Control of Emissions from Marine SI 

and Small SI Engines, Vessels, and 

Equipment 

Final Regulatory Impact Analysis 
Control of Emissions from Marine SI 

and Small SI Engines, Vessels, and 

Equipment 

Final Regulatory Impact Analysis 

Assessment and Standards Division 

Office of ransportation and Air Quality 

U.S. Environmental Protection Agency 

EPA420-R-08-014 

September 2008 
Table of Contents 

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ES-1 

CHAPTER 1: Industry Characterization 

1.1 Manufacturers of Small SI Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 

1.2 Manufacturers of Marine Spark-Ignition Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 

1.3 Fuel System Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6 

CHAPTER 2: Air Quality, Health, and Welfare Concerns 

2.1 Ozone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 

2.2 Particulate Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13 

2.3 Air Quality Modeling Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-32 

2.4 Air Toxics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-38 

2.5 Carbon Monoxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-43 

2.6 Acute Exposure to Air Pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-46 

CHAPTER 3: Emission Inventory 

3.1 Overview of Small Nonroad and Marine SI Engine Emissions Inventory 

Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 

3.2 Baseline Emission Inventory Estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 

3.3 Contribution of Small Nonroad and Marine SI Engines to National Emissions 

Inventories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-19 

3.4 Controlled Nonroad Small Spark-Ignition and Marine Engine Emission Inventory 

Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26 

3.5 Projected Emissions Reductions from the New Standards . . . . . . . . . . . . . . . . . . . . . 3-34 

3.6 Emission Inventories Used for Air Quality Modeling . . . . . . . . . . . . . . . . . . . . . . . . 3-43 

CHAPTER 4: Feasibility of Exhaust Emission Control 

4.1 General Description of Spark-Ignition Engine Technology . . . . . . . . . . . . . . . . . . . . . 4-1 

4.2 General Description of Exhaust Emission Control Technologies . . . . . . . . . . . . . . . . 4-8 

4.3 Feasibility of Small SI Engine Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22 

4.4 Feasibility of Outboard/Personal Watercraft Marine Engine Standards . . . . . . . . . . 4-38 

4.5 Feasibility of Sterndrive/Inboard Marine Engine Standards . . . . . . . . . . . . . . . . . . . 4-43 

4.6 Feasibility of Standard for Marine Generator Sets . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-55 

4.7 Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-56 

4.8 Impacts on Safety, Noise, and Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-72 

APPENDIX 4A: Normalized Modal Emissions for a 7.4 L MPI SD/I . . . . . . . . . . . . . . . 4-84 

CHAPTER 5: Feasibility of Evaporative Emission Control 

5.1 Diurnal Breathing Loss Evaporative Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2 

5.2 Running Loss Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26 

5.3 Fuel Tank Permeation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-29 

5.4 Fuel/Vapor Hose Permeation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-70 

5.5 Other Evaporative Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-89 

5.6 Evaporative Emission Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-91 

5.7 Impacts on Noise, Energy, and Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-109 
APPENDIX 5A: Diurnal Temperature Traces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-112 

APPENDIX 5B: Emission Results for Small SI Equipment Fuel Tanks Showing Effect of 

Venting on Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-115 

APPENDIX 5C: Diurnal Emission Results: Canister and Passive-Purge . . . . . . . . . . . 5-120 

APPENDIX 5D: Material Properties of Common Fuel System Materials . . . . . . . . . . . 5-121 

APPENDIX 5E: Diurnal Test Temperature Traces . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-125 

CHAPTER 6: Costs of Control 

6.1 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1 

6.2 Exhaust Emission Control Costs for Small SI Engines . . . . . . . . . . . . . . . . . . . . . . . . 6-2 

6.3 Exhaust Emission Control Costs for Outboard and Personal Watercraft Engines . . . 6-44 

6.4 Exhaust Emission Control Costs for Sterndrive/Inboard Marine Engines . . . . . . . . . 6-56 

6.5 Evaporative Emission Control Costs for Small SI Equipment . . . . . . . . . . . . . . . . . . 6-64 

6.6 Costs of Evaporative Emission Controls for Marine Vessels . . . . . . . . . . . . . . . . . . . 6-77 

6.7 Cost Sensitivity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-90

CHAPTER 7: Cost Per Ton 

7.1 30-Year Net Present Value Cost effectiveness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1 

7.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2 

CHAPTER 8: Cost-Benefit Analysis 

8.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1 

8.2 Air Quality Impacts for Benefits Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4 

8.3 PM-Related Health Benefits Estimation - Methods and Inputs . . . . . . . . . . . . . . . . . . 8-6 

8.4 Health Impact Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8 

8.5 Economic Values for Health Outcomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26 

8.6 Benefits Analysis Results for the Final Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-34 

8.7 Comparison of Costs and Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-44 

Appendix 8A: Sensitivity Analyses of Key Parameters in the Benefits Analysis . . . . . . . 8-51 

Appendix 8B: Health-Based Cost-Effectiveness of Reductions in Ambient O3 and PM2.5 

Associated with the Final Small SI and Recreational Marine Engine Rule . . . . . . . . 8-5 

CHAPTER 9: Economic Impact Analysis 

9.1 Overview and Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1 

9.2 Economic Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-16 

9.3 EIM Data Inputs and Model Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-35 

9.4 Methods for Describing Uncertainty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-64 

Appendix 9A: Impacts on Small SI Markets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-73 

Appendix 9B: Impacts on Marine SI Markets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-91 

Appendix 9C: Time Series of Social Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-103 

Appendix 9D: Overview of Model Equations and Calculation . . . . . . . . . . . . . . . . . . . . 9-107 

Appendix 9E: Elasticity Parameters for Economic Impact Modeling . . . . . . . . . . . . . . . 9-112 

Appendix 9F: Derivation of Supply Elasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-126 

Appendix 9G: Initial Market Equilibrium - Price Forecasts . . . . . . . . . . . . . . . . . . . . . . 9-128 

Appendix 9H: Sensitivity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-130 

CHAPTER 10: Small-Business Flexibility Analysis 

10.1 Overview of the Regulatory Flexibility Act . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1 
10.2 Need for and Objective of the Rulemaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2 

10.3 Summary of Significant Public Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3 

10.4 Definition and Description of Small Entities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4 

10.5 Type and Numbers of Small Entities Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5 

10.6 Reporting, Recordkeeping, and Compliance Requirements . . . . . . . . . . . . . . . . . . . 10-7 

10.7 Steps Taken to Minimize the Impact on Small Entities . . . . . . . . . . . . . . . . . . . . . . 10-8 

10.8 Projected Economic Effects of the Rulemaking . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1 

CHAPTER 11: Regulatory Alternatives 

11.1 Identification of Alternative Program Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1 

11.2 Cost per Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-7 

11.3 Emission Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-16 

11.4 Cost Effectiveness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-20 

11.5 Summary and Analysis of Alternative Program Options . . . . . . . . . . . . . . . . . . . . 11-20 

APPENDIX 11A: Emission Factors for the Less Stringent Alternative . . . . . . . . . . . . . 11-24 

APPENDIX 11B: Emission Factors for the More Stringent Alternative . . . . . . . . . . . . 11-27 

Executive Summary 

Executive Summary 

The Environmental Protection Agency (EPA) is establishing new requirements to reduce 

emissions of hydrocarbon (HC) and oxides of nitrogen (NOx) from nonroad small spark ignited 

engines below 19kW (“Small SI engines”) and marine spark ignited engines (“Marine SI 

engines”). This rule includes exhaust and evaporative emission standards for these engines as 

well as related gasoline fuel tanks and fuel lines. 

This executive summary describes the relevant air-quality issues, highlights the new exhaust 

and evaporative emission standards, and gives an overview of the analyses in the rest of this 

document. 

Air Quality Background and Environmental Impact of the Rule 

Emissions from Small SI engines and equipment and Marine SI engines and vessels 

contribute to a number of serious air pollution problems and will continue to do so in the future 

absent further reduction measures. Such emissions lead to adverse health and welfare effects 

associated with ozone, particulate matter (PM), nitrogen oxides (NOx), volatile organic 

compounds (VOC) including toxic compounds, and carbon monoxide (CO). These emissions 

also cause significant public welfare harm, such as damage to crops and regional haze. 

Millions of Americans continue to live in areas with unhealthy air quality that may endanger 

public health and welfare. As of March 2008 approximately 139 million people live in the 72 

areas that are designated as nonattainment for the 8-hour ozone National Ambient Air Quality 

Standards (NAAQS). In addition, approximately 88 million people live in areas that are 

designated as nonattainment for the PM2.5 NAAQS. Federal, state, and local governments are 

working to bring ozone and PM levels into attainment with the NAAQS. The reductions 

included in this rule will be useful to states in attaining and maintaining the ozone, CO, and PM 

NAAQS. 

In 2002, emissions from land-based nonroad Small SI engines and Marine SI 

engines were estimated to be about 26 percent of the total mobile-source inventory of VOC 

emissions and 1 percent of the NOx inventory. As presented in Figures 1 and 2, this rule will 

significantly reduce future Small SI and Marine SI emission inventories. 

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Final Regulatory Impact Analysis 

Figure 1: Small Spark Ignition VOC+NOx Baseline and Phase 3 Control Emission 

Inventory 

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

2000 2005 2010 2015 2020 2025 2030 2035 2040

Year

Tons

Baseline

Control

Figure 2: Marine Spark Ignition VOC+NOx Baseline and Phase 3 Control Emission 

Inventory 

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

2000 2005 2010 2015 2020 2025 2030 2035 2040

Year

Tons

Baseline

Control

ES-2 
Executive Summary 

Exhaust and Evaporative Emission Standards 

Tables 1 through 4 show the exhaust and evaporative emission standards and when they will 

apply. For Small SI nonhandheld engines, the standards are expected to result in the use of 

engine modificiations, aftertreatment systems, and some use of electronic fuel injection in Class 

II engines. As shown in Tables 1 through 4, we are phasing in many of the standards over time 

to address considerations of lead time, workload, and overall feasibility. In addition, the rule 

includes other provisions designed to address the transition to meeting the standards. 

Table 1: Small SI Nonhandheld Engine Exhaust Emission Standards and Schedule 

Engine Class Model Year 

HC+NOx 

[g/kW-hr] 

COa 

[g/kW-hr] 

Class I (>80cc to <225cc)b 2012 10.0 610 

Class II ($225cc) 2011 8.0 610 

a

 5 g/kW-hr CO for Small SI engines powering marine generators. b

 Nonhandheld engines at or below 80cc will be subject to the emission standards for handheld engines. 

Table 2: Small SI Equipment Evaporative Emission Standards and Schedule 

Fuel Line Permeation Tank Permeation Running Loss 

Standard Level 15 g/m2

/day 1.5 g/m2/day Design Standard 

Handheld 2012a,b 2009-2013c NA 

Class I 2009 2012 2012 

Class II 2009 2011 2011 

a

 2013 for small-volume families. b

 A separate set of declining fuel line permeation standards applies for cold-weather equipment from 2012 through 

2016. A standard of 225 g/m2

/day for cold-weather equipment fuel lines applies for 2016 and later. c

 2009 for families certified in California, 2013 for small-volume families, 2011 for structurally integrated nylon fuel 

tanks, and 2010 for remaining families. 

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Final Regulatory Impact Analysis 

Table 3a: Outboard/PWC Marine SI Engine Exhaust Standards and Schedulea 

Pollutant Powerb Emission Standardb Model Year 

HC+NOx 

P < 4.3 kW 30.0 2010 

P> 4.3 kW 2.1 + 0.09 × (151 + 557/P0.9) 2010 

CO 

P < 40 kW 500 – 5.0 × P 2010 

P> 40 kW 300 2010 

a

 These engines are also subject to not-to-exceed standards b

 P = maximum engine power in kilowatts (kW). 

Table 3b: Sterndrive/Inboard Marine SI Engine Exhaust Standards and Schedule 

Powera Model Year HC+NOx [g/kW-hr] CO [g/kW-hr] 

P < 373 kWb 2010c 5.0 75 

High-performance engines < 485 kW d 

2010 20.0 350 

2011 25.0 350 

High-performance engines < 485 kW d 

2010 16.0 350 

2011 22.0 350 

a

 P = maximum engine power in kilowatts (kW). b

 These engines are also subject to not-to-exceed standards. This category also includes engines >373 kW that do 

not otherwise meet the definition of “high-performance.” c

 2011 for small-businesses and for engines built using the 4.3L or 8.1L GM engine blocks. d

 For small businesses, the 2010 standards do not apply and the 2011 standards are delayed until 2013. 

Table 4: Marine SI Engine Evaporative Emissions Standards and Schedule 

Fuel Line Permeation Tank Permeation Diurnal 

Standard Level 15 g/m2

/day 1.5 g/m2/day 0.40 g/gal/day 

Portable Tanks 2009a 2011 2010b 

PWC 2009 2011 2010 

Other Installed Tanks 2009a 2012 2011c,d 

a

 2011 for primer bulbs. Phase-in for under cowl fuel lines, by length, on OB engines: 30% 2010, 60% 2011, 90% 

2012, 100% 2015. b

 Design standard. c

 Fuel tanks installed in nontrailerable boats (> 26 ft. in length or >8.5 ft. in width) may meet a standard of 0.16 

g/gal/day over an alternative test cycle. d

 The standard is effective July 31, 2011. For boats with installed fuel tanks, this standard is phased-in 50%/100% 

over the first two years. As an alternative, small manufacturers may participate in a diurnal allowance program. 

ES-4 
Executive Summary 

EPA has also taken steps to ensure that engines built to these standards achieve more 

accurate emissions reductions and is upgrading the test requirements to those listed in 

40CFR1065 as outlined in Preamble Section IX General Test Procedures. 

Feasibility of Meeting the Small SI Engine Exhaust Emission Standards 

Since 1997, exhaust emission control development for Small SI engines has concentrated on 

engine redesign including carburetor design, improved engine combustion and engine cooling. 

The primary technical focus of the new emission standards will be engine upgrades as needed, 

catalyst application to the majority of Small SI engines and electronic fuel injection on some 

Class II engines. Related information is in Chapter 4. 

We are finalizing, more stringent exhaust HC+NOx standards for Class I and II Small SI 

engines. We are also establishing a new CO standard for Small SI engines used in marine 

generator applications. The standards differ by engine size. Class I engines have a total engine 

displacement of < 225cc. Class II engines have a total engine displacement of $225cc. 

In the 2008 model year, manufacturers certified nearly 235 Class I and II engine families to 

the Phase 2 standards using a variety of engine designs and emission control technology. All 

Class I engines were produced using carbureted air-fuel induction systems and are air cooled. 

An extremely small number of engines used catalyst-based emission control technology. 

Similarly, Class II engines were predominantly carbureted and air cooled. A limited number of 

these engines used catalyst technology, electronic engine controls and fuel injection, and/or 

water 

cooling. 

The market focus has a large part to play in the engine design and quality. The large number 

of residential and commercial applications have led to a wide variety of engine qualities and 

designs in the marketplace today. Some of the more durable engine designs already incorporate 

the base design requirements needed to incorporate a catalyst to meet the Phase 3 emission 

standards. In addition, a number of engine families in both classes are currently certified at 

levels that would comply with the Phase 3 standards. 

Based on our own testing of advanced technology for these engines, our engineering 

assessments, and statements from the affected industry, we believe the requirements will lead 

many engine manufacturers to adopt exhaust aftertreatment technology using catalyst-based 

systems. Other likely engine changes include improvements in engine designs, cooling system 

designs and fuel delivery systems. The addition of electronic controls and/or fuel injection 

systems to some Class II engine families may obviate the need for catalytic aftertreatment, with 

the most likely candidates being multi-cylinder engine designs. 

Information herein on the feasibility assessment of exhaust emissions on Small SI engines 

includes the emission evaluation of current product and advanced technology engines. Areas 

covered include laboratory and field evaluations, review of patents of existing catalyst/muffler 

ES-5 
Final Regulatory Impact Analysis 

designs for Class I engines, discussions with engine manufacturers and suppliers of emission 

control-related engine components regarding recent and expected advances in emissions 

performance, and an analysis of catalyst/muffler units that were already in mass production by an 

original equipment manufacturer for use on European walk-behind lawn mowers. 

EPA used this information to design, build and emission test prototype catalyst-based 

emission control systems that were capable of effectively and safely achieving the Phase 3 

emission standards on both Class I and Class II engines. Chapter 4 projects that in some cases 

manufacturers of Class I and Class II engines may need to improve the durability of their basic 

engine designs, cooling system designs, ignition systems, or fuel metering systems for some 

engines in order to comply with the Phase 3 emission regulations over the useful life. EPA also 

built and tested electronic fuel injection systems on two twin cylinder Class II engines and 

emission tested them with and without catalysts. EFI improves the management of air-fuel 

mixtures and ignition spark timing and each of the engines achieved the requisite emission limit 

for HC+NOx (e.g., 8.0 g/kW-hr). Based on this work and information from one manufacturer of 

emission controls, we believe that either a catalyst-based system or electronic engine controls 

appear sufficient to meet the standard. Manufacturers adopting the EFI approach will likely 

realize other advantages such as easier starting, more stable and reliable engine operation, and 

reduced fuel consumption. 

We also used the information and the results of our engine testing to assess the potential need 

for improvements to engine, cooling and fuel system designs. A great deal of this effort was 

conducted in association with our more in-depth study regarding the efficacy and safety of 

implementing advanced exhaust emission controls on Small SI and recreational Marine SI 

engines, as well as new evaporative requirements for these engines, equipment, and vessels. The 

results of that study are also discussed in Chapter 4. 

There are a number of Class II engines that use gaseous fuels (i.e., liquid propane gas or 

compressed natural gas). Based on our engineering evaluation of current and likely emission 

control technology for these engines, we conclude that these engines will use catalysts, or larger 

catalysts than current, in order to achieve the Phase 3 HC+NOx standard. Some engines 

currently meet the Phase 3 emission standards. 

Regarding the marine generator CO standard, two manufacturers that produce the majority of 

marine generators have announced that as a result of boat builder demand, they are converting 

their marine generator product lines to new designs which can achieve more than a 99 percent 

reduction in CO emissions in order to reduce the risk of CO poisoning. These low CO emission 

designs used closed-loop electronic fuel injection and catalytic control on engines which are 

water cooled using the lake or sea water. Both of these manufacturers have certified some low 

CO engines and have expressed their intent to convert their full product lines in the near future. 

These manufacturers also make use of electronic controls to monitor catalyst function. 

Feasibility of Meeting the Marine SI Exhaust Emission Standards 

The technology is available for marine engine manufacturers to use to meet the new 

ES-6 
Executive Summary 

standards. This technology is the same that manufacturers are anticipated to use to meet the 

California ARB standards in 2008. For outboards and personal watercraft (OB/PWC) this 

largely means extended use of lower-emitting engine technology widely used today. For 

sterndrive and inboard (SD/I) marine engines, this means the use of catalytic converters in the 

exhaust system. Chapter 4 includes detailed descriptions of low emission technologies for 

marine engines, including emissions test data on these technologies. 

OB/PWC 

Over the past several years, manufacturers have demonstrated their ability to achieve 

significant HC+NOx emission reductions from OB/PWC engines. This has largely been 

accomplished through the introduction of two-stroke direct injection engines in some 

applications and conversion to four-stroke engines. Current certification data for these types of 

engines show that these technologies may be used to achieve emission levels significantly below 

the existing exhaust emission standards. In fact, California has adopted standards requiring a 65 

percent reduction beyond the current federal standards beginning in 2008. 

Our own analysis of recent certification data shows that most four-stroke outboard engines 

and many two-stroke direct injection outboard engines currently meet the new HC+NOx 

standard. Similarly, although PWC engines tend to have higher HC+NOx emissions, 

presumably due to their higher power densities, many of these engines also meet the new 

HC+NOx standard. Although there is currently not a CO emission standard for OB/PWC 

engines, OB/PWC manufacturers are required to report CO emissions from their engines. These 

emissions are based on test data from new engines and do not consider deterioration or 

compliance margins. Based on this data, all of the two-stroke direct injection engines show 

emissions well below the new standards. In addition, the majority of four-stroke engines meet 

the CO standards as well. 

We therefore believe the HC+NOx and CO emission standards can be achieved by phasing 

out conventional carbureted two-stroke engines and replacing them with four-stroke engines or 

two-stroke direct injection engines. This has been the market-driven trend over the last five 

years. Chapter 4 compares recent certification data to the new standards. 

SD/I 

Engine manufacturers can adapt readily available technologies to control emissions from 

SD/I engines. Electronically controlled fuel injection gives manufacturers more precise control 

of the air/fuel ratio in each cylinder, thereby giving them greater flexibility in how they calibrate 

their engines. With the addition of an oxygen sensor, electronic controls give manufacturers the 

ability to use closed-loop control, which is especially valuable when using a catalyst. In 

addition, manufacturers can achieve HC+NOx reductions through the use of exhaust gas 

recirculation. However, the most effective technology for controlling emissions is a three-way 

catalyst in the exhaust stream. 

In SD/I engines, the exhaust manifolds are water-jacketed and the water mixes with the 

ES-7 
Final Regulatory Impact Analysis 

exhaust stream before exiting the vessel. Manufacturers add a water jacket to the exhaust 

manifold to meet temperature-safety protocol. They route this cooling water into the exhaust to 

protect the exhaust couplings and to reduce engine noise. Catalysts must therefore be placed 

upstream of the point where the exhaust and water mix-this ensures the effectiveness and 

durability of the catalyst. Because the catalyst must be small enough to fit in the exhaust 

manifold, potential emission reductions are not likely to exceed 90 percent, as is common in 

land-based applications. However, as discussed in Chapter 4 of the Final RIA, data on 

catalyst-equipped SD/I engines show that emissions may be reduced by 70 to 80 percent for 

HC+NOx and 30 to 50 percent for CO over the test cycle. Larger reductions, especially for CO, 

have been achieved at lower-speed operation. 

Chapter 4 discusses issues that have been addressed in catalyst designs for SD/I engines such 

as sustained operation at high load, potential saltwater effects on catalyst efficiency, and thermal 

shock from cold water contacting a hot catalyst. Test programs have been performed to evaluate 

catalysts in the laboratory and on the water. Three SD/I engine manufacturers have certified SD/I 

engines to the California ARB standards, and some catalyst-equipped engines are available for 

purchase nationwide. Manufacturers have indicated that they have successfully completed 

durability testing, including extended in-use testing on saltwater. 

Feasibility of Meeting the Evaporative Emission Standards 

There are many feasible control technologies that manufacturers can use to meet the 

evaporative emission standards. We have collected emission test data on a wide range of 

technologies for controlling evaporative emissions. Chapter 5 presents a description of the 

evaporative emission sources which include permeation, diurnal, running loss, hot soak, and 

refueling emissions. In addition, Chapter 5 presents evaporative emission test data for current 

Small SI and marine fuel systems and on a wide range of evaporative emission control 

technologies. Below is an overview of technologies that are available for meeting the 

evaporative emission standards. 

Low-permeation fuel lines are in production today. One fuel line design, already used in 

some marine applications, uses a thermoplastic layer between two rubber layers to control 

permeation. This thermoplastic barrier may either be nylon or ethyl vinyl acetate (EVOH). 

Barrier approaches in automotive applications include fuel lines with fluoroelastomers such as 

FKM and fluoroplastics such as Teflon and THV. In addition to presenting data on 

low-permeation fuel lines, Chapter 5 lists several fuel-system materials and their permeation 

rates. Molded rubber fuel line components, such as primer bulbs and some handheld fuel lines, 

could meet the standard by using a fluoroelastomer such as FKM. 

Plastic fuel tanks used in Small SI and Marine SI applications can be molded using several 

processes. While no fuel tank permeation control strategy will work for all production processes 

and materials, there are multiple control strategies available for fuel tanks manufactured with 

each of the molding processes. These molding processes include blow-molding, injectionmolding, thermoforming, rotational-molding, and hand built constructions (fiberglass). 

ES-8 
Executive Summary 

Multi-layer fuel tanks can be formed using most of these molding processes. These fuel tank 

constructions include a barrier layer of a low permeation material such as ethylene vinyl alcohol 

(EVOH) or nylon. This technology has been used in blow-molded fuel tanks for automotive 

applications for many years and can achieve emission levels well below the new standard. For 

thermoformed fuel tanks, a similar barrier formed into the plastic sheet that is later molded into a 

fuel tank. Rotationally-molded fuel tanks can be produced with an inner barrier layer such as 

nylon. As an alternative, in the blow-molding process, a low-permeable resin can be blended 

with polyethylene and extruded it with a single screw. Although the barrier is not continuous, 

this strategy can still be used to meet the permeation standard. A similar strategy may be used 

for fiberglass fuel tank where the barrier material is clay nanocomposites. Finally, fuel tanks 

may be formed entirely out of a low permeation material such as nylon or an acetal copolymer. 

Many fuel tanks used with handheld equipment use nylon fuel tanks. 

Another approach to producing fuel tanks that meet the permeation standards would be to 

create permeation barrier through a post-processing step. Regardless of the molding process, 

another type of low-permeation technology for high-density polyethylene fuel tanks would be to 

treat the surfaces with a barrier layer. Two ways of achieving this are known as fluorination and 

sulfonation. In these processes, the tanks are exposed to a gas which forms a permeation barrier 

on the surfaces of the fuel tank. Either of these processes can be used to reduce gasoline 

permeation by more than 95 percent. Additionally, a barrier layer can be put onto a fuel tank 

with the use of an epoxy barrier coating. 

There are several technologies that can be used to reduce diurnal emissions from marine fuel 

tanks. The simplest approach is to seal the fuel tank. Portable fuel tanks currently use manual 

valves that can be closed to seal the fuel tank. PWC typically use sealed fuel systems with 

pressure relief valves that open at pressures ranging from 0.5 to 4.0 psi. For other vessels with 

installed fuel tanks, manufacturers have commented that even 1.0 psi of pressure would be too 

high for their applications. Through the use of a carbon canister in the vent line, diurnal 

emissions can be controlled from these fuel tanks without creating significant pressure in the fuel 

tank. With this technology, vapor generated in the tank is vented to a canister containing 

activated carbon. The fuel tank must be sealed such that the only venting that occurs is through 

the carbon canister. The activated carbon collects and stores the hydrocarbons. The activated 

carbon bed in the canister is refreshed by purging the vapors with air flow. The standard is 

based on the air flow being generated by the natural breathing of the fuel tank as it heats and 

cools. 

Running loss emissions can be controlled from Small SI equipment by sealing the fuel cap 

and routing vapors from the fuel tank to the engine intake. In doing so, vapors generated by heat 

from the engine will be burned in the engine’s combustion chamber. It may be necessary to use 

a valve or limited-flow orifice in the purge line to prevent too much fuel vapor from reaching the 

engine and to prevent liquid fuel from entering the line if the equipment flips over. Depending 

on the configuration of the fuel system and purge line, a one-way valve in the fuel cap may be 

desired to prevent a vacuum in the fuel tank during engine operation. We anticipate that a 

system like this would eliminate running loss emissions. However, higher temperatures during 

operation and the additional length of vapor line would slightly increase permeation. 

ES-9 
Final Regulatory Impact Analysis 

Considering these effects, we still believe that the system described here would reduce running 

losses from Small SI equipment by more than 90 percent. 

Many manufacturers today use fuel caps that by their design effectively limit the diffusion of 

gasoline from fuel tanks. In any case, we expect that the new running loss design standard will 

limit any diffusion emissions from this equipment. As discussed in Chapter 5, venting a fuel 

tank through a tube (rather than through an open orifice) greatly reduces diffusion. 

Estimated Costs and Cost-Effectiveness for Small SI Engines and Equipment 

There are approximately 410 nonroad equipment manufacturers using Small SI engines in 

over a thousand different equipment models. There are more than 50 engine manufacturers 

certifying Small SI engine families for these applications. Fixed costs consider engine research 

and development, engine tooling, engine certification, and equipment redesign. Variable costs 

include estimates for new emission-control hardware. Near-term and long-term costs for some 

example pieces of equipment are shown in Table 5. Also shown in Table 5 are typical prices for 

each piece of equipment for reference. See Chapter 6 for detailed information related to our 

engine and equipment cost analysis. 

Table 5: Estimated Costs for Several Example Pieces of Equipment ($2005)a 

Over the Range of Useful Life Categories for Small SI Enginesb 

Class I Class II Handheld 

(Class III-V) 

Exhaust Near Term 

Long Term 

$10 to $26 

$10 to $12 

$17 to $60 

$12 to $30 

$0.28 

$0.00 

Evaporative Near Term 

Long Term 

$3.05 

$2.20 

$6.73 

$5.16 

$0.82 

$0.69 

Total (without fuel savings) 

Near Term 

Long Term 

$14 to $26 

$11 to $17 

$46 to $92 

$27 to $52 

$1.12 

$0.69 

Total (with fuel savings)c 

Near Term 

Long Term 

$13 to $25 

$10 to $16 

$1-$48/$40-$86 

-$18-$6/$21-$46 

Engines w/ and w/o EFI 

$0.72 

$0.29 

Estimated Equipment Price Range $100-$2,800 $300-$6800 $210 avg 

a

 Near-term costs include both variable costs and fixed costs; long-term costs include only variable costs

 and represent those costs that remain following recovery of all fixed costs. 

b

 Class I (125,250, or 500 hours), Class II (250, 500, or 1000 hours) 

c

 Class I, Class II and handheld have fuel savings from evaporative measures. Class II engines with EFI have fuel 

savings of $39 based on the lifetime savings in the use of a residential ride on mower. There are no fuel savings 

related to compliance with the exhaust emission standard for Class I, handheld, or Class II engines without EFI. 

Chapter 6 presents aggregate costs of compliance for the new exhaust and evaporative 

ES-10 
Executive Summary 

emission standards for Small SI engines. Table 6 presents the annualized aggregate costs and 

fuel savings for the period from 2008-2037. The annualized fuel savings for Small SI engines 

are due to reduced fuel costs form the sue of electronic fuel injection on Class II engines as well 

as fuel savings from evaporative measures on all Small SI engines. 

Table 6: Estimated Annualized Cost to manufacturers and Annualized Fuel Savings for 

Small SI Engines and Equipment at a 7% Discount Rate (2005$) 

Annualized Cost to Manufacturers 

(millions/yr) 

Annualized fuel savings 

(millions/yr) 

Exhaust $182 $24 

Evaporative $65 $53 

Aggregate $247 $77 

Chapter 7 describes the cost effectiveness analysis. In this analysis, the aggregate costs of 

compliance are determined for the period 2008-2037. The discounted aggregate costs for the 

period are divided by the discounted aggregate HC_NOx emission reductions. 

Table 7: Aggregate Cost per Ton for Small SI Engines and Equipment 

2008-2037 Net Present Values at 7% Discount Rate ($2005) 

Pollutant 

NOx+HC 

Aggregate Discounted 

Lifetime Cost per ton 

Without Fuel Savings 

Aggregate Discounted 

Lifetime Cost per ton 

With Fuel Savings 

7% $978 $650 

Estimated Costs and Cost-Effectiveness for Marine SI Engines

 According to the US Coast Guard there are well over a thousand different boat builders 

using Marine SI engines. There are about 10 engine manufacturers certifying to the current 

OB/PWC exhaust emission standards. We have identified more than 30 companies 

manufacturing SD/I marine engines. Fixed costs consider engine research and development, 

engine tooling, engine certification, and equipment redesign. Variable costs include estimates 

for new emission-control hardware. Near-term and long-term costs for three different Marine SI 

applications are shown in Table 8. Also shown in Table 8 are typical prices for these types of 

marine vessels. See Chapter 6 for detailed information related to our engine and equipment cost 

analysis. 

ES-11 
Final Regulatory Impact Analysis 

Table 8: Estimated Average Incremental Costs for SI Marine Engines and Vessels ($2005)a 

Engine Category 

(Fuel Storage System) 

Outboard 

(Portable) 

PWC SD/I 

(Installed) 

Exhaust 

Near Term 

Long Term 

$291 

$224 

$359 

$272 

$355 

$266 

Evaporative 

Near Term 

Long Term 

$12 

$8 

$17 

$11 

$74 

$62 

Total (without fuel savings)b 

Near Term 

Long Term 

$433 

$336 

$376 

$283 

$487 

$376 

Total (with fuel savings)b 

Near Term 

Long Term 

$245 

$148 

$165 

$72 

$348 

$237 

Estimated Vessel Price Range $10,000-50,000 $6,000-12,000 $20,000-200,000 

a

 Near-term costs include both variable costs and fixed costs; long-term costs include only variable costs and 

represent those costs that remain following recovery of all fixed costs. 

b Total costs are presented as an average per boat and consider that many boats have multiple engines. 

Chapter 6 presents aggregate costs of compliance for the new exhaust and evaporative 

emission standards for Marine SI engines. Table 9 presents the annualized aggregate costs and 

fuel savings for the period from 2008-2037. The annualized fuel savings for Marine SI engines 

are due to reduced fuel costs from the use of more fuel efficient engines as well as fuel savings 

from evaporative measures. 

Table 9: Estimated Annualized Cost to Manufacturers and Annualized Fuel Savings for 

Marine SI Engines and Vessels at a 7% Discount Rate (2005$) 

Annualized Cost to Manufacturers 

(millions/yr) 

Annualized Fuel Savings 

(millions/year) 

Exhaust $123 $56 

Evaporative $22 $22 

Aggregate $144 $78 

Chapter 7 describes the cost effectiveness analysis. In this analysis, the aggregate costs of 

compliance are determined for the period 2008-2037. The discounted aggregate costs for the 

period are divided by the discounted aggregate HC+NOx emission reductions over that same 

period. Table 10 presents the cost per ton estimates with and without fuel savings. 

ES-12 
Executive Summary 

Table 10: Aggregate Cost per Ton for SI Marine Engines and Vessels 

2008-2037 Net Present Values at 7% Discount Rate ($2005) 

Pollutant Aggregate Discounted Aggregate Discounted 

NOx+HC Lifetime Cost per ton Lifetime Cost per ton 

Without Fuel Savings With Fuel Savings 

7% $780 $360 

Economic Impact Analysis 

We prepared a final Economic Impact Analysis estimate the market and social welfare 

impacts of the new standards. This analysis can be found in Chapter 9. According to this 

analysis, the average price of a Marine SI engine in 2030 is projected to increase by less than 2 

percent ($213) as a result of the new standards, and the average price of a Marine SI vessel is 

projected to increase by between 0.7 percent and 2.4 percent ($218 to $702), depending on the 

type of vessel. The average price of a Small SI engine in 2030 is projected to increase by about 

7.4 percent ($12), and the average price of Small SI nonhandheld equipment is projected to 

increase by between 2.2 percent and 5.6 percent ($15 to $20), depending on equipment class. 

Changes in quantity produced are expected to be small, at less than 2 percent. The exceptions 

are PWC (4.8 percent) and Class II equipment (2.4 percent). 

The net social costs of the program in 2030 are estimated to be $186 million. This includes 

$459 million of direct social costs and $273 million on fuel savings for the end users of these 

products. Overall, the consumers of Marine SI vessels and Small SI equipment are expected to 

bear the majority of the costs of complying with the program: 76 percent of the Marine SI 

program social costs in 2030, and 91 percent of the Small SI program social costs. However, 

when the fuel savings are considered, the social costs burden for consumers of Marine SI 

equipment becomes a net benefit (the fuel savings are greater than the compliance costs of the 

program), while the end-user share of the Small SI program drops to 86 percent. 

Benefits 

We estimate that the requirements in this rulemaking will result in substantial benefits to 

public health and welfare and the environment, as described in Chapter 8. The benefits analysis 

performed for this rulemaking uses sophisticated air quality and benefit modeling tools and is 

based on peer-reviewed studies of air quality and health and welfare effects associated with 

improvements in air quality and peer-reviewed studies of the dollar values of those public health 

and welfare effects. 

The range of benefits associated with this program are estimated based on the risk of several 

sources of PM- and ozone-related mortality effect estimates, along with all other PM and ozone 

non-mortality related benefits information. These benefits are presented in Table 11. The 

benefits reflect two different sources of information about the impact of reductions in PM on 

ES-13 
Final Regulatory Impact Analysis 

reduction in the risk of premature death, including an estimate of mortality derived from the 

epidemiological literature (the American Cancer Society (ACS) cohort study - Pope et al., 2002) 

and an expert elicitation study conducted by EPA in 2006. In order to provide an indication of 

the sensitivity of the benefits estimates to alternative assumptions, in Chapter 8 of the RIA we 

present a variety of benefits estimates based on two epidemiological studies (including the ACS 

Study and the Six Cities Study) and the expert elicitation. EPA intends to ask the Science 

Advisory Board to provide additional advice as to which scientific studies should be used in 

future RIAs to estimate the benefits of reductions in PM. 

The range of ozone benefits associated with the final standards is also estimated based on 

risk reductions estimated using several sources of ozone-related mortality effect estimates. 

There is considerable uncertainty in the magnitude of the association between ozone and 

premature mortality. This analysis presents four alternative estimates for the association based 

upon different functions reported in the scientific literature. We use the National Morbidity, 

Mortality and Air Pollution Study (NMMAPS), which was used as the primary basis for the risk 

analysis in the ozone Staff Paper and reviewed by the Clean Air Science Advisory Committee 

(CASAC). We also use three studies that synthesize ozone mortality data across a large number 

of individual studies. Note that there are uncertainties within each study that are not fully 

captured by this range of estimates. Chapter 8 of the RIA presents the results of each of the 

ozone mortality studies separately. 

In a recent report on the estimation of ozone-related premature mortality published by the 

National Research Council (NRC), a panel of experts and reviewers concluded that 

ozone-related mortality should be included in estimates of the health benefits of reducing ozone 

exposure. The report also recommended that the estimation of ozone-related premature mortality 

be accompanied by broad uncertainty analyses while giving little or no weight to the assumption 

that there is no causal association between ozone exposure and premature mortality. Because 

EPA has yet to develop a coordinated response to the NRC report's findings and 

recommendations, however, we have retained the approach to estimating ozone-related 

premature mortality used in RIA for the final Ozone NAAQS. EPA will specifically address the 

report's findings and recommendations in future rulemakings. 

The range of total ozone- and PM-related benefits associated with the final standards is 

presented in Table 11. We present total benefits based on the PM- and ozone-related premature 

mortality function used. The benefits ranges therefore reflect the addition of each estimate of 

ozone-related premature mortality (each with its own row in Table 11) to estimates of 

PM-related premature mortality, derived from either the epidemiological literature or the expert 

elicitation. 

ES-14 
Executive Summary 

Table 11: Estimated Monetized PM- and Ozone-Related Health Benefits of the Small SI 

and Marine SI Engine Standards 

2030 Total Ozone and PM Benefits - PM Mortality Derived from Epidemiology Studiesa 

Premature Ozone Mortality 

Function or Assumption 

Reference Mean Total Benefits 

(Billions, 2005$, 3% discount 

rate)c,d 

NMMAPS Bell et al., 2004 $2.4 

Meta-analysis Bell et al., 2005 $3.7 

Ito et al., 2005 $4.4 

Levy et al., 2005 $4.4 

Assumption that association is not causale $1.8 

2030 Total Ozone and PM Benefits - PM Mortality Derived from Expert Elicitationb 

Premature Ozone Mortality 

Function or Assumption 

Reference Mean Total Benefits 

(Billions, 2005$, 3% discount 

rate)c,d 

NMMAPS Bell et al., 2004 $1.7 to $9.7 

Meta-analysis Bell et al., 2005 $3.0 to $11 

Ito et al., 2005 $3.7 to $12 

Levy et al., 2005 $3.7 to $12 

Assumption that association is not causale $1.1 to $9.1 

a

 Total includes ozone and PM2.5 benefits. Range was developed by adding the estimate from the ozone premature 

mortality function to an estimate of PM2.5-related premature mortality derived from the ACS (Pope et al., 2002) 

study. 

b

 Total includes ozone and PM2.5 benefits. Range was developed by adding the estimate from the ozone premature 

mortality function to both the lower and upper ends of the range of the PM2.5 premature mortality functions 

characterized in the expert elicitation. The effect estimates of five of the twelve experts included in the elicitation 

panel fall within the empirically-derived range provided by the ACS and Six-Cities studies. One of the experts fall 

below this range and six of the experts are above this range. Although the overall range across experts is 

summarized in this table, the full uncertainty in the estimates is reflected by the results for the full set of 12 experts. 

The twelve experts' judgments as to the likely mean effect estimate are not evenly distributed across the range 

illustrated by arraying the highest and lowest expert means. 

c

 Note that total benefits presented here do not include a number of unquantified benefits categories. A detailed 

listing of unquantified health and welfare effects is provided in Table 8.4-1. d

 Results reflect the use of a 3 percent discount rate. Monetary results presented in Table 8.6-2 use both a 3 and 7 

percent discount rate, as recommended by EPA's Guidelines for Preparing Economic Analyses and OMB Circular 

A-4. Results are rounded to two significant digits for ease of presentation and computation. e

A recent report published by the National Research Council (NRC, 2008) recommended that EPA "give little or no 

weight to the assumption that there is no causal association between estimated reductions in premature mortality and 

reduced ozone exposure." 

ES-15 
Final Regulatory Impact Analysis 

We estimate that by 2030, the annual emission reductions associated with these more 

stringent standards will annually prevent 230 PM-related premature deaths (based on the ACS 

cohort study), between 77 and 350 ozone-related premature deaths (assuming a causal 

relationship between ozone and mortality), 1,700 hospital admissions and emergency room 

visits, 23,000 work days lost, and approximately 590,000 minor restricted-activity days. 

Impact on Small Businesses 

Chapter 10 discusses our Small Business Flexibility Analysis, which evaluates the impacts of 

the emission standards on small entities. As a part of this analysis, we interacted with several 

small entities representing the various affected sectors and convened a Small Business Advocacy 

Review (SBAR) Panel to gain feedback and advice from these representatives. The small 

entities that participated in the process included engine manufacturers, equipment manufacturers, 

vessel manufacturers, fuel tank manufacturers, and fuel hose manufacturers. The feedback from 

these companies was used to develop regulatory options which could address the impacts of the 

rule on small businesses. Small entities raised general concerns related to potential difficulties 

and costs of meeting the new standards. 

The SBAR Panel consisted of representatives from EPA, the Office of Management and 

Budget, and the Small Business Administration. The Panel developed a wide range of regulatory 

flexibilities to mitigate the impacts of the standards on small entities, and recommended that we 

propose and seek comment on the flexibilities. Chapter 10 discusses the flexibilities 

recommended by the Panel, and the flexibilities we are finalizing with today’s rule. We are 

establishing several provisions that give affected small entities several compliance options aimed 

specifically at reducing their compliance burdens. In general the options are similar to small 

entity provisions adopted in prior rulemakings where EPA set standards for other types of 

nonroad engines. The provisions include extra lead time for complying with the new standards, 

reduced testing requirements for demonstrating compliance with the new standards, and hardship 

provisions to address significant economic impacts and unusual circumstances related to the new 

standards. These provisions are intended to reduce the burden on small entities that will be 

required to meet the new emission standards when they are implemented. Given all of the 

flexibilities being adopted for small entities, we believe that this action will not have a 

significant economic impact on a substantial number of small entities. 

Alternative Program Options 

In developing the emission standards, we considered several alternatives including less 

and/or more stringent options. The paragraphs below summarize the information considered in 

Chapter 11 of the Draft RIA. 

Small SI Engines 

For Small SI engines, we considered what was achievable with catalyst technology. Our 

technology assessment work indicated that the emission standards are feasible in the context of 

ES-16 
Executive Summary 

provisions for establishing emission standards prescribed in section 213 of the Clean Air Act. 

We also considered what could be achieved with larger, more efficient catalysts and improved 

fuel induction systems. In particular, Chapter 4 of the Draft RIA presents data on Class I 

engines with more active catalysts and on Class II engines with closed-loop control fuel injection 

systems in addition to a catalyst. In both cases larger emission reductions were achieved. 

Based on this work we considered HC+NOx standards which would have involved a 50 

percent reduction for Class I engines and a 65-70 percent reduction for Class II engines. Chapter 

11 of the Draft RIA evaluates these alternatives, including an assessment of the overall 

technology and costs of meeting more stringent standards. For Class I engines a 50 percent 

reduction standard would require base engine changes not necessarily involved with the new 

standards and the use of a more active catalyst. For Class II engines this would require the 

widespread use of closed loop control fuel injection systems rather than carburetors, some 

additional engine upgrades, and the use three-way catalysts. We believe it is not appropriate at 

this time to establish more stringent exhaust emission standards for Small SI engines. Our key 

concern is lead time. More stringent standards would require several years (3-5) more lead time 

beyond the 2011 model year start date. We believe it would be more effective to implement the 

Phase 3 standards we are finalizing today to achieve near-term emission reductions needed to 

reduce ozone precursor emissions and to minimize growth in the Small SI exhaust emissions 

inventory in the post 2010 time frame. More efficient catalysts, engine improvements, and 

closed loop electronic fuel injection could be the basis for more stringent emission standards at 

some point in the future. 

Marine SI Engines 

In developing the final emission standards for SD/I engines, we considered both what was 

achievable without catalysts and what could be achieved with larger, more efficient catalysts 

than those used in our test programs. Without catalysts, we believe exhaust gas recirculation is a 

technologically feasible and cost-effective approach to reducing emissions from SD/I marine 

engines. However, we believe greater reductions could be achieved through the use of catalysts. 

We considered basing an interim standard on EGR, but were concerned that this will divert 

manufacturers' resources away from catalyst development and could have the effect of delaying 

emission reductions from this sector. 

Several of the marine engines with catalysts that were tested as part of the development of 

the standards had HC+NOx emission rates appreciably lower than 5 g/kW-hr, even with 

consideration of expected in-use emissions deterioration associated with catalyst aging. We 

considered a 2.5 g/kW-hr HC+NOx standard in our analysis of alternatives. However, we 

believe a standard of 5 g/kW-hr is still appropriate given the potential variability of in-use 

performance and in test data. 

For OB/PWC engines, we considered a level of 10 g/kW-hr HC+NOx for OB/PWC engines 

greater than 40 kW with an equivalent percent reduction below the new standards for engines 

less than 40 kW. This second tier of standards could apply in the 2012 or later time frame. Such 

a standard would be consistent with currently certified emission levels from a significant number 

ES-17 
Final Regulatory Impact Analysis 

of four-stroke outboard engines. We have three concerns with adopting this second tier of 

OB/PWC standards. First, while some four-stroke engines may be able to meet a 10 g/kW-hr 

standard with improved calibrations, it is not clear that all engines could meet this standard 

without applying catalyst technology. As described in Section IV.H.3 of the preamble, we 

believe it is not appropriate to base standards in this rule on the use of catalysts for OB/PWC 

engines. The technology is yet to be adequately demonstrated. Second, certification data for 

personal watercraft engines show somewhat higher exhaust emission levels, so setting the 

standard at 10 g/kW-hr would likely require catalysts for many models. Third, two-stroke direct 

injection engines operate with lean air-fuel ratios, so reducing NOx emissions with any kind of 

aftertreatment is challenging. 

Therefore, unlike the standards for SD/I engines, we are not pursuing OB/PWC standards 

that will require the use of catalysts. Catalyst technology would be necessary for significant 

additional control of HC+NOx and CO emissions. While there is good potential for eventual 

application of catalyst technology to OB/PWC engines, we believe the technology is not 

adequately demonstrated at this point. 

Evaporative Emission Controls 

We considered both less and more stringent evaporative emission control alternatives for fuel 

systems used in Small SI equipment and Marine SI vessels. Chapter 11 of the Draft RIA 

presents details on this analysis of regulatory alternatives. The results of this analysis are 

summarized below. We believe that the permeation standards are reflective of available 

technology and represent a step change in emissions performance. Therefore, we consider the 

same permeation control scenario in the less stringent and more stringent regulatory alternatives. 

For Small SI equipment, we considered a less stringent alternative without running loss 

emission standards for Small SI engines. However, we believe that controlling running loss 

emissions from non-handheld equipment is feasible at a relatively low cost. Running loss 

emissions can be controlled by changing the fuel tank and cap venting scheme and routing 

vapors from the fuel tank to the engine intake. Not requiring these controls would be 

inconsistent with section 213 of the Clean Air Act. For a more stringent alternative, we 

considered applying a diurnal emission standard for all Small SI equipment. We believe that 

passively purging carbon canisters could reduce diurnal emissions by 50 to 60 percent from 

Small SI equipment. However, we believe there would be significant costs to add carbon 

canisters to all Small SI equipment nationwide, especially when taking packaging and vibration 

into account. The cost sensitivity is especially noteworthy given the relatively low emissions 

levels (on a per-equipment basis) from such small fuel tanks. 

For Marine SI vessels, we considered a less stringent alternative, where there would be no 

diurnal emission standard for vessels with installed fuel tanks. However, installed fuel tanks on 

marine vessels are much larger in capacity than those used in Small SI applications. Our 

analysis indicates that traditional carbon canisters are feasible for boats at relatively low cost. 

While packaging and vibration are also issues with marine applications, we believe these issues 

have been addressed. Carbon canisters were installed on fourteen boats by industry in a pilot 

ES-18 
Executive Summary 

program. The results demonstrated the feasibility of this technology. The standards would be 

achievable through engineering design-based certification with canisters that are very much 

smaller than the fuel tanks. In addition, sealed systems, with pressure control strategies would 

be accepted under the engineering design-based certification. For a more stringent scenario, we 

consider a standard that would require boat builders to use an actively purged carbon canister. 

This means that, when the engine is operating, it would draw air through the canister to purge the 

canister of stored hydrocarbons. However, we rejected this option because active purge occurs 

infrequently due to the low hours of operation per year seen by many boats. The gain in overall 

efficiency would be quite small relative to the complexity active purge adds into the system in 

that the engine must be integrated into a vessel-based control strategy. The additional benefit of 

an actively purged diurnal control system is small in comparison to the cost and complexity of 

such a system. 

Conclusion 

We believe the new emission standards reflect what manufacturers can achieve through the 

application of available technology. We believe the lead time is necessary and adequate for 

manufacturers to select, design, and produce emission control strategies that will work best for 

their product lines. We expect that meeting these requirements will pose a challenge, but one 

that is feasible when taking into consideration the availability and cost of technology, lead time, 

noise, energy, and safety. 

ES-19 

Industry Characterization 

CHAPTER 1: Industry Characterization 

The information contained in this chapter on the Small SI engine and Marine SI engine 

industries was assembled by RTI International, a Health, Social and Economics Research firm in 

cooperation with EPA. RTI prepared one report each on the Small SI and Marine SI industries, 

“Industry Profile for Small Nonroad Spark Ignition Engines and Equipment”1 and “Industry 

Profile for Marine SI Industry”2

 report. The following sections provide a brief report overview. 

The reader is encouraged to refer to the reports for greater detail. In addition, this chapter 

includes an overview of production practices for fuel system component manufacturers. Chapter 

10 provides more information on businesses that would be affected by new standards. 

1.1 Manufacturers of Small SI Engines 

The nonroad spark-ignition (SI) industry includes a wide variety of handheld and 

nonhandheld equipment. Nonhandheld equipment is powered mainly by four-stroke gasoline 

engines; handheld equipment is powered mainly by two-stroke gasoline engines. Comprising 

much of what the general public considers "lawn and garden (L&G) equipment," this industry 

also produces significant numbers of generators, compressors, and construction and maintenance 

equipment. The industry often refers to itself as the "outdoor power equipment" industry. 

The industry profile report prepared by RTI for Small SI provides background 

information on the engines and equipment that make up the small nonroad SI industry, defined 

as those products rated less than or equal to 19 kilowatt (kW) (roughly equivalent to 25 

horsepower [hp]). The profile describes markets for engines and equipment, and discusses their 

use in both consumer and commercial applications. In each market, producers and consumers 

are described, along with product attributes and the effect of those attributes on production cost 

and demand. The market analysis emphasizes assessing suppliers' cost of production and 

industry structure, along with demanders' price responsiveness and consumption alternatives. 

The variety of products in this industry is usefully partitioned by both application 

categories and engine type. Figure 1-1 illustrates the links between the market segments of the 

Small SI engine supply chain included in the profile, from engine manufacturing and sale to 

equipment production, and on to purchase by consumers and commercial customers. Although 

more than 98 percent of total unit sales in the L&G equipment sector go to households, other 

sectors' sales are dominated by commercial equipment. Because of the significantly higher 

prices of commercial units, commercial sales represent a considerable share of the total value of 

production. 

It should be noted that there is a fair amount of vertical integration in the handheld 

industry, with the same parent firm making both engines and the equipment in which those 

engines are used. Handheld equipment includes string trimmers, leaf blowers, and chainsaws. 

This situation is known as "captive" engine production; data on internal consumption of engines 

and transfer prices are typically not available outside the firm. The makers of non-handheld 

1-1 
Final Regulatory Impact Analysis 

engines typically sell their engines to independent equipment manufacturers in a merchant 

engine market, where prices and quantities exchanged can be directly observed. 

The industry profile report prepared by RTI for Small SI presents information on product 

characteristics, supply-side considerations, consumer demand, and market structure for small 

nonroad SI engines. The report also includes similar types of information on equipment 

markets, broken down by application category. Considerations related to consumer and 

commercial markets are included in the report. 

Figure 1-1: The Nonroad Small SI Industry 

C o n s u m e r s 

N o n i n t e g r a t e d 

E q u i p m e n t 

M a n u f a c t u r e rs 

I m p o rt s 

• E n gin es 

• E q u ip m e n t 

In te g ra te d 

E q u i p m e n t 

M a n u f a c t u r e r s 

C a p tiv e 

E n gin e 

M a n u f a c t u r e r s 

M erc h a nt 

E n gin e 

M a n u f a c t u r e rs 

S m a ll S I E n g i n e M a rk e t s 

• C l a s s 

• S iz e 

C o m m e rc ia l U s e r s 

E q u i p m e n t M a r k e ts 

• L a w n m o w e r s 

• H a n d h e l d L a w n a n d G a r d e n 

• O t h e r L a w n a n d G a r d e n 

• G e n e ra to rs a n d W e ld e rs 

• C o m p r e s s o rs a n d P u m p s 

• R e c r e a t io n a l P r o d u c t s 

• S n o w B lo w e r s 

• O t h e r S m a l l S I 

1.2 Manufacturers of Marine Spark-Ignition Engines

 The Marine SI industry is dominated by recreational applications with some commercial 

use and includes markets for several types of boats, personal watercraft (PWC), and SI engines 

that power them. The industry profile presented in the “Industry Profile for Marine SI Industry” 

report by RTI describes producers and consumers for each market segment; product attributes 

and the effects of these attributes on production costs and demand are described as well. As part 

of the market characterization, particular emphasis is placed on assessing suppliers’ industrial 

organization and cost of production and demanders’ price responsiveness and substitution 

possibilities. The Marine SI industry is divided into three applications areas: outboard (OB) 

boats, sterndrive and inboard (SD/I) boats, and PWC. 

1-2 
Industry Characterization 

1.2.1 OB Boats 

An OB boat is a vessel powered by one or more gasoline engines, which are located 

outside the hull at the back of the boat. The engine and drive unit are combined in a single 

package. An engine can easily be removed from the boat for inspection or repair, and it is quite 

common for the boat owner to change engines during the life of the vessel. The OB boat 

segment is the largest of the three application areas; in 2002, 213,000 units were sold, which is 

more than the combined sales of SD/I and PWC. 

The OB application area can be further divided into “recreational” and “luxury” 

categories. The luxury category includes more-expensive vessels, for which the engine 

constitutes only a small portion of the cost of the entire vessel. The NMMA distinguishes 

between 14 types of OB vessels, 10 of which are considered recreational and 4 luxury. 

1.2.2 SD/I Boats 

SD/I vessels have an engine installed inside the hull of the vessel. An inboard vessel is a 

boat in which the engine is located inside the hull at the center of the boat with a propeller shaft 

going through the rear of the boat. A sterndrive (or inboard/outboard) vessel is a boat in which 

the engine is located inside the hull at the back of the boat with a drive assembly couple directly 

to the propeller. propeller shaft going through the rear of the boat. In contrast to OB vessels, 

SD/I vessels’ engine is an integral part. Removal or replacement is significantly more difficult, 

so most repair work is done with the engine in place. Just like OBs, the SD/I application area is 

divided into recreational and luxury categories. 

1.2.3 PWC 

According to the Personal Watercraft Industry Association (PWIA), a PWC is defined as 

a “vessel with an inboard motor powering a water jet pump as its primary source of motive 

power, and which is designed to be operated by a person sitting, standing, or kneeling on the 

vessel.” 

The PWC application area is divided into the entry level, high end, and performance 

categories based on the horsepower ratings of the vessel. These categories correspond to 50 to 

100 hp, 100 to 175 hp, and over 175 hp accordingly. Our study considers two categories that 

were available in 2002: entry level and high end. The performance category was introduced in 

2003. 

1.2.4 Marine SI Engines 

Some OB engine manufacturers specifically build their engines to be incorporated into 

boats produced by another division within the same parent company. Other manufacturers 

produce and sell their engines to independent OB boat builders or consumers who need a 

replacement engine. SD/I engine manufacturers typically build custom engines for SD/I boats 

by marinizing automotive engines. All PWC vessel manufacturers build their own engines for 

1-3 
Final Regulatory Impact Analysis 

their vessels 

Marine SI engines sold today are a mix of three primary technologies: crankcase 

scavenged two-stroke engines, direct-injection two-stroke engines, and four-stroke engines. 

Table 6.2.2-11 in Chapter 6 presents our best estimate of the technology mix for OB and PWC 

engines by power class. This technology mix is based on data submitted by manufacturers when 

the certify to our existing HC+NOx exhaust emission standards. Prior to the implementation of 

the existing standards, the vast majority of outboard and PWC engines were crankcase 

scavenged two-stroke engines. 

The following Figures show the flow of engines from the engine manufacturer to the consumer 

for the different engine types. 

Figure 1-2. OB Marine Economic Model Conceptual Flow Chart 

Consumers 

New Boats 

Equipment Market 

Nonintegrated 

Equipment 

Manufacturers 

Imports 

• Engines 

• Equipment 

Integrated 

Equipment 

Manufacturers 

Captive 

Engine 

Manufacturers 

Merchant 

Engine 

Manufacturers 

Consumers 

Loose Engines 

Marine SI Engine 

Markets 

1-4 
Industry Characterization 

Figure 1-3: PWC Economic Model Conceptual Flow Chart 

Consumer 

Equipment Market 

Integrated Equipment 

Manufacturers 

Captive Engine 

Manufacturers 

Figure 1-4: Inboard Marine Economic Model Conceptual Flow Chart 

Consumers 

Equipment Market 

Nonintegrated 

Equipment 

Manufacturer 

Integrated 

Equipment 

Manufacturer 

Captive 

Engine 

Marinizer 

Merchant 

Engine 

Marinizer 

Automotive Engine 

Market 

Merchant 

Engine 

Manufacturer 

Marinized Engine 

Market 

1-5 
Final Regulatory Impact Analysis 

1.3 Fuel System Components 

The primary fuel system components that would be affected by the rule are the fuel tanks 

and fuel lines on affected equipment and vessels. This section gives an overview of the 

production practices for these products. 

1.3.1 Fuel Tank Production Practices 

Plastic fuel tanks are either blow-molded, injection-molded, or rotational-molded. 

Generally, portable, PWC, and mid-sized Small SI fuel tanks are blow-molded. Blow-molding 

involves forming polyethylene in large molds using air pressure to shape the tank. Because this 

has high fixed costs, blow molding is only used where production volumes are high. This works 

for portable fuel tanks where the volumes are high and a single shape can be used for most 

applications. For portable tanks, the fuel tank manufacturer will generally design the tank, then 

send it out to a blow molder for production. 

Smaller fuel tanks used in Small SI equipment are often injection-molded. In the 

injection molding process, fuel tanks are formed by forcing heated plastic into molds at high 

pressure. Generally, two fuel tank halves are formed, which are later fused together. This 

process requires high tooling costs, but lower total fixed costs than blow-molding. Injectionmolding is typically used for smaller fuel tanks and has the advantage of giving manufacturers 

the ability to work with complex tank designs. 

Larger fuel tanks used on Class II equipment and in boats with installed fuel tanks are 

typically rotational-molded out of cross-link polyethylene. Rotational-molding is a lower cost 

alternative for smaller production volumes. In this method, a mold is filled with a powder form 

of polyethylene with a catalyst material. The mold is rotated in an oven; the heat melts the 

plastic and activates the catalyst which causes a strong cross-link material structure to form. 

This method is used for Class II fuel tanks where the tanks are unshielded on the equipment. 

These fuel tanks also used meet specific size and shape requirements for boats and are preferred 

because they do not rust like metal tanks, but at the same time are more fire resistant than highdensity polyethylene fuel tanks. 

Metal fuel tanks are also used on both Small SI equipment and boats. Typically, metal 

tanks on Small SI equipment are made of steel. These tanks are typically stamped out in two 

pieces and either welded or formed together with a seal. Aluminum fuel tanks are also used 

primarily for installed marine fuel tanks because aluminum is more resistant to oxidation than 

steel. In the marine industry, tank manufacturers generally custom make each tank to meet the 

boat manufacturers needs. Generally, sheet aluminum is used and is cut, bent, and welded into 

the required configuration. 

1.3.2 Fuel Hose Production Practices 

Marine hose is designed to meet the Coast Guard performance requirements as defined 

by the Society of Automotive Engineer’s recommended practice SAE J 1527. For fuel supply 

1-6 
Industry Characterization 

lines, this includes a permeation rate of 100 g/m2

/day at 23°C (Class 1). For other fuel hose not 

normally continuously in contact with fuel (vent and fuel fill neck), the permeation standard is 

300 g/m2

/day (Class 2). In general, boat builders will use Class 1 hose for both fuel supply and 

vent lines for simplicity. Some boat builders use low permeation barrier hose, for which, 

specifications are now included in SAE J 1527. For fuel fill necks, boat builders generally use 

Class 2 hose. Small SI hose is typically produced to manufacturer specifications. However, 

manufacturers may specify hose based on industry standards such as those listed in SAE J30. 

Most fuel supply and vent hose is extruded nitrile rubber with a coating for better wear 

and flame resistance. Hose may also be reinforced with fabric or wire. (In contrast, plastic 

automotive fuel lines are extruded without reinforcement and are generally referred to as 

“tubing.”) Hose manufacturers offer a wide variety of fuel hoses including those with a barrier 

layer of low permeability material, such as nylon, THV, FKM or ethyl vinyl alcohol, either on 

the inside surface or sandwiched between layers of nitrile rubber. These technologies are 

discussed in more detail in Chapter 5. 

Fuel fill hose used on boats is generally manufactured by hand wrapping layers of rubber 

and reinforcement materials around a steel mandril. This hose is then heated to cure the rubber. 

Fuel fill hose generally has a much larger diameter than fuel supply and vent hose and this 

process offers an effective method of producing this larger diameter hose. 

Pre-formed fuel lines are made in two ways. The first, and more common method, is to 

cut lengths of extruded hose, before it is vulcanized, and slip them over a contoured mandril. 

The hose is then vulcanized in the oven on the mandril to give it a preformed shape. The second 

way, primarily used on handheld equipment, but also for some outboard engine fuel system 

components, is to injection-mold small parts. To make the parts hollow, they are molded with a 

mandril inside. To remove the mandril, the part is typically inflated with air for just long enough 

to pull it off the mandril. Primer bulbs are also made in this manner. 

1-7 
Final Regulatory Impact Analysis 

Chapter 1 References 

1. “Industry Profile for Small Nonroad Spark-Ignition Engines and Equipment,” RTI International, October 2006. 

2. “Industry Profile for Marine SI Industry,” RTI International, October 2006. 

1-8 
Final Regulatory Impact Analysis 

CHAPTER 2: Air Quality, Health, and Welfare Concerns 

The standards finalized in this action will reduce emissions of hydrocarbons (HC), 

oxides of nitrogen (NOx), carbon monoxide (CO) and air toxics from the engines, vessels and 

equipment subject to this rule. Emissions of these pollutants contribute to ozone, PM and CO 

nonattainment and to adverse health effects associated with air toxics. The emissions from 

these engines, vessels and equipment also contribute to adverse environmental effects. 

The health and environmental effects associated with emissions from Small SI engines 

and equipment and Marine SI engines and vessels are a classic example of a negative 

externality (an activity that imposes uncompensated costs on others). With a negative 

externality, an activity’s social cost (the cost on society imposed as a result of the activity 

taking place) exceeds its private cost (the cost to those directly engaged in the activity). In 

this case, as described in this chapter, emissions from Small SI engines and equipment and 

Marine SI engines and vessels impose public health and environmental costs on society. The 

market system itself cannot correct this externality. The end users of the equipment and 

vessels are often unaware of the environmental impacts of their use for lawn care or 

recreation. Because of this, consumers fail to send the market a signal to provide cleaner 

equipment and vessels. In addition, producers of these engines, equipment, and vessels are 

rewarded for emphasizing other aspects of these products (e.g., total power). To correct this 

market failure and reduce the negative externality, it is necessary to give producers social cost 

signals. The standards EPA is finalizing will accomplish this by mandating that Small SI 

engines and equipment and Marine SI engines and vessels reduce their emissions to a 

technologically feasible limit. In other words, with this rule the costs of the services provided 

by these engines and equipment will account for social costs more fully. 

In this Chapter we will discuss the impacts of the pollutants emitted by Small SI 

engines and equipment and Marine SI engines and vessels on health and welfare, National 

Ambient Air Quality Standard (NAAQS) attainment, and personal exposure. Air quality 

modeling and monitoring data presented in this chapter indicate that a large number of people 

live in counties that are designated as nonattainment for either or both of the 8-hour ozone or 

PM2.5 NAAQS. Figure 2-1 illustrates the widespread nature of the ozone and PM2.5 

nonattainment areas and also depicts mandatory class I areas. The emission standards in this 

rule will help reduce HC, NOx, PM, air toxic and CO emissions and their associated health 

and environmental effects. 

2-1 
Air Quality, Health and Welfare Concerns 

Figure 2-1: 8-Hour Ozone and PM2.5 Nonattainment Areas and Mandatory Class I 

Federal Areas 

2.1 Ozone 

In this section we review the health and welfare effects of ozone exposure. We also 

describe the air quality monitoring and modeling data that indicates people in many areas 

across the country are exposed to levels of ambient ozone above the 1997 and 2008 ozone 

NAAQS. The data also indicates that in the future people will continue to live in counties 

with ozone levels above the NAAQS without additional federal, state or local measures. 

Emissions of volatile organic compounds (VOCs), of which HC are a subset, and NOx from 

the engines, vessels and equipment subject to this rule contribute to these ozone 

concentrations. Information on air quality was gathered from a variety of sources, including 

monitored ozone concentrations, air quality modeling forecasts conducted for this rulemaking, 

and other state and local air quality information. 

2-2 
Final Regulatory Impact Analysis 

2.1.1 Science of Ozone Formation 

Ground-level ozone pollution is formed by the reaction of VOCs and NOx in the 

atmosphere in the presence of heat and sunlight. These pollutants, often referred to as ozone 

precursors, are emitted by many types of pollution sources such as highway vehicles and 

nonroad engines (including those subject to this rule), power plants, chemical plants, 

refineries, makers of consumer and commercial products, industrial facilities, and smaller area 

sources. 

The science of ozone formation, transport, and accumulation is complex.1 Groundlevel ozone is produced and destroyed in a cyclical set of chemical reactions, many of which 

are sensitive to temperature and sunlight. When ambient temperatures and sunlight levels 

remain high for several days and the air is relatively stagnant, ozone and its precursors can 

build up and result in more ozone than typically would occur on a single high-temperature 

day. Ozone can be transported hundreds of miles downwind of precursor emissions, resulting 

in elevated ozone levels even in areas with low VOC or NOx emissions. 

The highest levels of ozone are produced when both VOC and NOx emissions are 

present in significant quantities on clear summer days. Relatively small amounts of NOx 

enable ozone to form rapidly when VOC levels are relatively high, but ozone production is 

quickly limited by removal of the NOx. Under these conditions NOx reductions are highly 

effective in reducing ozone while VOC reductions have little effect. Such conditions are 

called “NOx-limited”. Because the contribution of VOC emissions from biogenic (natural) 

sources to local ambient ozone concentrations can be significant, even some areas where manmade VOC emissions are relatively low can be NOx-limited. 

Ozone concentrations in an area also can be lowered by the reaction of nitric oxide 

(NO) with ozone, forming nitrogen dioxide (NO2); as the air moves downwind and the cycle 

continues, the NO2 forms additional ozone. The importance of this reaction depends, in part, 

on the relative concentrations of NOx, VOC, and ozone, all of which change with time and 

location. When NOx levels are relatively high and VOC levels relatively low, NOx forms 

inorganic nitrates (i.e., particles) but relatively little ozone. Such conditions are called “VOClimited”. Under these conditions, VOC reductions are effective in reducing ozone, but NOx 

reductions can actually increase local ozone under certain circumstances. Even in VOClimited urban areas, NOx reductions are not expected to increase ozone levels if the NOx 

reductions are sufficiently large. 

Rural areas are usually NOx-limited, due to the relatively large amounts of biogenic 

VOC emissions in such areas. Urban areas can be either VOC- or NOx-limited, or a mixture 

of both, in which ozone levels exhibit moderate sensitivity to changes in either pollutant. 

2.1.2 Health Effects of Ozone Pollution 

Exposure to ambient ozone contributes to a wide range of adverse health effectsA. 

A Human exposure to ozone varies over time due to changes in ambient ozone concentration and because people 

move between locations which have notable different ozone concentrations. Also, the amount of ozone 

2-3 
Air Quality, Health and Welfare Concerns 

These health effects are well documented and are critically assessed in the EPA ozone air 

quality criteria document (ozone AQCD) and EPA staff paper.2,3 We are relying on the data 

and conclusions in the ozone AQCD and staff paper, regarding the health effects associated 

with ozone exposure. 

Ozone-related health effects include lung function decrements, respiratory symptoms, 

aggravation of asthma, increased hospital and emergency room visits, increased asthma 

medication usage, and a variety of other respiratory effects. Cell-level effects such as, 

inflammation of lungs, have been documented as well. In addition, there is suggestive 

evidence of a contribution of ozone to cardiovascular-related morbidity and highly suggestive 

evidence that short-term ozone exposure directly or indirectly contributes to non-accidental 

and cardiopulmonary-related mortality, but additional research is needed to clarify the 

underlying mechanisms causing these effects. In a recent report on the estimation of ozonerelated premature mortality published by the National Research Council (NRC), a panel of 

experts and reviewers concluded that short-term exposure to ambient ozone is likely to 

contribute to premature deaths and that ozone-related mortality should be included in 

estimates of the health benefits of reducing ozone exposure.4 People who appear to be more 

susceptible to effects associated with exposure to ozone include children, asthmatics and the 

elderly. Those with greater exposures to ozone, for instance due to time spent outdoors (e.g., 

children and outdoor workers), are also of concern. 

Based on a large number of scientific studies, EPA has identified several key health 

effects associated with exposure to levels of ozone found today in many areas of the country. 

Short-term (1 to 3 hours) and prolonged exposures (6 to 8 hours) to higher ambient ozone 

concentrations have been linked to lung function decrements, respiratory symptoms, increased 

hospital admissions and emergency room visits for respiratory problems.5, 6, 7, 8, 9, 10 Repeated 

exposure to ozone can increase susceptibility to respiratory infection and lung inflammation 

and can aggravate preexisting respiratory diseases, such as asthma.11, 12, 13, 14, 15 Repeated 

exposure to sufficient concentrations of ozone can also cause inflammation of the lung, 

impairment of lung defense mechanisms, and possibly irreversible changes in lung structure, 

which over time could affect premature aging of the lungs and/or the development of chronic 

respiratory illnesses, such as emphysema and chronic bronchitis.16, 17, 18, 19 

Children and adults who are outdoors and active during the summer months, such as 

construction workers, are among those most at risk of elevated ozone exposures.20 Children 

and outdoor workers tend to have higher ozone exposure because they typically are active 

outside, working, playing and exercising, during times of day and seasons (e.g., the summer) 

when ozone levels are highest.21 For example, summer camp studies in the Eastern United 

States and Southeastern Canada have reported statistically significant reductions in lung 

function in children who are active outdoors.22, 23, 24, 25, 26, 27, 28, 29 Further, children are more at 

risk of experiencing health effects from ozone exposure than adults because their respiratory 

systems are still developing. These individuals (as well as people with respiratory illnesses 

such as asthma, especially asthmatic children) can experience reduced lung function and 

increased respiratory symptoms, such as chest pain and cough, when exposed to relatively low 

delivered to the lung is not only influenced by the ambient concentration but also by the individuals breathing 

route and rate. 

2-4 
Final Regulatory Impact Analysis 

ozone levels during prolonged periods of moderate exertion.30, 31, 32, 33 

2.1.3 Current Ozone Levels 

The small SI and marine SI engine emission reductions will assist ozone 

nonattainment areas in reaching the standard by each area’s respective attainment date and/or 

assist in maintaining the ozone standard in the future. In this and the following section we 

present information on current and model-projected future ozone levels. 

A nonattainment area is defined in the CAA as an area that is violating a NAAQS or is 

contributing to a nearby area that is violating the NAAQS. EPA designated nonattainment 

areas for the 1997 ozone NAAQS in June 2004. The final rule on Air Quality Designations 

and Classifications for the 1997 Ozone NAAQS (69 FR 23858, April 30, 2004) identifies the 

criteria that EPA considered in making the 1997 8-hour ozone nonattainment designations, 

including 2001-2003 measured data, air quality in adjacent areas, and other factors.B 

As of March 12, 2008 there are approximately 140 million people living in 72 areas 

designated as nonattainment with the 1997 8-hour ozone NAAQS. There are 337 full or 

partial counties that make up the 8-hour ozone nonattainment areas. These numbers do not 

include the people living in areas where there is a future risk of failing to maintain or attain 

the 8-hour ozone NAAQS. The 1997 8-hour ozone nonattainment areas, nonattainment 

counties, and populations are listed in Appendix 2A to this RIA. 

EPA has recently amended the ozone NAAQS (73 FR 16436, March 27, 2008). The 

final ozoneNAAQS rule addresses revisions to the primary and secondary NAAQS for ozone 

to provide increased protection of public health and welfare, respectively. With regard to the 

primary standard for ozone, EPA has revised the level of the 8-hour standard to 0.075 parts 

per million (ppm), expressed to three decimal places. With regard to the secondary standard 

for ozone, EPA has revised the current 8-hour standard by making it identical to the revised 

primary standard. 

States with ozone nonattainment areas are required to take action to bring those areas 

into compliance in the future. The attainment date assigned to an ozone nonattainment area is 

based on the area’s classification. Most ozone nonattainment areas will be required to attain 

the 1997 8-hour ozone NAAQS in the 2007 to 2013 time frame and then be required to 

maintain it thereafter.C

 The attainment dates associated with the potential nonattainment areas 

B

 An ozone design value is the concentration that determines whether a monitoring site meets the NAAQS for 

ozone. Because of the way they are defined, design values are determined based on three consecutive-year 

monitoring periods. For example, an 8-hour ozone design value is the fourth highest daily maximum 8-hour 

average ozone concentration measured over a three-year period at a given monitor. The full details of these 

determinations (including accounting for missing values and other complexities) are given in Appendices H and 

I of 40 CFR Part 50. For a county, the design value is the highest design value from among all the monitors with 

valid design values within that county. If a county does not contain an ozone monitor, it does not have a design 

value. However, readers should note that ozone design values generally represent air quality across a broad area 

and that absence of a design value does not imply that the county is in compliance with the ozone NAAQS. 

C

 The Los Angeles South Coast Air Basin 8-hour ozone nonattainment area is designated as severe and will have 

to attain before June 15, 2021. The South Coast Air Basin has recently applied to be redesignated as an extreme 

2-5 
Air Quality, Health and Welfare Concerns 

based on the 2008 8-hour ozone NAAQS will likely be in the 2013 to 2021 timeframe, 

depending on the severity of the problem. Table 2-1 provides an estimate, based on 2004-06 

air quality data, of the counties with design values greater than the 2008 ozone NAAQS. We 

expect many of the ozone nonattainment areas will need to adopt additional emissions 

reduction programs to attain and maintain the ozone NAAQS. The expected VOC and NOx 

reductions from these standards, which take effect between 2009 and 2013, will be useful to 

states as they seek to either attain or maintain the ozone NAAQS. 

Table 2-1 Counties with Design Values Greater Than the 2008 Ozone NAAQS Based on 

2004-2006 Air Quality Data 

Number of Counties Populationa 

1997 Ozone Standard: counties within the 72 

areas currently designated as nonattainment 

337 139,633,458 

2008 Ozone Standard: additional counties that 

would not meet the 2008 NAAQSb 

74 15,984,135 

Total 411 155,617,593 

Notes: 

a

 Population numbers are from 2000 census data. 

b

 Attainment designations for the 2008 ozone NAAQS have not yet been made. Nonattainment for the 2008 

Ozone NAAQS will be based on three years of air quality data from later years. Also, the county numbers in the 

table include only the counties with monitors violating the 2008 Ozone NAAQS. The numbers in this table may 

be an underestimate of the number of counties and populations that will eventually be included in areas with 

multiple counties designated nonattainment. 

2.1.4 Projected Ozone Levels 

In conjunction with this rulemaking, we performed a series of air quality modeling 

simulations for the continental U.S. The model simulations were performed for several 

emissions scenarios including the following: 2002 baseline projection, 2020 baseline 

projection, 2020 baseline projection with small SI/marine SI engine controls, 2030 baseline 

projection, and 2030 baseline projection with small SI/marine SI engine controls. Information 

on the air quality modeling methodology is contained in Section 2.3 as well as the air quality 

modeling technical support document (AQ TSD). In the following sections we describe our 

modeling of 8-hour ozone levels in the future with and without the controls being finalized in 

this action. 

2.1.4.1 Projected 8-Hour Ozone Levels without this Rulemaking 

EPA has already adopted many emission control programs that are expected to reduce 

ambient ozone levels. These control programs include the Locomotive and Marine Rule (73 

FR 25098, May 6, 2008), Clean Air Interstate Rule (70 FR 25162, May 12, 2005), the Clean 

Air Nonroad Diesel rule (69 FR 38957, June 29, 2004), and the Heavy Duty Engine and 

Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements (66 FR 5002, Jan. 

18, 2001). As a result of these programs, the number of areas that continue to violate the 8-

hour ozone NAAQS in the future is expected to decrease. 

nonattainment area which will make their attainment date June 15, 2024. 

2-6 
Final Regulatory Impact Analysis 

The baseline air quality modeling completed for this rule predicts that without 

additional local, regional or national controls there will continue to be a need for reductions in 

8-hour ozone concentrations in some areas in the future. The determination that an area is at 

risk of exceeding the 8-hour ozone standard in the future was made for all areas with current 

design values greater than or equal to 85 ppb (or within a 10 percent margin) and with 

modeling evidence that concentrations at and above these levels will persist into the future.D 

Those interested in greater detail should review the air quality modeling TSD which is 

included in the docket for this rule.34 

The baseline inventories that underlie the modeling conducted for this rulemaking 

include emission reductions from existing federal, state and local controls. There was no 

attempt to examine the prospects of areas attaining or maintaining the standard with future 

possible controls. We expect many of the areas to adopt additional emission reduction 

programs, but we are unable to quantify or rely upon future reductions from additional 

programs since they have not yet been promulgated. With reductions from programs already 

in place (but excluding the emission reductions from this rule), the number of counties in 

2020 with projected 8-hour ozone design values at or above 85 ppb is expected to be 8 with a 

population of 22 million people. In addition, in 2020, 37 counties where 27 million people 

are projected to live, will be within 10 percent of violating the 1997 8-hour ozone NAAQS. 

The results should therefore be interpreted as indicating counties at risk for violating the 

ozone NAAQS in the future without additional federal, state or local measures in addition to 

this rulemaking. 

2.1.4.2 Projected 8-Hour Ozone Levels with this Rulemaking 

This section summarizes the results of our modeling of ozone air quality impacts in 

the future due to the reductions in small SI and marine SI emissions finalized in this action. 

Specifically, we compare baseline scenarios to scenarios with controls. Our modeling 

indicates that the reductions from this rule will provide nationwide improvements in ambient 

ozone concentrations and minimize the risk of exposures in future years. Since some of the 

VOC and NOx emission reductions from this rule go into effect during the period when some 

areas are still working to attain the 8-hour ozone NAAQS, the projected emission reductions 

will assist state and local agencies in their effort to attain the 8-hour ozone standard and help 

others maintain the standard. Emissions reductions from this rule will also help to counter 

potential ozone increases due to climate change, which are expected in many urban areas in 

the United States, but are not reflected in the modeling shown here.35 

On a population-weighted basis, the average modeled future-year 8-hour ozone design 

values will decrease by 0.57 ppb in 2020 and 0.76 ppb in 2030. Table 2-2 shows the average 

change in future year eight-hour ozone design values for: (1) all counties with 2002 baseline 

design values, (2) counties with baseline design values that exceeded the standard in 2000-

2004 (“violating” counties), (3) counties that did not exceed the standard, but were within 10 

percent of it in 2000-2004, (4) counties with future year design values that exceeded the 

D Ozone design values are reported in parts per million (ppm) as specified in 40 CFR Part 50. Due to the scale of 

the design value changes in this action results have been presented in parts per billion (ppb) format. 

2-7 
Air Quality, Health and Welfare Concerns 

standard, and (5) counties with future year design values that did not exceed the standard, but 

were within 10 percent of it in 2020 and 2030. Counties within ten percent of the standard are 

intended to reflect counties that meet the standard, but will likely benefit from help in 

maintaining that status in the face of growth. All of these metrics show a decrease in 2020 

and 2030, indicating in five different ways the overall improvement in ozone air quality. 

Table 2-2 Average Change in Projected Future Year 8-hour Ozone Design Value as a Result 

of the Small SI and Marine SI controls 

Averagea Number 

of US 

Counties 

Change in 

2020 design 

valueb

 (ppb) 

Change in 

2030 design 

valueb (ppb) 

All 660 -0.47 -0.66 

All, population-weighted 660 -0.57 -0.76 

Counties whose base year is violating the 1997 

8-hour ozone standard 

261 -0.62 -0.88 

Counties whose base year is violating the 1997 

8-hour ozone standard, population-weighted 

261 -0.61 -0.80 

Counties whose base year is within 10 percent of 

the 1997 8-hour ozone standard 

223 -0.42 -0.61 

Counties whose base year is within 10 percent of 

the 1997 8-hour ozone standard, populationweighted 

223 -0.55 -0.78 

Counties whose future year is violating the 1997 

8-hour ozone standard 

8 (2020) 

6 (2030) 

-0.13 -0.10 

Counties whose future year is violating the 1997 

8-hour ozone standard, population-weighted 

8 (2020) 

6 (2030) 

-0.17 -0.13 

Counties whose future year is within 10 percent 

of the 1997 8-hour ozone standard 

37 (2020) 

23 (2030) 

-0.71 -1.05 

Counties whose future year is within 10 percent 

of the 1997 8-hour ozone standard, populationweighted 

37 (2020) 

23 (2030) 

-0.54 -0.79 

Notes: a averages are over counties with 2002 modeled design values b

 Ozone design values are reported in parts per million (ppm) as specified in 40 CFR Part 50. Due to the scale of 

the design value changes in this action results have been presented in parts per billion (ppb) format. 

Table 2-3 lists the counties with projected 8-hour ozone design values that violate or 

are within 10 percent of the 1997 8-hour ozone standard in 2020after application of the small 

SI and marine SI controls. Counties are marked with a “V” in the table if their projected 

design values are greater than or equal to 85 ppb. Counties are marked with an “X” in the 

table if their projected annual design values are greater than or equal to 76.5 ppb, but less than 

85 ppb. The counties marked “X” are not projected to violate the standard, but to be close to 

it, so the rule will help assure that these counties continue to meet the standard. The current 

design values are also presented in Table 2-3. Recall that we project future design values only 

for counties that have current design values, so this list is limited to those counties with 

ambient monitoring data sufficient to calculate current 3-year design values. 

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Final Regulatory Impact Analysis 

Figure 2-2 illustrates the geographic impact of the small SI and marine SI engine 

controls on 8-hour ozone design values in 2020. Some of the most significant decreases will 

occur in the great lakes region, the gulf coast region, the northeast corridor and in the Seattle 

region. The maximum decreases in a 2020 design values is 2.0 ppb in Cape Cod, 

Massachusetts. 

2-9 
Air Quality, Health and Welfare Concerns 

Table 2-3 Counties with 2020 8-hour Ozone Design Values in Violation or Within 10 percent 

of the 1997 Ozone Standard as a Result of the Small SI and Marine SI Controls 

State County 

2000-2004 

Average 8-Hour 

Ozone DV (ppb)a 

2020 modeling 

projections of 

8-Hour Ozone 

DV 

2020 

Population 

CA El Dorado 105.0 X 236,310 

CA Fresno 110.0 X 1,066,878 

CA Kern 114.3 X 876,131 

CA Kings 95.7 V 173,390 

CA Los Angeles 121.3 X 10,376,013 

CA Madera 91.0 V 173,940 

CA Merced 101.7 V 277,863 

CA Nevada 97.7 V 131,831 

CA Orange 85.3 V 3,900,599 

CA Placer 98.3 V 451,620 

CA Riverside 115.0 X 2,252,510 

CA Sacramento 99.0 V 1,640,590 

CA San Bernardino 128.7 X 2,424,764 

CA San Diego 92.3 V 3,863,460 

CA Stanislaus 95.0 V 607,766 

CA Tulare 105.7 X 477,296 

CA Tuolumne 91.0 V 70,570 

CT Fairfield 98.3 V 962,824 

CT New Haven 98.3 V 898,415 

IN Lake 88.3 V 509,293 

LA East Baton Rouge 87.0 V 522,399 

MD Harford 100.3 V 317,847 

NJ Camden 99.7 V 547,817 

NJ Gloucester 98.0 V 304,105 

NJ Mercer 97.7 V 392,236 

NJ Ocean 105.7 V 644,323 

NY Suffolk 97.0 V 1,598,742 

OH Ashtabula 95.7 V 108,355 

OH Geauga 99.0 V 114,438 

PA Bucks 99.0 V 711,275 

PA Philadelphia 96.7 V 1,394,176 

TX Brazoria 94.0 V 322,385 

TX Harris 102.0 X 4,588,812 

TX Jefferson 91.0 V 272,075 

WI Kenosha 98.3 V 184,825 

WI Racine 91.7 V 212,351 

WI Sheboygan 97.0 V 128,777 

Notes: a

 Ozone design values are reported in parts per million (ppm) as specified in 40 CFR Part 50. Due to the scale of 

the design value changes in this action results have been presented in parts per billion (ppb) format. 

2-10 
Final Regulatory Impact Analysis 

Number of Counties 

1 

69 

186 360 

Legend

<= -2.0 > -2.0 to -1.0 > -1.0 to -0.5 = 0.0 > 0.0 > -0.5 to -0.1 

44

0 2020cc_b

Figure 2-2 Impact of Small SI and Marine SI controls on 8-hour Ozone Design Values in 2020 (units are 

2-11 
2.1.5 Environmental Effects of Ozone Pollution 

There are a number of public welfare effects associated with the presence of ozone in 

the ambient air.36 In this section we discuss the impact of ozone on plants, including trees, 

agronomic crops and urban ornamentals. 

2.1.5.1 Impacts on Vegetation 

The Air Quality Criteria Document for Ozone and related Photochemical Oxidants 

notes that “ozone affects vegetation throughout the United States, impairing crops, native 

vegetation, and ecosystems more than any other air pollutant. Like carbon dioxide (CO2) and 

other gaseous substances, ozone enters plant tissues primarily through apertures (stomata) in 

leaves in a process called “uptake”.37 Once sufficient levels of ozone, a highly reactive 

substance, (or its reaction products) reaches the interior of plant cells, it can inhibit or damage 

essential cellular components and functions, including enzyme activities, lipids, and cellular 

membranes, disrupting the plant's osmotic (i.e., water) balance and energy utilization 

patterns.38,39 This damage is commonly manifested as visible foliar injury such as chlorotic or 

necrotic spots, increased leaf senescence (accelerated leaf aging) and/or reduced 

photosynthesis. All these effects reduce a plant’s capacity to form carbohydrates, which are 

the primary form of energy used by plants.40 With fewer resources available, the plant 

reallocates existing resources away from root growth and storage, above ground growth or 

yield, and reproductive processes, toward leaf repair and maintenance. Studies have shown 

that plants stressed in these ways may exhibit a general loss of vigor, which can lead to 

secondary impacts that modify plants' responses to other environmental factors. Specifically, 

plants may become more sensitive to other air pollutants, more susceptible to disease, insect 

attack, harsh weather (e.g., drought, frost) and other environmental stresses. Furthermore, 

there is evidence that ozone can interfere with the formation of mycorrhiza, essential 

symbiotic fungi associated with the roots of most terrestrial plants, by reducing the amount of 

carbon available for transfer from the host to the symbiont.41,42 

Ozone can produce both acute and chronic injury in sensitive species depending on the 

concentration level and the duration of the exposure. Ozone effects also tend to accumulate 

over the growing season of the plant, so that even lower concentrations experienced for a 

longer duration have the potential to create chronic stress on sensitive vegetation. Not all 

plants, however, are equally sensitive to ozone. Much of the variation in sensitivity between 

individual plants or whole species is related to the plant’s ability to regulate the extent of gas 

exchange via leaf stomata (e.g., avoidance of O3 uptake through closure of stomata).43,44,45 

Other resistance mechanisms may involve the intercellular production of detoxifying 

substances. Several biochemical substances capable of detoxifying ozone have been reported 

to occur in plants including the antioxidants ascorbate and glutathione. After injuries have 

occurred, plants may be capable of repairing the damage to a limited extent.46 

Because of the differing sensitivities among plants to ozone, ozone pollution can also 

exert a selective pressure that leads to changes in plant community composition. Given the 

range of plant sensitivities and the fact that numerous other environmental factors modify 

plant uptake and response to ozone, it is not possible to identify threshold values above which 

2-12 
Regulatory Impact Analysis 

ozone is consistently toxic for all plants. The next few paragraphs present additional 

information on ozone damage to trees, ecosystems, agronomic crops and urban ornamentals. 

Ozone also has been conclusively shown to cause discernible injury to forest trees.47,48 

In terms of forest productivity and ecosystem diversity, ozone may be the pollutant with the 

greatest potential for regional-scale forest impacts. Studies have demonstrated repeatedly that 

ozone concentrations commonly observed in polluted areas can have substantial impacts on 

plant function.49, 50 

Because plants are at the center of the food web in many ecosystems, changes to the 

plant community can affect associated organisms and ecosystems (including the suitability of 

habitats that support threatened or endangered species and below ground organisms living in 

the root zone). Ozone impacts at the community and ecosystem level vary widely depending 

upon numerous factors, including concentration and temporal variation of tropospheric ozone, 

species composition, soil properties and climatic factors.51 In most instances, responses to 

chronic or recurrent exposure in forested ecosystems are subtle and not observable for many 

years. These injuries can cause stand-level forest decline in sensitive ecosystems.52,53,54 It is 

not yet possible to predict ecosystem responses to ozone with much certainty; however, 

considerable knowledge of potential ecosystem responses has been acquired through longterm observations in highly damaged forests in the United States. 

Laboratory and field experiments have also shown reductions in yields for agronomic 

crops exposed to ozone, including vegetables (e.g., lettuce) and field crops (e.g., cotton and 

wheat). The most extensive field experiments, conducted under the National Crop Loss 

Assessment Network (NCLAN) examined 15 species and numerous cultivars. The NCLAN 

results show that “several economically important crop species are sensitive to ozone levels 

typical of those found in the Unites States.”55 In addition, economic studies have shown 

reduced economic benefits as a result of predicted reductions in crop yields associated with 

observed ozone levels.56, 57, 58 

Urban ornamentals represent an additional vegetation category likely to experience 

some degree of negative effects associated with exposure to ambient ozone levels. It is 

estimated that more than $20 billion (1990 dollars) are spent annually on landscaping using 

ornamentals, both by private property owners/tenants and by governmental units responsible 

for public areas.59 This is therefore a potentially costly environmental effect. However, in the 

absence of adequate exposure-response functions and economic damage functions for the 

potential range of effects relevant to these types of vegetation, no direct quantitative analysis 

has been conducted. 

2.2 Particulate Matter 

In this section we review the health and welfare effects of PM. We also describe air 

quality monitoring and modeling data that indicate many areas across the country continue to 

be exposed to levels of ambient PM above the NAAQS. Emissions of PM, HCs and NOx 

from the engines, vessels and equipment subject to this rule contribute to these PM 

concentrations. Information on air quality was gathered from a variety of sources, including 

2-13 
monitored PM concentrations, air quality modeling forecasts conducted for this rulemaking, 

and other state and local air quality information. 

2.2.1 Science of PM Formation 

Particulate matter (PM) represents a broad class of chemically and physically diverse 

substances. It can be principally characterized as discrete particles that exist in the condensed 

(liquid or solid) phase spanning several orders of magnitude in size. PM10 refers to particles 

generally less than or equal to 10 micrometers (Fm) in aerodynamic diameter. PM2.5 refers to 

fine particles, generally less than or equal to 2.5 Fm in aerodynamic diameter. Inhalable (or 

"thoracic") coarse particles refer to those particles generally greater than 2.5 Fm but less than 

or equal to 10 Fm in aerodynamic diameter. Ultrafine PM refers to particles generally less 

than 100 nanometers (0.1 Fm) in aerodynamic diameter. Larger particles (>10 Fm) tend to be 

removed by the respiratory clearance mechanisms, whereas smaller particles are deposited 

deeper in the lungs. 

Fine particles are produced primarily by combustion processes and by transformations 

of gaseous emissions (e.g., SOx, NOx and VOCs) in the atmosphere. The chemical and 

physical properties of PM2.5 may vary greatly with time, region, meteorology and source 

category. Thus, PM2.5, may include a complex mixture of different pollutants including 

sulfates, nitrates, organic compounds, elemental carbon and metal compounds. These 

particles can remain in the atmosphere for days to weeks and travel through the atmosphere 

hundreds to thousands of kilometers. 

Particles span many sizes and shapes and consist of hundreds of different chemicals. 

Particles are emitted directly from sources and are also formed through atmospheric chemical 

reactions; the former are often referred to as “primary” particles, and the latter as “secondary” 

particles. In addition, there are also physical, non-chemical reaction mechanisms that 

contribute to secondary particles. Particle pollution also varies by time of year and location 

and is affected by several weather-related factors, such as temperature, clouds, humidity, and 

wind. A further layer of complexity comes from a particle’s ability to shift between 

solid/liquid and gaseous phases, which is influenced by concentration, meteorology, and 

temperature. 

2.2.2 Health Effects of PM 

As stated in EPA’s Particulate Matter Air Quality Criteria Document (PM AQCD), 

available scientific findings “demonstrate well that human health outcomes are associated 

with ambient PM.”E

 We are relying on the data and conclusions in the PM AQCD and PM 

Staff Paper, which reflects EPA’s analysis of policy-relevant science from the PM AQCD, 

regarding the health effects associated with particulate matter.60,61 We also present additional 

E

 Personal exposure includes contributions from many different types of particles, from many sources, and in 

many different environments. Total personal exposure to PM includes both ambient and nonambient 

components; and both components may contribute to adverse health effects. 

2-14 
Regulatory Impact Analysis 

recent studies published after the cut-off date for the PM AQCD.F62 Taken together this 

information supports the conclusion that PM-related emissions such as those controlled in this 

action are associated with adverse health effects. Information on PM-related mortality and 

morbidity is presented first, followed by information on near-roadway exposure studies, 

marine ports and rail yard exposure studies. 

2.2.2.1 Short-term Exposure Mortality and Morbidity Studies 

As discussed in the PM AQCD, short-term exposure to PM2.5 is associated with 

mortality from cardiopulmonary diseases (PM AQCD, p. 8-305), hospitalization and 

emergency department visits for cardiopulmonary diseases (PM AQCD, p. 9-93), increased 

respiratory symptoms (PM AQCD, p. 9-46), decreased lung function (PM AQCD Table 8-34) 

and physiological changes or biomarkers for cardiac changes (PM AQCD, Section 8.3.1.3.4). 

In addition, the PM AQCD describes a limited body of new evidence from epidemiologic 

studies for potential relationships between short term exposure to PM and health endpoints 

such as low birth weight, preterm birth, and neonatal and infant mortality. (PM AQCD, 

Section 8.3.4). 

Among the studies of effects from short-term exposure to PM2.5, several specifically 

address the contribution of mobile sources to short-term PM2.5 effects on daily mortality. 

These studies indicate that there are statistically significant associations between mortality 

and PM related to mobile source emissions (PM AQCD, p.8-85). The analyses incorporate 

source apportionment tools into daily mortality studies and are briefly mentioned here. 

Analyses incorporating source apportionment by factor analysis with daily time-series studies 

of daily death indicated a relationship between mobile source PM2.5 and mortality.63,64 

Another recent study in 14 U.S. cities examined the effect of PM10 exposures on daily hospital 

admissions for cardiovascular disease. This study found that the effect of PM10 was 

significantly greater in areas with a larger proportion of PM10 coming from motor vehicles, 

indicating that PM10 from these sources may have a greater effect on the toxicity of ambient 

PM10 when compared with other sources.65 These studies provide evidence that PM-related 

emissions, specifically from mobile sources, are associated with adverse health effects 

Long-term Exposure Mortality and Morbidity Studies 

Long-term exposure to elevated ambient PM2.5 is associated with mortality from 

cardiopulmonary diseases and lung cancer (PM AQCD, p. 8-307), and effects on the 

respiratory system such as decreased lung function or the development of chronic respiratory 

disease (PM AQCD, pp. 8-313, 8-314). Of specific importance to this rulemaking, the PM 

AQCD also notes that the PM components of gasoline and diesel engine exhaust represent 

F

 These additional studies are included in the 2006 Provisional Assessment of Recent Studies on Health Effects 

of Particulate Matter Exposure. The provisional assessment did not and could not (given a very short timeframe) 

undergo the extensive critical review by EPA, CASAC, and the public, as did the PM AQCD. The provisional 

assessment found that the “new” studies expand the scientific information and provide important insights on the 

relationship between PM exposure and health effects of PM. The provisional assessment also found that “new” 

studies generally strengthen the evidence that acute and chronic exposure to fine particles and acute exposure to 

thoracic coarse particles are associated with health effects. 

2-15 
one class of hypothesized likely important contributors to the observed ambient PM-related 

increases in lung cancer incidence and mortality (PM AQCD, p. 8-318). 

The PM AQCD and PM Staff Paper emphasize the results of two long-term studies, 

the Six Cities and American Cancer Society (ACS) prospective cohort studies, based on 

several factors – the inclusion of measured PM data, the fact that the study populations were 

similar to the general population, and the fact that these studies have undergone extensive 

reanalysis (PM AQCD, p. 8-306, Staff Paper, p.3-18).66,67,68 These studies indicate that there 

are significant associations for all-cause, cardiopulmonary, and lung cancer mortality with 

long-term exposure to PM2.5. One analysis of a subset of the ACS cohort data, which was 

published after the PM AQCD was finalized but in time for the 2006 Provisional Assessment, 

found a larger association than had previously been reported between long-term PM2.5 

exposure and mortality in the Los Angeles area using a new exposure estimation method that 

accounted for variations in concentration within the city.69 

As discussed in the PM AQCD, the morbidity studies that combine the features of 

cross-sectional and cohort studies provide the best evidence for chronic exposure effects. 

Long-term studies evaluating the effect of ambient PM on children’s development have 

shown some evidence indicating effects of PM2.5 and/or PM10 on reduced lung function 

growth (PM AQCD, Section 8.3.3.2.3). In another recent publication included in the 2006 

Provisional Assessment, investigators in southern California reported the results of a crosssectional study of outdoor PM2.5 and measures of atherosclerosis in the Los Angeles basin.70 

The study found significant associations between ambient residential PM2.5 and carotid 

intima-media thickness (CIMT), an indicator of subclinical atherosclerosis, an underlying 

factor in cardiovascular disease. 

2.2.2.3 Roadway-Related PM Exposure and Health Studies 

A recent body of studies examines traffic-related PM exposures and adverse health 

effects. These studies are relevant to this rule because highway SI vehicles and nonroad SI 

engines, vessels and equipment have similar chemical and physical exhaust properties. 

However, this comparison is qualitative in nature since the near-road environment is 

influenced by both gasoline (SI) and diesel vehicles, as well as re-entrained road dust and 

brake and tire wear. One study was done in North Carolina looking at concentrations of PM2.5 

inside police cars and corresponding physiological changes in the police personnel driving the 

cars. The authors report significant elevations in markers of cardiac risk associated with 

concentrations of PM2.5 inside police cars on North Carolina state highways.71 Other studies 

have found associations between traffic-generated particle concentrations at residences and 

adverse effects, including all-cause mortality, infant respiratory symptoms, and reduced 

cognitive functional development.72,73,74,75 There are other pollutants present in the near 

roadway environment, including air toxics which are discussed in Section 2.4. Additional 

information on near-roadway health effects can be found in the recent Mobile Source Air 

Toxics rule (72 FR 8428, February 26, 2007). 

2-16 
Regulatory Impact Analysis 

2.2.3 Current and Projected PM Levels 

The emission reductions from this rule will assist PM nonattainment areas in reaching 

the standard by each area’s respective attainment date and assist PM maintenance areas in 

maintaining the PM standards in the future. In this and the following section we present 

information on current and model-projected future PM levels. 

2.2.3.1 Current PM2.5 Levels 

The small SI and marine SI engine emission reductions will assist PM nonattainment 

areas in reaching the standard by each area’s respective attainment date and/or assist in 

maintaining the PM standard in the future. In this and the following section we present 

information on current and model-projected future PM levels. 

A nonattainment area is defined in the Clean Air Act (CAA) as an area that is 

violating an ambient standard or is contributing to a nearby area that is violating the standard. 

In 2005, EPA designated 39 nonattainment areas for the 1997 PM2.5 NAAQS based on air 

quality design values and a number of other factors (70 FR 943, January 5, 2005; 70 FR 

19844, April 14, 2005).G These areas are comprised of 208 full or partial counties with a total 

population exceeding 88 million. The 1997 PM2.5 nonattainment counties, areas and 

populations, as of March 2008, are listed in Appendix 2B to this RIA. 

EPA has recently amended the NAAQS for PM2.5 (71 FR 61144, October 17, 2006). 

The final PM NAAQS rule addressed revisions to the primary and secondary NAAQS for 

PM2.5 to provide increased protection of public health and welfare, respectively. The primary 

PM2.5 NAAQS includes a short-term (24-hour) and a long-term (annual) standard. The level 

of the 24-hour PM2.5 NAAQS has been revised from 65 μg/m3

to 35 μg/m3 to provide increased 

protection against health effects associated with short-term exposures to fine particles. The 

current form of the 24-hour PM2.5 standard was retained (e.g., based on the 98th percentile 

concentration averaged over three years). The level of the annual PM2.5 NAAQS was retained 

at 15μg/m3

, continuing protection against health effects associated with long-term exposures. 

The current form of the annual PM2.5 standard was retained as an annual arithmetic mean 

averaged over three years, however, the following two aspects of the spatial averaging criteria 

were narrowed: (1) the annual mean concentration at each site will now be within 10 percent 

of the spatially averaged annual mean, and (2) the daily values for each monitoring site pair 

will now yield a correlation coefficient of at least 0.9 for each calendar quarter. 

With regard to the secondary standards for PM2.5, EPA has revised these standards to 

be identical in all respects to the revised primary standards. Specifically, EPA has revised the 

current 24-hour PM2.5 secondary standard by making it identical to the revised 24-hour PM2.5 

primary standard and retained the annual PM2.5 secondary standard. This suite of secondary 

PM2.5 standards is intended to provide protection against PM-related public welfare effects, 

including visibility impairment, effects on vegetation and ecosystems, and material damage 

and soiling. 

G The full details involved in calculating a PM2.5 design value are given in Appendix N of 40 CFR Part 50. 

2-17 
States with PM2.5 nonattainment areas will be required to take action to bring those 

areas into compliance in the future. Most PM2.5 nonattainment areas will be required to attain 

the 1997 PM2.5 NAAQS in the 2010 to 2015 time frame and then be required to maintain the 

1997 PM2.5 NAAQS thereafter.H Nonattainment areas will be designated with respect to the 

2006 PM2.5 NAAQS in early 2010. The attainment dates associated with the potential 

nonattainment areas based on the 2006 PM2.5 NAAQS will likely be in the 2014 to 2019 

timeframe. Table 2-4 provides an estimate, based on 2003-05 air quality data, of the counties 

with design values greater than the 2006 PM2.5 NAAQS. The emission standards being 

finalized in this action will become effective between 2009 and 2013. The expected PM2.5 

inventory reductions will be useful to states in attaining or maintaining the PM2.5 NAAQS. 

Table 2-4 Counties with Design Values Greater Than the 2006 PM2.5 NAAQS Based on 2003-

2005 Air Quality Data 

Number of Counties Populationa 

1997 PM2.5 Standards: counties within the 39 

areas currently designated as nonattainment 

208 88,394,000 

2006 PM2.5 Standards: additional counties that 

would not meet the 2006 NAAQSb 

49 18,198,676 

Total 257 106,592,676 

Notes: 

a

 Population numbers are from 2000 census data. 

b

 Attainment designations for the 2006 PM2.5 NAAQS have not yet been made. Nonattainment for the 2006 

PM2.5 NAAQS will be based on three years of air quality data from later years. Also, the county numbers in the 

table include only the counties with monitors violating the 2006 PM2.5 NAAQS. The numbers in this table may 

be an underestimate of the number of counties and populations that will eventually be included in areas with 

multiple counties designated nonattainment. 

H The EPA finalized PM2.5 attainment and nonattainment areas in April 2005. The EPA finalized the PM 

Implementation rule in March 2007. 

2-18 
Regulatory Impact Analysis 

2.2.3.2 Current PM10 Levels 

EPA designated PM10 nonattainment areas in 1990.I As of March 2008, 

approximately 28 million people live in the 47 areas that are designated as PM10 

nonattainment, for either failing to meet the PM10 NAAQS or for contributing to poor air 

quality in a nearby area. There are 46 full or partial counties that make up the PM10 

nonattainment areas.J 

2.2.3.3 Projected PM2.5 Levels 

In conjunction with this rulemaking, we performed a series of air quality modeling 

simulations for the continental U.S. The model simulations were performed for several 

emissions scenarios including the following: 2002 baseline projection, 2020 baseline 

projection, 2020 baseline projection with small SI/marine SI engine controls, 2030 baseline 

projection, and 2030 baseline projection with small SI/marine SI engine controls. Information 

on the air quality modeling methodology is contained in Section 2.3 as well as the air quality 

modeling technical support document (AQ TSD). In the following sections we describe 

projected PM2.5 levels in the future with and without the controls being finalized in this action. 

2.2.3.2.1 Projected PM2.5 Levels without this Rulemaking 

Even with the implementation of all current state and federal regulations, including the 

Locomotive and Marine Rule, CAIR Rule, the NOx SIP call, nonroad and on-road diesel rules 

and the Tier 2 rule, there are projected to be U.S. counties violating the PM2.5 NAAQS well 

into the future. The model outputs from the 2002, 2020 and 2030 baselines, combined with 

current air quality data, were used to identify areas expected to exceed the PM2.5 NAAQS in 

the future. 

The baseline air quality modeling conducted for this final rule projects that in 2020, 

with all current controls in effect, up to 11 counties, with a population of 25 million people, 

may not attain the annual standard of 15 μg/m3. This does not account for additional areas 

that have air quality measurements within 10 percent of the PM2.5 standard. These areas, 

although not violating the standard, will also benefit from the emissions reductions, ensuring 

long term maintenance of the PM NAAQS. For example, in 2020, an additional 16 million 

people are projected to live in 13 counties that have air quality measurements within 10 

percent of the 2006 PM NAAQS. This modeling supports the conclusion that there are a 

substantial number of counties across the US projected to experience PM2.5 concentrations at 

or above the PM2.5 NAAQS into the future. Emission reductions from small SI and marine SI 

engines will be helpful for these counties in attaining and maintaining the PM2.5 NAAQS. 

I

 A PM10 design value is the concentration that determines whether a monitoring site meets the NAAQS for 

PM10. The full details involved in calculating a PM10 design value are given in Appendices H and I of 40 CFR 

Part 50. 

J

 The PM10 nonattainment areas are listed in Appendix 2C to this RIA. 

2-19 
2.2.3.2.2 Projected PM2.5 Levels With this Rulemaking 

The impacts of the small SI and marine SI engine controls were determined by 

comparing the model results in the future year control runs against the baseline simulations of 

the same year. On a population-weighted basis, the average modeled future-year annual 

PM2.5 design value (DV) for all counties is expected to decrease by 0.02 μg/m3 in 2020 and 

2030. There are areas with larger decreases in their future-year annual PM2.5 DV, for instance 

the Chicago region will experience a 0.08 μg/m3 reduction by 2030. Figure 2-3 illustrates the 

geographic impact of the small SI and marine SI engine controls on annual PM2.5 design 

values in 2020. 

2-20 
Regulatory Impact Analysis 

0 0 0 3 

Number of Counties 

>= -0.09 to -0.05 >= -0.24 to -0.10 >= -0.49 to -0.25 <= -0.50 

Legend

>= -0.04 to 0.0 553 > 0.0 0 2020cc_

Figure 2-3 Impact of Small SI and Marine SI controls on annual PM2.5 Design Values (DV) in 2020 (units are 

2-21
Table 2-5 lists the counties with projected annual PM2.5 design values that violate 

or are within 10 percent of the annual PM2.5 standard in 2020. Counties are marked with 

a “V” in the table if their projected design values are greater than or equal to 15.05 

μg/m3

. Counties are marked with an “X” in the table if their projected annual design 

values are greater than or equal to 13.55 μg/m3

, but less than 15.05 μg/m3. The counties 

marked “X” are not projected to violate the standard, but to be close to it, so the rule will 

help assure that these counties continue to meet the standard. The current design values 

are also presented in Table 2-5. Recall that we project future design values only for 

counties that have current design values, so this list is limited to those counties with 

ambient monitoring data sufficient to calculate current 3-year design values. 

Table 2-5 Counties with 2020 Projected Annual PM2.5 Design Values in Violation or 

Within 10 percent of the Annual PM2.5 Standard as a Result of the Small SI and Marine 

SI Controls 

State County 

2000­

2004 

Average 

annual 

PM2.5 

DV 

(ug/m3) 

2020 

modeling 

projections 

of 

annual 

PM2.5 DV 

2020 

Population 

Alabama Jefferson Co 18.36 V 681,549 

California Fresno Co 20.02 X 1,066,878 

California Imperial Co 14.44 V 161,555 

California Kern Co 21.77 X 876,131 

California Kings Co 18.77 X 173,390 

California Los Angeles Co 23.16 X 10,376,013 

California Merced Co 16.47 X 277,863 

California Orange Co 18.27 X 3,900,599 

California Riverside Co 27.15 X 2,252,510 

California San Bernardino Co 24.63 X 2,424,764 

California San Diego Co 15.65 V 3,863,460 

California San Joaquin Co 14.84 V 743,469 

California Stanislaus Co 16.49 V 607,766 

California Tulare Co 21.33 X 477,296 

Georgia Fulton Co 18.29 V 929,278 

Illinois Cook Co 17.06 V 5,669,479 

Illinois Madison Co 17.27 V 278,167 

Kentucky Jefferson Co 16.58 V 726,257 

Michigan Wayne Co 19.32 X 1,908,196 

Montana Lincoln Co 15.85 V 20,147 

New York New York Co 17.16 V 1,700,384 

Ohio Cuyahoga Co 18.36 V 1,326,680 

Pennsylvania Allegheny Co 20.99 X 1,242,587 

West Virginia Hancock Co 17.30 V 30,539 

2-22 
Regulatory Impact Analysis 

2.2.4 Environmental Effects of PM Pollution 

In this section we discuss some of the public welfare effects of PM and its 

precursors, including NOx, such as visibility impairment, atmospheric deposition, and 

materials damage and soiling. 

2.2.4.1 Visibility Impairment 

Visibility can be defined as the degree to which the atmosphere is transparent to 

visible light.76 Visibility impairment manifests in two principal ways: as local visibility 

impairment and as regional haze.77 Local visibility impairment may take the form of a 

localized plume, a band or layer of discoloration appearing well above the terrain as a 

result of complex local meteorological conditions. Alternatively, local visibility 

impairment may manifest as an urban haze, sometimes referred to as a “brown cloud.” 

This urban haze is largely caused by emissions from multiple sources in the urban area 

and is not typically attributable to only one nearby source or to long-range transport. The 

second type of visibility impairment, regional haze, usually results from multiple 

pollution sources spread over a large geographic region. Regional haze can impair 

visibility over large regions and across states. 

Visibility is important because it has direct significance to people’s enjoyment of 

daily activities in all parts of the country. Individuals value good visibility for the wellbeing it provides them directly, where they live and work and in places where they enjoy 

recreational opportunities. Visibility is also highly valued in significant natural areas 

such as national parks and wilderness areas, and special emphasis is given to protecting 

visibility in these areas. 

Fine particles are the major cause of reduced visibility in parts of the United 

States. To address the welfare effects of PM on visibility, EPA sets secondary PM2.5 

standards which work in conjunction with the regional haze program. The secondary 

(welfare-based) PM2.5 NAAQS is equal to the suite of primary (health-based) PM2.5 

NAAQS. The regional haze rule (64 FR 35714, July 1999) was put in place to protect the 

visibility in mandatory class I federal areas. These areas are defined in Section 162 of the 

Act as those national parks exceeding 6,000 acres, wilderness areas and memorial parks 

exceeding 5,000 acres, and all international parks which were in existence on August 7, 

1977. A list of the mandatory class I federal areas is included in Appendix 2D. Visibility 

is impaired in both PM2.5 nonattainment areas and mandatory class I federal areas. 

Control of small SI and marine SI emissions will improve visibility. The small SI 

and marine SI engines subject to this rule emit PM and PM precursors and thus contribute 

to visibility impairment. In the next sections we present current information and 

projected estimates about visibility impairment related to ambient PM2.5 levels across the 

country and visibility impairment in mandatory class I federal areas. We conclude that 

visibility will continue to be impaired in the future and the emission reductions from this 

rule will help improve visibility conditions across the country and in mandatory class I 

2-23 
federal areas. For more information on visibility see the PM AQCD as well as the 2005 

PM Staff Paper.78,79 

2.2.4.1.1 Current Visibility Impairment in PM2.5 Nonattainment Areas 

As mentioned above, the secondary PM2.5 standards were set as equal to the suite 

of primary PM2.5 standards. Almost 90 million people live in the 208 counties that are in 

nonattainment for the 1997 PM2.5 NAAQS, (see Appendix 2A for the complete list of 

current nonattainment areas). These populations, as well as large numbers of individuals 

who travel to these areas can experience visibility impairment. 

2.2.4.1.2 Current Visibility Impairment at Mandatory Class I Federal Areas 

Detailed information about current and historical visibility conditions in 

mandatory class I federal areas is summarized in the EPA Report to Congress and the 

2002 EPA Trends Report.80,81 The conclusions draw upon the Interagency Monitoring of 

Protected Visual Environments (IMPROVE) network data. One of the objectives of the 

IMPROVE monitoring network program is to provide regional haze monitoring 

representing all mandatory class I federal areas where practical. The National Park 

Service report also describes the state of national park visibility conditions and discusses 

the need for improvement.82 

The regional haze rule requires states to establish goals for each affected 

mandatory class I federal area that 1) improves visibility on the haziest days (20% most 

impaired days), 2) ensures no degradation occurs on the cleanest days (20% least 

impaired days), and 3) achieves natural background visibility levels by 2064. Although 

there have been general trends toward improved visibility, progress is still needed on the 

haziest days. Specifically, as discussed in the 2002 EPA Trends Report, without the 

effects of pollution a natural visual range in the United States is approximately 75 to 150 

km in the East and 200 to 300 km in the West. In 2001, the mean visual range for the 

worst days was 29 km in the East and 98 km in the West.83 

2.2.4.1.3 Future Visibility Impairment 

Additional emission reductions will be needed from a broad set of sources, 

including those in this action, as part of the overall strategy to achieve the visibility goals 

of the Act and the regional haze program. 

Modeling was used to project visibility conditions in 133 mandatory class I 

federal areas across the US in 2020 and 2030 as a result of the small SI and marine SI 

engine standards. The AQ modeling TSD and Section 2.3 of this RIA provide 

information on the modeling methodology. Table 2-6 below indicates the current 

monitored deciview values, the natural background levels each area is attempting to 

reach, and also the projected deciview values in 2020 and 2030 with and without the 

standards. In 2030, the greatest visibility improvement due to this rule (0.14 deciview) 

will occur at Brigantine, New Jersey. 

2-24 
Regulatory Impact Analysis 

Table 2-6 Current (2002) and Future (2020 and 2030) Projected Visibility Conditions With and 

Without Small SI and Marine SI Rule in Mandatory Class I Federal Areas (20% Worst Days) 

Class 1 Area State Baseline 

Visibility 

2020 

Base 

2020 Bond 

Rule 

2030 

Base 

2030 Bond 

Rule 

Natural 

Background 

Sipsey Wilderness AL 29.03 23.73 23.72 23.66 23.64 10.99 

Caney Creek Wilderness AR 26.36 22.05 22.03 21.92 21.89 11.58 

Upper Buffalo Wilderness AR 26.27 22.35 22.33 22.19 22.17 11.57 

Chiricahua NM AZ 13.43 13.09 13.09 13.09 13.09 7.21 

Chiricahua Wilderness AZ 13.43 13.09 13.09 13.09 13.09 7.21 

Galiuro Wilderness AZ 13.43 13.07 13.06 13.09 13.09 7.21 

Grand Canyon NP AZ 11.66 11.09 11.09 11.08 11.08 7.14 

Mazatzal Wilderness AZ 13.35 12.72 12.71 12.73 12.71 6.68 

Petrified Forest NP AZ 13.21 12.83 12.82 12.75 12.75 6.49 

Pine Mountain Wilderness AZ 13.35 12.58 12.56 12.54 12.53 6.68 

Saguaro NM AZ 14.83 14.47 14.48 14.44 14.45 6.46 

Sierra Ancha Wilderness AZ 13.67 13.20 13.20 13.15 13.14 6.59 

Sycamore Canyon 

Wilderness AZ 15.25 14.94 14.93 14.93 14.93 6.69 

Agua Tibia Wilderness CA 23.50 21.14 21.13 20.94 20.94 7.64 

Caribou Wilderness CA 14.15 13.60 13.60 13.51 13.51 7.31 

Cucamonga Wilderness CA 19.94 17.36 17.38 17.10 17.10 7.06 

Desolation Wilderness CA 12.63 12.13 12.13 12.12 12.12 6.12 

Dome Land Wilderness CA 19.43 18.34 18.34 18.11 18.11 7.46 

Emigrant Wilderness CA 17.63 17.21 17.20 17.19 17.19 7.64 

Hoover Wilderness CA 12.87 12.72 12.72 12.74 12.74 7.91 

Joshua Tree NM CA 19.62 17.93 17.97 17.71 17.72 7.19 

Lassen Volcanic NP CA 14.15 13.54 13.54 13.43 13.43 7.31 

Lava Beds NM CA 15.05 14.42 14.42 14.32 14.32 7.86 

Mokelumne Wilderness CA 12.63 12.30 12.30 12.31 12.30 6.12 

Pinnacles NM CA 18.46 17.36 17.34 17.09 17.09 7.99 

Point Reyes NS CA 22.81 21.99 21.98 21.79 21.79 15.77 

Redwood NP CA 18.45 17.86 17.86 17.79 17.78 13.91 

San Gabriel Wilderness CA 19.94 17.25 17.25 16.93 16.93 7.06 

San Gorgonio Wilderness CA 22.17 20.22 20.24 19.70 19.71 7.30 

San Jacinto Wilderness CA 22.17 19.87 19.90 19.55 19.52 7.30 

South Warner Wilderness CA 15.05 14.59 14.59 14.52 14.52 7.86 

Thousand Lakes 

Wilderness CA 14.15 13.52 13.52 13.41 13.40 7.31 

Ventana Wilderness CA 18.46 17.64 17.63 17.62 17.62 7.99 

Yosemite NP CA 17.63 17.14 17.14 17.11 17.11 7.64 

Black Canyon of the 

Gunnison NM CO 10.33 9.79 9.79 9.77 9.77 6.24 

Eagles Nest Wilderness CO 9.61 9.03 9.03 8.96 8.95 6.54 

Flat Tops Wilderness CO 9.61 9.25 9.25 9.24 9.24 6.54 

Great Sand Dunes NM CO 12.78 12.35 12.35 12.34 12.34 6.66 

2-25 
Class 1 Area State Baseline 

Visibility 

2020 

Base 

2020 Bond 

Rule 

2030 

Base 

2030 Bond 

Rule 

Natural 

Background 

La Garita Wilderness CO 10.33 9.89 9.89 9.88 9.87 6.24 

Maroon Bells-Snowmass 

Wilderness CO 9.61 9.21 9.21 9.20 9.20 6.54 

Mesa Verde NP CO 13.03 12.39 12.39 12.37 12.37 6.83 

Mount Zirkel Wilderness CO 10.52 10.05 10.05 10.04 10.03 6.44 

Rawah Wilderness CO 10.52 10.04 10.03 10.04 10.02 6.44 

Rocky Mountain NP CO 13.83 13.08 13.06 13.01 12.99 7.24 

Weminuche Wilderness CO 10.33 9.85 9.85 9.85 9.84 6.24 

West Elk Wilderness CO 9.61 9.15 9.15 9.14 9.14 6.54 

Chassahowitzka FL 26.09 21.94 21.92 21.91 21.88 11.21 

Everglades NP FL 22.30 19.77 19.76 19.94 19.91 12.15 

St. Marks FL 26.03 21.82 21.81 21.83 21.81 11.53 

Cohutta Wilderness GA 30.30 23.33 23.32 23.28 23.26 11.14 

Okefenokee GA 27.13 23.42 23.41 23.40 23.39 11.44 

Wolf Island GA 27.13 23.37 23.35 23.32 23.29 11.44 

Craters of the Moon NM ID 14.00 12.97 12.96 12.82 12.80 7.53 

Sawtooth Wilderness ID 13.78 13.63 13.63 13.63 13.63 6.43 

Mammoth Cave NP KY 31.37 25.48 25.47 25.44 25.42 11.08 

Acadia NP ME 22.89 19.77 19.75 19.81 19.78 12.43 

Moosehorn ME 21.72 18.63 18.62 18.64 18.62 12.01 

Roosevelt Campobello 

International Park ME 21.72 18.45 18.44 18.47 18.45 12.01 

Isle Royale NP MI 20.74 19.10 19.08 19.04 19.01 12.37 

Seney MI 24.16 21.72 21.70 21.66 21.63 12.65 

Voyageurs NP MN 19.27 17.58 17.56 17.43 17.41 12.06 

Hercules-Glades 

Wilderness MO 26.75 22.93 22.92 22.81 22.78 11.30 

Anaconda-Pintler 

Wilderness MT 13.41 13.14 13.13 13.11 13.11 7.43 

Bob Marshall Wilderness MT 14.48 14.13 14.12 14.08 14.07 7.74 

Cabinet Mountains 

Wilderness MT 14.09 13.54 13.53 13.46 13.44 7.53 

Gates of the Mountains 

Wilderness MT 11.29 10.91 10.91 10.87 10.86 6.45 

Medicine Lake MT 17.72 16.19 16.19 16.09 16.09 7.90 

Mission Mountains 

Wilderness MT 14.48 14.04 14.04 13.99 13.99 7.74 

Scapegoat Wilderness MT 14.48 14.16 14.15 14.12 14.11 7.74 

Selway-Bitterroot 

Wilderness MT 13.41 13.04 13.04 12.99 12.99 7.43 

UL Bend MT 15.14 14.64 14.63 14.58 14.57 8.16 

Linville Gorge Wilderness NC 28.77 22.45 22.44 22.41 22.39 11.22 

Swanquarter NC 25.49 21.15 21.11 21.15 21.10 11.94 

Lostwood ND 19.57 17.70 17.70 17.60 17.60 8.00 

Theodore Roosevelt NP ND 17.74 16.49 16.48 16.34 16.34 7.79 

2-26 
Regulatory Impact Analysis 

Class 1 Area State Baseline 

Visibility 

2020 

Base 

2020 Bond 

Rule 

2030 

Base 

2030 Bond 

Rule 

Natural 

Background 

Great Gulf Wilderness NH 22.82 19.45 19.43 19.46 19.43 11.99 

Presidential Range-Dry 

River Wilderness NH 22.82 19.45 19.43 19.46 19.43 11.99 

Brigantine NJ 29.01 24.85 24.75 24.91 24.77 12.24 

Bandelier NM NM 12.22 11.35 11.35 11.29 11.28 6.26 

Bosque del Apache NM 13.80 12.85 12.85 12.73 12.73 6.73 

Gila Wilderness NM 13.11 12.54 12.54 12.54 12.53 6.69 

Pecos Wilderness NM 10.41 9.97 9.97 9.97 9.97 6.44 

Salt Creek NM 18.03 16.59 16.58 16.52 16.52 6.81 

San Pedro Parks 

Wilderness NM 10.17 9.43 9.43 9.40 9.40 6.08 

Wheeler Peak Wilderness NM 10.41 9.88 9.88 9.87 9.87 6.44 

White Mountain 

Wilderness NM 13.70 12.88 12.89 12.87 12.86 6.86 

Jarbidge Wilderness NV 12.07 11.86 11.85 11.85 11.85 7.87 

Wichita Mountains OK 23.81 20.62 20.60 20.55 20.53 7.53 

Crater Lake NP OR 13.74 13.27 13.25 13.20 13.18 7.84 

Diamond Peak 

Wilderness OR 13.74 13.20 13.19 13.12 13.11 7.84 

Eagle Cap Wilderness OR 18.57 17.83 17.82 17.71 17.70 8.92 

Gearhart Mountain 

Wilderness OR 13.74 13.37 13.37 13.33 13.33 7.84 

Hells Canyon Wilderness OR 18.55 17.20 17.19 17.04 17.01 8.32 

Kalmiopsis Wilderness OR 15.51 14.98 14.97 14.93 14.92 9.44 

Mount Hood Wilderness OR 14.86 14.13 14.12 14.14 14.12 8.44 

Mount Jefferson 

Wilderness OR 15.33 14.77 14.76 14.76 14.75 8.79 

Mount Washington 

Wilderness OR 15.33 14.75 14.74 14.72 14.71 8.79 

Mountain Lakes 

Wilderness OR 13.74 13.24 13.23 13.17 13.16 7.84 

Strawberry Mountain 

Wilderness OR 18.57 17.73 17.72 17.60 17.59 8.92 

Three Sisters Wilderness OR 15.33 14.82 14.81 14.79 14.78 8.79 

Cape Romain SC 26.48 22.74 22.72 22.71 22.68 12.12 

Badlands NP SD 17.14 15.84 15.83 15.74 15.74 8.06 

Wind Cave NP SD 15.84 14.91 14.91 14.87 14.86 7.71 

Great Smoky Mountains 

NP TN 30.28 23.93 23.92 23.86 23.85 11.24 

Joyce-Kilmer-Slickrock 

Wilderness TN 30.28 23.43 23.42 23.37 23.35 11.24 

Big Bend NP TX 17.30 16.13 16.13 16.15 16.14 7.16 

Carlsbad Caverns NP TX 17.19 15.89 15.89 15.87 15.87 6.68 

Guadalupe Mountains NP TX 17.19 15.87 15.86 15.84 15.84 6.68 

Arches NP UT 11.24 11.11 11.11 11.03 11.01 6.43 

Bryce Canyon NP UT 11.65 11.34 11.34 11.31 11.31 6.86 

2-27 
Class 1 Area State Baseline 

Visibility 

2020 

Base 

2020 Bond 

Rule 

2030 

Base 

2030 Bond 

Rule 

Natural 

Background 

Canyonlands NP UT 11.24 10.81 10.81 10.82 10.85 6.43 

Zion NP UT 13.24 12.92 12.95 12.81 12.83 6.99 

James River Face 

Wilderness VA 29.12 23.34 23.31 23.26 23.23 11.13 

Shenandoah NP VA 29.31 22.80 22.78 22.76 22.73 11.35 

Lye Brook Wilderness VT 24.45 21.08 21.06 21.11 21.08 11.73 

Alpine Lake Wilderness WA 17.84 16.71 16.69 16.60 16.57 8.43 

Glacier Peak Wilderness WA 13.96 13.60 13.60 13.67 13.66 8.01 

Goat Rocks Wilderness WA 12.76 12.05 12.03 12.03 12.02 8.36 

Mount Adams Wilderness WA 12.76 12.01 12.00 11.97 11.96 8.36 

Mount Rainier NP WA 18.24 17.24 17.23 17.21 17.18 8.55 

North Cascades NP WA 13.96 13.57 13.57 13.67 13.66 8.01 

Olympic NP WA 16.74 15.82 15.82 15.89 15.86 8.44 

Pasayten Wilderness WA 15.23 14.84 14.84 14.81 14.81 8.26 

Dolly Sods Wilderness WV 29.04 22.35 22.34 22.33 22.31 10.39 

Otter Creek Wilderness WV 29.04 22.29 22.28 22.27 22.25 10.39 

Bridger Wilderness WY 11.12 10.80 10.80 10.79 10.78 6.58 

Fitzpatrick Wilderness WY 11.12 10.85 10.85 10.84 10.84 6.58 

Grand Teton NP WY 11.76 11.35 11.35 11.31 11.31 6.51 

North Absaroka 

Wilderness WY 11.45 11.16 11.16 11.13 11.12 6.86 

Red Rock Lakes WY 11.76 11.43 11.42 11.39 11.39 6.51 

Teton Wilderness WY 11.76 11.40 11.39 11.36 11.36 6.51 

Washakie Wilderness WY 11.45 11.17 11.16 11.14 11.14 6.86 

Yellowstone NP WY 11.76 11.38 11.37 11.34 11.33 6.51 

a

 The level of visibility impairment in an area is based on the light-extinction coefficient and a unitless 

visibility index, called a “deciview”, which is used in the valuation of visibility. The deciview metric 

provides a scale for perceived visual changes over the entire range of conditions, from clear to hazy. Under 

many scenic conditions, the average person can generally perceive a change of one deciview. The higher 

the deciview value, the worse the visibility. Thus, an improvement in visibility is a decrease in deciview 

value. 

2.2.4.2 Particulate Matter Deposition 

Particulate matter contributes to adverse effects on vegetation and ecosystems, 

and to soiling and materials damage. These welfare effects result predominately from 

exposure to excess amounts of specific chemical species, regardless of their source or 

predominant form (particle, gas or liquid). Reflecting this fact, the PM AQCD concludes 

that regardless of size fractions, particles containing nitrates and sulfates have the greatest 

potential for widespread environmental significance, while effects are also related to 

other chemical constituents found in ambient PM, such as trace metals and organics. The 

following characterizations of the nature of these welfare effects are based on the 

information contained in the PM AQCD and PM Staff Paper. 

2-28 
Regulatory Impact Analysis 

2.2.4.2.1 Deposition of Nitrates and Sulfates 

At current ambient levels, risks to vegetation from short-term exposures to dry 

deposited particulate nitrate or sulfate are low. However, when found in acid or 

acidifying deposition, such particles do have the potential to cause direct leaf injury. 

Specifically, the responses of forest trees to acid precipitation (rain, snow) include 

accelerated weathering of leaf cuticular surfaces, increased permeability of leaf surfaces 

to toxic materials, water, and disease agents; increased leaching of nutrients from foliage; 

and altered reproductive processes—all which serve to weaken trees so that they are more 

susceptible to other stresses (e.g., extreme weather, pests, pathogens). Acid deposition 

with levels of acidity associated with the leaf effects described above are currently found 

in some locations in the eastern U.S.84 Even higher concentrations of acidity can be 

present in occult depositions (e.g., fog, mist or clouds) which more frequently impacts 

higher elevations. Thus, the risk of leaf injury occurring from acid deposition in some 

areas of the eastern U.S. is high. Nitrogen deposition has also been shown to impact 

ecosystems in the western U.S. A study conducted in the Columbia River Gorge 

National Scenic Area (CRGNSA), located along a portion of the Oregon/Washington 

border, indicates that lichen communities in the CRGNSA have shifted to a higher 

proportion of nitrophilous species and the nitrogen content of lichen tissue is elevated.85 

Lichens are sensitive indicators of nitrogen deposition effects to terrestrial ecosystems 

and the lichen studies in the Columbia River Gorge clearly show that ecological effects 

from air pollution are occurring. 

Some of the most significant detrimental effects associated with excess reactive 

nitrogen deposition are those associated with a syndrome known as nitrogen saturation. 

These effects include: (1) decreased productivity, increased mortality, and/or shifts in 

plant community composition, often leading to decreased biodiversity in many natural 

habitats wherever atmospheric reactive nitrogen deposition increases significantly and 

critical thresholds are exceeded; (2) leaching of excess nitrate and associated base cations 

from soils into streams, lakes, and rivers, and mobilization of soil aluminum; and (3) 

fluctuation of ecosystem processes such as nutrient and energy cycles through changes in 

the functioning and species composition of beneficial soil organisms.86 

In the U.S. numerous forests now show severe symptoms of nitrogen saturation. 

These forests include: the northern hardwoods and mixed conifer forests in the 

Adirondack and Catskill Mountains of New York; the red spruce forests at Whitetop 

Mountain, Virginia, and Great Smoky Mountains National Park, North Carolina; mixed 

hardwood watersheds at Fernow Experimental Forest in West Virginia; American beech 

forests in Great Smoky Mountains National Park, Tennessee; mixed conifer forests and 

chaparral watersheds in southern California and the southwestern Sierra Nevada in 

Central California; the alpine tundra/subalpine conifer forests of the Colorado Front 

Range; and red alder forests in the Cascade Mountains in Washington. 

Excess nutrient inputs into aquatic ecosystems (i.e. streams, rivers, lakes, 

estuaries or oceans) either from direct atmospheric deposition, surface runoff, or leaching 

from nitrogen saturated soils into ground or surface waters can contribute to conditions of 

2-29 
severe water oxygen depletion; eutrophication and algae blooms; altered fish 

distributions, catches, and physiological states; loss of biodiversity; habitat degradation; 

and increases in the incidence of disease. 

Severe and persistent eutrophication often directly impacts human activities. For 

example, losses in the nation’s fishery resources may be directly caused by fish kills 

associated with low dissolved oxygen and toxic blooms. Declines in tourism occur when 

low dissolved oxygen causes noxious smells and floating mats of algal blooms create 

unfavorable aesthetic conditions. Risks to human health increase when the toxins from 

algal blooms accumulate in edible fish and shellfish, and when toxins become airborne, 

causing respiratory problems due to inhalation. According to a NOAA report, more than 

half of the nation’s estuaries have moderate to high expressions of at least one of these 

symptoms – an indication that eutrophication is well developed in more than half of U.S. 

estuaries. 87 

2.2.4.2.2 Deposition of Heavy Metals 

Heavy metals, including cadmium, copper, lead, chromium, mercury, nickel and 

zinc, have the greatest potential for influencing forest growth (PM AQCD, p. 4-87).88 

Investigation of trace metals near roadways and industrial facilities indicate that a 

substantial load of heavy metals can accumulate on vegetative surfaces. Copper, zinc, 

and nickel have been documented to cause direct toxicity to vegetation under field 

conditions (PM AQCD, p. 4-75). Little research has been conducted on the effects 

associated with mixtures of contaminants found in ambient PM. While metals typically 

exhibit low solubility, limiting their bioavailability and direct toxicity, chemical 

transformations of metal compounds occur in the environment, particularly in the 

presence of acidic or other oxidizing species. These chemical changes influence the 

mobility and toxicity of metals in the environment. Once taken up into plant tissue, a 

metal compound can undergo chemical changes, accumulate and be passed along to 

herbivores or can re-enter the soil and further cycle in the environment. Although there 

has been no direct evidence of a physiological association between tree injury and heavy 

metal exposures, heavy metals have been implicated because of similarities between 

metal deposition patterns and forest decline (PM AQCD, p. 4-76). This hypothesized 

relationship/correlation was further explored in high elevation forests in the northeastern 

U.S. These studies measured levels of a group of intracellular compounds found in plants 

that bind with metals and are produced by plants as a response to sublethal concentrations 

of heavy metals. These studies indicated a systematic and significant increase in 

concentrations of these compounds associated with the extent of tree injury. These data 

strongly imply that metal stress causes tree injury and contributes to forest decline in the 

northeastern United States (PM AQCD 4-76,77).89 Contamination of plant leaves by 

heavy metals can lead to elevated soil levels. Trace metals absorbed into the plant 

frequently bind to the leaf tissue, and then are lost when the leaf drops (PM AQCD, p. 4-

75). As the fallen leaves decompose, the heavy metals are transferred into the soil.90,91 

The environmental sources and cycling of mercury are currently of particular 

concern due to the bioaccumulation and biomagnification of this metal in aquatic 

2-30 
Regulatory Impact Analysis 

ecosystems and the potent toxic nature of mercury in the forms in which is it ingested by 

people and other animals. Mercury is unusual compared with other metals in that it 

largely partitions into the gas phase (in elemental form), and therefore has a longer 

residence time in the atmosphere than a metal found predominantly in the particle phase. 

This property enables mercury to travel far from the primary source before being 

deposited and accumulating in the aquatic ecosystem. The major source of mercury in the 

Great Lakes is from atmospheric deposition, accounting for approximately eighty percent 

of the mercury in Lake Michigan.92,93 Over fifty percent of the mercury in the 

Chesapeake Bay has been attributed to atmospheric deposition.94 Overall, the National 

Science and Technology Council identifies atmospheric deposition as the primary source 

of mercury to aquatic systems.95 Forty-four states have issued health advisories for the 

consumption of fish contaminated by mercury; however, most of these advisories are 

issued in areas without a mercury point source. 

Elevated levels of zinc and lead have been identified in streambed sediments, and 

these elevated levels have been correlated with population density and motor vehicle 

use.96,97 Zinc and nickel have also been identified in urban water and soils. In addition, 

platinum, palladium, and rhodium, metals found in the catalysts of modern motor 

vehicles, have been measured at elevated levels along roadsides.98 Plant uptake of 

platinum has been observed at these locations. 

2.2.4.2.3 Deposition of Polycyclic Organic Matter 

Polycyclic organic matter (POM) is a byproduct of incomplete combustion and 

consists of organic compounds with more than one benzene ring and a boiling point 

greater than or equal to 100 degrees centigrade.99 Polycyclic aromatic hydrocarbons 

(PAHs) are a class of POM that contains compounds which are known or suspected 

carcinogens. 

Major sources of PAHs include mobile sources. PAHs in the environment may be 

present as a gas or adsorbed onto airborne particulate matter. Since the majority of PAHs 

are adsorbed onto particles less than 1.0 μm in diameter, long range transport is possible. 

However, studies have shown that PAH compounds adsorbed onto diesel exhaust 

particulate and exposed to ozone have half lives of 0.5 to 1.0 hours.100 

Since PAHs are insoluble, the compounds generally are particle reactive and 

accumulate in sediments. Atmospheric deposition of particles is believed to be the major 

source of PAHs to the sediments of Lake Michigan.101,102 Analyses of PAH deposition in 

Chesapeake and Galveston Bay indicate that dry deposition and gas exchange from the 

atmosphere to the surface water predominate.103,104 Sediment concentrations of PAHs are 

high enough in some segments of Tampa Bay to pose an environmental health threat. 

EPA funded a study to better characterize the sources and loading rates for PAHs into 

Tampa Bay.105 PAHs that enter a water body through gas exchange likely partition into 

organic rich particles and can be biologically recycled, while dry deposition of aerosols 

containing PAHs tend to be more resistant to biological recycling.106 Thus, dry 

deposition is likely the main pathway for PAH concentrations in sediments while 

gas/water exchange at the surface may lead to PAH distribution into the food web, 

2-31 
leading to increased health risk concerns. 

Trends in PAH deposition levels are difficult to discern because of highly variable 

ambient air concentrations, lack of consistency in monitoring methods, and the 

significant influence of local sources on deposition levels.107 Van Metre et al. noted PAH 

concentrations in urban reservoir sediments have increased by 200-300% over the last 

forty years and correlate with increases in automobile use.108 

Cousins et al. estimate that more than ninety percent of semi-volatile organic 

compound (SVOC) emissions in the United Kingdom deposit on soil.109 An analysis of 

PAH concentrations near a Czechoslovakian roadway indicated that concentrations were 

thirty times greater than background.110 

2.2.4.2.4 Materials Damage and Soiling 

The effects of the deposition of atmospheric pollution, including ambient PM, on 

materials are related to both physical damage and impaired aesthetic qualities. The 

deposition of PM (especially sulfates and nitrates) can physically affect materials, adding 

to the effects of natural weathering processes, by potentially promoting or accelerating 

the corrosion of metals, by degrading paints, and by deteriorating building materials such 

as concrete and limestone. Only chemically active fine particles or hygroscopic coarse 

particles contribute to these physical effects. In addition, the deposition of ambient PM 

can reduce the aesthetic appeal of buildings and culturally important articles through 

soiling. Particles consisting primarily of carbonaceous compounds cause soiling of 

commonly used building materials and culturally important items such as statues and 

works of art. 

2.3 Air Quality Modeling Methodology 

In this section we present information on the air quality modeling, including the 

model domain and modeling inputs. Further discussion of the modeling methodology, 

including evaluations of model performance, is included in the Air Quality Modeling 

Technical Support Document (AQM TSD).111 

2.3.1 Air Quality Modeling Overview 

A national scale air quality modeling analysis was performed to estimate future 

year 8-hour ozone concentrations, annual PM2.5 concentrations, and visibility levels. 

These projections were used as inputs to the calculation of expected benefits from the 

small SI and marine SI emissions controls considered in this assessment. The 2002-based 

CMAQ modeling platform was used as the tool for the air quality modeling of future 

baseline emissions and control scenarios. It should be noted that the 2002-based 

modeling platform has recently been finalized and the 2001-based modeling platform was 

used as the tool for the air quality modeling performed for the proposal. In the next 

paragraph we discuss some of the differences between the 2001-based platform used for 

the proposal and the 2002-based platform used for this final rule. 

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Regulatory Impact Analysis 

The 2002-based modeling platform includes a number of updates and 

improvements to data and tools compared to the 2001-based platform that was used for 

the proposal modeling. For the final rule modeling we used the new 2002 National 

Emissions Inventory along with updated versions of the models used to project future 

emissions from electric generating units (EGUs) and onroad and nonroad vehicles. The 

proposal modeling was based on the 2001 National Emissions Inventory. The new 

platform also includes 2002 meteorology and more recent ambient design values which 

were used as the starting point for projecting future air quality. For proposal, we used 

meteorology for 2001 for modeling the East and 2002 for modeling the West. The 

updates to CMAQ between proposal and final include (1) an in-cloud sulfate chemistry 

module that accounts for the nonlinear sensitivity of sulfate formation to varying pH; (2) 

improved vertical convective mixing; (3) heterogeneous reaction involving nitrate 

formation; (4) an updated gas-phase chemistry mechanism, Carbon Bond 2005 (CB05); 

and (5) an aqueous chemistry mechanism that provides a comprehensive simulation of 

aerosol precursor oxidants. 

The CMAQ model is a three-dimensional grid-based Eulerian air quality model 

designed to estimate the formation and fate of oxidant precursors, primary and secondary 

particulate matter concentrations and deposition over regional and urban spatial scales 

(e.g., over the contiguous U.S.).112,113,114 Consideration of the different processes that 

affect primary (directly emitted) and secondary (formed by atmospheric processes) PM at 

the regional scale in different locations is fundamental to understanding and assessing the 

effects of pollution control measures that affect PM, ozone and deposition of pollutants to 

the surface. In addition to the CMAQ model, the modeling platform includes the 

emissions, meteorology, and initial/boundary condition data which are inputs to this 

model. 

The CMAQ model was peer-reviewed in 2003 for EPA as reported in “Peer 

Review of CMAQ Model”.115 The latest version of CMAQ (Version 4.6.1) was 

employed for this modeling analysis. This version reflects updates, as mentioned above, 

in a number of areas to improve the underlying science which include (1) use of a stateof-the science inorganic and organic aerosol module, (2) an in-cloud sulfate chemistry 

module that accounts for the nonlinear sensitivity of sulfate formation to varying pH, (3) 

improved vertical convective mixing, (4) heterogeneous reaction involving nitrate 

formation and (5) an updated Carbon Bond 05 (CB05) gas-phase chemistry mechanism 

and aqueous chemistry mechanism that provides a comprehensive simulation of aerosol 

precursor oxidants. 

2.3.2 Model Domain and Configuration 

The CMAQ modeling domain encompasses all of the lower 48 States and portions 

of Canada and Mexico. The modeling domain is made up of a large continental U.S. 36 

km grid and two 12 km grids (an Eastern US and a Western US domain), as shown in 

Figure 2-4. The modeling domain contains 14 vertical layers with the top of the 

modeling domain at about 16,200 meters, or 100 millibars (mb). 

2-33 
Figure 2-4. Map of the CMAQ modeling domain 

2.3.3 Model Inputs 

The key inputs to the CMAQ model include emissions from anthropogenic and 

biogenic sources, meteorological data, and initial and boundary conditions. The CMAQ 

meteorological input files were derived from a simulation of the Pennsylvania State 

University / National Center for Atmospheric Research Mesoscale Model116 for the entire 

year of 2002. This model, commonly referred to as MM5, is a limited-area, 

nonhydrostatic, terrain-following system that solves for the full set of physical and 

thermodynamic equations which govern atmospheric motions. The meteorology for the 

national 36 km grid and the 12 km Eastern U.S. grid were developed by EPA and are 

described in more detail within the AQM TSD. The meteorology for the 12 km Western 

U.S. grid was developed by the Western Regional Air Partnership (WRAP) Regional 

Planning Organization. The meteorological outputs from MM5 were processed to create 

model-ready inputs for CMAQ using the Meteorology-Chemistry Interface Processor 

(MCIP) version 3.1 to derive the specific inputs to CMAQ, for example: horizontal wind 

components (i.e., speed and direction), temperature, moisture, vertical diffusion rates, and 

rainfall rates for each grid cell in each vertical layer.117 

The lateral boundary and initial species concentrations are provided by a threedimensional global atmospheric chemistry model, the GEOS-CHEM model.118 The 

global GEOS-CHEM model simulates atmospheric chemical and physical processes 

driven by assimilated meteorological observations from the NASA’s Goddard Earth 

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Regulatory Impact Analysis 

Observing System (GEOS). This model was run for 2002 with a grid resolution of 2 

degree x 2.5 degree (latitude-longitude) and 20 vertical layers. The predictions were used 

to provide one-way dynamic boundary conditions at three-hour intervals and an initial 

concentration field for the 36 km CMAQ simulations. The future base conditions from 

the 36 km coarse grid modeling were used as the initial/boundary state for all subsequent 

12 km finer grid modeling. 

The emissions inputs used for the 2002 base year and each of the future year base 

cases and control scenarios are summarized in Chapter 3 of this RIA. 

2.3.4 CMAQ Evaluation 

An operational model performance evaluation for PM2.5 and its related speciated 

components (e.g., sulfate, nitrate, elemental carbon, organic carbon, etc.) was conducted 

using the 2002 data in order to estimate the ability of the CMAQ modeling system to 

replicate base year concentrations. In summary, model performance statistics were 

calculated for observed/predicted pairs of daily/monthly/seasonal/annual concentrations. 

Statistics were generated for the following geographic groupings: domain wide, Eastern 

vs. Western (divided along the 100th meridian), and each Regional Planning 

Organization (RPO) region.K The “acceptability” of model performance was judged by 

comparing our results to those found in recent regional PM2.5 model applications for 

other, non-EPA studies.L Overall, the performance for the 2002 modeling platform is 

within the range of these other applications. A detailed summary of the 2002 CMAQ 

model performance evaluation is available within the AQM TSD. 

2.3.5 Model Simulation Scenarios 

As part of our analysis for this rulemaking the CMAQ modeling system was used 

to calculate 8-hour ozone concentrations, annual PM2.5 concentrations, and visibility 

estimates for each of the following emissions scenarios: 

2002 base year 

2020 base line projection 

2020 base line projection with small SI and marine SI controls 

2030 base line projection 

2030 base line projection with small SI and marine SI controls 

K Regional Planning Organization regions include: Mid-Atlantic/Northeast Visibility 

Union (MANE-VU), Midwest Regional Planning Organization – Lake Michigan Air 

Directors Consortium (MWRPO-LADCO), Visibility Improvement State and Tribal 

Association of the Southeast (VISTAS), Central States Regional Air Partnership 

(CENRAP), and Western Regional Air Partnership (WRAP). 

L These other modeling studies represent a wide range of modeling analyses which cover 

various models, model configurations, domains, years and/or episodes, chemical 

mechanisms, and aerosol modules. 

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It should be noted that the emission control scenarios used in the air quality and 

benefits modeling are slightly different than the emission control program being 

finalized. The differences reflect further refinements of the regulatory program since we 

performed the air quality modeling for this rule. Chapter 3 of this RIA describes the 

changes in the inputs and resulting emission inventories between the preliminary 

assumptions used for the air quality modeling and the final regulatory scenario. These 

refinements to the program would not significantly change the results summarized here or 

our conclusions drawn from this analysis. 

We use the predictions from the model in a relative sense by combining the 2002 

base-year predictions with predictions from each future-year scenario and applying these 

modeled ratios to ambient air quality observations to estimate annual PM2.5 

concentrations, 8-hour ozone concentrations, and visibility levels for each of the 2020 

and 2030 scenarios. The ambient air quality observations are average conditions, on a 

site by site basis, for a period centered around the model base year (i.e., 2000-2004). 

After completing this process, we then calculated the effect of changes in PM, ozone and 

visibility air quality metrics resulting from this rulemaking on the health and welfare 

impact functions of the benefits analysis. 

The projected annual PM2.5 design values were calculated using the Speciated 

Modeled Attainment Test (SMAT) approach. The SMAT uses an Federal Reference 

Method FRM mass construction methodology that results in reduced nitrates (relative to 

the amount measured by routine speciation networks), higher mass associated with 

sulfates (reflecting water included in FRM measurements), and a measure of organic 

carbonaceous mass that is derived from the difference between measured PM2.5 and its 

non-carbon components. This characterization of PM2.5 mass also reflects crustal 

material and other minor constituents. The resulting characterization provides a complete 

mass balance. It does not have any unknown mass that is sometimes presented as the 

difference between measured PM2.5 mass and the characterized chemical components 

derived from routine speciation measurements. However, the assumption that all mass 

difference is organic carbon has not been validated in many areas of the US. The SMAT 

methodology uses the following PM2.5 species components: sulfates, nitrates, ammonium, 

organic carbon mass, elemental carbon, crustal, water, and blank mass (a fixed value of 

0.5 μg/m3

). More complete details of the SMAT procedures can be found in the report 

"Procedures for Estimating Future PM2.5 Values for the CAIR Final Rule by Application 

of the (Revised) Speciated Modeled Attainment Test (SMAT)".119 For this latest 

analysis, several datasets and techniques were updated. These changes are fully 

described within the AQM TSD. The projected 8-hour ozone design values were 

calculated using the approach identified in EPA's guidance on air quality modeling 

attainment demonstrations. 

2.3.6 Visibility Modeling Methodology 

The modeling platform described in this section was also used to project changes 

in visibility. The estimate of visibility benefits was based on the projected improvement 

in annual average visibility at mandatory class I federal areas. There are 156 Federally 

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Regulatory Impact Analysis 

mandated Class I areas which, under the Regional Haze Rule, are required to achieve 

natural background visibility levels by 2064. These mandatory class I federal areas are 

mostly national parks, national monuments, and wilderness areas. There are currently 

116 Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring 

sites (representing all 156 mandatory class I federal areas) collecting ambient PM2.5 data 

at mandatory class I federal areas, but not all of these sites have complete data for 2002. 

For this analysis, we quantified visibility improvement at the 133 mandatory class I 

federal areas which have complete IMPROVE ambient data for 2002 or are represented 

by IMPROVE monitors with complete data.M 

Visibility impairment is quantified in extinction units. Visibility degradation is 

directly proportional to decreases in light transmittal in the atmosphere. Scattering and 

absorption by both gases and particles decrease light transmittance. To quantify changes 

in visibility, our analysis computes a light-extinction coefficient (bext) and visual range. 

The light extinction coefficient is based on the work of Sisler, which shows the total 

fraction of light that is decreased per unit distance. This coefficient accounts for the 

scattering and absorption of light by both particles and gases and accounts for the higher 

extinction efficiency of fine particles compared to coarse particles. Fine particles with 

significant light-extinction efficiencies include sulfates, nitrates, organic carbon, 

elemental carbon, and soil.120 

Visual range is a measure of visibility that is inversely related to the extinction 

coefficient. Visual range can be defined as the maximum distance at which one can 

identify a black object against the horizon sky. Visual range (in units of kilometers) can 

be calculated from bext using the formula: Visual Range (km) = 3912/bext (bext units are 

inverse megameters [Mm-1]) 

The future year visibility impairment was calculated using a methodology which applies 

modeling results in a relative sense similar to the Speciated Modeled Attainment Test 

(SMAT). 

In calculating visibility impairment, the extinction coefficient is made up of 

individual component species (sulfate, nitrate, organics, etc). The predicted change in 

visibility is calculated as the percent change in the extinction coefficient for each of the 

PM species (on a daily average basis). The individual daily species extinction 

coefficients are summed to get a daily total extinction value. The daily extinction 

coefficients are converted to visual range and then averaged across all days. In this way, 

we can calculate annual average extinction and visual range at each IMPROVE site. 

Subtracting the annual average control case visual range from the base case visual range 

gives a projected improvement in visual range (in km) at each mandatory class I federal 

area. This serves as the visibility input for the benefits analysis (See Chapter X). 

M There are 100 IMPROVE sites with complete data for 2002. Many of these sites collect data that is 

“representative” of other nearby unmonitored mandatory class I federal areas. There are a total of 133 

mandatory class I federal areas that are represented by the 100 sites. The matching of sites to monitors is 

taken from “Guidance for Tracking Progress Under the Regional Haze Rule”. 

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For visibility calculations, we are continuing to use the IMPROVE program 

species definitions and visibility formulas which are recommended in the modeling 

guidance.121 Each IMPROVE site has measurements of PM2.5 species and therefore we 

do not need to estimate the species fractions in the same way that we did for FRM sites 

(using interpolation techniques and other assumptions concerning volatilization of 

species). 

2.4 Air Toxics 

Small SI and Marine SI emissions contribute to ambient levels of air toxics 

known or suspected as human or animal carcinogens, or that have noncancer health 

effects. The population experiences an elevated risk of cancer and other noncancer health 

effects from exposure to air toxics.122 These compounds include, but are not limited to, 

benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein, polycyclic organic matter 

(POM), and naphthalene. These compounds, except acetaldehyde, were identified as 

national or regional risk drivers in the 1999 National-Scale Air Toxics Assessment 

(NATA) and have significant inventory contributions from mobile sources. 

Table2-7 Mobile Source Inventory Contribution to 1999 Emissions of NATA Risk Driversa 

1999 NATA Risk Driver Percent of Emissions 

Attributable to All Mobile 

Sources 

Percent of Emissions 

Attributable to Non-road 

Sources 

Benzene 68% 19% 

1,3-Butadiene 58% 17% 

Formaldehyde 47% 20% 

Acrolein 25% 11% 

Polycyclic organic matter (POM)b

 5% 2% 

Naphthalene 27% 6% 

Diesel PM and Diesel exhaust organic 

gases 

100% 62% 

a

 This table is generated from data contained in the pollutant specific Microsoft Access database files found 

in the County-Level Emission Summaries section of the 1999 NATA webpage 

(http://www.epa.gov/ttn/atw/nata1999/tables.html). b This POM inventory includes the 15 POM compounds: benzo[b]fluoranthene, benz[a]anthracene, 

indeno(1,2,3-c,d)pyrene, benzo[k]fluoranthene, chrysene, benzo[a]pyrene, dibenz(a,h)anthracene, anthracene, 

pyrene, benzo(g,h,i)perylene, fluoranthene, acenaphthylene, phenanthrene, fluorine, and acenaphthene. 

According to NATA for 1999, mobile sources were responsible for 44 percent of 

outdoor toxic emissions and almost 50 percent of the cancer risk. Benzene is the largest 

contributor to cancer risk of all 133 pollutants quantitatively assessed in the 1999 NATA 

and mobile sources were responsible for 68 percent of benzene emissions in 1999. In 

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Regulatory Impact Analysis 

response, EPA has recently finalized vehicle and fuel controls that address this public 

health risk.N 

People are exposed to toxics from spark-ignition engines as a result of operating 

these engines and from intrusion into the home of emissions that occur in residential 

attached garages. A study of aldehyde exposures among lawn and garden equipment 

operators found formaldehyde and acetaldehyde exposure concentrations, during 

approximately 30 to 120 minutes of engine use, that were one to two orders of magnitude 

greater than those measured at an upwind monitor.123 The study also reported measurable 

concentrations of transition metals emitted from most test engines, in addition to high 

organic carbon concentrations in PM2.5 samples. Analyses of organic material emitted 

from hand-held engines have detected PAHs and other compounds, suggesting that 

exposures to hand-held engine emissions are similar in composition to those found in 

motor vehicle-affected environments, such as near major roadways.124 Numerous studies 

have reported elevated benzene concentrations in residential attached garages. 125,126,127 

These studies indicate the potential for elevated exposures as a result of the use and 

storage of small spark-ignition engines. 

Noncancer health effects can result from chronic,O subchronic,P or acuteQ 

inhalation exposures to air toxics, and include neurological, cardiovascular, liver, kidney, 

and respiratory effects as well as effects on the immune and reproductive systems. 

According to the 1999 NATA, nearly the entire U.S. population was exposed to an 

average concentration of air toxics that has the potential for adverse noncancer 

respiratory health effects. This will continue to be the case in 2030, even though toxics 

concentrations will be lower. Mobile sources were responsible for 74 percent of the 

noncancer (respiratory) risk from outdoor air toxics in 1999. The majority of this risk 

was from exposure to acrolein. The confidence in the RfC for acrolein is medium and 

confidence in NATA estimates of population noncancer hazard from ambient exposure to 

this pollutant is low.128,129 

The NATA modeling framework has a number of limitations which prevent its 

use as the sole basis for setting regulatory standards. These limitations and uncertainties 

are discussed on the 1999 NATA website.130 Even so, this modeling framework is very 

N U.S. EPA (2007) Control of Hazardous Air Pollutants from Mobile Sources. 72 FR 8428; February 26, 

2007. 

O Chronic exposure is defined in the glossary of the Integrated Risk Information (IRIS) database 

(http://www.epa.gov/iris) as repeated exposure by the oral, dermal, or inhalation route for more than 

approximately 10% of the life span in humans (more than approximately 90 days to 2 years in typically 

used laboratory animal species). 

P

 Defined in the IRIS database as repeated exposure by the oral, dermal, or inhalation route for more than 

30 days, up to approximately 10% of the life span in humans (more than 30 days up to approximately 90 

days in typically used laboratory animal species).. 

Q Defined in the IRIS database as exposure by the oral, dermal, or inhalation route for 24 hours or less. 

2-39 
useful in identifying air toxic pollutants and sources of greatest concern, setting 

regulatory priorities, and informing the decision making process. 

Benzene: The EPA’s IRIS database lists benzene as a known human carcinogen 

(causing leukemia) by all routes of exposure, and concludes that exposure is associated 

with additional health effects, including genetic changes in both humans and animals and 

increased proliferation of bone marrow cells in mice.131,132,133 EPA states in its IRIS 

database that data indicate a causal relationship between benzene exposure and acute 

lymphocytic leukemia and suggest a relationship between benzene exposure and chronic 

non-lymphocytic leukemia and chronic lymphocytic leukemia. The International Agency 

for Research on Carcinogens (IARC) has determined that benzene is a human carcinogen 

and the U.S. Department of Health and Human Services (DHHS) has characterized 

benzene as a known human carcinogen.134,135 

A number of adverse noncancer health effects including blood disorders, such as 

preleukemia and aplastic anemia, have also been associated with long-term exposure to 

benzene.136,137 The most sensitive noncancer effect observed in humans, based on current 

data, is the depression of the absolute lymphocyte count in blood.138,139 In addition, 

recent work, including studies sponsored by the Health Effects Institute (HEI), provides 

evidence that biochemical responses are occurring at lower levels of benzene exposure 

than previously known.140,141,142,143 EPA’s IRIS program has not yet evaluated these new 

data. 

1,3-Butadiene: EPA has characterized 1,3-butadiene as carcinogenic to humans 

by inhalation.144,145 The IARC has determined that 1,3-butadiene is a human carcinogen 

and the U.S. DHHS has characterized 1,3-butadiene as a known human carcinogen.146,147 

There are numerous studies consistently demonstrating that 1,3-butadiene is metabolized 

into genotoxic metabolites by experimental animals and humans. The specific 

mechanisms of 1,3-butadiene-induced carcinogenesis are unknown; however, the 

scientific evidence strongly suggests that the carcinogenic effects are mediated by 

genotoxic metabolites. Animal data suggest that females may be more sensitive than 

males for cancer effects associated with 1,3-butadiene exposure; there are insufficient 

data in humans from which to draw conclusions about sensitive subpopulations. 1,3-

butadiene also causes a variety of reproductive and developmental effects in mice; no 

human data on these effects are available. The most sensitive effect was ovarian atrophy 

observed in a lifetime bioassay of female mice.148 

Formaldehyde: Since 1987, EPA has classified formaldehyde as a probable 

human carcinogen based on evidence in humans and in rats, mice, hamsters, and 

monkeys.149 EPA is currently reviewing recently published epidemiological data. For 

instance, research conducted by the National Cancer Institute (NCI) found an increased 

risk of nasopharyngeal cancer and lymphohematopoietic malignancies such as leukemia 

among workers exposed to formaldehyde.150,151 NCI is currently performing an update of 

these studies. A recent National Institute of Occupational Safety and Health (NIOSH) 

study of garment workers also found increased risk of death due to leukemia among 

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Regulatory Impact Analysis 

workers exposed to formaldehyde.152 Extended follow-up of a cohort of British chemical 

workers did not find evidence of an increase in nasopharyngeal or lymphohematopoietic 

cancers, but a continuing statistically significant excess in lung cancers was reported.153 

In the past 15 years there has been substantial research on the inhalation 

dosimetry for formaldehyde in rodents and primates by the CIIT Centers for Health 

Research (formerly the Chemical Industry Institute of Toxicology), with a focus on use of 

rodent data for refinement of the quantitative cancer dose-response assessment.154,155,156 

CIIT’s risk assessment of formaldehyde incorporated mechanistic and dosimetric 

information on formaldehyde. 

Based on the developments of the last decade, in 2004, the working group of the 

International Agency for Research on Cancer (IARC) concluded that formaldehyde is 

carcinogenic to humans (Group 1), on the basis of sufficient evidence in humans and 

sufficient evidence in experimental animals - a higher classification than previous IARC 

evaluations. After reviewing the currently available epidemiological evidence, the IARC 

(2006) characterized the human evidence for formaldehyde carcinogenicity as 

“sufficient,” based upon the data on nasopharyngeal cancers; the epidemiologic evidence 

on leukemia was characterized as “strong.”157 EPA is reviewing the recent work cited 

above from the NCI and NIOSH, as well as the analysis by the CIIT Centers for Health 

Research and other studies, as part of a reassessment of the human hazard and doseresponse associated with formaldehyde. 

Formaldehyde exposure also causes a range of noncancer health effects, including 

irritation of the eyes (burning and watering of the eyes), nose and throat. Effects from 

repeated exposure in humans include respiratory tract irritation, chronic bronchitis and 

nasal epithelial lesions such as metaplasia and loss of cilia. Animal studies suggest that 

formaldehyde may also cause airway inflammation – including eosinophil infiltration into 

the airways. There are several studies that suggest that formaldehyde may increase the 

risk of asthma – particularly in the young.158,159 

Acetaldehyde: Acetaldehyde is classified in EPA’s IRIS database as a probable 

human carcinogen, based on nasal tumors in rats, and is considered toxic by the 

inhalation, oral, and intravenous routes.160 Acetaldehyde is reasonably anticipated to be a 

human carcinogen by the U.S. DHHS in the 11th Report on Carcinogens and is classified 

as possibly carcinogenic to humans (Group 2B) by the IARC.161,162 EPA is currently 

conducting a reassessment of cancer risk from inhalation exposure to acetaldehyde. 

The primary noncancer effects of exposure to acetaldehyde vapors include 

irritation of the eyes, skin, and respiratory tract.163 In short-term (4 week) rat studies, 

degeneration of olfactory epithelium was observed at various concentration levels of 

acetaldehyde exposure.164,165 Data from these studies were used by EPA to develop an 

inhalation reference concentration. Some asthmatics have been shown to be a sensitive 

subpopulation to decrements in functional expiratory volume (FEV1 test) and 

bronchoconstriction upon acetaldehyde inhalation.166 The agency is currently conducting 

a reassessment of the health hazards from inhalation exposure to acetaldehyde. 

2-41 
Acrolein: EPA determined in 2003 that the human carcinogenic potential of 

acrolein could not be determined because the available data were inadequate. No 

information was available on the carcinogenic effects of acrolein in humans and the 

animal data provided inadequate evidence of carcinogenicity.167 The IARC determined 

in 1995 that acrolein was not classifiable as to its carcinogenicity in humans.168 

Acrolein is extremely acrid and irritating to humans when inhaled, with acute 

exposure resulting in upper respiratory tract irritation, mucus hypersecretion and 

congestion. Levels considerably lower than 1 ppm (2.3 mg/m3) elicit subjective 

complaints of eye and nasal irritation and a decrease in the respiratory rate.169,170 Lesions 

to the lungs and upper respiratory tract of rats, rabbits, and hamsters have been observed 

after subchronic exposure to acrolein. Based on animal data, individuals with 

compromised respiratory function (e.g., emphysema, asthma) are expected to be at 

increased risk of developing adverse responses to strong respiratory irritants such as 

acrolein. This was demonstrated in mice with allergic airway-disease by comparison to 

non-diseased mice in a study of the acute respiratory irritant effects of acrolein.171 

EPA is currently in the process of conducting an assessment of acute exposure 

effects for acrolein. The intense irritancy of this carbonyl has been demonstrated during 

controlled tests in human subjects, who suffer intolerable eye and nasal mucosal sensory 

reactions within minutes of exposure.172 

Polycyclic Organic Matter (POM): POM is generally defined as a large class of 

organic compounds which have multiple benzene rings and a boiling point greater than 

100 degrees Celsius. Many of the compounds included in the class of compounds known 

as POM are classified by EPA as probable human carcinogens based on animal data. 

One of these compounds, naphthalene, is discussed separately below. Polycyclic 

aromatic hydrocarbons (PAHs) are a subset of POM that contain only hydrogen and 

carbon atoms. A number of PAHs are known or suspected carcinogens. Recent studies 

have found that maternal exposures to PAHs (a subclass of POM) in a population of 

pregnant women were associated with several adverse birth outcomes, including low 

birth weight and reduced length at birth, as well as impaired cognitive development at 

age three.173,174 EPA has not yet evaluated these recent studies. 

Naphthalene: Naphthalene is found in small quantities in gasoline and diesel 

fuels. Naphthalene emissions have been measured in larger quantities in both gasoline 

and diesel exhaust compared with evaporative emissions from mobile sources, indicating 

it is primarily a product of combustion. EPA recently released an external review draft of 

a reassessment of the inhalation carcinogenicity of naphthalene based on a number of 

recent animal carcinogenicity studies.175 The draft reassessment recently completed 

external peer review.176 Based on external peer review comments received to date, 

additional analyses are being undertaken. This external review draft does not represent 

official agency opinion and was released solely for the purposes of external peer review 

and public comment. Once EPA evaluates public and peer reviewer comments, the 

document will be revised. The National Toxicology Program listed naphthalene as 

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Regulatory Impact Analysis 

"reasonably anticipated to be a human carcinogen" in 2004 on the basis of bioassays 

reporting clear evidence of carcinogenicity in rats and some evidence of carcinogenicity 

in mice.177 California EPA has released a new risk assessment for naphthalene, and the 

IARC has reevaluated naphthalene and re-classified it as Group 2B: possibly 

carcinogenic to humans.178 Naphthalene also causes a number of chronic non-cancer 

effects in animals, including abnormal cell changes and growth in respiratory and nasal 

tissues.179 

The small SI and marine SI standards will reduce air toxics emitted from these 

engines, vessels and equipment, thereby helping to mitigate some of the adverse health 

effects associated with their operation. The assumption that toxic reductions track 

reductions in HC are supported by results from numerous test programs, including recent 

testing on small nonroad gasoline engines with and without controls.180 

2.5 Carbon Monoxide 

Unlike many gases, CO is odorless, colorless, tasteless, and nonirritating. Carbon 

monoxide results from incomplete combustion of fuel and is emitted directly from 

vehicle tailpipes. Incomplete combustion is most likely to occur at low air-to-fuel ratios 

in the engine. These conditions are common during vehicle starting when air supply is 

restricted (“choked”), when vehicles are not tuned properly, and at high altitude, where 

“thin” air effectively reduces the amount of oxygen available for combustion (except in 

engines that are designed or adjusted to compensate for altitude). High concentrations of 

CO generally occur in areas with elevated mobile-source emissions. Carbon monoxide 

emissions increase dramatically in cold weather. This is because engines need more fuel 

to start at cold temperatures and because some emission control devices (such as oxygen 

sensors and catalytic converters) operate less efficiently when they are cold. Also, 

nighttime inversion conditions are more frequent in the colder months of the year. This is 

due to the enhanced stability in the atmospheric boundary layer, which inhibits vertical 

mixing of emissions from the surface. 

2.5.1 Health Effects of CO Pollution 

We are relying on the data and conclusions in the EPA Air Quality Criteria 

Document for CO (CO Criteria Document), which was published in 2000, regarding the 

health effects associated with CO exposure.R181 Carbon monoxide enters the bloodstream 

through the lungs and forms carboxyhemoglobin (COHb), a compound that inhibits the 

blood’s capacity to carry oxygen to organs and tissues.182,183 Carbon monoxide has long 

been known to have substantial adverse effects on human health, including toxic effects 

on blood and tissues, and effects on organ functions. Although there are effective 

compensatory increases in blood flow to the brain, at some concentrations of COHb, 

somewhere above 20 percent, these compensations fail to maintain sufficient oxygen 

delivery, and metabolism declines.184 The subsequent hypoxia in brain tissue then 

R The NAAQS review process is underway for CO and the CO Integrated Science 

Assessment is scheduled to be completed in 2010. 

2-43 
produces behavioral effects, including decrements in continuous performance and 

reaction time.185 

Carbon monoxide has been linked to increased risk for people with heart disease, 

reduced visual perception, cognitive functions and aerobic capacity, and possible fetal 

effects.186 Persons with heart disease are especially sensitive to carbon monoxide 

poisoning and may experience chest pain if they breathe the gas while exercising.187 

Infants, elderly persons, and individuals with respiratory diseases are also particularly 

sensitive. Carbon monoxide can affect healthy individuals, impairing exercise capacity, 

visual perception, manual dexterity, learning functions, and ability to perform complex 

tasks.188 

Several epidemiological studies have shown a link between CO and premature 

morbidity (including angina, congestive heart failure, and other cardiovascular diseases). 

Several studies in the United States and Canada have also reported an association 

between ambient CO exposures and frequency of cardiovascular hospital admissions, 

especially for congestive heart failure (CHF). An association between ambient CO 

exposure and mortality has also been reported in epidemiological studies, though not as 

consistently or specifically as with CHF admissions. EPA reviewed these studies as part 

of the CO Criteria Document review process and noted the possibility that the average 

ambient CO levels used as exposure indices in the epidemiology studies may be 

surrogates for ambient air mixes impacted by combustion sources and/or other 

constituent toxic components of such mixes. More research will be needed to better 

clarify CO’s role.189 

As noted above, CO has been linked to numerous health effects. In addition to 

health effects from chronic exposure to ambient CO levels, acute exposures to higher 

levels are also a problem. Acute exposures to CO are discussed further in Section 2.6. 

2.5.2 Attainment and Maintenance of the CO NAAQS 

On July 3, 1995 EPA made a finding that small land-based spark-ignition engines 

cause or contribute to CO nonattainment (60 FR 34581, July 3, 1995). Marine sparkignition engines, which have relatively high per engine CO emissions, can also be a 

source of CO emissions in CO nonattainment areas. In the preamble for this proposed 

rule EPA makes a finding that recreational marine engines and vessels cause or 

contribute to CO nonattainment and we provide information showing CO emissions from 

spark-ignition marine engines and vessels in the CO nonattainment areas in 2005. Sparkignition marine engines and vessels contribute to CO nonattainment in more than one of 

the CO nonattainment areas. 

A nonattainment area is defined in the Clean Air Act (CAA) as an area that is 

violating an ambient standard or is contributing to a nearby area that is violating the 

standard. EPA has designated nonattainment areas for the CO NAAQS by calculating air 

quality design values and considering other factors.S 

S

 The full details involved in calculating a CO design value are given in 40 CFR Part 50.8. 

2-44 
Regulatory Impact Analysis 

There are two CO NAAQS. The 8-hour average CO NAAQS is 9 ppm, not to be 

exceeded more than once per year, and the 1-hour average CO NAAQS is 35 ppm, not to 

be exceeded more than once per year. As of March 12, 2008, there are approximately 

850 thousand people living in 4 areas (which include 5 counties) that are designated as 

nonattainment for CO, see Table 2-8. The emission reductions in this rule will help areas 

to attain and maintain the CO NAAQS. 

Table 2-8: Classified Carbon Monoxide Nonattainment Areas as of March 2008a 

Area Classification Population (1000s) 

Las Vegas, NV serious 479 

El Paso, TX moderate <= 12.7 ppm 62 

Reno, NV moderate <= 12.7 ppm 179 

Total 719.5 

a

 This table does not include Salem, OR which is an unclassified CO nonattainment area. 

In addition to the CO nonattainment areas, there are areas that have not been 

designated as nonattainment where air quality monitoring may indicate a need for CO 

control. For example, areas like Birmingham, AL and Calexico, CA have not been 

designated as nonattainment although monitors in these areas have recorded multiple 

exceedances since 1995.190 

There are also almost 69 million people living in CO maintenance areas, see 

Table 2-9.T Carbon monoxide maintenance areas may remain at risk for high CO 

episodes especially in geographic areas with unusually challenging meteorological and 

topographical conditions and in areas with high population growth and increasing vehicle 

miles traveled. 

Table 2-9: Carbon Monoxide Maintenance Areas as of March 2008 

Number of Areas Number of Counties Population (1000s) 

Serious 6 15 20,496,077 

Moderate > 12.7ppm 4 19 17,575,606 

Moderate <= 12.7ppm 30 62 23,371,653 

Unclassified 33 38 7,480,907 

Total 73 127 68,924,243 

A 2003 NAS report found that in geographical areas that have achieved 

attainment of the NAAQS, it might still be possible for ambient concentrations of CO to 

sporadically exceed the standard under unfavorable conditions such as strong winter 

T

 The CO nonattainment and maintenance areas are listed in Appendix 2E to this RIA. 

2-45
inversions. Areas like Alaska are prone to winter inversions due to their topographic and 

meteorological conditions. The report further suggests that additional reductions in CO 

are prudent to further reduce the risk of violations in regions with problematic 

topography and temporal variability in meteorology.191 The reductions in CO emissions 

from this rule will assist areas in maintaining the CO standard. 

As discussed in the preamble, Small SI engines and equipment and Marine SI 

engines and vessels do contribute to CO nonattainment. The CO emission benefits from 

this rule will help states in their strategy to attain the CO NAAQS. Maintenance of the 

CO NAAQS is also challenging and many areas will be able to use the emissions 

reductions from this rule to assist in maintaining the CO NAAQS into the future. 

2.6 Acute Exposure to Air Pollutants 

Emissions from Small SI engines and equipment and Marine SI engines and 

vessels contribute to ambient concentrations of ozone, CO, air toxics and PM and acute 

exposures to air toxics, CO and PM. The standards being finalized in this action can help 

reduce acute exposures to emissions from Marine SI engines and vessels and Small SI 

engines and equipment. 

2.6.1 Exposure to CO from Marine SI Engines and Vessels 

In recent years, a substantial number of CO poisonings and deaths have occurred 

on and around recreational boats across the nation. The actual number of deaths 

attributable to CO poisoning while boating is difficult to estimate because CO-related 

deaths in the water may be labeled as drowning. An interagency team consisting of the 

National Park Service, the U.S. Department of Interior, and the National Institute for 

Occupational Safety and Health maintains a record of published CO-related fatal and 

nonfatal poisonings.192 Between 1984 and 2004, 113 CO-related deaths and 458 nonfatal CO poisonings have been identified based on hospital records, press accounts, and 

other information. Deaths have been attributed to exhaust from both onboard generators 

and propulsion engines. Houseboats, cabin cruisers, and ski boats are the most common 

types of boats associated with CO poisoning cases. These incidents have prompted other 

federal agencies, including the United States Coast Guard and National Park Service, to 

issue advisory statements and other interventions to boaters to avoid activities that could 

lead to excessive CO exposure.193 

CO concentrations can be extremely elevated within several meters of the exhaust 

port. Engineers and industrial hygienists from CDC/NIOSH and other state and federal 

agencies have conducted field studies of CO concentrations on and around houseboats. 

In one study of houseboat concentrations, CO concentrations immediately at the point of 

generator exhaust discharge on one houseboat averaged 0.5% (5,000 ppm), and ranged 

from 0.0% to 1.28% (12,800 ppm).194 With both propulsion and generators running, 

time-averaged concentrations on the swim deck were 0.2 - 169 ppm at different locations 

on one boat's swim platform, 17-570 ppm on another's, and 0-108 on another. Other 

studies also show the potential for high concentrations with extreme peaks in CO 

2-46 
Regulatory Impact Analysis 

concentrations in locations where boaters and swimmers can be exposed during typical 

boating activities, such as standing on a swim deck or swimming near a boat. 

2.6.2 Exposure to CO and PM from Small SI Engines and Equipment 

A large segment of the population uses small, gasoline-powered SI lawn and 

garden equipment on a regular basis. Emissions from many of the Small SI engines 

powering this equipment may lead to elevated air pollution exposures for a number of 

gaseous and particulate compounds, especially for individuals such as landscapers, whose 

occupations require the daily use of these engines and equipment. 

Emission studies with lawn and garden equipment suggest a potential for high 

exposures during the Small SI engine operation.195,196 Studies investigating air pollutant 

exposures during small engine use did report elevated personal exposure measurements 

related to lawn and garden equipment use.197,198 Bunger et al. reported elevated CO 

personal measurements related to chainsaw use, with short-term concentrations exceeding 

400 ppm for certain cutting activities. This study evaluated personal exposures during 

the use of uncontrolled chainsaws. Baldauf at al. evaluated the use of lawnmowers, 

chainsaws and string trimmers meeting US EPA Phase 2 standards. In this study, shortterm exposures during lawnmower and chainsaw use exceeded 120 ppm of CO, while 

string trimmer use resulted in some short-term exposures approaching 100 ppm of CO. 

This study also indicated that short-term PM2.5 exposures could exceed 100 Fg/m3

. 

Pollutant exposures were highly dependent on the operator’s orientation to the engine and 

wind direction, as well as the activities being conducted. 

These studies indicate that emissions from some lawn and garden equipment 

meeting EPA's current Phase 2 standards may contribute to elevated exposures to certain 

pollutants. The potential for elevated exposure to CO and PM2.5 for operators of Small SI 

engines and equipment will be reduced by this rule. 

1

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Washington, DC, EPA/600/R-05/004aF-cF, 2006. Error! Main Document Only.This document is 

contained in Docket Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

2

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Washington, DC, EPA/600/R-05/004aF-cF, 2006. Error! Main Document Only.This document is 

contained in Docket Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

3

 U.S. EPA, Review of the National Ambient Air Quality Standards for Ozone: Policy Assessment of 

Scientific and Technical Information, OAQPS Staff Paper, Washington, DC, EPA-452/R-07-003, January 

2-47 
2007. Error! Main Document Only.This document is available in Docket EPA-HQ-OAR-2004-

0008. 

4

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5

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9

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10 U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. EPA, 

Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket Identification 

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11 U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. EPA, 

Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket Identification 

EPA-HQ-OAR-2004-0008-0455 to 0457. 

12 Devlin, R. B.; McDonnell, W. F.; Mann, R.; Becker, S.; House, D. E.; Schreinemachers, D.; Koren, H. S. 

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14 Koren, H. S.; Devlin, R. B.; Graham, D. E.; Mann, R.; McGee, M. P.; Horstman, D. H.; Kozumbo, W. J.; 

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normal humans. Am. Rev. Respir. Dis. 143:1353-1358. 

16 U.S. EPA (1996). Air Quality Criteria for Ozone and Related Photochemical Oxidants, EPA600-P-93-

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Regulatory Impact Analysis 

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Arch. Environ. Health 48: 33-46. 

20 U.S. EPA, Review of the National Ambient Air Quality Standards for Ozone: Policy Assessment of 

Scientific and Technical Information, OAQPS Staff Paper, Washington, DC, EPA-452/R-07-003, January 

2007. This document is available in Docket EPA-HQ-OAR-2004-0008. 

21 U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. EPA, 

Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket Identification 

EPA-HQ-OAR-2004-0008-0455 to 0457. 

22 U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. EPA, 

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23 Avol, E. L.; Trim, S. C.; Little, D. E.; Spier, C. E.; Smith, M. N.; Peng, R.-C.; Linn, W. S.; Hackney, J. 

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30 U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. EPA, 

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2-49 
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34 AQ modeling TSD (EPA Doc #) 

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Regulatory Impact Analysis 

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2-51 
61 U.S. EPA (2005) Review of the National Ambient Air Quality Standard for Particulate Matter: Policy 

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Villareal, M.; Khurana Hershey, G.K.; Grinshpun, S.A. (2007) A comparison of proximity and land use 

regression traffic exposure models and wheezing in infants. Environ Health Perspect 115: 278-84. 

74 Morgenstern, V.; Zutavern, A.; Cyrys, J.; Brockow, I.; Gehring, U.; Koletzko, S.; Bauer, C.P.; Reinhart, 

D; Wichmann, H-E.; Heinrich, J. (2007) Respiratory health and individual estimated expousure to trafficrelated air pollutant in a cohort of young children. Occupational and Environmental Medicine 64: 8-16. 

75 Franco Suglia, S.; Gryparis, A.; Wright, R.O.; Schwartz, J.; Wright, R.J. (2007) Association of black 

carbon with cognition among children in a prospective birth cohort study. American Journal of 

Epidemiology 167: 280-286. 

2-52 
Regulatory Impact Analysis 

76 National Research Council, 1993. Protecting Visibility in National Parks and Wilderness Areas. 

National Academy of Sciences Committee on Haze in National Parks and Wilderness Areas. National 

Academy Press, Washington, DC. This book is available electronically at 

http://www.nap.edu/books/0309048443/html/ and is available in Docket EPA-HQ-OAR-2004-0008. 

77 U.S. EPA , National Ambient Air Quality Standards for Particulate Matter; Proposed Rule; January 17, 

2006, Vol71 p 2676. Error! Main Document Only.This document is available in Docket EPAHQ-OAR-2004-0008-0466. This information is available electronically at: http://epa.gov/fedrgstr/EPAAIR/2006/January/Day-17/a177.pdf 

78 U.S. EPA (2004) Air Quality Criteria for Particulate Matter (Oct 2004), Volume I Document No. 

EPA600/P-99/002aF and Volume II Document No. EPA600/P-99/002bF. This document is available in 

Docket EPA-HQ-OAR-2004-0008. 

79 U.S. EPA (2005) Review of the National Ambient Air Quality Standard for Particulate Matter: Policy 

Assessment of Scientific and Technical Information, OAQPS Staff Paper. EPA-452/R-05-005. This 

document is available in Docket EPA-HQ-OAR-2004-0008. 

80 U.S. EPA. 1993. Effects of the 1990 Clean Air Act Amendments on Visibility in Class I Areas: An EPA 

Report to Congress. EPA452-R-93-014. Error! Main Document Only.This document is available 

in Docket EPA-HQ-OAR-2004-0008-0483. 

81 U.S. EPA (2002) Latest Findings on National Air Quality – 2002 Status and Trends. EPA 454/K-03-001. 

Error! Main Document Only.This document is available in Docket EPA-HQ-OAR-2004-0008-

0482. 

82 National Park Service. Air Quality in the National Parks, Second edition. NPS, Air Resources Division. 

D 2266. September 2002. Error! Main Document Only.This document is available in Docket 

EPA-HQ-OAR-2004-0008-0481. 

83 U.S. EPA (2002) Latest Findings on National Air Quality – 2002 Status and Trends. EPA 454/K-03-001. 

This document is available in Docket EPA-HQ-OAR-2004-0008-0482. 

84 Environmental Protection Agency (2003). Response of Surface Water Chemistry to the Clean Air Act 

Amendments of 1990. National Health and Environmental Effects Research Laboratory, Office of Research 

and Development, U.S. Environmental Protection Agency. Research Triangle Park, NC. EPA 620/R– 

03/001. 

85 Fenn, M.E. and Blubaugh, T.J. (2005) Winter Deposition of Nitrogen and Sulfur in the Eastern Columbia 

River Gorge National Scenic Area, USDA Forest Service. 

86 Galloway, J. N.; Cowling, E. B. (2002). Reactive nitrogen and the world: 200 years of change. Ambio 

31: 64–71. 

87 Bricker, Suzanne B., et al., National Estuarine Eutrophication Assessment, Effects of Nutrient 

Enrichment in the Nation’s Estuaries, National Ocean Service, National Oceanic and Atmospheric 

Administration, September, 1999. 

88 Smith, W.H. 1991. “Air pollution and Forest Damage.” Chemical Engineering News, 69(45): 30-43. 

89 Gawel, J.E.; Ahner, B.A.; Friedland, A.J.; and Morel, F.M.M. 1996. “Role for heavy metals in forest 

decline indicated by phytochelatin measurements.” Nature, 381: 64-65. 

2-53 
90 Cotrufo, M.F.; DeSanto, A.V.; Alfani, A.; et al. 1995. “Effects of urban heavy metal pollution on organic 

matter decomposition in Quercus ilix L. woods.” Environmental Pollution, 89: 81-87. 

91 Niklinska, M.; Laskowski, R.; Maryanski, M. 1998. “Effect of heavy metals and storage time on two 

types of forest litter: basal respiration rate and exchangeable metals.” Ecotoxicological Environmental 

Safety, 41: 8-18. 

92 Mason, R.P. and Sullivan, K.A. 1997. “Mercury in Lake Michigan.” Environmental Science & 

Technology, 31: 942-947. (from Delta Report “Atmospheric deposition of toxics to the Great Lakes”). 

93 Landis, M.S. and Keeler, G.J. 2002. “Atmospheric mercury deposition to Lake Michigan during the Lake 

Michigan Mass Balance Study.” Environmental Science & Technology, 21: 4518-24. 

94 U.S. EPA. 2000. EPA453/R-00-005, “Deposition of Air Pollutants to the Great Waters: Third Report to 

Congress,” Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina. 

Error! Main Document Only.This document is available in Docket EPA-HQ-OAR-2004-0008. 

95 NSTC 1999 

96 Callender, E. and Rice, K.C. 2000. “The Urban Environmental Gradient: Anthropogenic Influences on 

the Spatial and Temporal Distributions of Lead and Zinc in Sediments.” Environmental Science & 

Technology, 34: 232-238. 

97 Rice, K.C. 1999. “Trace Element Concentrations in Streambed Sediment Across the Conterminous 

United States.” Environmental Science & Technology, 33: 2499-2504. 

98 Ely, JC; Neal, CR; Kulpa, CF; et al. 2001. “Implications of Platinum-Group Element Accumulation 

along U.S. Roads from Catalytic-Converter Attrition.” Environ. Sci. Technol. 35: 3816-3822. 

99 U.S. EPA. 1998. EPA454/R-98-014, “Locating and Estimating Air Emissions from Sources of 

Polycyclic Organic Matter,” Office of Air Quality Planning and Standards, Research Triangle Park, North 

Carolina. Error! Main Document Only.This document is available in Docket EPA-HQ-OAR2004-0008. 

100 U.S. EPA. 1998. EPA454/R-98-014, “Locating and Estimating Air Emissions from Sources of 

Polycyclic Organic Matter,” Office of Air Quality Planning and Standards, Research Triangle Park, North 

Carolina. Error! Main Document Only.This document is available in Docket EPA-HQ-OAR2004-0008. 

101 Simcik, M.F.; Eisenreich, S.J.; Golden, K.A.; et al. 1996. “Atmospheric Loading of Polycyclic Aromatic 

Hydrocarbons to Lake Michigan as Recorded in the Sediments.” Environmental Science and Technology, 

30: 3039-3046. 

102 Simcik, M.F.; Eisenreich, S.J.; and Lioy, P.J. 1999. “Source apportionment and source/sink relationship 

of PAHs in the coastal atmosphere of Chicago and Lake Michigan.” Atmospheric Environment, 33: 5071-

5079. 

103 Arzayus, K.M.; Dickhut, R.M.; and Canuel, E.A. 2001. “Fate of Atmospherically Deposited Polycyclic 

Aromatic Hydrocarbons (PAHs) in Chesapeake Bay.” Environmental Science & Technology, 35, 2178-

2183. 

104 Park, J.S.; Wade, T.L.; and Sweet, S. 2001. “Atmospheric distribution of polycyclic aromatic 

hydrocarbons and deposition to Galveston Bay, Texas, USA.” Atmospheric Environment, 35: 3241-3249. 

2-54 
Regulatory Impact Analysis 

105 Poor, N.; Tremblay, R.; Kay, H.; et al. 2002. “Atmospheric concentrations and dry deposition rates of 

polycyclic aromatic hydrocarbons (PAHs) for Tampa Bay, Florida, USA.” Atmospheric Environment 38: 

6005-6015. 

106 Arzayus, K.M.; Dickhut, R.M.; and Canuel, E.A. 2001. “Fate of Atmospherically Deposited Polycyclic 

Aromatic Hydrocarbons (PAHs) in Chesapeake Bay.” Environmental Science & Technology, 35, 2178-

2183. 

107 U.S. EPA. 2000. EPA453/R-00-005, “Deposition of Air Pollutants to the Great Waters: Third Report to 

Congress,” Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina. This 

document is available in Docket EPA-HQ-OAR-2004-0008. 

108 Van Metre, P.C.; Mahler, B.J.; and Furlong, E.T. 2000. “Urban Sprawl Leaves its PAH Signature.” 

Environmental Science & Technology, 34: 4064-4070. 

109 Cousins, I.T.; Beck, A.J.; and Jones, K.C. 1999. “A review of the processes involved in the exchange of 

semi-volatile organic compounds across the air-soil interface.” The Science of the Total Environment, 228: 

5-24. 

110 Tuhackova, J. et al. (2001) Hydrocarbon deposition and soil microflora as affected by highway traffic. 

Environmental Pollution, 113: 255-262. 

111 U.S. EPA, Technical Support Document for the Final Small SI/Marine SI Rule: Air Quality Modeling, 

Research Triangle Park, NC 

112 U.S. EPA, Byun, D.W., and Ching, J.K.S., Eds, 1999. Science algorithms of EPA Models-3 Community 

Multiscale Air Quality (CMAQ modeling system, EPA/600/R-99/030, Office of Research and 

Development). 

113 Byun, D.W., and Schere, K.L., 2006. Review of the Governing Equations, Computational Algorithms, 

and Other Components of the Models-3 Community Multiscale Air Quality (CMAQ) Modeling System, J. 

Applied Mechanics Reviews, 59 (2), 51-77. 

114 Dennis, R.L., Byun, D.W., Novak, J.H., Galluppi, K.J., Coats, C.J., and Vouk, M.A., 1996. The next 

generation of integrated air quality modeling: EPA’s Models-3, Atmospheric Environment, 30, 1925-1938. 

115 Amar, P., Bornstein, R., Feldman, H., Jeffries, H., Steyn, D., Yamartino, R., Zhang, Y., 2004. Final 

Report Summary: December 2003 Peer Review of the CMAQ Model. p. 7. 

116 Grell, G., J. Dudhia, and D. Stauffer, 1994: A Description of the Fifth-Generation Penn State/NCAR 

Mesoscale Model (MM5), NCAR/TN-398+STR., 138 pp, National Center for Atmospheric Research, 

Boulder CO. 

117 U.S. Environmental Protection Agency, Byun, D.W., and Ching, J.K.S., Eds, 1999. Science algorithms 

of EPA Models-3 Community Multiscale Air Quality (CMAQ) modeling system, EPA/600/R-99/030, 

Office of Research and Development). Please also see: http://www.cmascenter.org/ 

118 Yantosca, B., 2004. GEOS-CHEMv7-01-02 User’s Guide, Atmospheric Chemistry Modeling Group, 

Harvard University, Cambridge, MA, October 15, 2004. 

119 U.S. EPA, (2004), “Procedures for Estimating Future PM2.5 Values for the CAIR Final Rule by 

Application of the (Revised) Speciated Modeled Attainment Test (SMAT)- Updated 11/8/04”. 

120 Sisler 1996 

2-55 
121 U.S. EPA, Guidance on the Use of Models and Other Analyses For Demonstrating Attainment of Air 

Quality Goals for Ozone, PM2.5, and Regional Haze; EPA-454/B-07-002; Research Triangle Park, NC; 

April 2007. 

122 U. S. EPA. 1999 National-Scale Air Toxics Assessment. 

http://www.epa.gov/ttn/atw/nata1999/risksum.html 

123 Baldauf, R.; Fortune, C.; Weinstein, J.; Wheeler, M.; Blanchard, F. (2006) Air contaminant exposures 

during the operation of lawn and garden equipment. J Exposure Sci & Environ Epidemiol 16: 362-370. 

124 Volckens, J.; Olson, D.A.; Hays, M.D. (2008) Carbonaceous species emitted from handheld two-stroke 

engines. Atmos Environ 42: 1239-1248. 

125 Isbell, M.; Ricker, J.; Gordian, M.E.; Duff, L.K. (1999) Use of biomarkers in an indoor air study: lack 

of correlation between aromatic VOCs with respective urinary biomarkers. Sci Total Environ 241: 151-

159. 

126 Batterman, S.; Jia, C.; Hatzivasilis, G. (2007) Migration of volatile organic compounds from attached 

garages to residences: a major exposure source. Environ Res 104: 224-240. 

127 Philips, M.L.; Esmen, N.A.; Hall, T.A.; Lynch, R. (2005) Determinants of exposure to volatile organic 

compounds in four Oklahoma cities. J Exposure Anal Environ Epidemiol 15: 35-46. 

128 U.S. EPA (2003) Integrated Risk Information System File of Acrolein. National Center for 

Environmental Assessment, Office of Research and Development, Washington, D.C. 2003. This material 

is available electronically at http://www.epa.gov/iris/subst/0364.htm. 

129 U.S. EPA (2006) National-Scale Air Toxics Assessment for 1999. This material is available 

electronically at http://www.epa.gov/ttn/atw/nata1999/risksum.html. 

130 U.S. EPA (2006) National-Scale Air Toxics Assessment for 1999. 

http://www.epa.gov/ttn/atw/nata1999. 

131 U.S. EPA. 2000. Integrated Risk Information System File for Benzene. This material is available 

electronically at: http://www.epa.gov/iris/subst/0276.htm. 

132 International Agency for Research on Cancer, IARC monographs on the evaluation of carcinogenic risk 

of chemicals to humans, Volume 29, Some industrial chemicals and dyestuffs, International Agency for 

Research on Cancer, World Health Organization, Lyon, France, p. 345-389, 1982. 

133 Irons, R.D.; Stillman, W.S.; Colagiovanni, D.B.; Henry, V.A. (1992) Synergistic action of the benzene 

metabolite hydroquinone on myelopoietic stimulating activity of granulocyte/macrophage colonystimulating factor in vitro, Proc. Natl. Acad. Sci. 89:3691-3695. 

134 International Agency for Research on Cancer (IARC). 1987. Monographs on the evaluation of 

carcinogenic risk of chemicals to humans, Volume 29, Supplement 7, Some industrial chemicals and 

dyestuffs, World Health Organization, Lyon, France. 

135 U.S. Department of Health and Human Services National Toxicology Program 11th Report on 

Carcinogens available at: http://ntp.niehs.nih.gov/go/16183. 

136 Aksoy, M. (1989). Hematotoxicity and carcinogenicity of benzene. Environ. Health Perspect. 82: 

193-197. 

2-56 
Regulatory Impact Analysis 

137 Goldstein, B.D. (1988). Benzene toxicity. Occupational medicine. State of the Art Reviews. 3: 541-

554. 

138 Rothman, N., G.L. Li, M. Dosemeci, W.E. Bechtold, G.E. Marti, Y.Z. Wang, M. Linet, L.Q. Xi, W. Lu, 

M.T. Smith, N. Titenko-Holland, L.P. Zhang, W. Blot, S.N. Yin, and R.B. Hayes (1996) Hematotoxicity 

among Chinese workers heavily exposed to benzene. Am. J. Ind. Med. 29: 236-246. 

139 U.S. EPA 2002 Toxicological Review of Benzene (Noncancer Effects). Environmental Protection 

Agency, Integrated Risk Information System (IRIS), Research and Development, National Center for 

Environmental Assessment, Washington DC. This material is available electronically at 

http://www.epa.gov/iris/subst/0276.htm. 

140 Qu, O.; Shore, R.; Li, G.; Jin, X.; Chen, C.L.; Cohen, B.; Melikian, A.; Eastmond, D.; Rappaport, S.; Li, 

H.; Rupa, D.; Suramaya, R.; Songnian, W.; Huifant, Y.; Meng, M.; Winnik, M.; Kwok, E.; Li, Y.; Mu, 

R.; Xu, B.; Zhang, X.; Li, K. (2003). HEI Report 115, Validation & Evaluation of Biomarkers in Workers 

Exposed to Benzene in China. 

141 Qu, Q., R. Shore, G. Li, X. Jin, L.C. Chen, B. Cohen, et al. (2002). Hematological changes among 

Chinese workers with a broad range of benzene exposures. Am. J. Industr. Med. 42: 275-285. 

142 Lan, Qing, Zhang, L., Li, G., Vermeulen, R., et al. (2004). Hematotoxically in Workers Exposed to 

Low Levels of Benzene. Science 306: 1774-1776. 

143 Turtletaub, K.W. and Mani, C. (2003). Benzene metabolism in rodents at doses relevant to human 

exposure from Urban Air. Research Reports Health Effect Inst. Report No.113. 

144 U.S. EPA. 2002. Health Assessment of 1,3-Butadiene. Office of Research and Development, National 

Center for Environmental Assessment, Washington Office, Washington, DC. Report No. EPA600-P-98

001F. This document is available electronically at http://www.epa.gov/iris/supdocs/buta-sup.pdf. 

145 U.S. EPA. 2002 “Full IRIS Summary for 1,3-butadiene (CASRN 106-99-0)” Environmental Protection 

Agency, Integrated Risk Information System (IRIS), Research and Development, National Center for 

Environmental Assessment, Washington, DC http://www.epa.gov/iris/subst/0139.htm. 

146 International Agency for Research on Cancer (IARC) (1999) Monographs on the evaluation of 

carcinogenic risk of chemicals to humans, Volume 71, Re-evaluation of some organic chemicals, hydrazine 

and hydrogen peroxide and Volume 97 (in preparation), World Health Organization, Lyon, France. 

147 U.S. Department of Health and Human Services National Toxicology Program 11th Report on 

Carcinogens available at: http://ntp.niehs.nih.gov/go/16183. 

148 Bevan, C.; Stadler, J.C.; Elliot, G.S.; et al. (1996) Subchronic toxicity of 4-vinylcyclohexene in rats and 

mice by inhalation. Fundam. Appl. Toxicol. 32:1-10. 

149 U.S. EPA. 1987. Assessment of Health Risks to Garment Workers and Certain Home Residents from 

Exposure to Formaldehyde, Office of Pesticides and Toxic Substances, April 1987. 

150 Hauptmann, M..; Lubin, J. H.; Stewart, P. A.; Hayes, R. B.; Blair, A. 2003. Mortality from 

lymphohematopoetic malignancies among workers in formaldehyde industries. Journal of the National 

Cancer Institute 95: 1615-1623. 

151 Hauptmann, M..; Lubin, J. H.; Stewart, P. A.; Hayes, R. B.; Blair, A. 2004. Mortality from solid 

cancers among workers in formaldehyde industries. American Journal of Epidemiology 159: 1117-1130. 

-

2-57 
152 Pinkerton, L. E. 2004. Mortality among a cohort of garment workers exposed to formaldehyde: an 

update. Occup. Environ. Med. 61: 193-200. 

153 Coggon, D, EC Harris, J Poole, KT Palmer. 2003. Extended follow-up of a cohort of British chemical 

workers exposed to formaldehyde. J National Cancer Inst. 95:1608-1615. 

154 Conolly, RB, JS Kimbell, D Janszen, PM Schlosser, D Kalisak, J Preston, and FJ Miller. 2003. 

Biologically motivated computational modeling of formaldehyde carcinogenicity in the F344 rat. Tox Sci 

75: 432-447. 

155 Conolly, RB, JS Kimbell, D Janszen, PM Schlosser, D Kalisak, J Preston, and FJ Miller. 2004. Human 

respiratory tract cancer risks of inhaled formaldehyde: Dose-response predictions derived from 

biologically-motivated computational modeling of a combined rodent and human dataset. Tox Sci 82: 279-

296. 

156 Chemical Industry Institute of Toxicology (CIIT).1999. Formaldehyde: Hazard characterization and 

dose-response assessment for carcinogenicity by the route of inhalation. CIIT, September 28, 1999. 

Research Triangle Park, NC. 

157 International Agency for Research on Cancer (2006) Formaldehyde, 2-Butoxyethanol and 1-tertButoxypropan-2-ol. Monographs Volume 88. World Health Organization, Lyon, France. 

158 Agency for Toxic Substances and Disease Registry (ATSDR). 1999. Toxicological profile for 

Formaldehyde. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service. 

http://www.atsdr.cdc.gov/toxprofiles/tp111.html 

159 WHO (2002) Concise International Chemical Assessment Document 40: Formaldehyde. Published 

under the joint sponsorship of the United Nations Environment Programme, the International Labour 

Organization, and the World Health Organization, and produced within the framework of the InterOrganization Programme for the Sound Management of Chemicals. Geneva. 

160 U.S. EPA (1988). Integrated Risk Information System File of Acetaldehyde. Research and 

Development, National Center for Environmental Assessment, Washington, DC. This material is available 

electronically at http://www.epa.gov/iris/subst/0290.htm. 

161 U.S. Department of Health and Human Services National Toxicology Program 11th Report on 

Carcinogens available at: http://ntp.niehs.nih.gov/go/16183. 

162 International Agency for Research on Cancer (IARC). 1999. Re-evaluation of some organic chemicals, 

hydrazine, and hydrogen peroxide. IARC Monographs on the Evaluation of Carcinogenic Risk of 

Chemical to Humans, Vol 71. Lyon, France. 

163 U.S. EPA (1988). Integrated Risk Information System File of Acetaldehyde. This material is available 

electronically at http://www.epa.gov/iris/subst/0290.htm. 

164 U.S. EPA. 2003. Integrated Risk Information System File of Acrolein. Research and Development, 

National Center for Environmental Assessment, Washington, DC. This material is available electronically 

at http://www.epa.gov/iris/subst/0364.htm. 

165 Appleman, L.M., R.A. Woutersen, and V.J. Feron. (1982). Inhalation toxicity of acetaldehyde in rats. I. 

Acute and subacute studies. Toxicology. 23: 293-297. 

2-58 
Regulatory Impact Analysis 

166 Myou, S.; Fujimura, M.; Nishi K.; Ohka, T.; and Matsuda, T. (1993) Aerosolized acetaldehyde induces 

histamine-mediated bronchoconstriction in asthmatics. Am. Rev. Respir.Dis.148(4 Pt 1): 940-943. 

167 Integrated Risk Information System File of Acrolein. Research and Development, National Center for 

Environmental Assessment, Washington, DC. This material is available at 

http://www.epa.gov/iris/subst/0364.htm 

168 International Agency for Research on Cancer (IARC). 1995. Monographs on the evaluation of 

carcinogenic risk of chemicals to humans, Volume 63, Dry cleaning, some chlorinated solvents and other 

industrial chemicals, World Health Organization, Lyon, France. 

169 Weber-Tschopp, A; Fischer, T; Gierer, R; et al. (1977) Experimentelle reizwirkungen von Acrolein auf 

den Menschen. Int Arch Occup Environ Hlth 40(2):117-130. In German 

170 Sim, VM; Pattle, RE. (1957) Effect of possible smog irritants on human subjects. J Am Med Assoc 

165(15):1908-1913. 

171 Morris JB, Symanowicz PT, Olsen JE, et al. 2003. Immediate sensory nerve-mediated respiratory 

responses to irritants in healthy and allergic airway-diseased mice. J Appl Physiol 94(4):1563-1571. 

172 Sim VM, Pattle RE. Effect of possible smog irritants on human subjects JAMA165: 1980-2010, 1957. 

173 Perera, F.P.; Rauh, V.; Tsai, W-Y.; et al. (2002) Effect of transplacental exposure to environmental 

pollutants on birth outcomes in a multiethnic population. Environ Health Perspect. 111: 201-205. 

174 Perera, F.P.; Rauh, V.; Whyatt, R.M.; Tsai, W.Y.; Tang, D.; Diaz, D.; Hoepner, L.; Barr, D.; Tu, Y.H.; 

Camann, D.; Kinney, P. (2006) Effect of prenatal exposure to airborne polycyclic aromatic hydrocarbons 

on neurodevelopment in the first 3 years of life among inner-city children. Environ Health Perspect 114: 

1287-1292. 

175 U. S. EPA. 2004. Toxicological Review of Naphthalene (Reassessment of the Inhalation Cancer Risk), 

Environmental Protection Agency, Integrated Risk Information System, Research and Development, 

National Center for Environmental Assessment, Washington, DC. This material is available electronically 

at http://www.epa.gov/iris/subst/0436.htm. 

176 Oak Ridge Institute for Science and Education. (2004). External Peer Review for the IRIS 

Reassessment of the Inhalation Carcinogenicity of Naphthalene. August 2004. 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=84403 

177 National Toxicology Program (NTP). (2004). 11th Report on Carcinogens. Public Health Service, U.S. 

Department of Health and Human Services, Research Triangle Park, NC. Available from: http://ntp

server.niehs.nih.gov. 

178 International Agency for Research on Cancer (IARC). (2002). Monographs on the Evaluation of the 

Carcinogenic Risk of Chemicals for Humans. Vol. 82. Lyon, France. 

179 U. S. EPA. 1998. Toxicological Review of Naphthalene, Environmental Protection Agency, Integrated 

Risk Information System, Research and Development, National Center for Environmental Assessment, 

Washington, DC. This material is available electronically at http://www.epa.gov/iris/subst/0436.htm 

180 US EPA (2004) Characterization of Emissions from Small, Hand-Held,In-Use 2-Cycle Engines Internal 

Report, EPA/600/X-04/191. 

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181 U.S. EPA (2000). Air Quality Criteria for Carbon Monoxide. EPA600-P-99-001F. June 1, 2000. U.S. 

Environmental Protection Agency, Office of Research and Development, National Center for 

Environmental Assessment, Washington, D.C. This document is available online at 

http://www.epa.gov/ncea/pdfs/coaqcd.pdf. A copy of this document is available in Docket Identification 

EPA-HQ-OAR-2004-0008-0050. 

182 U.S. EPA (2000). Air Quality Criteria for Carbon Monoxide. EPA600-P-99-001F. June 1, 2000. U.S. 

Environmental Protection Agency, Office of Research and Development, National Center for 

Environmental Assessment, Washington, D.C. This document is available online at 

http://www.epa.gov/ncea/pdfs/coaqcd.pdf. A copy of this document is available in Docket Identification 

EPA-HQ-OAR-2004-0008-0050. 

183 Coburn, R.F. (1979) Mechanisms of carbon monoxide toxicity. Prev. Med. 8:310-322. 

184 Helfaer, M.A., and Traystman, R.J. (1996) Cerebrovascular effects of carbon monoxide. In: Carbon 

Monoxide (Penney, D.G., ed). Boca Raton, CRC Press, 69-86. 

185 Benignus, V.A. (1994) Behavioral effects of carbon monoxide: meta analyses and extrapolations. J. 

Appl. Physiol. 76:1310-1316. 

186 U.S. EPA (2000). Air Quality Criteria for Carbon Monoxide. EPA600-P-99-001F. June 1, 2000. U.S. 

Environmental Protection Agency, Office of Research and Development, National Center for 

Environmental Assessment, Washington, D.C. This document is available online at 

http://www.epa.gov/ncea/pdfs/coaqcd.pdf. A copy of this document is available in Docket Identification 

EPA-HQ-OAR-2004-0008-0050. 

187 U.S. EPA (2000). Air Quality Criteria for Carbon Monoxide. EPA600-P-99-001F. June 1, 2000. U.S. 

Environmental Protection Agency, Office of Research and Development, National Center for 

Environmental Assessment, Washington, D.C. This document is available online at 

http://www.epa.gov/ncea/pdfs/coaqcd.pdf. A copy of this document is available in Docket Identification 

EPA-HQ-OAR-2004-0008-0050. 

188 U.S. EPA (2000). Air Quality Criteria for Carbon Monoxide. EPA600-P-99-001F. June 1, 2000. U.S. 

Environmental Protection Agency, Office of Research and Development, National Center for 

Environmental Assessment, Washington, D.C. This document is available online at 

http://www.epa.gov/ncea/pdfs/coaqcd.pdf. A copy of this document is available in Docket Identification 

EPA-HQ-OAR-2004-0008-0050. 

189 U.S. EPA (2000). Air Quality Criteria for Carbon Monoxide. EPA600-P-99-001F. June 1, 2000. U.S. 

Environmental Protection Agency, Office of Research and Development, National Center for 

Environmental Assessment, Washington, D.C. This document is available online at 

http://www.epa.gov/ncea/pdfs/coaqcd.pdf. A copy of this document is available in Docket Identification 

EPA-HQ-OAR-2004-0008-0050. 

190 National Academy of Sciences (2003). Managing Carbon Monoxide Pollution in Meteorological and 

Topographical Problem Areas. The National Academies Press, Washington, D.C. This document is 

available on the internet at http://www.nap.edu. 

191 National Academy of Sciences (2003). Managing Carbon Monoxide Pollution in Meteorological and 

Topographical Problem Areas. The National Academies Press, Washington, D.C. This document is 

available on the internet at http://www.nap.edu. 

192 National Park Service: Department of Interior; National Institute for Occupational Safety and Health. 

(2004) Boat-related carbon monoxide (CO) poisonings. Updated: October 2004 [Online at 

2-60 
Regulatory Impact Analysis 

http://safetynet.smis.doi.gov/thelistbystate10-19-04.pdf] A copy of this document is available in Docket 

Identification EPA-HQ-OAR-2004-0008-0106. 

193 U.S. Department of Interior. (2004) Carbon monoxide dangers from generators and propulsion engines. 

On-board boats - compilation of materials. [Online at http://safetynet.smis.doi.gov/COhouseboats.htm] A 

copy of this document is available in Docket Identification EPA-HQ-OAR-2004-0008-0110. 

194 Letter dated April 5, 2001 to Mr. John Stenseth, Fun Country Marine Industries, Inc., from Ronald M. 

Hall, NIOSH. 

195 Gabele, P. (1997) Exhaust emissions from four-stroke lawn mower engines. Air Waste Manage Assoc. 

47: 945-952. 

196 Priest, M.W.; Williams, D.J.; and Bridgman, H.A. (2000) Emissions from in-use lawn-mowers in 

Australia. Atmos Environ. 34:657-664. 

197 Bunger, J.; Bombosch, F.; Mesecke, U.; and Hallier, E. (1997) Monitoring and analysis of occupational 

exposure to chain saw exhausts. Am Ind Hyg Assoc J. 58:747-751. 

198 Baldauf, R.; Fortune, C.; Weinstein, J.; Wheeler, M.; and Blanchard, F. (2006) Air contaminant 

exposures during the operation of lawn and garden equipment. Journal of Exposure Science and 

Environmental Epidemiology. 16(4):362-370. 

2-61 

Emission Inventory 

CHAPTER 3: Emission Inventory 

This chapter presents our analysis of the emission impact of the final Phase 3 standards 

for spark ignition (SI) small nonroad engines (#25 horsepower (hp) or #19 kilowatts (kW) used 

in land-based or auxiliary marine applications (hereafter collectively termed small nonroad SI 

engines) and marine SI engines. The control requirements include exhaust and evaporative 

emission standards for small non-handheld SI engines (Class I <225 cubic centimeters (cc) and 

Class II $225 cc), an evaporative emission standards for small handheld SI engines (Classes IIIV), and exhaust and evaporative emission standards for all marine SI engines. 

Section 3.1 presents an overview of methodology used to develop the emission 

inventories for the small nonroad and marine engines that are subject to the final rulemaking. 

Section 3.2 identifies the specific modeling inputs that were used to develop the baseline 

scenario emission inventories. The resulting baseline emission inventories are also presented in 

that section. Section 3.3 then describes the contribution of the small nonroad and marine SI 

engines to national baseline inventories. Section 3.4 describes the development of the controlled 

inventories, specifically the changes made to the baseline modeling inputs to incorporate the new 

standards. The control inventories are also presented in this section. Section 3.5 follows with 

the projected emission reductions resulting from the final rule. Section 3.6 describes the 

emission inventories used in the air quality modeling described in Chapter 2. This discussion 

includes a description of the changes in the inputs and resulting emission inventories between the 

preliminary baseline and control scenarios used for the air quality modeling and the slightly 

refined baseline and control scenarios reflected in the actual final rule. 

The emission inventory estimates contained in Sections 3.2, 3.4, 3.5, and 3.6, for small 

nonroad and marine SI engines are reported for the 50-state geographic area that comprises the 

United States (including the District of Columbia). These inventories reflect the emissions from 

the engines subject to the final Phase 3 standards, i.e., federal engines. As such, they exclude the 

emissions from engines that are regulated by the State of California as provided for by section 

209 of the Clean Air Act. 

More specifically, California has been granted a waiver under the Clean Air Act to 

regulate the emissions from all nonroad SI engines, except for engines with less than 175 

horsepower that are used in farm and construction equipment. Therefore, these latter engines are 

subject to federal regulation and are included in our 50-state inventories. By contrast, we do not 

include any of the emissions from California marine SI engines in these inventories. As with 

certain nonroad engine classes, the State has been granted a waiver to regulate the exhaust 

emissions from all marine SI engines and evaporative emissions from outboard and personal 

watercraft SI engines. That State also has indicated its intent to adopt the final Phase 3 standards 

for evaporative emissions from sterndrive engines. Therefore, the 50-state inventories presented 

in Sections 3.2, 3.4, 3.5, and 3.6 only reflect the emissions from small nonroad and marine SI 

engines that are subject to federal regulation. 

3-1 
Final Regulatory Impact Analysis 

Section 3.3 presents a nationwide comparison of the emissions from small nonroad and 

marine SI engines to those from other source categories, i.e., stationary, area, and other mobile 

sources. Unlike the 50-state inventories described earlier, these inventories reflect the emissions 

from all sources, whether they are separately regulated by a state government or the federal 

government, e.g., all of California’s small SI and marine SI engines are included. 

Inventories are generally presented for the following pollutants: exhaust and evaporative 

hydrocarbons reported as total hydrocarbons (THC) and volatile organic compounds (VOC), 

oxides of nitrogen (NOx), particulate matter (PM2.5 and PM10), and carbon monoxide (CO). The 

VOC category is a broader class of hydrocarbon compounds than THC that is primarily 

important for air quality modeling purposes. The additional compounds that comprise this 

category are reactive oxygenated species represented by aldehydes (RCHO) and alcohols 

(RCOH), and less reactive species represented by methane (CH4) and ethane (CH3CH3). The PM 

inventories for particle sizes of #2.5 microns or #10 microns in diameter include directly emitted 

PM only, although secondary sulfates are taken into account in the air quality modeling as noted 

below. Toxic pollutant inventories are also presented because the final Phase 3 requirements 

will reduce hazardous air pollutants such as benzene, formaldeyde, acetaldehyde, 1,3-butadiene, 

acrolein, napthalene, and 15 other compounds grouped together as polycyclic organic matter 

(POM). 

Finally, none of the controlled inventory estimates include the potential uses of the 

averaging, banking, and trading (ABT) program for engine manufacturers, since these are 

flexibilities that would be difficult to predict and model. More information regarding these 

provisions can be found in the preamble for this final rule that is published in the Federal 

Register. 

3.1 Overview of Small Nonroad and Marine SI Engine Emissions Inventory 

Development 

This section describes how the final emission inventories were modeled for the small 

nonroad and marine SI engines that are affected by the Phase 3 standards. Generally, the 

inventories were generated using a modified version of our NONROAD2005 model. More 

specifically, we started with the most recent public version of the model, i.e., NONROAD2005a, 

which was released in February 2006. A copy of that model and the accompanying technical 

reports that detail of the modeling inputs (e.g., populations, activity, etc.) are available in the 

docket for this final rule.1 They can also be accessed on our website at: 

http://www.epa.gov/otaq/nonrdmdl.htm. 

The NONROAD2005a model was modified to incorporate new emission test data and 

other improvements for this rulemaking. This special version is named NONROAD2005d. A 

copy of the model and the accompanying documentation are available in the docket.2,3,4 The 

inputs we used to model the effects of the Phase 3 standards are also described in Chapter 4 for 

exhaust emissions and Chapter 5 for evaporative emissions. Finally, the modifications we made 

to NONROAD2005a to reflect the baseline and control scenarios related to the final rule are 

3-2 
Emission Inventory 

summarized in Sections 3.2 and 3.4, respectively. 

The nonroad model estimates emission inventories of important air pollutant species from 

a diverse universe of nonroad equipment. The model’s scope includes all off-highway sources 

with the exception of locomotives, aircraft and commercial marine vessels. The model can 

distinguish emissions on the basis of equipment type, horsepower, and technology group. For 

the engines subject to the final rule, the nonroad model evaluates numerous equipment types 

with each type containing multiple horsepower categories and technology groups. A central 

feature of the model is the projection of past, present, or future emissions between 1970 and 

2050. 

The chemical species NOx, PM, and CO are exhaust emissions, i.e., pollutants emitted 

directly as exhaust from the combustion of fuel (both liquid and gaseous fuels) in the engine. 

Hydrocarbon species, e.g., THC and VOC, consist of both exhaust and evaporative emissions. 

The exhaust component represents hydrocarbons emitted as products of combustion, which can 

also include emissions vented from the crankcase. The evaporative hydrocarbon component 

includes compounds from unburned fuel that are emitted either while the engine is being 

operated or when the equipment is not in use. The various categories of evaporative emissions 

that are included in the nonroad model are: 

Diurnal. These emissions result from changes in temperature during the day. As the day 

gets warmer there is a concomitant rise in the temperature of the liquid fuel in the fuel tank. This 

causes the vapor pressure inside the tank to increase, forcing vaporized fuel to escape into the 

atmosphere. For modeling purposes, this category also includes diffusion losses that come from 

fuel vapor exiting the orifice of a vented fuel tank cap regardless of temperature. 

Permeation. These emissions occur when fuel molecules transfuse through plastic or 

rubber fuel-related components (fuel lines and fuel tanks) into the atmosphere. 

Hot Soak. These emissions occur after the engine is shut off and the engine’s residual 

heat causes fuel vapors from the fuel tank or fuel metering device to be released into the 

atmosphere. 

Running Loss. Similar in form to diurnal losses, these emissions are caused from the 

engine’s heat during equipment operation. 

Vapor Displacement or Refueling Loss. These are vapors displaced from the fuel tank 

when liquid fuel is being added during a refueling event. 

Liquid Spillage. This refers to the liquid fuel that is spilled when equipment is refueled 

either from a portable fuel container or fuel pump, which subsequently evaporates into the 

atmosphere. 

Equipment fueled by compressed natural gas, liquified petroleum gas, or diesel fuel are 

assumed to have zero evaporative emissions. Consequently, all evaporative emissions are from 

3-3 
Final Regulatory Impact Analysis 

gasoline or gasoline blends, i.e., ethanol and gasoline. 

The control scenario analyzed in Section 3.4 reflects the final Phase 3 standards for 

exhaust hydrocarbons, CO, and NOx from small nonhandheld nonroad and marine SI engines.a 

New standards to control evaporative emissions from hose permeation and tank permeation from 

these engine classes and handheld equipment are also included. Further, the final requirements 

also establish new standards for running loss and diffusion emissions from small nonhandheld 

nonroad SI engines and diurnal emissions from marine SI engines. Finally, we expect that the 

technology necessary to achieve the final exhaust emission standards will indirectly lower 

exhaust PM. All of these effects are reflected in the controlled emission inventories presented in 

this chapter. 

3.2 Baseline Emission Inventory Estimates 

This section describes more specifically how we developed the baseline exhaust and 

evaporative inventories for small nonroad and marine SI engines. The resulting baseline 

inventories are also presented. Section 3.2.1 provides this information for exhaust and 

evaporative emissions. 

The inventory estimates presented throughout this section include only equipment that 

would be subject to the final standards. For small nonroad SI equipment, California’s Air 

Resources Board (ARB) has promulgated standards that are roughly equivalent in stringency 

overall to final Phase 3 federal standards, although some of the specific requirements and test 

procedures are different. However, the Clean Air Act prohibits California from regulating 

engines used in farm and construction equipment with maximum power levels below 175 hp or 

130 kW. Therefore, the requirements contained in this final rule for small nonroad SI engines 

will apply in California to the above farm and construction equipment power levels. As a result, 

these engines are included in the inventories presented in this chapter. However, the majority of 

the small nonroad SI equipment in California is subject to ARB regulations, so the effect of the 

federal Phase 3 standards for these engines in that State is rather limited. 

For marine SI engines, ARB also has its own exhaust emission standards that are roughly 

equivalent overall to the final Phase 3 federal standards. In addition, ARB has stated its intend 

to develop evaporative emissions standards for marine SI equipment in California. Therefore, 

the exhaust and evaporative inventory estimates for marine SI engines/equipment completely 

exclude California. 

3.2.1 Baseline Exhaust and Evaporative Emissions Estimates for THC, VOC, NOx, PM2.5, 

PM10, and CO 

The baseline exhaust and evaporative emission inventories for small nonroad and marine 

SI engines include the effects of all existing applicable federal emission standards. We 

a

 The CO standard applies to small nonhandheld SI engines used in auxiliary marine applications. 

3-4 
Emission Inventory 

generated these inventories by starting with the NONROAD2005a emissions model, which was 

released to the public in February 2006. That model was then modified to incorporate new 

emission test data and other improvements for this rulemaking. This special version of the 

model is named NONROAD2005d. The modifications to the base model are described below. 

3.2.1.1 Changes from NONROAD2005a to NONROAD2005d 

As already mentioned, a number of improvements to the most publically available 

nonroad emissions inventory model were made to develop the NONROAD2005d, which is used 

in this final rulemaking. These revisions were based on recent testing programs, other 

information, and model enhancements. The changes are summarized below for small nonroad 

and marine SI engines. Many of the most important revisions are discussed in greater detail in 

the following sections. 

3.2.1.1.1 Revisions for Small SI Engines 

The modifications that we made to the NONROAD2005a model for Small SI engines 

that are most relevant to the final rule are summarized below: 

1.	 Revised fuel tank and hose permeation emission factors; 

2.	 Added new fuel tank diffusion losses to the diurnal emission estimates; 

3.	 Updated or corrected exhaust emission factors and deterioration rates, and 

technology-type sales fractions for Phase 2 engines; 

4.	 Adjusted equipment populations to properly account for the application of federal 

emission requirements to engines in California; 

5.	 Added the ability to specifically model the effects of ethanol blends on exhaust 

emissions and on fuel tank and hose permeation losses; 

6.	 Added hot soak and running losses for handheld equipment; 

7.	 Corrected snowblower technology types to include 4-stroke engines; and 

8.	 Corrected running loss emission factors for Class 1 snowblowers to account for 

cold weather applications. 

3.2.1.1.2 Revisions for Recreation Marine SI Engines 

The modifications that we made to the NONROAD2005a model for marine SI engines 

that are most relevant to the final rule are summarized below: 

1.	 Revised brake-specific fuel consumption factors; 

2.	 Revised PM emission factors for 2-stroke technology engines; 

3.	 Revised fuel tank and hose permeation emission factors and temperature effects; 

4.	 Updated modeling inputs for high performance sterndrive and inboard (SD/I) 

engines; and 

5.	 Added the ability to specifically model the effects of ethanol blends on exhaust 

emissions and fuel tank and hose permeation losses. 

3-5 
Final Regulatory Impact Analysis 

3.2.1.2 Baseline Exhaust Emission Calculations 

3.2.1.2.1 Small SI Exhaust Calculations 

We revised the Phase 2 exhaust emission factors in the NONROAD2005d inventory 

model to reflect new information and our better understanding of the in-use emissions of these 

engines, as discussed further below. 

The nonroad model estimates exhaust emissions in a given year by applying an 

appropriate emission factor based on the engines age or hours of use. This reflects the fact that 

an engine’s exhaust emissions performance degrades over its lifetime due to normal use or 

misuse (i.e., tampering or neglect). More specifically, the emission factor is a combination of a 

“zero-hour” emission level (ZHL) and a deterioration factor (DF). The ZHL represents the 

emission rate for recently manufactured engines, i.e., engines with few operating hours. The DF 

to the degree of emissions degradation per unit of activity. Nonroad engine activity is expressed 

in terms of hours of use or fraction of its median life. This later term refers to the age at which 

50 percent of the engines sold in a given year ceased to function and have been scrapped. The 

following formula describes the basic form of the calculation: 

EFaged = ZHL × DF 

where: EFaged is the emission factor for an aged engine 

ZML is the zero hour emission factor for a new engine 

DF is the deterioration factor 

The form of the DF for nonroad SI engines is as follows: 

DF = 1 + A × (Age Factor)b for Age Factor #1 

DF = 1 + A	 for Age Factor > 1 

where: Age Factor = 	 [Cumulative Hours × Load Factor]

 Median Life at Full Load, in Hours

 A, b = constants for a given technology type; b #1. 

The constants A and b can be varied to approximate a wide range of deterioration 

patterns. "A" can be varied to reflect differences in maximum deterioration. For example, 

setting A equal to 2.0 would result in emissions at the engine’s median life being three times the 

emissions when new. The shape of the deterioration function is determined by the second 

constant, b. This constant can be set at any level between zero and 1.0; currently, the 

NONROAD model sets b equal to either 0.5 or 1.0. The first case results in a curvilinear 

deterioration rate in which most of the deterioration occurs in the early part of an engine's life. 

The second case results in a linear deterioration pattern in which the rate of deterioration is 

constant throughout the median life of an engine. In both cases, we previously decided to cap 

deterioration at the end of an engine's median life, under the assumption that an engine can only 

3-6 
Emission Inventory 

deteriorate to a certain point beyond which it becomes inoperable. For spark ignition engines at 

or below 25 horsepower, which are the subject of this final rule, the nonroad model sets the 

constant b equal to 0.5. The emission factor inputs for Phase 2 small nonroad SI engines used in 

this analysis are shown in Table 3.2-1. 

Table 3.2-1: Phase 2 Modeling Emission Factors for Small SI Engines(g/kW-hr)b 

Class/ 

Technology THC ZML THC "A" NOx ZML NOx "A" CO ZML CO "A" PM10 

ZML 

PM10 

"A"

 Class I - SV 10.30 1.753 2.57 0.180 386.53 0.070 0.35 1.753

 Class I - OHV 8.73 1.753 3.28 0.180 392.93 0.070 0.05 1.753

 Class II 5.58 1.095 3.71 0.000 472.80 0.080 0.08 1.095 

Some of the values shown in Table 3.2-1 have been updated from the NONROAD2005a 

inventory model based on data collected by EPA on in-use engines as well as 

manufacturer-supplied certification data. The ZHL emission factors for Class I engines were 

updated based on testing performed by EPA on 16 in-use walk-behind lawnmowers. The Class I 

side-valve engine A values were revised to be the same as the Class I overhead engine A values 

based on the same in-use testing of lawnmowers which showed similar in-use deterioration 

characteristics between overhead valve and sidevalve Class I engines. The Class I and Class II 

engine A values for CO emissions were revised to better reflect the level of deterioration seen in 

both the in-use lawnmower testing noted above as well as certification data provided by 

manufacturers to EPA. Finally, based on data collected from another test program of in-use 

lawnmowers, the assumption that there was no deterioration of Class I and II emissions after the 

median life was reached was revised to reflect further continued emissions deterioration after 

that point. 

Also, the model was modified to acknowledge the continued use of side-valve engine 

designs in Class I nonhandheld engines meeting Phase 2 standards. In the rulemaking that 

established those regulatory requirements, side-valve technology was assumed to be superceded 

by overhead valve designs and was modeled accordingly. In reality, side-valve technology has 

continued to be used in small nonroad SI engines. The resulting technology mixture is shown in 

Table 3.2-2. The estimated sales fractions by engine class and technology are based on sales 

information provided by engine manufacturers to EPA for the 2005 model year. A full 

description of the emission modeling information for Phase 2 engines and the basis for the 

estimates can be found in the docket for this rule. 

b

 The nonroad model calculates VOC by multiplying THC by an adjustment factor depending on engine 

and fuel type for exhaust emissions as follows: 2-stroke gasoline = 1.034; 4-stroke gasoline = 0.933; liquified 

petroleum (LPG) = 0.995; and compressed natural gas (CNG) = 0.004. Crankcase and evaporative VOC for all fuels 

other than CNG is assumed to be equivalent to THC. CNG fueled equipment do not emit crankcase and evaporative 

VOC emissions because CNG is comprised almost exclusively of methane. PM2.5 is calculated by multiplying PM10 

0.92. 

3-7 
Final Regulatory Impact Analysis 

Table 3.2-2: Phase 3 Small Nonroad SI Engine Technology Classes 

Engine Class Technology Class Percent Sales (%) 

Class I Side Valve 60 

Class I Overhead Valve 40 

Class II Overhead Valve 100 

3.2.1.2.2 Marine SI Exhaust Calculations 

The NONROAD2005a model included a number of updates to the emission rates and 

technology mix of marine SI engines.5

 These updates were largely based on data submitted to 

EPA by marine engine manufacturers as part of the certification process and on new test data 

collected by EPA.6

 However, NONROAD2005a did not include high-performance SD/I marine 

engines. High-performance marine engines are niche product and were not included in the data 

set used to develop the engine populations for the NONROAD2005a model. 

Manufacturers have more recently commented that approximately 1,500 highperformance engines are produced in the U.S. per year. These engines range from 500 to 1500 

horsepower and are used in both racing and non-racing applications. Based on conversations 

with individual high-performance engine manufacturers, we estimate that about two thirds of 

these engines are sold for use in the U.S. with an average power of about 650 horsepower. These 

engines are designed to sacrifice service life for power, but with rebuilds, generally are used for 

7-8 years (we use 8 years for our modeling). Based on these estimates and the growth rate in the 

NONROAD2005a model, we estimate a 1998 population of SD/I engines >600 horsepower of 

7500 units. One manufacturer stated that they performed a survey on the annual use of these 

engines for warranty purposes and the result was an average annual use of about 30 hours per 

year. We also updated the baseline emission factors for high performance marine engines based 

on the emission data presented in Chapter 4. Note that no changes were made to the PM 

emission factors because no new data was available. Table 3.2-3 presents the updated emission 

factors for high-performance SD/I marine engines. 

Table 3.2-3: Emission Factors for High-Performance Marine Engines [g/kW-hr] 

Pollutant Carbureted Engines 

(MS4C, Bin 12) 

Fuel-Injected Engines 

(MS4D, Bin 12) 

HC 

CO 

NOx 

PM 

BSFC 

13.8 

253 

8.4 

0.08 

400 

13.8 

207 

6.8 

0.08 

362 

3-8 
Emission Inventory 

3.2.1.3 Baseline Evaporative Emission Calculations 

Chapter 5 presents a great deal of information on evaporative emission rates from fuel 

systems used in nonroad equipment. Much of this information was incorporated into the 

NONROAD2005a model.7 However, we have continued to collect evaporative emission data 

and incorporate the new information into our evaporative emission inventory calculations. 

These updates are described below. A technical memorandum that documents the methodology 

and input values for modeling the effects of ethanol blends on nonroad engine fuel hose and tank 

permeation is also available in the docket for this final rulemaking.8 

3.2.1.3.1 Fuel Ethanol Content 

Currently, about 55 percent of fuel sold in the U.S. contains ethanol. With the recent 

establishment of the Energy Policy Act of 2005,9 this percentage is expected to increase. The 

significance of the use of ethanol in fuel, for the inventory calculations, is that ethanol in fuel can 

affect both exhaust and evaporative emissions from nonroad equipment. The oxygen content of 

the ethanol tends to make combustion mixtures leaner, which can decrease exhaust HC and CO 

emissions while increasing NOx. Also, fuel blends containing ethanol typically increase the 

permeation rate for most materials used in gasoline fuel systems. This is discussed in more 

detail below. 

Title XV, section 1501, of the Energy Policy Act requires that the total volume of 

renewable fuel increase from 4.0 to 7.5 billion gallons per year from 2006 to 2012, and the 

Energy Information Administration (EIA) predicts that production will actually surpass 11 

billion gallons per year by then. Based on these figures and projected gasoline sales from the 

Energy Information Administration,10,11 we estimate that about three-fourths of gasoline sold in 

2009 and later will contain ethanol. Table 3.2-4 presents our estimates for ethanol blended fuels 

into the future. The blend market shares shown in the last column of this table assume 10 

percent for ethanol content of blended gasoline in all areas except California, where it is 5.7 

volume percent until switching to 10 percent in 2010. 

3-9 
Final Regulatory Impact Analysis 

Table 3.2-4: Estimated Fraction of Gasoline Containing Ethanol 

Calendar Year U.S. Gasoline Sales 

[109

 gal.] 

U.S. Ethanol Sales 

[109 gal.] 

Fraction of Gas with 

Ethanol 

2000 

2001 

2002 

2003 

2004 

2005 

2006 

2007 

2008 

2009 

2010 

2011 

2012 

129.9 

132.0 

135.6 

137.0 

140.1 

140.2 

142.2 

141.7 

142.5 

144.1 

145.4 

147.1 

149.0 

1.6 

1.8 

2.1 

2.8 

3.5 

4.0 

5.5 

6.1 

7.6 

10.0 

10.9 

11.0 

11.2 

12.5% 

13.4% 

15.7% 

22.2% 

27.3% 

31.0% 

41.5% 

46.3% 

57.5% 

75.1% 

78.8% 

78.8%* 

78.8%* 

* ethanol fraction projected to be constant after 2010 

3.2.1.3.2 Hose Permeation 

We developed hose permeation emission factors based on the permeation data and hose 

requirements presented in Chapter 5. Because permeation is a function of surface area and 

because hose lengths and inner diameters are defining parameters, hose permeation rates are 

based on g/m2/day. These emission factors incorporate a more complete set of data than those in 

the NONROAD2005a model. In addition, distinctions are now made between permeation rates 

for liquid fuel versus fuel vapor exposure and between permeation rates for gasoline versus 

ethanol-blend fuels. The updated hose emission factors are discussed below and presented in 

Table 3.2-5. 

Fuel hoses in small nonroad SI applications vary greatly in construction depending on the 

individual specifications of the engine and equipment manufacturers. However most fuel hose 

used on non-handheld equipment meets the SAE J30 R7 hose requirements which includes a 

permeation requirement of 550 g/m2

/day on Fuel C at 23°C.12 Chapter 5 presents data on several 

hose constructions that range from 190 to 450 g/m2

/day on Fuel C. As discussed in Chapter 5, 

permeation is typically lower on gasoline than on Fuel C. At the same time, blending ethanol 

into the fuel increases permeation. Based on data presented in Chapter 5, we estimate that nonhandheld fuel hose permeation rates range from 27 to 180 g/m2

/day on gasoline and 80-309 

g/m2

/day on gasoline blended with 10 percent ethanol (E10). Of the data presented in Chapter 5, 

the lowest two permeation rates for SAE J30 R7 hose were from an unknown fuel hose 

construction and from a hose (used in some small nonroadSI applications) that was specially 

constructed of fuel resistant materials to facilitate painting. Dropping the unknown hose 

construction (which is not known to be used in Small SI applications), we get average 

permeation rates of 122 g/m2

/day on gasoline and 222 g/m2/day on E10 at 23/C. 

3-10 
Emission Inventory 

Chapter 5 also presents permeation data on fuel lines used in handheld equipment tested 

using E10 fuel. Based on this data, we estimate an average permeation rate at 23/C, on fuel 

containing 10 percent ethanol of 255 g/m2/day. To determine an emission factor for handheld 

fuel lines on gasoline, we used the ratio of permeation rates for NBR rubber samples on E10 

versus gasoline. The resulting permeation rate for handheld hose on gasoline was estimated to 

be 140 g/m2/day at 23/C. 

Fuel hose for portable marine fuel tanks is not subject to any established recommended 

practice. For this reason, we consider fuel hose used on portable marine fuel tanks to be 

equivalent to the hose used in Small SI applications. The supply hose for each portable marine 

fuel tank is modeled to include a primer bulb with the same permeation rate as the hose. 

Recommended practices for marine hose on SD/I vessels include a permeation rate of 

100 g/m2

/day on Fuel C and 300 g/m2/day on fuel CM15 (15 percent methanol).13,14 

Accordingly, these vessels have fuel hose with lower permeation. Rather than using the 

recommended permeation rate limits for this hose, we base the permeation emission factors for 

this hose on the data presented in Chapter 5 on gasoline with ethanol which is more 

representative of in-use fuels. Chapter 5 also includes data on commercially available low 

permeation fuel hose which is used by some manufacturers. However, we do not include this in 

the baseline emission factor calculation because its use is primarily in anticipation of upcoming 

permeation standards and would therefore not be expected to remain in the baseline without 

enactment of this final rule. 

For other vessels with installed fuel tanks (OB and PWC), we based the permeation 

emission factors on the test data in Chapter 5 on marine hose not certified to Coast Guard Class I 

requirements. 

The Coast Guard specifications for fill neck hose call for a permeation limit of 300 

g/m2

/day on Fuel C and 600 on Fuel CM15. However, fill neck hose are not usually exposed to 

liquid fuel. Therefore, we used the vapor line data presented in Chapter 5 for both fill neck and 

vent line permeation rates. Hose permeation rates for both gasoline and E10 are presented in 

Table 3.2.-5. 

Table 3.2-5: Hose Permeation Emission Factors at 23/C [g/m2

/day] 

Hose Type Gasoline E10 

Handheld equipment fuel hose 

Non-handheld equipment fuel hose 

140 

122 

255 

222 

Portable fuel tank supply hose* 

Installed system OB/PWC fuel lines 

Installed system SD/I fuel lines 

Fill necks and vent lines (vapor exposure) 

122 

42 

22 

2.5 

222 

125 

40 

4.9

 * this permeation rate is used for primer bulbs as well 

3-11 
Final Regulatory Impact Analysis 

The above permeation rates do not include any effects of deterioration. Over time, the 

fuel can draw some of the plasticizers out of the rubber in the hose, making it more brittle and 

subject to cracking. This is especially true for higher permeation fuel hoses which are generally 

less fuel resistant. Exposure to ozone over time can also deteriorate the hose. This deterioration 

would presumably increase the permeation rate over time. However, we do not have any data to 

quantify this effect and are not including deterioration in this analysis at this time. Lower 

permeation fuel hose, such as that designed to meet the final standard would likely have much 

lower deterioration due to the use of more fuel resistant materials. Therefore, this analysis may 

underestimate the inventory and benefits associated with the final fuel permeation standards. 

3.2.1.3.3 Hose Lengths 

The hose lengths used in NONROAD2005a are based primarily on confidential 

information supplied by equipment manufacturers. Hose lengths for handheld equipment are 

based on survey data provided by the Outdoor Power Equipment Institute.15 Recently, we 

received comment from a boatbuilder using outboard motors that the hose lengths in our 

calculations were too short.16 Because our existing data set did not include outboard boats with 

installed fuel tanks, we updated the hose lengths for these vessels based on the data supplied by 

this boat builder. In addition, the vent line lengths in the NONROAD2005a were divided by two 

to account for a vapor gradient throughout the fuel line caused by diurnal breathing and 

diffusion. This factor has been removed in lieu of the new emission factors for vent lines based 

on vapor exposure. Table 3.2-6 presents the updated hose lengths for outboard boats with 

installed fuel tanks. 

Table 3.2-6: Updated Hose Lengths for Outboard Boats with Installed Fuel Systems 

Engine Power 

Category 

Fill Neck 

Length [m] 

Fuel Supply Hose 

Length [m] 

Vent Hose 

Length [m] 

18.7-29.8 kW 

29.9-37.3 kW 

37.4-74.6 kW 

74.7-130.5 kW 

130.6+ kW 

1.8 

2.4 

3.1 

3.7 

4.3 

1.8 

2.4 

3.1 

3.7 

4.3 

1.5 

1.8 

2.1 

2.4 

2.7 

3.2.1.3.4 Tank Permeation 

For fuel tanks, the NONROAD2005a model does not include a fuel ethanol effect on 

permeation. Data in Chapter 5 suggest that even polyethylene fuel tanks see a small increase in 

permeation on E10 compared to gasoline. This increase is much larger for nylon fuel tanks like 

those used in handheld equipment with structurally-integrated fuel tanks. Table 3.2-7 presents 

the updated emission factors on E10 fuel and compares them to the emission factors based on 

gasoline permeation rates. The primary difference between the permeation rates for installed 

marine tanks, compared to smaller HDPE fuel tanks, is largely due to the wall thickness of the 

different constructions rather than material permeation properties. Permeation rate is a function 

3-12 
Emission Inventory 

of wall thickness, so as tank thickness doubles, permeation rate halves. The model considers 

permeation from metal fuel tanks to be zero. 

Table 3.2-7: Tank Permeation Emission Factors at 29/C [g/m2

/day] 

Tank Type Gasoline E10 

Nylon handheld fuel tanks 

Small SI HDPE <0.25 gallons 

Small SI HDPE $0.25 gallons 

1.25 

6.5 

9.7 

2.5 

7.2 

10.7 

Portable and PWC HDPE fuel tanks 

Installed non-metal marine fuel tanks 

9.9 

8.0 

10.9 

8.8 

Metal tanks 0 0 

3.2.1.3.5 Diffusion 

The NONROAD2005a model includes an adjustment factor to diurnal emissions to 

account for diffusion. The data used to create this adjustment factor is included in Chapter 5. 

This adjustment factor is applied to all small nonroad SI equipment in the NONROAD2005a 

model. However, we believe that handheld equipment are all produced with either sealed fuel 

tanks or slosh/spill resistant fuel caps. Therefore, we do not include diffusion emissions for 

handheld equipment in this analysis. 

3.2.1.3.6 Modeling of Nonlinear Ethanol Blend Permeation Effects 

Based on the limited available test data it appears that the effect of alcohol-gasoline 

blends on permeation is nonlinear, tending to increase permeation at lower alcohol 

concentrations up to about 20 percent ethanol, but then decreasing permeation at higher alcohol 

concentrations.17 

Starting with the zero and 10 percent ethanol points described above, a simple 

exponential curve was selected to connect the zero and 10 percent points continuing up to the 20 

percent ethanol level. Then to get a nonlinear decreasing curve above 20 percent a simple 

decreasing exponential curve was used. Since effects above 85 percent are especially uncertain, 

and no such fuels are foreseen for use in nonroad equipment, the effect above 85 percent was set 

equal to the E85 effect. The equations used are shown here, and an example curve based on 

these equations is shown in Figure 3.2-1. 

3-13 
Final Regulatory Impact Analysis 

Hose and Tank Permeation for zero to 20 percent ethanol volume percent: 

 Permeation EF = GasEF + GasEF × (E10fac - 1) × [ (EthVfrac / 0.10) ^ 0.4 ] 

Hose and Tank Permeation for ethanol volume percent greater than 20 percent: 

 Permeation EF = GasEF × { 1 + (E10fac - 1) × [ (20 / 10) ^ 0.4 ] } 

× { 1 - [ (MIN(EthVfrac, 0.85) - 0.20 ) / 0.80 ] ^ (1 / 0.4 ) } 

where: 

Permeation EF = Permeation emission factor for modeled fuel (grams per meter2 per day) 

GasEF = Gasoline hose permeation emission factor from input EF data files (grams per 

meter2

 per day) 

E10fac = permeation emission adjustment factor for E10 relative to gasoline. This is the 

ratio of the E10 to gasoline permeation emission factors (unitless) 

EthVfrac = Volume fraction ethanol in the fuel being modeled. E10 = 0.10 

0.4 = exponent chosen to yield a reasonable shape of curve.

 Figure 3.2-1: Ethanol Blend Hose Permeation Example Curve 

It should be noted that all ethanol blends currently modeled with the NONROAD model 

are less than or equal to E10, so no parts of this curve above E10 are used. Also, the value of 

E10fac used in the modeling of the control case is 2.0 for all the tank and hose permeation 

sources listed above in Tables 3.2-6 and 3.2-7. 

3-14 
Emission Inventory 

3.2.1.3.7 Modeling Effect of Ethanol Blend Market Share on Permeation 

The effect of ethanol blend market share is modeled linearly. In most areas the ethanol 

blend market share is either zero or 100 percent, but in areas where it is between those two 

market shares, or when doing a nationwide model run, the effect is calculated as a simple 

proportion. For instance a 30 percent market share of E10 would be modeled using a permeation 

rate 30 percent of the way between the E0 permeation rate and the E10 permeation rate. 

3.2.1.4 Baseline Exhaust and Evaporative Inventory Results for THC, VOC, NOx, 

PM2.5, PM10, and CO 

Table 3.2-8 presents the 50-state baseline emission inventories, respectively, for small 

nonroad SI engines. Table 3.2-9 provides the same information for marine SI engines. 

3-15 
Final Regulatory Impact Analysis 

Table 3.2-8: Baseline 50-State Annual Exhaust and Evaporative Emissions for 

Small Nonroad Spark-Ignition Engines (short tons) 

Year THC VOC NOx PM2.5 PM10 CO 

2002 1,064,625 1,047,374 106,804 23,382 25,416 15,091,835 

2003 1,026,922 1,009,822 106,852 23,480 25,522 14,351,829 

2004 963,709 945,601 106,610 23,483 25,525 13,690,337 

2005 886,524 867,081 106,847 23,417 25,453 12,923,819 

2006 825,413 804,926 109,233 23,498 25,541 12,252,479 

2007 768,239 747,552 109,439 23,804 25,874 11,711,607 

2008 718,564 700,010 111,235 24,335 26,451 10,861,441 

2009 682,088 665,890 116,329 24,882 27,045 9,992,801 

2010 665,762 650,954 118,376 25,402 27,611 9,623,727 

2011 663,620 649,358 119,424 25,888 28,139 9,568,610 

2012 665,666 651,743 120,820 26,364 28,657 9,579,040 

2013 671,328 657,539 122,506 26,832 29,165 9,644,512 

2014 679,634 665,819 124,400 27,291 29,664 9,751,728 

2015 689,045 675,131 126,395 27,747 30,160 9,879,027 

2016 699,225 685,164 128,468 28,202 30,654 10,020,040 

2017 709,899 695,658 130,573 28,655 31,146 10,169,185 

2018 720,944 706,498 132,701 29,107 31,638 10,324,079 

2019 732,284 717,615 134,846 29,558 32,128 10,483,706 

2020 743,755 728,853 137,002 30,009 32,618 10,645,870 

2021 755,254 740,118 139,160 30,460 33,109 10,808,929 

2022 766,782 751,412 141,317 30,911 33,599 10,972,659 

2023 778,333 762,727 143,475 31,362 34,089 11,136,954 

2024 789,900 774,056 145,636 31,813 34,579 11,301,731 

2025 801,493 785,411 147,806 32,265 35,070 11,467,292 

2026 813,217 796,890 150,003 32,718 35,563 11,634,934 

2027 824,971 808,397 152,209 33,173 36,057 11,803,402 

2028 836,736 819,915 154,418 33,627 36,551 11,972,207 

2029 848,508 831,439 156,628 34,081 37,045 12,141,251 

2030 860,287 842,970 158,840 34,535 37,538 12,310,505 

2031 872,069 854,504 161,053 34,990 38,032 12,479,899 

2032 883,856 866,042 163,266 35,444 38,526 12,649,385 

2033 895,645 877,583 165,479 35,898 39,020 12,818,940 

2034 907,437 889,126 167,692 36,353 39,514 12,988,554 

2035 919,232 900,672 169,906 36,807 40,008 13,158,228 

2036 931,029 912,219 172,119 37,261 40,502 13,327,954 

2037 942,828 923,769 174,332 37,716 40,995 13,497,732 

2038 954,629 935,321 176,546 38,170 41,489 13,667,556 

2039 966,431 946,874 178,759 38,625 41,983 13,837,424 

2040 978,235 958,429 180,973 39,079 42,477 14,007,335 

3-16 
Emission Inventory 

Table 3.2-9: Baseline 50-State Annual Exhaust and Evaporative Emissions for 

Marine Spark-Ignition Engines (Short Tons) 

Year THC VOC NOx PM2.5 PM10 CO 

2002 906,318 931,132 46,311 15,092 16,404 2,472,251 

2003 873,287 896,969 49,694 14,417 15,670 2,407,992 

2004 836,493 858,916 53,397 13,679 14,869 2,346,538 

2005 796,279 817,340 57,862 12,886 14,007 2,266,733 

2006 756,781 776,480 63,366 12,090 13,142 2,170,374 

2007 717,924 736,303 67,730 11,311 12,295 2,103,059 

2008 680,702 697,795 73,894 10,553 11,470 2,007,804 

2009 645,730 661,588 82,123 9,824 10,678 1,885,970 

2010 612,180 626,901 87,140 9,149 9,945 1,823,844 

2011 580,750 594,415 90,516 8,525 9,266 1,788,830 

2012 553,441 566,191 93,662 7,983 8,678 1,758,115 

2013 530,682 542,671 96,528 7,534 8,189 1,732,653 

2014 511,166 522,503 99,197 7,144 7,766 1,710,005 

2015 495,178 505,981 101,703 6,823 7,416 1,690,755 

2016 481,650 492,000 104,022 6,549 7,118 1,673,978 

2017 470,667 480,648 106,158 6,324 6,874 1,660,415 

2018 462,602 472,308 108,084 6,156 6,691 1,650,631 

2019 455,864 465,336 109,885 6,012 6,535 1,642,841 

2020 451,176 460,481 111,525 5,908 6,422 1,638,114 

2021 447,624 456,799 113,063 5,826 6,333 1,635,047 

2022 445,371 454,457 114,479 5,768 6,270 1,634,065 

2023 443,951 452,972 115,802 5,726 6,224 1,634,672 

2024 443,203 452,179 117,052 5,696 6,191 1,636,603 

2025 443,196 452,151 118,228 5,680 6,174 1,639,914 

2026 443,770 452,720 119,344 5,675 6,168 1,644,492 

2027 444,806 453,764 120,401 5,678 6,172 1,650,159 

2028 446,152 455,126 121,411 5,687 6,182 1,656,748 

2029 447,768 456,766 122,387 5,701 6,197 1,663,933 

2030 449,626 458,656 123,335 5,719 6,217 1,671,627 

2031 451,666 460,733 124,260 5,741 6,240 1,679,753 

2032 453,836 462,943 125,166 5,765 6,266 1,688,228 

2033 456,159 465,310 126,052 5,792 6,296 1,697,074 

2034 458,592 467,790 126,922 5,821 6,327 1,706,229 

2035 461,115 470,363 127,777 5,851 6,360 1,715,675 

2036 463,691 472,990 128,621 5,883 6,394 1,725,343 

2037 466,323 475,674 129,454 5,915 6,429 1,735,210 

2038 468,999 478,403 130,278 5,948 6,465 1,745,240 

2039 471,706 481,164 131,095 5,982 6,502 1,755,400 

2040 474,437 483,949 131,907 6,016 6,539 1,765,651 

3-17 
Final Regulatory Impact Analysis 

3.2.2 Baseline Hazardous Air Pollutant Estimates 

The analysis of toxic air pollutants from small nonroad and marine SI engines focuses on 

seven major pollutants: benzene, formaldehyde, acetaldehyde, 1,3-butadiene, acrolein, 

naphthalene, and 15 other compounds grouped together as polycyclic organic matter (POM) for 

this analysis.c

 All of these compounds, except acetaldehyde, were identified as national or 

regional cancer or noncancer "risk" drivers in the 1999 National Scale Air Toxics Assessment 

(NATA)18 and have significant inventory contributions from mobile sources. That is, for a 

significant portion of the population, these compounds pose a significant portion of the total 

cancer or noncancer risk from breathing outdoor air toxics. The health effects of these hazardous 

pollutants are specifically discussed in Chapter 2. Many of these compounds are also part of the 

THC and VOC inventories. An exception is formaldehyde, which is not measured by the 

analytic technique used to measure THC, and part of the mass of other aldehydes as well. 

However, all are included in the VOC inventories presented in this chapter. 

The baseline inventories for each of the toxic air pollutants described above were 

developed using EPA’s National Mobile Inventory Model (NMIM). This model is an analytical 

framework that links a county-level database to our NONROAD model and collates the output 

into a single database table. The resulting estimates for small nonroad and marine SI engines 

account for local differences in fuel characteristics and temperatures on a much finer scale than 

is possible when running the standalone NONROAD model. Emissions were modeled for all of 

the small nonroad and marine SI equipment categories in the continental United States, including 

California. Hence, the hazardous emission inventories presented here include the emissions 

from engines that are regulated by that State. As a result, the emission inventories are slightly 

overstated relative to the those from the small nonroad and marine SI engines subject to the 

federal Phase 3 requirements. 

Table 3.2-10 presents the 50-state baseline inventories for toxic air emissions from small 

nonroad SI engines in 2002, 2020, 2030. Table 3.2-11 provides the same information for marine 

SI engines. 

Table 3.2-10: Baseline 50-State Air Toxic Emissions for 

Small Nonroad Spark-Ignition Engines (short tons) 

Year Benzene 

1,3 

Butadiene 

Formaldehyde Acetaldehyde Acrolein Naphthalene POM 

2002 35,086 5,561 8,664 2,900 505 447 97 

2020 23,216 3,468 5,802 2,792 291 638 131 

2030 26,776 3,999 6,691 3,217 336 739 152 

c

 The 15 POMs summarized in this chapter are acenaphthylene, anthracene, benz(a)anthracene, 

benzo(a)pyrene, benzo(b)fluoranthene, benzo(g,h,i)perylene, beno(k)fluoranthene, chrysene, dibenzo(a,h)anthracene, 

fluoranthene, fluorene, ideno(1,2,3-c,d)pyrene, phenanthrene, and pyrene. 

3-18 
Emission Inventory 

Table 3.2-11: Baseline 50-State Air Toxic Emissions for 

Marine Spark-Ignition Engines (short tons) 

Year Benzene 

1,3 

Butadiene 

Formaldehyde Acetaldehyde Acrolein Naphthalene POM 

2002 23,110 2,053 2,153 1,543 211 37 31 

2020 8,417 763 535 818 27 42 16 

2030 8,476 751 525 811 27 46 16 

3.3 Contribution of Small Nonroad and Marine SI Engines to National 

Emissions Inventories 

This section describes the nationwide contribution of small nonroad and marine SI 

engines to the emissions of other source categories. Information is presented for the pollutants 

that are directly controlled by the final standards, i.e., VOC, NOx, and CO, and those that are 

indirectly reduced by some of the requisite control technology, i.e., PM2.5 and PM10. The VOC 

inventories includes both exhaust and evaporative hydrocarbon emissions. 

The national inventories are presented for 2002, 2020, and 2030 for all 50-states and the 

District of Columbia.19 The stationary, highway, and aircraft inventories were taken directly 

from EPA’s National Emissions Inventory (NEI) modeling platform for 2002.20 The emission 

inventories for locomotives, and Classes 1 and 2 commercial marine engines were taken from 

our recent final rule for these mobile source categories.21 The inventories for Class 3 

commercial marine engines was take from our recent advance notice of final rulemaking for that 

category of engines.22 The emission estimates for portable fuel containers was taken from the 

recent final MSAT rule.23 All of the land-based nonroad engine emission inventories was 

developed using the NONROAD2005d model, as previously described.d Finally, these 

inventories account for the future use of renewable fuels as required by the Energy Policy Act of 

2005. 

3.3.1 VOC Emissions Contribution 

Table 3.3-1 provides the contribution of small nonroad SI engines, marine SI engines and 

other source categories to nationwide VOC emissions. The emissions from small nonroad 

(<19kW) and marine SI engines are 26 percent of the mobile source inventory and 12 percent of 

the total manmade VOC emissions in 2002. These percentages decrease slightly to 23 percent 

and 10 percent, respectively, by 2030. 

d The modeling inputs for diesel nonroad engines that were used in NONROAD2005d for this final rule 

are the same as those contained in the NONROAD2005a public. 

3-19 
Final Regulatory Impact Analysis 

3.3.2 NOx Emissions Contribution 

Table 3.3-2 provides the contribution of nonroad small nonroad SI engines, marine SI 

engines and other source categories to nationwide NOx emissions. The emissions from small 

nonroad and marine SI engines are about 1 percent of the mobile source inventory and about 1 

percent of the total manmade NOx emissions in 2002. These percentages increase to 6 percent 

and 3 percent, respectively, by 2030. 

3.3.3 PM Emissions Contribution 

Table 3.3-3 and 3.3-4 provide the contribution of small nonroad SI engines, marine SI 

engines and other source categories to nationwide PM2.5 and PM10 emissions, respectively. Both 

particle size categories from small nonroad and marine SI engines are about 8 percent of the 

mobile source inventory and approximately 1 percent of the total manmade PM2.5 emissions in 

2002. The mobile source percentage increases to about 12 percent and the total manmade 

percentage stay about the same at 1 percent by 2030. 

3.3.4 CO Emissions Contribution 

Table 3.3-5 provides the contribution of small nonroad SI engines, marine SI engines, 

and other source categories to nationwide CO emissions. The emissions from small nonroad and 

marine SI engines are 23 percent of the mobile source inventory and 10 percent of the total 

manmade CO emissions in 2002. These percentages decrease to 30 percent and increase to 25 

percent, respectively, by 2030. 

3-20 
Table 3.3-1: 50-State Annual VOC Baseline Emission Levels for

 Mobile and Other Source Categories

Category 

2002 2020 

short tons 

% of 

mobile % of total short tons 

% of 

mobile % of total short tons 

Small Nonroad SI total 1,165,257 14.0% 6.6% 808,873 19.6% 6.3% 935,619 

 NonHandheld Small SI 675,311 8.1% 3.8% 590,186 14.3% 4.6% 684,057  Handheld Small SI 489,946 5.9% 2.8% 218,688 5.3% 1.7% 251,562 Recreational Marine SI 1,003,325 12.1% 5.7% 496,183 12.0% 3.9% 494,217 

Locomotive 50,665 0.6% 0.3% 27,974 0.7% 0.2% 17,722 Recreational Marine Diesel 1,538 0.0% 0.0% 2,485 0.1% 0.0% 2,912 

Commercial Marine (C1 & C2) 17,229 0.2% 0.1% 11,478 0.3% 0.1% 6,911 

Land-Based Nonroad Diesel 184,868 2.2% 1.0% 76,817 1.9% 0.6% 63,342 Commercial Marine (C3) 26,175 0.3% 0.1% 53,204 1.3% 0.4% 79,697 SI Recreational Vehicles 551,285 6.6% 3.1% 442,121 10.7% 3.4% 382,468 Large Nonroad SI (>25hp) 134,950 1.6% 0.8% 11,957 0.3% 0.1% 9,953 Portable Fuel Containers 243,994 2.9% 1.4% 38,185 0.9% 0.3% 43,375 

Aircraft 52,651 0.6% 0.3% 63,251 1.5% 0.5% 67,730 

Total Off Highway 3,431,938 41.3% 19.3% 2,032,530 49.2% 15.8% 2,103,947 

Highway Diesel 191,514 2.3% 1.1% 129,321 3.1% 1.0% 140,959 

Highway Non-Diesel 4,684,391 56.4% 26.4% 1,973,180 47.7% 15.3% 1,800,856 

Total Highway 4,875,904 58.7% 27.5% 2,102,501 50.8% 16.3% 1,941,815 

Total Diesel (distillate) Mobile 445,814 5.4% 2.5% 248,075 6.0% 1.9% 231,847 

Total Mobile Sources 8,307,843 100% 46.8% 4,135,030 100% 32.1% 4,045,762 Stationary Point and Area Sources 9,433,356 - 53.2% 8,740,057 - 67.9% 8,740,057 

Total Man-Made Sources 17,741,198 - 100% 12,875,088 - 100% 12,785,819 
Table 3.3-2: 50-State Annual NOx Baseline Emission Levels

 for Mobile and Other Source Categories 

2002 2020 

% of % of 

mobile mobile 

Category short tons source % of total short tons source % of total short tons 

Small Nonroad SI 119,833 0.9% 0.6% 153,872 2.7% 1.3% 178,406 

 NonHandheld Small SI 116,743 0.9% 0.5% 148,004 2.6% 1.3% 171,650 

 Handheld Small SI 3,090 0.0% 0.0% 5,867 0.1% 0.1% 6,756 

Recreational Marine SI 49,902 0.4% 0.2% 120,172 2.1% 1.0% 132,898 

Locomotive 1,118,786 8.8% 5.2% 669,405 11.7% 5.8% 437,245 

Recreational Marine Diesel 40,437 0.3% 0.2% 43,579 0.76% 0.38% 43,665 

Commercial Marine (C1 & C2) 834,025 6.5% 3.9% 499,798 8.77% 4.36% 308,614 

Land-Based Nonroad Diesel 1,555,812 12.2% 7.3% 683,481 12.0% 5.96% 435,774 Commercial Marine (C3) 745,224 5.9% 3.5% 1,368,420 24.00% 11.93% 2,023,974 

SI Recreational Vehicles 10,614 0.1% 0.0% 30,108 0.5% 0.3% 34,318 

Large Nonroad SI (>25hp) 336,292 2.6% 1.6% 48,270 0.8% 0.42% 47,766 

Aircraft 103,591 0.8% 0.5% 132,278 2.32% 1.15% 143,986 

Total Off Highway 4,914,515 38.6% 23.0% 3,749,382 65.8% 32.7% 3,786,645 

Highway Diesel 3,529,046 27.7% 16.5% 681,142 11.9% 5.9% 355,817 Highway Non-Diesel 4,293,733 33.7% 20.1% 1,270,269 22.3% 11.1% 1,144,199 

Total Highway 7,822,779 61.4% 36.6% 1,951,411 34.2% 17.0% 1,500,016 

Total Diesel (distillate) Mobile 7,078,105 55.6% 33.2% 2,577,404 45.2% 22.5% 1,581,115 

Total Mobile Sources 12,737,294 100% 59.7% 5,700,793 100% 49.7% 5,286,661 

Stationary Point and Area Sources 8,613,718 - 40.3% 5,773,927 - 50.3% 5,773,927 

Total Man-Made Sources 21,351,012 - 100% 11,474,721 - 100% 11,060,589 
Table 3.3-3: 50-State Annual PM2.5 Baseline Emission Levels

 for Mobile and Other Source Categories 

2002 2020 

% of % of 

mobile mobile 

Category short tons source % of total short tons source % of total short tons 

Small Nonroad SI 25,700 5.2% 0.7% 32,905 10.0% 1.0% 37,878 

 NonHandheld Small SI 4,841 1.0% 0.1% 6,957 2.1% 0.2% 8,065 

 Handheld Small SI 20,859 4.2% 0.6% 25,947 7.9% 0.8% 29,813 

Recreational Marine SI 16,262 3.3% 0.5% 6,367 1.9% 0.2% 6,163 Locomotive 29,660 5.99% 0.84% 15,145 4.59% 0.45% 8,584 

Recreational Marine Diesel 1,096 0.22% 0.03% 973 0.29% 0.03% 1,053 

Commercial Marine (C1 & C2) 28,730 5.80% 0.82% 15,787 4.78% 0.47% 10,017 

Land-Based Nonroad Diesel 159,111 32.1% 4.52% 46,056 13.9% 1.36% 17,902 

Commercial Marine (C3) 54,667 11.04% 1.55% 110,993 33.61% 3.29% 166,161 

SI Recreational Vehicles 13,710 2.8% 0.4% 11,901 3.6% 0.4% 10,090 

Large Nonroad SI (>25hp) 1,652 0.3% 0.05% 2,421 0.7% 0.07% 2,844 

Aircraft 17,979 3.63% 0.51% 22,176 6.72% 0.66% 24,058 

Total Off Highway 348,568 70.4% 9.9% 264,722 80.2% 7.8% 284,749 Highway Diesel 94,982 19.2% 2.7% 20,145 6.1% 0.6% 18,802 

Highway non-diesel 51,694 10.4% 1.5% 45,329 13.7% 1.3% 51,621 

Total Highway 146,676 29.6% 4.2% 65,474 19.8% 1.9% 70,423 

Total Diesel (distillate) Mobile 313,581 63.3% 8.9% 98,106 29.7% 2.9% 56,358 

Total Mobile Sources 495,245 100% 14.1% 330,196 100% 9.8% 355,172 

Stationary Point and Area Sources 3,025,244 - 85.9% 3,047,714 - 90.2% 3,047,714 

Total Man-Made Sources 3,520,488 - 100% 3,377,911 - 100% 3,402,887 
Table 3.3-4: 50-State Annual PM10 Baseline Emission Levels

 for Mobile and Other Source Categories 

2002 2020 

% of % of 

mobile mobile % 

Category short tons source % of total short tons source % of total short tons 

Small Nonroad SI 27,935 4.9% 0.7% 35,766 8.5% 1.0% 41,172 

 NonHandheld Small SI 5,262 0.9% 0.1% 7,562 1.8% 0.2% 8,767 

 Handheld Small SI 22,673 4.0% 0.6% 28,204 6.7% 0.8% 32,406 

Recreational Marine SI 17,676 3.1% 0.5% 6,920 1.7% 0.2% 6,699 Locomotive 30,578 5.33% 0.82% 15,613 3.73% 0.43% 8,849 

Recreational Marine Diesel 1,130 0.20% 0.03% 1,003 0.24% 0.03% 1,086 

Commercial Marine (C1 & C2) 29,619 5.17% 0.79% 16,275 3.89% 0.45% 10,327 

Land-Based Nonroad Diesel 164,032 28.6% 4.40% 47,480 11.3% 1.31% 18,455 

Commercial Marine (C3) 59,409 10.36% 1.59% 120,617 28.83% 3.34% 180,566 

SI Recreational Vehicles 14,902 2.6% 0.4% 12,936 3.1% 0.4% 10,967 

Large Nonroad SI (>25hp) 1,672 0.3% 0.04% 2,441 0.6% 0.07% 2,866 

Aircraft 24,622 4.30% 0.66% 30,211 7.22% 0.84% 32,714 

Total Off Highway 371,575 64.8% 10.0% 289,263 69.1% 8.0% 313,702 

Highway Diesel 109,097 19.0% 2.9% 32,733 7.8% 0.9% 34,746 

Highway non-diesel 92,531 16.1% 2.5% 96,380 23.0% 2.7% 110,796 

Total Highway 201,628 35.2% 5.4% 129,113 30.9% 3.6% 145,542 Total Diesel (distillate) Mobile 334,456 58.3% 9.0% 113,105 27.0% 3.1% 73,464 

Total Mobile Sources 573,203 100% 15.4% 418,376 100% 11.6% 459,244 

Stationary Point and Area Sources 3,158,011 - 84.6% 3,194,610 - 88.4% 3,194,610 

Total Man-Made Sources 3,731,215 - 100% 3,612,986 - 100% 3,653,854 
Table 3.3-5: 50-State Annual CO Baseline Emission Levels 

for Mobile and Other Source Categories 

2002 2020 

% of % of 

mobile mobile % 

Category short tons source % of total short tons source % of total short tons 

Small Nonroad SI 16,943,267 19.9% 17.6% 11,934,654 25.5% 20.6% 13,803,668 

 NonHandheld Small SI 15,884,854 18.7% 16.5% 11,084,472 23.7% 19.2% 12,826,965 

 Handheld Small SI 1,058,413 1.2% 1.1% 850,181 1.8% 1.5% 976,703 

Recreational Marine SI 2,663,932 3.1% 2.8% 1,765,122 3.8% 3.1% 1,801,234 

Locomotive 123,210 0.1% 0.1% 167,488 0.4% 0.3% 195,882 

Recreational Marine Diesel 6,467 0.0% 0.0% 9,374 0.0% 0.0% 10,930 

Commercial Marine (C1 & C2) 151,331 0.2% 0.2% 139,712 0.3% 0.2% 143,791 

Land-Based Nonroad Diesel 860,257 1.0% 0.9% 310,250 0.7% 0.5% 155,576 

Commercial Marine (C3) 59,515 0.1% 0.1% 120,889 0.3% 0.2% 181,032 

SI Recreational Vehicles 1,741,702 2.0% 1.8% 1,910,030 4.1% 3.3% 1,916,102 

Large Nonroad SI (>25hp) 1,801,104 2.1% 1.9% 289,382 0.6% 0.5% 270,827 

Aircraft 557,820 0.7% 0.6% 677,930 1.4% 1.2% 723,842 

Total Off Highway 24,908,605 29.3% 25.8% 17,324,829 37.0% 29.9% 19,202,883 

Highway Diesel 940,898 1.1% 1.0% 260,238 0.6% 0.4% 219,594 

Highway non-diesel 59,178,847 69.6% 61.4% 29,211,716 62.4% 50.5% 32,038,635 

Total Highway 60,119,745 70.7% 62.4% 29,471,955 63.0% 50.9% 32,258,229 

Total Diesel (distillate) Mobile 2,082,164 2.4% 2.2% 887,061 1.9% 1.5% 725,772 Total Mobile Sources 85,028,351 100% 88.2% 46,796,783 100% 80.9% 51,461,112 Stationary Point and Area Sources 11,354,201 - 11.8% 11,049,239 - 19.1% 11,049,239 Total Man-Made Sources 96,382,552 - 100% 57,846,022 - 100% 62,510,350 
Final Regulatory Impact Analysis 

3.4 Controlled Nonroad Small Spark-Ignition and Marine Engine Emission 

Inventory Development 

This section describes how the controlled emission inventories were developed for the 

small nonroad and marine SI engines that are subject to the Phase 3 standards. The resulting 

controlled emission inventories are also presented. Section 3.4.1 provides this information for 

exhaust and evaporative emissions. 

Once again, the inventory estimates presented throughout this section only include 

equipment that would be subject to the final standards. Specifically for California, this includes 

small nonroad SI engines used in farm and construction equipment with maximum power levels 

below 175 hp or 130 kW. For marine SI engines, our analysis assumes that the final standards 

have no effect because that state already has equivalent exhaust emission standards and is 

expected to adopt equivalent evaporative hydrocarbon requirements. 

3.4.1 Controlled Exhaust and Evaporative Emissions Estimates for THC, VOC, NOx, 

PM2.5, PM10, and CO 

The controlled exhaust and evaporative emission inventories for small nonroad and 

marine SI engines were generated by modifying the input files for NONROAD2005d to account 

for the engine and equipment controls associated with the Phase 3 standards. (See the baseline 

emission inventory discussion in Section 3.2 for the changes we made to the publically available 

NONROAD2005a model to develop NONROAD2005d.) The modifications that were made to 

estimate the controlled emissions inventories are described below. 

3.4.1.1 Controlled Exhaust Emission Standards, Zero-Hour Emission Factors and 

Deterioration Rates 

3.4.1.1.1 Small SI Exhaust Emission Calculations 

The final Phase 3 emission standards and implementation schedule are shown in Table 

3.4-1. While the new standards take effect in 2011 for Class II engines and 2012 for Class I 

engines, we providing a number of flexibilities for engine and equipment manufacturers that will 

allow the continued production and use of Class II engines meeting the Phase 2 standards in 

limited numbers over the first four years of the Phase 3 program. The implementation schedule 

shown in the table is used for modeling purposes only. It is based on our assumption that engine 

and equipment manufacturers take full advantage of these flexibilities. 

3-26 
Emission Inventory 

Table 3.4-1: Phase 3 Emission Standards and Estimated Implementation Schedule 

for Class I and II Small SI Enginesa (g/kW-hr or Percent) 

Engine 

Class Requirement 2011 2012 2013 2014 2015+ 

HC+NOx -- 10 10 10 10 

Class I 

CO (marine generator

 sets only) -- 5 5 5 5 

Estimated Sales 

Percentage -- 95 95 100 100 

HC+NOx 8 8 8 8 8 

Class II 

CO (marine generator

 s ets only) 5 5 5 5 5 

Estimated Sales 

Percentage 83 83 93 93 100 

a Reflects maximum use of compliance flexibilities by engine and equipment manufacturers. Used for modeling 

purposes only. 

The modeled emission factors corresponding to the final Phase 3 standards are shown in 

Table 3.4-2. (See Section 3.2.1.2.1 for a discussion of how the model uses zero hour emission 

levels (ZML) and deterioration rates (A values.) We developed these new emission factors 

based on testing of catalyst-equipped engines both in the laboratory and in-use. A full 

description of the emission factor information for Phase 3 engines and the basis for the estimates 

can be found in the docket for this rule. 

Table 3.2-2: Phase 3 Modeling Emission Factors for Small SI Engines (g/kW-hr) 

Class/ 

Technology HC ZML HC "A" NOx ZML NOx "A" CO ZML CO "A" PM10 

ZML PM10 "A"

 Class I - SV 5.60 0.797 1.47 0.302 319.76 0.070 0.24 1.753

 Class I - OHV 5.09 0.797 1.91 0.302 325.06 0.070 0.05 1.753

 Class II 4.25 0.797 1.35 0.302 431.72 0.080 0.08 1.095 

We left the proportion of sales in each technology classification unchanged from those 

used for Phase 2 engines. The technology mix was previously shown Table 3.2-2. 

Finally, as discussed in more detail in Chapter 6, were developed a new brake-specific 

fuel consumption (BSFC) estimate for Class II engines to reflect the expected fuel consumption 

benefit associated with the use of additional electronic fuel injection technology on Phase 3 

compliant engines. The resulting BFSC for Phase 3 Class II engines is 0.735 pounds per 

horsepower-hour (lb/hp-hr). 

3-27 
Final Regulatory Impact Analysis 

3.4.1.1.2 Marine SI Exhaust Emission Calculations 

For the control case, we developed new technology classifications for engines meeting 

the final standards. For outboards and personal watercraft, we no longer will attempt to 

determine the technology mix between low emitting technology options (such as DI 2-stroke 

versus 4 stroke). The new technology classifications for these engines are simply tied to the 

standard. These new technology classifications are titled MO09 and MP09 for outboards and 

personal watercraft, respectively. In determining the combined HC+NOx emission factor, we 

used the final emission standards with a 10 percent compliance margin (with deterioration factor 

applied). To determine the NOx emission factors, we used certification data to determine the 

sales weighted average NOx for low emission technologies in each power bin. HC was then 

determined as the difference between the HC+NOx and the NOx emission factors. Because we 

are establishing the same standards for OB and PWC and because they use similar engines, we 

use the same HC+NOx emission factors and deterioration factors for both engine types. 

Because the final CO standard primarily acts as a cap on CO, the CO emission factors 

were determined based on the emission factors for existing low emission engines in each power 

bin. Fuel consumption factors were calculated in the same manner. Therefore, some differences 

are seen between the projected CO and BSFC factors for OB and PWC. No changes were made 

to the PM emission factors. Also, the existing deterioration factors for 4-stroke carbureted 

engines were applied to the control case (1.05 for HC, NOx, and CO). Table 3.4-3 presents the 

zero-hour OB/PWC emission factors for the control case. 

Table 3.4-3: Control Case Emission Factors for OB/PWC (g/kW-hr) 

Power Bin HC NOx CO

 OB PWC 

BSFC

 OB PWC 

0-2.2 kW 

2.3-4.5 kW 

4.6-8.2 kW 

8.3-11.9 kW 

12.0-18.6 kW 

18.7-29.8 kW 

29.9-37.3 kW 

37.4-55.9 kW 

55.9-74.6 kW 

74.7-130.5 kW 

130.6+ kW 

20.9 

22.1 

15.5 

11.6 

12.5 

10.2 

9.3 

9.2 

9.2 

9.2 

10.2 

4.8 

3.6 

5.6 

6.8 

4.3 

5.7 

5.9 

5.4 

5.4 

5.0 

3.7 

542 

357 

292 

248 

205 

189 

167 

169 

169 

173 

137 

640 

538 

243 

231 

218 

206 

206 

206 

206 

202 

178 

563 

560 

555 

552 

543 

528 

507 

471 

471 

415 

387 

563 

560 

555 

552 

543 

528 

507 

486 

486 

394 

380 

For sterndrive and inboards, we developed a new engine classification similar to the 

OB/PWC discussion above. SD/I engines at or below 373 kW are modeled to meet the final 

standard through the use of aftertreatment. HC and NOx emission factors are based on test data 

presented in Chapter 4 for SD/I engines equipped with catalysts. High performance engines 

have two tiers of standards that can be achieved through the use of engine-based technology. 

Although the standards distinguish between two power ranges for high-performance, a single 

3-28 
Emission Inventory 

weighted EF is used here. CO emission factors are based on meeting the final standard at the 

end of useful life (with the deterioration factor applied). No emission reductions are modeled for 

PM. The fuel consumption factor for fuel-injected 4-stroke SD/I engines is applied to the control 

case. Deterioration factors for catalyst-equipped engines are the same as those used in the 

NONROAD2005a model for catalyst-equipped large SI engines. Table 3.4-4 presents the zerohour emission factors and the accompanying deterioration factors for the control case. 

Table 3.4-4: Control Case EFs (g/kW-hr) and DFs for SD/I 

Engine Category 

HC NOx CO 

BSFC

EF DF EF DF EF DF 

kW #373 kW 1.80 1.64 1.60 1.15 55.0 1.36 345 

> 373 kW, Tier 1 11.80 1.69 6.70 1.38 207 1.81 362 

> 373 kW, Tier 2 8.58 1.69 6.80 1.38 207 1.81 362 

3.4.1.2 Controlled Evaporative Emission Rates 

Below, we present the effect of the final Phase 3 evaporative emission standards on hose 

permeation, tank permeation, diurnal, and running loss emission inventories. 

3.4.1.2.1 Hose Permeation 

Similar to the baseline case, hose permeation rates are based on g/m2/day and are 

modeled as a function of temperature. The fuel hose test procedures are based on Fuel CE10 as a 

test fuel. Based on data presented in Chapter 5, we would expect in-use emissions on gasolinebased E10 to be about half of the measured level on Fuel CE10. In addition, we believe that 

hose designed to meet the final 15 g/m2

/day standard on 10 percent ethanol fuel will permeate at 

least 50 percent less when gasoline is used. Therefore, we model permeation from hoses 

designed to meet 15 g/m2/day on Fuel CE10 to be 3.75 g/m2/day on gasoline at 23°C. Consistent 

with the baseline emission case, we weight the gasoline and E10 emission factors by our 

estimates of gasoline sales with and without ethanol added. The same correction factors used to 

account for the effect of ethanol on permeation are used in the control and baseline cases. 

Fill neck and vent hose containing vapor rather than liquid fuel are not subject to the final 

standards. No emission reductions are modeled for these hose types. In addition, no emission 

reductions are modeled for hose on handheld equipment used in cold weather applications (e.g. 

Class V chainsaws). 

3.4.1.2.2 Tank Permeation 

Similar to the baseline case, fuel tank permeation rates are based on units of g/m2

/day and 

are modeled as a function of temperature. We believe that fuel tanks using alternative materials 

3-29 
Final Regulatory Impact Analysis 

to meet the final 1.5 g/m2

/day standard on 10 percent ethanol fuel will typically permeate at least 

50 percent less when gasoline is used. Therefore, we model permeation from fuel tanks to be 

0.75 g/gal/day at 29°C on gasoline. Consistent with the baseline emission case, we weight the 

gasoline and E10 emission factors by our estimates of gasoline sales with and without ethanol 

added. The same correction factors used to account for the effect of ethanol on permeation are 

used in the control and baseline cases. 

One exception to the above discussion is metal tanks. For these fuel tanks, we do not 

include any emissions reductions from baseline. 

3.4.1.2.3 Diurnal 

We are not establishing a diurnal emission requirement for small nonroad SI equipment. 

Therefore, we do not model direct reductions in diurnal emissions. However, we are placing a 

limit on diffusion emissions. As a result, we set the diffusion multiplier to 1.0 for all nonhandheld Small SI equipment for the control case. Note that this multiplier was already set to 

1.0 for handheld equipment in the baseline case. This is equivalent to applying a 32 percent 

reduction to the diurnal emission factors. 

In the control case for marine SI engines, we model portable fuel tanks as having 90 

percent lower diurnal emissions than an open vent system. Also, we set the diffusion multiplier 

to 1.0 because the tanks would be sealed. Presumably, the diurnal temperature cycles would 

build some pressure in the fuel tank causing hydrocarbons to be released when the tank is 

opened. Therefore, we do not model these tanks as having zero diurnal emissions. For PWC, we 

use the baseline scenario of sealed systems with a 1.0 psi pressure relief valve. For installed fuel 

tanks, we model a 60 percent reduction due to a carbon canister in the fuel line with passive 

purge. This reduction is based on data presented in Chapter 5. As in the baseline case, no 

diffusion is modeled for PWC and installed fuel tanks. 

3.4.1.2.4 Running Loss 

For Class I engines, we believe that the final running loss control requirement will be met 

by routing vapor from the fuel take to the engine air intake system. Therefore, all vapor 

generated in the fuel tank should be consumed by the engine, thereby eliminating running loss 

emissions. However, there may be some inefficiencies in the system such as vapor escaping out 

the intake at idle. Therefore, we model the running loss emission reduction as only 90 percent. 

For Class II equipment, we believe that some equipment will inherently meet the final standard 

because they will have low enough temperature fluctuation in the fuel tanks during operation to 

certify by design. Based on the data presented in Chapter 5 on fuel tank temperatures during 

operation, we estimate an 80 percent reduction in running loss for Class II equipment. 

3.4.1.3 Controlled Exhaust and Evaporative Inventory Results for THC, VOC, 

NOx, PM2.5, PM10, CO and SO2 

Tables 3.4-5 presents the 50-state controlled emission inventories for small nonroad SI 

3-30 
Emission Inventory 

engines. Tables 3.4-6 provides the same information for marine SI engines. 

Table 3.4-5: Controlled 50-State Annual Exhaust and Evaporative Emissions for 

Small Nonroad Spark-Ignition Engines (short tons) 

Year THC VOC NOx PM2.5 PM10 CO 

2002 1,064,625 1,047,374 106,804 23,382 25,416 15,091,835 

2003 1,026,922 1,009,822 106,852 23,480 25,522 14,351,829 

2004 963,709 945,601 106,610 23,483 25,525 13,690,337 

2005 886,524 867,081 106,847 23,417 25,453 12,923,819 

2006 825,413 804,926 109,233 23,498 25,541 12,252,479 

2007 768,239 747,552 109,439 23,804 25,874 11,711,607 

2008 713,266 694,712 111,235 24,335 26,451 10,861,441 

2009 669,782 653,584 116,329 24,882 27,045 9,992,801 

2010 646,659 631,851 118,376 25,402 27,611 9,623,727 

2011 618,463 604,977 107,135 25,888 28,139 9,427,359 

2012 573,611 562,317 96,222 26,364 28,445 9,240,448 

2013 535,035 525,722 86,623 26,832 28,747 9,125,886 

2014 509,895 501,985 81,011 27,291 29,071 9,107,104 

2015 495,565 488,517 76,412 27,747 29,473 9,135,515 

2016 486,951 480,492 73,517 28,202 29,896 9,201,411 

2017 484,102 477,989 72,202 28,655 30,336 9,298,167 

2018 485,460 479,510 71,768 29,107 30,795 9,415,010 

2019 488,969 483,092 71,822 29,558 31,259 9,543,762 

2020 493,763 487,905 72,175 30,009 31,727 9,679,462 

2021 499,618 493,736 72,848 30,460 32,198 9,820,562 

2022 506,071 500,141 73,667 30,911 32,671 9,964,572 

2023 512,988 506,990 74,592 31,362 33,146 10,110,794 

2024 520,130 514,054 75,564 31,813 33,622 10,258,216 

2025 527,386 521,227 76,578 32,265 34,098 10,406,862 

2026 534,763 528,516 77,629 32,718 34,576 10,557,631 

2027 542,202 535,864 78,700 33,173 35,055 10,709,373 

2028 549,676 543,246 79,782 33,627 35,534 10,861,555 

2029 557,179 550,657 80,875 34,081 36,013 11,014,081 

2030 564,711 558,094 81,977 34,535 36,492 11,166,921 

2031 572,261 565,549 83,086 34,990 36,971 11,319,980 

2032 579,823 573,015 84,197 35,444 37,450 11,473,166 

2033 587,396 580,492 85,312 35,898 37,929 11,626,453 

2034 594,978 587,978 86,429 36,353 38,408 11,779,824 

2035 602,567 595,471 87,547 36,807 38,887 11,933,276 

2036 610,167 602,974 88,669 37,261 39,366 12,086,826 

2037 617,776 610,486 89,795 37,716 39,845 12,240,473 

2038 625,391 618,003 90,922 38,170 40,324 12,394,188 

2039 633,010 625,525 92,051 38,625 40,803 12,547,962 

2040 640,633 633,050 93,181 39,079 41,282 12,701,792 

3-31 
Final Regulatory Impact Analysis 

Table 3.4-6: Controlled 50-State Annual Exhaust and Evaporative Emissions for 

Marine Spark-Ignition Engines (short tons) 

Year THC VOC NOx PM2.5 PM10 CO 

2002 906,318 931,132 46,311 15,092 16,404 2,472,251 

2003 873,287 896,969 49,694 14,417 15,670 2,407,992 

2004 836,493 858,916 53,397 13,679 14,869 2,346,538 

2005 796,279 817,340 57,862 12,886 14,007 2,266,733 

2006 756,781 776,480 63,366 12,090 13,142 2,170,374 

2007 717,924 736,303 67,730 11,311 12,295 2,103,059 

2008 680,702 697,795 73,894 10,553 11,470 2,007,804 

2009 644,330 660,187 82,123 9,824 10,678 1,885,970 

2010 593,432 607,656 84,822 8,832 9,600 1,808,304 

2011 543,080 555,760 85,353 7,891 8,577 1,755,638 

2012 495,189 506,468 85,673 7,035 7,647 1,707,370 

2013 452,028 462,066 85,732 6,275 6,820 1,664,442 

2014 412,280 421,190 85,609 5,577 6,062 1,624,423 

2015 376,203 384,108 85,334 4,951 5,381 1,587,889 

2016 342,807 349,793 84,890 4,376 4,756 1,553,983 

2017 312,281 318,441 84,279 3,856 4,191 1,523,443 

2018 285,067 290,507 83,468 3,399 3,695 1,496,863 

2019 259,742 264,519 82,546 2,978 3,237 1,472,528 

2020 238,704 242,957 81,398 2,640 2,869 1,452,196 

2021 219,826 223,621 80,081 2,341 2,545 1,433,655 

2022 203,027 206,427 78,657 2,081 2,262 1,417,440 

2023 188,065 191,121 77,197 1,851 2,012 1,403,195 

2024 175,954 178,752 75,802 1,673 1,818 1,391,146 

2025 166,147 168,751 74,424 1,534 1,668 1,380,739 

2026 157,943 160,391 73,057 1,419 1,542 1,371,913 

2027 151,063 153,384 71,713 1,323 1,438 1,364,592 

2028 145,397 147,624 70,421 1,247 1,355 1,358,936 

2029 140,670 142,822 69,236 1,185 1,288 1,354,638 

2030 136,990 139,083 68,639 1,137 1,236 1,353,989 

2031 134,079 136,124 68,339 1,099 1,194 1,355,439 

2032 131,797 133,803 68,148 1,067 1,160 1,357,905 

2033 130,067 132,045 68,038 1,043 1,134 1,361,273 

2034 128,766 130,723 67,985 1,024 1,113 1,365,343 

2035 127,853 129,798 67,975 1,010 1,098 1,370,010 

2036 127,275 129,212 68,009 1,001 1,088 1,375,199 

2037 126,952 128,888 68,077 995 1,081 1,380,822 

2038 126,816 128,753 68,174 991 1,077 1,386,805 

2039 126,828 128,769 68,302 989 1,075 1,393,116 

2040 126,959 128,906 68,461 989 1,075 1,399,715 

3-32 
Emission Inventory 

3.4.2 Controlled Hazardous Air Pollutant Estimates 

The final hydrocarbon emission standards for small nonroad and marine SI engines will 

also reduce toxic air pollutants. To calculate the controlled toxic air emission inventories, we 

multiplied the baseline hazardous air pollutant estimates (Section 3.2.2) by the ratio of control 

and baseline emission inventories (Section 3.2.1.4 and 3.4.1.3, respectively) for VOC or PM, as 

appropriate. More specifically, we used the VOC ratio for all toxic pollutant species that are 

found in the gas phase. The gas phase pollutants are all the species described below, except for 

naphthalene and the polycyclic organic matter (POM) compounds that are found in both the gas 

and particulate phase. In these cases, we used the PM ratio to estimate the controlled 

inventories. 

Controlled inventories were calculated for the seven major types of air toxic emissions: 

benzene, formaldeyde, acetaldehyde, 1,3-butadiene, acrolein, naphthalene, and 15 other 

compounds grouped together as POM for this analysis.e Table 3.4-7 presents the 50-state 

controlled inventories, respectively, small nonroad SI engines. Table 3.4-8 provides the same 

information for marine SI engines. 

Table 3.4-7: Controlled 50-State Air Toxic Emissions for 

Small Nonroad Spark-Ignition Engines (short tons) 

Year Benzene 

1,3 

Butadiene 

Formaldehyde Acetaldehyde Acrolein Naphthalene POM 

2002 35,086 5,561 8,664 2,900 505 447 97 

2020 15,413 2,504 4,189 2,015 210 620 128 

2030 17,577 2,859 4,784 2,300 240 718 147 

Table 3.4-8: Controlled 50-State Air Toxic Emissions for 

Marine Spark-Ignition Engines (short tons) 

Year Benzene 

1,3 

Butadiene 

Formaldehyde Acetaldehyde Acrolein Naphthalene POM 

2002 23,110 2,053 2,153 1,543 211 37 31 

2020 4,453 390 273 418 14 19 7 

2030 2,582 216 151 234 8 9 3 

e

 The 15 POMs summarized in this chapter are acenapthylene, anthracene, benz(a)anthracene, 

benzo(a)pyrene, benzo(b)fluoranthene, benzo(g,h,i)perylene, beno(k)fluoranthene, chrysene, dibenzo(a,h)anthracene, 

fluoranthene, fluorene, indeno(1,2,3-c,d)-pyrene, phenanthrene, and pyrene. 

3-33 
Final Regulatory Impact Analysis 

3.5 Projected Emissions Reductions from the Final Rule 

This section presents the projected total emission reductions associated with the final 

Phase 3 standards. We calculated the reductions by subtracting the baseline inventories from 

Section 3.2 by the controlled inventories from Section 3.4. 

3.5.1 Results for THC, VOC, NOx, PM2.5, PM10, and CO

 Tables 3.5-1 presents the 50-state exhaust and evaporative emission inventories and 

percent reductions, respectively, for small nonroad SI engines. Tables 3.5-2 provides the same 

information for marine SI engines. Tables 3.5-3 summarizes the combined emission reductions 

for the final rule. The earliest Phase 3 evaporative standards for small nonroad SI engines begin 

in 2008. Similar final evaporative standards affect Marine SI engines one year later. Therefore 

the emission reductions are shown beginning in 2008 for small nonroad SI engines and 2009 for 

Marine SI engines. Figures 3.5-1 though 3.5-5 show the combined baseline, controlled, and by 

contrast the reduction emission inventories over time for small nonroad and Marine SI engines. 

3-34 
Table 3.5-1: Total 50-State Annual Exhaust and Evaporative Emission Reductions 

for Small Spark-Ignition Engines (short tons) 

Year 

THC VOC NOx PM2.5 PM10 

Tons % Tons % Tons % Tons % Tons % Tons 

2008 5,298 1 5,298 1 0 0 0 0 0 0 

2009 12,306 2 12,306 2 0 0 0 0 0 0 2010 19,103 3 19,103 3 0 0 0 0 0 0 2011 45,157 7 44,381 7 12,289 10 0 0 0 0 141

2012 92,055 14 89,426 14 24,598 20 195 1 212 1 338

2013 136,293 20 131,817 20 35,882 29 385 1 419 1 518

2014 169,739 25 163,834 25 43,389 35 546 2 594 2 644

2015 193,479 28 186,614 28 49,983 40 632 2 687 2 743

2016 212,274 30 204,672 30 54,951 43 697 2 758 2 818

2017 225,797 32 217,669 32 58,371 45 745 3 810 3 871

2018 235,483 33 226,988 33 60,933 46 776 3 843 3 909

2019 243,315 33 234,523 33 63,024 47 800 3 870 3 939

2020 249,991 34 240,948 34 64,827 47 820 3 892 3 966

2021 255,636 34 246,382 34 66,312 48 838 3 911 3 988

2022 260,711 34 251,271 34 67,650 48 854 3 928 3 1,008

2023 265,345 34 255,737 34 68,883 48 868 3 943 3 1,026

2024 269,770 34 260,002 34 70,072 48 881 3 958 3 1,043

2025 274,107 34 264,185 34 71,228 48 894 3 972 3 1,060

2026 278,455 34 268,375 34 72,374 48 908 3 987 3 1,077

2027 282,769 34 272,533 34 73,509 48 922 3 1,002 3 1,094

2028 287,060 34 276,668 34 74,635 48 936 3 1,017 3 1,110

2029 291,328 34 280,782 34 75,753 48 949 3 1,032 3 1,127

2030 295,576 34 284,876 34 76,863 48 963 3 1,047 3 1,143

2031 299,808 34 288,955 34 77,967 48 977 3 1,062 3 1,159

2032 304,033 34 293,027 34 79,068 48 990 3 1,076 3 1,176

2033 308,250 34 297,091 34 80,167 48 1,004 3 1,091 3 1,192

2034 312,460 34 301,148 34 81,264 48 1,018 3 1,106 3 1,208

2035 316,665 34 305,201 34 82,359 48 1,031 3 1,121 3 1,224

2036 320,862 34 309,246 34 83,450 48 1,045 3 1,136 3 1,241

2037 325,052 34 313,284 34 84,537 48 1,059 3 1,151 3 1,257

2038 329,238 34 317,318 34 85,623 48 1,072 3 1,166 3 1,273

2039 333,421 35 321,349 35 86,708 49 1,086 3 1,181 3 1,289

2040 337,602 35 325,379 35 87,792 49 1,100 3 1,195 3 1,305
Table 3.5-2: Total 50-State Annual Exhaust and Evaporative Emission Reductions 

for Marine Spark-Ignition Engines (short tons) 

Year 

THC VOC NOx PM2.5 PM10 

Tons % Tons % Tons % Tons % Tons % Tons 

2009 1,400 0 1,400 0 0 0 0 0 0 0 2010 18,748 3 19,245 3 2,318 3 317 3 344 3 15

2011 37,670 6 38,656 7 5,163 6 634 7 689 7 33

2012 58,252 11 59,723 11 7,989 9 948 12 1,031 12 50

2013 78,654 15 80,605 15 10,796 11 1,259 17 1,369 17 682014 98,886 19 101,313 19 13,588 14 1,567 22 1,703 22 852015 118,974 24 121,873 24 16,369 16 1,872 27 2,035 27 102

2016 138,843 29 142,207 29 19,131 18 2,173 33 2,362 33 119

2017 158,386 34 162,207 34 21,879 21 2,468 39 2,683 39 136

2018 177,535 38 181,801 38 24,617 23 2,756 45 2,996 45 153

2019 196,122 43 200,818 43 27,340 25 3,034 50 3,298 50 170

2020 212,471 47 217,524 47 30,128 27 3,269 55 3,553 55 185

2021 227,798 51 233,178 51 32,981 29 3,485 60 3,788 60 201

2022 242,345 54 248,030 55 35,822 31 3,688 64 4,008 64 216

2023 255,886 58 261,851 58 38,605 33 3,875 68 4,212 68 231

2024 267,248 60 273,428 60 41,250 35 4,023 71 4,373 71 245

2025 277,049 63 283,400 63 43,803 37 4,146 73 4,506 73 259

2026 285,828 64 292,329 65 46,286 39 4,256 75 4,626 75 272

2027 293,743 66 300,379 66 48,689 40 4,355 77 4,734 77 285

2028 300,755 67 307,503 68 50,990 42 4,440 78 4,826 78 297

2029 307,097 69 313,944 69 53,151 43 4,516 79 4,909 79 309

2030 312,636 70 319,573 70 54,696 44 4,582 80 4,981 80 317

2031 317,588 70 324,609 70 55,921 45 4,642 81 5,046 81 324

2032 322,039 71 329,140 71 57,018 46 4,698 81 5,107 81 330

2033 326,092 71 333,265 72 58,015 46 4,749 82 5,162 82 335

2034 329,826 72 337,067 72 58,937 46 4,797 82 5,214 82 340

2035 333,261 72 340,565 72 59,802 47 4,841 83 5,262 83 345

2036 336,417 73 343,778 73 60,611 47 4,882 83 5,306 83 350

2037 339,371 73 346,786 73 61,377 47 4,920 83 5,348 83 354

2038 342,183 73 349,649 73 62,104 48 4,957 83 5,388 83 358

2039 344,878 73 352,395 73 62,793 48 4,993 83 5,427 83 362

2040 347,477 73 355,043 73 63,445 48 5,027 84 5,464 84 365
Table 3.5-3: Total 50-State Annual Exhaust and Evaporative Emission Reductions 

for Small Nonroad and Marine Spark-Ignition Engines (short tons) 

Year 

THC VOC NOx PM2.5 PM10 

Tons % Tons % Tons % Tons % Tons % Tons 

2008 5,298 0 5,298 0 0 0 0 0 0 0 2009 13,706 1 13,706 1 0 0 0 0 0 0 2010 37,851 3 38,348 3 2,318 1 317 1 344 1 15

2011 82,827 7 83,037 7 17,451 8 634 2 689 2 174

2012 150,307 12 149,149 12 32,587 15 1,143 3 1,243 3 389

2013 214,947 18 212,422 18 46,679 21 1,644 5 1,787 5 586

2014 268,625 23 265,147 22 56,977 25 2,113 6 2,297 6 730

2015 312,454 26 308,487 26 66,353 29 2,504 7 2,722 7 846

2016 351,117 30 346,879 29 74,082 32 2,870 8 3,120 8 938

2017 384,183 33 379,875 32 80,250 34 3,213 9 3,493 9 1,007

2018 413,019 35 408,789 35 85,550 36 3,532 10 3,839 10 1,0622019 439,437 37 435,340 37 90,363 37 3,834 11 4,168 11 1,1102020 462,463 39 458,472 39 94,954 38 4,089 11 4,444 11 1,1522021 483,433 40 479,560 40 99,293 39 4,323 12 4,698 12 1,189

2022 503,056 42 499,301 41 103,472 40 4,541 12 4,936 12 1,224

2023 521,231 43 517,588 43 107,488 41 4,743 13 5,155 13 1,257

2024 537,018 44 533,430 44 111,322 42 4,905 13 5,331 13 1,288

2025 551,156 44 547,584 44 115,031 43 5,040 13 5,479 13 1,319

2026 564,282 45 560,704 45 118,660 44 5,164 13 5,613 13 1,349

2027 576,512 45 572,913 45 122,198 45 5,277 14 5,736 14 1,379

2028 587,814 46 584,171 46 125,625 46 5,376 14 5,843 14 1,408

2029 598,426 46 594,726 46 128,904 46 5,465 14 5,940 14 1,436

2030 608,211 46 604,449 46 131,559 47 5,545 14 6,027 14 1,461

2031 617,396 47 613,565 47 133,888 47 5,619 14 6,107 14 1,484

2032 626,072 47 622,167 47 136,087 47 5,688 14 6,183 14 1,506

2033 634,342 47 630,356 47 138,182 47 5,753 14 6,253 14 1,528

2034 642,286 47 638,215 47 140,201 48 5,814 14 6,320 14 1,549

2035 649,926 47 645,766 47 142,161 48 5,872 14 6,383 14 1,570

2036 657,279 47 653,024 47 144,061 48 5,927 14 6,442 14 1,591

2037 664,423 47 660,069 47 145,914 48 5,979 14 6,499 14 1,611

2038 671,421 47 666,967 47 147,727 48 6,029 14 6,554 14 1,631

2039 678,299 47 673,744 47 149,501 48 6,079 14 6,607 14 1,651

2040 685,079 47 680,422 47 151,237 48 6,127 14 6,660 14 1,671

. 
Final Regulatory Impact Analysis 

3-38 

Figure 3.5-1: 50-State Annual THC Exhaust and Evaporative Emissions for Small SI and 

Marine SI Engines 

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

2000 2005 2010 2015 2020 2025 2030 2035 2040

Year 

Tons /Year 

Baseline

Controlled

Figure 3.5-2: 50-State Annual VOC Exhaust and Evaporative Emissions for 

Small SI and Marine SI Engines 

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

2000 2005 2010 2015 2020 2025 2030 2035 2040

Year 

Tons /Year 

Baseline

Controlled
Emission Inventory 

3-39 

Figure 3.5-2: 50-State Annual NOx Exhaust Emissions for Small SI and Marine SI 

Engines 

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

2000 2005 2010 2015 2020 2025 2030 2035 2040

Year 

Tons /Year 

Baseline

Controlled

Figure 3.5-3: 50-State Annual PM2.5 Exhaust Emissions for Small SI and 

Marine SI Engines 

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

2000 2005 2010 2015 2020 2025 2030 2035 2040

Year 

Tons /Year 

Baseline

Controlled
Final Regulatory Impact Analysis 

Figure 3.5-4: 50-State Annual PM10 Emissions for Small SI and Marine SI 

Engines 

0

10,000

20,000

30,000

40,000

50,000

60,000

2000 2005 2010 2015 2020 2025 2030 2035 2040

Year 

Tons /Year 

Baseline

Controlled

Figire 3.5-5: 50-State CO Exhaust Emission for Small SI and 

Marine SI Engines 

0

2,000,000

4,000,000

6,000,000

8,000,000

10,000,000

12,000,000

14,000,000

16,000,000

18,000,000

20,000,000

2000 2005 2010 2015 2020 2025 2030 2035 2040

Year 

Tons 

Baseline

Controlled

3-40 
Emission Inventory 

3.5.2 Results for Hazardous Air Pollutants

 Table 3.5-4 presents the 50-state exhaust and evaporative hazardous air pollutant 

emission reductions for small nonroad SI engines that are expected as a result of the final 

standards. Table 3.5-5 provides the same information for marine SI engines. Table 3.5-6 

summarizes the combined hazardous air pollutant reductions for the final rule. These results are 

displayed for 2020 and 2030, when most or all of the engines subject to the standards are 

represented in the respective fleets. 

3-41 
Table 3.5-4: 50-State Air Toxic Emission Reductions for 

Small Nonroad Spark-Ignition Engines (short tons)

Year Benzene 1,3 Butadiene Formaldehyde Acetaldehyde Acrolein Napthalen

Tons % Tons % Tons % Tons % Tons % Tons 

2020 7,803 34 965 28 1,614 28 777 28 81 28 17 

2030 9,200 34 1,140 29 1,907 29 917 29 96 29 21 

Table 3.5-5: 50-State Air Toxic Emission Reductions for 

Marine Spark-Ignition Engines (short tons)

Year Benzene 1,3 Butadiene Formaldehyde Acetaldehyde Acrolein Napthalen

Tons % Tons % Tons % Tons % Tons % Tons 

2020 3,964 47 373 49 261 49 400 49 13 49 23 

2030 5,893 70 535 71 374 71 577 71 19 71 37 

Table 3.5-6: 50-State Air Toxic Emission Reductions for 

Small Nonroad and Marine Spark-Ignition Engines (short tons)

Year Benzene 1,3 Butadiene Formaldehyde Acetaldehyde Acrolein Napthalen

Tons % Tons % Tons % Tons % Tons % Tons 

2020 11,767 37 1,338 32 1,875 30 1,176 33 94 30 41 

2030 15,093 43 1,675 35 2,281 32 1,494 37 115 32 57 
Emission Inventory 

3.6 Emission Inventories Used for Air Quality Modeling 

This section briefly summaries the methodology we used for air quality modeling 

purposes and to develop the emission inventories for that modeling. It also describes the 

changes to our emission inventory modeling inputs and resulting emission inventories that were 

made between the preliminary baseline and control scenarios used for the air quality modeling, 

and the updated final baseline and control scenarios for the final Phase 3 rule. These differences 

often occur because the emission inputs for the air quality modeling are required early in the 

analytical process to ensure there is adequate time to complete the analysis and incorporate the 

results into the rulemaking. Given that lead time requirement, air quality modeling is often 

based on analytical methods and inputs that may be superceded, or on a control scenario that 

does not specifically match the final set of emission standards. 

3.6.1 General Description of the Air Quality Modeling 

Air quality modeling was performed for the 48 contiguous states and the District of 

Columbia to estimate the effect of the final rule on future annual fine particulate matter (PM2.5) 

concentrations, 8-hour ozone concentrations, and visibility levels. The analysis was performed 

for calendar years 2002, 2020, and 2030 using the Community Multiscale Air Quality (CMAQ) 

model. The model simulates the multiple physical and chemical processes involved in the 

formation, transport, and destruction of fine particulate and ozone. 

The air quality modeling for the final rule was predominately taken directly from the 

work performed for EPA’s recent final rulemaking to control air emissions from locomotive 

engines and marine compression-ignition engines less than 20 liters per cylinder (the 

locomotive/marine rule). This approach was adopted to ensure that the air quality modeling for 

this rule included the effects all EPA’s most recent air pollution control regulations and to 

conserve resources by taking advantage of the existing inventory preparation (i.e., input files), 

analytical methods, and results. 

More specifically, we used the locomotive/marine rule’s “control” scenario as our starting 

point. The resulting baseline for the Phase 3 final rule was then modified to include more recent 

modeling updates for small nonroad and marine SI engines based on the NONROAD2005d core 

model and a set of input files that closely matches those used in this final rule. (The differences 

in the input files used in the preliminary inventories and those for the final rule, which also used 

NONROAD 2005d core model, are specifically described later in this section.) For air quality 

modeling purposes, the nonroad model was executed within the framework of EPA’s National 

Mobile Inventory Model (NMIM) that links a county-level database to the model and collates the 

output into a single database table. The resulting NMIM inventory estimates for nonroad and 

marine SI engines account for local differences in fuel characteristics and temperatures. By 

contrast, if NONROAD2005d is run as a stand alone model, results are based on a somewhat less 

accurate, but much less resource intensive approach that uses national average daily temperatures 

and fuel characteristics. 

3-43 
Final Regulatory Impact Analysis 

The NMIM emissions inventory methodology and results for the highway vehicles and all 

nonroad sources (including those for small nonroad and marine SI engines) that were used in the 

air quality assessment are in the docket for this final rule. 24 

3.6.2 Methodology for Comparing the Preliminary Air Quality Emission Inventories and 

the Final Inventories 

The simplest method for comparing the preliminary emission inventories and the 

inventories represented in the final rule is to compare the emission results from using the 

NONROAD2005d core model with the national average inputs for temperature and fuel that 

reflect the modeling assumptions for the preliminary and final rule inventories. This is possible 

because of the similarities in the underlying use of the NONROAD2005d model. More 

specifically, even though the two modeling approaches, i.e., NMIM and the stand alone 

NONROAD2005 model, use different temperature and fuel characteristics, the computational 

method is the same.f This consistency means that the results of the two modeling approaches 

will be proportional in nature, i.e., the relative changes in the inventories will be similar. Also, 

as is explained in more detail later, the other basic modeling scenario inputs, e.g., emission 

factors and deterioration rates, are nearly identical. Taken together, the modeling results from 

using the NONROAD2005d model with national average inputs for temperature and fuels will 

closely mirror the differences in inventories produced with NMIM. This avoids the more time 

and resource intensive approach of rerunning the NMIM model for the final rule scenarios, while 

still providing a good comparison of the differences in the absolute inventories, i.e., tons, and 

more importantly for air quality considerations, the percent reduction between the baseline and 

control cases. Therefore, the comparisons of the preliminary and final emission scenarios that 

are presented in the following sections are based on comparing 50-state inventories using the 

nonroad model with national average inputs. 

3.6.3 Comparison of the Baseline Scenario Emission Inventories 

As described in Section 3.2., the final emission inventories for the Phase 3 rule are based 

on the use of a special version of the nonroad model, i.e., NONROAD2005d. Similarly, the 

preliminary emission inventories for air quality modeling were also constructed using the same 

version NONROAD2005d core model. Therefore, the only difference between the preliminary 

and final baseline scenarios are the modeling inputs. These differences and a comparison of the 

respective inventory results are presented below. 

3.6.3.1 Differences Between the Preliminary and Final Baseline Scenarios 

The modeling inputs for the final baseline scenario are described in Section 3.2.1. The 

only difference in the inputs for small nonroad SI engines between the preliminary and the final 

baseline scenarios is that the preliminary results did not include correction of the running loss 

f

 The difference between the preliminary emission inventories using NMIM and final rule emission 

inventories using NONROAD2005d is that the NMIM results, which use county-level data for temperatures and fuel 

characteristics, are generally 10-15 percent greater depending on the pollutant. 

3-44 
Emission Inventory 

emission factors for Class 1 snowblowers to account for cold weather applications as described 

in Section 3.2.1.1.1, number 8. There were no differences in the inputs for marine SI engines. 

3.6.3.2 Comparison of Preliminary and Final Baseline Emission Inventories 

Table 3.6-1 compares the preliminary and final 50-state baseline scenario inventories for 

small nonroad and marine SI engines. As shown, the differences in the baseline scenarios are 

insignificant. 

3-45 
Table 3.6-1: Comparison of 50-State Baseline Scenario Emissions for

Preliminary Air Quality Modeling and Final Rule

Applications Year 

VOC [short tons] NOx [short tons] PM2.5 

Final Preliminary Difference Final Preliminary Difference Final Preli

Small Nonroad SI Subject to the Final rule 

2020 728,853 729,235 (382) 137,002 137,002 0 30,009 

2030 842,970 843,410 (440) 158,840 158,840 0 34,535 

 Marine SI 2020 460,481 460,481 0 111,525 111,525 0 5,908 

2030 458,656 458,656 0 123,335 123,335 0 5,719 

Total 2020 1,189,334 1,189,716 (382) 248,527 248,527 0 35,917 

2030 1,301,626 1,302,066 (440) 282,175 282,175 0 40,254 
Emission Inventory 

Table 3.6-1 (Cont’d) 

Comparison of 50-State Baseline Scenario Emissions for 

Preliminary Air Quality Modeling and Final Rule 

Applications Year 

PM10 [short tons] CO [short tons] 

Final Preliminary Difference Final Preliminary Difference 

Small Nonroad 

SI Subject to the 

Final rule 

2020 32,618 32,618 0 10,645,870 10,645,870 0 

2030 37,538 37,538 0 12,310,505 12,310,505 0

 Marine SI 2020 6,422 6,422 0 1,638,114 1,638,114 0 

2030 6,217 6,217 0 1,671,627 1,671,627 0 

Total 2020 39,041 39,041 0 12,283,983 12,283,983 0 

2030 43,755 43,755 0 13,982,132 13,982,132 0 

3.6.4 Comparison of the Control Scenario Emission Inventories 

As noted above, the preliminary and final emission inventories for the Phase 3 rule are 

based on the same version of the nonroad model, i.e., NONROAD2005d. Therefore, the only 

difference between the scenarios are the modeling inputs. These differences and a comparison 

of the respective inventory results are presented below. 

3.6.4.1 Differences Between the Preliminary and Final Control Scenarios 

The modeling inputs for the final control scenario are described in Section 3.4.1. The 

only difference in the inputs for small nonroad SI engines between the preliminary and the final 

control scenarios is that the preliminary results excluded the following: 

1.	 Update of the Phase 3 Class II zero-hour emission factor for CO from 391.13 to 

431.72 g/kW-hr (321.9 g/hp-hr); and 

2.	 Update of the Phase 3 Class II brake specific fuel consumption values from 0.666 

to 0.735 lb/hp-hr to reflect a lower use of electronic fuel injection systems. 

For marine SI engines, the only difference in the inputs between the preliminary and the 

final control scenarios is that the preliminary results excluded the following: 

1.	 Revised several of the HC and NOx emission factors for outboards, personal 

watercraft, and sterndrive/inboards; 

2.	 Revised the Phase 3 standard phase-in dates for high performance 

sterndrive/inboards (>600 hp); 

3.	 Delayed by one year the implementation dates for outboards, personal watercraft, 

and stern drive/inboards; and 

3-47 
Final Regulatory Impact Analysis 

4.	 Delayed by one year the implementation of diurnal Phase 3 controls for portable 

fuel tanks to 2010 and installed fuel tanks to 2011. 

3.6.4.2 Comparison of Preliminary and Final Control Emission Inventories 

Table 3.6-2 compares the preliminary and final 50-state control scenario inventories for 

small nonroad and marine SI engines. As shown, the difference in the control scenarios are 

insignificant. 

3-48 
Table 3.6-2: Comparison of 50-State Control Scenario Emissions for

Preliminary Air Quality Modeling Scenario and Final Rule (Tons/Year)

Applications Year 

VOC [short tons] NOx [short tons] PM

Final Preliminary Difference Final Preliminary Difference Final Pre

Small Nonroad SI Subject to the Final rule 

2020 487,905 487,663 242 72,175 72,175 0 29,189 

2030 558,094 557,805 289 81,977 81,977 0 33,572 

 Marine SI 2020 242,957 241,216 1,741 81,398 81,162 236 2,640 

2030 139,083 136,650 2,433 68,639 68,538 101 1,137 

Total 2020 730,862 728,879 1,983 153,573 153,336 237 31,829 

2030 697,177 694,455 2,722 150,616 150,515 101 34,709 
Final Regulatory Impact Analysis 

Table 3.6-2 (Cont’d) 

Comparison of 50-State Control Scenario Emissions for 

Preliminary Air Quality Modeling and Final Rule 

Applications Year 

PM10 [short tons] CO [short tons] 

Final Preliminary Difference Final Preliminary Difference 

Small Nonroad 

SI Subject to the 

Final rule 

2020 31,727 31,727 0 9,679,462 9,029,001 650,461 

2030 36,492 36,492 0 11,166,921 10,393,508 773,413

 Marine SI 2020 2,869 2,869 0 1,452,196 1,447,553 4,643 

2030 1,236 1,236 0 1,353,989 1,345,079 8,910 

Total 2020 34,596 34,596 0 11,131,658 10,476,554 655,104 

2030 37,728 37,728 0 12,520,910 11,738,587 782,323 

3.6.5 Comparison of the Emission Reduction Inventories 

Table 3.6-3 compares the emission reductions for preliminary and final 50-state 

inventories for small nonroad and marine SI engines. As shown, the differences are 

insignificant. 

3-50 
Table 3.6-3: Comparison of 50-State Emissions Reductions for

Preliminary Air Quality Modeling Scenario and Final Rule (Tons/Year)

Applications Year 

VOC [short tons] NOx [short tons] PM

Final Preliminary Difference Final Preliminary Difference Final P

Small Nonroad SI Subject to the Final rule 

2020 240,948 241,572 (624) 64,827 64,827 0 820 

2030 284,876 285,605 (729) 76,863 76,863 0 963 

 Marine SI 2020 217,524 219,265 (1,741) 30,128 30,364 (236) 1,287 

2030 319,573 322,006 (2,433) 54,696 54,797 (101) 3,269 

Total 2020 458,472 460,837 (2,365) 94,955 95,191 (236) 4,082 

2030 604,449 607,611 (3,162) 131,559 131,660 (101) 5,545 
Final Regulatory Impact Analysis 

Table 3.6-3 (Cont’d) 

Comparison of 50-State Emission Reductions for 

Preliminary Air Quality Modeling and Final Rule 

Applications Year 

PM10 [short tons] CO [short tons] 

Final Preliminar 

y 

Difference Final Preliminar 

y 

Difference 

Small Nonroad 

SI Subject to the 

Final rule 

2020 892 892 0 966,407 1,616,868 (650,461) 

2030 1,047 1,047 0 1,143,584 1,916,997 (773,413)

 Marine SI 2020 3,553 3,553 0 185,917 190,560 (4,643) 

2030 4,981 4,981 0 317,638 326,548 (8,910) 

Total 2020 4,445 4,445 0 1,152,325 1,807,428 (655,103) 

2030 6,028 6,028 0 1,461,222 2,243,545 (782,323) 

3-52 
Emission Inventory 

Chapter 3 References 

1. “NONROAD2005a Emissions Inventory Model and Documentation,” Memorandum and attachment from 

Richard S. Wilcox to Docket EPA-HQ-OAR-2004-0008, U.S. Environmental Protection Agency, Office of 

Transportation and Air Quality, Ann Arbor, Michigan, February 5, 2007. Docket Identification EPA-HQ-OAR2004-0008-0517. 

2. “NONROAD2005d missions Inventory Model,” Memorandum and attachment from Richard S. Wilcox to Docket 

EPA-HQ-OAR-2004-0008, U.S. Environmental Protection Agency, Office of Transportation and Air Quality, Ann 

Arbor, Michigan, February 5, 2007. Docket Identification EPA-HQ-OAR-2004-0008-0719. 

3. “Updates to Phase 2 Technology Mix, Emission Factors, and Deterioration Rates for Spark-Ignition Nonroad 

Nonhandheld Engines at or below 19 Kilowatts for the NONROAD Emissions Inventory Model,” Memorandum 

from Phil Carlson to Docket EPA-HQ-OAR-2004-0008, U.S. Environmental Protection Agency, Office of 

Transportation and Air Quality, Ann Arbor, Michigan, March 6, 2000. Docket Identification EPA-HQ-OAR-2004-

0008-0543. 

4. “Phase 3 Technology Mix, Emission Factors, and Deterioration Rates for Spark-Ignition Nonroad Nonhandheld 

Engines at or below 19 Kilowatts for the NONROAD Emissions Inventory Model,” Memorandum from Phil Carlson 

to Docket EPA-HQ-OAR-2004-0008, U.S. Environmental Protection Agency, Office of Transportation and Air 

Quality, Ann Arbor, Michigan, May 21, 2008. Docket Identification EPA-HQ-OAR-2004-0008-0842. 

5. “Exhaust Emission Factors for Nonroad Engine Modeling; Spark-Ignition, Report No. 010e,” U.S. Environmental 

Protection Agency, Office of Transportation and Air Quality, Ann Arbor, Michigan, EPA420-R-05-019, December 

2005. Docket Identification EPA-HQ-OAR-2004-0008-0398. 

6. “Updates to Technology Mix, Emissions Factors, Deterioration Rates, Power Distribution, and Fuel Consumption 

Estimates for SI Marine Engines in the NONROAD Emissions Inventory Model,” Memorandum from Michael 

Samulski to Docket EPA-HQ-OAR-2004-0008, U.S. Environmental Protection Agency, Office of Transportation 

and Air Quality, Ann Arbor, November 30, 2005. Docket Identification EPA-HQ-OAR-2004-0008-0361. 

7. “Nonroad Evaporative Emission Rates, Report No. 012c,” U.S. Environmental Protection Agency, Office of 

Transportation and Air Quality, Ann Arbor, Michigan, December 2005. Docket Identification EPA-HQ-OAR-2004-

0008-0362. 

8. “Modeling of Ethanol Blend Effects on Nonroad Fuel Hose and Tank Permeation - Updated,” Memorandum from 

Craig Harvey to Docket EPA-HQ-OAR-2004-0008, U.S. Environmental Protection Agency, Office of 

Transportation and Air Quality, Ann Arbor, Michigan, February 22, 2008. Docket Identification EPA-HQ-OAR2004-0008-0698. 

9. “Domenici-Barton Energy Policy Act of 2005,” 109th Congress, U.S. House of Representatives and U.S. Senate, 

July 26, 2005. Docket Identification EPA-HQ-OAR-2004-0008-0268. 

10. “Annual Energy Outlook 2007; With Projections to 2030, Table 11: Liquid Fuels Supply and Disposition," 

Energy Information Administration, U.S. Department of Energy, Report # DOE/EIA-0383(2007), 2007. 

Http://www.eia.doe.gov/oiaf/archive/aeo07/pdf/aeotab_11.pdf. Docket Identification EPA-HQ-OAR-2004-0008-

0695. 

11. “Annual Energy Outlook 2007; With Projections to 2030, Table 17: Renewable Energy, Consumption, by 

Sector and Source," Energy Information Administration, U.S. Department of Energy, Report # 

DOE/EIA-0383(2007), 2007. Http://www.eia.doe.gov/oiaf/archive/aeo07/pdf/aeotab_17.pdf. Docket Identification 

EPA-HQ-OAR-2004-0008-0696. 

3-53 
Final Regulatory Impact Analysis 

12. “Fuel and Oil Hoses,” Recommended Practice J30, Society of Automotive Engineers, June 1998. Docket 

Identification EPA-HQ-OAR-2004-0008-0176. 

13. “Personal Watercraft Fuel Systems,” Recommended Practice J2046, Society of Automotive Engineers, January, 

19, 2001. Docket Identification EPA-HQ-OAR-2004-0008-0179. 

14. “Marine Fuel Hoses,” Recommended Practice J1527, Society of Automotive Engineers, Revised February 1993. 

Docket Identification EPA-HQ-OAR-2004-0008-0177. 

15. “Handheld Fuel Lines,” email from William Guerry, representing Outdoor Power Equipment Institute, to Glenn 

Passavant and Mike Samulski, U.S. Environmental Protection Agency, Office of Transportation and Air Quality, 

Ann Arbor, Michigan, July 6, 2005. Docket Identification EPA-HQ-OAR-2004-0008-0126. 

16. Letter from Jim Hardin, Grady-White Boats, to Phil Carlson, U.S. Environmental Protection Agency, Office of 

Transportation and Air Quality, Ann Arbor, Michigan, July 25, 2006. Docket Identification EPA-HQ-OAR-2004-

0008-0437. 

17. "Permeation of Gasoline and Gasoline-Alcohol Fuel Blends Through High-Density Polyethylene Fuel Tanks 

with Different Barrier Technologies," D. Kathios and R. Ziff, SAE Paper 920164, 1992, Docket Identification 

EPA-HQ-OAR-2004-0008-0172. 

18. “List of 177 Pollutants in the Assessment,” National-Scale Air Toxics Assessment for 1999, U. S. 

Environmental Protection Agency, 2006. Http://www.epa.gov/ttn/atw/nata1999/177poll.html. 

19. “Comparison of Small Nonroad and Marine Spark-Ignition Emissions to Stationary and Other Mobile Source 

Emission Inventories,” Memorandum and attachment from Richard Wilcox, U.S. Environmental Protection Agency, 

Office of Transportation and Air Quality, Ann Arbor, Michigan, March 12, 2007. Docket Identification EPA-HQOAR-2004-0008-0540. 

20. “Technical Support Document: Preparation of Emissions Inventories for the 2002-Based Platform, Version 3, 

Criteria Pollutants,” U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research 

Triangle Point, North Carolina, January 2008. 

Http://www.epa.gov/scram001/reports/Emissions%20TSD%20Vol1_02-28-08.pdf. Docket Identification EPA-HQOAR-2004-0008-0699. 

21. “Regulatory Impact Analysis: Control of Emissions or Air Pollution from Locomotives and Marine 

Compression-Ignition Engines Less Than 30 Liters per Cylinder,” U.S. Environmental Protection Agency, Office of 

Transportation and Air Quality, Ann Arbor, Michigan, May 2008. EPA Report Number: EPA420-R-08-001a. 

22. “Control of Emissions From New Marine Compression-Ignition Engines at or Above 30 Liters per Cylinder,” 

Advanced Notice of Proposed Rulemaking, U.S. Environmental Protection Agency, Office of Transportation and 

Air Quality, Ann Arbor, Michigan, 72 Federal Register 69521, December 7, 2007. 

23. “Control of Hazardous Air Pollutants from Mobile Sources: Regulatory Impact Analysis,” U.S. Environmental 

Protection Agency, Office of Transportation and Air Quality, Ann Arbor, Michigan, February 2007. EPA Report 

Number: EPA420-R-07-002. 

24. “Electronic Media Supporting Development of Air Quality Modeling Emissions Inventories for the Small 

Nonroad and Marine Spark-Ignition Engine Final Rulemaking,” Memorandum and attachments from Harvey 

Michaels, U.S. Environmental Protection Agency, Office of Transportation and Air Quality, Ann Arbor, Michigan, 

July 22, 2008. Docket Identification EPA-HQ-OAR-2004-0008-0694. 

3-54 
Feasibility of Exhaust Emission Control 

CHAPTER 4: Feasibility of Exhaust Emission Control 

Section 213(a)(3) of the Clean Air Act presents statutory criteria that EPA must evaluate 

in determining standards for nonroad engines and vehicles including marine vessels. The 

standards must "achieve the greatest degree of emission reduction achievable through the 

application of technology which the Administrator determines will be available for the engines 

or vehicles to which such standards apply, giving appropriate consideration to the cost of 

applying such technology within the period of time available to manufacturers and to noise, 

energy, and safety factors associated with the application of such technology." This chapter 

presents the technical analyses and information that form the basis of EPA's belief that the 

exhaust emission standards are technically achievable accounting for all the above factors. 

The exhaust emission standards for Small SI engines and Marine SI engines are 

summarized in the Executive Summary. This chapter begins with a current state of technology 

for spark-ignition (SI) engines and the emission control technologies expected to be available for 

manufacturer and continues with a presentation of available emissions data on baseline 

emissions and on emission reductions achieved through the application of emission control 

technology. In addition, this chapter provides a description of new test procedures including 

not-to-exceed requirements. 

4.1 General Description of Spark-Ignition Engine Technology 

The two most common types of engines are gasoline-fueled engines and diesel-fueled 

engines. These engines have very different combustion mechanisms. Gasoline-fueled engines 

initiate combustion using spark plugs, while diesel fueled engines initiate combustion by 

compressing the fuel and air to high pressures. Thus these two types of engines are often more 

generally referred to as "spark-ignition" and "compression-ignition" (or SI and CI) engines, and 

include similar engines that use other fuels. SI engines include engines fueled with liquid 

petroleum gas (LPG) and compressed natural gas (CNG). 

4.1.1 Basics of Engine Cycles 

Spark ignition engines may be of two-stroke or four-stroke which refers to the number of 

piston strokes per combustion cycle. Handheld Small SI equipment typically use two-stroke 

engines while larger non-handheld equipment use four-stroke engines. Outboard and personal 

watercraft (OB/PWC) engines, until the advent of recent environmental regulations, were 

generally two-stroke engines. They are now a mix of two- and four-stroke engines. Sterndrive 

and inboard (SD/I) engines are primarily SI four-stroke engines. 

4.1.1.1 Two-Stroke Engines 

“Two-stroke” refers to the number of piston strokes per combustion cycle. These two 

strokes, compression and expansion, occur in one revolution of the crankshaft. During the 

4-1 
Final Regulatory Impact Analysis 

expansion stroke the piston moves downward. As the piston nears its lowest position, the intake 

and exhaust ports are opened. While these ports are open, a fresh charge of fuel and air is 

pushed into the cylinder which, in turn, helps force the burned gases from the previous cycle out 

of the exhaust port. During the compression stroke, the intake and exhaust ports close and the 

fresh charge is compressed. As the piston approaches its highest position, a spark-plug ignites 

the fresh charge to generate combustion. The force from the combustion acts on the piston to 

move it downward, thereby causing the expansion stroke and generating power. 

In traditional two-stroke engine designs, the engines are crankcase-scavenged and 

carbureted with intake and exhaust ports on the cylinder walls. The advantage of this engine 

design is simplicity (low number of moving parts) and a high power to weight ratio of the 

engine. In this design, the carburetor meters fuel into the intake air which is then routed to the 

crankcase. The motion of the drive shaft then pressurizes the charge. Oil is typically blended 

into the fuel to provide cylinder and reciprocating assembly lubrication. When the piston lowers, 

it exposes the intake port on the side of the cylinder wall which allows the pressurized fuel/air 

charge to enter the cylinder. At the same time, the exhaust port is exposed allowing burned 

gases to escape the cylinder. Because both ports are open at the same time, some of the fresh 

charge can exit the exhaust port. These fuel losses are known as “short-circuiting” or 

“scavenging” losses and can result in 25 percent or more of the fuel passing through the cylinder 

unburned. As the piston moves up, the intake and exhaust ports are covered and combustion is 

initiated. 

An emerging technology for reducing emissions and scavenging losses from two-stroke 

engines is direct-injection. This is used primarily on larger outboard and personal watercraft 

engines (37 kW and up) to meet exhaust emission standards. In a direct-injected engine, charge 

air is used to scavenge the exhaust gases. Once the exhaust valve closes, fuel is injected into the 

charge air and ignited with a spark-plug. Because the exhaust valve is closed during most or all 

of the injection event, short-circuiting losses are minimized. Also, because the fuel is not used to 

lubricate the crankcase, oil does not need to be blended into the fuel. As a result, much less oil is 

used. 

4.1.1.2 Four-Stroke Engines 

Four-stroke engines are used in many different applications. Virtually all gasolinepowered highway motorcycles, automobiles, trucks and buses are powered by four-stroke 

engines. Four-stroke engines are also common in off-road motorcycles, all-terrain vehicles 

(ATVs), boats, airplanes, and numerous nonroad applications such as lawn mowers, lawn and 

garden tractors, and generators, pressure washers and water pumps to name just a few. 

A “four-stroke” engine gets its name from the fact that the piston makes four passes or 

strokes in the cylinder to complete an entire cycle. The strokes are intake, compression, 

expansion or power, and exhaust. Two of the strokes are downward (intake & expansion) and 

two of the strokes are upward (compression & exhaust). The four strokes are completed in two 

revolutions of the crankshaft. Valves in the combustion chamber open and close to route gases 

into and out of the combustion chamber or create compression. 

4-2 
Feasibility of Exhaust Emission Control 

Figure 4.1-1: 4-Stroke Cycle 

The first step of the cycle is for an intake valve to open during the intake stroke allowing 

a mixture of air and fuel to be drawn into the cylinder while an exhaust valve is closed and the 

piston moves down the cylinder. The piston moves from top dead center (TDC) or the highest 

piston position to bottom dead center (BDC) or lowest piston position. This displacement of the 

piston draws air and fuel past the open intake valve into the cylinder. 

During the compression stroke, the intake valve closes and the momentum of the 

crankshaft moves the piston up the cylinder from BDC to TDC, compressing the air and fuel 

mixture. As the piston nears TDC, at the very end of the compression stroke, the air and fuel 

mixture is ignited by a spark plug and the air and fuel mixture begins to burn. As the air and fuel 

mixture burns, pressures and temperatures increase and the products of combustion expand in the 

cylinder, which causes the piston to move back down the cylinder, transmitting power to the 

crankshaft during the expansion or power stroke. Near the bottom of the expansion stroke, an 

exhaust valve opens and as the piston moves back up the cylinder, exhaust gases are pushed out 

through the exhaust valve to the exhaust manifold to complete the exhaust stroke, finishing a 

complete four-stroke cycle. 

4.1.2 Exhaust Emissions from Nonroad SI Engines 

Hydrocarbon (HC) and carbon monoxide (CO) emissions are products of incomplete 

combustion. The level of CO exhaust emissions is primarily a function of the air-to-fuel ratio at 

which an engine is operated. Hydrocarbon emissions formation mechanisms are somewhat more 

complex, and appear to be primarily related to: 

1.	 Quenching of the air/fuel mixture at the walls of the combustion chamber 

2.	 Filling of crevice volumes with the air/fuel mixture that remains unburned due to flame 

quenching at the entrance to the crevice 

3.	 Lubricant absorption and desorption of fuel compounds 

4.	 Partial combustion during an operating cycle or even complete misfiring of the air/fuel 

mixture during the cycle 

5.	 Entrainment and incomplete combustion of lubricant 

4-3 
Final Regulatory Impact Analysis 

As a result, a number of design and operational variables have an impact on HC 

emissions, including air-to-fuel ratio; combustion chamber design and geometry; homogeneity of 

the air/fuel charge; intake port geometry and the degree of induced air/fuel charge motion; 

ignition energy, dwell, and timing; the effectiveness of the cooling system; and oil consumption. 

NOx emissions from SI engines are primarily emissions of nitric oxide (NO). Nitrogen 

in the intake air reacts with oxygen at high temperatures primarily via the Zeldovich mechanism 

to form NO. Thus variables that impact combustion temperatures can have a significant impact 

on NO formation and NOx exhaust emissions. These include air-to-fuel ratio, spark timing and 

the quantity of residual exhaust gases carried over between engine firing cycles (either through 

external exhaust gas recirculation or inefficient cylinder scavenging). 

Particulate matter (PM) emissions from SI engines consists primarily of semi-volatile 

organic compounds from the engine lubricant together with elemental-carbon soot formed from 

pyrolysis of fuel and lubricant during combustion. 

4.1.2.1 Air-to-fuel ratio 

The calibration of engine air-to-fuel ratio affects torque and power output, fuel 

consumption (often indicated as Brake Specific Fuel Consumption or BSFC), engine 

temperatures, and emissions for SI engines. The effects of changing the air-to-fuel ratio on 

emissions, fuel consumption and torque (indicated as Brake Mean Effective Pressure or BMEP, 

which is torque corrected for engine volumetric displacement) are shown in Figure 3-1.1 

In the past, manufacturers have calibrated fuel systems of nonroad SI engines for rich 

operation. This was done in part to reduce the risk of lean misfire due to imperfect mixing of the 

fuel and air and variations in the air-fuel mixture from cylinder to cylinder. Rich operation at 

between approximately 12.5:1 and 13:1 air-to-fuel ratio also generally increased engine torque 

output (figure 4.1-1) and prevented lean air-to-fuel ratio excursions during application of 

transient loads to the engine. Rich operation also has been used to reduce piston, combustion 

chamber, cylinder and exhaust port temperatures, thus reducing the thermal load on the cooling 

system, a particularly important issue with air-cooled engines. Operation at air-to-fuel ratios 

richer than approximately 13:1 or 13.5:1 can limit the effectiveness of, or pose design challenges 

for, post-combustion catalytic exhaust emission controls for HC and CO emissions but work well 

for catalytic reduction of NOx. At the same time, because a rich mixture lacks sufficient oxygen 

for complete combustion, it results in increased fuel consumption rates and higher HC and CO 

emissions. 

As can be seen from the figure, the best fuel consumption rates occur when the engine is 

running lean of the stoichiometric air-to-fuel ratio (approximately 14.6:1 air-to-fuel ratio for 

typical gasolines), but lean operational limits are bounded by the onset of abnormal combustion 

(e.g., lean misfire and combustion knock), the ability to pick up load, and exhaust port 

temperatures (particularly with air-cooled engines). Many air-cooled engines are limited by 

heat-rejection to operation that starts approximately at stoichiometry for light loads, and is rich 

4-4 
Feasibility of Exhaust Emission Control 

of stoichiometry as load is increased. 

With the use of more advanced fuel systems, manufacturers would be able to improve 

control of the air-fuel mixture in the cylinder. This improved control allows for leaner operation 

that is closer to a stoichimetric air-to-fuel ratio without increasing the risk of abnormal 

combustion. This can be enhanced through careful selection of intake port geometry and 

combustion chamber shape to induce turbulence into the air/fuel cylinder charge. The leaner airto-fuel ratios (e.g., operating just rich of stoichiometry) resulting from advanced fuel systems 

and intake charge turbulence can significantly reduce HC and CO emissions and fuel 

consumption, and can provide more oxygen in the exhaust for improved catalytic control of HC 

and CO. Leaner air-to-fuel ratios, however, can increase NOx emissions due to higher 

combustion temperatures, particularly for engines that are not equipped with exhaust catalysts. 

More advanced fuel systems would allow tailoring of the air to fuel ratio to allow good transient 

response and to add enrichment at higher load conditions for engine and catalyst protection and 

to reduce engine-out NOx emissions. High-load enrichment is particularly important for aircooled engines, since high-load operation at leaner air-to-fuel ratios could also increase 

hydrocarbon emissions and PM emissions if the higher cylinder temperatures encountered result 

in a significant increase in cylinder-bore distortion and lubricating oil consumption. 

Figure 4.1-2: Effects of Air-to-Fuel Ratio on Torque Output, Fuel Consumption and 

Emissions for Naturally Aspirated Spark Ignition Engines. 

4.1.2.2 Spark-timing 

For each engine speed and air-fuel mixture, there is an optimum spark-timing that results 

in peak torque (“Maximum Brake Torque” or “MBT” timing). If the spark is advanced from 

MBT, more combustion occurs during the compression stroke. If the spark is retarded from 

MBT, peak cylinder pressure is decreased because too much combustion occurs later in the 

expansion stroke generating less useable torque. Timing retard may be used as a strategy for 

reducing NOx emissions, because it suppresses peak cylinder temperatures that lead to high NOx 

levels. Timing retard also results in higher exhaust gas temperatures, because less mechanical 

work is extracted from the available energy. This may have the benefit of warming catalyst 

material to more quickly reach the temperatures needed to operate effectively during light-load 

operation.2

 Some automotive engine designs rely on timing retard at start-up to reduce cold-start 

4-5 
Final Regulatory Impact Analysis 

emissions. 

Advancing the spark-timing at higher speeds gives the fuel more time to burn. Retarding 

the spark timing at lower speeds and loads avoids misfire. With a mechanically controlled 

engine, a fly-weight or manifold vacuum system adjusts the timing. Mechanical controls, 

however, limit the manufacturer to a single timing curve when calibrating the engine. This 

means that the timing is not completely optimized for most modes of operation. 

4.1.3 Marinization 

Gasoline sterndrive and inboard (SD/I) engines are generally derived from land-based 

counterparts. Engine marinizers buy automotive engine blocks and modify them for use on 

boats. Because of the good power/weight ratio of gasoline engines, most SD/I engines are not 

modified to produce more power than the base engines were originally designed to produce. In 

some airboat applications, aircraft engines are used. 

4.1.3.1 Typical SD/I marinization process 

Marine SI engines are typically built from base engines designed for use in cars and 

trucks. Currently, the vast majority of base engines are General Motor (GM) engines that range 

in size from a 3.0 L in-line four cylinder engine to an 8.1 L V8 engine and range in power from 

about 100 to 300 kW. These engines are sold without front accessory drives or intake and 

exhaust manifolds. Also, no carbureted versions of these engines are offered; they are either 

sold with electronic fuel injection, or no fuel system at all. Relatively small numbers of custom 

blocks and Mazda rotary engines are also used. 

Marinizers convert the base engines into marine engines in the following ways: 

- Choose and optimize the fuel management system. 

- Configure a marine cooling system. 

- Add intake and exhaust manifolds, and accessory drives and units. 

Fuel and air management: Historically, Marine SI engines have been carbureted. Today 

this technology seems to be going away but is still offered as cheaper alternative to electronic 

fuel injection. Less than half of new engines are sold with carburetors. GM does not offer 

carburetors or their associated intake manifolds because they are not used in the higher volume, 

automotive applications. Therefore, marinizers who produce carbureted engines must purchase 

the fuel systems and intake manifolds elsewhere. 

The 3.0 L and 4.3 L base engines are offered with throttle body fuel injection systems as 

an option. All of the larger engines are offered with multi-port fuel injection as an option. 

Although GM offers a base marine calibration for its electronic control module, it also offers 

software allowing marinizers to perform their own engine calibrations. For most engines sold, 

the marinizers will alter the calibrations to optimize engine operation. Except for some small 

market niches, the marinizers do not calibrate the engines for more power. 

4-6 
Feasibility of Exhaust Emission Control 

Cooling system: Marine SI engines are generally packaged in small compartments 

without much air flow for cooling. In addition, Coast Guard safety regulations require that 

surface temperatures be kept cool on the engine and exhaust manifold. Typically, marine 

exhaust systems are designed with surface temperatures below 93°C (200°F). To do this, 

manufacturers use ambient (raw) water to cool the engine and exhaust. Most sterndrive and 

inboard engines use raw water to cool the engine. This water is then used, in a water jacket, to 

cool the exhaust manifold. Finally, the water is dumped into the exhaust stream. 

Most Marine SI engines are cooled with raw water. This means that ambient water is 

pumped through the engine, to the exhaust manifold, and mixed with the exhaust. The 

exhaust/water mixture is then dumped under water. Mixing the water with exhaust has three 

advantages: 

- cools the exhaust and protects rubber couplings in sterndrives 

- acts as a muffler to reduce noise 

- helps tune the exhaust back pressure 

An alternative to raw water cooling is fresh water cooling. In a fresh water system, raw 

water is used to cool the recirculated engine coolant (“fresh water”). The raw water is generally 

still used to cool the exhaust manifold and exits the engine with the exhaust. However, some 

systems use the engine coolant to cool the exhaust manifold. 

Some gasoline engines, mostly inboards, have fresh water cooling systems which provide 

two advantages. 1) Engine corrosion problems are reduced, especially when the boat is used in 

saltwater. Fresh water systems keep saltwater, which can be corrosive, out of the engine. 

Because salt emulsifies at about 68°C, thermostats in fresh water systems are set around 60-

62°C. 2) Marinizers can achieve much better control of the engine temperature. By reducing 

variables in engine operation, combustion can be better optimized.3 

There are trade-offs with using a fresh water system. The fresh water system costs more 

because of the added pump and heat exchanger. Also, this system is not as efficient for cooling 

the engine as pumping raw water directly to the engine 

Other additions: As mentioned above, marinizers add intake manifolds to carbureted 

engines. As part of the cooling system, marinizers must add water jacketed exhaust manifolds, 

pumps, and heat exchangers. SD/I engines may also have larger oil pans to help keep oil 

temperatures down. Because of the unique marine engine designs, marinizers also add their own 

front accessory drive assembly. Finally, sterndrive engines also must be coupled with the lower 

drive unit. 

4.1.3.2 High performance SD/I marinization process 

There is a niche in the SD/I market where customers are willing to sacrifice engine 

durability for a high power to weight ratio. Marinizers who address this niche do so by 

increasing the fueling of the engine, optimizing the spark-timing for power, increasing the peak 

4-7 
Final Regulatory Impact Analysis 

engine speed (rpm), and modifying the exhaust manifold for better tuning. In some cases, the 

marinizers may actually increase the displacement of the engine by boring out the cylinders. 

Other components such as camshafts and pistons may also be modified. Superchargers may also 

be added. As an example, GM’s largest base engine for this market is rated at 309 kW. One 

high performance SD/I engine with a bored cylinder, a high performance fuel injection 

calibration, and a supercharger achieves more than 800 kW. 

4.1.4 Gaseous Fuels 

Engines operating on LPG or natural gas carry compressed fuel that is gaseous at 

atmospheric pressure. The technical challenges for gasoline related to an extended time to 

vaporize the fuel do not apply to gaseous-fuel engines. Typically, a mixer introduces the fuel 

into the intake system. Manufacturers are pursuing new designs to inject the fuel directly into 

the intake manifold. This improves control of the air-fuel ratio and the combustion event, similar 

to the improvements in gasoline injection technology. 

4.2 General Description of Exhaust Emission Control Technologies 

HC and CO emissions from spark-ignition engines are primarily the result of poor incylinder combustion. This is intensified in carbureted two-stroke engines with the very high HC 

emissions due to short-circuiting losses. Higher levels of NOx emissions are the result of leaner 

air-fuel ratios and the resulting higher combustion temperatures. Combustion chamber 

modifications can help reduce HC emission levels, while using improved air-fuel ratio and spark 

timing calibrations, as discussed in Sections 4.1.2.1 and 4.1.2.2, can further reduce HC emissions 

and lower CO emissions. The conversion from carburetor to electronic fuel injection will also 

help reduce HC and CO emissions. Exhaust gas recirculation could be used to reduce NOx 

emissions. The addition of secondary air into the exhaust can significantly reduce HC and CO 

emissions. Finally, the use catalytic converters can further reduce all three emissions. 

4.2.1 Combustion chamber design 

Unburned fuel can be trapped momentarily in crevice volumes (especially the space 

between the piston and cylinder wall) before being released into the exhaust. Reducing crevice 

volumes decreases this amount of unburned fuel, which reduces HC emissions. One way to 

reduce crevice volumes is to design pistons with piston rings closer to the top of the piston. HC 

may be reduced by 3 to 10 percent by reducing crevice volumes, with negligible effects on NOx 

emissions.4 

HC emissions also come from lubricating oil that leaks into the combustion chamber. 

The heavier hydrocarbons in the oil generally do not burn completely. Oil in the combustion 

chamber can also trap gaseous HC from the fuel and prevent it from burning. For engines using 

catalytic control, some components in lubricating oil can poison the catalyst and reduce its 

effectiveness, which would further increase emissions over time. To reduce oil consumption, 

manufacturers can tighten tolerances and improve surface finishes for cylinders and pistons, 

improve piston ring design and material, and improve exhaust valve stem seals to prevent 

4-8 
Feasibility of Exhaust Emission Control 

excessive leakage of lubricating oil into the combustion chamber. 

4.2.2 Fuel injection 

Fuel injection has proven to be an effective and durable strategy for controlling emissions 

and reducing fuel consumption from highway gasoline engines. Comparable upgrades are also 

available for gaseous fuels. This section describes a variety of technologies available to improve 

fuel metering. 

Throttle-body gasoline injection: A throttle-body system uses the same intake manifold 

as a carbureted engine. However, the throttle body replaces the carburetor. By injecting the 

fuel into the intake air stream, the fuel is better atomized than if it were drawn through with a 

venturi. This results in better mixing and more efficient combustion. In addition, the fuel can be 

more precisely metered to achieve benefits for fuel economy, performance, and emission control. 

Throttle-body designs have the drawback of potentially large cylinder-to-cylinder 

variations with multi-cylinder engines. Like a carburetor, TBI injects the fuel into the intake air 

at a single location upstream of all the cylinders. Because the air-fuel mixture travels different 

routes to each cylinder, and because the fuel “wets” the intake manifold, the amount of fuel that 

reaches each cylinder will vary. Manufacturers account for this variation in their design and may 

make compromises such as injecting extra fuel to ensure that the cylinder with the leanest 

mixture will not misfire. These compromises affect emissions and fuel consumption. 

Port gasoline injection: As the name suggests, port (single cylinder) or multi-port (multicylinder-port) fuel injection means that a fuel injector is placed in close proximity to each of the 

intake ports. The intake manifold, if used, flows only air. Sequentially-timed systems inject a 

quantity of fuel each time the intake valve opens for each cylinder, but multi-port injection 

systems can also be “batch fired” (all injectors pulsed simultaneously on a multicylinder engine) 

or continous (e.g., the Bosch CIS automotive systems of the 1970's and 80's). Port injection 

allows manufacturers to more precisely control the amount of fuel injected for each combustion 

event. This control increases the manufacturer’s ability to optimize the air-fuel ratio for 

emissions, performance, and fuel consumption. Because of these benefits, multi-port injection is 

has been widely used in automotive applications for decades. 

Sequential injection has further improved these systems by more carefully timing the 

injection event with the intake valve opening. This improves fuel atomization and air-fuel 

mixing, which further improves performance and control of emissions. 

A newer development to improve injector performance is air-assisted fuel injection. By 

injecting high pressure air along with the fuel spray, greater atomization of the fuel droplets can 

occur. Air-assisted fuel injection is especially helpful in improving engine performance and 

reducing emissions at low engine speeds. In addition, industry studies have shown that the short 

burst of additional fuel needed for responsive, smooth transient maneuvers can be reduced 

significantly with air-assisted fuel injection due to a decrease in wall wetting in the intake 

manifold. On a highway 3.8-liter engine with sequential fuel injection, the air assist was shown 

4-9 
Final Regulatory Impact Analysis 

to reduce HC emissions by 27 percent during cold-start operating conditions. At wide-openthrottle with an air-fuel ratio of 17, the HC reduction was 43 percent when compared with a 

standard injector.5 

4.2.3 Exhaust gas recirculation 

Exhaust gas recirculation (EGR) has been in use in cars and trucks for many years. The 

recirculated gas acts as a diluent in the air-fuel mixture, slowing reaction rates and absorbing 

heat to reduce combustion temperatures. These lower temperatures can reduce the engine-out 

NOx formation rate by as much as 50 percent.6 HC is increased slightly due to lower 

temperatures for HC burn-up during the late expansion and exhaust strokes. 

Depending on the burn rate of the engine and the amount of recirculated gases, EGR can 

improve fuel consumption. Although EGR slows the burn rate, it can offset this effect with 

some benefits for engine efficiency. EGR reduces pumping work of SI engines because the 

addition of nonreactive recirculated gases forces larger throttle openings for the same power 

output. Because the burned gas temperature is decreased, there is also less heat loss to the 

exhaust and cylinder walls. In effect, EGR allows more of the chemical energy in the fuel to be 

converted to useable work.7 

Electronic EGR control: Many EGR systems in today’s automotive applications utilize a 

control valve that requires vacuum from the intake manifold to regulate EGR flow. Under partthrottle operation where EGR is needed, engine vacuum is sufficient to open the valve. 

However, during throttle applications near or at wide-open throttle, engine vacuum is too low to 

open the EGR valve. While EGR operation only during part-throttle driving conditions has been 

sufficient to control NOx emissions for vehicles in the past, more stringent NOx standards and 

emphasis on controlling off-cycle emission levels may require more precise EGR control and 

additional EGR during heavy throttle operation to reduce NOx emissions. Automotive 

manufacturers now use electronic control of EGR. By using electronic solenoids to directly 

open and close the EGR valve or by modulating the vacuum signal to vacuum actuated valves, 

the flow of EGR can be precisely controlled. 

Stratified EGR: Another method of increasing the engine’s tolerance to EGR is to 

stratify the reicirculated gases in the cylinder. This stratification allows high amounts of dilution 

near the spark plug for NOx reduction while making undiluted air available to the crevices, oil 

films, and deposit areas so that HC emissions may be reduced. Stratification may be induced 

radially or laterally through control of air and mixture motion determined by the geometry of the 

intake ports. Research on a one cylinder engine has shown that stratified EGR will result in 

much lower fuel consumption at moderate speed and load (6 percent EGR at 2400 rpm, 2.5 bar 

BMEP) while maintaining low HC and NOx emissions when compared to homogeneous EGR.8 

For catalyst systems with high conversion efficiencies, the benefit of using EGR becomes 

proportionally smaller, although it can offer cost savings by reducing catalyst rhodium loadings. 

Including EGR as a design variable for optimizing the engine can add significantly to the 

development time needed to fully calibrate the electronic controls of engines or vehicles. 

4-10 
Feasibility of Exhaust Emission Control 

4.2.4 Multiple valves and variable valve timing 

Four-stroke engines generally have two valves for each cylinder, one for intake of the airfuel mixture and the other for exhaust of the combusted mixture. The duration and lift (distance 

the valve head is pushed away from its seat) of valve openings is constant regardless of engine 

speed. As engine speed increases, the aerodynamic resistance to pumping air in and out of the 

cylinder for intake and exhaust also increases. Automotive engines have started to use two 

intake and two exhaust valves to reduce pumping losses and improve their volumetric efficiency 

and useful power output. 

In addition to gains in volumetric efficiency, four-valve designs allow the spark plug to 

be positioned closer to the center of the combustion chamber, which decreases the distance the 

flame must travel inside the chamber. This decreases the likelihood of flame-quenching 

conditions in the areas of the combustion chamber farthest from the spark plug. In addition, the 

two streams of incoming gas can be used to achieve greater mixing of air and fuel, further 

increasing combustion efficiency and lowering engine-out emissions. 

Control of valve timing and lift take full advantage of the four-valve configuration for 

even greater improvement in combustion efficiency. Engines normally use fixed-valve timing 

and lift across all engine speeds. If the valve timing is optimized for low-speed torque, it may 

offer compromised performance under higher-speed operation. At light engine loads, for 

example, it is desirable to close the intake valve early to reduce pumping losses. Variable-valve 

timing can enhance both low-speed and high-speed performance with less compromise. 

Variable-valve timing can allow for increased swirl and intake charge velocity, especially during 

low-load operating conditions where this is most problematic. By providing a strong swirl 

formation in the combustion chamber, the air-fuel mixture can mix sufficiently, resulting in a 

faster, more complete combustion, even under lean air-fuel conditions, thereby reducing 

emissions. Automotive engines with valve timing have also replaced external EGR systems with 

“internal EGR” accomplished via variable valve overlap, generally with improved EGR rate 

control over external systems and improved engine-out NOx emissions. 

4.2.5 Secondary air 

Secondary injection of air into exhaust ports or pipes after cold start (e.g., the first 40-60 

seconds) when the engine is operating rich, coupled with spark retard, can promote combustion 

of unburned HC and CO in the exhaust manifold and increase the warm-up rate of the catalyst. 

By means of an electrical or mechanical pump, or by using a passive venturi or check-valve, 

secondary air is injected into the exhaust system, preferably in close proximity of the exhaust 

valve. Together with the oxygen of the secondary air and the hot exhaust components of HC and 

CO, net oxidizing conditions ahead of the catalyst can bring about an efficient increase in the 

exhaust temperature which helps the catalyst to heat up quicker. The exothermic reaction that 

occurs is dependent on several parameters (secondary air mass, location of secondary air 

injection, engine A/F ratio, engine air mass, ignition timing, manifold and headpipe construction, 

etc.), and ensuring reproducibility demands detailed individual application for each vehicle or 

engine design. 

4-11 
Final Regulatory Impact Analysis 

Secondary air injection was first used as an emission control technique in itself without a 

catalyst, and still is used for this purpose in many highway motorcycles and some off-highway 

motorcycles to meet federal and California emission standards. For motorcycles, air is usually 

provided or injected by a system of check valves which uses the normal pressure pulsations in 

the exhaust manifold to draw in air from outside, rather than by a pump.9 

Secondary air injection can also be used in continuous operation with rich-jetted 

carbureted engines to a achieve an exhaust chemistry just rich of stoichiometry to improve the 

efficiency of 3-way catalysts.10,11 

4.2.6 Catalytic Aftertreatment 

Over the last several years, there have been tremendous advances in exhaust 

aftertreatment systems. Catalyst manufacturers have increased the use of palladium (Pd), 

particularly for close-coupled positions in automotive catalyst applications.12 Improvements to 

catalyst thermal stability and washcoat technologies, the design of higher cell densities, and the 

use of two-layer washcoat applications are just some of the advances made in catalyst 

technology.13 Current Pd catalysts are capable of withstanding prolonged exposure to 

temperatures approaching 1100°C.14 The light-off temperature of these advanced catalysts is in 

the range of 250 to 270°C. 

There are two types of catalytic converters commonly used: oxidation and three-way. 

Oxidation catalysts use platinum and/or palladium to increase the rate of reaction between 

oxygen in the exhaust and unburned HC and CO. Ordinarily, this reaction would proceed very 

slowly at temperatures typical of engine exhaust. The effectiveness of the catalyst depends on its 

temperature, on the air-fuel ratio of the mixture, and on the mix of HC present. Highly reactive 

species such as formaldehyde and olefins are oxidized more effectively than less-reactive 

species. Short-chain paraffins such as methane, ethane, and propane are among the least reactive 

HC species, and are more difficult to oxidize. 

Three-way catalysts use a combination of platinum and/or palladium and rhodium. In 

addition to promoting oxidation of HC and CO, these metals also promote the reduction of NO to 

nitrogen and oxygen. In order for the NO reduction to occur efficiently, an overall rich or 

slightly-rich of stoichiometric air-fuel ratio is required. The NOx efficiency drops rapidly as the 

ai-fuel ratio becomes leaner than stoichiometric. If the air-fuel ratio can be maintained precisely 

at or just rich of stoichiometic, a three-way catalyst can simultaneously oxidize HC and CO and 

reduce NOx. The window of air-fuel ratios within which this is possible is very narrow and 

there is a trade-off between NOx and HC/CO control even within this window. The window can 

be broadened somewhat through the use of oxygen storage components, such as cerium oxide, 

within the catalyst washcoating. Cerium oxide also promotes CO and HC removal via steam 

reformation with water vapor in the exhaust, and the hydrogen liberated by these reactions 

promotes further NOx reduction. 

Manufacturers are developing catalysts with substrates that utilize thinner walls in order 

to design higher cell density, low thermal mass catalysts for close-coupled applications 

4-12 
Feasibility of Exhaust Emission Control 

(improves mass transfer at high engine loads and increase catalyst surface area). The cells are 

coated with washcoat which contain the noble metals which perform the catalysis on the exhaust 

pollutants. The greater the number of cells, the more surface area with washcoat that exists, 

meaning there is more of the catalyst available to convert emissions (or that the same catalyst 

surface area can be put into a smaller volume). Cell densities of 900 cells per square inch (cpsi) 

have already been commercialized, and research on 1200 cpsi catalysts has been progressing. 

Typical cell densities for conventional automotive catalysts are 400 to 600 cpsi. 

There are several issues involved in designing catalytic control systems for the engines 

covered by this rule. The primary issues are the cost of the system, packaging constraints, and 

the durability of the catalyst. This section addresses these issues. 

4.2.6.1 System cost 

Sales volumes of recreational vessels are small compared to automotive sales and while 

sales of Small SI engines <19kW are similar, the price of equipment is much less than 

automotive. Manufacturers therefore have a limited ability to recoup large R&D expenditures 

for these applications. For these reasons, we believe it is not appropriate to consider highly 

refined catalyst systems that are tailored specifically to nonroad applications. Catalyst 

manufacturers have assured us that automotive-type catalysts can easily be built to any size 

needed for Small SI and marine applications. We are considering catalyst packaging designs 

that do not require the manufactures to incur the costs of reworking the entire exhaust system 

and, for Marine SI engines, the lower power unit. The cost of these systems will decrease 

substantially when catalysts become commonplace. Chapter 6 describes the estimated costs for 

nonroad catalyst systems for Small SI and Marine SI engines. 

4.2.6.2 Differences in emission control system application and design by engine 

category 

One challenge in the use of catalytic control for Small SI and Marine SI engines lies in 

acceptable design and packaging of the exhaust catalysts onto a wide variety of different types of 

equipment. This section discusses specific issues related to these applications. 

4.2.6.2.1 Small SI Class I engines 

Class I engines typically are equipped with integral exhaust and fuel systems and are 

air-cooled. Significant applications include walk-behind lawn mowers (largest segment), 

pressure washers, generator sets and pumps. There are both overhead valve (OHV) and 

side-valve (SV) engines used in Class I, but side-valve engines are the predominant type in Class 

I, particularly in lawn mower applications. They currently represent about 60 percent of Class I 

sales. Exhaust catalyst design for Class I engines must take into account several important 

factors that differ from automotive applications: 

1.	 Air-cooled engines run rich of stoichiometry to prevent overheating when under load. 

Because of this, CO and HC emissions can be high. Catalyst induced oxidation of a high 

4-13 
Final Regulatory Impact Analysis 

percentage of available reactants in the exhaust in the presence of excess oxygen (i.e., 

lean of stoichiometric conditions) can result in highly exothermic exhaust reactions and 

increase heat rejection from the exhaust. For example, approximately 80 to 90 percent of 

the energy available from catalyst-promoted exhaust reactions is via oxidation of CO. 

2.	 Air-cooled engines have significant HC and NOx emissions that are typically much 

higher on a brake-specific basis than water-cooled automotive engine types. Net heat 

available from HC oxidation and NOx reduction at rich of stoichiometric conditions is 

considerably less than that of oxidation of CO at near stoichiometric or lean of 

stoichiometric conditions due to the much lower concentrations of NO and HC in the 

exhaust relative to CO. 

3.	 Most Class I engines do not have 12-volt DC electrical systems to power auxiliaries and 

instead are pull start. Electronic controls relying on 12-volt DC power would be difficult 

to integrate onto Class I engines without a significant cost increase. 

4.	 Most Class I engines use inexpensive stamped mufflers with internal baffles. Mufflers 

are typically integrated onto the engine and may or may not be placed in the path of 

cooling air from the cooling fan. 

5.	 The regulatory emission test cycles (A-cycle, B-cycle), manufacturer's durability cycles 

and some limited in-use operation data indicate that emissions control should focus 

primarily on light and part load operation for the highest volume applications 

(lawnmowers). 

These factors would lead to exhaust catalyst designs for small engines that should differ 

somewhat from those of light duty gasoline vehicle exhaust catalyst designs. Design elements 

specific to Class I Phase 3 exhaust catalysts would include: 

1.	 Catalyst substrate volume would be sized relatively small so as to be space-velocity 

limited. Catalyst volume for Class I Phase 3 engines would be approximately 18 to 50 

percent of the engine cylinder displacement, depending on cell count, engine-out 

emission levels, and oil consumption. Catalyst substrate sizes would be compact, with 

typical catalyst substrate volumes of approximately 2 to 5 cubic inches. This would 

effectively limit mass transport to catalyst sites at moderate-to-high load conditions and 

reduce exothermic reactions occurring when exhaust temperature is highest. This is 

nearly the opposite of the case of typical automotive catalyst designs. Automotive 

catalyst volume is typically 50 to 100 percent of cylinder displacement, with the chief 

constraints on catalyst volume being packaging and cold-start light-off performance. 

2.	 Catalyst precious metal loading (Pt-platinum, Pd-palladium, Rh-rhodium) would be kept 

relatively low, and formulations would favor NOx and HC selectivity over CO 

selectivity. We estimate that typical loading ratios for Phase 3 would be approximately 

in the range of 40 to 50 g/ft3 (approximately 50 percent of typical automotive loadings at 

light-duty vehicle Tier 2 emission levels) and can be Pt:Rh, Pd:Rh or tri-metallic. 

Tri-metallic platinum group metal (PGM) loadings that replace a significant fraction of Pt 

with Pd would be less selective for CO oxidation and would also reduce the cost of the 

catalyst. Loading ratios would be similar or higher in Rh than what is typically used for 

automotive applications (20-25 percent of the total PGM mass in Small SI) to improve 

NOx selectivity, improve rich of stoichiometry HC reactions and reduce CO selectivity. 

4-14 
Feasibility of Exhaust Emission Control 

3.	 Catalysts would be integrated into the muffler design. Incorporating the catalyst into the 

muffler would reduce surface temperatures, and would provide more surface area for heat 

rejection. This is nearly the opposite of design practice used for automotive systems, 

which generally try to limit heat rejection to improve cold-start light-off performance. 

The muffler design for Class I Phase 3 engines would have somewhat higher surface area 

and somewhat larger volume than many current Class I muffler designs in order to 

promote exhaust heat rejection and to package the catalyst, but would be similar to some 

higher-end "quiet" Class I muffler designs. Appropriately positioned stamped 

heat-shielding and touch guards would be integrated into Class I Phase 3 catalyst-muffler 

designs in a manner similar to many Class I Phase 2 mufflers. A degree of heat rejection 

would be available via forced convection from the cooling fan, downstream of cooling 

for the cylinder and cylinder head. This is the case with many current muffler designs. 

Heat rejection to catalyst muffler surfaces to minimize "hot spots" can also be enhanced 

internally by turning the flow through multiple chambers and baffles that serve as sound 

attenuation within the muffler, similar to the designs used with catalyst-equipped lawn 

mowers sold in Sweden and Germany. 

4.	 Many Class I Phase 3 catalysts would include passive secondary air injection to enhance 

catalyst efficiency and allow the use of smaller catalyst volumes. Incorporation of 

passive secondary air allows halving of catalyst substrate volume for the same catalyst 

efficiency over the regulatory cycle. A system for Class I Phase 3 engines would be sized 

small enough to provide minimal change in exhaust stoichiometry at high load conditions 

so as to limit heat rejection, but would be provide approximately 0.5 to 1.0 points of 

air-to-fuel ratio change at conditions of 50 percent of peak torque and below in order to 

lower HC emissions effectively in engines operating at air-to-fuel ratios similar to those 

of current Class I Phase 2 engines. Passive secondary air systems are preferred. 

Mechanical or electrical air pumps are not necessary. Passive systems include stamped 

or drawn venturis or ejectors integrated into the muffler, some of which may incorporate 

an air check-valve, depending on the application. Pulse-air injection is also a form of 

passive secondary air injection. Pulse air draws air into the exhaust port through a 

check-valve immediately following the closure of the exhaust valve. Active secondary 

air (air pump) systems were not considered in this analysis since they may be cost 

prohibitive for use in Class I applications due to the need for a mechanical accessory 

drive or 12-volt DC power. 

5.	 Catalyst durability in side valve engines can be enhanced through two catalyst design 

ideas. First, the use of a pipe catalyst upstream of the main catalyst brick can “catch” the 

oil in the exhaust thereby limiting the amount seen in the catalyst and thereby catalyst 

poisoning. Second, the catalyst brick can be lengthened to allow poisoning to some 

degree yet allow for catalyst conversion for the regulatory life of the engine. 

6.	 Class I engines are typically turned off via a simple circuit that grounds the input side of 

the ignition coil. Temperature fail-safe capability could, if appropriate, be incorporated 

into the engine by installing a bimetal thermal switch in parallel with the ignition 

grounding circuit used for turning the engine off. The switch can be of the inexpensive 

bimetal disc type in wide-spread use in numerous consumer products (furnaces, 

water-heaters, ovens, hair dryers, etc.). To reduce cost, the bimetal switch could be a 

non-contact switch mounted to the engine immediately behind the muffler, similar to the 

4-15 
Final Regulatory Impact Analysis 

installation of bimetal sensors currently used to actuate automatic chokes on current 

Phase 2 Class I lawn mower engines. 

4.2.6.2.2 Small SI Class II engines 

Almost all Class II engines are air-cooled. Unlike Class I engines, Class II engines are 

not typically equipped with integral exhaust systems and fuel tanks. Significant applications 

include lawn tractors (largest segment), commercial turf equipment, generator sets and pumps. 

Overhead valve engines have largely replaced side-valve engines in Class II, with the few 

remaining side-valve engines certifying to the Phase II standards using emissions credits or 

being used in snow thrower type applications where the HC+NOx standards do not apply. Class 

II engines are typically built more robustly than Class I engines. They often use cast-iron 

cylinder liners, may use either splash lubrication or full-pressure lubrication, employ high 

volume cooling fans and in some cases, use significant shrouding to direct cooling air. Exhaust 

catalyst design practice for Class II engines will differ depending on the level of emission 

control. Class II engine designs are more suitable for higher-efficiency emission control systems 

than most Class I engine designs. The design factors are somewhat similar to Class I: 

1.	 Class II engines are mostly air-cooled, and thus must run rich of stoichiometry at high 

loads. The ability to operate at air-to-fuel ratios rich of stoichiometry at high load may 

be more critical for some Class II engines than for Class I engines due to the longer 

useful life requirements in Class II. The larger displacement Class II engines have better 

efficiency combustion and some engines incorporate more advanced fuel metering and 

spark control than is typical in Class I, in order to meet the more stringent Class II Phase 

2 emission standards (12.1 g/kW-hr HC+NOx in Class II versus 16.1 g/kW-hr in Class I). 

The heat energy available from CO oxidation is typically somewhat less than the case in 

Class I because of slightly lower average emission rates. 

2.	 Class II engines have HC and NOx emissions that are generally in more equal portions, 

or have the potential to be, in the total regulated HC+NOx emissions and lower CO 

emissions than is the case for Class I engines. 

3.	 Most Class II engines are equipped with 12-volt DC electrical systems for starting. 

Electronic controls relying on 12-volt DC power could be integrated into Class II engine 

designs. Low-cost electronic engine management systems are extensively used in motor 

scooter applications in Europe and Asia. Both Kohler and Honda have introduced Class 

II engines in North America that use electronic engine management systems. 

4.	 Class II engines use inexpensive stamped mufflers with internal baffles similar to Class I, 

but the mufflers are often not integrated onto the engine design and may be remote 

mounted in a manner more typical of automotive mufflers. Class II mufflers are often not 

placed in the direct path of cooling air from the cooling fan. 

5.	 As with Class I, the regulatory cycles (A-cycle, B-cycle), manufacturer's durability cycles 

and some limited in-use operation data indicate that emissions control should focus 

primarily on light and part load operation for the high volume sales of garden tractor 

equipment. 

Taking these factors into account would point towards exhaust catalyst designs that differ 

4-16 
Feasibility of Exhaust Emission Control 

from those of light duty gasoline exhaust catalysts and differ in some cases from Class I systems. 

Elements specific to Class II Phase 3 emission control system design using carburetor fuel 

systems would include: 

1.	 Catalyst substrate volume would be sized relatively small so as to be space-velocity 

limited. Catalyst volume for Class II Phase 3 engines would be approximately 33-50 

percent of the engine cylinder displacement, depending on cell count, engine-out 

emission levels, oil consumption and the useful life hours to which the engine's emissions 

are certified. Catalyst substrate sizes would be very compact within typical mufflers used 

in Class II, with typical catalyst substrate volumes of approximately 8 to 10 cubic inches 

(based on sales weighting within useful life categories). This would effectively limit 

mass transport to catalyst sites at moderate-to-high load conditions and reduce 

exothermic reactions occurring when exhaust temperature is highest. 

2.	 Catalyst precious metal loading would be kept relatively low, and formulations would 

favor NOx and HC selectivity over CO selectivity to minimize heat concerns. We 

estimate that typical loading ratios for Phase 3 would be approximately in the range of 30 

to 50 g/ft3 (approximately 50 percent of typical automotive loadings) and could be Pt:Rh, 

Pd:Rh or tri-metallic. Tri-metallic PGM loadings that replace a significant fraction of Pt 

with Pd would be less selective for CO oxidation and would also reduce the cost of the 

catalyst. Loading ratios would be similar or higher in Rh than what is typically used for 

automotive applications (20-25 percent of the total PGM mass in Small SI). 

3.	 Catalysts would be integrated into the muffler design. Incorporating the catalyst into the 

muffler would reduce surface temperatures relative to the use of a separate catalyst 

component. The catalyst for Class II Phase 3 engines would be integrated into mufflers 

that are similar in volume to today's Class II Phase 2 mufflers. Appropriately positioned 

stamped heat-shielding and touch guards would be integrated into Class II Phase 3 

catalyst-muffler designs in a manner similar to current product. Class II engines typically 

have a much higher volume of cooling air available downstream of the cylinder than 

Class I engines. Heat rejection from the cylinder and cylinder head increases the 

temperature of the cooling air, but it is still sufficiently below the temperature of exhaust 

system components to allow its use for forced cooling. Thus a degree of heat rejection 

would be available via forced convective cooling of exhaust components via the cooling 

fan. However, this would require some additional ducting to supply cooling air to exhaust 

system surfaces along with careful layout of engine and exhaust components within the 

design of the equipment that it is used to power. Integrated catalyst-mufflers can also use 

exhaust energy for ejector cooling (see chapter 6). Heat rejection to catalyst muffler 

surfaces to minimize "hot spots" can also be enhanced internally by turning the flow 

through multiple chambers and baffles that serve as sound attenuation within the muffler. 

4.	 Some applications may include secondary air injection to enhance catalyst efficiency. 

Incorporation of passive secondary air allows halving of catalyst substrate volume for the 

same catalyst efficiency over the regulatory cycle. In many cases, this may not be 

necessary due to the lower engine-out emissions of Class II engines. In cases where 

secondary air is used, it could either be a passive system similar to the previously 

described Class I systems, or an active system with an engine driven pump. Pump drive 

for active systems could be either 12-volt DC electric or via crankcase pulse, and pump 

4-17 
catalyst 

Final Regulatory Impact Analysis 

actuation could be actively controlled using an electric solenoid or solenoid valve. The 

use of active systems is an option but seems unlikely. The most likely control scenario 

for Class II would be a combination of engine out emission control, use of a small 

catalyst, and no use of secondary air. 

Higher catalyst efficiency, considerably lower exhaust emissions levels, and improved fuel 

consumption are possible with Class II engines, but heat rejection and safety considerations 

might necessitate the use of electronic engine management and open-loop fuel injections 

systems. In such a case, the design and integration of the emission control system would more 

closely resemble automotive applications with the use of electronic engine management and 

larger catalyst volumes with higher precious metal loadings. 

4.2.6.2.3 Marine SI 

Due to the design of marine exhaust systems, fitting a catalyst into the exhaust system 

raises unique application issues for many boat/engine designs. Often boat builders will strive to 

minimize the space taken up in the boat by the engine compartment. In addition, these exhaust 

systems are designed, for safety reasons, to avoid hot surface temperatures. For most Marine SI 

engines, the surface temperature is kept low by running raw water through a jacket around the 

exhaust system. This raw water is then mixed with the exhaust before being passed out of the 

engine. To avoid a major redesign of the exhaust system, the catalyst must be placed upstream 

of where the water and exhaust mix. In addition, the catalyst must be insulated and/or waterjacketed to keep the surface temperatures of the exhaust low. 

As discussed later in this chapter, Figure 4.2-1: Placement of Marine Catalyst 

testing has been performed on prototype 

systems where small catalysts have been placed 

in the exhaust manifolds of SD/I engines. 

Figure 4.2-1 illustrates one installation design. 

For outboard engines, this packaging 

arrangement would be less straightforward 

because of the very short exhaust path between 

the cylinder exhaust ports and where the 

cooling water and exhaust mix. However, it 

may be possible to engineer a packaging 

solution for outboards as well similar to that 

shown for SD/I in Figure 4.2-1. 

Several marine engine manufacturers 

are now producing engines with water jacketed 

catalysts in the exhaust. As discussed later in this chapter, one manufacturer has certified 

personal watercraft engines with catalysts packaged in the exhaust system. These are small 

oxidation catalysts used in conjunction with two-stroke engines. Two manufacturers are selling 

marine generators with catalysts. Also, one SD/I engine marinizer has recently added an engine 

with catalysts in the exhaust to its product line. 

4-18 

exhaust 

water 
Feasibility of Exhaust Emission Control 

Another issue is maintaining high enough temperatures with a water-jacketed catalyst for 

the catalyst to react properly. The light-off temperature of these advanced catalysts is in the 

range of 250 to 270°C which was low enough for the catalysts to work effectively in our 

laboratory tests. However, it could be necessary for manufacturers to retard the spark timing at 

idle and low load for some engines to maintain this minimum temperature in the catalyst. 

The matching of the catalyst to the engine may have to be compromised to fit it into the 

exhaust manifold. However, significant reductions are still achievable. One study on a 4.3 liter 

automotive engine looked at three different Pd-only catalyst displacements. The smallest of 

these catalysts had a displacement ratio of 0.12 to 1. The HC+NOx downstream of the catalyst 

was measured to be from 1.2 to 2.6 grams per mile, depending on the severity of the catalyst 

aging.15 This is equivalent to about 1.5 to 3.2 g/kW-hr based on highway operation.16 This work 

suggests that significant reductions are achievable with an “undersized” catalyst. As discussed 

later in this chapter, significant reductions in exhaust emissions have been demonstrated for 

catalysts packaged in SD/I exhaust systems. 

4.2.6.3 Catalyst Durability 

Two aspects of marine applications that could affect catalyst durability are thermal load 

and vibration. Because the catalyst would be coupled close to the exhaust ports, it would likely 

see temperatures as high as 750 to 850°C when the engine is operated at full power. The bed 

temperature of the catalyst would be higher due to the reactions in the catalyst. However, even 

at full power, the bed temperature of the catalyst most likely would not exceed the exhaust 

temperature by more than 50-100°C. In our laboratory testing, we minimized the temperature at 

full load by operating the engine with a rich air-fuel mixture. The temperatures seen were well 

within the operating range of new Pd-only catalysts which are capable of withstanding prolonged 

exposure to temperatures approaching 1100°C.17 

In on-highway applications, catalysts are designed to operate in gasoline vehicles for 

more than 100,000 miles. This translates to about 4,000-5,000 hours of use on the 

engine/catalyst. We estimate that, due to low annual hours of operation, the average useful life 

of Small SI and Marine SI engines is only a fraction percent of this value. This suggests that 

catalysts designed for automotive use should be durable over the useful life of a Small SI and 

Marine SI engines. Use of catalysts in automotive, motorcycle, and hand-held equipment 

applications suggests that catalysts can be packaged to withstand the vibration in the exhaust 

manifold. As discussed later in this chapter, catalysts have recently been demonstrated, through 

in-use testing, to be durable over the useful lives of SD/I marine vessels. 

4.2.6.4 Water Reversion 

Another aspect of marine applications that could affect catalyst durability is the effect of 

water contact with the catalyst. There is concern that, in some designs, water could creep back 

up the exhaust passages, due to pressure pulses in the exhaust, and damage the catalyst and 

oxygen sensor. This damage could be due to thermal shock from cold water coming into contact 

with a hot catalyst or due to salt deposition on the catalyst. One study was performed, using a 

4-19 
Final Regulatory Impact Analysis 

two-stroke outboard equipped with a catalyst, to investigate the effect of water exposure on a 

catalyst.18 The results of this study are summarized in Table 4.2-1. 

Table 4.2-1: Summary of Marine Catalyst Durability Study 

Issue Investigation Result 

high catalyst 

temperatures 

- compared base catalyst to catalysts aged for 10 

hrs at 900 and 1050°C 

- little change in conversion efficiency 

observed 

saltwater effects - soaked catalysts in two seawater solutions and 

compared to base catalyst 

- used intake air with a salt-water mist 

- large drop in conversion efficiency 

observed 

- no effect on catalyst 

fresh water effects - soaked catalyst in fresh water and compared to 

base catalyst 

- flushed out catalyst with fresh water that was 

soaked in saltwater 

- little change in conversion efficiency 

observed 

- washing catalyst removes salt and 

restores some performance 

thermal shock of hot 

catalyst with cold 

water 

- as part of the catalyst soaking tests, 900°C 

catalysts were soaked in both salt and fresh 

water 

- no damage to the catalysts was 

reported 

deterioration factor - operated engine with catalyst for 300 hours of 

E4 operation 

- 20% loss in conversion efficiency for a 

2-stroke engine 

The above study on catalysts in marine applications was performed supplemental to an 

earlier study.19 The earlier study also showed that immersing the catalysts in saltwater would 

hurt the conversion efficiency of the catalyst, but that operating in a marine environment would 

not. In addition, this earlier study showed that much of the efficiency loss due to salt on the 

catalyst could be reversed by flushing the catalyst with water. This paper also showed that with 

the catalyst activated, temperatures at full power were less than at mid power because the space 

velocity of the exhaust gases at rated speed was high enough to reduce the conversion efficiency 

of the catalyst. 

A study of water reversion was performed on a vessel powered by a sterndrive engine.20 

However, it was found that the water found in the exhaust system upstream of where the exhaust 

and water mix was due to condensation. This condensation was a result of cool surfaces in the 

exhaust pipe due to the water-jacketing of the exhaust. This study found that the condensation 

could be largely resolved by controlling the exhaust cooling water temperature with a thermostat. 

Since that time, data has been collected on a number of catalyst-equipped SD/I vessels operated 

either in salt or fresh-water. This data, which showed no significant catalyst deterioration, is 

discussed later in this chapter. These engines were designed to prevent water reversion by 

placing the catalyst near the engine and away from the water/exhaust mixing point. In addition, 

some of the prototype designs used either a water dam or mist barrier to help limit any potential 

water reversion. 

4-20 
Feasibility of Exhaust Emission Control 

4.2.7 Advanced Emission Controls 

On February 10, 2000, EPA published new "Tier 2" emissions standards for all passenger 

vehicles, including sport utility vehicles (SUVs), minivans, vans and pick-up trucks. The new 

standards will ensure that exhaust VOC emissions be reduced to less than 0.1 g/mi on average 

over the fleet, and that evaporative emissions be reduced by at least 50 percent. Onboard 

refueling vapor recovery requirements were also extended to medium-duty passenger vehicles. 

By 2020, these standards will reduce VOC emissions from light-duty vehicles by more than 25 

percent of the projected baseline inventory. To achieve these reductions, manufacturers will 

need to incorporate advanced emission controls, including: larger and improved close-coupled 

catalysts, optimized spark timing and fuel control, improved exhaust systems. 

To reduce emissions, gasoline-fueled vehicle manufacturers have designed their engines 

to achieve virtually complete combustion and have installed catalytic converters in the exhaust 

system. In order for these controls to work well for gasoline-fueled vehicles, it is necessary to 

maintain the mixture of air and fuel at a nearly stoichiometric ratio (that is, just enough air to 

completely burn the fuel). Poor air-fuel mixture can result in significantly higher emissions of 

incompletely combusted fuel. Current generation highway vehicles are able to maintain 

stoichiometry by using closed-loop electronic feedback control of the fuel systems. As part of 

these systems, technologies have been developed to closely meter the amount of fuel entering the 

combustion chamber to promote complete combustion. Sequential multi-point fuel injection 

delivers a more precise amount of fuel to each cylinder independently and at the appropriate time 

increasing engine efficiency and fuel economy. Electronic throttle control offers a faster 

response to engine operational changes than mechanical throttle control can achieve, but it is 

currently considered expensive and only used on some higher-price vehicles. The greatest gains 

in fuel control can be made through engine calibrations -- the algorithms contained in the 

powertrain control module (PCM) software that control the operation of various engine and 

emission control components/systems. As microprocessor speed becomes faster, it is possible to 

perform quicker calculations and to increase response times for controlling engine parameters 

such as fuel rate and spark timing. Other advances in engine design have also been used to 

reduce engine-out emissions, including: the reduction of crevice volumes in the combustion 

chamber to prevent trapping of unburned fuel; "fast burn" combustion chamber designs that 

promote swirl and flame propagation; and multiple valves with variable-valve timing to reduce 

pumping losses and improve efficiency. These technologies are discussed in more detail in the 

RIA for the Tier 2 FRM.21 

As noted above, manufacturers are also using aftertreatment control devices to control 

emissions. New three-way catalysts for highway vehicles are so effective that once a TWC 

reaches its operating temperature, emissions are virtually undetectable.22 Manufacturers are now 

working to improve the durability of the TWC and to reduce light-off time (that is, the amount of 

time necessary after starting the engine before the catalyst reaches its operating temperature and 

is effectively controlling VOCs and other pollutants). EPA expects that manufacturers will be 

able to design their catalyst systems so that they light off within less than thirty seconds of 

engine starting. Other potential exhaust aftertreatment systems that could further reduce coldstart emissions are thermally insulated catalysts, electrically heated catalysts, and HC adsorbers 

4-21 
Final Regulatory Impact Analysis 

(or traps). Each of these technologies, which are discussed below, offers the potential for VOC 

reductions in the future. There are technological, implementation, and cost issues that still need 

to be addressed, and at this time, it appears that these technologies would not be a cost-effective 

means of reducing nonroad emissions on a nationwide basis. 

Thermally insulated catalysts maintain sufficiently high catalyst temperatures by 

surrounding the catalyst with an insulating vacuum. Prototypes of this technology have 

demonstrated the ability to store heat for more than 12 hours.23 Since ordinary catalysts typically 

cool down below their light-off temperature in less than one hour, this technology could reduce 

in-use emissions for vehicles that have multiple cold-starts in a single day. However, this 

technology would have less impact on emissions from vehicles that have only one or two coldstarts per day. 

Electrically-heated catalysts reduce cold-start emissions by applying an electric current to 

the catalyst before the engine is started to get the catalyst up to its operating temperature more 

quickly.24 These systems require a modified catalyst, as well as an upgraded battery and 

charging system. These can greatly reduce cold-start emissions, but could require the driver to 

wait until the catalyst is heated before the engine would start to achieve optimum performance. 

Hydrocarbon adsorbers are designed to trap VOCs while the catalyst is cold and unable 

to sufficiently convert them. They accomplish this by utilizing an adsorbing material which 

holds onto the VOC molecules. Once the catalyst is warmed up, the trapped VOCs are 

automatically released from the adsorption material and are converted by the fully functioning 

downstream three-way catalyst. There are three principal methods for incorporating an adsorber 

into the exhaust system. The first is to coat the adsorber directly on the catalyst substrate. The 

advantage is that there are no changes to the exhaust system required, but the desorption process 

cannot be easily controlled and usually occurs before the catalyst has reached light-off 

temperature. The second method locates the adsorber in another exhaust pipe parallel with the 

main exhaust pipe, but in front of the catalyst and includes a series of valves that route the 

exhaust through the adsorber in the first few seconds after cold start, switching exhaust flow 

through the catalyst thereafter. Under this system, mechanisms to purge the adsorber are also 

required. The third method places the trap at the end of the exhaust system, in another exhaust 

pipe parallel to the muffler, because of the low thermal tolerance of adsorber material. Again a 

purging mechanism is required to purge the adsorbed VOCs back into the catalyst, but adsorber 

overheating is avoided. One manufacturer who incorporates a zeolite hydrocarbon adsorber in 

its California SULEV vehicle found that an electrically heated catalyst was necessary after the 

adsorber because the zeolite acts as a heat sink and nearly negates the cold start advantage of the 

adsorber. This approach has been demonstrated to effectively reduce cold start emissions. 

4.3 Feasibility of Small SI Engine Standards 

We are establishing new, more stringent HC+NOx standards for Small SI engines 

(<19kW) used in nonhandheld, terrestrial applications (we are also setting a CO std for Small SI 

engines used in marine applications that is discussed in Section 4.4). The standards differ by 

engine size. Class I engines have a total cylinder displacement of < 225cc. Class II engines 

4-22 
Feasibility of Exhaust Emission Control 

have a total displacement of $225cc. We are also making changes to the emission certification 

protocols for durability testing and test fuel specifications for both classes. The new certification 

requirements will improve emissions performance of these engines over their regulatory lifetime 

and better align the test fuel with in-use fuel characteristics. 

Table 4.3-1 shows the existing Phase 2 exhaust emission standards for Class I and II 

small spark ignition engines as well as the new Phase 3 standards. The Phase 3 standards 

represent a nominal 35-40 percent reduction from current standards. 

Table 4.3-1: Comparison of Phase 2 and Phase 3 

Standards for Small Spark-Ignition Engines 

Engine Class Phase 2 Standards 

(HC+NOx g/kW-hr) 

Phase 3 Standards 

(HC+NOx g/kW-hr) 

Percent Reduction 

(%) 

Class I (<225 cc) 16.1 10.0 38 

Class II ($225cc) 12.1 8.0 34 

The following sections present the technical analyses and information that support our 

view that the Phase 3 exhaust emission requirements are technically feasible. We begin with a 

review of the current state of compliance with the Phase 2 standards relative to the Phase 3 

standards and conclude with a more in depth assessment of the technical feasibility of the 

requirements for Class I gasoline-fueled engines, Class II single-cylinder gasoline-fueled 

engines, Class II multi-cylinder gasoline-fueled engines, and both classes of gaseous-fueled (e.g., 

liquid propane gas) engines. 

4.3.1 Current Technology and 2008 Certification Test Data 

In the 2008 model year manufacturers certified engines to the Phase 2 standards using a 

variety of engine designs and emission control technology. Table 4.3-2 shows manufacturers’ 

projected engine sales by technology type. For Class I engines, side-valve designs represent the 

majority of sales, although there are also a significant number of overhead-valve sales. An 

extremely small number of engines used catalyst-based emission control technology. Class II is 

dominated by overhead-valve engine designs. A limited number of these engines used catalyst 

technology, electronic fuel injection, or were water cooled. 

4-23 
Final Regulatory Impact Analysis 

Table 4.3-2: 2005 Engine Sales by Technology Market Mix 

Engine Technology Class I Class II 

Side Valve 66% 2% 

Overhead Valve 34% 98% 

With Catalyst 0.003% 0.4% 

With Other (Electronic Fuel 

Injection and/or water cooled) 

0 1% 

Looking at the industry from an engine family rather than a sales perspective, shows that 

68 and 212 engine families were emission certified in Class I and II, respectively for 2008. The 

range of technology types is shown in Table 4.3-3. The majority of engine families in Class I are 

overhead-valve, carbureted engines, with only 14 families using side-valve, carbureted designs 

(the side-valve engines still account for the bulk of Class I sales). Five families utilized catalytic 

exhaust aftertreatment. 

Table 4.3-3: 2005 Small Spark-Ignition 

Engine Technology Types and Number of Engine Families 

Engine 

Class 

Side-Valve Overhead Valve 

SingleCylinder 

Carburetor 

SingleCylinder 

Carburetor 

w. Catalyst 

SingleCylinder 

Carburetor 

SingleCylinder 

Carburetor 

w. Catalyst 

MultiCylinder 

Carburetor 

MultiCylinder 

Carburetor 

w. Catalyst 

MultiCylinder 

Fuel 

Injection 

MultiCylinder 

Fuel 

Injection 

w. 

Catalyst 

I yes (14) no yes (48) yes (4) no no no no 

II yes (2) yes (0) yes (43) no yes (105) yes (6) yes (6) yes (8) 

In Class II, the majority of the engine families use multi-cylinder (predominately v-twins) 

designs incorporating overhead-valve technology. Most of these multi-cylinder families utilized 

carburetors, with a few using catalytic exhaust aftertreatment, fuel injection, or electronic engine 

controls. There are relatively fewer single-cylinder engine families using the older, less 

sophisticated side-valve technology. None of these engines were certified with catalytic 

aftertreatment. 

Figures 4.3-1 and 4.3-2 present the 2008 certification results at full life for Class I and II 

4-24 
Feasibility of Exhaust Emission Control 

engine families, respectively, by technology type.1 One striking feature of these figures, especially 

Figure 4.3-2, is that there are a number of engine families displaying emission levels well above 

the existing, i.e., Phase 2, standards. Generally, these families represent somewhat older 

technology, low production engines that have been certified using preexisting emission credits. 

Under the conditions of the final Phase 3 rules, these engine families will be unable to be certified 

using existing credits. As a consequence, we expect these families will be eliminated in favor of 

newer designs when the Phase 3 standards become effective. 

Looking at the remaining engine families, several families were certified at levels 

necessary to comply with the Phase 3 standards. Also, a number of families are very close to the 

requisite emission levels. This suggests that, even accounting for the relative increase in 

stringency associated with our certification protocols, a number of families will either not need to 

do anything or require only modest reductions in their emission performance to meet the new 

standards. 

1 The data presented in Figure 4.3-1 and Figure 4.3-2 are consistent with the 2008 certification data used for the cost 

analysis in Chapter 6. This data does not include certification data from the nearly 90 Chinese manufacturers that have started 

certifying nonhandheld engines with EPA in the last few years. (As noted in Chapter 6, EPA has chosen not include data from 

Chinese manufacturers because we have no information on actual sales of their engines in the United States. Based on 

discussions with nonhandheld engine manufacturers that have been certifying with EPA for over ten years now, it is our 

understanding that sales of nonhandheld engines from Chinese manufacturers are relatively small at this time.) The certification 

levels of the engines certified by Chinese manufacturers generally fall within the same range as the engines presented in Figure 

4.3-1 and Figure 4.3-2. 

4-25 
Final Regulatory Impact Analysis 

Figure 4.3-1:Class I HC+NOx Full Life Certification Results for 

2008 

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

20 

22 

24 

26 

80 100 120 140 160 180 200 220 

Displacement (cc) 

HC+NOx (g/kW-hr) 

SV Carb 

OHV Carb 

OHV Catalyst 

Phase 2 

Standard 

Phase 3 

Standard 

Figure 4.3-2: Class II HC+NOx Full Life Certification Results for 

2008 

0 

2 

4 

6 

8 

10 

12 

14 

16 

0 200 400 600 800 1000 1200 1400 

Displacement (cc) 

HC+NOx (g/kW-hr)

SV Carb 

OHV Carb 

OHV Fuel Inj 

OHV Catalyst 

Phase 2 

Standard 

Phase 3 

Standard 

4-26 
Feasibility of Exhaust Emission Control 

4.3.2 Technology Assessment and Demonstration 

As described above, a number of engine families already are certified to emission levels 

that likely would comply with the Phase 3 standards. However, many engine families clearly will 

have to do more to improve emission performance. Generally, we believe the new requirements 

will require many engine manufacturers to adopt exhaust aftertreatment technology using 

catalyst-based systems. Other likely changes include improved engine designs and fuel delivery 

systems. Finally, adding electronic controls or fuel injection systems may obviate the need for 

catalytic aftertreatment for some engine families, with the most likely candidates being 

multi-cylinder engine designs. 

Many of the technical design considerations for adapting advanced emission controls to 

Small SI engines were presented in Section 4.2. These included redirected air from the cooling 

fan, redirected exhaust flow through multiple chamber and baffles within the catalyst muffler, or 

other design considerations. (These are also the kinds of design elements that engine 

manufacturers will need to consider for safe and durable emission control systems.) In the 

remainder of this section we describe the specific results of our emission control assessment based 

on engine testing of exhaust catalyst systems, as well as a more specific discussion of other 

potential emission reduction technology for certain engine types such as electronic engine controls 

and fuel injection. The results of our safety assessment are described later in section 4.8 of this 

chapter. 

4.3.2.1 Overview of Technology Assessment 

Our feasibility assessment began by evaluating the emissions performance of current 

technology for Small SI engines and equipment. These initial efforts focused on developing a 

baseline for emissions and general engine performance so that we could assess the potential for 

new emission standards for engines and equipment in this category. This process involved 

laboratory and field evaluations of the current engines and equipment. We reviewed engineering 

information and data on existing engine designs and their emissions performance. We also 

reviewed patents of existing catalyst/muffler designs for Class I engines. We engaged engine 

manufacturers and suppliers of emission control-related engine components in discussions 

regarding recent and expected advances in emissions performance beyond that required to comply 

with the current Phase 2 standards. Finally, we purchased catalyst/muffler units that were already 

in mass production by an original equipment manufacturer for use on European walk-behind lawn 

mowers and conducted engineering and chemical analysis on the design and materials of those 

units. 

We used the information and experience gathered in the above effort along with the 

previous catalyst design experience of our engineering staff to design and build prototype 

catalyst-based emission control systems that were capable of effectively and safely achieving the 

Phase 3 requirement based on dynamometer and field testing. We also used the information and 

the results of our engine testing to assess the potential need for improvements to engine and fuel 

system designs, and the selective use of electronic engine controls and fuel injection on some 

engine types. A great deal of this effort was conducted in association with our more exhaustive 

4-27 
Final Regulatory Impact Analysis 

study regarding the efficacy and safety of implementing advanced exhaust emission controls on 

Small SI engines, as well as new evaporative requirements for these engines.25 In other testing, we 

evaluated advanced emission controls on a multi-cylinder Class II engine with electronic fuel 

injection.26 

In designing our engine testing program, we selected engines certified to the Phase 2 

emission standards that were expected to remain compliant with those standards for the duration of 

their useful life based on our low-hour emission testing and the manufacturer's declared 

deterioration factor from the certification records for that engine family. We also selected engine 

families that represented: 1) a cross section of Class I and Class II side-valve and overhead-valve 

technologies; and 2) higher sales volume families. Each engine was maintained based on the 

manufacturer's specifications.2 The results of our specific technical feasibility assessment are 

presented below. 

4.3.2.2 Class I Gasoline-Fueled Engines 

We tested six side-valve and six overhead-valve Class I engines that used gasoline fuel 

with prototype catalyst/muffler control systems. The primary design target for selecting the 

catalyst configuration, e.g., volume, substrate, platinum group metal (PGM), was to achieve 

emission levels below the limit of 10 g/kW-hr HC+NOx for this class at 125 hours of engine 

operation. That time period represents the useful life requirement for the most common 

application in this category, i.e., residential walk-behind lawn mowers. A maximum of about 7 

g/kW-hr HC+NOx was set as the low-hour performance target with a catalyst system to allow for 

engine and emission control degradation over the engine's useful life. This level assumes a 

certification cushion at low hours of 1 g/kW-hr HC+NOx and a multiplicative deterioration factor 

of 1.3. Secondary design targets were primarily safety related and included minimizing CO 

oxidation at moderate to high load conditions to maintain exhaust system surface temperatures 

comparable to those of the original Phase 2 compliant systems. The test engine, size, and salient 

catalyst features are shown in Table 4.3-4. 

Table 4.3-5 presents the results of our catalyst testing on Class I engines.27,28 Three of the 

engines were tested at high hours. The high-hour results for the remaining engines were projected 

from their low-hour emission performance. We projected high-hour emission results for these 

engines by applying the multiplicative deterioration factor from the manufacturer's Phase 2 

certification application to the low-hour emission test results. The certification deterioration 

factors ranged from 1.097 to 1.302 g/kW-hr HC+NOx. 3

 As shown, each of the engines achieved 

the requisite emission limit of 10 g/kW-hr HC+NOx at the end of their useful lives. 

2

 The specific test engines were generally used in residential lawn mower and lawn tractor applications. 

These applications were chosen for field testing as part of our safety study because they represented certain 

potentially unique and challenging safety concerns connected with operation and storage in environments with 

combustible debris. 

3

 These results were taken from the 2005 certification results. 

4-28 
Table 4.3-4: Class I Test Engine and Control Technology Description 

Engine ID 

Displacement

 (L) 

Valve 

Train 

Fuel 

Metering 

Passive 

(Venturi) 

Secondary 

Air? 

Catalyst Type Catalyst Volume Catalyst Cell Density 

236 0.20 Side Carburetor Yes Metal monolith 44 cc 200 cpsi 

246 0.20 Side Carburetor Yes Metal monolith 44 cc 200 cpsi 248 0.20 Side Carburetor Yes Metal monolith 44 cc 200 cpsi 249 0.20 Side Carburetor Wire-mesh 60 cc N/A 6820 0.19 Side Carburetor Yes Cordierite 

Ceramic Monolith 

40 cc 400 cpsi 

258 0.19 Side Carburetor Yes Cordierite 

Ceramic Monolith 

40 cc 400 cpsi 

241 0.19 Overhead Carburetor Yes Cordierite 

Ceramic Monolith 

40 cc 400 cpsi 

255 0.19 Overhead Carburetor Yes Coated tube precatalyst, Metal 

monolith mainbody catalyst 

20 mm dia. X 73 mm long exhaust tubing, 22 cc metal monolith 

Tube: 2 channels (annular shape), Main body: 200 cpsi 

2982 0.19 Overhead Carburetor Yes Metal monolith 34 cc 100 cpsi 

243 0.16 Overhead Carburetor Yes Cordierite 

Ceramic Monolith 

30 cc 400 cpsi 

244 0.16 Over-head Carburetor Yes Metal monolith 44 cc 200 cpsi 245 0.16 Overhead Carburetor Yes Metal monolith 44 cc 200 cpsi 
Final Regulatory Impact Analysis 

Table 4.3-5: Class I Emission Results with Advanced Catalytic Control Technology 

Engine 

Age 

(hours)1 

HC+NOx 

(g/kW-hr) 

236 10-20 4.9 ± 0.62 

Projected High 6.1 

246 10-20 5.6 

Projected High 7.0 

248 10-20 4.6 

Projected High 5.7 

249 10-20 6.3 

Projected High 7.8 

6820 Not Tested na 

>110 9.4 

258 10-20 6.7 

>110 8.2 

241 10-20 3.9 ± 0.2 

>110 6.6 ± 0.2 

255 10-20 5.0 

Projected High 6.5 

2982 10-20 4.9 ± 0.3 

>110 7.0 ± 0.4 

243 10-20 7 ± 1 

Projected High 7.7 

244 10-20 7.2 

Projected High 7.9 

245 10-20 5.6 

Projected High 6.1 

1

 Projected high hour results estimated by multiplying the low hour test results by the 

manufacturer’s certification deterioration rate. 2

 “±” values represent the 95% confidence intervals of 3 tests using a 2-sided t-test. 

4-30 
Feasibility of Exhaust Emission Control 

The above method for projecting high-hour emission results using a certification 

deterioration factor assumes that the catalyst system will control engine-out emissions to the same 

extent, i.e., proportional reduction, over the useful life of the engine. For some engines this may 

not always be the case depending on oil consumption, air-to-fuel ratio and other factors that may 

change the effectiveness of the catalyst over time.4 Our approach also did not explicitly account 

for the fact that manufacturers will generally design the engine and catalyst to provide some 

certification cushion. It appears that most of the engines in Tables 4.3-5 would accommodate the 

above design considerations. However, the projected high-hour results are uncomfortably close to 

the 10 g/kW-hr HC+NOx standard for engine number 6820. In these cases, such factors can be 

accounted for by the engine manufacturer in the engine family’s research and design phase by 

either improving the durability of the engine (see the discussion below) or designing the catalyst to 

account for degradation in catalyst effectiveness over time, e.g, more precious metal loading, 

larger catalyst volume, dividing the catalyst into two separate pieces within the exhaust stream, 

etc. 

The technical feasibility of the Phase 3 standard for Class I engines is supported by a 

number of Small SI engine manufacturers.29,30,31,32 Also, a manufacturer of emission controls 

specifically indicated the types of hardware that may be needed to comply with new standards.33 

That manufacturer concluded that, depending on the application and engine family, either catalyst 

or electronic engine controls should be able to achieve emission standards as low as 9 g/kW-hr 

HC+NOx. As demonstrated above, we believe the standard of 10 g/kW-hr HC+NOx can be 

achieved using catalysts only. However, based on our engineering judgment, we agree that it may 

be possible to achieve the standard with the sole use of electronic engine controls because of the 

more precise management of air-fuel mixtures and ignition spark timing offered by that 

technology. 

We conducted a design and process Failure Mode and Effects Analysis study to assess the 

safety of implementing advanced exhaust emission controls on Small SI engines.34 That work, 

which was based in part on our engine test program, suggests that manufacturers of Class I may 

need to improve the durability of basic engine designs, ignition systems, or fuel metering systems 

for some engines in order to comply with the emission regulations at full useful life. Some of 

these emission-related improvements may include: 

1. Adding a fuel filter or improving the needle and seat design in the carburetor to 

minimize fuel metering problems caused by debris from the fuel tank; 

2. Improving intake manifold design or materials to reduce air leaks; 

3. Upgrading the ignition system design for better ignition spark reliability and durability; 

4. Improving design and manufacturing processes for carburetors to reduce the production 

variability in air-fuel mixtures; and 

4

 Catalyst performance degradation can occur from thermal sintering and catalyst poisoning due to oil 

consumption. Catalyst performance can also improve as engine air-to-fuel ratio slowly drifts towards stoichiometry 

over the useful life of the engine. Air-cooled engines are typically designed with air-to-fuel ratio calibrations that 

take into account lean-drift with extended operation, and are designed with a sufficiently rich air-to-fuel ratio to 

prevent net-lean operation at high hours that could result in engine damage or deteriorating engine performance. 

4-31 
Final Regulatory Impact Analysis 

5. Enhancing exhaust manifold design for better reliability and durability. 

4.3.2.3 Class II Single-Cylinder Gasoline-Fueled Engines 

Class II single-cylinder engines that use gasoline fuel are currently certified and sold under 

the Phase 2 standard in both side-valve and overhead-valve configurations. In 2008, only 2 out of 

107 Class II single-cylinder engine families used side-value designs. Manufacturers certified these 

families under the averaging provisions of the applicable regulations with emission credits that 

were generated by (low emitting) overhead-valve engines. We believe that the Phase 3 standard 

will reduce the number of emission credits available for the certification of side-valve technology. 

As a result, we assume that a number of the remaining Class II side-valve engines may be phased 

out of applicable manufacturer's product line in the future. 

Based on the above, we did not directly assess the technical feasibility of the standard for 

side-valve Class II engines in our test program. Instead we assessed only single-cylinder, 

overhead-valve Class II engines with prototype catalyst/muffler control systems. The primary 

design target for selecting the catalyst configuration for these engines, e.g., volume, substrate, 

design and PGM loading, was to achieve emission levels well below the limit of 8 g/kW-hr 

HC+NOx for this class to accommodate the longer useful life of many of these engines. The 

emission regulations allow useful lives ranging from 250 to1000 hours. For two of the engines 

families, we selected emission control technology with a target of meeting a 3.5 g/kW-hr 

HC+NOx. This included the use of electronic engine and fuel controls to improve the 

management of air-fuel mixtures and ignition spark timing that allow, among other advantages, the 

use of larger catalyst volumes and higher precious metal loading. Secondary design targets were 

primarily safety related and included minimizing CO oxidation at moderate to high load conditions 

to maintain exhaust system surface temperatures comparable to those of the original Phase 2 

compliant systems. The test engines, size, salient catalyst parameters, and use of electronic engine 

controls are shown in Table 4.3-6. 

4-32 
Feasibility of Exhaust Emission Control 

Table 4.3-6: Class II Single-Cylinder Test Engine and Control Technology Description 

Engine 

Displac 

ement 

(L)

 Useful 

Life 

Fuel 

Metering 

Catalyst 

Type 

Catalyst 

Volume 

Catalyst 

Cell 

Density 

Catalyst Loading 

142 0.40 500 hour Carburetor Cordierite 

Ceramic 

Monolith 

250 cc 400 cpsi 40 g/ft3

, 5:0:11 

231 0.50 250 hour Electronic 

Fuel 

Injection 

Metal 

monolith 

280 cc 200 cpsi 70 g/ft3

, 0:5:1 

251 0.50 250 hour Carburetor Cordierite 

Ceramic 

Monolith 

250 cc 400 cpsi 40 g/ft3

, 5:0:1 

253 0.50 250 hour Carburetor Cordierite 

Ceramic 

Monolith 

250 cc 400 cpsi 40 g/ft3

, 5:0:1 

254 0.59 250 hour Carburetor Cordierite 

Ceramic 

Monolith 

250 cc 400 cpsi 40 g/ft3

, 5:0:1 

232 0.49 1,000 hour Electronic 

Fuel 

Injection 

Metal 

monolith 

250 cc 200 cpsi 40 g/ft3

, 5:0:1 

1

 Metal loading expressed as a ratio of platinum:palladium:rhodium. 

Table 4.3-7 shows the results of our catalyst testing on single cylinder Class II engines. 

Only one of the engines was tested at high hours. As explained above for the Class I engines, the 

high-hour results for the remaining engines were projected from their low-hour emission 

performance. We projected high-time emission results for these engines by applying the 

multiplicative deterioration factor from the manufacturer's Phase 2 certification application to the 

low-hour emission test results. The certification deterioration factors ranged from 1.033 to 1.240 

g/kW-hr HC+NOx.5

 As shown, each of the engines achieved the requisite emission limit of 8 

g/kW-hr HC+NOx. 

5

 These results were taken from the 2005 certification results. 

4-33 
Final Regulatory Impact Analysis 

Table 4.3-7: Class II Single-Cylinder Emission Results 

with Advanced Catalytic Control Technology 

Engine 

Age 

(hours)1 

HC+NOx 

(g/kW-hr) 

231 (w/ EFI) 10-40 1.8 ± 0.42 

Projected High 2.2 

232 (w/ EFI) 10-40 2.2 ± 0.1 

Projected High 2.3 

251 10-40 3.1 ± .3 

Projected High 3.8 

253 10-40 4.5 ± 0.1 

Projected High 5.6 

254 10-40 4.0 ± 0.3 

Projected High 4.5 

142 50 2.5 ± 0.6 

500 2.8 

1

 Projected high-hour results estimated by multiplying the low-hour test results by the manufacturer’s 2005 

certification deterioration rate. 2

 “±” values represent the 95% confidence intervals of 3 tests using a 2-sided t-test. 

Again, as with Class I engines, the technical feasibility of the Class II standard was 

supported by a number of Small SI engine manufacturers.35363738 Also, a manufacturer of emission 

controls specifically indicated the types of hardware that may be needed to comply with new 

standards.39 That manufacturer concluded that, depending on application and engine family, a 

catalyst and electronic engine controls should be capable of achieving emission standards as low 

as 7 g/kW-hr HC+NOx. Also, as described above, that same manufacturer concluded that, again 

depending on the application and engine family, either catalyst or electronic engine controls 

should be able to achieve emission standards as low as 9 g/kW-hr HC+NOx. Our standard of 8 

g/kW-hr HC+NOx is in between these two regions. Therefore, based solely on that manufacturer’s 

conclusions, complying with the standard may require control technology ranging from either a 

catalyst or electronic engine controls, or a combination of both. 

Based on the above information, especially our testing as discussed previously, we 

conclude that catalysts do not necessarily need to be used in conjunction with electronic engine 

controls to achieve our standard of 8 g/kW-hr HC+NOx. Either one of those technologies appear 

sufficient. In fact, market forces may cause some manufacturers to shift to electronic controls in 

the absence of more stringent emission standards. Nonetheless, we can not discount the possibility 

that both technologies may be used by some manufacturers to meet the standard on single-cylinder 

Class II engines. (See section 4.2.3.4 for more on electronic engine control and fuel injection.) 

The design and process Failure Mode and Effects Analysis study mentioned previously 

suggests that manufacturers of Class II may need to improve the durability of basic engine designs, 

4-34 
Feasibility of Exhaust Emission Control 

ignition systems, or fuel metering systems for some engines in order to comply with the emission 

regulations at full useful life.40 Some of these emission-related improvements may include: 

1. Reducing the variability in air-fuel mixtures with tighter manufacturing tolerances for 

fuel metering components; and 

2. Improving the ignition system design for better ignition spark reliability and durability. 

4.3.2.4 Class II Multi-Cylinder Gasoline-Fueled Engines 

Gasoline-fueled Class II multi-cylinder engines are very similar to their single-cylinder 

counterparts. Beyond the difference in the number of cylinders, several more Class II multicylinder engine families are currently certified with catalysts and electronic engine control 

technology (either with or without a catalyst). Because of the direct similarities and the use of 

more sophisticated emission control-related technology on some engine families, we find that our 

conclusions regarding the technical feasibility of the 8 g/kW-hr HC+NOx standard for singlecylinder Class II engines is directly transferable to multi-cylinder Class II engines. 

Nonetheless, we also tested two twin-cylinder gasoline-fueled Class II engines from 

different engine families by the same manufacturer.41 The engines were basically identical except 

for their fuel metering systems, i.e., carbureted or electronic fuel injection. We tested both without 

modification and tested the electronic fuel injected engine with a catalyst system that we 

developed. All the tests were conducted when the engines had accumulated 10-15 total hours of 

operating time. 

The results of this testing are shown in Table 4.3-8. As was done for the Class I and II 

single-cylinder engines discussed earlier, we projected emission levels at the end of each engine’s 

useful life using the multiplicative deterioration factors for each engine family as reported in the 

manufacturer’s Phase 2 certification application. As shown, the carbureted engine is projected to 

have end of life emissions of approximately 9.1 g/kW-hr. Based on our experience with singlecylinder engines, compliance with the new standard may require the use of a catalyst for this 

engine family. The unmodified engine with electronic fuel injection is projected to achieve about 

7.3 g/kW-hr. This engine is very close to complying with the standard and will most likely require 

only additional fuel-air mixture and injection timing calibration changes for compliance. 

4-35 
Final Regulatory Impact Analysis 

Table 4.3-8: Class II Multi-Cylinder 

Emission Results with Advanced Catalytic Control Technology 

(V-Twin, Approximately 0.7 Liter Displacement, 3-Way Catalyst) 

Engine 

Configu 

r-ation 

Fuel 

Metering 

Age 

(hours)1 

HC+NO 

x 

(g/kWhr) Catalyst 

Type 

Catalyst 

Volume 

Catalyst 

Cell 

Density 

Catalyst 

Loading 

OEM Carburet 10-40 7.2 -- -- -- --

Projected 9.1 -- -- -- --

OEM EFI 10-40 5.9 -- -- -- --

Projected 7.3 -- -- -- --

OEM w/ EFI 10-40 1.8 Cordierite 700cc 400 cpsi 60 g/ft3 

, 

catalyst Projected 2.2 same same same same 

1

 Projected high-hour results estimated by multiplying the low-hour test results by the manufacturer’s 2004 

certification deterioration rate. 2

 Metal loading expressed as a ratio of platinum:palladium:rhodium. 

Finally, the combination of electronic fuel injection and catalytic exhaust aftertreatment 

clearly has the potential to reduce emissions well below the Phase 3 standard as shown in the table. 

We also evaluated emission control technology for twin-cylinder Class II engines, and by 

analogy all multi-cylinder engines, as part of our safety study.42 Here again we did not find any 

unique challenges in designing catalyst-based control systems for these multi-cylinder engines 

relative to the feasibility of complying with the exhaust standards under normal engine operation. 

However, we did conclude that these engines may present unique concern with the application of 

catalytic control technology under atypical operation conditions. More specifically, the concern 

relates to the potential consequences of combustion misfire or a complete lack of combustion in 

one of the two or more cylinders when a single catalyst/muffler design is used. (A single muffler 

is typically used in Class II applications.) In a single-catalyst system, the unburned fuel and air 

mixture from the malfunctioning cylinder would combine with hot exhaust gases from the other, 

properly operating cylinder. This condition would create high temperatures within the muffler 

system as the unburned fuel and air charge from the misfiring cylinder combusts within the 

exhaust system. This could potentially destroy the catalyst. 

One solution is simply to have a separate catalyst/muffler for each cylinder. Another 

solution is to employ electronic engine controls to monitor ignition and either put the engine into 

“limp-mode” or shut the engine down until the condition clears on re-start or until necessary 

repairs are made, if appropriate. For engines using carburetors, this would effectively require the 

addition of electronic controls. For engines employing electronic fuel injection that may need to 

also employ a small catalyst, it would require that the electronic controls incorporate ignition 

misfire detection if they do not already utilize the inherent capabilities within the engine 

management system. 

4-36 
Feasibility of Exhaust Emission Control 

We expect some engine families will use electronic fuel injection to meet the Phase 3 

standard without employing catalytic aftertreatment. As described earlier, engine families that 

already use these fuel metering systems and are reasonably close to complying with the 

requirement are likely to need only additional calibration changes to the engine management 

system for compliance. In addition, we expect that some engine families which currently use 

carbureted fuel systems will convert directly to electronic fuel injection. Manufacturers may adopt 

this strategy to couple achieving the standard without a catalyst and realizing other advantages of 

using fuel injection such as easier starting, more stable and reliable engine operation, and reduced 

fuel consumption. A few engine manufacturers have confidentially confirmed their plans to use 

electronic fuel injection on some engine families in the future as part of an engine management 

strategy in lieu of using catalysts. 

Our evaluation of electronic fuel injection systems that could be used to attain the new 

standard found that a rather simple, low cost system should be sufficient. We demonstrated this 

proof of concept as part of the engine test program we conducted for our safety study. In that 

program, we fitted two single-cylinder Class II engines with an electronic control unit and fuel 

system components developed for Asian motor-scooters and small-displacement motorcycles. 

The sensors for the system were minimized to include a throttle position sensor, air charge 

temperature sensor, oil temperature sensor, manifold absolute pressure sensor, and a crankshaft 

position sensor. This is in contrast to the original equipment manufacturer (OEM) fuel injection 

systems currently used in some two-cylinder Class II engine applications that employ more 

sophisticated and expensive automotive-based components. 

Regarding the electronic control unit and fuel system components referenced above and in 

previous sections, at least two small engine manufacturers have developed simplified, compact, 

low-cost electronically controlled fuel injection systems for small motorcycles and scooters.4344 

One manufacturer has also developed a general purpose small engine with electronic engine speed 

control technology that eliminates the need for a battery.45,46 These manufacturers have generally 

reported a number of benefits for these advanced systems, including lower emissions and better 

fuel economy. 

4.3.2.5 Class II Gaseous-Fueled Engines 

Engine manufacturers and equipment manufacturers certify engines to run on liquid 

propane gas (LPG) or compressed natural gas (CNG) in a number of applications including indoor 

floor buffers which require low CO emissions. The technology to reduce emissions to the Phase 3 

levels is catalyst due the fact that most engines run closer to stoichiometry than gasoline engines 

and further enleanment to reduce emissions may not be feasible. Due to the high amount of NOx 

compared with HC, as seen from engine data in the certification database, the catalysts may need 

to be designed to reduce NOx and oxidize a limited amount of CO. The EPA 2008 Certification 

Database lists 6 multi-cylinder engine families in the Class II 1000 useful life category as having 

catalysts. Due to this fact, it is assumed that gaseous engines do not have the same concerns with 

multi-cylinder engines and catalysts as gasoline engines. 

4-37 
Final Regulatory Impact Analysis 

4.4 Feasibility of Outboard/Personal Watercraft Marine Engine Standards 

Outboard and personal watercraft (OB/PWC) engines are subject to exhaust emission 

standards which require approximately a 75 percent reduction in hydrocarbon emissions compared 

to conventional carbureted, crankcase-scavenged two-stroke engines. Because of the emission 

credit program included in these requirements, manufacturers are able to sell a mix of old and new 

technology engines to meet the standards on average.

 We are finalizing new exhaust emission standards for OB/PWC engines based on the 

emissions results achievable from the newer technology engines. These technologies have 

primarily been two-stroke direct injection and four-stroke engine designs. For a few model years, 

one manufacturer certified PWC engines with catalytic aftertreatment. This section presents 

emission data for 2004 model year outboard and personal watercraft engines and includes a 

description of the various emission control technologies used. In addition, the possibility of using 

catalytic aftertreatment on OB/PWC engines is discussed. 

4.4.1 OB/PWC Certification Test Data 

When engine manufacturers apply for certification to exhaust emission standards, they 

submit exhaust emission test data. In the case of the OB/PWC engines, the emission standards are 

based on the sum of hydrocarbons and oxides of nitrogen (HC+NOx). Manufacturers submit 

emission test data on HC and NOx to demonstrate their emission levels. Although carbon 

monoxide (CO) emissions are not currently regulated, manufacturers submit data on CO emissions 

as well. 

Three primary technologies are used on Marine SI engines: conventional two-stroke 

engines, direct injection two-stroke engines, and four-stroke engines. Conventional two-stroke 

engines are primarily carbureted, but larger engines may have indirect fuel injection systems as 

well (IDI). Four stroke engines come in carbureted, throttle-body fuel injected (TBI), and multiport fuel injection (MPI) versions. These technologies are discussed in more detail in 

Section 4.4.2. 

4.4.1.1 HC+NOx Certification Data 

Figure 4.4-1 presents HC+NOx certification levels for 2006 model year outboard engines 

and compares this data to the existing and new exhaust emission standards. These certification 

levels are based on test data over the ISO E4 duty cycle with an adjustment for emissions 

deterioration over the regulatory useful life. The certification data set includes engines well above 

and below the emission standard. Manufacturers are able to certify to the standard by meeting it 

on average. In other words, clean engines generate emission credits which offset the debits 

incurred by the engines emitting above the standard. Figure 4.4-2 presents only the data from 

engines that meet the 2006 standard. As shown in these figures, two-stroke direct injection 

engines and four-stroke engines easily meet the 2006 standard. 

4-38 
Feasibility of Exhaust Emission Control 

0 

50 

100 

150 

200 

250 

300 

350 

400 

0 50 100 150 200 

Rated Power [kW] 

HC+NOx [g/kW-hr] 

2s Carb 

2s DI 

4s Carb 

4s EFI 

Baseline 

2006 

2010 

Figure 4.4-1: 2006 MY Outboard HC+NOx Certification Levels 

0 

100 

200 

300 

400 

500 

600 

700 

800 

0 50 100 150 200 

Rated Power [kW] 

CO [g/kW-hr]

2s Carb 

2s DI 

4s Carb 

4s EFI 

proposed 

Figure 4.4-2: 2006 MY New Technology Outboard HC+NOx Certification Levels 

Figures 4.4-3 and 4.4-4 present similar data for personal watercraft engines. These engines 

4-39 
Final Regulatory Impact Analysis 

use similar technology, but the HC+NOx emissions are a little higher on average, presumably due 

to higher average power densities for PWC engines. This difference in emissions is reflected in 

the new HC+NOx standards. 

Figure 4.4-3: 2006 MY Personal Watercraft HC+NOx Certification Levels 

0 

50 

100 

150 

200 

250 

300 

350 

400 

0 50 100 150 200 

Rated Power [kW] 

HC+NOx [g/kW-hr] 

2s Carb 

2s DI 

2s Catalyst 

4s EFI 

Baseline 

2006 

2010 

Figure 4.4-4: 2006 MY New Technology PWC HC+NOx Certification Levels 

0 

5 

10 

15 

20 

25 

30 

35 

40 

45 

50 

0 50 100 150 200 

Rated Power [kW] 

HC+NOx [g/kW-hr] 

2s Carb 

2s DI 

2s Catalyst 

4s EFI 

Baseline 

2006 

2010 

4-40 
Feasibility of Exhaust Emission Control 

4.4.1.2 CO Certification Data 

Although no exhaust emission standards for CO are currently in place for Marine SI 

engines, the technological advances associated with the HC+NOx standards have resulted in lower 

CO emissions for many engines. Figures 4.4-5 and 4.4-6 present reported CO exhaust emission 

levels for certified outboard and personal watercraft engines. These engines use similar 

technology as outboard engines and show similar emission results. 

Figure 4.4-5: Reported CO Emission Levels for 2006 MY Outboard Engines 

0 

100 

200 

300 

400 

500 

600 

0 50 100 150 200 

Rated Power [kW] 

CO [g/kW-hr]

2s Carb 

2s DI 

2s Catalyst 

4s EFI 

2010 

Figure 4.4-6: Reported CO Emission Levels for 2006 MY PWC Engines 

0 

100 

200 

300 

400 

500 

600 

700 

800 

0 50 100 150 200 

Rated Power [kW] 

CO [g/kW-hr]

2s Carb 

2s DI 

4s Carb 

4s EFI 

2010 

4-41 
Final Regulatory Impact Analysis 

4.4.2 OB/PWC Emission Control Technologies 

This section discusses the how general technologies discussed above apply to outboard and 

PWC applications and discusses specific OB/PWC technology. 

4.4.2.1 Conventional Two-Stroke Engines 

As discussed earlier in this chapter, hydrocarbon emissions from two-stroke engines are 

primarily the result of short-circuiting losses where unburned fuel passes through the engine and 

out the exhaust during cylinder charging. Even with an indirect injection system, the air and fuel 

are mixed prior to entering the cylinder. Therefore, even though there is better metering of fuel 

and air than with a carbureted engine, short-circuiting losses still occur. Because of the very rich 

and cool conditions, little NOx is formed. As shown in Figures 4.4-1 and 4.4-2, HC emissions can 

range from 100 to 400 g/kW-hr. CO is formed as a product of incomplete combustion. As a 

result, CO emissions range from 200 to 500 g/kW-hr from these engines. 

4.4.2.2 Direct Injection Two-Stroke Engines 

The primary advantage of direct-injection (DI) for a two-stroke is that the exhaust gases 

can be scavenged with fresh air and fuel can be injected into the combustion chamber after the 

exhaust port closes. As a result, hydrocarbon emissions, fuel economy, and oil consumption are 

greatly improved. Some users prefer direct-injection two-stroke engines over four-stroke engines 

due to the higher power to weight ratio. Today, this technology is used on engines with power 

ratings ranging from 35 to 220 kW. One manufacturer has recently stated its plans to manufacture 

DI two-stroke engines as low as 7.4 kW. 

Most of the DI two-stroke engines currently certified to the current OB/PWC emissions 

standards have HC+NOx emissions levels somewhat higher than certified four-stroke engines. 

These engines also typically have lower CO emissions due to the nature of a heterogeneous 

charge. By injecting the fuel directly into a charge of air in the combustion chamber, localized 

areas of lean air/fuel mixtures are created where CO is efficiently oxidized. PM emissions may be 

higher for DI two-stroke engines than for four-stroke engines because oil is burned in the 

combustion chamber and because of localized rich areas in the fuel injection stream. 

Recently, one manufacturer has introduced a newer technology DI two-stroke engine that 

has comparable HC+NOx emission results as many of the certified four-stroke engines.47 This 

engine makes use of a low-pressure fuel injection nozzle that relies on high swirl to produce 

uniform fuel flow rates and droplet sizes. Also, significant improvements have been made in oil 

consumption. As with the older DI two-stroke designs, CO emissions are much lower than 

comparable four-stroke engines. What is unique about this design is that the manufacturer has 

reported lower PM emissions than for a comparable four-stroke engine. 

4-42 
Feasibility of Exhaust Emission Control 

4.4.2.3 Four Stroke Engines 

Manufacturers currently offer four-stroke Marine SI engines with power ratings ranging 

from 1.5 to 224 kW. These engines are available with carburetion, throttle-body fuel injection, or 

multi-point fuel injection. Carbureted engines are offered from 1.5 to 60 kW while fuel injected 

engines are offered from 22 to 224 kW. One manufacturer has stated that the fuel injection 

systems are too expensive to use on the smaller engine sizes. Most of the four-stroke outboard 

engines above 19 kW have HC+NOx emissions below 16 g/kW-hr and many have emissions 

below 13 g/kW-hr. CO emissions for these engines range from 150 to 250 g/kW-hr. Based on the 

certification data, whether the engine is carbureted or fuel injected does not have a significant 

effect on combined HC+NOx emissions. For PWC engines, the HC+NOx levels are somewhat 

higher. However, many of the four-stroke PWC engines are below 16 g/kW-hr. CO emissions for 

these engines are similar as those for four-stroke outboards. 

4.4.2.4 Catalysts Figure 4.4-7: PWC Engine with Catalyst 

One manufacturer has certified two PWC 

engine models with oxidation catalysts. One engine 

model uses the oxidation catalyst in conjunction with 

a carburetor while the other uses throttle-body fuel 

injection. The engine with throttle-body fuel 

injection has an HC+NOx emission rate of 25 g/kWhr which is significantly below the EPA 2006 

standard. In this application, the exhaust system is 

shaped in such a way to protect the catalyst from 

water and is nearly as large as the engine (see Figure 

4.4-7). Manufacturers have recently begun efforts to 

develop a three-way catalyst system for PWC 

engines used in jet boats. 

Catalysts have not yet been packaged into the 

exhaust system of production outboard marine engines. In current designs, water and exhaust are 

mixed in the exhaust system to help cool the exhaust and tune the engine. Water often works its 

way up through the exhaust system because the lower end in under water and due to pressure 

pulses. As discussed above, salt-water can be detrimental to catalyst performance and durability. 

In addition, the lower unit of outboards are designed to be as thin as possible to improve the ability 

to turn the engine on the back of the boat and to reduce drag on the lowest part of the unit. 

Certainly, the success of packaging catalysts in sterndrive and inboard boats in recent development 

efforts (see below) suggests that catalysts may be feasible for outboards. However, this has not yet 

been demonstrated and significant development efforts would be necessary. 

4.5 Feasibility of Sterndrive/Inboard Marine Engine Standards 

We are establishing exhaust emission standards for spark-ignition sterndrive and inboard 

(SD/I) engines. These new emission standards are supported by data collected on SD/I engines 

4-43 
Final Regulatory Impact Analysis 

equipped with catalysts. This section presents exhaust emission data from baseline SD/I engines 

as well as data from SD/I engines equipped with lean calibrations, exhaust gas recirculation, and 

catalytic control. 

4.5.1 Baseline SD/I Emissions Data 

The vast majority of SD/I engines are four-stroke reciprocating piston engines similar to 

those used in automotive applications. The exceptions are small sales of air boats using aircraft 

piston-type engines and at least one marinizer that uses rotary engines. More than half of the new 

engines sold are equipped with electronic fuel injection while the rest still use carburetors. The 

majority of the electronic fuel injection systems are multi-port injection; however, throttle-body 

injection is also widely used, especially on smaller engines. 

Table 4.5-1 presents baseline emissions for four-stroke SD/I engines built up from 

automotive engine blocks.48,49,50,51,52,53,54 All these data were collected during laboratory tests over 

the ISO E4 duty cycle. Five of these engines are carbureted, one uses throttle-body fuel injection, 

and four use multi-port fuel injection. One of the multi-port fuel injected engines was tested with 

three calibrations. Note that without emissions calibrations performed specifically for low 

emissions, the HC+NOx emissions are roughly equal for the carbureted and fuel injected engines. 

Using the straight average, HC+NOx from the carbureted engines is 15.6 g/kW-hr while it is 16.0 

g/kW-hr from the fuel injected engines (15.1 g/kW-hr if the low HC calibration outlier is 

excluded). 

4-44 
Feasibility of Exhaust Emission Control 

Table 4.5-1: Baseline SD/I Exhaust Emission Data 

Engine 

# 

Power 

[kW] Fuel Delivery System 

HC 

[g/kW-hr] 

NOx 

[g/kW-hr] 

CO 

[g/kW-hr] 

1 79 carburetor 11.2 8.0 281 

2 91 carburetor 4.4 13.9 98 

3 121 carburetor 8.5 6.0 247 

4 153 multi-port electronic fuel injection 4.9 11.7 111 

5 158 carburetor 7.3 6.0 229 

6 167 carburetor 8.0 5.7 174 

7 196 carburetor 4.4 10.3 101 

8 159 throttle-body fuel injection 2.9 8.7 42 

9 185 multi-port electronic fuel injection 5.2 9.7 149 

9 181 #9, low CO calibration 5.8 11.7 48 

9 191 #9, low HC calibration 3.3 18.2 72 

10 219 multi-port electronic fuel injection 4.7 9.4 160 

11 229 multi-port electronic fuel injection 2.7 13.1 44 

A distinct class of SD/I engines are the high-performance engines. These engines are 

similar to SD/I engines except that they are designed for high power output at the expense of 

engine durability. This high power output is typically achieved through higher fuel and air rates, 

larger combustion chambers, and through higher peak engine speeds. In most cases, custom 

engine blocks are used. Even in the engines that use an automotive block, few stock automotive 

engine components are used. Table 4.5-2 presents emission data collected by EPA on five highperformance engines.55,56,57 This data also includes data submitted by a high performance engine 

manufacturer in its public comments on the proposed rule.58 

4-45 
Final Regulatory Impact Analysis 

Table 4.5-2: Baseline High Performance SD/I Exhaust Emission Data [g/kW-hr] 

Power 

[kW] 

Fuel Delivery System HC NOx CO BSFC 

391 multi-port electronic fuel injection 14.7 3.8 243 354 

550 carburetor 13.2a 8.4 253 376 

634 multi-port electronic fuel injection, supercharger 16.9 9.1 135 348 

778 throttle-body fuel-injection, supercharger, 

intercooler 

7.6 4.9 349 448 

802 multi-port electronic fuel injection, supercharger 16.1 9.4 102 299 

466 electronic fuel injection 15.4a 3.2 257 --

410 electronic fuel injection 14.8a 3.9 325 --

466 electronic fuel injection, low emission 

calibrationb 

4.3 10.8 104 --

a

 HC concentration at idle was out of measurement range b

 15% load factor at idle 

4.5.2 Exhaust Gas Recirculation Emission Data 

We collected data on three engines over the ISO E4 marine test cycle with and without the 

use of exhaust gas recirculation (EGR).59,60,61 The first engine was a 6.8 L Ford heavy-duty 

highway engine. Although this was not a marine engine, it uses the same basic technology as SD/I 

engines. The second and third engines were the 7.4 L and 4.3 L SD/I engines used in the catalyst 

development program described below. These engines are marinized versions of GM heavy-duty 

highway engines. The baseline emissions from the 7.4 L engine are a little different than 

presented below in the catalyst discussion because engine head was rebuilt prior to the catalyst 

development work. 

This test data suggests that, through the use of EGR on a SD/I marine engine, a 40-50 

percent reduction in NOx (30-40 percent reduction in HC+NOx) can be achieved. EGR was not 

applied at peak power in this testing because the throttle is wide open at this point and displacing 

fresh air with exhaust gas at this mode of operation would reduce power. We also did not apply 

EGR at idle because the idle mode does not contribute significantly to the cycle weighted NOx. 

4-46 
Feasibility of Exhaust Emission Control 

Table 4.5-3: Exhaust Emission Data Using EGR on the E4 Marine Duty Cycle 

EGR Scenario HC 

[g/kW-hr] 

NOx 

[g/kW-hr] 

CO 

[g/kW-hr] 

Power 

[kW] 

BSFC 

[g/kW-hr] 

6.8 L Engine: baseline

 with EGR 

2.7 

2.7 

13.4 

7.1 

26.5 

24.3 

145 

145 

326 

360 

7.4 L Engine: baseline

 with EGR 

4.5 

4.5 

8.4 

4.8 

171 

184 

209 

209 

349 

356 

4.3 L Engine: baseline

 with EGR 

4.9 

4.2 

11.7 

5.3 

111 

92 

153 

148 

329 

350 

4.5.3 Catalytic Control Emission Data 

4.5.3.1 Engine Testing 

In a joint effort with the California Air Resources Board (ARB), we contracted with 

Southwest Research Institute to perform catalyst development and emission testing on a SD/I 

marine engine.62 This test program was performed on a 7.4 L electronically controlled Mercruiser 

engine with multi-port fuel injection. Figure 4.5-1 illustrates the three primary catalyst packaging 

configurations used in this test program. The upper right-hand picture shows a catalyst packaged 

in a riser extension which would be placed between the lower exhaust manifold and the exhaust 

elbow. This riser had the same outer dimensions as the stock riser extension produced by Mercury 

Marine. The upper left-hand picture shows a catalyst packaged in the elbow. The lower picture 

shows a larger catalyst that was packaged downstream of the exhaust elbow. All of these catalyst 

configurations were water jacketed to prevent high surface temperatures. 

4-47 
Final Regulatory Impact Analysis 

Figure 4.5-1: Three Catalyst Configurations Used in SD/I Test Program 

Table 4.5-4 presents the exhaust emission results for the baseline test and three catalyst 

packaging configurations. In each case a pair of catalysts were used, one for each exhaust 

manifold. For the riser catalyst configuration, we tested the engine with two cell densities, 60 and 

300 cells per square inch (cpsi), to investigate the effects of back-pressure on power. The catalysts 

reduced in HC+NOx in the range of 42 to 77 percent and reduced CO in the range of 46 to 54 

percent. There were no significant impacts on power, and fuel consumption actually improved due 

to the closed-loop engine calibrations necessary to optimize the catalyst effectiveness. At the full 

power mode, we left the engine controls in open-loop and allowed it to operate rich to protect the 

catalysts from over-heating. 

4-48 
Feasibility of Exhaust Emission Control 

Table 4.5-4: Exhaust Emission Data on a 7.4 L SD/I Engine with Various Catalysts 

Catalyst Scenario* 

(cell density, volume, location) 

HC 

[g/kW-hr] 

NOx 

[g/kW-hr] 

CO 

[g/kW-hr] 

Power 

[kW] 

BSFC 

[g/kW-hr] 

baseline (no catalyst) 4.7 9.4 160 219 357 

60 cpsi, 0.7 L, riser 2.5 5.7 81 214 345 

300 cpsi, 0.7 L, riser 1.7 1.9 87 213 349 

400 cpsi, 1.3 L, elbow 2.8 1.1 81 217 337 

200 cpsi, 1.7 L, downstream 2.1 1.2 83 221 341 

*Multiply volume by two for total catalyst volume per engine. 

Additional reductions in HC+NOx and CO can be achieved by using EGR in addition to a 

catalyst. However, the added benefit of EGR is small compared to the emission reductions 

achieved by the catalysts. Regardless, the use of EGR could give manufacturers some flexibility 

in the design of their catalyst. In the catalyst testing work described above on the 7.4 L SD/I 

marine engine, each of the catalyst configurations were tested with and without EGR. Table 4.5-5 

presents these test results. 

Table 4.5-5: Exhaust Emission Data on a 7.4 L SD/I Engine with Catalysts and EGR 

Catalyst Scenario* 

(cell density, volume, location) 

HC+NOx [g/kW-hr] CO [g/kW-hr] 

catalyst catalyst + EGR catalyst catalyst + EGR 

60 cpsi, 0.7 L, riser 8.2 6.8 81 74 

300 cpsi, 0.7 L, riser 3.6 2.8 87 77 

400 cpsi, 1.3 L, elbow 3.9 3.3 81 76 

200 cpsi, 1.7 L, downstream 3.3 2.5 83 73 

*Multiply volume by two for total catalyst volume per engine. 

4.5.3.2 Freshwater Boat Testing 

The catalyst testing described above was a first step in developing and demonstrating 

catalysts that can reduce emissions from Marine SI engines. However, this program only looked at 

catalysts operating in a laboratory. Additional efforts have been made to address issues with using 

catalyst in marine applications by operating engines in boats with catalysts. When the California 

Air Resources Board finalized their catalyst-based emission standards for SD/I engines, they 

agreed to further assessment of the durability of catalyst used in boats through technology review. 

To that end, ARB, industry and the U.S. Coast Guard recently performed a cooperative in4-49 
Final Regulatory Impact Analysis 

boat demonstration program designed to demonstrate the feasibility of using catalysts in SD/I 

applications.63,64 This testing included four boats, two engine types, and four catalysts. The 

catalysts were packaged in the exhaust emission manifold in such a way that they were waterjacketed and capable of fitting within the existing boat design. Each of the boats were operated by 

the U.S. Coast Guard for 480 hours on a fresh water lake. This service accumulation period, 

which was intended to represent the useful life of typical SD/I engines, began in December of 

2003 and was completed in September of 2004. Table 4.5-6 presents a description of the boats 

that were used in the test program. 

Table 4.5-6: Vessel Configurations for Full Useful Life Catalyst Testing 

Boat Engine Catalyst 

Type 

Catalyst 

Volume* 

Catalyst Cell 

Density 

Inboard Straight-Drive Ski Boat 5.7 L, V-8 metallic 1.4 L 300 cpsi 

Inboard V-Drive Runabout 5.7 L, V-8 ceramic 1.7 L 400 cpsi 

22 ft, Sterndrive Bowrider 5.7 L, V-8 metallic 1.4 L 200 cpsi 

19 ft. Sterndrive Runabout 4.3 L, V-6 ceramic 0.7 L 400 cpsi 

*Multiply volume by two for total catalyst volume per engine. 

Exhaust emissions were measured for each catalyst before and after the durability testing.65 

No significant deterioration was observed on any of the catalysts. In fact, all of the 5.7 L engines 

were below the standard of 5 g/kW-hr HC+NOx even after the durability testing. Although the 

zero hour emissions for the 4.3 L engine were less than half of the HC+NOx standard, the final 

emissions for the 4.3 L engine were 15 percent above the HC+NOx standard. However, it should 

be noted that the 4.3L engine was determined to have excessive fuel delivered to one cylinder bank 

and low compression in one of the cylinders. These problems did not appear to be related to the 

catalyst installations and would account for the increase in emissions even without catalyst 

deterioration. Once the calibration on this engine was corrected, a level of 5 g/kW-hr HC+NOx 

was achieved. In addition, no deterioration was observed in the oxygen sensors which were 

installed upstream of the catalysts. 

Significant carbon monoxide emission reductions were achieved, especially at lower power 

modes. At wide-open-throttle, the engines operated in open-loop to prevent the exhaust valves 

from overheating. Additional reductions in CO could be achieved through better fuel air ratio 

control. For instance, although the engines in this test program were fuel injected, batch injections 

were used. In other words, all of the fuel injectors for each bank were firing at the same time 

rather than timing the fuel injection with the valve timing for each individual cylinder. Because of 

this strategy, the engine would need to be calibrated somewhat rich. The next generation of 

electronics for these engines are expected to have more sophisticated control which would allow 

for optimized timing for each fuel injector. 

4-50 
Feasibility of Exhaust Emission Control 

Table 4.5-7: Vessel Configurations for Full Useful Life Catalyst Testing 

Boat Catalyst Aging 

HC 

[g/kW-hr] 

NOx 

[g/kW-hr] 

CO 

[g/kW-hr] 

5.7 L engine 

4.3 L engine 

baseline (no catalyst) 

baseline (no catalyst) 

5.4 

4.9 

6.7 

11.7 

193 

111 

Inboard StraightDrive Ski Boat 0 hours 

480 hours 

1.7 

2.1 

1.0 

1.7 

100 

117 

Inboard V-Drive 

Runabout 

0 hours 

480 hours 

1.8 

1.7 

0.5 

1.0 

87 

102 

22 ft, Sterndrive 

Bowrider 

0 hours 

480 hours 

1.8 

1.5 

0.5 

0.9 

74 

93 

19 ft. Sterndrive 

Runabout 

0 hours 

480 hours* 

1.9 

2.9 

0.5 

2.1 

106 

116 

* after calibration corrected 

4.5.3.3 Saltwater Boat Testing 

Two test programs were initiated to investigate the feasibility of using catalysts on boats 

used in saltwater. In the first program, a small boat with a catalyst was operated over a set of 

operation conditions, developed by industry, to represent the worst case conditions for water 

reversion. In the second test program, three boats were equipped with catalysts and operated for 

an extended period similar to the fresh water testing. 

4.5.3.3.1 Safety, Durability, and Performance Testing 

We contracted with SwRI to test catalysts on a sterndrive engine before and after operation 

on a boat in saltwater.66 The purpose of the testing was to determine if the catalyst would be 

damaged by water reversion in the exhaust manifold. This testing was performed on a 19 foot 

runabout with a 4.3 L sterndrive engine. On previous testing on this boat without a catalyst, SwRI 

found that the only water collected in the exhaust manifold was due to condensation. They were 

able to prevent this condensation by fitting the water jacket around the exhaust system with a 

thermostat to keep the manifold walls from becoming too cool. 

The 4.3 L engine was fitted with a pair of riser catalysts similar to the one illustrated in 

Figure 4.5-1. These catalysts had a cell density of 300 cpsi and a combined volume of 1.4 L. The 

catalysts were water-jacketed to maintain low surface temperatures and, to prevent any possible 

water reversion, cones were inserted in the exhaust elbows. These cones were intended to increase 

the difficulty for water to creep up the inner walls of the exhaust manifold. The water jacketing 

system was fitted with a 82°C thermostat to keep the manifold wall temperatures above the dew 

4-51 
Final Regulatory Impact Analysis 

point of the exhaust gas (~50°C) thereby preventing water condensation in the exhaust manifold. 

Prior to testing, the catalysts were aged using a rapid aging cycle designed to represent 

50,000 miles of vehicle operation. SwRI estimated that this would likely be more severe than 

would be seen over the useful life of an SD/I engine. The engine was then tested for emissions, in 

a test cell, with and without the aged catalysts installed in the exhaust manifold risers. In addition 

to adding the catalysts, the engine fueling was optimized using closed-loop electronic emission 

control. 

After the baseline emission tests, the catalysts were installed on a 19 foot runabout 

equipped with a similar 4.3 L engine used in the emissions test cell. The boat was operated on 

saltwater over a number of safety, durability, and performance tests that were developed by 

industry for heat soak, water ingestion, and engine exhaust back-pressure. In addition, SwRI 

operated the boat over tests that they designed to represent operation and use that would most 

likely induce water reversion. After this boat testing, the catalyst was returned to the laboratory 

for a repetition of the baseline emission tests. 

Table 4.5-8 presents the baseline, aged catalyst, and post boat operation catalyst emission 

test results. No significant deterioration of the catalysts were observed. Prior to boat testing, the 

aged catalysts achieved a 75 percent reduction in HC+NOx and a 36 percent reduction in CO. 

After the boat operation in saltwater, the catalysts achieved a 73 percent reduction in HC+NOx 

and a 34 percent reduction in CO. As described in Chapter 3, if saltwater had reached the catalyst, 

there would have been a large reduction in catalyst efficiency. No salt deposits were observed on 

the catalysts when they were removed from the boat. 

Table 4.5-8: Exhaust Emission Data on a 4.3 L SD/I Engine with Catalysts 

Catalyst Scenario 

HC 

[g/kW-hr] 

NOx 

[g/kW-hr] 

CO 

[g/kW-hr] 

Power 

[kW] 

BSFC 

[g/kW-hr] 

open-loop, no catalyst 4.9 11.7 111 153 329 

closed-loop, no catalyst 4.5 10.4 101 153 327 

aged catalyst pre boat 2.1 2.0 70 154 321 

aged catalyst post boat 2.2 2.3 73 150 327 

4.5.3.3.2 Extended Period In-Use Testing 

We engaged in a test program with the California Resources Board, United States Coast 

Guard, National Marine Manufacturers Association, the Texas Department of Parks and Wildlife, 

and Southwest Research Institute to evaluate three additional engines with catalysts in vessels 

operating on salt-water. Early in the program, two of the three manifolds experienced corrosion in 

the salt-water environment resulting in water leaks and damage to the catalyst. These manifolds 

were rebuilt with guidance from experts in the marine industry and additional hours were 

4-52 
Feasibility of Exhaust Emission Control 

accumulated on the boats. Although the accumulated hours are well below the 480 hours 

performed on fresh water, the completed operation showed no visible evidence of water reversion 

or damage to the catalysts. Table 4.5-9 presents initial exhaust emission results for the three 

engines, equipped with catalysts, included in this test program. 

Table 4.5-9: Baseline Emission Data for Engines/Catalysts in Saltwater Test Program 

Catalyst Scenario 

HC 

[g/kW-hr] 

NOx 

[g/kW-hr] 

CO 

[g/kW-hr] 

Power 

[kW] 

BSFC 

[g/kW-hr] 

Maxum, 4.3L V6, ceramic catalysts 2.1 0.7 136 150 345 

Sea Ray, 5.7L V8, metal catalysts 1.3 0.3 114 191 351 

Malibu, 5.7L V8, ceramic catalysts 0.5 0.4 107 194 348 

4.5.3.4 Production Engines 

At the time of proposal, only one manufacturer was selling inboard Marine SI engines 

equipped with catalysts. These engines are being sold nationwide. The engines are based on 5.7L 

automotive blocks and use electronically controlled fuel injection, twin catalysts, and onboard 

diagnostics. The manufacturer, Indmar, has also performed extended durability testing in a 

saltwater environment. Test data from this engine is presented in Table 4.5-10, with and without 

an applied deterioration factor.67 One advantage that Indmar has promoted with this engine is very 

low CO at part throttle. Part throttle operation is associated with lower boat speeds where the risk 

of CO poisoning is highest. The measured CO over the marine duty cycle is primarily due to 

emissions at wide open throttle, where the engine goes to open loop rich operation to protect the 

exhaust valves from overheating. 

Table 4.5-10: Exhaust Emission Data on a 5.7L Production SD/I Engine with Catalysts 

HC 

[g/kW-hr] 

NOx 

[g/kW-hr] 

CO 

[g/kW-hr] 

measured test results 1.8 2.0 46.6 

with deterioration factor applied 2.0 2.3 51.8 

At this time, three manufacturers have certified engines, equipped with catalysts, to the 5 

g/kW-hr HC+NOx California standards for SD/I engines. Table 4.5-11 presents the certification 

data available from the California Air Resources Board’s Off-Road Certification Database.68 

4-53 
Final Regulatory Impact Analysis 

Table 4.5-11: Catalyst-Equipped SD/I Engines Certified in California 

Manufacturer 

Engine Disp. 

[liters] 

Rated Power 

[kW] 

HC+NOx 

[g/kW-hr] 

Indmar 5.7 

5.7 

230 

230 

3.7 

4.6 

Mercury Marine 1.6 

3.0 

5.0 

5.7 

8.1 

8.1 

75 

101 

194 

246 

280 

317 

4.2 

2.7 

1.8 

3.4 

2.8 

4.6 

Volvo Penta 5.0 

8.1 

239 

298 

3.3 

2.6 

4.5.3.5 CO Emissions Reductions at Low versus High Power 

Under stoichiometric or lean conditions, catalysts are effective at oxidizing CO in the 

exhaust. However, under very rich conditions, catalysts are not effective for reducing CO 

emissions. SD/I engines often run at high power modes for extended periods of time. At these 

temperatures, engine marinizers must calibrate the engine to run rich as an engine protection 

strategy. If the engine were calibrated for a stoichometric air-fuel ratio at high power, high 

temperatures could lead to failures in exhaust valves and cylinder heads. 

All of the data presented above on SD/I engines equipped with catalysts were based on 

engines that used open-loop engine control at high power. As a result, the catalysts achieved little 

reduction in HC and CO at full power (test mode 1). However, NOx reductions were achieved at 

mode 1 because NOx is effectively reduced under rich conditions. 

The catalysts were effective in reducing CO in modes 2 through 5 of the test procedure. In 

these lower power modes, the engines described above saw CO reductions on the order of 80 

percent. However, the weighted values over the test cycle only show about a 50 percent reduction 

in CO because of the high contribution of mode 1 to the total weighted CO value. Studies have 

shown that there is a higher risk of operator exposure to CO at lower boat speeds69 which would 

correspond to lower engine power modes. This suggests that CO reductions at lower power modes 

may be more beneficial than CO reductions at full power. 

To look at the effect of mode 1 on the cycle weighted CO levels, we performed an analysis 

in which we recalculated the CO level for ten catalyst-equipped SD/I engines without mode 1. To 

determine the weighted value without mode 1, the weighting factor for mode 1 was set to zero 

percent and the weighting factors for modes 2 and 3 were each increased so that weighting factors 

would sum to 100 percent. Figure 4.5-2 compares the CO emissions with and without including 

4-54 
Feasibility of Exhaust Emission Control 

mode 1 for these engines. Although mode 1 is only weighted as 6 percent of the test cycle, but 

makes up the majority of the cycle weighted CO value. Based on this analysis, the weighed CO 

level would be 70-90 percent lower if mode 1 were not included in the test procedure. 

Figure 4.5-2: CO Emissions for SD/I Engines Equipped with Catalysts 

with and without Including Mode 1 in the Weighted Results 

0 

20 

40 

60 

80 

100 

120 

140 

1 2 3 4 5 6 7 8 9 10 

Engine 

CO [g/kW-hr] 

E4 Weighting 

Without Mode 1 

4.6 Feasibility of Standard for Marine Generator Sets 

Currently, SI marine generator sets are regulated as Small SI or Large SI engines, 

depending on their size. Most SI marine generators are less than 25 hp and are therefore classified 

as Small SI engines. Generator sets in marine applications are unique in that they use liquidcooled engines. Liquid cooling allows manufacturers to minimize the temperature of hot surfaces 

on marine generators, thereby reducing the risk of fires on a boat. For marine applications, liquid 

cooling is practical because of the nearly unlimited source of cooling water around the boat. 

Another safety issue that has become apparent in recent years is carbon monoxide 

poisoning on boats. Studies have shown that exhaust emissions from engines on boats can lead to 

user exposure of high levels of carbon monoxide.70 The marine industry, Coast Guard, American 

Boat and Yacht Council, and other stakeholders have been meeting regularly over the past several 

years in an attempt to mitigate the risk of CO poisoning in boating.71,72 Mitigation strategies that 

have been discussed at these meetings include labeling, education, diverting the exhaust flow with 

smoke stacks, CO detectors, low CO emission technologies, and emission standards. 

The vast majority of gasoline marine generators are produced by two engine 

manufacturers. Recently, these two manufacturers have announced that they are converting their 

4-55 
Final Regulatory Impact Analysis 

marine generator product lines over to low CO engines.73,74 They have stated that this is to reduce 

the risk of CO poisoning and that this action is a result of boat builder demand. Both 

manufacturers are using a combination of closed-loop electronic fuel injection and catalytic 

control. To date, both of these manufacturers have certified some low CO engines and have stated 

their intent to convert their full product lines in the near future. These manufacturers also make 

use of the electronic controls to monitor catalyst function. Table 4.6-1 presents the 2005 model 

year certification levels for these engines. 

Table 4.6-1: 2005 MY Certification Levels for Low CO Marine Generator Engines 

Engine 

Manufacturer 

Power 

[kW] 

Emission Control System HC+NOx 

[g/kW-hr] 

CO 

[g/kW-hr] 

Kohler Power 

Systems 

10.2 throttle-body injection, O2 sensor, catalyst 7.2 5.2 

Westerbeke 7.5 

17.9 

throttle-body injection, O2 sensor, catalyst 

throttle-body injection, O2 sensor, catalyst 

2.0 

4.4 

0.01 

0.0 

In-use testing has been performed on two marine generator engine equipped with catalysts. 

These engines were installed on rental houseboats and operated for a boating season. Testing was 

first performed with low hours of operation; 108 hours for the 14 kW engine and 159 hours for the 

20 kW.75 The CO performance was reported to be “impressive with exhaust stack CO emissions of 

approximately 200 ppm for a fully warmed generator.” The emissions measured around the boat 

were much lower due to dilution. According to the manufacturer, no significant deterioration has 

been found in the emission performance of the catalysts. Note that the manufacturer recommends 

changing the catalysts at 2000 hours and inspecting for CO at 1000 hours. 

4.7 Test Procedures 

We are making several technical amendments to the existing exhaust emission test 

procedures for Small SI and OB/PWC engines. These amendments are part of a larger effort to 

develop uniform test procedures across all of our programs. We including SD/I engines in these 

test procedures. In addition we are establishing not-to-exceed requirements for Marine SI engines. 

These new procedures are discussed in this section. 

4.7.1 SD/I Certification Test Procedure 

We are using the same certification duty cycle and test procedures for all Marine SI 

engines, including sterndrives and inboards. Table 4.5-6 presents the certification test duty cycle. 

This duty cycle is commonly referred to as the E4 duty cycle and was developed using operational 

data on outboard and sterndrive marine gasoline engines.76 In addition, the E4 duty cycle is 

recommended by the International Standards Organization for use with all spark-ignition 

pleasurecraft less than 24 meters in length.77 Although some Marine SI engines may be used for 

commercial activities, these engines would not likely be made or used differently than those used 

4-56 
Feasibility of Exhaust Emission Control 

for pleasure. 

Table 4.7-1: SI Marine Certification Steady-State Test Duty Cycle 

Mode 

% of Maximum Test 

Speed (MES) 

% of Maximum Torque at 

MES 

% of Maximum Powera

 at 

MES 

Weighting 

Factor 

1 

2 

3 

4 

5 

100 

80 

60 

40 

idle 

100 

71.6 

46.5 

25.0 

0b 

100 

57.2 

27.9 

10.1 

--

0.06 

0.14 

0.15 

0.25 

0.40 

a % power = (% speed) × (% torque) b 15% of maximum torque at MES for high-performance engines 

For high-performance engines, the above test procedure is modified slightly. These 

engines typically have substantial auxiliary loads and parasitic losses even when the vessel does 

not need propulsion power. In addition, these engines are not designed to operate at a low load 

idle and survey data suggests that operators do not spend significant time at zero power idle.78 To 

account for this, for high-performance engines, we revised the test torque at idle speed to be 15 

percent of maximum torque at maximum test speed. 

4.7.2 SI Marine Not-To-Exceed Requirements 

EPA is concerned that if a marine engine is designed for low emissions on average over a 

low number of discrete test points, it may not necessarily operate with low emissions in-use. This 

is due to a range of speed and load combinations that can occur on a vessel which do not 

necessarily lie on the test duty cycle. For instance, the test modes on the E4 duty cycle lie on an 

average propeller curve. However, a propulsion engine may never be fitted with an “average 

propellor.” In addition, a light planing hull boat may operate at much lower torques than a heavily 

loaded boat. 

It is our intent that an engine operate with low emissions under all in-use speed and load 

combinations that can occur on a boat, rather than just the discrete test modes in the five-mode 

duty cycle. To ensure this, we have requirements that extend to typical in-use operation. We are 

establishing not-to-exceed (NTE) requirements similar to those established for marine diesel 

engines. Under this approach, manufacturers would design their engines to comply with a not-toexceed limit, tied to the standard, for HC+NOx and CO, within the NTE zone. In the cases where 

the engine is included in averaging, banking, and trading of credits, the NTE limits would be tied 

to the family emission limits. We would reserve the right to test an engine in a lab or installed in a 

boat to confirm compliance to this requirement. 

We believe there are significant advantages to taking this approach. The test procedure is 

very flexible so it can represent the majority of in-use engine operation and ambient conditions. 

Therefore, the NTE approach takes all of the benefits of a numerical standard and test procedure 

and expands it to cover a broad range of conditions. Also, laboratory testing makes it harder to 

perform in-use testing because either the engines would have to be removed from the vessel or 

4-57 
Final Regulatory Impact Analysis 

care would have to be taken that laboratory-type conditions can be achieved on the vessel. With 

the NTE approach, in-use testing and compliance become much easier because emissions may be 

sampled during normal vessel use. Because this approach is objective, it makes enforcement 

easier and provides more certainty to the industry of what is expected in use versus over a fixed 

laboratory test procedure. 

Even with the NTE requirements, we believe it is still important to retain standards based 

on the steady-state duty cycle. This is the standard that we expect the certified marine engines to 

meet on average in use. The NTE testing is more focused on maximum emissions for segments of 

operation and should not require additional technology beyond what is used to meet the new 

standards. We believe basing the emission standards on a distinct cycle and using the NTE zone to 

ensure in-use control creates a comprehensive program. In addition, the steady-state duty cycles 

give a basis for calculating credits for averaging, banking, and trading. 

We believe that the same technology that can be used to meet the standards over the fivemode certification duty cycle can be used to meet the NTE caps in the NTE zone. We therefore do 

not expect the NTE standards to cause marinizers to need additional technology. We do not 

believe the NTE concept results in a large amount of additional testing, because these engines 

should be designed to perform as well in use as they do over the steady-state five-mode 

certification test. 

4.7.2.1 Shape of the NTE Zone 

The NTE zone is intended to capture typical in-use operation for marine vessels. We used 

two data sources to define this operation. The first data source was the collection of data on 

marine engine operation that was used to develop the ISO E4 steady-state duty cycle.79 Speed and 

torque data were collected on 33 outboards and three sterndrives. This data showed that the 

marine engines generally operated along a propeller curve with some variation due to differences 

in boat design and operation. A propeller curve defines the relationship between engine speed and 

torque for a marine engine and is generally presented in terms of torque as a function of engine 

speed in RPM raised to an exponent. The paper uses an exponent of 1.5 as a general fit, but states 

that the propeller curves for Marine SI applications range from exponents of 1.15 to 2.0. 

The second source of data was a study of marine engine operation recently initiated by the 

marine industry.80 In this study, sixteen boats were tested in the water at various engine speeds. 

These boats included seven sterndrives, three inboards, four outboards, and two personal 

watercraft. To identify the full range of loads at each engine speed, boats were operated both fully 

loaded and lightly loaded. Boats were operated at steady speeds to identify torque at each speed. 

In some cases, the operation was clearly unsafe or atypical. We did not include these operating 

points in our analysis. An example of atypical operation would be with a boat so highly loaded 

that it was operating in an unstable displacement mode with its bow sticking up into the air. 

Figure 4.7-1 presents test data from the two studies as well as the NTE zone for Marine SI 

engines. This zone includes operation above and below the theoretical propeller curve used in the 

E4 duty cycle. Operation below 25 percent of rated speed is excluded because brake-specific 

4-58 
Feasibility of Exhaust Emission Control 

emissions at low loads becomes very high due to low power in the denominator. This approach is 

consistent with the marine diesel NTE zone. The upper and lower borders of the NTE zone are 

designed to capture all of the typical operation that was observed in the two studies. The curve 

functions for these boarders are presented in Figure 4.7-1. 

Figure 4.7-1: NTE Zone and Marine Engine Operation Data 

0 

0.2 

0.4 

0.6 

0.8 

1 

1.2 

0% 20% 40% 60% 80% 100% 120% 

Normalized Speed 

Normalized Torque 

Outboard 

PWC 

Inboard 

Sterndrive 

SAE 901596 

E4 Setpoints 

Prop Curve 

Torque Curve 

NTE 

Zone 

Atypical Points 

1.5 x Speed - 0.16 

Speed^1.5 - 0.08 

Torque MAP 

100% Speed 

40% Speed 

25.3% Torque 

When testing the engine within the NTE zone, only steady-state operation would be 

considered. It is unlikely that transient operation is necessary under the NTE concept to ensure 

that emissions reductions are achieved. We designed the NTE zone to contain the operation near 

an assumed propeller curve that the steady-state duty cycle represents. We believe that the vast 

majority of the operation in the NTE zone would be steady-state. When bringing a boat to plane, 

marine engine operation would be transient and would likely be above the NTE zone. However 

we do not have enough information to quantify this. Also we do not believe that the NTE zone 

should be extended to include areas an engine may see under transient operation, but not under 

steady-state operation. For this reason, we do not believe that adding transient operation to the 

NTE requirements is necessary at this time. We would revise this opinion in the future if there 

were evidence that in-use emissions were increased due to insufficient emission control under 

transient operation 

4-59 
Final Regulatory Impact Analysis 

4.7.2.2 Modal Emission Test Data within the NTE Zone 

The NTE zone has emissions caps which represent a multiplier times the weighted test 

result used for certification. Although ideally the engine should meet the certification level 

throughout the NTE zone, we understand that a cap of 1.0 times the standard is not reasonable 

because there is inevitably some variation in emissions over the range of engine operation. This is 

consistent with the concept of a weighted modal emission test such as the E4 duty cycle. 

In developing the emission caps in the NTE zone, we collected modal HC+NOx and CO 

emission data on a large number of OB, PWC, and SD/I engines. Because limited modal data is 

available in published literature,81,82,83 most of the modal data on outboards and personal watercraft 

was provided confidentially by individual manufacturers. Data on SD/I engines with catalysts was 

collected as part of the catalyst development efforts discussed earlier in this chapter.84,85,86,87 Our 

analysis focuses only on engines using technology that could be used to meet the new standards. 

The modal data is presented in Figures 4.7-2 through 4.7-9 in terms of the modal emission rate 

divided by the weighted E4 average for that engine. Each color bar represents a different engine. 

Because of the large volume of data and differences in engine operation and emissions 

performance, data is presented separately for carbureted 4-stroke, fuel-injected 4-stroke, and 

direct-injected 2-stroke OB/PWC, and for catalyst-equipped SD/I engines. 

Figures 4.7-2 and 4.7-4 present normalized HC+NOx modal data for carbureted and EFI 4-

stroke OB/PWC engines. Note that most of the data points are near or below the E4 weighted 

average (represented by bars near or below 1.0). This is largely due to the exclusion of idle 

operation from the NTE zone compared to the E4 duty cycle that is 40 percent weighted at idle. 

As mentioned above, idle is excluded because brake-specific emissions become very large at low 

power due to a low power figure in the denominator (g/kW-hr). Especially for the carbureted 

engines, higher normalized HC+NOx emissions are observed at the low power end of the NTE 

zone (40 percent speed, 25 percent torque). As shown in Figures 4.7-3 and 4.7-5, a similar trend is 

observed with normalized CO emissions from these engines. 

4-60 
1 2 3 4

1 2 3 4

Feasibility of Exhaust Emission Control 

Figure 4.7-2: Normalized Modal HC+NOx for Carbureted 4-Stroke OB/PWC 

0.0 

0.2 

0.4 

0.6 

0.8 

1.0 

1.2 

1.4 

1.6 

1.8 

2.0 

Normalized Speed, Torque [% of rated] 

Normalized HC+NOx [Modal/E4] 

40%, 25% 60%, 47% 80%, 72% 100%, 100% 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

Normalized Speed, Torque [% of rated] 

Normalized CO [Modal/E4] 

40%, 25% 60%, 47% 80%, 72% 100%, 100% 

Figure 4.7-3: Normalized Modal CO for Carbureted 4-Stroke OB/PWC 

4-61 
1 2 3 4

1 2 3 4

Final Regulatory Impact Analysis 

Figure 4.7-4: Normalized Modal HC+NOx for EFI 4-Stroke OB/PWC 

0.0 

0.2 

0.4 

0.6 

0.8 

1.0 

1.2 

1.4 

1.6 

1.8 

2.0 

Normalized HC+NOx [Modal/E4] 

40%, 25% 

Normalized Speed, Torque [% of rated] 

 60%, 47% 80%, 72% 100%, 100% 

Figure 4.7-5: Normalized Modal CO for EFI 4-Stroke OB/PWC 

2.5 

2.0 

1.5 

Normalized CO [Modal/E4] 1.0 

0.5 

0.0 

40%, 25% 

Normalized Speed, Torque [% of rated] 

 60%, 47% 80%, 72% 100%, 100% 

4-62 
1 2 3 4

Feasibility of Exhaust Emission Control 

Figures 4.7-6 through 4.7-9 present normalized HC+NOx and CO modal data for directinjected 2-stroke OB/PWC engines. Based on the data collected, there appear to be two distinct 

types of direct-injection 2-stroke engines. One manufacturer uses a higher pressure fuel system 

with a unique combustion chamber design for low emissions. Because the modal variation in 

emission results are significantly different for the two engine designs, we designate them headings 

of Type 1 and Type 2 engines and look at them separately for the purposes of this analysis. As 

shown in Figure 4.7-6 and 4.7-7, Type 1 engines tend to have relatively high HC+NOx at low 

power, then fairly low emissions over the rest of the modes. For CO, these engines show much 

less variability between modes. For Type 2 engines, HC+NOx is below the E4 average in the midspeed range as shown in Figure 4.7-8. However, there is a wide degree of variation in how these 

engines behave at low and high speed. Most of these engines seem to have high normalized 

HC+NOx emissions either at low or at high speed. Figure 4.7-9 presents CO values for Type 1 

engines. These engines tend to have high CO at full power with decreasing CO at lower power 

modes. 

Figure 4.7-6: Normalized Modal HC+NOx for Type 1 DI 2-Stroke OB/PWC 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

Normalized Speed, Torque [% of rated] 

Normalized HC+NOx [Modal/E4] 

40%, 25% 60%, 47% 80%, 72% 100%, 100% 

4-63 
1 2 3 4

1 2 3 4

Final Regulatory Impact Analysis 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

Normalized Speed, Torque [% of rated] 

Normalized CO [Modal/E4] 

40%, 25% 60%, 47% 80%, 72% 100%, 100% 

Figure 4.7-7: Normalized Modal CO for Type 1 DI 2-Stroke OB/PWC 

Figure 4.7-8: Normalized Modal HC+NOx for Type 2 DI 2-Stroke OB/PWC 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

Normalized Speed, Torque [% of rated] 

Normalized HC+NOx [Modal/E4] 

40%, 25% 60%, 47% 80%, 72% 100%, 100% 

4-64 
1 2 3 4

Feasibility of Exhaust Emission Control 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

Normalized Speed, Torque [% of rated] 

Normalized CO [Modal/E4] 

40%, 25% 60%, 47% 80%, 72% 100%, 100% 

Figure 4.7-9: Normalized Modal CO for Type 2 DI 2-Stroke OB/PWC 

Figures 4.7-10 and 4.7-11 present normalized HC+NOx and CO modal data for SD/I 

engines equipped with catalysts. All of these engines demonstrated HC+NOx emissions below the 

E4 average in the mid-speed range. However, some of these engines show somewhat higher 

normalized HC+NOx emissions at either the low-power or full power mode. These differences are 

likely a function of catalyst design and location as well as air/fuel calibration. At wide open 

throttle, all of these engines were calibrated to run rich as an engine protection strategy, so 

emission reductions at this mode are due to NOx reductions in the catalyst. Because these engines 

are designed to run rich at full power, high CO emissions were observed at this mode. For the rest 

of the power range, CO emissions were generally below the E4 average for these engines. As part 

of the catalyst development work for SD/I engines, one engine was tested over 26 modes, most of 

which are contained in the NTE zone.88 This engine was tested in its baseline configuration (openloop fuel injection) as well as with three catalyst configurations. The three catalyst configurations 

included one close-coupled to the engine (in the riser), one a little farther downstream (in the 

exhaust elbow), and a larger catalyst external to the existing exhaust manifold. This data provided 

insight into how exhaust emissions throughout the NTE zone for Marine SI engines compare to the 

modal test data on the theoretical propeller curve. This data is presented in Appendix 4A. 

4-65 
1 2 3 4 5 6 7

1 2 3 4 5 6 7

Final Regulatory Impact Analysis 

0.0 

0.2 

0.4 

0.6 

0.8 

1.0 

1.2 

1.4 

1.6 

Normalized Speed, Torque [% of rated] 

Normalized HC+NOx [Modal/E4] 

40%, 25% 50%, 35% 60%, 47% 70%, 59% 80%, 72% 90%, 85% 100%, 100% 

Figure 4.7-10: Normalized Modal HC+NOx for SD/I with Catalysts 

Figure 4.7-11: Normalized Modal CO for SD/I with Catalysts 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

Normalized Speed, Torque [% of rated] 

Normalized CO [Modal/E4] 

40%, 25% 50%, 35% 60%, 47% 70%, 59% 80%, 72% 90%, 85% 100%, 100% 

4-66 
Feasibility of Exhaust Emission Control 

4.7.2.3 NTE Zones and Standards 

As described above, the emissions characteristics of marine engines are largely dependent 

on technology type. Four-stroke engines tend to have relatively constant emission levels 

throughout the NTE zone. In contrast, two-stroke engine tend to have high variability in 

emissions, not only within the NTE zone but between different engine designs as well. Catalystequipped engines tend to have relatively flat emissions profiles, in the NTE zone, when operating 

in closed-loop engine control mode. However, at higher engine power, the engines are calibrated 

to operate with a rich fuel-air ratio, in open-loop control, to protect the exhaust valves and catalyst 

from high exhaust temperatures. This reduces the catalyst efficiency at high power for oxidizing 

HC and CO. 

Since the NPRM was published, we have worked with engine manufacturers to better 

understand the design constraints, operation, and emissions characteristics of marine engines. 

Based on this understanding, and the emission data presented above, we decided to develop 

different NTE standards for three distinct types of engines; 4-stroke, 2-stroke, and catalystequipped. These standards are discussed below. 

We used the modal data presented above and the data on additional operation points 

presented in Appendix 4A to develop NTE limits. These limits are presented as a multiplier times 

the Family Emission Limit (FEL) developed using the 5-mode test procedure. The limits represent 

the levels that can be met by the majority of the marine engines tested. In the case of engines that 

have modal emissions that are somewhat higher than the NTE limits, we believe that these engines 

can be calibrated to meet these limits. In addition, the limits are based on the FELs chosen by 

manufacturers at certification. Therefore, manufacturers would have the option of increasing their 

FELs, in some cases, to bring otherwise problem engines into compliance with the NTE limits. 

4.7.2.3.1 4-Stroke Engines 

The emissions data, presented above, for 4-stroke marine engines suggests that brakespecific emissions rates are relatively constant throughout the NTE zone. One exception is slightly 

higher HC+NOx emissions at low power. To account for this, we are subdividing the NTE zone to 

have a low power subzone below 50 percent of maximum test speed. In this low power subzone, 

the HC+NOx NTE limit is 1.6, while it is 1.4 for the remainder of the NTE zone. The CO NTE 

limit is 1.5 throughout the NTE zone. Figure 4.7-12 presents the NTE zone and subzones. These 

limits would apply to all non-catalyzed four-stroke marine engines. 

4-67 
Final Regulatory Impact Analysis 

Figure 4.7-12: 4-Stroke Engine NTE Zone and Subzones 

0% 

20% 

40% 

60% 

80% 

100% 

120% 

0% 20% 40% 60% 80% 100% 120% 

Normalized Speed 

Normalized Torque 

1.5 x Speed - 0.16 

Speed^1.5 - 0.08 

Torque MAP 

100% Speed 

40% Speed 

25.3% Torque 

50% Speed 

Speed^1.5 (theoretical propeller curve) 

E4 Modes Subzone 1 

Subzone 2 

4.7.2.3.2 2-Stroke Engines 

The emissions data presented above, for 2-stroke direct-injection marine engines suggests 

that these engines have high variability in emissions, not only within the NTE zone but between 

different engine designs as well. Due to this variability, we do not believe that a flat (or stepped) 

limit in the NTE zone could be effectively used to establish meaningful standards for these 

engines. At the same time, we believe that NTE standards are valuable for facilitating in-use 

testing. Therefore, we developed a weighted NTE approach specifically for these engines. In the 

long term, we may consider further emission reduction based on catalytic control applied to 

OB/PWC engines. In this case, we would revisit the appropriateness of the weighted NTE 

approach in the context of those standards. 

Under the weighted NTE approach, emissions data is collected at five test points. These 

test points are idle, full power, and the speeds specified in modes 2-4 of the 5-mode duty cycle. 

Similar to the 5-mode duty cycle, the five test points are weighted to achieve a composite value. 

This composite value must be no higher than 1.2 times the FEL for that engine. 

The difference in this approach, from the 5-mode duty cycle, is that the test torque is not 

specified. During an in-use test, the engine would be set to the target speed and the torque value 

would be allowed to float. In addition, at wide open throttle, the engine speed would be based on 

4-68 
1

Feasibility of Exhaust Emission Control 

actual performance on the boat. Because in-use engines installed in boats do not generally operate 

on the theoretical propeller curve used to define the 5-mode duty cycle, this NTE approach helps 

facilitate NTE testing. 

At each test mode, limits are placed on allowable engine operation. These limits are 

generally based on the NTE zone presented above for 4-stroke engines, but there are two 

exceptions. First, the lower torque limit at 40 percent speed is lowered slightly to better ensure 

that an engine on an in-use boat is capable of operating within the NTE zone. Second, the speed 

range is extended at wide-open throttle for the same reason. Figure 4.7-13 presents this approach. 

Figure 4.7-13: 2-Stroke Engine Weighted NTE Concept 

0% 

20% 

40% 

60% 

80% 

100% 

120% 

0% 20% 40% 60% 80% 100% 120% 

Normalized Speed 

Normalized Torque 

1.5 x Speed - 0.16 

Speed^1.5 - 0.08 

Torque MAP 

40% Speed 

Speed^1.5 (theoretical propeller curve) 

E4 Modes 

Idle 

2 

4 

3 80% Speed 

60% Speed 

During laboratory testing, any point within each of the four non-idle subzones may be 

chosen as test points. These test points do not necessarily need to lie on a propeller curve. It 

should be noted that the actual power measured would be used in the calculation of the weighted 

brake-specific emissions. 

4.7.2.3.3 Catalyst-Equipped Engines 

SD/I engines are anticipated to make use of three-way catalysts to meet the new exhaust 

emission standards. These catalysts are most effective when the fuel-air ratio in the exhaust is near 

stoichiometry. Engine manufacturers use closed-loop control to monitor and maintain the proper 

fuel-air ratio in the exhaust for optimum catalyst efficiency. However, at high power, engine 

4-69 
5.7L NA

6.0L SC Base

?6.0L SC Hi Perf

Final Regulatory Impact Analysis 

manufacturers must increase the fueling rate to reduce the temperature of the exhaust. Otherwise, 

if the exhaust temperature becomes too high, exhaust valves and catalysts may be damaged. 

During rich, open-loop operation at high power, the catalyst is oxygen-limited and less effective at 

oxidizing HC and CO. To address the issue of open-loop catalyst efficiency, we created a high 

power subzone in the NTE zone for catalyst-equipped engines. 

The majority of SD/I engines are based on engine blocks produced by General Motors. To 

determine the appropriate threshold for the high power-subzone, we used temperature data 

supplied by General Motors.89 This data was consistent with confidential data supplied by engine 

marinizers on engine control strategies for catalyst-equipped SD/I engines. Figure 4.7-14 presents 

the stoichiometric limits for engine protection, based on the General Motors study, for three 

different engine designs. 

Figure 4.7-14: GM Study-Stoichiometric Limits for Engine Protection 

Normalized Torque 

100% 

90% 

80% 

70% 

Engine Torque Curve 

1 

2 

5.7L NA 

6.0L SC Base 

?6.0L SC Hi Perf

? 

? 

?

?

70% 80% 90% 100% 

Normalized Speed 

Figure 4.7-15 presents the NTE zone and high power subzone for catalyst-equipped marine 

engines. The shape of the high power subzone is based on the General Motors engine protection 

data. The emission limits are based on data discussed above on SD/I engines, with catalysts, 

operating in open-loop versus closed-loop engine control. 

For catalyst-equipped engines, the largest contribution of emissions over the 5-mode duty 

cycle comes from open-loop operation at Mode 1. In addition, the idle point (Mode 5) is weighted 

4-70 
Feasibility of Exhaust Emission Control 

40 percent in the 5-mode duty cycle, but not included in the NTE zone. For this reason, 

brake-specific emissions throughout most of the NTE zone are less than the weighted average from 

the steady-state testing. For most of the NTE zone, we are therefore requiring a limit equal to the 

duty-cycle standard (i.e., NTE multiplier = 1.0). 

Emission data on catalyst-equipped engines also show higher emissions near full-power 

operation. As discussed above, this is due to the need for richer fuel-air ratios under high-power 

operation to protect the engines from overheating. We are therefore establishing higher NTE 

limits for subzone 1 based on emissions performance during open-loop operation. Specifically, we 

are establishing an HC+NOx limit of 1.5 times the duty-cycle standard. Some HC+NOx control is 

expected in subzone 1 because a three-way catalyst will effectively reduce NOx emissions under 

rich conditions. However, for subzone 1, we are not setting a CO limit. Under rich conditions, a 

three-way catalyst is not at all effective for oxidizing HC or CO emissions. In addition, the cycle 

weighted emission level for CO is primarily driven by Mode 1. 

Figure 4.7-15: Catalyst-Equipped Engine NTE Zone and Subzones 

0% 

20% 

40% 

60% 

80% 

100% 

120% 

0% 20% 40% 60% 80% 100% 120% 

Normalized Speed 

Normalized Torque 

Subzone 2 

1.5 x Speed - 0.16 

Speed^1.5 - 0.08 

Torque MAP 

100% Speed 

40% Speed 

25.3% Torque 

1.2 - 0.5 x Speed 

Speed^1.5 (theoretical propeller curve) 

E4 Modes 

Subzone 1 

4.7.2.4 Ambient Conditions 

Ambient air conditions, including temperature and humidity, may have a significant effect 

on emissions from marine engines in-use. To ensure real world emissions control, the NTE zone 

testing should include a wide range of ambient air conditions representative of real world 

conditions. Because these engines are used in similar environments as marine diesel engines, we 

4-71 
Final Regulatory Impact Analysis 

are applying the same ambient ranges to the Marine SI NTE requirements as already exist for 

marine diesel engine NTE requirements. 

We believe that the appropriate ranges should be 13-30°C (55-86°F) for air temperature 

and 7.1-10.7 grams water per kilogram dry air (50-75 grains/pound of dry air) for air humidity. 

The air temperature ranges are based on temperatures seen during ozone exceedences, except that 

the upper end of the temperature range has been adjusted to account for the cooling effect of a 

body of water on the air above it.90 We are also aware, however, that marine engines sometimes 

draw their intake air from an engine compartment or engine room such that intake air temperatures 

are substantially higher than ambient air temperatures. In this case, we would retain 35°C as the 

end of the NTE temperature range for engines that do not draw their intake air directly from the 

outdoor ambient. 

For NTE testing in which the air temperature or humidity is outside the specified range, we 

require that the emissions must be corrected back to the specified air temperature or humidity 

range. These corrections would be consistent with the equations in 40 CFR Part 91, Subpart E 

except that these equations correct to 25°C and 10.7 grams per kilogram of dry air while the NTE 

corrections would be to the nearest outside edge of the specified ranges. For instance, if the 

outdoor air temperature were higher than 30°C for an engine that drew fresh outdoor air into the 

intake, a temperature correction factor could be applied to the emissions results to determine what 

emissions would be at 30°C. 

Ambient water temperature also may affect emissions due to it’s impact on engine cooling. 

For this reason, we are requiring that the NTE testing include a range of ambient water 

temperatures from 5 to 27°C (41 to 80°F). The water temperature range is based on temperatures 

that marine engines experience in the U.S. in-use. At this time, we are not aware of an established 

correction for ambient water temperature, therefore the NTE zone testing would have to be withing 

the specified ambient water temperature range. 

4.8 Impacts on Safety, Noise, and Energy 

Section 213 of the Clean Air Act directs us to consider the potential impacts on safety, 

noise, and energy when establishing the feasibility of emission standards for nonroad engines. 

Furthermore, section 205 of Public Law 109-54 requires us to assess potential safety issues, 

including the risk of fire and burn to consumers in use, associated with the emission standards for 

nonroad spark-ignition engines under 50 horsepower. As further detailed in the following 

sections, we expect that the exhaust emission standards will either have no adverse affect on 

safety, noise, and energy or will improve certain aspects of these important characteristics. 

4.8.1 Safety 

We conducted a comprehensive, multi-year safety study of nonroad SI engines that focused 

on the following areas where we are finalizing new exhaust standards.91 These areas are: 

- New catalyst-based HC+NOx exhaust emission standards for Class I and II 

4-72 
Feasibility of Exhaust Emission Control 

nonhandheld (NHH) engines; and 

- New HC+NOx exhaust emission standards for outboard and personal watercraft 

(OB/PWC) engines and vessels, and a new CO exhaust emission standard for NHH 

engines used in marine auxiliary applications. 

Each of these four areas is discussed in greater detail in the next sections. 

4.8.1.1 Exhaust Emission Standards for Small Spark-Ignition Engines 

The technology approaches that we assessed for achieving the Small SI engine standards 

included exhaust catalyst aftertreatment and improvements to engine and fuel system designs. In 

addition to our own testing and development effort, we also met with engine and equipment 

manufacturers to better understand their designs and technology and to determine the state of 

technological progress beyond EPA's Phase 2 standards. 

The scope of our safety study included Class I and Class II engine systems that are used in 

residential walk-behind and ride-on lawn mower applications, respectively. Residential lawn 

mower equipment was chosen for the following reasons. 

- Lawn mowers and the closely-related category of lawn tractors overwhelmingly 

represent the largest categories of equipment using Class I and Class II engines. We 

estimate that over 47 million walk-behind mowers and ride-on lawn and turf equipment 

are in-use in the US today. 

- These equipment types represent the majority of sales for Small SI engines. 

- Consumer Product Safety Commission (CPSC) data indicates that more thermal burn 

injuries associated with lawn mowers occur than with other NHH equipment; lawn 

mowers therefore represent the largest thermal burn risk for these classes of engines. 

- General findings regarding advanced emission control technologies for residential lawn 

and garden equipment carry over to commercial lawn and turf care equipment as well 

as to other NHH equipment using Class I and Class II engines. Lawn mower design 

and use characteristics pose unique safety implications not encountered by other NHH 

equipment using these engines (i.e. a mower deck collects debris during operation 

whereas a pressure washer collects no debris). Thus, other NHH equipment may 

employ similar advanced emission control technologies for meeting the standards 

without a corresponding concern regarding the safety issues analyzed in this study. 

We conducted the technical study of the incremental risk on several fronts. First, working 

with the CPSC, we evaluated their reports and databases and other outside sources to identify 

those in-use situations which create fire and burn risk for consumers. The outside sources 

included meetings, workshops, and discussions with engine and equipment manufacturers. The 

following scenarios were identified for evaluation: 

- Thermal burns due to inadvertent contact with hot surface on engine or equipment; 

- Fires from grass and leaf debris on the engine or equipment; 

4-73 
Final Regulatory Impact Analysis 

- Fires due to fuel leaks on hot surfaces; 

- Fires related to spilled fuel or refueling vapor; 

- Equipment or structure fire when equipment is left unattended after being used; 

- Engine malfunction resulting in an ignitable mixture of unburned fuel and air in the 

muffler (engine misfire); and 

- Fire due to operation with richer than designed air-fuel ratio in the engine or catalyst. 

These scenarios cover a comprehensive variety of in-use conditions or circumstances 

which potentially could lead to an increase in burns or fires. They may occur presently or not at 

all, but were included in our study because of the potential impact on safety if they were to occur. 

The focus of the analysis was, therefore, on the incremental impact on the likelihood and severity 

of the adverse condition in addition to the potential causes as it related to the use of more advanced 

emissions control technology. 

Second, we conducted extensive laboratory and field testing of both current technology 

(Phase 2) and prototype catalyst-equipped advanced-technology engines and equipment (Phase 3) 

to assess the emission control performance and thermal characteristics of the engines and 

equipment. This testing included a comparison of exhaust system, engine, and equipment surface 

temperatures using thermal imaging equipment. 

Third, we contracted with Southwest Research Institute (SwRI) to conduct design and 

process Failure Mode and Effects Analyses (FMEA).92 The SwRI FMEA focused on comparing 

current Phase 2 and Phase 3 compliant engines and equipment to evaluate incremental changes in 

risk probability as a way of evaluating the incremental risk of upgrading Phase 2 engines to meet 

Phase 3 emission standards. This is an engineering analysis tool to help engineers and other 

professional staff on the FMEA team to identify and manage risk. In a FMEA, potential failure 

modes, causes of failure, and failure effects are identified and a resulting risk probability is 

calculated from these results. This risk probability is used by the FMEA team to rank problems 

for potential action to reduce or eliminate the causal factors. Identifying these causal factors is 

important because they are the elements that a manufacturer can consider reducing the adverse 

effects that might result from a particular failure mode. 

Our technical work and subsequent analysis of all of the data and information strongly 

indicate that effective catalyst-based standards can be implemented without an incremental 

increase in the risk of fire or burn to the consumer either during or after using the equipment. 

Similarly, we did not find any increase in the risk of fire during storage near typical combustible 

materials. In many cases, the designs used for catalyst-based technology can lead to an 

incremental decrease in such risk. 

More specifically, our work included taking temperature measurements and infrared 

thermal images of both OEM mufflers and prototype catalyst/mufflers on six Class 1 engines and 

three Class 2 engines as part of the safety study. We integrated the emission reduction catalyst 

into the muffler. In doing so, we generally designed heat management features into the 

catalyst/muffler and cooling system. These heat management design elements, all of which were 

not used on every prototype, included: 1) positioning the catalyst within the cooling air flow of the 

4-74 
Feasibility of Exhaust Emission Control 

engine fan or redirecting some cooling air over the catalyst area with a steel shroud; 2) redirecting 

exhaust flow through multiple chambers or baffles within the catalyst/muffler; 3) larger 

catalyst/muffler volumes than the original equipment muffler; and 4) minimizing CO oxidation at 

moderate to high load conditions to maintain exhaust system surface temperatures comparable to 

those of the OEM systems. The measurements and images were taken during various engine 

operating conditions and as the engines cooled down after being shut off.. This latter event, 

termed “hot soak,” is an important consideration since it is often when the operator is in close 

proximity to the engine either performing maintenance or refueling the equipment. 

Figures 4.8-1 and 4.8-2 are an example of the measurements and images taken to compare 

Class 1 engine original equipment (OEM) mufflers to the same engines equipped with prototype 

catalyst/mufflers. The first figure depicts surface temperatures from engine number 244 while 

operated on a laboratory dynamometer over three modes of EPA’s A-cycle steady-state test cycle. 

The second figure shows surface temperatures for the same engine at different times during hot 

soak. The prototype catalyst/muffler system shown in these figures uses one of the most effective 

heat management designs in the safety study. As shown, the catalyst system in this example has 

much lower surface temperatures during both engine operation and hot soak. 

Similar information was collected in the laboratory for Class 2 engines used in lawn 

tractors. However, those tests were conducted on the “raw” engines without the chassis, which is 

an integral part of the overall engine cooling system for most residential Class 2 applications. 

Because of this, we believe it is more appropriate to compare the thermal measurements from field 

testing of the integrated unit. 

The test results for engine 251 are fairly typical of the Class 2 lawn tractor test results. 

During engine operation, the OEM muffler configuration had exposed surface temperatures of 

approximately 200 /C as viewed from both sides of the tractor when cutting moderate to heavy 

grass and peak temperatures as high as 300 to 365 /C. The lawn tractor equipped with engine 253, 

which is from the same engine family as number 251, was fitted with a prototype catalyst/muffler 

exhibited exposed surface temperatures of approximately 115 to 130 /C and peaks of 160 to 190 

/C. The lower temperatures for the prototype catalyst system is in part due to the more effective 

cooling of the catalyst/mufflers due to the re-routing of cooling air through the chassis and other 

heat management design elements. 

The hot soak results for the above engines and two other related Class 2 lawn mowers are 

shown in Figure 4.8-3. The two-minute nominal refueling point after engine shut-down following 

30 minutes of grass-cutting operation is shown for reference. In these tests, both of the engines 

with prototype catalyst/mufflers had lower peak surface temperatures than the OEM muffler 

configurations. 

4-75 
Final Regulatory Impact Analysis 

Figure 4.8-1: Surface Temperature Infrared Thermal Images of Exhaust System 

Components for Class 1 Engine 244 with a Catalyst/Muffler (left) and an OEM Muffler 

(right) at Various Operating Modes. 

4-76 
Feasibility of Exhaust Emission Control 

Figure 4.8-2: Hot Soak Surface Temperature Infrared Thermal Images of Exhaust System 

Components for Class 1 Engine 244 After Sustained Wide Open Throttle and 100 Percent 

Load. 

4-77 
253 w/Catalyst

251 w/OEM Muffler

254 w/Catalyst

256 w/OEM Muffler

Final Regulatory Impact Analysis 

Figure 4.8-3: Hot Soak Peak Surface Temperatures Infrared Thermal Images for Class 2 

Lawn Tractors Following After Approximately 30-Minutes of Grass Cutting. 

0 

20 

40 

60 

80 

100 

120 

140 

160 

180 

200 

220 

240 

260 

280 

300 

320 

340 

360 

380 

400 

Peak Surface Temperature (°C) 

2 - minutes

0

20

40

60

80

100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

Peak Surface Temperature (°C)

0

20

40

60

80

100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

Peak Surface Temperature (°C)

253 w/Catalyst 

251 w/OEM Muffler 

254 w/Catalyst 

256 w/OEM Muffler 

2 - minutes

0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 :00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00

Time (min.:sec.) Time (min.:sec.) e (min.:sec.)

4.8.1.2 Exhaust Emission Standards for Marine SI Engines 

Our analysis of exhaust emission standards for Marine SI engines found that the U.S. Coast 

Guard has comprehensive safety standards that apply to engines and fuel systems used in these 

vessels. Additionally, organizations such as the Society of Automotive Engineers, Underwriters 

Laboratories, and the American Boat and Yacht Council (ABYC) also have safety standards that 

apply in this area. We also found that the four-stroke and two-stroke direct injection engine 

technologies likely to be used to meet the exhaust emission standards contemplated for Marine SI 

engines are in widespread use in the vessel fleet today. These more sophisticated engine 

technologies are replacing the traditional two-stroke carbureted engines. The four-stroke and 

two-stroke direct injection engines meet applicable Coast Guard and ABYC safety standards and 

future products will do so as well. The emission standards must be complementary to existing 

safety standards and our analysis indicates that this will be the case. There are no known safety 

issues with the advanced technologies compared with two-stroke carbureted engines. The 

newer-technology engines arguably provide safety benefits due to improved engine reliability in4-78 
Feasibility of Exhaust Emission Control 

use. Based on the applicability of Coast Guard and ABYC safety standards and the good in-use 

experience with advanced-technology engines in the current vessel fleet, we believe new emission 

standards would not create an incremental increase in the risk of fire or burn to the consumer. 

4.8.2 Noise 

As automotive technology demonstrates, achieving low emissions from spark-ignition 

engines can correspond with greatly reduced noise levels. Direct-injection two-stroke and fourstroke OB/PWC have been reported to be much quieter than traditional carbureted two-stroke 

engines. Catalysts in the exhaust act as mufflers which can reduce noise. Additionally, adding a 

properly designed catalyst to the existing muffler found on all Small SI engines can offer the 

opportunity to incrementally reduce noise. 

4.8.3 Energy 

Adopting new technologies for controlling fuel metering and air-fuel mixing, particularly 

the conversion of some carbureted engines to advanced fuel injection technologies, will lead to 

improvements in fuel consumption. This is especially true for OB/PWC engines where we expect 

the standards to result in the replacement of old-technology two stroke engines with more fuel 

efficient technologies such as two-stroke direct injection or four-stroke engines. Carbureted 

crankcase-scavenged two-stroke engines are inefficient in that 25 percent or more of the fuel 

entering the engine may leave the engine unburned. We estimate a fuel savings of about 61 

million gallons of gasoline from marine engines in 2030, when most boats would be using engines 

complying with the standard. 

The conversion of some carbureted Small SI engines to fuel injection technologies is also 

expected to improve fuel economy. We estimate approximately 7 percent of the Class II engines 

will be converted to fuel injection and that this will result in a fuel savings of about 10 percent for 

each converted engine. This translates to a fuel savings of about 22 million gallons of gasoline in 

2030 when all of the Class II engines used in the U.S. will comply with the Phase 3 standards. By 

contrast, the use of catalyst-based control systems on Small SI engines is not expected to change 

their fuel consumption characteristics. These estimates are discussed in more detail in Chapter 6. 

4-79 
Final Regulatory Impact Analysis 

APPENDIX 4A: Normalized Modal Emissions for a 7.4 L MPI SD/I 

Figure 4A-1: HC+NOx Ratios for 7.4L MPI Engine, Baseline 

140% 

0.4 

0.5 

0.6 

0.4 

0.6 

0.7 

0.4 

0.8 

0.9 

1.0 

1.0 

0.9 

1.0 

1.0 

1.0 

1.1 

0.8 

0.8 

0.9 

0.7 

0.7 

0.6 

0.6 

0.5 

0.8 

NA 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 

Normalized Speed 

120% 

100% 

80% 

60% 

40% 

20% 

0% 

Normalized Torque 

Figure 4A-2: CO Ratios for 7.4L MPI Engine, Baseline 

140% 

1.1 

1.1 

1.3 

0.9 

0.8 

0.7 

0.9 

0.4 

0.5 

0.5 

0.5 

0.3 

0.3 

0.3 

0.4 

0.4 

0.4 

0.5 

0.4 

0.4 

0.5 

0.6 

0.6 

0.8 

1.5 

NA 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 

Normalized Speed 

120% 

100% 

80% 

60% 

40% 

20% 

0% 

Normalized Torque 

4-80 
Feasibility of Exhaust Emission Control 

Figure 4A-3: HC+NOx Ratios for 7.4L MPI Engine, Riser Catalysts 

140% 

120% 

100% 

80% 

60% 

40% 

20% 

0% 

0.6 

0.9 

1.0 

0.7 

0.8 

0.9 

0.7 

0.9 

0.7 

0.7 

0.6 

0.8 

0.8 

0.7 

1.3 

0.5 

0.5 

0.4 

0.4 

0.9 

0.2 

0.3 

1.6 

1.0 

1.3 

NA 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 

Normalized Speed 

Normalized Torque 

Figure 4A-4: CO Ratios for 7.4L MPI Engine, Riser Catalysts 

140% 

Normalized Torque 

120% 

100% 

80% 

60% 

40% 

20% 

0% 

1.9 

1.4 

1.8 

1.8 

1.4 

0.4 

1.8 

0.9 

0.2 

0.2 

0.1 

0.7 

0.3 

0.3 

0.3 

0.4 

0.4 

0.3 

0.4 

0.3 

0.2 

0.0 

0.3 

0.5 

0.6 

NA 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 

Normalized Speed 

4-81 
Final Regulatory Impact Analysis 

Figure 4A-5: HC+NOx Ratios for 7.4L MPI Engine, Elbow Catalysts 

Normalized Torque 

140% 

120% 

100% 

80% 

60% 

40% 

20% 

0% 

0.6 

0.5 

0.5 

0.6 

0.6 

0.4 

0.5 

0.5 

0.4 0.3 

0.3 

0.2 

0.3 

0.5 

0.5 

0.9 

0.6 

0.5 

0.4 

0.5 

0.5 

0.3 

1.7 

1.5 

1.7 

NA 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 

Normalized Speed 

Figure 4A-6: CO Ratios for 7.4L MPI Engine, Elbow Catalysts 

Normalized Torque 

140% 

120% 

100% 

80% 

60% 

40% 

20% 

0% 

1.8 

1.7 

1.2 

1.6 

0.7 

0.5 

0.6 

0.5 

0.4 0.2 

0.1 

0.1 

0.3 

0.3 

0.4 

0.5 

0.4 

0.4 

0.4 

0.3 

0.3 

0.1 

0.4 

0.4 

0.8 

NA 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 

Normalized Speed 

4-82 
Feasibility of Exhaust Emission Control 

Figure 4A-7: HC+NOx Ratios for 7.4L MPI Engine, External Catalysts 

Normalized Torque 

140% 

120% 

100% 

80% 

60% 

40% 

20% 

0% 

0.3 

0.3 

1.3 

0.3 

0.3 

0.3 

0.4 

0.3 

0.3 

0.2 

0.3 

0.3 

0.3 

0.3 

0.4 

0.6 

0.6 

0.2 

0.6 

0.4 

0.1 

0.0 

1.4 

1.1 

0.5 

NA 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 

Normalized Speed 

Figure 4A-8: CO Ratios for 7.4L MPI Engine, External Catalysts 

140% 

120% 

100% 

80% 

60% 

40% 

20% 

0% 

0.5 

0.5 

0.6 

0.3 

0.4 

0.4 

0.3 

0.2 

0.1 

0.1 

0.2 

0.4 

0.3 

0.3 

0.5 

0.7 

0.8 

0.4 

0.7 

0.4 

0.2 

0.0 

0.9 

1.5 

0.1 

NA 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 

Normalized Speed 

4-83 

Normalized Torque 
Final Regulatory Impact Analysis 

Chapter 4 References 

1. Internal Combustion Engine Fundamentals, Heywood, J., McGraw-Hill, Inc., New York, 1988, pp.829-836, 

Docket Identification EPA-HQ-OAR-2004-0008-0203. 

2. Internal Combustion Engine Fundamentals, Heywood, J., McGraw-Hill, Inc., New York, 1988, pp.827-829, 

Docket Identification EPA-HQ-OAR-2004-0008-0203. 

3. Conversation between Tim Fileman at Flagship Marine and Mike Samulski at U.S. EPA, February 10, 1999. 

4. “Benefits and Cost of Potential Tier 2 Emission Reduction Technologies,” Energy and Environmental Analysis, 

Final Report, November 1997, Docket Identification EPA-HQ-OAR-2004-0008-0198. 

5. “Study on Air Assist Fuel Injector Atomization and Effects on Exhaust Emission Reduction,” Saikalis, G., Byers, 

R., Nogi., T.,SAE Paper 930323, 1993, Docket Identification EPA-HQ-OAR-2004-0008-0217. 

6. “Three-Way Catalyst Technology for Off-Road Equipment Powered by Gasoline and LPG Engines,” Southwest 

Research Institute, prepared for CARB, CEPA, and SCAQMD, (SwRI 8778), April 1999, Docket Identification 

EPA-HQ-OAR-2004-0008-0224. 

7. Internal Combustion Engine Fundamentals, Heywood, J., McGraw-Hill, Inc., New York, 1988, pp. 836-839, 

Docket Identification EPA-HQ-OAR-2004-0008-0203. 

8. “Improving the NOx/Fuel Economy Trade-Off for Gasoline Engines with the CCVS Combustion System,” 

Stokes, J., Lake, T., Christie, M., Denbratt, I., SAE Paper 940482, 1994, Docket Identification EPA-HQ-OAR-2004-

0008-0498. 

9. Wu, H., Yang, S., Wang, A., Kao, H., “Emission Control Technologies for 50 and 125 cc Motorcycles in 

Taiwan,” SAE Paper 980938, 1998, Docket Identification EPA-HQ-OAR-2004-0008-0502. 

10. Borland, M., Zhao, F., “Application of Secondary Air Injection for Simultaneously Reducing Converter-In 

Emissions and Improving Catalyst Light-Off Performance,” SAE Paper 2002-01-2803, 2001, Docket Identification 

EPA-HQ-OAR-2004-0008-0497. 

11. Koehlen, C., Holder, E., Guido, V., “Investigation of Post Oxidation and Its Dependency on Engine Combustion 

and Exhaust Manifold Design,” SAE Paper 2002-01-0744, 2002. 

12. “Benefits and Cost of Potential Tier 2 Emission Reduction Technologies,” Energy and Environmental Analysis, 

Final Report, November 1997, Docket Identification EPA-HQ-OAR-2004-0008-0198. 

13. “Reduction of Exhaust Gas Emissions by Using Pd-based Three-way Catalysts,” Lindner, D., Lox, E.S., 

Kreuzer, T., Ostgathe, K., van Yperen, R., SAE Paper 960802, 1996, Docket Identification EPA-HQ-OAR-2004-

0008-0500. 

14. “Overview of Recent Emission Control Technology Developments,” Manufacturers of Emission Controls 

Association, November 18, 1997, Docket Identification EPA-HQ-OAR-2004-0008-0206. 

15. “Application of Accelerated Rapid Aging Test (RAT) Schedules with Poisons: The Effects of Oil Derived 

Poisons, Thermal Degradation and Catalyst Volume on FTP Emissions,” Ball, D., Mohammed, A., Schmidt, W., 

SAE Paper 972846, 1997, Docket Identification EPA-HQ-OAR-2004-0008-0501. 

4-84 
Feasibility of Exhaust Emission Control 

16. “Update Heavy-Duty Engine Emission Conversion Factors for MOBILE6; Analysis of Fuel Economy, NonEngine Fuel Economy Improvements, and Fuel Densities,” prepared by Arcadis for U.S. EPA, EPA420-R-006, 

January 2002, Docket Identification EPA-HQ-OAR-2004-0008-0251. 

17. “Overview of Recent Emission Control Technology Developments,” Manufacturers of Emission Controls 

Association, November 18, 1997, Docket Identification EPA-HQ-OAR-2004-0008-0206. 

18. “Catalytic Converter Applications for Two Stroke, Spark-Ignited Marine Engines,” Fujimoto, H., Isogawa, A., 

Matsumoto, N., SAE Paper 951814, 1995, Docket Identification EPA-HQ-OAR-2004-0008-0220. 

19. “Catalytic Converter Applications for Two Stroke, Spark-Ignited Marine Engines,” Fujimoto, H., Isogawa, A., 

Matsumoto, N., SAE Paper 941786, 1994, Docket Identification EPA-HQ-OAR-2004-0008-0218. 

20. “Public Meeting to Consider a Status Report on Catalyst Testing of Spark-Ignition Inboard/Sterndrive 

Pleasurecraft: Staff Report,” State of California; Air Resources Board, October 28, 2004, Docket Identification EPAHQ-OAR-2004-0008-0236. 

21. “Regulatory Impact Analysis—Control of Air Pollution from New Motor Vehicles: Tier 2 Motor Vehicle 

Emissions Standards and Gasoline Sulfur Control Requirements,” U.S. EPA, December 1999, EPA420-R-99-023, 

http://www.epa.gov/otaq/regs/ld-hwy/tier-2/frm/ria/r99023.pdf 

22. “Demonstration of Tier 2 Emission Levels for Heavy Light-Duty Trucks,” J. McDonald and L. Jones, SAE 

2000-01-1957, Docket Identification EPA-HQ-OAR-2004-0008-0496. 

23. “SULEV and ‘Off-Cycle’ Emissions Benefits of a Vacuum-Insulated Catalytic Converter,” Burch, S.D., and J.P. 

Biel, SAE 1999-01-0461, Docket Identification EPA-HQ-OAR-2004-0008-0495. 

24. “Development of an Alternator-Powered Electrically-Heated Catalyst System,” Laing, P.M., SAE 941042, 

Docket Identification EPA-HQ-OAR-2004-0008-0494. 

25. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower”, U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

26. “Nonroad SI Manufacturer Discussion,” Slide 26-700cc Class II/Phase 2 Horizontal V-Twin. U.S. 

Environmental Protection Agency, November 22, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0087. 

27. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower”, U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

28. “Test Results for Small Spark-Ignition Engine Number 258,” Memorandum and Excel spreadsheet from Richard 

Wilcox, Office of Transportation and Air Quality, U.S. Environmental Protection Agency, January 23, 2007, Docket 

Identification EPA-HQ-OAR-2004-0008-0530. 

29. Letter from David Raney, American Honda Motor Co., Inc., to Margo T. Oge, U. S. Environmental Protection 

Agency, September 1, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0304. 

30. Letter from Kent B. Herrick, Tecumseh Products Company, to Margo T. Oge, U. S. Environmental Protection 

Agency, September 7, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0306. 

31. Letter from Jeffrey Cl Shetler, Kawasaki Motors Corp, U.S.A., to Margo T. Oge, U. S. Environmental 

Protection Agency, September 7, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0305. 

4-85 
Final Regulatory Impact Analysis 

32. Letter from James P. Doyle, Kohler Co., to Margo T. Oge, U. S. Environmental Protection Agency, September 

7, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0303. 

33. “Reducing Emissions From Gasoline Platforms at Less Then 20 kW,” Slide 9, B. Walker and A. Gopalkrishna, 

Delphi Automotive, Asian Vehicle Emission Control Conference, Jaipur, Japan, September 22, 2006. EPA-HQOAR-2004-0008-0535. 

34. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower”, Appendix C - FMEA of Small SI Equipment and Engines, U.S. Environmental Protection Agency, 

EPA420-R-06-006, March 2006, Docket Identification EPA-HQ-OAR-2004-0008-0329. 

35. Letter from David Raney, American Honda Motor Co., Inc., to Margo T. Oge, U. S. Environmental Protection 

Agency, September 1, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0304. 

36. Letter from Kent B. Herrick, Tecumseh Products Company, to Margo T. Oge, U. S. Environmental Protection 

Agency, September 7, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0306. 

37. Letter from Jeffrey Cl Shetler, Kawasaki Motors Corp, U.S.A., to Margo T. Oge, U. S. Environmental 

Protection Agency, September 7, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0305. 

38. Letter from James P. Doyle, Kohler Co., to Margo T. Oge, U. S. Environmental Protection Agency, September 

7, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0303. 

39. “Reducing Emissions From Gasoline Platforms at Less Then 20 kW,” Slide 9, B. Walker and A. Gopalkrishna, 

Delphi Automotive, Asian Vehicle Emission Control Conference, Jaipur, Japan, September 22, 2006. EPA-HQOAR-2004-0008-0535. 

40. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower”, Appendix C - FMEA of Small SI Equipment and Engines, U.S. Environmental Protection Agency, 

EPA420-R-06-006, March 2006, Docket Identification EPA-HQ-OAR-2004-0008-0329. 

41. “Nonroad SI Manufacturer Discussion,” Slide 26-700cc Class II/Phase 2 Horizontal V-Twin. U.S. 

Environmental Protection Agency, November 22, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0087. 

42. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower,” U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

43. “Research on the New Control Method Using Crankshaft Rotational Changes for Electronically Controlled FI 

System of Small Motorcycle Single Cylinder Engine,” Toichiro Hikichi, Tetsuya Kaneko, and Toshimitsu Nakajima, 

Honda R&D Co., Ldt., SAE Paper 2006-32-0108, Small Engine Technology Conference and Exhibition, San 

Antonio, Texas, November 13-16, 2006, Docket Identification EPA-HQ-OAR-2004-0008. 

44. “Fuel Injection System for Small Motorcycles,” Michihisa Nakamure, Yuuichirou Sawada, and Shigeki 

Hashimoto, Yamaha Motor Co., Ltd., SAE Paper 2003-32-0084, September 2003,Docket Identification EPA-HQOAR-2004-0008. 

45. “Honda Releases the iGX440 Next-Generation General Purpose Engine with Electronic Control Technology–a 

World’s First,” Honda Motor Co., Ldt., Press Release, April 20, 2005, Docket Identification EPA-HQ-OAR-2004-

0008. 

46. “Honda’s iGX Intelligent Engine,” Honda Motor Co., Ldt., Product Information, April 2007, Docket 

Identification EPA-HQ-OAR-2004-0008. 

4-86 
Feasibility of Exhaust Emission Control 

47. “Evinrude E-TEC Presentation; Ann Arbor Michigan,” presented to U.S. EPA by Fernando Garcia of BRP on 

September 30, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0246. 

48. “Exhaust Emissions from Marine Engines Using Alternate Fuels,” Michigan Automotive Research Corporation, 

Prepared for NMMA, October 8, 1992, Docket Identification EPA-HQ-OAR-2004-0008-0205. 

49. “Effects of Transience on Emissions from Inboard Marine Engines,” EPA memo by Mike Samulski, May 30, 

1996, Docket Identification EPA-HQ-OAR-2004-0008-0209. 

50. Letter from Jeff Carmody, Santa Barbara Air Quality management District, to Mike Samulski, U.S. EPA, July 

21, 1997, Docket Identification EPA-HQ-OAR-2004-0008-0193. 

51. “National Marine Manufacturers Association’s Small Business Boat Builder and Engine Manufacturers 

Comments in Response to EPA’s Initial Regulatory Flexibility Analysis Regarding EPA’s Plans to Propose 

Emission Regulations for Recreational Marine Gas and Diesel Powered Sterndrive/Inboard Engines,” July 12, 1999, 

Docket Identification EPA-HQ-OAR-2004-0008-0213. 

52. “Emissions from Marine Engines with Water Contact in the Exhaust System,” Mace, et. al., SAE Paper 980681, 

1998, Docket Identification EPA-HQ-OAR-2004-0008-0219. 

53. “Marine Gasoline Engine Testing,” Carroll, J., White, J., Southwest Research Institute, Prepared for U.S. EPA, 

September, 2001, Docket A-2000-01, Docket Identification EPA-HQ-OAR-2004-0008-0253. 

54. “Marine Gasoline Engine and Boat Testing,” Carroll, J., Southwest Research Institute, Prepared for U.S. EPA, 

September, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0254. 

55. “Exhaust Emission Testing of Two High-Performance SD/I Marine Engines,” EPA Memo from Mike Samulski 

and Matt Spears, June 23, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0349. 

56. Email from Mark Reichers, Mercury Marine, to Mike Samulski, US EPA, “1075 / 850 Test Data,” June 9, 2005, 

Docket Identification EPA-HQ-OAR-2004-0008-0295. 

57. Email from Mark Reichers, Mercury Marine, to Mike Samulski, US EPA, “525 EFI Baseline Emissions Data,” 

June 10, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0296. 

58. Ray, P., Brown, R., “ Ilmor Comments on the Notice of Proposed Rulemaking for Control of Emissions from 

Nonroad Spark-Ignited Engines and Equipment 72 Fed. Reg. 28,908 (May 18,2007),” August 3, 2007. 

59. “EGR Test Data from a Heavy-Duty Gasoline Engine on the E4 Duty Cycle,” EPA Memo from Joe McDonald 

and Mike Samulski, July 12, 1999, Docket Identification EPA-HQ-OAR-2004-0008-0199. 

60. “Marine Gasoline Engine Testing,” Carroll, J., White, J., Southwest Research Institute, Prepared for U.S. EPA, 

September, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0253. 

61. “Marine Gasoline Engine and Boat Testing,” Carroll, J., Southwest Research Institute, Prepared for U.S. EPA, 

September, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0254. 

62. “Marine Gasoline Engine Testing,” Carroll, J., White, J., Southwest Research Institute, Prepared for U.S. EPA, 

September, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0253. 

63. “Summary of SwRI Project for CARB entitled, ‘Development of Low Emissions SD/I Boats,” White, J., 

Southwest Research Institute, August 14, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0263. 

4-87 
Final Regulatory Impact Analysis 

64. “Development of Low Emissions; SD/I Boats; Project Update,” Carrol, J., Southwest Research Institute, 

September 11, 2003, Docket Identification EPA-HQ-OAR-2004-0008-0264. 

65. “Public Meeting to Consider a Status Report on Catalyst Testing of Spark-Ignition Inboard/Sterndrive 

Pleasurecraft: Staff Report,” State of California; Air Resources Board, October 28, 2004, Docket Identification EPAHQ-OAR-2004-0008-0236. 

66. “Marine Gasoline Engine and Boat Testing,” Carroll, J., Southwest Research Institute, Prepared for U.S. EPA, 

September, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0254. 

67. E-mail from Rich Waggoner, Indmar, to Mike Samulski, U.S. EPA, “SBREFA notes from Indmar,” July 24, 

2006, Docket Identification EPA-HQ-OAR-2004-0008-0438. 

68. http://www.arb.ca.gov/msprog/offroad/cert/cert_results.php?order=0, February 14, 2008. 

69. Garcia, A., Beamer, B., Earnest, G., “In Depth Survey Report of Carbon Monoxide Emissions and Exposures on 

Express Cruisers Under Various Operating Conditions,” National Institute for Occupational Safety and Health, 

Report No. EPHB 289-11a, January 2006, Docket Identification EPA-HQ-OAR-2004-0008-0396. 

70. Garcia, A., Beamer, B., Earnest, G., “In Depth Survey Report of Carbon Monoxide Emissions and Exposures on 

Express Cruisers Under Various Operating Conditions,” National Institute for Occupational Safety and Health, 

Report No. EPHB 289-11a, January 2006, Docket Identification EPA-HQ-OAR-2004-0008-0396. 

71. “Summary of Government/Industry Carbon Monoxide Workshop and Two Follow-Up Meetings,” Memo from 

Mike Samulski, U.S. EPA to Docket OAR-2004-0008, March 31, 2004, Docket Identification EPA-HQ-OAR-2004-

0008-0008. 

72. “Carbon Monoxide Follow-up Meeting; Miami FL – IBEX Show; Minutes,” American Boat and Yacht Council, 

October 19, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0286. 

73. “News Release: Floating Environmental Laboratory Demonstrates Westerbeke’s Safe-COTM Ultra-Low CO 

Emissions,” Westerbeke Engines & Generators, September 26, 2005, Docket Identification EPA-HQ-OAR-2004-

0008-0298. 

74. “Create the Right Atmosphere; Kohler Marine Generators Helping Make Boating Safer,” Presented by Kohler 

Power Systems at the 2005 International Boatbuilders’ Exhibition and Conference, October 20, 2005, Docket 

Identification EPA-HQ-OAR-2004-0008-0292. 

75. Zimmer, A., Earnest, G., Kurimo, R., “An Evaluation of Catalytic Emission Controls and Vertical Exhaust 

Stacks to Prevent Carbon Monoxide Poisonings from Houseboat Generator Exhaust,” National Institute for 

Occupational Safety and Health, EPHB 171-36a, September 2005, Docket Identification EPA-HQ-OAR-2004-0008-

0397. 

76. “Duty Cycle for Recreational Marine Engines,” Morgan, E., Lincoln, R., SAE Paper 901596, 1990, Docket 

Identification EPA-HQ-OAR-2004-0008-0216. 

77. “Reciprocating Internal Combustion Engines – Exhaust Emission Measurement – Part 4: Test Cycles for 

Different Engine Applications,” ISO/DIS 8178-4, International Standards Organization, Docket Identification EPAHQ-OAR-2004-0008-0503. 

78. Ray, P., Brown, R., “ Ilmor Comments on the Notice of Proposed Rulemaking for Control of Emissions from 

Nonroad Spark-Ignited Engines and Equipment 72 Fed. Reg. 28,908 (May 18,2007),” August 3, 2007. 

4-88 
Feasibility of Exhaust Emission Control 

79. Morgan, E., Lincoln, R., “Duty Cycle for Recreational Marine Engines,” SAE Paper 901596, 1990, Docket 

Identification EPA-HQ-OAR-2004-0008-0216. 

80. Carroll, J., “Determination of Operating Ranges of Marine Engines,” prepared by Southwest Research Institute 

for the National Marine Manufacturers Association, August 2004, Docket Identification EPA-HQ-OAR-2004-0008-

0255. 

81. Samulski, M., “Exhaust Emission Testing of a Two-Stroke and a Four-Stroke Marine Engine; Results and 

Procedures,” U.S. EPA, Memo to Docket #A-92-98, Docket Identification EPA-HQ-OAR-2004-0008-0097. 

82. Wasil, J., Montgomery, D., Strauss, S., Bagley, S., “Life Assessment of PM, Gaseous Emissions, and Oil Usage 

in Modern Marine Outboard Engines,” SAE-GRAZ 43, Society of Automotive Engineers International, 2004, 

Docket Identification EPA-HQ-OAR-2004-0008-0262. 

83. Klak, Joe, “Marine NTE Zones,” Bombardier Recreational Products, October 26, 2006, Docket Identification 

EPA-HQ-OAR-2004-0008-0508. 

84. “Marine Gasoline Engine Testing,” Carroll, J., White, J., Southwest Research Institute, Prepared for U.S. EPA, 

September, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0253. 

85. “Marine Gasoline Engine and Boat Testing,” Carroll, J., Southwest Research Institute, Prepared for U.S. EPA, 

September, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0254. 

86. “Summary of SwRI Project for CARB entitled, ‘Development of Low Emissions SD/I Boats,” White, J., 

Southwest Research Institute, August 14, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0263. 

87. “Development of Low Emissions; SD/I Boats; Project Update,” Carrol, J., Southwest Research Institute, 

September 11, 2003, Docket Identification EPA-HQ-OAR-2004-0008-0264. 

88. “Marine Gasoline Engine Testing,” Carroll, J., White, J., Southwest Research Institute, Prepared for U.S. EPA, 

September, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0253. 

89. Mantey, C., “GMPT Study – Stoich Limits for Engine Protection,” Presented by General Motors to EPA on 

November 19, 2007. 

90. Memorandum from Mark Wolcott to Charles Gray, “Ambient Temperatures Associated with High Ozone 

Concentrations,” U.S. EPA, September 6, 1984, Docket Identification EPA-HQ-OAR-2004-0008-0235. 

91. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower,” U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

92. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower,” U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

4-89 

Feasibility of Evaporative Emission Control 

CHAPTER 5: Feasibility of Evaporative Emission Control 

Section 213(a)(3) of the Clean Air Act presents statutory criteria that EPA must evaluate 

in determining standards for nonroad engines and vehicles including marine vessels. The 

standards must "achieve the greatest degree of emission reduction achievable through the 

application of technology which the Administrator determines will be available for the engines 

or vehicles to which such standards apply, giving appropriate consideration to the cost of 

applying such technology within the period of time available to manufacturers and to noise, 

energy, and safety factors associated with the application of such technology." This chapter 

presents the technical analyses and information that form the basis of EPA's belief that the new 

evaporative emission standards are technically achievable accounting for all the above factors. 

The evaporative emission standards for Small SI equipment and Marine SI vessels are 

summarized in the Executive Summary. This chapter presents available emissions data on 

baseline emissions and on emission reductions achieved through the application of emission 

control technology. In addition, this chapter provides a description of the test procedures for 

evaporative emission determination. 

Evaporative emissions from equipment and vessels using spark-ignition (SI) engines can 

be very high. This is largely because Small SI and Marine SI applications generally have fuel 

tanks that are vented to the atmosphere and because materials used in the construction of the 

plastic fuel tanks and hoses generally have high permeation rates. Evaporative emissions can be 

grouped into five categories: 

DIURNAL: Gasoline evaporation increases as the temperature rises during the day, 

heating the fuel tank and venting gasoline vapors. We also include, under this heading, diffusion 

losses which are vapors that will escape from an open vent even without a change in 

temperature. 

PERMEATION: Gasoline molecules can saturate plastic fuel tanks and rubber hoses, 

resulting in a relatively constant rate of emissions as the fuel continues to permeate through these 

components. 

RUNNING LOSSES: The hot engine and exhaust system can vaporize gasoline when the 

engine is running. 

HOT SOAK: The engine remains hot for a period of time after the engine is turned off 

and gasoline evaporation continues. 

REFUELING: Gasoline vapors are always present in typical fuel tanks. These vapors are 

forced out when the tank is filled with liquid fuel. 

5-1 
Final Regulatory Impact Analysis 

5.1 Diurnal Emissions 

In an open fuel tank, the vapor space is at atmospheric pressure (typically about 14.7 psi), 

and contains a mixture of fuel vapor and air. At all temperatures below the fuel's boiling point, 

the vapor pressure of the fuel is less than atmospheric pressure. This is also called the partial 

pressure of the fuel vapor. The partial pressure of the air is equal to the difference between 

atmospheric pressure and the fuel vapor pressure. For example, in an open-vented fuel tank at 

60/F, the vapor pressure of typical gasoline is about 4.5 psi. In this example, the partial pressure 

of the air is about 10.2 psi. Assuming that the vapor mixture behaves as an ideal gas, then the 

mole fractions (or volumetric fractions) of fuel vapor and air is equal to their respective partial 

pressures divided by the total pressure; thus, the fuel would be 31 percent of the mixture 

(4.5/14.7) and the air would be 69 percent of the mixture (10.2/14.7). 

Diurnal emissions occur when the fuel temperature increases, which increases the 

equilibrium vapor pressure of the fuel. For example, assume that the fuel in the previous 

example was heated to 90/F, where the vapor pressure that same typical fuel is about 8.0 psi. To 

maintain the vapor space at atmospheric pressure, the partial pressure of the air would need to 

decrease to 6.7 psi, which means that the vapor mixture must expand in volume. This forces 

some of the fuel-air mixture to be vented out of the tank. When the fuel later cools, the vapor 

pressure of the fuel decreases, contracting the mixture, and drawing fresh air in through the vent. 

When the fuel is heated again, another cycle of diurnal emissions occurs. It is important to note 

that this is generally not a rate-limited process. Although the evaporation of the fuel can be 

slow, it is generally fast enough to maintain the fuel tank in an essentially equilibrium state. 

As fuel is used by the engine, and the liquid fuel volume decreases, air is drawn into the 

tank to replace the volume of the fuel. (Note: the decrease in liquid fuel could be offset to some 

degree by increasing fuel vapor pressure caused by increasing fuel temperature.) This would 

continue while the engine was running. If the engine was shut off and the tank was left 

overnight, the vapor pressure of the fuel would drop as the temperature of the fuel dropped. This 

would cause a small negative pressure within the tank that would cause it to fill with more air 

until the pressure equilibrated. The next day, the vapor pressure of the fuel would increase as the 

temperature of the fuel increased. This would cause a small positive pressure within the tank 

that would force a mixture of fuel vapor and air out. In poorly designed gasoline systems, where 

the engine or exhaust is very close to the fuel tank the engine/exhaust heating may cause large 

amounts of gasoline vapor to be vented directly to the atmosphere. 

Several emission-control technologies can be used to reduce diurnal evaporative 

emissions. Many of these technologies also control running loss and hot soak emissions and 

some could be used to control refueling emissions. We believe manufacturers will have the 

opportunity use a wide variety of technology approaches to meet the evaporative emission 

standards. The advantages and disadvantages of the various possible emission-control strategies 

are discussed below. This section summarizes the data and rationale supporting the diurnal 

emission standard for Marine SI vessels and Small SI equipment presented in the Executive 

Summary. 

5-2 
Feasibility of Evaporative Emission Control 

5.1.1 Baseline Emissions 

5.1.1.1 Marine Vessels 

We tested two aluminum marine fuel tanks in their baseline configurations for diurnal 

emissions. Aluminum fuel tanks were used so that permeation emissions would not occur during 

the testing. The 17 gallon aluminum tank was constructed for this testing, but is representative 

of a typical marine fuel tank; the 30 gallon aluminum tank was removed from an 18 foot 

runabout. The fuel tanks were tested with the venting through a length of 5

/8 inch hose to ensure 

that the emissions measured were a direct result of the fuel temperature heating and not diffusion 

through the vent (see Section 5.1.3). The advantage of using the aluminum fuel tanks for this 

testing was to exclude permeation emissions from the measured results. All of the testing was 

performed with fuel tanks filled to 40 percent of capacity with 9RVP1

 test fuel. 

The diurnal test results are presented in units of grams per gallon capacity of the fuel tank 

per day. These units are used because gallons capacity is a defining characteristic of the fuel 

tank. Diurnal vapor formation itself is actually a function of the vapor space above the fuel in 

the fuel tank rather than the total capacity.

 Table 5.1-1 presents the test results compared to anticipated results. The anticipated 

results are based on the Wade model which is a set of theoretical calculations for determining 

diurnal emissions based of fill level, fuel RVP, and temperature profile. These calculations are 

presented in Chapter 3. Although the Wade model over-predicts the vapor generation, it does 

show a similar trend with respect to temperature. To account for this over prediction, we use a 

correction factor of 0.78. This correction factor is based on empirical data1

, has historically been 

used in our automotive emission models, and appears to be consistent with the data presented 

below. 

1

 Reid Vapor Pressure (psi). This is a measure of the volatility of the fuel. 9 RVP represents a typical 

summertime fuel in northern states. 

5-3 
Final Regulatory Impact Analysis 

Table 5.1-1: Baseline Diurnal Evaporative Emission Results (varied temperature) 

Temperatures Capacity 

[gallons] 

Measured 

[g/gallon/day] 

Wade Model 

[g/gallon/day] 

Corrected Wade 

[g/gallon/day] 

22 - 36°C (72 - 96°F) 17 1.40 2.30 1.79 

22 - 36°C (72 - 96°F) 30 1.50 2.30 1.79 

24 - 33°C (74 - 91°F) 30 1.13 1.33 1.04 

22 - 30°C (71 - 86°F) 30 0.88 1.02 0.80 

25 - 31°C (77 - 88°F) 30 0.66 0.88 0.69 

26 - 32°C (78 - 90°F) 30 0.85 1.04 0.81 

28 - 31°C (82 - 87°F) 30 0.47 0.43 0.34 

5.1.1.2 Small SI Equipment 

We contracted with an outside lab for the testing of thirteen Small SI fuel tanks over 

various test temperature profiles.2,3 This testing was performed with the tanks filled to 50 

percent capacity with certification gasoline and is discussed in more detail below in the 

Section 5.2.1. This data is presented in Table 5.1-2. In addition, in cases where the fuel 

temperature profiles were within the input range of the Wade model for diurnal emissions, 

theoretical emissions were also calculated using the same correction factor discussed above for 

marine fuel tanks. As shown below, the measured values are fairly consistent with the 

theoretical values. 

5-4 
Feasibility of Evaporative Emission Control 

Table 5.1-2: Fuel Temperature Measurements During Operation of Small SI Equipment 

Equipment Type Fuel Capacity 

[gallons] 

Temperature 

Profile °C 

Measured HC 

grams/gallon 

Theoretical HC 

grams/gallon 

Riding mower 1.1 

1.4 x 2 

1.7 

2.5 

3.0 

6.5 

6.5 x 2 

15.7 - 28.4 

21.9 - 29.7 

19.5 - 30.3 

27.0 - 35.0 

26.6 - 28.4 

24.3 - 33.2 

20.5 - 23.9 

0.92 

0.88 

0.82 

1.29 

0.25 

1.20 

0.26 

0.91 

0.71 

0.94 

1.16 

0.17 

1.08 

0.23 

Walk-behind 

mower 

0.34 

0.25 

0.22 

23.3 - 33.0 

28.7 - 46.7 

28.7 - 59.7 

0.76 

4.92 

36.9 

1.18 

NA* 

NA* 

Generator set 8.5 

7.0 

20.6 - 25.8 

25.8 - 50.0 

0.45 

9.90 

0.38 

NA* 

Pressure washer 1.8 19.0 - 50.6 11.6 NA* 

* outside the temperature range of the model 

The California Air Resources Board performed diurnal testing on seven pieces of 

handheld equipment and 20 pieces of non-handheld equipment by placing the whole equipment 

in a SHED.4 They filled the fuel tanks to 50 percent with 7 RVP fuel and tested over their 65-

105° F summer day test cycle. Because the entire piece of equipment was included in these 

tests, not only were diurnal venting emissions measured, but tank and hose permeation as well 

(plus any potential leaks). Average test results by equipment type are presented in Table 5.1-3. 

Table 5.1-3: ARB Measurement of Evaporative Emissions from Small SI Equipment 

(7 RVP California Certification Fuel, 50% Fill, 65-105°F) 

Equipment Type Number of Data Points Average Measured HC [grams/day] 

Handheld equipment 7 1.04 

Walk-behind lawnmowers 12 3.51 

Generators 2 11.2 

Riding Mowers 3 8.70 

Edgers 2 1.53 

Tiller 1 4.12 

5-5 
Final Regulatory Impact Analysis 

ARB also performed tests on a subset of the equipment using fuel containing MTBE and 

fuel containing ethanol to investigate fuel effects. They observed nearly a 50 percent increase in 

emissions when an ethanol blend was used compared to an MTBE blend. The reason for this 

increase was not discussed, but may have due to increases in permeation caused by the ethanol 

or due to differences in fuel volatility. On five pieces of equipment, a California wintertime 

cycle (51.6-69.5° F) was used as well. As would be expected, the emissions were reduced 

significantly. The theoretical models predict about an 85 percent reduction in diurnal venting 

emissions and about a 60 percent reduction in permeation. The observed results were about a 70 

percent reduction which is in this range. 

5.1.2 Insulation of the Fuel Tank 

The diurnal vapor generated in a fuel tank is directly related to the diurnal temperature 

profile of the fuel in the tank. A reduction in temperature variation causes less vapor to be 

formed. To investigate this effect, we used insulation around the fuel tank to reduce the effect of 

the ambient air temperature variation on the fuel temperature variation. In our preliminary 

testing, we insulated a 23 gallon rotationally molded marine fuel tank using 3 inch thick 

construction foam with an R-value of 15 as defined by 16 CFR 460.5. This testing was 

performed with the fuel tank vent open to atmosphere. Table 5.1-4 presents the fuel 

temperatures and evaporative emissions over the three day test. 

We tested this fuel tank over a three day diurnal test with an ambient temperature of 72-

96°F. This experiment resulted in a 50 percent reduction in emissions from baseline on the 

highest of these three test days. The baseline emissions were measured to be 2.5 g/gallon/day; 

however, it should be noted that for both the baseline test and the insulated tank tests we did not 

control for permeation or diffusion. Over this test, the emissions decreased for subsequent days. 

We believe this was due to the fuel temperature cycle stabilizing. Although we did not control 

for permeation or diffusion, the results from this preliminary experiment directionally show the 

effect of insulation on diurnal emissions. 

Table 5.1-4: Evaporative Emission Results for Insulated Flat, Plastic Tank 

Test Day SHED Temperature Fuel Temperature Evaporative HC 

Day #1 22-36°C (72-96°F) 22-28°C (72-82°F) 1.2 g/gal/day 

Day #2 22-36°C (72-96°F) 26-30°C (78-86°F) 1.0 g/gal/day 

Day #3 22-36°C (72-96°F) 26-30°C (80-86°F) 0.8 g/gal/day 

In boats with installed fuel tanks, the fuel tank is generally hidden beneath the deck. As a 

result, there is a certain amount of “inherent” insulation caused by the boat itself. This effect is 

increased for a boat that is stored in the water. The water acts as a cooling medium for the fuel 

tank, especially if it is installed in the bottom of the boat. In addition, the thermal inertia of the 

fuel in the tank can act to dampen temperature variation imposed from the diurnal heating of the 

5-6 
Feasibility of Evaporative Emission Control 

ambient air. To investigate this effect, we tested several boats by recording the ambient air 

temperature and fuel temperatures over a series of days. Two boats were tested on trailers 

outside in the summer, two boats were tested on trailers in a SHED, and two boats were tested in 

the water on summer days. Table 5.1-5 presents the average results of this testing. The 

temperature traces are presented in Appendix 5A. 

Table 5.1-5: Ratio of Fuel to Ambient Temperature Swing for Boats 

Boat Type Test Conditions Capacity 

[gallons] 

Fuel Tank 

Fill Level 

Temperature 

Ratio* 

9 ft. personal watercraft outside, on trailer 13 50% 66% 

16 ft. jet boat outside, on trailer 40 50% 52% 

18 ft. runabout in SHED, on trailer 30 40% 68% 

16 ft. jet boat in SHED, on trailer 40 90% 33% 

18 ft. runabout outside, in water 30 100% 19% 

21 ft. deck boat outside, in water 20 90% 27%

 * Average ratio of change in fuel temperature to change in ambient air temperature over test days. 

In their comments on the 2002 proposed rule, the National Marine Manufacturers 

Association presented temperature data on 18 foot runabout, with a 32 gallon tank, tested in a 

SHED with an ambient temperature of 72-96°F.5 The average fuel to ambient temperature ratio 

was 54 percent for this testing. This ratio is in the range of EPA test results for boats tested on a 

trailer. Brunswick also included temperature data in their comments.6 The average days test on 

a boat on the water was 19 percent, which is consistent with our water tests. Brunswick’s 

average for boats tested while stored out of the water was 27 percent which is considerably lower 

than the EPA and NMMA testing. Combining all of the EPA and industry data, the average fuel 

to ambient temperature ratio (based on test days) is about 20 percent for boats in the water and 

50 percent for boats stored out of the water. 

During diurnal testing of lawnmowers, ARB found that the fuel and tank skin 

temperature follow the ambient temperature closely.7

 This same phenomenon would be expected 

for other Small SI equipment as well (and portable fuel tanks) because of the small fuel volumes 

and because these tanks are generally exposed to ambient air. One issue that we considered was 

that Small SI equipment is often stored in garages or sheds. In that case, we were interested in if 

the garage or shed acts to insulate the fuel tanks from ambient temperature swings. ARB 

collected data on four garages and one shed. This data included summer and winter California 

temperature measurements. For each test, the inside and outside temperature were measured for 

five days. This data is presented in Table 5.1-7. For the garages, the inside temperature was 

generally warmer than outside, but the variable temperature swings were smaller. For the shed, 

the inside temperature was warmer and showed higher heat builds than the outside temperature. 

5-7 
Final Regulatory Impact Analysis 

Table 5.1-6 also presents an estimate of the effect on diurnal emissions using the theoretical 

equations presented in Chapter 3. No conclusive evidence of was observed to suggest that these 

fuel tanks are generally subject to inherent insulation. 

Table 5.1-6: Comparison of Ambient to Inside Diurnal Temperature Swings 

Season Enclosure Inside Temperature °C

 Avg T Avg Delta T 

Outside Temperature °C

 Avg T Avg Delta T 

Emission 

Effect 

Winter garage D 

garage G 

garage J 

13.8 

12.1 

13.5 

6.4 

9.2 

2.4 

10.1 

5.8 

8.0 

9.3 

14.3 

7.3 

-8% 

-9% 

-55% 

Summer garage A 

garage D 

garage G 

garage J 

shed 

27.4 

35.9 

27.4 

27.6 

27.1 

3.6 

11.7 

15.7 

8.9 

20.1 

22.4 

30.3 

21.3 

23.7 

23.6 

12.2 

15.6 

19.5 

20.3 

14.1 

-63% 

20% 

23% 

-61% 

119% 

Some of the variance between the fuel temperature and ambient temperature, especially 

for larger fuel tanks, is likely due to the thermal inertia of the fuel in the tank. The fuel has mass 

and therefore takes time to heat up. ARB performed a study in which the fuel temperature and 

ambient temperature were recorded for aboveground storage fuel tanks.8,9 Three fuel tanks sizes 

were included in the study: 350, 550, and 1000 gallons. Because of the large size of these tanks, 

the thermal inertia effects would be expected to be larger than for typical fuel tanks used in 

Marine SI and Small SI applications. For the 350 gallon fuel tank, ARB also measured the effect 

of insulating the fuel tank on temperature. Table 5.1-7 presents the results of this testing. Note 

that the test results are the average of five days. Ambient temperature on these test days 

typically had a minimum in the 60-70/F range and a maximum temperature in the 95-105/F 

range. 

EPA performed testing on 17 gallon marine fuel tank in a SHED over a single 72-96/F 

diurnal test and measured both ambient and fuel temperature.10 This data is also included in 

Table 5.1-7. Note that for the smaller tank, there is little difference between the ambient and fuel 

temperature profiles. However, for larger tanks, the fuel temperature has about a 25-30 percent 

smaller temperature swing than the ambient temperature. Note that the insulated fuel tank had a 

temperature ratio similar to the fuel tank stored in a boat in the water. 

5-8 
Feasibility of Evaporative Emission Control 

Table 5.1.7: Ratio of Fuel to Ambient Temperature for Uninsulated Fuel Tanks 

Fuel Tank Type Tank Capacity [gallons] Temperature Ratio* 

marine fuel tank 17 95% 

aboveground storage tank 

(with insulation) 

350 75% 

(18%) 

aboveground storage tank 550 70% 

aboveground storage tank 1000 76%

 * Average ratio of change in fuel temperature to change in ambient air temperature over test days. 

5.1.3 Diffusion Effect 

For the purposes of this discussion, diffusion refers to the process in which gasoline 

vapor penetrates air in an attempt to equalize the concentration throughout the gas mixture. This 

transport phenomenon is driven by the concentration gradient and by effective area. In the case 

of a mobile source fuel system that has a vent to atmosphere, the fuel vapor concentration is near 

saturation in the fuel tank and near zero outside of the fuel system. Therefore, the diffusion rate 

is primarily a function of the path between the fuel tank and atmosphere. The following equation 

describes the relationship between the flux of gasoline vapor out of the tank, the concentration 

gradient, and the vent path: 

mass ∆C

Flux = = D ×

area × time ∆ x 

where: D = diffusion coefficient (constant) 

)C = concentration gradient 

)x = path length 

area = cross sectional area of vent 

Based on the above equation, diffusion from a tank through a vent hose would be a 

function of the cross-sectional area divided by the length of the hose. Therefore a longer hose 

would theoretically limit fuel vapor venting due to diffusion. Whenever a hydrocarbon (HC) 

molecule escapes from the fuel tank, a new molecule of air enters the fuel tank to replace the 

escaped HC. This brings the concentration of HC vapor in the fuel tank out of equilibrium. To 

balance the partial pressures in the fuel tank, more HC must evaporate as HC in the vapor space 

is depleted. In this way, the vapor concentration in the fuel tank remains saturated. 

5.1.3.1 Marine Fuel Tank Data 

In testing diurnal emissions from fuel tanks with open vents, the configuration of the vent 

can have a significant effect on the measured emissions due to the diffusion of vapor out of any 

5-9 
Final Regulatory Impact Analysis 

opening in the fuel tank. Depending on the size and configuration of the vent, diffusion can 

actually occur when the fuel temperature is cooling. Most marine vessels with an installed fuel 

tank vent through a hose. As shown below this configuration can minimize diffusion. 

To quantify the diffusion component for a typical fuel tank, we ran four 72-96°F diurnal 

tests on a 17 gallon aluminum marine fuel tank using various configurations for venting The 

first configuration was with the fuel cap cracked open and the vent sealed, the second 

configuration was with a 68 cm length of vent hose, and the third configuration was with a 1000 

micron (1 mm) limiting flow orifice in the vent opening. This 1000 micron orifice was large 

enough to allow venting without any measurable pressure increase in the fuel tank during the 

diurnal test. The fourth configuration was a combination of the limited flow orifice and the vent 

hose. Table 5.1-8 presents the results of this testing. 

Table 5.1-8: Diurnal Test Results with Varied Venting Configurations 

Vent Configuration Evaporative HC [g/gallon/day] 

cracked fuel cap 2.05 

68 cm of 5

/8" fuel hose 1.40 

1000 micron orifice 1.47 

1000 micron orifice + 68 cm of 5/8" fuel hose 1.34 

The above testing showed a 50 percent higher emission rate for the tank vented through a 

cracked fuel cap compared to one vented through a hose. In the test with the cracked fuel cap, 

an increase in HC concentration in the SHED was observed throughout the test, even when the 

fuel temperature was cooling. For the other three tests, the HC concentration leveled off when 

the temperature began to cool. This suggests that the difference in measured emissions of 0.6 -

0.7 g/gal/day was due to diffusion losses. 

To further investigate this diffusion effect, we tested the 17 gallon aluminum tank with 

several venting configuration, at two constant temperature settings. Under these conditions, all 

of the measured evaporative emissions would be expected to be due to diffusion. As seen in 

Table 5.1-9, diffusion can be very high with too large of a vent opening unless a vent hose is 

used. The two lengths of vent hose tested did not show a significant difference in diffusion 

emissions. We believe that the vent hose limits diffusion by creating a gradual gradient in fuel 

vapor concentration. 

5-10 
Feasibility of Evaporative Emission Control 

Table 5.1-9: Constant Temperature Test Results with Varied Venting Configurations 

Vent Configuration 22°C (72°F) 

Evaporative HC [g/gal/day] 

36°C (96°F) 

Evaporative HC [g/gal/day] 

1⁄2" I.D. fitting 5.65 10.0 

68 cm of 5

/8" fuel hose 0.11 0.18 

137 cm of 5

/8" fuel hose 0.07 0.24 

1000 micron orifice 0.28 0.41 

The above data suggest that, at least for open vent fuel systems, the size and 

configuration of the venting system can have a significant effect on evaporative emissions. In 

marine applications, there is typically a vent hose attached to the fuel tank. Diffusion emissions 

appear to be minimal if the fuel tank is vented through a length of hose. This is probably 

because the long residence times in the hose cause more opportunities for molecular collisions 

which direct the HC molecules back towards the fuel tank. 

One study looked at the evaporation of liquids from a tube filled to various fill heights.11 

As the fill height decreased (effectively increasing the length of the tube above the liquid 

surface) the evaporation quickly decreased. These results are consistent with the observed 

effects of venting through a hose in our testing. Installed marine fuel tanks typically vent 

through a hose to the outside of the boat; therefore, diffusion losses are likely relatively small for 

these applications. Another study was performed on automotive fuel caps which suggests that a 

crack in the gasket on the fuel cap of 1 percent of the gasket area can result in more than 2 grams 

of HC emissions per day.12 

5.1.3.2 Small SI Fuel Tank Data 

For Small SI applications (and portable marine fuel tanks), the tanks are typically vented 

through an opening in the fuel cap. Therefore, unless the cap is sealed, we would expect 

diffusion emissions to occur. The above data suggest that diffusion can account for a significant 

portion of the evaporative HC emissions measured from a metal tank with a small vent in the cap 

over a 72-96°F diurnal test. Because diffusion would still occur at constant temperature, the 

contribution of diffusion to measured diurnal emissions would increase, on a percentage basis, as 

the diurnal temperature swing approached zero. 

To investigate the effect of fuel cap design on diffusion for Small SI applications, we 

implemented a test program which included four fuel tank configurations (one metal and three 

plastic) and the corresponding fuel caps. These four fuel tanks were taken from lawnmowers 

using engines from the three lawnmower engine manufacturers with the highest U.S. sales and 

represent the majority of lawnmower fuel tanks on the market. Table 5.1-10 presents a 

description of these fuel tanks. 

5-11 
Final Regulatory Impact Analysis 

Table 5.1-10: Lawnmower Fuel Tanks Used in Diurnal/Diffusion Testing 

Tank Tank description Fuel Cap Vent Description 

BM metal, 800 ml Three 1/16" dia. holes drilled in top of cap. Four similar holes 

drilled in fibrous gasket 

BP plastic, 1175 ml Three torturous pathways through plastic gasket, with venting 

between tank/cap threads. (Also performed test using a 

modified cap similar to the cap used on the metal tank.) 

HP plastic, 950 ml Pinhole in gasket center leading to two indentations in rubber 

gasket at mating surface, with venting between tank/cap threads 

TP plastic, 920 ml Four indentations in rubber gasket at mating surface, with 

venting between tank/cap threads 

We contracted with two outside laboratories to perform the diurnal/diffusion tests for the 

Small SI equipment fuel tanks shown above.13,14,15,16 In this effort, the fuel tanks were sealed, 

except for the vents in the fuel cap, and filled to 40 percent of capacity with 9 RVP fuel. These 

tanks were then tested in a mini-SHED over the EPA 72-96°F 24-hour diurnal test procedure. 

To minimize the effect of permeation on the test results, new fuel caps and plastic fuel tanks 

were used for each test that had not been exposed to fuel or fuel vapor prior to the test. 

Under this testing, emissions continued to climb even when temperature was cooling 

back from 96/F to 72/F. These emissions were clearly not driven by temperature, so they were 

determined to represent diffusion emissions. Total diffusion for the test was determined by 

recording the HC emissions that occurred during the last 12 hours of the test (during the cooling 

event) and then multiplying these emissions by two to represent 24 hours. Although the peak 

temperature occurs after nine hours, only the last 12 hours were used to ensure that the fuel in 

the tank was not still heating due to a thermal time lag. Diffusion was then subtracted off the 

total HC measurement to determine non-diffusion diurnal emissions. For the fuel cap with the 

three holes drilled straight through it, the emissions were so high that it went out of measurement 

range near the end of the tests performed by one of the contractors. However, all of the observed 

diffusion rates were linear, making it simple to extrapolate the data where necessary. Table 5.1-

11 presents the diurnal and diffusion data from these tests and compares it to the theoretical 

diurnal emissions using the corrected Wade equations discussed above. Charts in Appendix 5B 

present the time series of the measured HC compared to the mini-SHED temperature. 

5-12 
Feasibility of Evaporative Emission Control 

Table 5.1-11: Diurnal and Diffusion Emissions from Lawnmower Fuel Tanks (g/gal/day) 

over a 72-96-72 °F (22.2-35.6-22.2 °C) Temperature Profile 

Tank Total HC Diffusion Diurnal Wade Diurnal 

BM 47.8 43.6 4.2 1.8 

BP 

BP cap 2* 

2.1 

24.1 

0.1 

19.3 

2.0 

4.8 

1.8 

1.8 

HP 1.6 0.1 1.5 1.8 

TP 2.1 0.2 2.0 1.8 

* modified to be similar to cap on metal tank (BM) 

The fuel caps in the above table for the lawnmower tanks labeled as BM and BP cap 2 

resulted in very high diffusion emissions. Although this fuel cap type is a common design used 

in Small SI applications, it may represent one of the worst case configurations for diffusion. 

There are three small holes in the cap itself, and four small holes in the fibrous material 

imbedded in the inside of the cap. Presumably, this design was intended to minimize fuel from 

splashing out of the tank while still allowing the tank to breathe to prevent pressure or vacuum 

from occurring in the tank. Because the carburetor on this lawnmower is gravity fed, too much 

vacuum in the fuel tank could cause the engine to stall from lack of enough fuel. The reason that 

this may be a worst case configuration is that there is a direct (and relatively large) path for fuel 

vapor to escape from the fuel tank. 

The other three fuel cap designs were also from stock lawnmower fuel systems. In all 

three of these designs, the venting occurred through small grooves in the gasket that seals the 

mating between the fuel cap and the fuel tank. The venting then occurs through the thread paths 

between the cap and tank. As a result, vapor and air must pass through a tortuous pathway to 

enter or leave the tank. This tortuous pathway appears to limit diffusion in much the same way 

as venting through a long hose does. 

The above emission testing was repeated except that the vents in the fuel cap were sealed 

and the tank was vented through a 8 inch length of 1/4" I.D. hose. A lawnmower air intake filter 

was attached to the end of this hose in order to simulate the venting configuration on a 

lawnmower with running loss control. To minimize the effect of permeation, a low permeation 

barrier hose was used that had never before been exposed to fuel or fuel vapor. The test results 

in which the tanks were vented through hoses are presented in Table 5.1-12. 

5-13 
Final Regulatory Impact Analysis 

Table 5.1-12: Diurnal and Diffusion Emissions from Lawnmower Fuel Tanks (g/gal/day) 

with Modified Venting Through Hose/Air Filter to Simulate Running Loss Control 

over a 72-96-72 °F (22.2-35.6-22.2 °C) Temperature Profile 

Tank Total HC 

vent through stock cap 

Total HC 

vent through hose/filter 

Reduction in 

Total HC 

BM 47.8 12.9 34.8 

BP 

BP cap 2* 

2.1 

24.1 

1.9 

1.9 

0.2 

22.2 

HP 1.6 2.0 (0.4) 

TP 2.1 2.9 (0.7) 

* modified to be similar to cap on metal tank (BM) 

As shown in the table above, venting through the hose greatly reduced the measured 

emissions compared to the BM cap vent. When vented through the hose configuration, diffusion 

emissions were on roughly the same order as when the tortuous cap vents were used. This is 

consistent with the data presented earlier on marine fuel tanks vented through a hose. In an inuse running loss system, a valve or limited flow orifice would likely also be in the vent line. 

These components would likely further reduce, or even eliminate, diffusion emissions. 

There was some concern that diffusion may have been underestimated in the above tests 

because air flowing back into the fuel tank during the cooling period may have limited diffusion 

by pulling HC molecules back into the fuel tank. In addition, we believed that testing at constant 

temperature would allow us to more directly measure diffusion. Therefore, the above testing 

was repeated at a constant temperature of 29°C.17,18,19 However, it should be noted that this 

testing may have overestimated diffusion somewhat because of small temperature fluctuations 

(less than 0.5 °C) around the average during the test. Therefore, any HC measurements from the 

“constant” temperature testing may have overstated diffusion due to vapor generated by the 

repeated mini-diurnal cycles during in the test. These test results are presented in Table 5.1-13. 

5-14 
Feasibility of Evaporative Emission Control 

Table 5.1-13: Isothermal [29 °C] Diurnal and Diffusion Emissions from 

Lawnmower Fuel Tanks (g/gal/day) with Modified Venting 

Through Hose/Air Filter to Simulate Running Loss Control 

Tank Total HC 

vent through stock cap 

Total HC 

vent through hose/filter 

Reduction in 

Total HC 

BM 43.2 8.9 34.3 

BP 

BP cap 2* 

1.3 

29.3 

1.0 

1.0 

0.3 

28.3 

HP 1.0 0.8 0.2 

TP 0.9 0.9 0.0 

* modified to be similar to cap on metal tank (BM) 

At constant temperature, the relationship between measured diffusion emissions between 

the venting configurations was consistent with the variable temperature testing. However, the 

indicated diffusion results were somewhat higher. These higher results were influenced by two 

effects. In the variable temperature testing, the diffusion was measured during the cooling 

period when air was being drawn into the fuel tank. This would reduce diffusion into the SHED 

because escaping HC molecules would need to overcome the air flow into the tank. At the same 

time, the constant temperature test may have overstated diffusion due to the measured small 

fluctuations in temperature that may have caused mini-diurnal cycles. Likely, the actual 

diffusion rates are somewhere in-between the results presented in Tables 5.1-11 and 5.1-12. 

Appendix 5B contains data charts that present the results of the Small SI diffusion testing in 

more detail. 

Although the results are presented above on a gram per gallon basis for comparison with 

diurnal emissions, diffusion appears to be more a function of orifice size that fuel tank size. 

Presumably, the diffusion rate on a grams per day basis would be the same through a given 

orifice regardless of size of the vapor space. This is reflected in the data above in that the 

permeation rates on a gram per gallon basis from the lawnmower fuel tanks with holes in the fuel 

cap were much larger than for the marine fuel tank in the testing discussed earlier. At the same 

time, larger fuel tanks may be designed with larger orifice sizes to account for higher amounts of 

vapor expansion in the tank. 

5.1.4 Carbon Canister 

The primary diurnal evaporative emission control device used in automotive applications 

is a carbon canister. With this technology, vapor generated in the tank is vented through a 

canister containing activated carbon (similar to charcoal). The fuel tank must be otherwise 

sealed; however, this only results in a minimal amount of pressure in the tank. The activated 

carbon collects and stores the hydrocarbons. Once the engine is running, purge air is drawn 

through the canister and the hydrocarbons are burned in the engine. These carbon canisters 

5-15 
Final Regulatory Impact Analysis 

generally are about a liter in size for an automotive tank and have the capacity to store three days 

of vapor over the test procedure conditions. For automotive applications, this technology 

reduces diurnal emissions by more than 95 percent. 

In a marine application, the vessel may sit for weeks without an engine purge; therefore, 

canisters were not originally considered to be a practical technology for controlling diurnal vapor 

from boats. Since that time, however, we have collected information showing that, during 

cooling periods, the canister is purged sufficiently enough so that it can be used effectively to 

reduce diurnal emissions. When the fuel in the tank cools, fresh air is drawn back through the 

canister into the fuel tank. This fresh air will partially purge the canister and return 

hydrocarbons back to the fuel tank.20,21 Therefore, the canister will have open sites available to 

collect vapor during the next heating event. Test data presented below show that a canister that 

starts empty is more than 90 percent effective at capturing hydrocarbons until it reaches 

saturation. Once the canister reaches saturation, it is still capable of achieving more than a 60 

percent reduction in diurnal emissions due to passive purging. Passive purging occurs as a result 

of fresh air that is pulled through the canister during fuel tank cooling periods. With the addition 

of an engine (active) purge, greater reductions would be expected. 

We tested a 30 gallon aluminum fuel tank over three, multiple-day diurnal cycles with 

and without a charcoal canister. The carbon canister was 2.1 liters in size with a butane working 

capacity (BWC) of 11 g/dL (based on EPA test) and was aged using multiple 24 hour diurnal 

cycles prior to testing. In our first test, the fuel temperature was cycled from 72-96°F using a 

heating blanket in a SHED for at total of 28 days. Because we were not able to test over 

weekends, we brought the fuel temperature down to 72°F and held it to prevent the generation or 

purging of vapors. On Mondays, we saw higher vapor rates than the rest of the week which was 

likely due to the vapor redistributing itself equally through the canister over the weekend when 

the temperature was held constant. Under normal conditions, the continued diurnal cycles would 

maintain a gradient through the canister and this effect would not occur. Appendix 5C contains 

graph showing the results of the 28 day test. This test is interesting because we began with a 

purged canister and were able to observe the loading of the canister over the first few days. It 

took about five test days to achieve canister breakthrough and another ten test days before the 

canister loading/purging cycle stabilized. 

Once the canister was saturated, the emissions results stabilized. Therefore, for the 

subsequent canister tests, we began with a loaded canister and tested for four days. The results 

were collected beginning after the first night so that the canister would have a cooling cycle for 

back-purge. Table 5.1-14 presents our test results for the baseline and stabilized with canister 

diurnal emission rates. 

5-16 
Feasibility of Evaporative Emission Control 

Table 5.1-14: EPA Diurnal Emission Test Results With and Without a Canister 

on a 30 Gallon Aluminum Marine Fuel Tank [g/gal/day] 

Temperature Range Baseline With a Canister Reduction 

22.2-35.6°C (72-96°F) 1.50 0.52 65% 

25.6-32.2°C (78-90°F) 0.85 0.28 67% 

27.8-30.6°C (82-87°F) 0.47 0.14 71% 

Marine manufacturers raised the concern that the high humidity in the areas where boats 

are used would be detrimental to this technology. They stated that the carbon could become 

saturated with water vapor, thereby reducing the available sites for hydrocarbon capture. These 

manufacturers also commented that carbon canisters may not be able to survive shocks and 

vibration that would be seen on a boat. Carbon canisters have been used in automotive 

applications for decades, which are subject to high humidity (rainy days) and shocks and 

vibration. In addition, one manufacturer, who is a primary supplier to the automotive industry, 

has developed a new grade of carbon that has low moisture adsorption characteristics and about 

40 percent harder than typical automotive carbon.22,23 This carbon has been designed specifically 

for marine applications. Based on this manufacturer’s testing, more than a 60 percent reduction 

in diurnal vapor emissions can be achieved with a passive purge system. This reduction is based 

on a canister capacity of 0.03 to 0.04 liters of carbon per gallon of fuel tank capacity. 

The National Marine Manufacturers Association performed a test program has to 

demonstrate the durability of carbon canisters in marine applications. This test program included 

installing carbon canisters on a total of fourteen boats made by four boat builders.24 These boat 

types included cruisers, runabouts, pontoon boats, and fishing boats. The carbon canister design 

used for these boats is a simple cylinder that can be cut to length with end caps and mounting 

brackets. The canisters were installed in the vent lines and a valve was added to prevent liquid 

fuel from reaching the canister during refueling. These canisters use marine grade carbon. At 

the end of this test program, each of the canisters were tested for working capacity and each 

canister showed proper performance.25 

Another issue that has been raised has been the ability of carbon canisters to pass the 

Coast Guard flame test. The carbon canisters could be made out of a variety of materials, 

including metal. Even a thin-walled nylon fuel tank could be manufactured to pass the flame test 

if a flame-resistant coating or cover were used. One study attempted to ignite a carbon canister 

that was loaded with fuel vapor.26 When an ignition source was applied to the canister vent, the 

gases exiting the canister were ignited and burned as a small, steady flame until the canister tube 

opening began to melt. No explosion occurred. In any case, as with the vent line, if the carbon 

canister is self-draining, then the canister would not likely hold the five ounces of fuel, specified 

in 33 CFR 183.558, to trigger the need for flame protection. 

Manufacturers have raised the concern that it is common for liquid fuel to pass out the 

5-17 
Final Regulatory Impact Analysis 

vent line during refueling. If there were a canister in the vent line it would become saturated 

with fuel. While this would not likely cause permanent damage to the canister, we believe 

marine fuel systems should prevent liquid fuel from exiting the vent line for both environmental 

and safety reasons. A float valve or small orifice in the entrance to the vent line from the fuel 

tank would prevent liquid fuel from reaching the canister or escaping from the tank. Any 

pressure build-up from such a valve would cause fuel to back up the fill neck and shut off the 

fuel dispensing nozzle. In addition, 

a vapor space should be included to Figure 5.1-1: Canister Installation Example 

account for fuel expansion. These 

Fill neck 

Vapor space 

(for fuel expansion) 

Valve or 

orifice 

Canister 

Vent line 

fuel system design considerations are 

straight-forward, long used in other 

applications,27 are applicable to 

boats,28 and would have the added 

benefit of minimizing fuel spillage, 

from boats, into the water. One 

possible design for preventing fuel 

from reaching the canister, due to 

refueling, sloshing, or expansion, is 

shown in Figure 5.1-1. 

Recently, the California Air Resources Board (ARB) performed diurnal emission testing 

on a commercial mower and a generator with 6 gallon fuel tanks and 0.65 liter canisters.29 Their 

testing showed better than 50 percent reductions, on average, in diurnal emissions through the 

use of canisters without an engine purge. The testing was performed over two diurnal 

temperature ranges, 53-71°F and 65-105°F which are intended to represent an average day and a 

high temperature episode. 

Over a decade ago, testing performed on a car showed similar results.30 A 1988 Regency 

98 with an 18 gallon fuel tank was subjected to an 8 day diurnal without driving. This diurnal 

was performed using a 72-96°F temperature profile, a tank filled to 40 percent with 9RVP 

gasoline, and a purged canister at the beginning of testing. The test results showed, that the 

canister loading/purging cycle began to stabilize after 6 days. Due to the canister back-purge, 

the stabilized diurnal emission rate about 11.5 grams per day which was more than a 50 percent 

reduction compared to baseline. 

A manufacturer of activated carbon performed studies of ethanol fuel blend and carbon 

bed temperature on carbon efficiency.31 Testing was performed with carbon canisters using 

gasoline, E10, and E85 fuel for onboard vapor refueling emissions efficiency. The emissions 

control was similar for each of the test fuels. Testing was also performed to measure gasoline 

working capacity for carbon soaked at temperatures ranging from 25 to 80/C. Over this range 

only a 10 percent decrease in working capacity was observed with increasing temperature. Over 

the 25-40/C range, which is more representative of boat or Small SI equipment use, the effect 

was only 1-2 percent. Based on the results from these studies, carbon canister efficiency would 

be expected to be effective at reducing diurnal emissions over the range of fuels and 

temperatures that may be seen in use. 

5-18 
Feasibility of Evaporative Emission Control 

5.1.5 Sealed System with Pressure Relief 

Evaporative emissions are formed when the fuel heats up, evaporates, and passes through 

a vent into the atmosphere. By closing that vent, evaporative emissions are prevented from 

escaping. However, as vapor is generated, pressure builds up in fuel tank. Once the fuel cools 

back down, the pressure subsides. One way to control these emissions is to seal the fuel system. 

However, depending on the fuel tank design, a pressure relief valve may be necessary which 

would limit the control. 

5.1.5.1 Pressure Relief Valve 

For most marine applications, U.S. Coast Guard safety regulations require that fuel tanks 

be able to withstand at least 3 psi and must be able to pass a pressure impulse test which cycles 

the tank from 0 to 3 psi 25,000 times (33 CFR part 183).2 The Coast Guard also requires that 

these fuel tanks must be vented such that the pressure in the tank in-use never exceeds 80 percent 

of the pressure that the tank is designed to withstand without leaking. The American Boat and 

Yacht Council makes the additional recommendation that the vent line should have a minimum 

inner diameter of 7/16 inch.32 However, these recommended practices also note that “there may 

be EPA or state regulations that limit the discharge of hydrocarbon emissions into the 

atmosphere from gasoline fuel systems. The latest version of these regulations should be 

consulted.” 

To prevent pressure from building too high in marine tanks, we first considered a 2 psi 

pressure relief valve. This is a typical automotive rating and is below the Coast Guard 

requirements. With this valve, vapors would be retained in the tank until 2 psi of pressure is 

built up in the tank due to heating of the fuel. Once the tank pressure reached 2 psi, just enough 

of the vapor would be vented to the atmosphere to maintain 2 psi of pressure. As the fuel cooled, 

the pressure would decrease. In our August 14, 2002 proposal (67 FR 53050) we considered 

standards based on a 1 psi valve which would only achieve a modest reduction over the diurnal 

test procedure. However this reduction would be significantly greater in use because the test 

procedure is designed to represent a hotter than average day. On a more mild day, there would 

be less pressure buildup in the tank and the valve may not even need to open. With the use of a 

sealed system, a low pressure vacuum relief valve would also be necessary so that air could be 

drawn into the tank to replace fuel drawn from the tank when the engine is running. 

Manufacturers of larger plastic fuel tanks have expressed concern that their tanks are not 

designed to operate under pressure. For instance, although they will not leak at 3 psi, 

rotationally molded fuel tanks with large flat surfaces could begin deforming at pressures as low 

as 0.5 psi. At 2.0 psi, the deformation would be greater. This deformation would affect how the 

tank is mounted in the boat. Also, fuel tank manufacturers commented that some of the fittings 

2 These regulations only apply to boats with installed fuel tanks and exclude outboard boats. 

However, ABYC recommended practice effectively extends many of these requirements to outboard 

boats as well. 

5-19 
Final Regulatory Impact Analysis 

or valves used today may not work properly under 2 psi of pressure. Finally, they commented 

that backup pressure-relief valves would be necessary for safety. For smaller fuel tanks, such as 

used in personal watercraft, portable fuel tanks, and Small SI equipment, pressure is less of an 

issue because of the smaller internal surface area of these fuel tanks. In addition, the 

construction of these fuel systems are generally vertically integrated which allows for more 

precise control of design parameters. For instance, personal watercraft manufacturers are 

already sealing their fuel systems to prevent fuel from spilling into the water. These systems 

generally have pressure relief valves ranging from 0.5 to 4.0 psi. In addition, portable fuel tanks 

are designed to be sealed without any pressure relief. 

We looked at two types of pressure relief strategies: pressure relief valves and limited 

flow orifices. Because the Coast Guard requires that fuel systems not exceed 80 percent of their 

design capacity of 3 psi, we only looked at pressure relief strategies that would keep the pressure 

below 2.4 psi under worst case conditions. 

For the pressure relief valve testing, we looked at several pressures ranging from 0.5 to 

2.25 psi. The 2.25 psi valve was an off-the-shelf automotive fuel cap with a nominal 2 psi 

pressure relief valve and 0.5 psi vacuum relief valve. For the other pressure settings, we used 

another automotive cap modified to allow adjustments to the spring tension in the pressure relief 

valve. We performed these tests on the 17 gallon aluminum fuel tank to remove the variable of 

permeation. Emissions were vented through a hose to prevent diffusion losses from affecting the 

measurements. We operated over two temperature profiles. The first set of tests were performed 

in a variable temperature SHED with a 72-96°F air temperature profile. This temperature profile 

was based on the existing automotive cycle which is intended to represent a typical summer day 

on which a high ozone event may occur. The second set of tests were performed using a heating 

blanket to create a 78-90°F fuel temperature profile. This testing was intended to represent a 

fuel tank in a boat, where the tank may be inherently insulated, during the same ambient 

temperature profile. This inherent insulation creates a time lag on the heating and cooling of the 

fuel and reduces the amplitude of the temperature profile by half. 

As shown in Figure 5.1-2, there was a fairly linear relationship between the pressure 

setting of the valve and the emissions measured over the variable-temperature test procedure. In 

addition, the slopes of the lines are similar for both test temperature scenarios. This suggests that 

over a smaller temperature profile, a greater percent reduction in HC can be achieved at a given 

pressure setting. This is reasonable because, in each case, a constant amount of vapor is 

captured. In other words, regardless of the temperature profile, the same amount of vapor must 

be generated to create a given pressure. For instance, with a 1 psi valve, about 0.4 grams/gallon 

of HC are captured over each temperature profile. However, this represents a 50 percent 

reduction over a 78-90°F temperature profile while only about a 25 percent reduction over the 

72-96°F temperature profile. 

5-20 
Feasibility of Evaporative Emission Control 

Figure 5.1-2: Effect of Pressure Cap on Diurnal Emissions 

HC [g/gal/day] 

1.6 

1.4 

1.2 

1 

0.8 

0.6 

0.4 

0.2 

0 

y = -0.42x + 1.5 

R2

 = 0.92 

y = -0.47x + 0.81 

R2

 = 0.96 

0.0 0.5 1.0 1.5 2.0 2.5 

pressure relief setting [psi] 

72-96F 

78-90F 

Portable marine fuel tanks are generally equipped with a valve that allows the tank to be 

sealed when not in use. The valve must be opened during engine operation or the draw of fuel 

from the fuel tank can create a vacuum in the fuel tank. If the vacuum becomes too great, the 

engine will not be able to draw sufficient fuel from the tank and therefore stall. During storage, 

the valve may be closed to prevent fuel vapors from escaping. These fuel tanks are designed to 

withstand pressurization much greater than would be experienced when a fuel tank is heated by 

ambient temperature changes. However, this vapor control strategy relies heavily on user 

behavior. According to one survey, the majority of boat owners store their portable marine fuel 

tanks with fuel in them, and many do not close the vent during storage.33 Therefore, significant 

emission reductions may be achieved with a sealed fuel tank with an automatic vacuum relief 

valve. This is discussed further in section 5.1.5.3 below. 

The California Air Resources Board tested a lawnmower in a SHED for diurnal 

emissions in a baseline configuration, a sealed system, and with various pressure relief settings.34 

Because the whole lawnmower was tested, permeation (and potentially leakages) were measured 

as well as diurnal venting emissions. The testing was performed over a 65-105°F temperature 

cycle with the fuel tank filled to 50 percent with 7 RVP fuel. For the system as a whole, they 

measured a 76 percent reduction in emissions when the tank was fully sealed compared to the 

open vent configuration. This suggests that diurnal venting made up about 76 percent of the 

evaporative emissions measured. Testing using 2, 3, and 4 psi pressure relief valves showed 

reductions of 43 percent, 43 percent, and 63 percent respectively. They also collected pressure 

data over various diurnal temperature cycles on a lawnmower fuel tank. Over the 65-105°F 

cycle, the measured a pressure increase of about 2.5 psi. Even under an extreme cycle of 68-

121°F, the measured increase in tank pressure was about 3.6 psi. 

5-21 
Final Regulatory Impact Analysis 

5.1.5.2 Limited Flow Orifice 

Another strategy for maintaining a design pressure is to use a limited flow orifice on the 

vent. In our testing, we are looked at three orifice sizes: 25, 75, and 1,000 microns in diameter. 

Again, we performed tests over a 72-96°F diurnal using a 17 gallon aluminum tank. To get these 

exact orifice sizes, we ordered from a company that specializes in boring holes with a laser 

device. These orifices were relatively inexpensive. It should be noted that a smaller tank would 

need a smaller orifice and a larger tank could use a larger orifice to build up the same pressure in 

the tank. The test results are presented in Table 5.1-15. For all of the tests with the limited flow 

orifices, no vent hose was attached. 

Table 5.1-15: Diurnal Evaporative Emissions with Limited Flow Orifices 

Orifice Diameter (microns) Peak Pressure [psi] Evaporative HC [g/gallon/day] 

baseline (open vent with hose) 0.0 1.40 

1000 0.0 1.47 

75 1.6 1.16 

25 3.1 0.24 

By limiting the flow of the vapor from the tank, emissions were reduced with some 

pressure build up in the tank. However, because the vapor is flowing from the tank even at low 

pressure, this strategy is less effective for reducing diurnal emissions than a pressure relief valve. 

Generally, a higher peak pressure is necessary with the LFO for a given emission reduction. In 

addition, the limited flow orifice would have to be sized for worst case conditions to prevent the 

tank from reaching too high of a pressure. A LFO sized for worst case conditions would be less 

effective under typical conditions because the vapor flow out of the tank could be too low for the 

LFO to create a restriction. In comparison, a pressure relief valve would achieve higher percent 

reductions under typical conditions than for worst case conditions because the valve would open 

less often. 

5.1.5.3 Vacuum Relief Valve 

For some fuel tanks, pressure relief is not necessary. An example of this is portable 

marine fuel tanks which are currently equipped with a manual sealing valve. This valve can be 

sealed by the operator during storage to prevent vapor from escaping. Although pressure will 

build up during diurnal heating, the fuel tanks are designed to withstand this pressure. However, 

the valve must be opened by the operator during engine operation so that a vacuum does not 

form in the fuel tank as fuel is drawn to the engine. If this vacuum were to become too high, it 

could cause the engine to stall by restricting fuel to the engine. 

The existing design requires that the operator close the valve whenever the engine is not 

running for diurnal emissions to be controlled. If an automatic vacuum relief valve were used, 

5-22 
Feasibility of Evaporative Emission Control 

then the operator would not need to operate the sealing mechanism. It would always control 

diurnal emissions. At the same time, the vacuum relief valve would allow air to be drawn into 

the fuel tank when the engine is operating to prevent a significant vacuum from being formed. 

One manufacturer’s approach to this automatic valve design is to use a diaphragm valve 

such as those used in automotive fuel systems.35 This inexpensive design would be able to seal 

the tank under pressure, yet open at very low vacuums. This design (or other vacuum relief 

valve designs) could be used in any nonroad application where the fuel system is able to 

withstand pressure. 

5.1.6 Selective Permeability Membrane 

Another approach we investigated was fitting a molecular membrane in the vent line. 

The theory was that the membrane would allow oxygen and nitrogen to pass through, but block 

most longer-chain hydrocarbon molecules. We used a membrane fabricated using Teflon AF® 

which is an amorphous fluoropolymer. Because oxygen and nitrogen (and some smaller 

hydrocarbons) can pass through the membrane, hydrocarbons can be trapped in the fuel tank. 

However, the process for molecules passing through the membrane is slow, so it is important to 

size the membrane properly to prevent pressure build-up. This membrane could be placed in the 

vent line or directly in an opening in the top of the fuel tank. 

Similar membranes are already used for several applications. One manufacturer provides 

membranes for a variety of uses such as oxygen or nitrogen enrichment of air or for separation of 

hydrocarbons from air.36 One of these uses is to act as a vapor processor to prevent hydrocarbon 

vapor from escaping from retail gasoline stations in California.37 Another membrane used for 

similar applications allows hydrocarbons to permeate but blocks smaller gases. This membrane 

is used in hydrocarbon recovery applications.38 In the above noted applications, the membranes 

are typically used with a pump to provide a pressure drop across the membrane which causes 

permeation through the membrane. Typically, adequate mixing is needed to maintain an 

efficient diffusion rate. 

We tested an amorphous fluoropolymer membrane with a surface area of about 40 cm2

 in 

the vent line of both a 30 and a 17 gallon aluminum fuel tank over three temperature cycles. The 

membrane was applied to a wire mesh in a cylindrical shape with the an outside diameter not 

much larger than the vent hose. Hydrocarbon emissions and fuel tank pressure were measured. 

Over these tests we consistently saw a pressure build up, even over a 24 hour test. To investigate 

the impacts of surface area, we increased the surface area by using 3 filters in parallel (single 

vent line to assembly). Our test results suggest that the pressures associated with this technology 

are comparable with the pressure relief valves needed to achieve the same reductions. However, 

this technology may have the potential for meeting our standards if used in conjunction with a 

pump to provide a pressure differential across the filter without allowing pressure (and mixing) 

to build up in the fuel tank. Our test results are presented in Table 5.1-16. 

5-23 
Final Regulatory Impact Analysis 

Table 5.1-16: Diurnal Venting Emissions with Selective Permeable Membranes 

Tank Size 

[gallons] Venting 

72-96°F 

g/gal/day psi 

78-90°F 

g/gal/day psi 

81.6-86.4°F 

g/gal/day psi 

30 open 

1 filter 

3 filters 

1.50 

0.24 

0.39 

0 

2.9 

2.2 

0.85 

0.14 

– 

0 

1.5 

– 

0.47 

0.19 

– 

0 

0.6 

– 

17 open 

3 filters 

1.40 

0.45 

0 

2.1 

– 

0.30 

– 

1.2 

– 

– 

– 

– 

5.1.7 Volume Compensating Air Bag 

Another concept for minimizing pressure in a sealed fuel tank is through the use of a 

volume compensating air bag.39 The purpose of the bag is to fill up the vapor space in the fuel 

tank above the fuel itself. By minimizing the vapor space, less air is available to mix with the 

heated fuel and less fuel evaporates. As vapor is generated in the small vapor space, air is forced 

out of the air bag, which is vented to atmosphere. Because the bag collapses as vapor is 

generated, the volume of the vapor space grows and no pressure is generated.3 Once the fuel 

tank cools as ambient temperature goes down, the resulting vacuum in the fuel tank will open the 

bag back up. 

We tested a 6 gallon portable plastic fuel tank with a 1.5 gallon volume compensating 

bag made out of Tedlar. Tedlar is a light, flexible, clear plastic which we use in our labs for 

collecting exhaust emissions samples. In our testing, the pressure relief valve never opened 

because the volume compensating bag was able to hold the vapor pressure below 0.8 psi for each 

of the three days. This testing supports the theory that a volume compensating bag can be used 

to minimize pressure in a fuel tank, which in turn, reduces emissions when used in conjunction 

with a pressure relief valve. 

We did see an emission rate of about 0.4 g/gal/day over the 3 day test. The emission rate 

was fairly constant, even when the ambient temperature was cooling during the test. This 

suggests that the emissions measured were likely permeation through the tank. Other materials 

may be more appropriate than Tedlar for the construction of these bags. The bags would have to 

hold up in a fuel tank for years and resist permeation while at the same time be light and flexible. 

One such material that may be appropriate would be a fluorosilicon fiber. 

3

 The Ideal Gas Law states that pressure and volume are inversely related. By increasing the volume of the 

vapor space, the pressure can be held constant. 

5-24 
Feasibility of Evaporative Emission Control 

5.1.8 Bladder Fuel Tank 

Probably the most effective technology for reducing evaporative emissions from fuel 

tanks is through the use of a collapsible fuel bladder. In this concept, a non-permeable bladder 

would be installed in the fuel tank to hold the fuel. As fuel is drawn from the bladder, the 

vacuum created collapses the bladder. Therefore, there is no vapor space and no pressure build 

up. Because the bladder would be sealed, there would be no vapors vented to the atmosphere. 

In addition, because there is no vapor space, vapor is not displaced during refueling events. We 

have received comments that bladder tanks would be cost prohibitive because its use would 

increase tank costs by 30 to 100 percent depending on tank size. However, bladder fuel tanks 

have positive safety implications as well and are already sold by at least one manufacturer to 

meet market demand in niche applications. Information on this system is available in the 

docket.40 

We tested a marine bladder fuel tank in our lab for both diurnal and permeation 

emissions. Over the diurnal test procedure we saw an emission rate of 0.2 g/gal/day. Because 

the system was sealed, this measured emission rate was likely due to permeation through the 

bladder and not due to diurnal losses. We later tested the bladder fuel tank for permeation 

emissions at 29°C and measured a permeation rate of 0.46 g/gal/day. The bladder used in our 

testing was constructed out of polyurethane. The manufacturer of this bladder tank is now 

working with a lower permeability material known as THV. THV is a fluoropolymer that can be 

used to achieve more than a 95 percent reduction in permeation from current bladder fuel tanks 

made out of polyurethane.41 In addition, THV is resistant to ethanol. Permeation rates for these 

materials are presented in Appendix 5D. 

5.1.9 Floating Fuel and Vapor Separator 

Another concept used in some stationary engine applications is a floating fuel and vapor 

separator. Generally small, impermeable plastic balls are floated in the fuel tank. The purpose 

of these balls is to provide a barrier between the surface of the fuel and the vapor space. 

However, this strategy does not appear to be viable for fuel tanks used in mobile sources. 

Because of the motion of Small SI equipment and Marine SI vessels, the fuel sloshes and the 

barrier would be continuously broken. Even small movements in the fuel could cause the balls 

to rotate and transfer fuel to the vapor space. In addition, the unique geometry of many fuel 

tanks could case the balls to collect in one area of the tank. However, we do not preclude the 

possibility that some form of this approach could be made to work effectively in some mobile 

source applications. 

5.1.10 Liquid Vapor Trap 

One company has developed a Figure 5.1-3: Liquid Vapor Trap 

liquid vapor trap that it refers to as a 

fuel vapor containment system (VCS).42 A B 

The VCS behaves similar to a liquid VCS 

trap used in sink drains in that trapped 

fuel tank vent 

5-25 
Final Regulatory Impact Analysis 

liquid creates a barrier to gases. This trap would be placed in the vent line to limit fuel vapor 

emitted from the fuel tank. Figure 5.1-3 presents an illustration of the basic concept. 

When the temperature in the fuel tank increases, the vapor would expand in the fuel tank. 

The fuel vapor would enter chamber A and force more of the liquid into chamber B. This would 

provide room for the vapor to expand without allowing vapor to escape through the vent. As the 

fuel tank cools, the vapor would condense. This would cause the level of the liquid in chamber A 

to rise while the level of the liquid in chamber B would drop. Some pressurization may occur in 

the fuel tank with this system, but it would be much less than for a sealed fuel tank due to the 

expansion chamber. Any pressure or vacuum in the fuel system would be a function of the VCS 

design and would be expected to be less than 0.5 psi. In addition, a pressure relief valve could 

be added to the system to protect against any high pressure excursions. 

In the initial testing of the VCS, the manufacturer has used water as the liquid barrier. 

However, they stated that ethylene-glycol or even oil could be used which would be more stable 

liquids and would resist freezing. Diurnal testing was performed on a 25 gallon fuel tank 

equipped with a roughly 3 gallon VCS unit.43 Testing was performed in a mini-SHED over the 

EPA 72-96/C diurnal cycle for two days. The tank was filled to 50 percent capacity with 9 RVP 

certification gasoline. The total weight loss was 1.1 grams on the first day and 2.6 grams on the 

second day. Using the higher of the two days, we get a diurnal emission rate of about 0.1 

g/gal/day. The peak pressure during this testing was approximately 0.5 psi. 

5.2 Running Loss Emissions 

Running loss emissions are similar to diurnal emissions except that the fuel temperature 

rise is due to heat from the engine or other heat producing components, such as hydraulic 

systems, when the engine is running. This section summarizes the data and rationale supporting 

the running loss emission standard for Small SI equipment presented in the Executive Summary. 

5.2.1 Baseline Emissions 

To investigate running loss emissions, we instrumented seven riding lawnmowers, three 

walk-behind lawnmowers, two generators, and one pressure washer to measure the fuel 

temperature during typical operation. Many of the temperature measurements were made by a 

contractor.44 Of the riding mowers, two had fuel tanks in front near the engine, three had fuel 

tanks in rear away from engine (but near the hydraulic system), and two were “zero-turn” 

mowers that had pairs of side saddle tanks that were relatively close to the rear mounted engine. 

All of the riding mowers had plastic fuel tanks. One of the walk-behind mowers had a metal 

tank directly mounted to the block while the others had plastic tanks near the top/side of the 

engine. Both generators had plastic tanks mounted above the engine while the pressure washer 

had a metal tank mounted above the engine. All of the equipment vented through the fuel caps. 

The pressure washer had a metal fuel tank mounted above the engine. The equipment was 

operated in the field until the fuel temperature stabilized. For lawnmowers, the fuel temperature 

stabilized within 20 to 30 minutes while the larger equipment took up to an hour. 

5-26 
Feasibility of Evaporative Emission Control 

By measuring the increase in fuel temperature during operation, we were able to make a 

simple determination of the running loss emissions vented from the fuel tank. Other potential 

running loss emissions would be from the carburetor, due to permeation increases due to heating 

the fuel, or vibration-induced leaks in the fuel system. However, we believed that the majority 

of the running loss emissions would be due to breathing losses associated with heating the fuel. 

Table 5.2-1 presents the results of the temperature testing. 

We contracted with an independent testing laboratory to test fuel tanks from most of the 

above pieces of equipment over the measured fuel temperature profiles.45 For three of the tests 

on larger fuel tanks, we found that the measured emissions were inconsistent with theoretical 

predictions. An investigation of the test data suggested that the test had been ended too soon to 

see the full effect of the heat build. Repeat tests were performed with a longer sample time.46 

From this data we get the running loss emissions due to the breathing losses associated with the 

heating of the fuel tank. New tanks were purchased for this testing that had not been previously 

exposed to fuel so permeation emissions would not be included in the emission measurements. 

Table 5.2-1 also presents the test results for the above equipment. 

Table 5.2-1: Fuel Temperature Measurements During Operation of 

Small SI Equipment and Hydrocarbons Measured Over This Temperature Profile 

Equipment Type Fuel Capacity 

[gallons] 

Min. Temp 

°C 

Max. Temp 

°C 

HC [g/hr] 

Riding mower 

front tank near engine 

1.7 

1.1 

19.5 

15.7 

30.3 

28.4 

1.4 

1.0 

Riding mower 

rear tank away from engine 

6.5 

3.0 

2.5 

24.3 

26.6 

27.0 

33.2 

28.4 

35.0 

7.8 

0.7 

3.2 

Zero-turn riding mower 

2 saddle tanks near engine 

6.5 x 2 

1.4 x 2 

20.5 

21.9 

23.9 

29.7 

3.4 

2.5 

Walk-behind mower (plastic) 0.34 

0.25 

23.3 

28.7 

33.0 

46.7 

0.3 

1.2 

Walk-behind mower (metal) 0.22 28.7 59.7 8.1 

Generator set 8.5 

7.0 

20.6 

25.8 

25.8 

50.0 

1.8 

69.3 

Pressure washer 1.8 19.0 50.6 20.3 

The California Air Resources Board performed running loss tests on several pieces of 

Small SI equipment.47 This equipment included four lawnmowers (2 new and 2 old), one string 

trimmer, two generators, two ATVs, and two forklifts. To measure running loss emissions, the 

equipment were operated on California certification fuel in a SHED and the exhaust was routed 

5-27 
Final Regulatory Impact Analysis 

outside the SHED. Running loss emissions were determined by measuring the HC concentration 

in the SHED. Therefore the measurements included all evaporative emissions during operation 

including those from fuel heating, permeation, carburetor losses, and, for the two older 

lawnmowers, liquid fuel leaks. Although the ATVs and forklifts are not considered to be small 

offroad engines, these data can be used as surrogates for equipment that were not tested. Table 

5.2-2 presents this data. 

Table 5.2-2: Results from ARB Running Loss Tests 

Equipment Type Model Year* Running Loss [g/hr] 

lawnmower 2000 

2001 

1994 

1989 

0.8 

2.6 

27.0 

12.1 

string trimmer 1999 0.6 

generator 1995 

2001 

19.5 

1.8 

ATV 2001 

2001 

21.4 

1.3 

forklift 1995 

1987 

1.8 

7.4 

* the 2000 and 2001 equipment were new at the time of testing 

5.2.2 Control Technology 

Running loss emissions can be controlled by sealing the fuel cap and routing vapors from 

the fuel tank to the engine intake. In doing so, vapor generated heat from the engine will be 

burned by the engine. It may be necessary to use a valve or limited flow orifice in the purge line 

to prevent fuel from entering the line in the case of the equipment turning over and to limit the 

vapor to the engine during operation. Depending on the configuration of the fuel system and 

purge line, a one way valve in the fuel cap may be desired to prevent a vacuum in the fuel tank 

during engine operation. We anticipate that a system like this would eliminate running loss 

venting emissions. However, higher temperatures during operation would increase permeation 

somewhat. In addition, the additional length of vapor line would increase permeation. 

Considering these effects, we still believe that the system described here would result in more 

than a 90 percent reduction in running loss emissions from Small SI equipment. 

A secondary benefit of running loss control for Small SI equipment has to do with 

diffusion emissions. As discussed above, venting a fuel tank through a hose (rather than through 

an open orifice) greatly reduces diffusion. In the system discussed above, all venting losses 

would occur through the vapor hose to the engine intake rather than through open vents in the 

5-28 
Feasibility of Evaporative Emission Control 

fuel cap. Therefore, the diffusion effect should be largely eliminated. 

Another approach to reducing running loss emissions would be to insulate the fuel tank 

or move it further from heat sources such as the engine or hydraulic system. With this approach, 

the fuel cap vent would likely still be used, but diffusion could be controlled using a tortuous 

vent path in the cap as described above. 

For marine fuel tanks we are not considering running loss emissions. For portable fuel 

tanks and installed fuel tanks on larger vessels, we would not expect there to be significant 

heating of the fuel tanks during engine operation due to the distance from the engine and the 

cooling effect of operating the vessel in water. For personal watercraft, the fuel tanks have a 

sealed system with pressure relief that should help contain running loss emissions. For other 

installed fuel tanks, we would expect the diurnal emission control system to capture about half of 

any running losses as well. 

5.3 Fuel Tank Permeation 

The polymeric material (plastic) of which many gasoline fuel tanks manufactured 

generally has a chemical composition much like that of gasoline. As a result, constant exposure 

of gasoline to these surfaces allows the material to continually absorb fuel. Permeation is driven 

by the difference in the chemical potentials of gasoline or gasoline vapor on either side of the 

material. The outer surfaces of these materials are exposed to ambient air, so the gasoline 

molecules permeate through these fuel-system components and are emitted directly into the air. 

Permeation emissions continue at a nearly constant rate, regardless of how much the vehicle or 

equipment is used. Because of these effects, permeation-related emissions can therefore add up 

to a large fraction of the total emissions from nonroad equipment. 

This section summarizes the data and rationale supporting the permeation emission 

standard for Small SI and Marine SI fuel tanks presented in the Executive Summary. 

5.3.1 Baseline Fuel Tank Technology and Emissions 

Fuel tanks may be constructed in several ways. Portable marine fuel tanks and some 

small, higher production-volume, installed marine fuel tanks are generally blow-molded using 

high-density polyethylene (HDPE). Larger, installed marine fuel tanks are generally either 

rotationally-molded using cross-link polyethylene (XLPE) or are constructed out of welded 

aluminum. Some boat builders even construct the fuel tanks out of fiberglass as part of the 

vessel construction. Fuel tanks on Small SI equipment may be injection molded, blow molded or 

rotationally molded. Blow-molded and injection-molded tanks are primarily made of HDPE, but 

nylon is used as well in some applications. Rotationally molded fuel tanks are generally made 

out of XLPE. 

Blow molding is widely used for the manufacture of Small SI, portable marine, and PWC 

fuel tanks. Typically, blow molding is performed by creating a hollow tube, known as a parison, 

by pushing high-density polyethylene (HDPE) through an extruder with a screw. The parison is 

5-29 
Final Regulatory Impact Analysis 

then pinched in a mold and inflated with an inert gas. In automotive applications, nonpermeable plastic fuel tanks are produced by blow molding a layer of ethylene vinyl alcohol 

(EVOH) or nylon between two layers of polyethylene. This process is called coextrusion and 

requires at least five layers: the barrier layer, adhesive layers on either side of the barrier layer, 

and HDPE as the outside layers which make up most of the thickness of the fuel tank walls. 

However, multi-layer construction requires additional extruder screws which significantly 

increases the cost of the blow molding machine. 

Injection molding can be used with lower production volumes than blow molding due to 

lower tooling costs. In this method, a low viscosity polymer is forced into a thin mold to create 

each side of the fuel tank. The two sides are then welded together. In typical fuel tank 

construction, the sides are welded together by using a hot plate for localized melting and then 

pressing the sides together. The sides may also be connected using vibration or sonic welding. 

Rotational molding has two advantages over blow molding, which is widely used for 

forming automotive parts. First, the tooling cost is an order of magnitude lower than for blowmolding. Therefore, for small production volumes such as seen for marine applications, 

rotational molding is more cost-effective. Manufacturers of rotationally molded plastic fuel 

tanks have commented that they could not produce their tanks with competitive pricing in any 

other way. The second advantage of rotational molding is that larger parts can generally be 

molded on rotational molding machines than on blow-molding machines. Plastic marine fuel 

tanks can exceed 120 gallons. 

Installed plastic marine fuel tanks are often produced in many shapes and sizes to fit the 

needs of specific boat designs. These fuel tanks tanks are generally rotationally-molded out of 

cross-link polyethylene. Cross-link polyethylene, which has a permeation rate comparable to 

HDPE, is used in larger marine applications because of its ability to pass the U.S. Coast Guard 

flame resistance requirements (33 CFR 183.590). Rotational-molding is also used in some Small 

SI applications where there are low production volumes of unique fuel tanks. XLPE is used in 

these fuel tanks as well because the fuel tank is often exposed and must be able to withstand 

impacts such as flying debris. 

5.3.1.1 Baseline permeation test data 

5.3.1.1.1 Marine fuel tanks 

To determine the baseline permeation emissions from marine fuel tanks, we have 

collected permeation data on several plastic fuel tanks. Because gasoline does not permeate 

through aluminum, we did not perform permeation testing on aluminum fuel tanks. 

We tested ten plastic fuel tanks that were either intended for marine use or are of similar 

construction. This permeation testing was performed at 29°C with gasoline. Prior to testing, the 

fuel tanks were stored with gasoline in them for about 20 weeks to ensure stable permeation 

rates. Table 5.3-1 presents the measured permeation rates for these fuel tanks in grams per 

gallon of fuel tank capacity. Where the internal surface area was either easily determined or 

5-30 
Feasibility of Evaporative Emission Control 

supplied by the manufacturer, we also calculated the permeation rate in terms of grams per 

square meter of inside surface area. The 31 gallon tank showed much lower permeation than the 

other fuel tanks. This was likely due to the thickness of the walls in this tank. Even after 

stabilization, permeation is a function of material thickness. According to Fick’s Law, if the 

wall thickness of a fuel tank were double, the permeation rate would be halved.48 

Table 5.3-1: Permeation Rates for Plastic Marine Fuel Tanks Tested by EPA at 29°C 

Tank Capacity 

[gallons] 

Permeation 

[g/gal/day] [g/m2

/day] 

Construction Application 

3.3 

6.0 

6.0 

6.0 

6.6 

6.6 

6.0 

23 

31 

0.96 

0.61 

1.18 

0.75 

0.83 

0.77 

0.60 

0.64 

0.44 

12.7 

6.8 

13.1 

8.4 

9.1 

8.4 

8.3 

8.1 

5.5 

HDPE 

HDPE 

HDPE 

HDPE 

HDPE 

HDPE 

cross-link 

cross-link 

cross-link 

portable marine 

portable marine 

portable marine 

portable marine 

portable marine 

portable marine 

marine test tank 

installed marine 

installed marine 

The Coast Guard tested three rotationally-molded, cross-link polyethylene marine fuel 

tanks at 40°C (104°F) for 30 days.49 The results are presented in Table 5.3-2. Because 

permeation emissions are a function of surface area and wall thickness, there was some variation 

in the permeation rates from the three tanks on a g/gal/day basis. These results are not directly 

comparable to the EPA testing because of the difference in test temperature. However, we can 

adjust the permeation rates for temperature using Arrhenius’ relationship50 combined with 

empirical data collected on permeation rates for materials used in fuel tank constructions 

(described below). These adjusted permeation rates are shown in Table 5.3-2 and are consistent 

with the EPA test data. 

Table 5.3-2: Permeation Rates for Cross-Link Marine Fuel Tanks at 40°C 

Tank Capacity 

[gallons] 

Measured Permeation 

Loss [g/gal/day] 

Average Wall 

Thickness [mm] 

Adjusted to 29°C 

[g/gal/day] 

12 1.48 5.3 0.71 

18 1.39 5.6 0.67 

18 1.12 6.9 0.54 

5.3.1.1.2 Small SI equipment fuel tanks 

The California Air Resources Board (ARB) investigated permeation rates lawn & garden 

equipment fuel tanks. The ARB data is compiled in several data reports on their web site and are 

5-31 
Final Regulatory Impact Analysis 

included in our docket.51,52,53,54,55 Table 5.3-3 presents a summary of this data which was 

collected using the ARB Test Method 513.56 Where multiple tests were run on a given tank or 

tank type, the average results are presented. Although the temperature in the ARB testing is 

cycled from 18 - 41°C rather than held at a constant temperature, the average temperature is 

29/C which is similar to the EPA testing. Therefore, the permeation results would likely be 

similar if the data were collected at the average temperature of 29°C used in the EPA testing. 

Variation in permeation rates on a gram per square meter basis is likely due to differences in the 

wall thicknesses. Note that surface area measurements were not available for all of the fuel 

tanks. Smaller fuel tanks would be expected to have higher emissions on a gram per gallon basis 

due to the increased surface area to volume ratio. However, lower permeation rates were 

observed for the fuel tanks less than 1 quart, potentially due to relatively thicker walls or due to a 

difference in material used for these applications. 

5-32 
--

--

--

--

--

--

--

--

--

Feasibility of Evaporative Emission Control 

Table 5.3-3: Permeation Rates for Plastic Lawn and 

Garden Fuel Tanks Tested by ARB Over a 18-41°C Diurnal 

Tank Capacity Permeation Loss Permeation Loss 

[gallons] [g/gal/day] [g/m2

/day] 

0.06 0.20 5.39 

0.08 0.26 6.67 

0.09 0.12 

0.09 0.19 5.88 

0.10 0.28 

0.12 0.53 9.01 

0.15 0.42 7.32 

0.16 0.29 4.79 

0.25 1.32 11.56 

0.25 0.73 10.65 

0.25 0.67 9.75 

0.25 0.74 10.75 

0.25 0.86 12.54 

0.25 0.68 9.91 

0.25 1.06 9.24 

0.25 1.24 10.84 

0.25 0.99 8.68 

0.25 0.67 9.80 

0.25 0.66 9.65 

0.25 0.62 9.07 

0.25 1.39 12.17 

0.25 1.26 11.03 

0.29 1.27 15.00 

0.38 0.27 

0.38 1.30 10.66 

0.38 0.92 9.18 

0.38 0.08 

0.50 1.39 12.69 

0.50 1.04 8.53 

0.55 1.24 

0.74 1.82 

1.4 1.72 7.81 

1.7 1.14 

1.8 1.47 6.19 

3.9 3.28 4.84 

5.0 3.20 

5.0 2.75 

5.0 3.82 8.80 

7.5 2.07 2.86 

5-33 
Final Regulatory Impact Analysis 

Some handheld equipment, primarily chainsaws, use structurally-integrated fuel tanks 

where the tank is molded as part of the body of the equipment. In these applications the frames 

(and tanks) are typically molded out of nylon for strength. We tested structurally-integrated fuel 

tanks from four handheld equipment manufacturers at 29/C on both gasoline and s 10 percent 

ethanol blend. The test results suggest that these fuel tanks are capable of meeting the standards 

using their current materials. In the cases where the permeation rates were higher than the 

standards, it was observed that the fuel cap seals had large exposed surface areas on the O-rings, 

which were not made of low permeation materials. Emissions could likely be reduced 

significantly from these tanks with improved seal designs. Table 5.3-4a presents the results of 

this testing. Note that permeation emissions are 20 to 70 percent higher on E10 than on gasoline 

for these fuel tanks. 

Table 5.3-4a: Permeation Rates for Handheld Fuel Tanks Tested by EPA at 29°C 

Tank ID Application Material Test Fuel Permeation Loss 

[g/m2

/day] 

R1 

R2 

R3 

clearing saw 

(0.24 gallons) 

nylon 6 gasoline 

E10 

E10 

0.34 

0.42 

0.48 

B1 

B2 

B3 

B4 

hedge clipper 

(0.05 gallons) 

nylon 6, 33% glass gasoline 

E10 

E10 

E10 

0.62 

1.01 

1.12 

0.93 

W1 

W2 

W3 

chainsaw 

(0.06 gallons) 

nylon 6, 30% glass gasoline 

E10 

E10 

1.45 

2.18 

2.46 

G1 

G2 

G3 

chainsaw 

(0.06 gallons) 

nylon 6, 30% glass gasoline 

E10 

E10 

1.30 

1.41 

2.14 

The handheld industry also tested a number of fuel tanks for their products.57 In this 

testing, they investigated the effect of fuel type and gasket material on the permeation results. 

These test results suggested that permeation can be reduced significantly by using a low 

permeation material, such as FKM, for the seal on the fuel cap. In addition, data on aged tanks 

suggested that NBR o-rings may deteriorate in-use such that the permeation rate (or vapor leak 

rate) through the seal increases greatly. This test data is presented in Table 5.3-4b. 

5-34 
Feasibility of Evaporative Emission Control 

Table 5.3-4b: Permeation Rates for Handheld Fuel Tanks Tested by Industry 

Tank 

Capacity 

Tank Material O-ring 

Material 

Test 

Temp. 

Test Fuel Permeation Loss 

[g/m2

/day] 

350cc nylon 6, 30% glass NBR 

NBR 

Aged NBR* 

New NBR* 

28/C CE10 1.00 

0.64 

45.2 

0.92 

260cc nylon 6, 30% glass NBR 28/C CE10 1.31 

0.64 

773cc nylon 6, 30% glass NBR 40/C CE10 

CE10 

gasoline 

3.58 

2.60 

1.10 

400cc nylon 6, 30% glass FKM 40/C CE10 0.40 

1538cc nylon 6, 33% glass NBR 40/C CE10 1.11 

1538cc nylon 6, 30% glass NBR 

FKM 

40/C CE10 1.42 

0.37 

530cc nylon 6, 30% glass NBR 40/C gasoline 1.55 

400cc HDPE NBR (gasket) 40/C gasoline 17.5 

* these units were used in the field prior to testing 

5.3.1.1.3 Portable fuel tanks 

The California Air Resources Board (ARB) investigated permeation rates from portable 

fuel containers. Although this testing was not on Small SI or marine fuel tanks, the fuel tanks 

tested are of similar construction.58,59 The ARB data is compiled in several data reports on their 

web site and is included in our docket. Table 5.3-5 presents a summary of this data which was 

collected using the ARB Test Method 513.60 Due to the increasing surface to volume ratio with 

decreasing fuel tank sizes, data presented in terms of grams per gallon for smaller tanks would be 

expected to be higher for the same grams per surface area permeation rate. Although the 

temperature in the ARB testing is cycled from 18 - 41°C rather than held at a constant 

temperature, the results would likely be similar if the data were collected at the average 

temperature of 29°C which is used in the EPA testing. 

5-35 
Final Regulatory Impact Analysis 

Table 5.3-5: Permeation Rates for HDPE Portable 

Fuel Containers Tested by ARB Over a 18-41°C Diurnal 

Tank Capacity 

[gallons] 

Permeation Loss 

[g/gal/day] 

1.0 

1.0 

1.0 

1.0 

1.0 

1.0 

1.3 

1.3 

1.3 

1.3 

1.3 

1.3 

1.3 

1.3 

2.1 

2.1 

2.1 

2.1 

2.5 

2.5 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

6.6 

1.63 

1.63 

1.51 

0.80 

0.75 

0.75 

0.50 

0.49 

0.51 

0.52 

0.51 

0.51 

1.51 

1.52 

1.88 

1.95 

1.91 

1.78 

1.46 

1.09 

0.89 

0.62 

0.99 

1.39 

1.46 

1.41 

1.47 

1.09 

5.3.1.2 Effect of temperature on permeation rate 

It is well known that the rate of permeation is a function of temperature. For most 

materials, permeability increases by about a factor of 2 for every 10°C increase in temperature.61 

To determine this relationship for nonroad fuel tanks, we performed permeation testing on nine 

HDPE Small SI fuel tanks at both 29°C and 36°C (85°F and 96°F). This sample set included 

both baseline and surface treated fuel tanks. On average (excluding the outlier), the temperature 

effect was equivalent to nearly a factor of 2 increase in permeation per 10°C increase in 

temperature. The one outlier likely resulted from measurement error due to the very low 

permeation levels (0.5 grams lost over 2 weeks). Table 5.3-6 presents the test results. 

5-36 
Data on HDPE samples 

80% increase in permeation per 

10 C increase in temperature 

Feasibility of Evaporative Emission Control 

Table 5.3-6: Effect of Temperature on Permeation from HDPE Small SI Fuel Tanks 

Tank Treatment 29°C [g/m2

/day] 36°C [g/m2/day] Increase per 10°C 

A 

B 

C 

untreated 11.5 

11.4 

11.2 

17.1 

16.6 

17.0 

92% 

86% 

97% 

D 

E 

F 

sulfonated 2.48 

2.73 

2.24 

4.10 

3.98 

3.42 

127% 

85% 

100% 

H 

I 

J 

fluorinated 0.56 

0.62 

0.22 

0.75 

0.68 

0.31 

60% 

17% 

80% 

Published data collected on HDPE samples at four temperatures62,63 suggest that the 

permeation of gasoline through HDPE increases by about 80 percent for every 10°C increase in 

temperature. This relationship is presented in Figure 5.3-1, and the numeric data can be found in 

Appendix 5D. 

Figure 5.3-1: Effect of Temperature on HDPE Permeation 

0 

50 

100 

150 

200 

250 

300 

350 

400 

450 

g mm/m2 day 

0 10 20 30 40 50 60 70 

degrees Celsius 

Another study was performed on the permeation from complete automotive fuel 

systems.64 These fuel systems, which included fuel tanks, hoses, and other components, were 

tested at both 29°C and 40°C on three fuel types (gasoline, ethanol blend, and MTBE blend). 

5-37 
Final Regulatory Impact Analysis 

The effect of temperature on permeation did not appear to be significantly affected by fuel type. 

Table 5.3-7 presents this data for ten automotive fuel systems tested on gasoline. This data 

showed more than a factor of 2 increase in permeation per 10°C increase in temperature. 

Table 5.3-7: Effect of Temperature on Permeation from Automotive Fuel Systems 

Fuel System Fuel Tank 29°C 

[mg/hr] 

40°C 

[mg/hr] 

Increase 

per 10°C 

2001 Toyota Tacoma 

2000 Honda Odyssey 

1999 Toyota Corolla 

1997 Chrysler Town & Country 

1995 Ford Ranger 

1993 Chevrolet Caprice Classic 

1991 Honda Accord LX 

1989 Ford Taurus GL 

1985 Nissan Sentra 

1978 Olds Cutlass Supreme 

Metal 

Plastic (enhanced 

evap) 

Metal 

Plastic (enhanced 

evap) 

HDPE 

Fluorinated HDPE 

Metal 

Metal 

Metal 

Metal 

9 

21 

10 

23 

309 

95 

40 

24 

53 

57 

20 

55 

24 

52 

677 

255 

110 

52 

148 

122 

101% 

136% 

124% 

110% 

102% 

143% 

148% 

100% 

152% 

99% 

5.3.1.3 Units for reporting the permeation rate (g/gal/day vs. g/m2

/day) 

Much of the permeation data presented in this chapter is in units of grams of 

hydrocarbons lost in a day divided by the capacity of the fuel tank (g/gal/day). For diurnal 

emissions, these units are used because the vapor generation is a function of fuel tank volume. 

For permeation emissions, we considered using these units because the capacity of the fuel tank 

is generally readily available; either identified on the fuel tank or readily measured. However, 

although volume is generally used to characterize fuel tank emission rates, permeation is actually 

a function of surface area. Because the surface to volume ratio of a fuel tank changes with 

capacity and geometry of the tank, two similar shaped tanks of different volumes or two different 

shaped tanks of the same volume could have different g/gal/day permeation rates even if they 

were made of the same material and used the same emission control technology. For this reason, 

the final standards are based on units of grams per square meter of inside surface area 

(g/m2

/day). 

This chapter presents permeation data for a large number of Small SI, marine, and other 

fuel tanks. For many of these fuel tanks, we had information on both the volume and inside 

surface area. Figure 5.3-2 presents the relationship between fuel tank volume in gallons and 

inside surface area in square meters. As a fuel tank becomes smaller, its surface to volume ratio 

increases. This relationship can be seen better in the chart to the right which presents only data 

for fuel tanks less than 1 gallon. A hyperbolic curve is fit through the data in Figure 5.3-2 to 

represent this relationship. This is seen better in the right-side chart which presents only smaller 

tank sizes. In addition to fuel tank volume, the surface to volume ratio is affected by geometry 

5-38 
Feasibility of Evaporative Emission Control 

of the fuel tank. A long flat-fuel tank would have a higher surface to volume than a cube or 

spherical design. Larger plastic fuel tanks, used primarily in marine vessels, tend to have 

somewhat high surface to volume ratios for this reason. 

Figure 5.3-2: Relationship Between Tank Volume and Inside Surface Area 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

0 10 20 30 40 

volume [gallons] 

inside surface area [m2] 

0.00 

0.05 

0.10 

0.15 

0.20 

0.0 0.5 1.0 

volume [gallons] 

inside surface area [m2] 

5.3.1.4 Effect of fuel tank fill level on permeation 

Permeation is driven by the chemical potential of the fuel or vapor in contact with the 

plastic. In a fuel tank, the vapor is essentially at equilibrium with the fuel in a fuel tank. 

Therefore, the permeation rate is the same through the surfaces in contact with saturated vapor as 

it is through the surfaces in contact with the liquid fuel. Because the permeation rate of saturated 

vapor and liquid fuel are the same, the fill level of the fuel tank during a permeation test does not 

affect the measured results. 

Figure 5.3-3: Cup Method 

The fact that liquid fuel and saturated fuel vapor result 

in the same permeation rates is supported by published 

literature.65,66,67,68 In two of these studies, permeation was 

measured for material samples using the cup method 

illustrated in Figure 5.3-3. In these tests, no significant 

difference was seen between the permeation rates for material 

samples exposed to liquid fuel or to fuel vapor. To test for 

permeation with fuel vapor, the cup was inverted so that the 

fuel was on the bottom and the sample was taken off the top. 

Table 5.3-8 presents the data from these two reports. In both 

cases, the material being tested was a fluoroelastomer. 

Purge Gas 

to Sampler 

Fuel Sample 

Material Sample 

Purge Gas

to Sampler

Fuel Sample

Material Sample

5-39 
Final Regulatory Impact Analysis 

Table 5.3-8: Permeation Measured in Cup Method with Fuel Versus Vapor Fuel Exposure 

Paper Fuel Temperature Liquid Fuel Exposure Fuel Vapor Exposure 

SAE 2001-01-1999 CE10 40/C 30.5 g/m2

/day 29.5 g/m2/day 

SAE 2000-01-1096 CE10 

CM15 

23/C 

40/C 

23/C 

40/C 

0.3 g/test 

2.6 g/test 

3.1 g/test 

9.5 g/test 

0.3 g/test 

2.5 g/test 

2.9 g/test 

8.5 g/test 

One commenter presented test data suggesting that fill level may affect permeation 

emissions.69 They tested four HDPE jugs, two filled to 40 percent and two filled to 100 percent 

with gasoline and saw a 15 percent difference in the average permeation results for the two fill 

levels (1.3 g/gal/day for 40 percent fill and 1.5 g/gal/day for 100 percent fill). Although this 

small measured difference was likely due to test variability, we performed our own testing to 

study the effect of fill level. For this testing, we used two 6-gallon HDPE portable marine fuel 

tanks. The fuel tanks were soaked with gasoline for 12 weeks to ensure a stabilized permeation 

rate. Each tank was tested at both 50 percent and 90 percent fill. No significant difference in 

permeation rate was observed for either tank. Table 5.3-9 presents the results in terms of 

g/gal/day at 29°C. 

Table 5.3-9: Effect of Fuel Tank Fill Level on Permeation 

for Two Portable Marine Fuel Tanks [g/gal/day] 

50% fill 90% fill 

Tank 1 

Tank 2 

1.16 

0.77 

1.21 

0.78 

Another study showed mixed results. Four automotive fuel systems (including fuel tank, 

hose, and other components) were tested for permeation with the fuel tanks filled with Fuel C to 

both 20 percent and 100 percent of capacity.70 Prior to the testing, the fuel tanks were soaked 

with fuel at the specified fill levels until a stable permeation rate was achieved. It was not clear 

what fraction of the permeation came from the fuel tanks compared to other fuel system 

components or how the fuel level affected the exposure of the other components. In this study, 

two of the fuel systems saw no significant change in permeation as a result of a change in fill 

level. These two fuel system were on older vehicles, one with an untreated and one with a 

fluorinated HDPE fuel tank. Two other fuel systems, using fuel tanks that meet automotive 

enhanced evaporative emission requirements, showed significant reductions in fuel system 

permeation (32 percent and 49 percent) when tested with the fuel tank filled to only 20 percent 

capacity. The study presented no rationale for this effect; however, it should be noted that these 

were very low permeation systems and measurement error would presumably be larger. These 

data are presented in Table 5.3-10. In addition, it is possible that the change in fill level affected 

whether or not there was fuel in the hoses. As discussed later in this chapter, the vapor 

5-40 
Feasibility of Evaporative Emission Control 

concentration in fuel hoses may be significantly lower than saturated when exposed only to 

vapor due to diffusion constraints. 

Table 5.3-10: Effect of Fuel Tank Fill Level on Permeation 

for Four Automotive Fuel Systems at 29/C [g/hour] 

Description of Fuel Tank 20% fill 80% fill 

Rig 2 

Rig 4 

Rig 5 

Rig 6 

enhanced evap system 

enhanced evap system 

HDPE fuel tank 

fluorinated HDPE fuel tank 

0.013 

0.021 

0.350 

0.095 

0.019 

0.041 

0.349 

0.094 

The California Air Resources Board also performed testing on three pairs of portable fuel 

tanks.71 All of the fuel tanks were identical 1 gallon tanks made out of HDPE. Each pair was 

filled to a different level with California certification fuel (30 percent, 50 percent and 70 percent 

fill). The fuel tanks were then sealed and subjected to five days of the California diurnal test 

(65-105/F) and weight loss was measured daily. Over the five days of testing, the tanks with 

lower fill levels actually saw significantly higher permeation than the other tanks. Looking at 

the last day of testing, which represents some conditioning of the fuel tanks by the fuel resulting 

in more stabilized permeation rates, the permeation rates are similar regardless of the fill level. 

This data, which is presented in Table 5.3-11, suggests that the fuel vapor in the tanks permeated 

at the same rate as (or higher than) the liquid fuel. 

Table 5.3-11: Effect of Fuel Tank Fill Level on Permeation 

for Three Pairs of Portable Fuel Tanks [g/day] 

Tank Fill Level 5-Day Permeation Last Day Permeation 

30a 

30b 

30% 1.79 

1.57 

1.87 

1.91 

50a 

50b 

50% 1.53 

1.03 

1.91 

1.43 

70a 

70b 

70% 1.26 

1.08 

1.85 

1.43 

5.3.1.5 Effect of background concentration on permeation 

As discussed above, permeation is driven by the difference in chemical potential between 

the inside and outside of the tank. If the concentration of vapor outside the fuel tank were large 

enough, it could reduce the permeation rate of fuel through the tank. One commenter presented 

test data suggesting that, at very low concentrations of vapor in the boat around the fuel tank, 

that the permeation rate would be significantly reduced.72 This test data was based on two three 

hour tests on 5 gallon HDPE bottles at 35°C. They measured 0.57 g/hr with a background 

5-41 
Final Regulatory Impact Analysis 

concentration of 26 ppm and 0.36 g/hr with a background of 212 ppm. No repeat tests were run. 

It is not clear why the above results were measured. Compared to the concentration of the fuel 

vapor in the tank, this difference between 212 and 26 ppm is minuscule (about three orders of 

magnitude difference from saturated vapor). It is more likely that this effect was due to test 

variation. 

To investigate this potential effect on permeation emissions further, we performed our 

own testing. First, we measured the concentration of fuel vapor around the fuel tank on a 

summer day in a runabout with the tank installed in the hull. This concentration was 1400 ppm. 

We then tested two different fuel tanks for permeation with different background concentrations. 

The background concentration was maintained by controlling the bleed of fresh air through the 

test container or SHED. Each test ran for about two weeks and the permeation rates were 

determined using the weight loss method. Prior to the testing, the tanks were soaked until a 

stable permeation rate was achieved, then new fuel was added to the tank just prior to beginning 

the test. The fuel tank was soaked until the fuel temperature stabilized at 29°C before the 

beginning weight was measured. The results, which are presented in Table 5.3-12, showed no 

significant difference in permeation as a function of background concentrations of hydrocarbon 

vapor. 

Table 5.3-12: Effect of Background Concentration on Permeation 

Fuel Tank Background [ppmC] Permeation [g/gal/day] 

6 gallon HDPE 30 

1500 

0.77 

0.78 

23 gallon cross-link PE 30 

150 

1350 

0.64 

0.67 

0.66 

5.3.2 Fuel Tank Permeation Reduction Technologies 

There are several strategies that can be used to reduce permeation from plastic fuel tanks. 

This section presents data collected on five permeation control strategies: sulfonation, 

fluorination, non-continuous barrier platelets, coextruded continuous barrier, and alternative 

materials. 

5.3.2.1 Sulfonation 

Sulfonation is a process where the surface of the fuel tank is treated to minimize 

permeation. The sulfonation process uses sulfur trioxide is used to create the barrier by reacting 

with the exposed polyethylene to form sulfonic acid groups on the surface. Current practices for 

sulfonation are to place fuel tanks on a small assembly line and expose the inner surfaces to 

sulfur trioxide, then rinse with a neutralizing agent. However, sulfonation can also be performed 

off-line. Either of these processes can be used to reduce gasoline permeation by more than 90 

5-42 
Feasibility of Evaporative Emission Control 

percent from new tanks.73 

We tested several sulfonated marine fuel tanks at 29°C for permeation. This testing 

included both HDPE blow-molded fuel tanks and cross-link polyethylene rotationally-molded 

tanks. Both gasoline and alcohol fuel blends were investigated. In some cases, the fuel tanks 

were exposed to durability testing as described in Section 5.6.2. The fuel tanks were stored with 

fuel in them (soaked) for preconditioning, then they were drained and then filled with fresh fuel 

prior to each permeation test. The purpose of the soak periods was to ensure that the fuel 

permeation rate had stabilized and the purpose of the pressure cycles and slosh testing was to 

evaluate the durability of the barrier treatment. 

We also collected data from ARB and other sources on the effectiveness of sulfonation 

for reducing permeation emissions from plastic fuel tanks. Most of this research has been 

performed on blow-molded HDPE fuel tanks. As shown in these data, it is important that the 

resin formulation be matched to the sulfonation process. The following discussions look at 

sufonation results on HDPE and on cross-link polyethylene separately. 

HDPE fuel tanks 

We tested several HDPE fuel tanks that were sulfonated on the internal surfaces. These 

included three 6-gallon and one 3.3 gallon portable marine fuel tanks and three all-terrain vehicle 

(ATV) fuel tanks. These fuel tanks were sent to a sulfonater for barrier treatment. Multiple fuel 

tanks were used so that they could be tested on certification gasoline , E10 (10 percent ethanol), 

and M15 (15 percent methanol). The test results, presented in Table 5.3-13, showed more than a 

90 percent reduction in permeation emissions from baseline. However, the two fuel tanks that 

were subjected to slosh testing saw emission levels above the standard. This may have been a 

material compatibility issue as discussed below. The test results are consistent with similar data 

collected by the California Air Resources Board. 

5-43 
Final Regulatory Impact Analysis 

Table 5.3-13: EPA Permeation Data on Sulfonated HDPE Fuel Tanks at 29°C 

Treatment Fuel Soak Period g/gal/day g/m2/day 

6 gallon portable marine fuel tanks 

baseline 

sulfonated 

sulfonated 

sulfonated 

sulfonated 

gasoline 

gasoline 

gasoline, sloshed 

E10 

M15 

15 weeks 

16 weeks 

12 weeks 

24 weeks 

24 weeks 

0.77 

0.04 

0.39 

0.14 

0.08 

8.53 

0.45 

4.30 

1.58 

0.84 

4 gallon ATV fuel tanks 

sulfonated 

sulfonated 

sulfonated 

gasoline 

E10 

M15 

20 weeks 

24 weeks 

24 weeks 

0.13 

0.06 

0.08 

1.05 

0.45 

0.64 

3.3 gallon portable fuel tank 

baseline 

sulfonated 

sulfonated 

E10 

E10 

E10, sloshed 

14 weeks 

14 weeks 

38 weeks 

0.96 

0.06 

0.16 

12.7 

0.83 

2.09 

We performed slosh testing on the 6 and 3.3 gallon portable marine fuel tanks with E10 

fuel. This slosh testing included 1 million cycles consistent with the durability test procedure. 

After the slosh testing, the permeation rates were measured to be 2.0 and 4.3 g/m2/day for the 3.3 

and 6 gallon fuel tanks, respectively. As discussed below, we believe that the impact of the 

durability testing on the effectiveness of sulfonation can be minimized if the sulfonation process 

and material properties are matched properly. However, this data supports the need for the 

durability testing requirements. 

The California Air Resources Board (ARB) collected test data on permeation rates from 

sulfonated portable fuel containers using California certification fuel.74 The results show that 

sulfonation can be used to achieve significant reductions in permeation from plastic fuel 

containers. This data was collected using a diurnal cycle from 18-41°C which is roughly 

equivalent to steady-state permeation testing at 29°C. The average emission rate for the 32 

sulfonated fuel tanks is 0.35 g/gal/day; however, there was a wide range in variation in the 

effectiveness of the sulfonation process for these fuel tanks. Some of the data outliers were 

actually higher than baseline emissions. This was likely due to leaks in the fuel tank which 

would result in large emission increases due to pressure built up with temperature variation over 

the diurnal cycle. Removing these five outliers, the average permeation rate is 0.17 g/gal/day 

with a minimum of 0.01 g/gal/day and a maximum of 0.64 g/gal/day. This data suggests that 

more than a 90 percent reduction in permeation from HDPE fuel tanks is possible through 

sulfonation. This data is presented in Table 5.3-14. 

5-44 
Feasibility of Evaporative Emission Control 

Table 5.3-14: Permeation Rates for Sulfonated 

Plastic Fuel Containers Tested by ARB Over a 18-41°C Diurnal 

Tank Capacity 

[gallons] 

Permeation Loss 

[g/gal/day] 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

2 

2 

2 

2 

2 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

5 

5 

5 

5 

5 

5 

5 

0.05 

0.05 

0.05 

0.06 

0.06 

0.06 

0.08 

0.12 

0.14 

1.23 

1.47 

1.87 

0.02 

0.02 

0.48 

0.54 

1.21 

0.03 

0.08 

0.32 

0.38 

0.42 

0.52 

0.64 

0.80 

0.01 

0.04 

0.05 

0.06 

0.11 

0.13 

0.15 

Variation can occur in the effectiveness of this surface treatment if the sulfonation 

process is not properly matched to the plastic and additives used in the fuel tank material. For 

instance, if the sulfonater does not know what UV inhibitors or plasticizers are used, they cannot 

maximize the effectiveness of their process. Earlier data collected by ARB showed consistently 

high emissions from sulfonated fuel tanks; however, ARB and the treatment manufacturers agree 

that this was due to inexperience with treating fuel tanks and that these issues have since been 

5-45 
Final Regulatory Impact Analysis 

largely resolved.75 

ARB also investigated the effect of fuel slosh on the durability of sulfonated surfaces. 

Three half-gallon fuel tanks used on Small SI equipment were sulfonated and tested for 

permeation before and after being sloshed with fuel in them 1.2 million times.76,77 These fuel 

tanks were blow-molded HDPE tanks used in a number of Small SI applications including 

pressure washers, generators, snowblowers, and tillers. The results of this testing show that an 

85 percent reduction in permeation was achieved on average even after the slosh testing was 

performed. Table 5.3-15 presents these results which were recorded in units of g/m2

/day. The 

baseline level for Set #1 is an approximation based on testing of similar fuel tanks, while the 

baseline level for Set #2 is based on testing of those tanks. 

The sulfonater was not aware of the materials used in the fuel tanks sulfonated for the 

slosh testing. After the tests were performed, the sulfonater was able to get some information on 

the chemical make up of the fuel tanks and how it might affect the sulfonation process. For 

example, the UV inhibitor used in some of the fuel tanks is known as HALS. HALS also has the 

effect of reducing the effectiveness of the sulfonation process. Two other UV inhibitors, known 

as carbon black and adsorber UV, are also used in similar fuel tank applications. These UV 

inhibitors cost about the same as HALS, but have the benefit of not interfering with the 

sulfonation process. The sulfonater claimed that if HALS were not used in the fuel tanks, a 97 

percent reduction in permeation would have been seen.78 To confirm this, one manufacturer 

tested a sulfonated tank similar to those in Set #2 except that carbon black, rather than HALS, 

was used as the UV inhibitor. This fuel tank showed a permeation rate of 0.88 g/m2/day at 

40°C79 which was less than half of what the CARB testing showed on their constant temperature 

test at 40°C.80 A list of resins and additives that are compatible with the sulfonation process is 

included in the docket.81,82 

5-46 
Feasibility of Evaporative Emission Control 

Table 5.3-15: Permeation Rates for Sulfonated Fuel Tanks 

with Slosh Testing by ARB Over a 18-41°C Diurnal 

Technology 

Configuration 

Units Tank 1 Tank 2 Tank 3 Average 

Set #1 Approximate 

Baseline 

g/m2

/day 10.4 10.4 10.4 10.4 

Set #1 Sulfonated g/m2

/day 

% 

reduction 

0.73 

93% 

0.82 

92% 

1.78 

83% 

1.11 

89% 

Set #1 Sulfonated & 

Sloshed 

g/m2

/day 

% 

reduction 

1.04 

90% 

1.17 

89% 

2.49 

76% 

1.57 

85% 

Set #2 Average Baseline g/m2

/day 12.1 12.1 12.1 12.1 

Set #2 Sulfonated g/m2/day 

% 

reduction 

1.57 

87% 

1.67 

86% 

1.29 

89% 

1.51 

88% 

Set #2 Sulfonated & 

Sloshed 

g/m2/day 

% 

reduction 

2.09 

83% 

2.16 

82% 

1.70 

86% 

1.98 

84% 

About a year and a half after the California ARB tests on the Set #2 fuel tanks, we 

performed permeation tests on these fuel tanks. During the intervening period, the fuel tanks 

remained sealed with California certification fuel in them. We drained the fuel tanks and filled 

them with fresh California certification fuel. We then measured the permeation rate at 29°C. 

Because this is roughly the average temperature of the California variable temperature test, 

similar permeation rates would be expected. The untreated fuel tanks showed slightly lower 

permeation over the constant temperature test. This difference was likely due to the difference in 

the temperature used for the testing. However, the sulfonated fuel tanks showed an increase in 

permeation. This increase in permeation appears to be the result of the 1.5 year additional fuel 

soak. After this long soak, the average permeation reduction changed from 84 to 78 percent. 

Table 5.3-13 presents this comparison. 

5-47 
Final Regulatory Impact Analysis 

Table 5.3-16: Permeation Rates [g/m2/day] for Sulfonated Fuel Tanks Tested by 

ARB and EPA on CA Certification Gasoline with a 11⁄2 Year Fuel Soak Differential 

Technology 

Configuration 

Temperatu 

re 

Tank 1 Tank 2 Tank 3 Average 

Baseline, CARB testing 18-41°C 12.1 12.1 12.1 12.1 

Baseline, EPA testing 

after 1.5 year additional 

fuel soak 

29°C 

% change 

11.5 

-5% 

11.4 

-6% 

11.2 

-7% 

11.4 

-6% 

Sulfonated, CARB 

testing 

18-41°C 2.09 2.16 1.70 1.98 

Sulfonated, EPA testing 

after 1.5 year additional 

fuel soak 

29°C 

% 

reduction 

2.48 

78% 

2.73 

76% 

2.24 

80% 

2.5 

78% 

After the above testing, we drained the fuel tanks and filled them with certification 

gasoline splash-blended with 10 percent ethanol (E10). We then soaked the fuel tanks for 20 

weeks to precondition them on this fuel. Following the preconditioning, we tested these fuel 

tanks for permeation at 29/C (85/F). Table 5.3-17 presents these emission results compared to 

the emission results for three baseline tanks (untreated) that were subject to the same 

preconditioning. Percent reductions are presented based on the difference between the 

sulfonated fuel tanks and the average results of the three untreated fuel tanks. 

Table 5.3-17: Permeation Rates for Sulfonated Fuel Tanks on E10 Fuel at 29/C 

Technology 

Configuration 

Units Tank 1 Tank 2 Tank 3 Average 

Baseline (untreated) g/m2

/day 13.9 13.7 14.4 14.0 

Sulfonated g/m2/day 

% 

reduction 

3.91 

72% 

4.22 

70% 

2.92 

79% 

3.69 

74% 

An in-use durability testing program was also completed for sulfonated HDPE fuel tanks 

and bottles.83 The fuel tank had a 25 gallon capacity and was removed from a station wagon that 

had been in use in southern California for five years (35,000 miles). The fuel tank was made of 

HDPE with carbon black used as an additive. After five years, the sulfonation level measured on 

the surface of the plastic fuel tank did not change. Tests before and after the aging both showed 

a 92 percent reduction in gasoline permeation due to the sulfonation barrier compared to the 

permeation rate of a new untreated tank. Testing was also done on 1 gallon bottles made of 

HDPE with 3 percent carbon black. These bottles were shown to retain over a 99 percent barrier 

5-48 
Feasibility of Evaporative Emission Control 

after five years. This study also looked at other properties such as yield strength and mechanical 

fatigue and saw no significant deterioration. 

One study looked at the effect of alcohol in the fuel on permeation rates from sulfonated 

fuel tanks.84 In this study, the fuel tanks were tested with both gasoline and various methanol 

blends. No significant increase in permeation due to methanol in the fuel was observed. 

XLPE fuel tanks 

We tested eight sulfonated cross-link polyethylene (XLPE) fuel tanks for permeation 

emissions. These tanks were produced by marine fuel tank manufacturers specifically for this 

testing. The fuel tanks were then treated by a sulfonater. For the first four tanks tested, the fuel 

tanks were molded using the resin formulation and processes currently used by the fuel tank 

manufacturers. When the sulfonation was applied, we observed that the barrier was soft and 

could be scraped off easily. When tested, the barrier on these fuel tanks was not as effective as 

had been seen on HDPE fuel tanks. 

Because the barrier could be scratched off, the sulfonater ascertained that the sulfonation 

had poor surface penetration and the darkness of the barrier suggested heavy oxidation. For the 

next batch of four test tanks, the sulfonater worked with the material supplier and roto-molder 

and attempted to develop a formulation that may be more compatible with sulfonation. They 

decided to use the same material, but bake it in the oven longer to remove more oxygen from the 

surface of the fuel tank. Four bake times were used to produce the four 6-gallon test tanks: 11, 

12, 14, and 16 minutes. It was observed that the sulfonation barrier could not easily be scratched 

off these fuel tanks. We tested the four sulfonated on E10 (10 percent ethanol) using the same 

procedures as for the HDPE tanks discussed above. The test results did not show a significant 

improvement.

 Another approach may be to mold an inner liner of HDPE inside a XLPE shell. These 

materials readily bond with each other and sulfonation has been demonstrated for HDPE. This 

construction, which is currently used in chemical storage applications, is performed in the oven 

through the use of a “drop box” in the mold containing the HDPE. This drop-box is opened part 

way through the oven cycle allowing for a HDPE layer to be molded on the inside of the fuel 

tank. 

5.3.2.2 Fluorination 

Another barrier treatment process is known as fluorination. The fluorination process 

causes a chemical reaction where exposed hydrogen atoms are replaced by larger fluorine atoms 

which form a barrier on the surface of the fuel tank. In this process, fuel tanks are generally 

processed post production by stacking them in a steel container. The container is then voided of 

air and flooded with fluorine gas. By pulling a vacuum in the container, the fluorine gas is 

forced into every crevice in the fuel tanks. As a result of this process, both the inside and outside 

surfaces of the fuel tank would be treated. As an alternative, fuel tanks can be fluorinated online by exposing the inside surface of the fuel tank to fluorine during the blow molding process. 

5-49 
Final Regulatory Impact Analysis 

However, this method may not prove as effective as off-line fluorination which treats the inside 

and outside surfaces. 

We tested several fluorinated marine fuel tanks at 29°C for permeation. This testing 

included both HDPE blow-molded fuel tanks and cross-link polyethylene rotationally-molded 

tanks. Both gasoline and alcohol fuel blends were investigated. In some cases, the fuel tanks 

were exposed to durability testing as described in Section 5.6.2. The fuel tanks were stored with 

fuel in them (soaked) for preconditioning, then they were drained and then filled with fresh fuel 

prior to each permeation test. The purpose of the soak periods was to ensure that the fuel 

permeation rate had stabilized and the purpose of the pressure cycles and slosh testing was to 

evaluate the durability of the barrier treatment. 

We also collected data from ARB and other sources on the effectiveness of fluorination 

for reducing permeation emissions from plastic fuel tanks. Most of this research has been 

performed on blow-molded HDPE fuel tanks. However, we believe that fluorination can also be 

applied effectively for injection-molded HDPE tanks as well. The following discussion looks at 

each material separately as well as rotationally-molded cross-link polyethylene. 

Blow-molded HDPE fuel tanks 

We tested one fluorinated HDPE fuel tank which we bought off the shelf and sent to a 

fluorinater for barrier treatment. The fuel tank type used was a 6-gallon portable marine fuel 

tank. The fuel tank was soaked for 20 weeks with certification gasoline prior to testing. We 

measured a permeation rate of 0.05 g/gal/day (0.56 g/m2

/day) which represents more than a 95 

percent reduction from baseline. We then began soaking this fuel tank on E10, subjected it to 

the pressure and slosh testing, and retested the fuel tank. The post durability testing result 

showed a permeation rate of 0.6 g/gal/day (6.8 g/m2/day). As discussed below, we believe that 

the impact of the durability testing on the effectiveness of fluorination on can be minimized if 

the fluorination process and material properties are matched properly. In addition, this fuel tank 

was treated to a significantly lower level of fluorination than is now available. However, this 

data supports the need for the durability testing requirements. 

The California Air Resources Board (ARB) collected test data on permeation rates from 

fluorinated fuel containers using California certification fuel.85,86 The results show that 

fluorination can be used to achieve significant reductions in permeation from plastic fuel 

containers. This data was collected using a diurnal cycle from 18-41°C which is roughly 

equivalent to steady-state permeation testing at 30°C. For the highest level of fluorination, the 

average permeation rate was 0.04 g/gal/day which represents a 95 percent reduction from 

baseline. Earlier data collected by ARB showed consistently high emissions from fluorinated 

fuel tanks; however, ARB and the treatment manufacturers agree that this was due to 

inexperience with treating fuel tanks and that these issues have since been largely resolved.87 

The ARB data is presented in Table 5.3-18. 

5-50 
Feasibility of Evaporative Emission Control 

Table 5.3-18: Permeation Rates for Fluorinated 

Plastic Fuel Containers Tested by ARB Over a 18-41°C Diurnal 

Barrier Treatment* Tank Capacity 

[gallons] 

Permeation Loss 

[g/gal/day] 

Level 4 

(average =0.09 g/gal/day) 

1 

1 

1 

5 

5 

5 

0.05 

0.05 

0.06 

0.11 

0.11 

0.15 

Level 5 

(average =0.07 g/gal/day) 

1 

1 

1 

1 

1 

1 

1 

1 

1 

2.5 

2.5 

2.5 

2.5 

2.5 

5 

5 

5 

0.03 

0.04 

0.05 

0.05 

0.07 

0.08 

0.11 

0.11 

0.12 

0.04 

0.04 

0.05 

0.07 

0.07 

0.05 

0.10 

0.11 

SPAL 

(average =0.04 g/gal/day) 

5 

5 

5 

0.04 

0.04 

0.04

 *designations used in ARB report; shown in order of increasing treatment 

All of the data on fluorinated fuel tanks presented above were based on fuel tanks 

fluorinated by the same company. Available data from another company that fluorinates fuel 

tanks shows a 98 percent reduction in gasoline permeation through a HDPE fuel tank due to 

fluorination.88 

ARB investigated the effect of fuel slosh on the durability of fluorinated surfaces. Two 

sets of three fluorinated fuel tanks were tested for permeation before and after being sloshed with 

fuel in them 1.2 million times.89,90 These fuel tanks were 0.5 gallon, blow-molded HDPE tanks 

used in a number of Small SI applications including pressure washers, generators, snowblowers, 

and tillers. The results of this testing show that an 80 percent reduction in permeation was 

achieved on average even after the slosh testing was performed for Set #1. However, this data 

5-51 
Final Regulatory Impact Analysis 

also showed a 99 percent reduction for Set #2. This shows the value of matching the barrier 

treatment process to the fuel tank material. Table 5.3-19a presents these results which were 

recorded in units of g/m2

/day. The baseline level for Set #1 is an approximation based on testing 

of similar fuel tanks, while the baseline for Set #2 is based on testing of those tanks. 

Table 5.3-19a: Permeation Rates for Fluorinated Fuel Tanks 

with Slosh Testing by ARB Over a 18-41°C Diurnal 

Technology 

Configuration 

Units Tank 1 Tank 2 Tank 3 Average 

Set #1 Approximate 

Baseline 

g/m2

/day 10.4 10.4 10.4 10.4 

Set #1 Fluorinated g/m2

/day 

% 

reduction 

1.17 

89% 

1.58 

85% 

0.47 

96% 

1.07 

90% 

Set #1 Fluorinated & 

Sloshed 

g/m2/day 

% 

reduction 

2.38 

77% 

2.86 

73% 

1.13 

89% 

2.12 

80% 

Set #2 Approximate 

Baseline 

g/m2

/day 12.1 12.1 12.1 12.1 

Set #2 Fluorinated g/m2

/day 

% 

reduction 

0.03 

>99% 

0.00 

>99% 

0.00 

>99% 

0.01 

>99% 

Set #2 Fluorinated & 

Sloshed 

g/m2/day 

% 

reduction 

0.07 

99% 

0.11 

99% 

0.05 

>99% 

0.08 

99% 

About a year and a half after the California ARB tests on the Set #2 fuel tanks, we 

performed permeation tests on these fuel tanks. During the intervening period, the fuel tanks 

remained sealed with California certification fuel in them. We drained the fuel tanks and filled 

them with fresh California certification fuel. We then measured the permeation rate at 29°C. 

Because this is roughly the average temperature of the California variable temperature test, 

similar permeation rates would be expected. The untreated fuel tanks showed slightly lower 

permeation over the constant temperature test. This difference was likely due to the difference in 

the temperature used for the testing. However, the fluorinated fuel tanks showed an increase in 

permeation. This increase in permeation appears to be the result of the 1.5 year additional fuel 

soak. Even after this long fuel soak, the fluorination achieves more than a 95 percent reduction 

in permeation. Table 5.3-19b presents this comparison. 

5-52 
Feasibility of Evaporative Emission Control 

Table 5.3-19b: Permeation Rates [g/m2/day] for Fluorinated Fuel Tanks Tested by 

ARB and EPA on CA Certification Gasoline with a 11⁄2 Year Fuel Soak Differential 

Technology 

Configuration 

Temperature Tank 1 Tank 2 Tank 3 Average 

Baseline, CARB testing 18-41°C 12.1 12.1 12.1 12.1 

Baseline, EPA testing 

after 1.5 year additional 

fuel soak 

29°C 

% change 

11.5 

-5% 

11.4 

-6% 

11.2 

-7% 

11.4 

-6% 

Fluorinated, CARB 

testing 

18-41°C 0.07 0.11 0.05 0.08 

Fluorinated, EPA testing 

after 1.5 year additional 

fuel soak 

29°C 

% reduction 

0.56 

95% 

0.62 

95% 

0.22 

98% 

0.47 

96% 

After the above testing, we drained the fuel tanks and filled them with certification 

gasoline splash-blended with 10 percent ethanol (E10). We then soaked the fuel tanks for 20 

weeks to precondition them on this fuel. Following the preconditioning, we tested these fuel 

tanks for permeation at 29/C (85/F). Table 5.3-21 presents these emission results compared to 

the emission results for three baseline tanks (untreated) that were subject to the same 

preconditioning. Percent reductions are presented based on the difference between the 

fluorinated fuel tanks and the average results of the three untreated fuel tanks. The slight 

increase in permeation on the E10 fuel was similar for the baseline and fluorinated fuel tanks and 

still resulted in permeation rates well below the standard. 

Table 5.3-20: Permeation Rates for Fluorinated Fuel Tanks on E10 Fuel at 29/C 

Technology 

Configuration 

Units Tank 1 Tank 2 Tank 3 Average 

Baseline (untreated) g/m2

/day 13.9 13.7 14.4 14.0 

Fluorinated g/m2/day 

% reduction 

0.43 

97% 

0.62 

96% 

0.62 

96% 

0.56 

96% 

The handheld industry also tested a number of fluorinated fuel tanks for their products.91 

This testing included three fuel types and two test temperatures. These test results suggest that 

fluorination may be used to significantly reduce permeation from handheld fuel tanks. Higher 

permeation rates were observed in CE10 than gasoline; however, it is not clear whether these 

impacts were due to increased permeation through the gaskets or through the tank. As shown 

earlier in Table 5.3-4b, the use of low permeation gasket materials can significantly improve 

permeation rates, especially on fuel CE10. This test data is presented in Table 5.3-21. 

5-53 
Final Regulatory Impact Analysis 

Table 5.3-21: Permeation Rates for Handheld Fuel Tanks Tested by Industry 

Tank Capacity Gasket Material Test Temp. Test Fuel Permeation Loss 

[g/m2

/day] 

695 NBR 28/C CE10 2.01 

2.88 

420 NBR 28/C CE10 1.46 

1.32 

400* NBR 

FKM 

40/C gasoline 0.56 

0.64 

252 NBR 40/C CE10 

gasoline 

CE10 

E10 

2.94 

0.84 

1.95 

1.40 

* A similar, untreated, tank was measured to have a permeation rate of 17.5 g/m2/day. 

Another study also looked at the effect of alcohol in the fuel on permeation rates from 

fluorinated fuel tanks.92 In this study, the fuel tanks were tested with both gasoline and various 

methanol blends. No significant increase in permeation due to methanol in the fuel was 

observed. 

Under their rule for small offroad equipment, California may issue executive orders to 

manufacturers with low emission products. As of August, 2006, ARB has issued 5 executive 

orders for low permeation fuel tanks.93 Under these executive orders, three fluorination 

approaches have been approved. The California fuel tank permeation standard is 1.5 g/m2/day 

tested at 40/C on California certification fuel. Table 5.3-22 presents the test results for the fuel 

tanks with ARB executive orders. Note that the reported emissions are the average of five test 

samples. 

Table 5.3-22: ARB Fuel Tank Executive Orders for Small Offroad Equipment 

EO# Test Fuel g/m2/day 

C-U-05-015 

C-U-06-019 

C-U-06-006 

Phase II 

Phase II 

Phase II 

1.10 

0.30 

0.38 

One automobile manufacturer used fluorination to reduce permeation on HDPE fuel 

tanks to meet the LEV I vehicle standards. This manufacturer used similar or more stringent 

requirements for fuel soak, durability, and testing than finalized today. At 40°C, this 

5-54 
Feasibility of Evaporative Emission Control 

manufacturer stated that they measured 0.15-0.2 g/day for fluorinated tanks compared to over 10 

g/day for untreated HDPE fuel tanks.94 

Injection-molded HDPE fuel tanks 

The issue has been raised by manufacturers that HDPE intended for injection-molding 

has a somewhat different composition than HDPE used for blow-molding. To address this 

concern, testing has been performed on fluorinated, injection-molded fuel tanks as well.95 These 

fuel tanks were tested using California’s TP-901 test procedures which preconditioning steps 

including fuel soak, slosh testing, and pressure-vacuum cycling. California Phase II gasoline 

was used for this testing. 

Three similar fuel tanks were tested also over the Federal test procedure.96 Under this 

testing, E10 fuel was used. Weight loss tests were performed before and after the durability tests 

in 40 CFR 1501.515.97 These durability tests included slosh testing, pressure vacuum cycling, 

and UV exposure. Results from this testing are presented in Table 5.3-23. The permeation was 

significantly higher when tested on E10 fuel, especially when accounting for differences in test 

temperature. In addition, permeation increased somewhat after the durability testing. However, 

the measured permeation rates were well below the fuel tank permeation standard on E10 after 

the durability testing. 

Table 5.3-23: Permeation Rates for Fluorinated, Injection-Molded Fuel Tanks [g/m2/day] 

Test Procedure Test 

Temperature 

Tank 1 Tank 2 Tank 3 Average 

California TP-901 40/C 0.28 0.26 0.27 0.27 

Federal Baseline 

After Durability Testing 

28/C 

28/C 

0.32 

0.30 

0.47 

0.92 

0.42 

0.57 

0.41 

0.60 

XLPE fuel tanks 

We tested several fluorinated cross-link polyethylene (XLPE) fuel tanks for permeation 

emissions. The first tank was a 6 gallon test tank produced by a marine fuel tank manufacturer 

specifically for this testing. The remaining fuel tanks were purchased on the open market. The 

fuel tanks were then treated by a fluorinater. We tested the first tank on certification gasoline. 

After a 20 week soak, we observed a permeation rate of 0.11 g/gal/day (1.52 g/m2

/day), which 

represented more than an 80 percent reduction in permeation. 

The remainder of the fluorinated tanks were tested on E10 (10 percent ethanol) using the 

same procedures as for the HDPE tanks discussed above. These fuel tanks were treated at a level 

equivalent to what the fluorinater uses for automotive applications. All of the fuel tanks were 

treated both on the inside and outside. The test results, presented in Table 5.3-24, showed 

emission reductions of about 40 percent on average. Emission results from the sloshed fuel 

5-55 
Final Regulatory Impact Analysis 

tanks were not significantly different than from the tanks that were not sloshed. 

Table 5.3-24: EPA Permeation Data on Fluorinated Cross-Link Fuel Tanks at 29°C on 

E10 

Fuel Tank Capacity Soak Period g/gal/day g/m2/day slosh test? 

1 12 gallons 29 weeks 0.27 

0.39 

4.1 

5.9 

no 

no 

0.32 4.9 no 

0.36 5.4 no 

0.38 5.8 no 

2 12 gallons 29 weeks 0.39 

0.34 

5.7 

5.0 

yes 

no 

0.42 6.2 no 

0.32 4.6 no 

3 12 gallons 29 weeks 0.28 

0.22 

0.22 

3.4 

2.6 

2.8 

yes 

no 

no 

5.3.2.3 Barrier Platelets 

Another approach to creating a permeation barrier in a fuel tank is to blend a low 

permeable resin in with the HDPE and extrude it with a single screw. The trade name typically 

used for this permeation control strategy is Selar®. The low permeability resin, typically nylon 

or EVOH, creates non-continuous platelets in the HDPE fuel tank which reduce permeation by 

creating long, tortuous pathways that the hydrocarbon molecules must navigate to pass through 

the fuel tank walls. Although the barrier is not continuous, this strategy can still achieve greater 

than a 90 percent reduction in permeation of gasoline. EVOH has much higher permeation 

resistance to alcohol than nylon; therefore, it would be the preferred material to use for meeting 

our standard which is based on testing with a 10 percent ethanol fuel. 

We tested several portable gas cans and marine tanks molded with low permeation noncontinuous barrier platelets 29°C. Six of fuel tanks tested were constructed using nylon as the 

barrier material. The remainder of the fuel tanks were constructed using ethylene vinyl alcohol 

(EVOH) as the barrier material. The advantage of EVOH is that it has much better resistance to 

alcohol than nylon. Five of the nylon based fuel tanks were tested on certification gasoline. The 

sixth tank was tested on E10 (10 percent ethanol) to evaluate the effectiveness of this material 

with alcohol blended fuel. The fuel tanks with the EVOH barrier were all tested on E10. 

Testing was performed after the fuel tanks had been filled with fuel and stored at room 

temperature. The purpose of the soak period was to ensure that the fuel permeation rate had 

stabilized. Although 20 weeks was generally accepted as an acceptable period, we soaked the 

tanks with gasoline for 22 weeks and the tanks with E10 for 37 weeks. The fuel tanks were 

5-56 
Feasibility of Evaporative Emission Control 

drained and then filled with fresh fuel prior to the permeation tests. Because the barrier platelets 

are integrated in the tank wall material, it did not seem likely that pressure or slosh testing would 

significantly affect the performance of this technology. 

Table 5.3-25 presents the results of the permeation testing on the fuel tanks with barrier 

platelets. These test results show more than an 80 percent reduction for the nylon barrier tested 

on gasoline. However, the nylon barrier does not perform as well when a fuel with a 10 percent 

ethanol blend is used. Testing on a pair of 2 gallon tanks with nylon barrier showed 80 percent 

percent higher emissions when tested on E10 than on gasoline. We also tested fuel tanks that 

used EVOH barrier platelets. EVOH has significantly better resistance to permeation on E10 

fuel than nylon (see Appendix 5D for material properties). For the fuel tanks blended with 6 

percent EVOH, we observed an average permeation rate of about 1.4 g/m2/day on E10 fuel 

which meets our permeation standard. 

Table 5.3-25: Permeation Rates for Plastic Fuel Containers 

with Barrier Platelets Tested by EPA at 29°C 

Percent 

Selar®* 

Tank Capacity 

[gallons] 

Test Fuel Fuel Soak 

[weeks] 

g/gal/day g/m2/day

 Nylon barrier platelets 

unknown** 

unknown** 

4% 

4% 

4% 

4% 

2 

2 

5 

5.3 

6.6 

6.6 

gasoline 

E10 

gasoline 

gasoline 

gasoline 

gasoline 

40 

40 

22 

22 

22 

22 

0.54 

0.99 

0.35 

0.11 

0.15 

0.14 

3.7 

6.8 

4.1 

1.2 

1.6 

1.5

 EVOH barrier platelets 

2% 

4% 

4% 

6% 

6% 

6.6 

6.6 

6.6 

6.6 

6.6 

E10 

E10 

E10 

E10 

E10 

37 

37 

37 

37 

37 

0.23 

0.14 

0.15 

0.08 

0.09 

3.0 

1.9 

2.0 

1.4 

1.4 

*trade name for barrier platelet technology used in test program 

** designed to meet California permeation requirement 

Manufacturers raised the concern about whether or not a tank using barrier platelets 

would have a stabilized permeation rate after 20 weeks. In other words, manufacturers were 

concerned that this technology may pass the test, but have a much higher permeation rate in-use. 

We tested one of the 4 percent and 6 percent EVOH tanks on E10 again after soaking for a total 

of 104 weeks (2 years). The measured permeation rates were 2.0 and 1.4 g/m2/day for the 4 

percent and 6 percent EVOH tanks, respectively, which represents no significant changes in 

permeation from the 37 week tests. In contrast we measured the 4 percent nylon tanks again 

after 61 weeks and measured a permeation rates of 2.8 and 2.7 g/m2

/day which represented about 

5-57 
Final Regulatory Impact Analysis 

an 80-90 percent increase in permeation compared to the 22 week tests. 

The California Air Resources Board (ARB) collected test data on permeation rates from 

portable fuel containers molded with low permeation non-continuous barrier platelets using 

California certification fuel. These fuel tanks all used nylon as the barrier resin. The results 

show that this technology can be used to achieve significant reductions in permeation from 

plastic fuel containers. This data was collected using a diurnal cycle from 18-41°C which is 

roughly equivalent to steady-state permeation testing at 30°C. Because the data is reported in 

g/gal/day, we only include the data on fuel tanks here that are compatible in size with marine 

fuel tanks. This test data showed that more than a 90 percent reduction in permeation is 

achievable through the use of nylon barrier platelets. However, all of this testing was performed 

on California certification fuel which does not include ethanol. 

Table 5.3-26: Permeation Rates for Plastic Fuel Containers 

with Barrier Platelets Tested by ARB Over a 18-41°C Diurnal 

Percent Selar®* Tank Capacity 

[gallons] 

Permeation Loss 

[g/gal/day] 

4% 

(average =0.12 g/gal/day) 

5 

5 

5 

5 

5 

6 

6 

0.08 

0.09 

0.13 

0.16 

0.17 

0.08 

0.10 

6% 

(average =0.09 g/gal/day) 

5 

5 

5 

5 

5 

5 

6 

6 

0.07 

0.07 

0.07 

0.08 

0.12 

0.17 

0.06 

0.07 

8% 

(average =0.07 g/gal/day) 

5 

5 

6 

6 

0.08 

0.10 

0.05 

0.06 

*trade name for barrier platelet technology used in test program 

Dupont, who manufacturers Selar®, has performed testing on HDPE with higher 

blends of EVOH (known as Selar RB®). Table 5.3-27 presents permeation rates for HDPE and 

three Selar RB® blends when tested at 60°C on xylene.98 Xylene is a component of gasoline and 

gives a rough indication of the permeation rates on gasoline. This report also shows a reduction 

of 99 percent on naptha and 98 percent on toluene for 8 percent Selar RB®. 

5-58 
Feasibility of Evaporative Emission Control 

Table 5.3-27: Xylene Permeation Results for Selar RB® at 60°C 

Composition Permeation, g mm/m2/day % Reduction 

100% HDPE 

10% RB 215/HDPE 

10% RB 300/HDPE 

15% RB 421/HDPE 

285 

0.4 

3.5 

0.8 

– 

99.9% 

98.8% 

99.7% 

5.3.2.4 Alternative Materials 

Permeation can also be reduced from fuel tanks by constructing them out of a lower 

permeation material than HDPE. Examples of alternative materials are metal, various grades of 

plastic, and new fiberglass construction. 

5.3.2.4.1 Metal 

Gasoline does not permeation through metal. Therefore, the only permeation from a 

metal fuel tank would be through rubber gaskets or O-rings that may be used to seal connections 

on the fuel tank. Examples would be the gasket or O-ring in a fuel cap or a bolted-on component 

such as a sender unit for a marine tank. Presumably, the exposed surface area of the gaskets 

would be small enough that a metal fuel tank would be well below our permeation standard. 

One issue with metal fuel tanks, however, is fuel leakage due to corrosion. A study sponsored 

by the Coast Guard in 1994 showed that aluminum (and even stainless steel) fuel tanks are prone 

to failure, both in salt water and fresh water applications., due to corrosion.99 Fuel leakages 

would not only be an environmental issue, but could be a safety issue as well. Aluminum fuel 

tank manufacturers have stated that corroding fuel tanks are typically due to improper 

installation. 

5.3.2.4.2 Alternative Plastics 

There are grades of plastics other than HDPE that could be molded into fuel tanks. One 

material that has been considered by manufacturers is nylon; however, although nylon has 

excellent permeation resistance on gasoline, it has poor chemical resistance to alcohol-blended 

fuels. As shown in Appendix 5D, nylon could be used to achieve more than a 95 percent percent 

reduction in permeation compared to HDPE for gasoline. However, for a 10 percent ethanol 

blend, this reduction would significantly less depending on the grade of nylon. For a 15 percent 

methanol blend, the permeation would actually be several times higher through nylon than 

HDPE. 

Some handheld equipment, primarily chainsaws, use structurally-integrated fuel tanks 

where the tank is molded as part of the body of the equipment. In these applications, the frames 

(and tanks) are typically molded out of nylon for strength. We tested structurally-integrated fuel 

tanks from four handheld equipment manufacturers at 29/C on both gasoline and a 10 percent 

ethanol blend. The test results suggest that permeation emissions are 20 to 70 percent higher on 

5-59 
Final Regulatory Impact Analysis 

E10 than on gasoline for these fuel tanks. Note these fuel tanks are capable of meeting the 

standards using their current materials. In the cases where the permeation rates were higher than 

these standards, it was observed that the fuel cap seals had large exposed surface areas on the Orings, which were not made of low permeation materials. Emissions could likely be reduced 

significantly from these tanks with improved seal designs. Table 5.3-28 presents the results of 

this testing. 

Table 5.3-28: Permeation Rates for Nylon Handheld Fuel Tanks Tested by EPA at 29°C 

Tank ID Application Material Test Fuel Permeation Loss 

[g/m2/day] 

R1 

R2 

R3 

clearing saw nylon 6 gasoline 

E10 

E10 

0.34 

0.42 

0.48 

B1 

B2 

B3 

B4 

hedge clipper nylon 6, 33% glass gasoline 

E10 

E10 

E10 

0.62 

1.01 

1.12 

0.93 

W1 

W2 

W3 

chainsaw nylon 6, 30% glass gasoline 

E10 

E10 

1.45 

2.18 

2.46 

G1 

G2 

G3 

chainsaw nylon 6, 30% glass gasoline 

E10 

E10 

1.30 

1.41 

2.14 

Other materials which have excellent permeation resistance even with alcohol-blended 

fuels are acetal copolymers and thermoplastic polyesters. These polymers can be used to form 

fuel tanks in the blow-molding, rotational-molding, and injection-molding processes. An 

example of an acetal copolymer is known as Celcon® which has excellent chemical resistance to 

fuel and has been shown to be durable based on exposure to automotive fuels for 5000 hours at 

high temperatures.100 As shown in Appendix 5D, Celcon would result in more than a 99 percent 

reduction in permeation compared to HDPE for gasoline. On a 10 percent ethanol blend, the use 

of Celcon would result in more than a 95 percent reduction in permeation. Two thermoplastic 

polyesters, known as Celanex® and Vandar®, are also being considered for fuel tank construction 

and are being evaluated for permeation resistance by the manufacturer. Celcon has a more 

crystalline structure than Vandar resulting in lower permeation but less impact resistance. 

We tested a 1-liter blow-molded Vandar fuel tank and three rotationally-molded 3-liter 

fuel tanks made of impact toughened Celcon for permeation at 29°C on E10 fuel. Prior to the 

permeation testing, the fuel containers were soaked in E10 for more than 20 weeks. These test 

results are included in Table 5.3-29 below. For the Celcon tank tests, higher emissions were 

observed in the second week than the first week. This behavior was seen in repeat tests and was 

5-60 
Feasibility of Evaporative Emission Control 

likely due to deterioration of the epoxy seal used in this testing. Therefore, the actual emission 

rates of the material are likely lower than presented below. More detailed data on this testing is 

available in the docket.101 

Table 5.3-29: Permeation Results Acetal Copolymer Fuel Tanks at 29°C on E10 

Material Name Material Type g/gal/day g/m2/day 

Vandar V1 thermoplastic polyester 1.7 5.6 

Impact C10 

Resistant 

C11 

Celcon C13 

modified 

acetal copolymer 

0.13 

0.09 

0.10 

0.75 

0.53 

0.59 

Fuel tank manufacturers have expressed some concern that the acetal copolymer is not as 

tough as cross-link polyethylene. Thermoplastic polyesters have better impact resistance, but 

higher permeation. The impact toughened fuel tanks mentioned above were in response to these 

concerns. Also, the rotational molding process must be better controlled to use these materials in 

comparison to XLPE. The temperature profile must be tightly controlled to uses Celcon, or 

formaldehyde gases may form. The moisture level of Vandar must be kept low prior to molding. 

Acetal copolymers are also used today to produce many fuel resistant automotive 

components such as low permeation fuel caps. This construction has been used for many years 

in automotive applications and now acetal copolymers are being used to manufacture low 

permeation fuel caps for nonroad equipment as well. 

Another low permeation thermoplastic that can be used in the manufacture of fuel tanks 

is a polyester/polycarbonate alloy. One example is marketed under the trade name of Xenoy 

6620. This engineered plastic is impact modified and is intended for the injection molding 

process. The polyester provides good chemical resistance and the polycarbonate provides the 

impact resistance. Permeation testing was performed on a fuel tank made of Xenoy 6620 

following the California test procedures. At 40/C on California Phase II CERT fuel, the 

measured permeation rate was 0.26 g/m2

/day.102 The manufacturer of this material also has a 

version that is modified slightly so that it can be used in the blow-molding process. 

5.3.2.4.3 Low Permeation Fiberglass 

One manufacturer has developed a low permeation fiberglass fuel tank construction.103 

The composite tanks are fabricated using a glass fiber reinforced closed cell urethane composite 

sheet as substrate and assembled with structural urethane adhesive as a fastening medium. These 

fuel tanks may be hand constructed, or for larger volume production, they may be molded at 

lower cost. Once fully assembled with necessary fuel fittings the tank is coated with fiberglass 

reinforced resin, sufficient for H-24 ABYC (American Boat and Yacht Council) and 33 CFR 

183.510 standards for fuel systems mechanical strength requirements. A final gel coat finish may 

5-61 
Final Regulatory Impact Analysis 

was applied for aesthetics. 

Permeation control is achieved by incorporating fillers into a resin system and coating the 

assembled tank interior and exterior. This filler is made up of nanocomposites (very small 

particles of treated volcanic ash)4 which are dispersed into a carrier matrix. This construction 

creates a tortuous pathway for hydrocarbon migration through the walls of the fuel tank. We 

tested a 14 gallon fuel tank provided by this manufacturer and measured a permeation rate of 

0.97 g/m2/day on E10 fuel at 29°C. Other advantages of this technology are improved strength 

and flame resistance compared to plastic fuel tanks. 

5.3.2.5 Multi-Layer Construction 

Fuel tanks may also be constructed out of multiple layers of materials. In this way the 

low cost and structural advantages of traditional materials can be utilized in conjunction with 

higher grade materials which can provide effective permeation resistance. Today, fuel tanks are 

made in many ways including higher volume blow-molding, lower volume injection molding, 

and very low volume rotational-molding. The discussion below presents data on several multilayer fuel constructions. 

5.3.2.5.1 Blow-Molded Coextruded Barrier 

Coextruded barrier technology has been long established for blow-molded automotive 

fuel tanks. Data from one automobile manufacturer showed permeation rates of 0.01-0.03 g/day 

for coextruded fuel tanks at 40°C on EPA certification fuel. They are using this technology to 

meet LEV II vehicle standards. For comparison, this manufacturer reported permeation rates of 

more than 10 g/day for standard HDPE fuel tanks.104 

Another study looks at the permeation rates, using ARB test procedures, through multilayer fuel tanks.105 The fuel tanks in this study were 6 layer coextruded plastic tanks with EVOH 

as the barrier layer (3 percent of wall thickness). The outer layers were HDPE and two adhesive 

layers were needed to bond the EVOH to the polyethylene. The sixth layer was made of 

recycled polyethylene. The two test fuels were a 10 percent ethanol blend (CE10) and a 15 

percent methanol blend (CM15). See Table 5.3-30. 

Table 5.3-30: Permeation Results for a Coextruded Fuel Tank Over a 18-41°C Diurnal 

Composition Permeation, g/day % Reduction 

100% HDPE (approximate) 

3% EVOH, 10% ethanol (CE10) 

3% EVOH, 15% methanol (CM15) 

6 - 8 

0.2 

0.3 

– 

97% 

96% 

4 Chemically modified montmorillonite for nanocomposite formulation 

5-62 
Feasibility of Evaporative Emission Control 

The California Air Resources Board tested two sets of three 5-gallon portable fuel 

containers.106 Each set was manufactured by a different company, but all of the fuel tanks were 

blow-molded with a coextruded barrier layer. Testing was performed over the California 18-

41/C temperature cycle with California Phase II gasoline. Testing was performed with and 

without the spouts removed. The test data presented in Table 5.3-31 was after 174 days of fuel 

soak with the spouts removed and the openings welded shut. California reported the test results 

in grams per gallon. Table 5.3-31 also presents approximate g/m2

/day values based on the 

relationship between tank capacity and inside surface area used in the NONROAD2005 

emissions model. 

Table 5.3-31: ARB Permeation Results for a Coextruded Portable Fuel Tanks 

Fuel Tank Permeation, g/gal/day Approximate Rate in g/m2/day 

B1 

B2 

B3 

Average 

0.01 

0.01 

0.01 

0.01 

0.09 

0.11 

0.11 

0.10 

M1 

M2 

M3 

Average 

0.01 

0.02 

0.02 

0.02 

0.14 

0.21 

0.18 

0.17 

The handheld industry also tested a number of fuel tanks for their products that had been 

coextruded with an EVOH barier.107 Even with NBR gaskets on the fuel caps, these tanks had 

permeation rates well below the new standards. This test data is presented in Table 5.3-32. 

Table 5.3-32: Permeation Rates for Handheld Fuel Tanks Tested by Industry 

Tank Capacity Gasket Material Test Temp. Test Fuel Permeation Loss 

[g/m2

/day] 

1840 NBR 28/C CE10 0.23 

0.26 

470 NBR 28/C CE10 0.75 

0.54 

Another approach has recently been developed in which a multi-layer fuel tank can be 

blow-molded with only two layers.108 In this construction, a barrier layer of a polyarylamide 

known as Ixef MXD6 is used on the inside of a HDPE fuel tank. Ixef has permeation properties 

similar to EVOH. Test results showed a permeation rate of 0.8 g-mm/m2

/day at 60/C on CE10 

for a test film of Ixef. Unlike EVOH, Ixef can be exposed directly to the fuel which removes the 

need for an inner layer of HDPE. In addition, a tie material can be blended into the HDPE which 

will allow the polyarylamide to bond directly to the HDPE rather than using an adhesive layer. 

5-63 
Final Regulatory Impact Analysis 

Permeation emissions were measured on five 2.5 liter fuel tanks at 28/C using fuel 

CE10.109 During the preconditioning of these fuel tanks, the pressure-vacuum, slosh, and UVexposure durability tests were performed. All of the testing was performed using stock fuel caps 

and gaskets. One of the fuel tanks showed considerably higher emissions than the others. This 

higher emitting tank was found to have an issue with the interface between the tank and the fuel 

cap. In general, the permeation rates were well below the tank permeation standard. These test 

results are presented in Table 5.3-33. 

We also tested three test bottles and three fuel tanks made using this construction for 

permeation emissions. The test bottles were about 1.3 liters in volume and used a fluoropolymer 

gasket under the caps. The fuel tanks were similar to those described above. Each of the test 

bottles and tanks was filled with E10 and soaked for more than 20 weeks. Prior to the two week 

weight loss test, fresh fuel was added to each bottle/tank. As shown in Table 5.3-33, the 

measured permeation results were well below the new tank permeation standard. 

Table 5.3-33: Permeation Results Ixef Barrier Test Bottles at 29°C on E10 

Tank Conditions Preconditioning g/gal/day g/m2/day 

tank 1 28/C, fuel soak, slosh, 0.11 0.67 

tank 2 Fuel CE10 pressure-vacuum, 0.14 0.87 

tank 3 and UV exposure 0.19 1.17 

tank 4 0.13 0.80 

tank 5a 0.34 2.07 

tank 6 29/C, fuel soak 0.04 0.36 

tank 7 Fuel E10 0.19 1.80 

tank 8 0.04 0.36 

bottle 1b 

bottle 2b 

bottle 3b 

29/C, 

Fuel E10 

fuel soak 0.05/0.02 

0.14/0.02 

0.07/0.02 

0.26/0.12 

0.72/0.12 

0.39/0.12 

a

 interface issue reported with cap b repeated test with epoxy seal on fuel cap 

Tanks 6-8 and bottles 1-3 were tested by EPA using screw on fuel caps with gaskets. For 

the test bottles, gaskets were cut at EPA from FKM rubber. It was thought that the permeation 

results were affected by the seal at the fuel cap. Therefore, the tests were rerun 6 months later 

using epoxy as a secondary seal at the fuel cap. As a result, much lower permeation rates were 

measured for all three test bottles. For the fuel tanks, the stock fuel caps and gaskets were used. 

One of the tanks had significantly higher permeation emissions than the other two tanks. This 

difference may have been a seal issue at the fuel cap. 

5.3.2.5.2 Rotational Molded Dual-layer Construction 

As discussed above, an inner layer can be molded into the inside of a rotationally molded 

5-64 
Feasibility of Evaporative Emission Control 

fuel tank through the use of a drop-box that opens after the XLPE tank begins to form. Through 

this method, a XLPE fuel tank could be molded with a low permeation inner barrier. With this 

construction, it may be possible to reduce the amount of XLPE used depending on the structural 

characteristics of the inner liner material. For instance, acetal copolymer can be rotationally 

molded and could be used as the inner liner. This way, the permeation characteristics of an 

acetal copolymer could be achieved through an inner liner while still retaining the toughness of 

XLPE . One issue would be that acetal copolymers do not readily adhere to XLPE. Therefore 

fitting designs would need to account for this. 

Another material that could be used in a multi-layer approach is nylon which comes in 

many grades. Typical nylon grades used in Small SI fuel tank constructions may not perform 

well in marine applications because of the hygroscopic nature of these nylons. In other words, 

typical nylon adsorbs water which can make it brittle. In addition, E10 fuel permeates through 

nylon much more readily than gasoline. 

One manufacturer is working with a nylon known as Rilsan® polyamide 11 (PA 11) in 

constructing low permeation multi-layer rotational-molded fuel tanks.110 Rilsan® polyamide 11 

has two advantages to traditional nylons in that it is not hygroscopic and it is more resistive to 

alcohol fuels. One manufacturer has manufactured fuel tanks using the PA11 as an inner liner in 

a polyethylene shell. The manufacturer using this approach reports a permeation rate of about 3 

g-mm/m2

/day on fuel CE10 at 28°C compared to about 30 g-mm/m2/day for XLPE. In addition, 

the nylon used in multi-layer constructions is formulated with a polyethylene graft that causes it 

to adhere well to XLPE. This prevents the layers from separating in use. 

We tested two 10 gallon multi-layer rotational molded fuel tanks at 29°C with E10 fuel 

after a 35 week soak with two fuel changes during that period.111 One of the tanks was molded 

with an outer shell of medium-density polyethylene while the other was molded with an outer 

shell of cross-link polyethylene. The long soak period was due to test equipment problems and 

the fuel was changed with each test attempt. However, it presents valuable data on the longer 

term effectiveness of this technology. This test data is presented in Table 5.3-34. The 

manufacturer reported that this tank design passed testing on the Coast Guard burn, pressure, 

shock, and impulse test requirements.112,113,114,115 In addition, a tank of this construction was 

tested and passed the tank durability tests for snowmobiles specified in SAE J288.116 These tests 

include cold (-40/C) and hot temperature (60/C) immersion and drop tests. 

Typically, multi-layer rotational-molded fuel tanks are constructed with the use of a drop 

box which adds the inner-layer material into the mold after the first material sets. Other 

approaches are to use a meltable bag containing the inner-layer material or even to pull the mold 

from the oven to add the inner-layer material. However, one manufacturer, that participated in 

the SBREFA process, has stated that they have developed a method to mold the inner liner 

without the use of a drop box or other approach that lengthens molding cycle time. This fuel 

tank manufacturer is selling fuel tanks using this construction for use in Small SI equipment and 

is selling mono-layer XLPE rotational-molded tanks for use in boats. 

5-65 
Final Regulatory Impact Analysis 

Table 5.3-34: Permeation Results PA 11/PE Fuel Tanks at 29°C on E10 

Tank Outer Shell g/gal/day g/m2/day 

1 

2 

MDPE 

XLPE 

0.05 

0.06 

0.71 

0.79 

Under their rule for small offroad equipment, California may issue executive orders to 

manufacturers with low emission products. As of August, 2006, ARB has issued 5 executive 

orders for low permeation fuel tanks.117 Under these executive orders, two basic multi-layer 

rotomolded (XLPE and nylon) approaches have been approved. The California fuel tank 

permeation standard is 1.5 g/m2/day tested at 40/C on California certification fuel. However, 

most of the testing was performed on fuel CE10 which is a significantly more aggressive fuel for 

permeation. Table 5.3-35 presents the test results for rotational-molded fuel tanks with ARB 

executive orders. Note that the reported emissions are the average of 3-5 test samples. 

Table 5.3-35: ARB Fuel Tank Executive Orders for Small Offroad Equipment 

EO# Test Fuel g/m2

/day 

C-U-05-005 CE10 

Phase II 

0.81 

0.18 

C-U-06-014 CE10 

CE10 

CE10 

0.10 

0.00 

0.09 

There is another approach to dual-layer rotomolded fuel tanks under development that 

uses a “single shot” approach to molding.118 In this method a material known as polybutylene 

terephthalate cyclic oligimor (CBT) is combined with the XLPE in the mold. Because of the 

different melt rates and viscosities of the two materials, during the mold process, the CBT® 

polymerizes into a thermoplastic known as polybutylene terephthalate (PBT) to form a barrier 

layer on the inside of the fuel tank. Adhesion between the PBT and XLPE comes from 

mechanical bonding between the two layers. This material can be used without lengthening the 

cycle time for rotational molding, and it does not require forced cooling.119 Initial testing shows 

a permeation rate of <1 g/m2

/day when tested with fuel CE10 at 40/C for a sample with a 3.9 mm 

total wall thickness.120 This wall thickness for this testing was composed of 0.9mm CBT and 

3.0mm XLPE. PBT itself has a permeation rate on CE10 at 40/C of less than 0.05 g-mm/m2/day. 

5.3.2.5.3 Injection-Molded Dual-Layer Construction 

To add a barrier layer in the injection molding process, a thin sheet of the barrier material 

may be placed inside the mold prior to injection of the poleythylene. The polyethylene, which 

generally has a much lower melting point than the barrier material, bonds with the barrier 

material to create a shell with an inner liner. 

5-66 
Feasibility of Evaporative Emission Control 

5.3.2.5.4 Thermoformed Multi-Layer Construction 

As an alternative, multiple layers can be created through thermoforming.121 In this 

process, sheet material is heated then drawn into two vacuum dies. The two halves are then 

fused while the plastic is still molten to form the fuel tank. Before the halves are fused together, 

it is possible to add components inside of the fuel tank. Low permeation fuel tanks can be 

constructed using this process by using multi-layer sheet material. This multi-layer sheet can be 

extruded using similar materials to multi-layer blow-molded fuel tank designs. A typical barrier 

construction would include a thin EVOH barrier, adhesion layers on both sides, a layer of HDPE 

regrind, and HDPE layers on the outside surfaces. 

This process has low capital costs compared to blow-molding and should be cost 

competitive with injection molding and rotational-molding. Manufacturers have indicated that 

this construction could be coated with an intumescent material which would help it pass the 

Coast Guard fire test. This coating could be applied directly to the multi-layer plastic sheets 

while they are still hot after extrusion. Once the plastic cools, it could be applied using flame 

ionization or electric arcing to increase the surface are of the plastic for adhesion. 

EPA tested two, 5.6 gallon, thermoformed fuel tanks for permeation. These fuel tanks 

were constructed as described above with a thin EVOH barrier and were soaked with E10 for 27 

weeks prior to testing. Due to test variability, testing was repeated at 35 and 44 weeks (fresh 

fuel was added prior to each weight loss test). From day to day, a constant weight loss was not 

always observed, and weight gains were occasionally seen. This variability in measured weight 

loss was likely due to the very low permeation rates combined with the effect of atmospheric 

conditions on measured weight. The highest variations in weight loss were observed when 

storms passed through suggesting that the changes in barometric pressure and relative humidity 

were affecting the buoyancy of the fuel tanks (discussed in more detail in Section 5.6.2.3). In 

the third round of testing (after 44 weeks), barometric pressure and humidity were measured and 

deemed to be relatively stable. In addition, a smaller tank with sand in it (rather than fuel) was 

measured simultaneously as a control to give some indication of the buoyancy effect. A small 

weight loss was measured for the control tank, suggesting that the measured test results may 

slightly overstate the permeation for the thermoformed fuel tanks. Table 5.3-36 presents the test 

results for each of the three tests. 

5-67 
Final Regulatory Impact Analysis 

Table 5.3-36: Permeation Results Multilayer Thermoformed Fuel Tanks at 29°C on E10 

Soak (weeks) Tank g/gal/day g/m2

/day 

27 #16 

#21 

0.01 

0.01 

0.15 

0.05 

35 #16 

#21 

0.01 

0.01 

0.07 

0.09 

44 #16 

#21 

0.01 

0.00 

0.11 

0.04 

Average #16 

#21 

0.01 

0.01 

0.11 

0.06 

5.3.2.5.5 Epoxy Barrier Coating 

Another approach that has shown promising results is to coat a plastic fuel tank with a 

low permeation epoxy barrier coating. Early attempts at coating a plastic fuel tank resulted in 

coatings that eventually wear off due to the difficulty of bonding some materials to HDPE and 

XLPE. However, because fluorination increases the surface energy of the plastic, a low level of 

fluorination can be used to make it possible to apply an epoxy coating, even to XLPE. Because 

this approach is applied to the fuel tank post-molding, it can be used for any plastic fuel tank, 

regardless of the production molding method. 

We performed permeation testing on six 12 gallon rotationally-molded XLPE fuel tanks 

with a thin, low-permeation epoxy coating. This coating was a two-part epoxy that was sprayed 

onto the tank and thermally cured in 45 minutes. Prior to the permeation measurements, the fuel 

tanks were soaked with E10 fuel at about 25°C for 15 weeks. The tanks were then drained and 

fresh E10 was added prior to the 29°C constant temperature permeation test. Inspection of the 

externally coated fuel tanks showed that the epoxy was unevenly applied and that some bare 

spots existed. This was reflected in the unsatisfactory permeation results. A more careful 

coating would be expected to result in similar results as the internal coatings. One of the 

externally coated fuel tanks was over-coated with a 1-part epoxy that was cured with a 45 second 

UV exposure. This tank was soaked for an additional 6 weeks prior to retesting. These test 

results, which are presented in Table 5.3-37, show that this technology can be used to reduce 

permeation emissions by more than 90 percent. 

5-68 
Feasibility of Evaporative Emission Control 

Table 5.3-37: EPA Permeation Data on Epoxy Coated XLPE Fuel Tanks at 29°C on E10 

Fuel Tank Set Coating Soak Period g/gal/day g/m2/day slosh test? 

1 Inside 

Thermocured 

15 weeks 0.04 

0.001 

0.07 

0.6 

0.02 

1.0 

no 

no 

yes 

2 Outside 

Thermocured* 

15 weeks 0.13 

0.23 

0.23 

1.9 

3.3 

3.3 

no 

no 

yes 

3 Outside 

UV cured 

additional 

6 weeks 

0.03 0.4 no 

* inspection showed uneven application of the coating which affected permeation results 

Since the above testing was performed, the fluorinater and the epoxy manufacturer who 

developed this approach have performed more testing on their UV cured, 1-part epoxy. The 

testing was performed on epoxy coated HDPE bottles and 2 gallon fuel tanks using the 

California ARB test procedure of 40°C with California certification fuel.122 At 29°C, we would 

expect the permeation rate to be about half of these levels due to the relationship between 

permeation and temperature discussed above in Section 5.3.1.2. The results for this testing were 

reported to be 0.3 g/m2/day on average for both the bottles and tanks on gasoline. The bottles 

had a permeation rate of 0.5 g/m2/day on gasohol (ethanol blend). This technology resulted in 

better than 95 percent reductions in permeation. Table 5.3-38 presents the test results after a 9 

week fuel soak at 40°C. 

Table 5.3-38: Permeation Data: Epoxy Coated HDPE Fuel Tanks at 40°C on CA Cert Fuel 

Fuel Tank g/gal/day g/m2/day 

1 

2 

3 

4 

0.04 

0.02 

0.02 

0.08 

0.25 

0.09 

0.11 

0.49 

Roto-molders of marine fuel tanks generally use cross-link polyethylene. The advantage 

of XLPE is that its cross-link structure causes it to behave like thermoset which helps the fuel 

tanks pass the Coast Guard fire test (33 CFR 183.590) by holding their shape longer under 

exposure to fire. If a flame retardant were included in the epoxy coating, a less expensive 

material, such as HDPE could be used to make fuel tanks that are subject to the flame test 

requirement. The manufacturers who have developed the above approach for permeation have 

developed an additive that provides an intumescent coating to allow the fuel tanks to be 

produced at a lower cost. Testing on the Coast Guard burn test showed that an HDPE fuel tank 

would fail around after being exposed to a flame for about 1.5 minutes (the standard is 2.5 

5-69 
Final Regulatory Impact Analysis 

minutes). With the intumescent coating, the fuel tank passed the flame test and survived more 

than 5 minutes.123 

5.4 Fuel/Vapor Hose Permeation 

The polymeric materials (plastic or rubber) used in the construction of gasoline fuel and 

vapor hoses generally have chemical compositions much like that of gasoline. As a result, 

constant exposure of gasoline to these surfaces allows the material to continually absorb fuel. 

Permeation is driven by the difference in the chemical potentials of gasoline or gasoline vapor on 

either side of the material. The outer surfaces of these materials are exposed to ambient air, so 

the gasoline molecules permeate through these fuel-system components and are emitted directly 

into the air. Permeation emissions continue at a nearly constant rate, regardless of how much the 

vehicle or equipment is used. Because of these effects, permeation-related emissions can 

therefore add up to a large fraction of the total evaporative emissions. 

This section summarizes the data and rationale supporting the permeation emission 

standard for fuel lines presented in the Executive Summary. 

5.4.1 Baseline Hose Technology and Emissions 

5.4.1.1 Marine Fuel Hose Subject to 33 CFR part 183 

The majority of marine fuel hoses are constructed primarily of nitrile rubber with a 

chloroprene cover for abrasion and flame resistance. Hoses are designed to meet the Coast 

Guard requirements in 33 CFR part 183 which reference SAE J1527.124 Fuel hose for boats with 

gasoline engines (excluding outboards) must meet the Class 1, Type A requirements which 

specify a maximum permeation rate of 100 g/m2/day at 23°C on ASTM Reference Fuel C125 (50 

percent toluene, 50 percent iso-octane). Class 1 refers to hose that is used where liquid fuel is 

normally continuously in the hose. Type A refers to hose that will pass a 21⁄2 minute flame 

resistance test. 

On a fuel containing an alcohol blend, permeation would likely be higher from these fuel 

hoses. In fact, the SAE J1527 standard also requires Class 1 hose to meet a permeation rate of 

300 g/m2

/day on fuel CM15 (15 percent methanol). Although ethanol is generally less 

aggressive than methanol, ethanol in the fuel would still be expected to increase the permeation 

rate significantly through most fuel hoses. Based on the data presented in Appendix 5D, 

permeation through nitrile rubber is about 50 percent higher when tested on Fuel CE10 (10 

percent ethanol) compared to testing on Fuel C. 

Fuel fill neck hoses are subject to a less stringent permeation standard under the Coast 

Guard specifications because they are not normally continuously in contact with fuel (Class 2). 

This relaxed standard is 300 g/m2

/day on Fuel C and 600 g/m2/day on Fuel CM15 at 23°C. 

Where marine fuel hose is typically extruded, fill neck hose is generally constructed by wrapped 

layers on a mandrill. Fill neck hose is constructed with a larger inner diameter (1.5-2") to 

accommodate higher fuel rates and with thicker, more heavily reinforced walls, to prevent 

5-70 
Feasibility of Evaporative Emission Control 

buckling and pinching. 

Marine fuel hose is typically designed to be somewhat lower than the SAE J1527 

requirements. Confidential data by one manufacturer supplying baseline marine fuel hose 

suggested that their fuel feed hose is about 25 percent lower than the Class 1, Type A 

requirement on Fuel C and about 35 percent lower on Fuel CM15. In their comments on the 

2002 proposal for marine evaporative emission control, Lawrence industries stated that the 

majority of their fill neck hose permeates in the range of 150 to 180 g/m2/day which is about half 

of the 300 g/m2

/day requirement required by the Coast Guard.126 

We collected test data on marine hose permeation through contracts with outside 

laboratories.127,128,129,130,131 Data was also available on a fuel feed hose testing funded by the 

marine industry.132 All of the hose were prepared by soaking with liquid fuel for long enough 

periods to stabilize the permeation rate. This data is presented in Table 5.4-1. Note that this data 

shows somewhat lower permeation than was reported by manufacturers based on their own 

testing. Especially in the case of the fuel feed hose, this may be a function of the hose 

construction. This hose was purchased by the contractor without any knowledge of the hose 

construction. Therefore, it is not known if this is a representative sample of a baseline hose 

construction or if it contains some sort of barrier material. 

Table 5.4-1: Permeation Rates for Baseline SAE J1527 Marine Fuel Hose 

Hose Type I.D. Fuel Type* g/m2/day Test Temperature 

fuel feed hose 3/8" E10 

Fuel CE10 

43 

88 

23 /C 

vent hose 5/8" E10 37 28 /C 

fill neck hose 1.5" Fuel C 95 

98 

109 

22-36 /C

 temperature cycle 

fill neck hose 1.5" Fuel C 

Fuel CE10 

87 

164 

23 /C 

fill neck hose 1.5" Fuel C 

E10 

Fuel CE10 

123 

123 

274 

23 /C 

* E10 refers to gasoline with 10 percent ethanol 

Although fuel hose used in personal watercraft is subject to 33 CFR part 183, personal 

watercraft manufacturers do not use hose specified in SAE J1527. Fuel hose specifications are 

contained in a separate recommended practice under SAE J2046.133 Under this practice, the 

permeation requirement is 300 g/m2

/day with testing performed in accordance with SAE J1527. 

5-71 
Final Regulatory Impact Analysis 

5.4.1.2 Other Marine Fuel Hose 

Fuel hose used with outboard engines is not subject to 33 CFR part 183. This hose 

includes the fuel line from the portable fuel tank to the engine and fuel hose on the engine itself 

and is generally either constructed out of nitrile rubber with an abrasion resistant cover similar to 

hose used in recreational vehicle applications or is constructed out of polyvinyl chloride (PVC). 

One manufacturer of marine hose for use in outboard marine engines supplied permeation data 

on five hose constructions tested at 23°C.134 This data is presented in Table 5.4-2 for Fuel C, 

Fuel CE10, and Fuel CM15 (15 percent methanol). As shown by this data, hose permeation rates 

can increase dramatically when tested on fuel blended with alcohol. Fuel lines connected to a 

portable fuel tank are also generally fitted with a primer bulb which is also typically constructed 

from nitrile rubber. 

Table 5.4-2: Permeation Rates for Baseline Fuel Hose [g/m2/day at 23°C] 

Fuel Hose Fuel C Fuel CE10 Fuel CM15 gasoline* E10 

C-464-D11 

C-530-D2-CE 

ECO/CPE 

J30R7 

OMC ES1763 

195 

5 

228 

426 

141 

420 

183 

402 

279 

290 

590 

546 

565 

433 

314 

66 

4 

53 

27 

43 

192 

74 

131 

126 

103 

* cited as Marathon 92 

5.4.1.3 Small SI Equipment Hose 

Fuel hoses produced for use in Small SI equipment are generally extruded nitrile rubber 

with a cover for abrasion resistance. This hose is often equivalent to SAE J30 R7 hose which as 

a permeation requirement of 550 g/m2

/day at 23°C135 on ASTM Fuel C (50 percent toluene, 50 

percent iso-octane). On a fuel containing an alcohol blend, permeation would likely be much 

higher for these fuel hoses. R7 hose is made primarily of nitrile rubber (NBR). Based on the 

data presented in Appendix 5D, permeation through NBR is 50 percent higher when tested on 

Fuel CE10 (10 percent ethanol) compared to testing on Fuel C. 

One manufacturer performed a study of several hose samples and various fuel types.136 

Permeation testing was performed using the methodology in SAE J30. These hose samples 

included SAE J30 R7, R8, and R9 hose. The R7 hose samples were constructed with an 

acrylonitrile inner tube with a chlorosulfonated polyethylene cover layer. The R8 hose samples 

were constructed using a epichlorohydrin ethyleneoxide copolymer. The R9 hose used a 

fluoroelastomer barrier for the inner tube with an outer tube made of chlorosulfonated 

polyethylene compound reinforced with a polyester braid. Over the two week tests, the study 

showed a peak permeation rate after 4-6 days for R7 and R8 hose and a peak permeation rate 

after 10-12 days for the lower permeating R9 hose. Table 5.4-3 below presents the two week 

averages for each of the hose samples and test fuels. In this study, the hose manufacturers were 

not identified, but the hose samples were each given a letter designation. 

5-72 
Feasibility of Evaporative Emission Control 

Table 5.4-3: Permeation Rates for SAE J 30 Fuel Hose [g/m2/day at 23°C] 

Fuel Hose Fuel C Fuel CE10 Fuel CE15 Fuel CM15 

SAE J30 R7 “mfr. D” 

SAE J30 R7 “mfr. E” 

450 

330 

508 

501 

541 

433 

587 

707 

SAE J30 R8 “mfr. B” 

SAE J30 R8 “mfr. F” 

152 

130 

385 

355 

337 

308 

620 

545 

SAE J30 R9 “mfr. A” 

SAE J30 R9 “mfr. C” 

2 

2 

11 

6 

10 

4 

73 

55 

Handheld equipment typically use smaller diameter hose made of a single material with 

no cover. This fuel hose may either be extruded straight run hose or may be more complex 

injection-molded designs. To determine baseline permeation emission rates from hose on 

handheld equipment, testing was performed by industry using a modified SAE J30 weight loss 

procedure.137 In this modified procedure, E10 fuel was used and the testing followed a 30 day 

fuel soak intended to stabilize the permeation rate. Further testing was later performed by 

industry on similar fuel lines exposed to E10 and to CE10.138 This testing showed much higher 

permeation on CE10 than on E10 for these hose samples. Table 5.4-4 presents the test results. 

Table 5.4-4: Handheld Product Fuel Line Permeation Test Data [23/C] 

Hose ID Construction Test Fuel Material g/m2/day 

90014 

90015 

90016 

S3 

S4 

H1 

H2 

B1* 

B2* 

extruded E10 NBR 198 

192 

168 

165 

171 

360 

455 

205 

224 

S1 

S2 

C* 

molded E10 NBR 

NBR/PVC 

NBR/PVC 

198 

386 

270 

B1* 

B2* 

extruded CE10 NBR 742 

662 

E* 

F* 

A* 

molded CE10 NBR 

NBR/PVC 

NBR/PVC 

1148 

736 

975 

* average of 5 measurements 

5-73 
Final Regulatory Impact Analysis 

5.4.1.4 Fuel Effects on Hose Permeation 

As shown in the data above, adding ethanol or methanol to the test fuel significantly 

affects the permeation rate through fuel hoses. Because the SAE guidelines typically specify 

Fuel C for testing, most of the hose data available in the literature is on Fuel C or some blend of 

Fuel C and ethanol or methanol. 

One study looked at the effect of fuel composition on the permeation of several materials 

used in baseline hose constructions.139 This data suggests that Fuel C is a more aggressive fuel 

with respect to permeation than gasoline. In addition, this data shows that permeation for these 

materials is very low with diesel fuel. Table 5.4-5 presents the data from this study. Appendix 

5D includes a table spelling out the acronyms for the hose materials in this table. 

Table 5.4-5: Permeation Rates by Fuel and Fuel and Hose Material [g/m2/day at 21°C] 

Material Fuel C CE10 CM10 Indolene* IE10 IM10 Diesel 

CFM 

CO 

ECO 

ETER 

39% ACN NBR 

CSM 

CR 

nil 

150 

190 

230 

300 

490 

640 

35 

270 

390 

400 

420 

575 

690 

nil 

255 

310 

360 

360 

665 

740 

0.1 

10 

55 

65 

110 

210 

320 

20 

80 

180 

205 

200 

240 

340 

nil 

125 

150 

165 

200 

300 

385 

3 

2 

5 

10 

15 

nil 

10 

* “Indolene” refers to a fuel meeting the EPA specifications for certification gasoline 

This difference in permeation between Fuel C and gasoline is likely due to the higher 

aromatic content of Fuel C than of certification gasoline. A second study compared three 

common fuel system materials on Fuel C and certification gasoline.140 Fuel C is made up of 50 

percent toluene and 50 percent isooctane. As a result, it is half aromatics and half aliphatics. In 

this study, the certification gasoline was observed to be 29 percent aromatics, 67 percent 

aliphatics, and 4 percent olefins. The test results were indicative of the effect of aromatics on 

permeation. Table 5.4-6 presents the permeation rate reported in g-mm/m2

/day for three sample 

materials: a low permeation fluoroelastomer (FKM), two medium permeation epichlorohydrins 

(ECO) and two high permeation nitrile rubbers (NBR). This testing, which was performed at 

24/C, gives a good comparison of the effect of gasoline versus Fuel C on permeation. 

5-74 
Feasibility of Evaporative Emission Control 

Table 5.4-6: Fuel C Versus Gasoline Permeation by Hose Material [g-mm/m2/day] 

Material Fuel C Indolene* % difference 

FKM-1 3.3 1.2 -64% 

ECO-1 

ECO-3 

180 

282 

33 

45 

-82% 

-84% 

NBR-1 

NBR-2 

570 

705 

255 

510 

-55% 

-28% 

* “Indolene” refers to a fuel meeting the EPA specifications for certification gasoline 

5.4.1.5 Vent Hose Permeation 

Permeation occurs not only through hose walls that are in contact with liquid gasoline, 

but also through surfaces exposed to fuel vapor. In the event that the fuel vapor represents a 

saturated mix of air and fuel, we would expect permeation to be the same as that for exposure to 

liquid fuel. In a fuel tank, the walls of the tank are readily exposed to saturated vapor as 

discussed earlier in Section 5.3.1.4. In a fuel system hose not continuously exposed to liquid 

fuel, the vapor concentration may be significantly lower than saturation for several reasons. 

Clearly, if a hose is open to atmosphere, such as vent hose, there would be a gradient through the 

hose ranging from saturated vapor in the fuel tank to fresh air outside of the fuel system. In 

addition, if the tank is venting and drawing in air due to diurnal (or other) temperature changes, 

then the fuel hose will regularly be exposed to varying vapor concentrations. 

To investigate permeation rates for vent hose exposed to gasoline vapor, we contracted 

with an outside laboratory to measure the permeation of fuel through marine hoses under various 

venting configurations.141,142 The marine hose used in this testing met the USCG requirements 

for SD/I vessels in specified in 33 CFR part 183 and SAE Recommended Practice J1527. Each 

section of hose was connected to a metal fuel reservoir and exposed to liquid fuel for 8 weeks at 

40°C to stabilize the permeation rate. The test fuel was EPA certification gasoline blended with 

10 percent ethanol (E10) Each section of hose was then soaked for an additional 2 weeks at 

40°C in the planned test configuration. After the soak, fresh fuel was added to the reservoirs and 

permeation was measured in a mini-SHED. Hose sections were tested at constant temperature in 

three configurations. 

One section of hose was tested exposed to liquid fuel. Two sections of hose (1.5 and 5/8" 

I.D.) were tested with one end connected to the fuel reservoir and the other opened to 

atmosphere through a fitting in the SHED. This configuration was intended to simulate vent 

hose at constant temperature. A third configuration was also tested where three sections of hose 

were configured as vent hose and tested over a 22.2-35.6°C one day diurnal sequence. This test 

was intended to simulate vent hose in a fuel system exposed to fuel tank breathing caused by 

temperature variation. The data in this testing, shown in Table 5.4-7, suggest that permeation 

rates for vent lines are much lower than for hose that is regularly exposed to liquid fuel. This 

result is likely due to a fuel concentration gradient in the hose which is largely due to one end 

5-75 
Final Regulatory Impact Analysis 

being exposed to fresh air. 

Table 5.4-7: Effect of Venting on Hose Permeation with E10 [g/m2/day] 

I.D. 

inches 

Length 

feet 

Temperature Liquid Exposure Vented to Atmosphere 

1.5 

0.625 

1 

3 

28°C (84°F) constant 123* 

37 

3.3 

5.8 

0.625 

0.625 

0.625 

3 

3 

3 

22-36°C (72-96°F) diurnal – 

4.3 

4.5 

4.9 

* taken from Table 5.4-1 on a similar hose for comparison 

The marine industry also funded permeation testing on vent hose exposed only to fuel 

vapor and air.143 The vent line hose was preconditioned by attaching the hose to a 55 gallon steel 

drum containing commercial gasoline containing 10 percent ethanol and setting the drum outside 

during the summer. A carbon canister was attached to the end of the hose to simulate a vent line 

with diurnal emission control. Permeation was measured after 90, 120, 150, and 180 days of 

preconditioning. Because of the large size of the test rig, weight loss testing could not be 

performed. Instead, a sleeve was fitted over the hose and nitrogen was flowed through the sleeve 

to a carbon trap. The change in the weight of the carbon trap was then measured to determine 

the permeation rate. As with the fill neck testing, the hose was configured to run vertically from 

the top of the fuel reservoir (55 gallon drum). Repeat testing was performed on this hose and 

both values for each hose are presented in Table 5.4-8. The permeation rates for this testing 

were lower than for similar hose exposed to liquid fuel. Fuel vapor stratification may have been 

caused by a number of factors including breathing of fresh air into the tank during ambient 

cooling periods, gravity, and a limiting diffusion rate. 

Table 5.4-8: Industry Test Data on Marine Vent Hose Exposed to Fuel Vapor 

Hose manufacturer Permeation [g/m2/day] 

#1 2.7, 2.2 

2.7, 2.8 

8.9, 8.5 

5.7, 6.6 

#2 2.2, 2.0 

2.5, 2.2 

2.5, 2.6 

5-76 
Feasibility of Evaporative Emission Control 

5.4.1.6 Vapor Hose Permeation 

Even in a vapor hose that is sealed at one end, stratification may occur for a fuel system 

due to gravity. An example of vapor hose would be fuel fill neck hose with a sealed cap. 

Because fuel vapor is heavier than air, even a large diameter hose may see stratification of fuel 

vapor concentration if it reaches high enough above the surface of the liquid fuel. The 

stratification of vapor molecules happens slowly but would likely be observed under static 

conditions. Another cause of low vapor concentration in fuel system hose may occur due to the 

properties of diffusion discussed above in Section 5.1.3. If the hose diameter is small compared 

to its length, diffusion of vapor into the hose may be the rate limiting step rather than the 

permeation rate through the hose. In other words, the fuel vapor may enter the hose much slower 

than rate at which it could permeate through the hose. This effect could be combined with the 

other effects discussed above to cause lower permeation for fuel hose exposed to vapor rather 

than liquid fuel. 

The marine industry funded permeation testing on fill neck exposed only to fuel vapor.144 

For the fill neck hose, a three foot section of hose was attached to the top of a five gallon metal 

fuel reservoir and configured vertically. The fuel reservoir was filled half-way with gasoline 

containing 10 percent ethanol. Approximately every 30 days, this hose/reservoir assembly was 

weighed for five days in a row. After the fifth day, the fuel in the reservoir was replaced with 

fresh fuel. Testing was performed at 23/C. The only liquid fuel exposure was a weekly 

inversion of the assembly for about 1 minute. No attempt was made to simulate fuel slosh that 

would be likely be seen in a boat in the water. Also the hose was configured straight up and 

down rather than in a more representative configuration as seen on a boat that would include 

more horizontal orientation for most of the length of the hose. Repeat testing was performed on 

the hose.145 During this repeat testing, permeation was also measured for the same fill neck hose 

exposed to liquid fuel. 

Four of the fill neck hose constructions were specified as meeting the A2 designation in 

SAE J1527. The other two fill neck hose samples were not identified except that they are made 

by a hose manufacturer that is known to offer fill neck hose with and without a fluoroelastomer 

barrier. Table 5.4-9 presents the test results which show much lower permeation rates for fill 

neck hose exposed vapor rather than liquid fuel. Because the end of the hose was not exposed to 

atmosphere, and because the hose was situated well above the surface of the liquid fuel in a 

vertical fashion, stratification may have occurred in the hose largely due to gravity. This 

stratification would be expected to lower the vapor concentration in the hose and therefore lower 

permeation. 

5-77 
Final Regulatory Impact Analysis 

Table 5.4-9: Industry Permeation Data on Marine Fill Neck Hose [g/m2/day] 

Hose manufacturer Vapor Exposure Liquid Exposure 

#1 4.8, 4.8 

4.5, 4.4 

4.7, 4.8 

4.7, 4.7 

129 

114 

113 

121 

#2 1.3, 1.1 

0.6, 6.9 

5.6 

8.5 

The marine industry testing was all performed on static test rigs with vertically oriented 

hose. No consideration was given to how sloshing the test configuration, as would be seen in a 

boat in the water, would have affected the results. For in-use equipment, especially boats in the 

water, the fuel is sloshed regularly due to operation or waves. This sloshing may mix up the 

vapor in the tank and hose. The industry test program also did not consider how a different hose 

configuration (i.e. more horizontally oriented) would have affected the results. Fill neck hose in 

boats often runs nearly horizontal from the tank to the edge of the boat, then runs more vertically 

near the fill port. 

We contracted with an outside test lab to Figure 5.4-1: Hose Test Configurations 

investigate the effects of fuel slosh and hose 

configuration on permeation through marine fill 

neck hose.146 All of the testing was performed Liquid 

on 3 foot sections of 1.5" I.D. marine fill neck 

hose. Testing was performed in each of the Vertical 

three configurations shown in Figure 5.4-1. For 

each fuel vapor exposure test, the hose was first 

preconditioned by subjecting it to liquid fuel for 

5 weeks followed by fuel vapor for an 

additional 5 weeks. For the liquid fuel exposure Horizontal 

tests, the hose was soaked with liquid fuel for 

10 weeks. Fuel soaking was performed at 40/C. 

A total of eleven tests were run. For each configuration, testing was performed on three 

fuels: Fuel C, CE10, and E10. The liquid fuel exposure tests were performed in the static 

position, while the fuel vapor exposure tests were performed with the fuel tanks on a slosh table. 

Sloshing was performed at 15 cycles per minute with a deviation of +7/ to -7/ from level to 

simulate movement that might be seen on a boat. An additional two tests were performed to 

measure permeation through vapor hose in the vertical and horizontal positions without sloshing. 

Permeation was measured similar to the industry testing using weight loss measurements of the 

entire test rigs at 23/C. 

The test results from this testing are presented in Table 5.4-10. It was observed that 

permeation was much lower for vapor fuel exposure than for liquid fuel exposure. Fuel 

5-78 
Feasibility of Evaporative Emission Control 

permeation was significantly higher for the horizontal hose configuration than for the vertical 

hose configuration. This suggests that a large amount vapor stratification was occurring for the 

vertical hose, while some fuel vapor was collecting in the horizontal hose. The fuel sloshing 

applied in this testing doubled the permeation through the horizontal hose. Regardless of fuel 

slosh, no measurable permeation was observed through the vertically oriented hose. Permeation 

emissions were observed to be about twice as high on fuel CE10 than on Fuel C or E10. 

Table 5.4-10: Effect of Hose Configuration, Vapor Exposure, 

and Test Fuel on Marine Fill Neck Hose Permeation at 23/C 

Hose Configuration Vapor Exposure Test Fuel Permeation [g/m2/day] 

horizontal 

stationary 

sloshed 

sloshed 

sloshed 

CE10 

CE10 

E10 

Fuel C 

4.6 

9.1 

4.6 

9.1 

vertical 

stationary 

sloshed 

sloshed 

sloshed 

CE10 

CE10 

E10 

Fuel C 

0.0 

0.0 

0.0 

0.0 

liquid soak 

CE10 

E10 

Fuel C 

273.7 

123.2 

123.2 

In another study, the effects of liquid fuel versus vapor were studied in which the vapor 

hose was not open to atmosphere.147 The fuel hose used for this testing was purchased over the 

counter and was labeled as SAE J30 R7. Further investigation of the hose revealed that this 

particular grade is made of lower permeation materials than typical Small SI hose constructions. 

It was constructed of NBR with a relatively high ACN blend (39 percent) and an ECO cover was 

used. This construction was originally intended to allow the hose to be painted with a lacquerbased paint, then dried in an oven. Although this is a somewhat atypical hose construction, the 

test results should still reflect the effects of liquid versus vapor on permeation. 

In this testing, all of the fuel hose was preconditioned by soaking in liquid fuel for 5 

weeks at about 40/C. This soak was then repeated, except that half of the hose sections were 

then exposed only to fuel vapor resulting from attaching the hose to the top of a metal fuel 

reservoir. Three fuels were used; California certification gasoline (CARB II), EPA certification 

gasoline (gasoline), and EPA gasoline blended with 10 percent ethanol (E10). After the soak 

period, the fuel was refreshed and weight loss testing was performed at 23/C. Table 5.4-11 

presents the test results. Note that each data point in this table is the average of three hose 

samples. In this testing, the end of the hose was plugged and the hose was configured 

horizontally. The lower permeation rates for vapor exposure were likely the result a low vapor 

concentration in the hose. This low vapor concentration may have been caused because the 

diffusion into the long narrow hose may have been the rate limiting effect rather than the 

5-79 
Final Regulatory Impact Analysis 

permeation rate through the hose. 

Table 5.4-11: Fuel Hose Permeation with Vapor vs. Liquid Exposure [g/m2/day] 

Test Fuel Liquid Exposure Vapor Exposure 

CARB II 35.8 0.3 

Gasoline 44.5 0.1 

E10 80.3 0.7 

5.4.2 Hose Permeation Reduction Technologies 

Materials used in current automotive fuel lines are two to three orders of magnitude less 

permeable than nitrile hoses.148 In automotive applications, multilayer plastic tubing, made of 

fluoropolymers is generally used. An added benefit of these low permeability lines is that some 

fluoropolymers can be made to conduct electricity and therefore can prevent the buildup of static 

charges.149 Although this technology can achieve more than an order of magnitude lower 

permeation than barrier hoses, it is relatively inflexible and may need to be molded in specific 

shapes for each Small SI application. For marine applications, this tubing would not likely meet 

the Coast Guard or ABYC durability specifications for fuel and vent hose. 

Thermoplastic fuel lines for automotive applications are generally built to SAE J2260 

specifications.150 Category 1 fuel lines under this specification have permeation rates of less than 

25 g/m2/day at 60°C on CM15 fuel (15 percent methanol). One thermoplastic used in 

automotive fuel line construction is polyvinylidene fluoride (PVDF). Based on the data 

presented in Appendix 5D, a PDVF fuel line with a typical wall thickness (1 mm) would have a 

permeation rate of 0.2 g/m2/day at 23°C on CM15 fuel. However, manufacturers involved in the 

boat building industry have commented that this fuel line would not be flexible enough to use in 

their applications because they require flexible rubber hose to fit tight radii and to resist 

vibration. They also commented that the hose they use must pass the Coast Guard flame 

resistance requirements.151,152 

Recreational vehicle manufacturers are required to use hose that meets a permeation 

standard of 15 g/m2

/day at 23°C on gasoline blended with 10 percent ethanol (E10). Low 

permeation hose constructions that have been identified for these applications could also be used 

in Small SI equipment. We believe that the same barrier materials that will be used for 

recreational vehicle hose can also be used for marine hose constructions. Marine hose 

constructions generally meet the Coast Guard flame resistance requirements either through the 

use of a flame-resistant cover, or by increasing the wall thickness. Therefore, the addition of an 

inner permeation barrier would not be expected to affect the flame resistance of the hose. 

Several low permeation hose constructions are discussed below. Even though most of this data 

is on hoses not designed for marine applications, the barrier technology can be used in marine 

hose. 

5-80 
Feasibility of Evaporative Emission Control 

We are requiring that fuel and vapor hose meet our standards on E10 fuel for two 

reasons. First, ethanol is commonly a component of in-use fuels. Second, for many materials 

used in hose constructions, permeation would likely be much higher for fuel containing ethanol. 

For instance, a typical barrier material used in barrier hose constructions is FKM. Based on the 

data presented in Appendix 5D for FKM, the permeation rate is 3-5 times higher on Fuel CE10 

than Fuel C. Therefore, a hose meeting 15 g/m2/day at 23°C on Fuel C may actually permeate at 

a level of 40-50 g/m2

/day on fuel with a 10 percent ethanol blend. 

There are lower permeation fuel hoses available today that are manufactured for 

automotive applications. These hoses are generally used either as vapor hoses or as short 

sections of fuel line to provide flexibility and absorb vibration. One example of such a hose153 is 

labeled by General Motors as “construction 6" which is a multilayer hose with an inner layer of a 

fluoroplastic known as THV sandwiched in inner and outer layers of a rubber known as ECO.5 

A hose of this construction would have less than 8 g/m2

/day at 40°C when tested on CE10. 

Permeation data on several low permeation hose designs were provided to EPA by an 

automotive fuel hose manufacturer.154 This hose, which is as flexible as non-barrier hose, was 

designed for automotive applications and is available today. Table 5.4-12 presents permeation 

data on three hose designs that use THV 800 as the barrier layer. The difference in the three 

designs is the material used on the inner layer of the hose. This material does not significantly 

affect permeation emissions through the hose but can affect leakage at the plug during testing (or 

connector in use) and fuel that passes out of the end of the hose which is known as wicking. The 

permeation testing was performed using the ARB 18-41°C diurnal cycle using a fuel with a 10 

percent ethanol blend (E10). 

Table 5.4-12: Hose Permeation Rates with THV 800 Barrier over ARB Cycle (g/m2/day) 

Hose Name Inner Layer Permeation Wicking Leaking Total 

CADBAR 9610 THV 0.16 0.00 0.02 0.18 

CADBAR 9710 NBR 0.17 0.29 0.01 0.47 

CADBAR 9510 FKM 0.16 0.01 0.00 0.18 

The data presented above shows that there is hose available that can easily meet the hose 

permeation standard on CE10 fuel. Although hose using THV 800 is available, it is produced for 

automobiles that must meet the tighter evaporative emission requirements in the Tier 2 

standards. Hose produced in mass quantities today uses THV 500. This hose is less expensive 

and could be used to meet the hose permeation requirements. Table 5.4-13 presents information 

comparing hose using THV 500 with the hose described above using THV 800 as a barrier 

layer.155 In addition, this data shows that permeation rates more than double when tested on 

CE10 versus Fuel C. 

5 THV = tetrafluoroethylene hexafluoropropylene, ECO = epichlorohydrin/ethylene oxide 

5-81 
Final Regulatory Impact Analysis 

Table 5.4-13: Comparison of Hose Permeation Rates with THV 500 and 800 (g/m2/day)* 

Hose Inner 

Diameter, mm 

THV 500 THV 800 

Fuel C Fuel CE10 Fuel C Fuel CE10 

6 0.5 1.4 0.2 0.5 

8 0.5 1.4 0.3 0.5 

10 0.5 1.5 0.2 0.5 

* Calculated using data from Thwing Albert materials testing (may overstate permeation) 

We contracted with an independent testing laboratory to test several samples of SAE J30 

R9 hose and a sample each of automotive vent line and fill neck hose for 

permeation.156,157,158,159,160,161 The fuel and vapor hoses had a six mm inner diameter. The test lab 

used the SAE J30 test procedures for R9 hose with both Fuel C and Fuel CE10. Most of the R9 

fuel hose was supplied by recreational vehicle manufacturers who also supplied information on 

the materials used in the construction of the hose as well. We purchased one sample of the R9 

hose (which was labeled as such) from a local auto parts store without knowing its construction. 

Two additional R9 hoses were tested by a fuel hose manufacturer on fuel CE10 after a four week 

soak.162 The SAE permeation specification for R9 hose is 15 g/m2

/day at 23/C on Fuel C. The 

R9 hose tested all met this limit, even on ethanol blend fuels which typically result in higher 

permeation. The automotive vent line showed similar results, but the automotive fill neck 

showed much lower permeation. Table 5.4-14 presents the test data on the above hose samples. 

5-82 
Feasibility of Evaporative Emission Control 

Table 5.4-14: Test Results on Commercially Available Hose Samples (g/m2/day) 

Hose Sample Construction Fuel C Fuel CE10 

SAE J30 R9 FKM/ECO – 7.6 

SAE J30 R9 FKM/ECO – 2.1 

SAE J30 R9 FKM/NBR/CM – 4.2 

SAE J30 R9 FKM/ECO – 10.9 

SAE J30 R9 FKM/ECO – 5.2 

SAE J30 R9 PVC/EEC – 11.6 

SAE J30 R9 FKM barrier – 6.6 

SAE J30 R9 fluorine/hydrin – 9.0 

SAE J30 R9 unknown 10.1 12.1 

SAE J30 R9 FKM barrier – 4.2 

SAE J30 R9 FKM barrier – 6.7 

Automotive vent line unknown 10.9 9.0 

Automotive fill neck unknown 0.33 0.49 

Another hose construction that can be used to meet the marine hose permeation standards 

is known as F200 which uses Teflon® as a barrier layer. Teflon® has a permeation rate of 0.03-

0.05 g-mm/m2

/day on 15 percent methanol fuel. F200 hose is used today to meet SAE J30 R11 

and R12 requirements for automotive applications. Table 5.4-15 presents data on permeation 

rates for several F200 constructions.163 

Table 5.4-15: F200 Typical Fuel Permeation 

Film Thickness [mils] Hose Diameter [in.] Fuel g/m2/day @23°C g/m2/day @40°C 

2 0.375 TF-2 -- 0.7 

2 0.275 TF-2 -- 1 

2 0.275 M25 0.5 4 

2 0.470 CE10 -- 3 

2 0.625 CE10 -- 3 

1 0.625 CE10 -- 4 

1 1.5 CE10 1.5 --

Low permeability hoses produced today are generally constructed with a barrier material 

5-83 
Final Regulatory Impact Analysis 

layer. There are hoses used in some marine applications with a thermoplastic layer (either nylon 

or EVOH) between two rubber layers to control permeation. Because the thermoplastic layer is 

very thin, on the order of 0.1 to 0.2 mm, the rubber hose retains its flexibility. Through contract 

with two independent labs, we tested three samples of marine barrier hose that were available 

prior to our 2002 proposal for marine permeation emissions. This hose included two 3/8" 

samples and one 5/8" sample which all used nylon as the permeation barrier. These hose 

constructions are used in some sterndrive and inboard applications. Table 5.4-16 presents the 

permeation test results at 23°C.164,165,166,167,168,169 

Table 5.4-16: Test Results on Available Barrier Marine Hose Samples (g/m2/day) 

Hose Description 

Lab 1 Lab 2* 

Fuel C Fuel CE10 Fuel C 

3/8" marine barrier fuel hose 0.80 

--

5.2 

11.6 

0.36 

--

5/8" marine barrier fuel hose -- 3.4 0.76 

* average of three tests 

Similar testing was performed by the marine industry on commercially available low 

permeation marine hose.170 In this testing, the 3/8" I.D. fuel hose samples were connected to 

metal fuel reservoirs and soaked with gasoline containing 10 percent ethanol at 23/C for 180 

days. The weight of the container/hose assembly was measured for five days in a row 

approximately every 30 days. The fuel was replaced with fresh fuel after each series of weight 

measurements. The test report did not specify details on the hose constructions. However, based 

on the manufacturer part numbers, several of the hoses in this test program were determined to 

use a nylon barrier layer. One of the hoses included was a baseline rubber construction meeting 

Coast Guard requirements for SD/I fuel hose. Repeat testing was performed on the hose.171 

During this repeat testing, permeation was also measured for the same hose exposed to fuel 

CE10. Although the permeation rate was generally higher on fuel CE10, the barrier hose 

permeation rates were still well below the standard. Table 5.4-17 presents the results of this 

testing. 

Table 5.4-17: Permeation Results for Commercially Available Marine Barrier Hose

 Tested at 23/C with Gasoline Containing 10% Ethanol (g/m2

/day) 

Hose Construction Gasoline with 10% Ethanol CE10 

SAE J1527 A1 constructions with nylon barrier 6.2, 5.2 

5.6, 5.1 

4.4, 3.8 

4.4, 3.2 

6.1 

6.7 

10.0 

12.1 

not reported 0.4, 0.1 0.0 

5-84 
Feasibility of Evaporative Emission Control 

After the 2002 proposal for marine permeation emissions, two marine hose manufacturers 

developed hose samples using the F200 hose construction. In addition, other hose manufacturers 

supplied samples of barrier hose using the F200 hose construction and using THV800 as a 

barrier layer. These manufacturers stated that they could make marine hose using the same 

barrier construction. We contracted to have these hose samples permeation tested on fuel CE10 

at 23°C following a four week soak.172 These test results are presented in Table 5.4-18. 

Table 5.4-18: Permeation Test Results on New Marine Barrier Hose Constructions 

Application Barrier Material I.D. [inches] g/m2/day 

marine fill neck Teflon (F200) 11⁄2 0.2 

marine fuel hose Teflon (F200) 3/8 5.0 

fuel hose Teflon (F200) 1/4 3.8 

fuel hose THV 800 1/4 5.1 

Currently, the Coast Guard requires that fuel pumps on engines be located on or near the 

engine to minimize the length of high pressure fuel lines on the vessel. However, at least one 

manufacturer sells boats with the high pressure fuel pump in the fuel tank. They received a 

waiver from the Coast Guard by using fuel lines that use either a glass fiber or stainless steel 

braid cover and quick connect end fittings that are designed to withstand very high pressures 

(much higher than would be seen on a boat).173 This particular fuel line construction also uses 

Teflon® as a barrier layer. Table 5.4-19 presents permeation test data on this hose.174 

Table 5.4-19: Permeation Test Data on Reinforced Fuel Hose 

Application I.D. [inches] Temperature Fuel g/m2/day 

Marine 0.31 

0.25 

0.19 

23°C CE10 0.05 

0.08 

0.05 

Outdoor Power 

Equipment 

0.31 

0.25 

0.19 

60°C CM15 0.52 

0.93 

1.08 

Primer bulbs are typically injection-molded out of nitrile rubber. Fuel lines for some 

handheld equipment are manufactured in a similar manner. Low permeation primer bulbs and 

fuel lines could be manufactured using a similar process by molding them from a 

fluoroelastomer such as FKM. Fluoroelastomers, such as FKM, have similar physical properties 

as nitrile rubber but are much more fuel-resistant. If the primer bulb or fuel line were molded 

out of a FKM with a sufficient flurorine concentration, the permeation rate would be less than 

fuel line permeation standard. Alternatively, primer bulbs could be manufactured to meet the 

standards by molding a fluoroelastomer inner liner with a nitrile shell to reduce costs. Other 

5-85 
Final Regulatory Impact Analysis 

materials may be applicable as well (see tables of material properties in Appendix 5D). 

One manufacturer has developed a low-permeation primer bulb replacement that meets 

the hose permeation standard.175,176 This design uses a rigid, low permeation housing in the 

shape of a traditional primer bulb. However, it uses a simple piston displacement pump inside to 

take the place of soft elastomer squeeze type bulb. It is designed to have similar dimensions to 

existing primer bulbs and to be easily retrofitted into current applications. 

Under their rule for small offroad equipment, California may issue executive orders to 

manufacturers with low emission products. As of August, 2006, ARB has issued 24 executive 

orders for low permeation fuel lines.177 The California fuel line permeation standard is 15 

g/m2/day tested at 40/C on California certification fuel. However, many of the manufacturers 

tested their products on CE10 fuel which results in significantly higher permeation rates. Some 

manufacturers even tested at 60/C. In all cases, the test results were below the 15 g/m2

/day 

standard, even under the more challenging test conditions. Table 5.4-20 presents the test results 

for the fuel lines with ARB executive orders. Note that the reported emissions are the average of 

5-6 test samples. 

5-86 
Feasibility of Evaporative Emission Control 

Table 5.4-20: ARB Fuel Hose Executive Orders for Small Offroad Equipment 

EO# I.D. [mm] Test Fuel Temperature g/m2

/day 

C-U-06-016 

C-U-06-001 

G-05-016 

G-05-017 

G-05-019 

C-U-05-004 

C-U-05-010 

4.8 

6.0 

6.4 

6.4 

6.4 

6.4 

6.4 

CE10 

CE10 

CE10 

CE10 

CE10 

CE10 

CE10 

40 

40 

40 

40 

40 

40 

40 

3.75 

1.42 

4.62 

5.97 

0.02 

12.3 

10.6 

G-05-019* 

G-05-015a 

C-U-05-001 

6.4 

7.9 

8.0 

CE10 

CE10 

CE10 

60 

60 

60 

0.26 

11.1 

8.22 

C-U-06-001* 6.0 CM15 40 3.77 

C-U-06-001* 6.0 Fuel C 40 0.78 

C-U-06-020 

C-U-05-014 

C-U-06-021 

C-U-06-002 

C-U-06-011 

4.5 

6.4 

6.4 

6.4 

6.4 

Indolene 

Indolene 

Indolene 

Indolene 

Indolene 

40 

40 

40 

40 

40 

3.20 

8.20 

7.40 

5.00 

12.7 

C-U-05-011 

C-U-06-017 

C-U-05-013 

C-U-05-006 

C-U-05-012 

C-U-05-003 

G-05-018 

C-U-05-009 

C-U-06-010 

C-U-05-002 

2.0 

3.5 

4.0 

4.0 

4.0 

4.5 

4.8 

4.8 

4.8 

6.4 

Phase II 

Phase II 

Phase II 

Phase II 

Phase II 

Phase II 

Phase II 

Phase II 

Phase II 

Phase II 

40 

40 

40 

40 

40 

40 

40 

40 

40 

40 

4.63 

10.8 

1.22 

10.3 

7.33 

12.3 

0.87 

3.94 

4.69 

3.76 

* fuel tube 

5.4.3 Low Temperature Hose Materials 

In some applications, molded fuel hoses are used rather than simple extruded fuel hose. 

These fuel hoses are typically molded out of nitrile rubber (NBR) or a fluoroelastomer such as 

FKM. FKM is essentially rubber impregnated with fluorine which results in good fuel 

permeation resistance. Manufacturers of handheld equipment that may be used in very cold 

weather have stated that they must use nitrile rubber because the FKM material may become 

brittle at very low temperatures.178 Examples of such equipment are ice augers and chainsaws. 

5-87 
Final Regulatory Impact Analysis 

Industry has not raised an issue with the capability of using extruded multi-layer hose in 

cold temperature applications. This type of hose construction has been demonstrated for low 

temperature use in automobiles and snowmobiles. Extruded fuel hose meeting SAE and ASTM 

standards is available today which meets a widespread set of safety and durability requirements. 

Industry has stated that for some applications, such as chainsaws, that extruded fuel hose will not 

work. In these applications, injection molding is used to manufacture complex fuel hose 

geometries designed to account for high vibration of the equipment. This vibration generally 

results in different motion patterns for the carburetor and fuel tank resulting in variable distances 

between the two. 

Industry presented information on FKM fuel lines that became brittle and cracked at very 

low temperatures.179,180 However, this information was was based on an FKM compound without 

a low temperature additive package. There are a wide range of FKM products available on the 

market. Many of these fluoroelastomers are designed for use at low temperatures.181,182 For 

instance, low temperature o-rings are common in automotive applications.183,184,185 Low 

temperature grade FKM products are available with a glass transition temperature as low as -

40/C and a brittleness point as low as -60/C.186 However, low temperature grade FKM products 

typically cost several times as much as FKM products intended for less severe temperatures. In 

addition, these materials have not been demonstrated for use in molded fuel lines for handheld 

applications. 

A lower cost option may be to blend a standard fluorosilicone such as FVMQ with a 

standard grade FKM. The fluorosilicone brings very low temperature characteristics to the 

blend. However, the permeation resistance is not nearly as good as for FKM products. The 

blended product would be intended to create a balance between cost, permeation, and low 

temperature properties.187 This product is currently used in automotive o-rings. However, it is 

not clear if this material could be molded into fuel lines that would meet the appropriate design 

criteria for handheld applications. 

A new material, called F-TPV, has been developed that is a dynamically vulcanized 

combination of fluorothermoplastic resin and fluoroelastomer compound.188 The mix of the two 

materials can be varied to trade-off permeation resistance with material hardness. This material 

has been shown to have a permeation rate ranging from 3 to 30 g-mm/m2

/day on fuel CE10 at 

60/C. Rubber hose molded out of even the softest version of this material would be expected to 

be capable of achieving a permeation rate well below the standard. In addition, the impact 

brittleness temperature is below -50/C for the full range of material blends discussed above. 

Finally, the cost of this material is much lower than for low-temperature FKM products. Further 

development efforts would be necessary to determine the suitability of this material for fuel lines 

on handheld equipment. 

Table 5.4-4, above, presents permeation data on several samples of NBR fuel lines used 

on handheld equipment today. The permeation rates from these fuel lines range from 165 to 455 

g/m2

/day with E10 fuel at 23/C. Later discussions with industry revealed that the NBR hose 

with the lower permeation rates had higher acrylonitrile (ACN) contents. Although high ACN 

rubber cannot achieve the same low permeation rates as FKM or F-TPV, some permeation 

5-88 
Feasibility of Evaporative Emission Control 

reductions could still be achieved with this material. 

5.5 Other Evaporative Emissions 

5.5.1 Other Venting Losses 

Hot soak emissions occur after the engine is turned off, especially during the resulting 

temperature rise. The primary source of hot soak emissions is the evaporation of the fuel left in 

the carburetor bowl. Other sources can include increased permeation and evaporation of fuel 

from plastic or rubber fuel lines in the engine compartment. 

Refueling emissions occur when the fuel vapors are forced out when the tank is filled 

with liquid fuel. At a given temperature, refueling emissions are proportional to the volume of 

the fuel dispensed into the tank. Every gallon of fuel put into the tank forces out one-gallon of 

the mixture of air and fuel vapors. Thus, refueling emissions are highest when the tank is near 

empty. Refueling emissions are also affected by the temperature of the fuel vapors and 

dispensed fuel. At low dispensed fuel temperatures, the fuel vapor content of the vapor space 

that is replaced is lower than it is at higher temperatures because of the cooling effect on the 

vapor in the fuel tank. 

In automotive applications, the carbon canister is sized not only to capture diurnal 

emissions, but refueling, hot soak, and running loss emissions as well. With an engine purge, the 

canister would effectively capture running loss emissions and hot soak emissions because the 

canister would presumably be nearly empty after a short period of operation. For the canister to 

be effective at collecting refueling emissions, it would need to be purged before the refueling 

event. However, even without a purged canister, refueling emissions could be minimized by 

matching the geometry of the fuel fill opening to the fuel pump nozzle. By minimizing the open 

space in the fuel fill opening around the nozzle, less air will be entrained which will minimize 

vapor generation during the refueling event. This will not help control the expulsion of vapor 

that is displaced by liquid fuel. 

5.5.2 Refueling Spitback/Spillage 

Installed fuel systems on boats are typically open vented. The exception to this is PWC 

which have sealed fuel tanks with pressure relief valves, largely to prevent spillage of fuel during 

operation. For larger boats, fuel spillage during operation is less of an issue; however, it is 

common for fuel to be lost to the environment during refueling or shortly thereafter.189,190 There 

are several mechanisms that lead to fuel loss due to a refueling event. These mechanisms 

include restrictions in the fill neck, fuel flowing out the vent line, and expansion of fuel in the 

tank. 

The American Boat and Yacht Council (ABYC) has a voluntary refueling standard 

designed to help prevent fuel from backing up the fill neck during a refueling event.191 This test 

requires that no fuel back up the fill neck when a fuel tank in a boat is filled from 25 to 75 

percent full at a fill rate of 9 gallons per minute. This test is apparently designed to make sure 

5-89 
Final Regulatory Impact Analysis 

that the fill neck does not have a restriction that may cause fuel to back up the fill neck during 

refueling. To prevent fill from backing up the fill neck, fill necks are typically made of large 

diameter hose which is reinforced to prevent kinking. In addition, the fuel fill opening is 

typically positioned higher than the vent line. This test does not consider fuel overflow that may 

occur from filling a marine tank to 100 percent full. In addition, the full rate may be too low to 

require a design that would work in typical in-use situations. One survey on 19 marinas saw a 

range of 8 to 25 gallons per minute for gasoline fill nozzles with an average of 14 gallons per 

minute.192 

The most common refueling spillage today is overflow out the vent line. Typically the 

vent line is the path of least resistance for fuel overflow. Boats typically do not have a 

mechanism that prevents fuel tanks from filling all the way to the top. In fact, the fill and vent 

hose are attached to the top of the fuel tank and are often filled with fuel in addition to the tank. 

Because the vent hose exits the boat lower than the fill neck opening, the tank can be filled until 

fuel begins to exit through the vent hose. In addition, fuel may expand in the fuel tank when 

cool fuel is pumped into the fuel tank on a warm day. This expansion can cause additional fuel 

overflow out the vent line. 

A number of devices have been produced to help control fuel spillage during refueling. 

These devices include liquid/vapor separators, combination deck fills and vents, and fuel flow 

monitoring systems. A study was performed by Boat US Foundation to evaluate the 

effectiveness of several of these systems which are currently available on the market.193 The 

results of this study are discussed below. 

Liquid/vapor separators are valves that are installed in the fuel line. The typical design is 

for the valve to contain a ball that rises when liquid fuel reaches it which closes the vent to liquid 

fuel. As the tank fills, fuel backs up the fill neck, allowing the automatic shut-off on the nozzle 

to stop the fuel flow. The study found that these systems typically worked best at lower fuel fill 

rates and that the larger units were more effective. The effectiveness of the larger units was 

probably because they essentially included a reservoir, allowing extra room for fuel expansion. 

For the smaller units, the testing consistently showed fuel backing up the fill neck too quickly for 

the automatic shut-off valve to engage and fuel spit back out of the deck fill. 

In a vented deck fill design, the vent line is routed back to the top of the fill neck. The 

intent is that the fuel surging out of the vent line would return to the fill neck and back to the 

tank. The study found that the combination vented deck fills significantly reduced 

spitback/spillage, but still needed to be used with some caution. One issue was that even when 

the fuel came back up and shut off the nozzle, pressure in the fuel tank would cause fuel to 

continue to rise in the line and spill onto the deck. Another manufacturer has a similar device 

except that a clear section of tubing that redirects the fuel overflow from the vent line to the fill 

neck. The operator only attaches this tubing during refueling. Because the tubing is clear, the 

operator can see when the fuel is coming out of the vent and can manually slow down or stop the 

fuel flow. 

Fuel flow monitoring systems are designed to keep track of fuel usage by measuring fuel 

5-90 
Feasibility of Evaporative Emission Control 

flowing to the engine. The study did not present definitive results for the use of flow meters to 

accurately refuel the tank without overfill. 

Where a carbon canister is used in the vent line for diurnal vapor control, it is important 

to include a device to prevent liquid fuel from entering the canister. This device could take the 

form of a floating ball valve, limited flow orifice, or other liquid/vapor separation mechanism. 

In addition, this device could be positioned in such a way as to prevent the tank from filling all 

the way to the top. For instance, the vent fitting could reach down into the fuel tank. Leaving a 

vapor space in the fuel tank gives room for fuel in the tank to expand. 

In automotive applications, carbon canisters have been used for many years in vehicles 

that also meet fuel spit-back standards set by EPA. In typical automotive fuel systems, the fuel 

shut-off on the nozzle is tripped before the fuel comes back out the fill neck. It is common to 

have a narrow tube parallel to the fill neck reach into the fuel tank at the desired peak fill level of 

the tank. The narrow tube connects to the fill neck near the top where the small hole on the 

nozzle would be. When fuel splashes on this small hole, the vacuum draw is broken and the 

shut-off device is triggered. Fuel travels up the narrow tube more quickly than up the fill neck 

and triggers the nozzle shut-off well before fuel spit-back can occur. 

At least one company is developing a similar design for use in boats. Testing has been 

performed on one system by an independent laboratory that also performs ABYC and Coast 

Guard tests for the marine industry. During the testing, a fuel tank was filled 30,000 times, using 

this fuel system configuration, without any spillage.194 Also, this fuel system configuration 

creates a vapor space in the top of the tank which allows fuel to expand during heating, thereby 

preventing fuel spillage due to expansion of the fuel in the tank.195 This system has since been 

modified to be adaptable to any fuel tank with a fuel sending unit based on the standard SAE 5-

hole pattern. The updated system was tested using a similar methodology as in the Boat US 

study discussed above and underwent 25,000 refueling events at 15 gallons per minute without 

experiencing any spills.196 Pictures and video of this system are included in the docket. 

5.6 Evaporative Emission Test Procedures 

This section discusses test procedures for measuring fuel line permeation, fuel tank 

permeation, and diurnal emissions. 

5.6.1 Fuel line Permeation Testing 

Fuel line permeation must be measured at a temperature of 23 ± 2°C using the weight 

loss method specified in SAE J30197 and SAE J1527.198 In this method, one end of a specified 

length of hose is connected to a metal reservoir while the other end is plugged. Test fuel is then 

added to the reservoir at a volume high enough to ensure that the hose is filled with fuel. Once 

care has been taken to ensure that no air bubbles are trapped in the fuel line, the reservoir is 

sealed and the entire system is weighed. Permeation is determined by weighing the system every 

24 hours and noting the weight loss. After each weighing, the fuel is mixed by inverting the 

assembly, then returning it to its original position. 

5-91 
Final Regulatory Impact Analysis 

We are including two modifications to SAE J30 that are consistent with our current 

requirements for recreational vehicles and highway motorcycles. First, the test fuel must be 

ASTM Fuel C199 (50 percent toluene, 50 percent iso-octane) blended with 10 percent ethanol.6 

This fuel is known as CE10 and is commonly used in industry standards and test procedures such 

as in SAE recommended practices (including SAE J1527). Section 5.4, and Appendix 5D 

presents permeation data for several hose constructions and materials used in hose constructions 

on fuels with and without ethanol. As shown in this data, adding ethanol to the test fuel 

significantly increases permeation. Standard recommended practice for hose testing uses Fuel C, 

or some blend of Fuel C and either ethanol or methanol. This test fuel is generally more 

aggressive than standard gasoline. Although hoses are not generally exposed to Fuel C in use, 

the level of the standard was based on testing using Fuel C and Fuel C blends. In addition, most 

of the test data on low permeation hose presented in this Chapter is based on fuel CE10. For 

these reasons, we believe that it is appropriate to allow Fuel CE10 for hose testing. 

The second modification is that the hose must be preconditioned by filling the hose with 

fuel and soaking long enough to ensure that the permeation rate has stabilized. We are using a 

soak period of 8 weeks at 23 ± 5°C. If a longer time period is necessary to achieve a stabilized 

permeation rate for a given hose design, we expect the manufacturer to use a longer soak period 

(and/or higher temperature) consistent with good engineering judgement. For instance, thickwalled marine fuel hose may take longer to reach a stable permeation rate than thinner-walled 

hose used in Small SI applications. In addition, we are clarifying that the weight loss 

measurement period should be two weeks. 

Alternatively, for purposes of submission of data at certification, permeation could be 

measured using alternative equipment and procedures that provide equivalent results. One 

alternative approaches that we anticipate manufacturers may use are the recirculation technique 

described in SAE J1737.200 To use other alternative methods, such as enclosure-type testing such 

as in 40 CFR part 86, manufacturers have to apply to us and demonstrate equivalence. In 

enclosure testing, manufacturers would need to show how they would account for the ethanol 

fraction of the permeate. 

Recommended practice for automotive fuel tubing is defined in SAE J2260.201 The 

permeation requirements in this standard are one to two orders of magnitude lower than those 

defined for marine hoses. These permeation requirements are based on the same fuels as the 

revised SAE J 1527, but at a much higher temperature (60°C). At 60°C, permeation rates for a 

given material may be 16 times as high or higher than at 23°C based on the rule of thumb that 

permeation doubles for every 10°C increase in temperature. SAE J2260 refers to the permeation 

test procedures in SAE J1737.202 

The procedures in SAE J1737 were designed to measure the low permeation rates needed 

in automotive applications to meet EPA evaporative emission requirements. There was concern 

that the weight loss measurement, such as used in SAE J1527, was not sensitive enough to 

6

 An exception to this is that fuel IE10 may be used for cold-weather fuel lines. 

5-92 
Feasibility of Evaporative Emission Control 

measure these low permeation rates. In addition, this procedure requires exposing the material to 

be tested for hundreds of hours, depending on the material and fuel, to reach a steady-state 

permeation rate. In this procedure, fuel is heated to 60°C and circulated through a tube running 

through a glass test cell. Nitrogen around the tube in this test cell is used to carry the permeate 

to activated charcoal canisters. The canisters are weighed to determine their capture. Because 

the canister is much lighter than the reservoir/hose in the SAE J1527 configuration, a much more 

accurate measurement of the permeation loss can be made. 

Some manufacturers of low permeability product are finding that as their emission rates 

decrease, they need more refined test procedures to accurately measure permeation. These 

manufacturers are finding that the weight of the charcoal canisters are much higher than the 

permeate being measured. As an alternative to the gravimetric approach used in the above two 

procedures, even very low permeation emissions can be measured by a flame ionization detector 

and a SHED. As discussed earlier, SHED testing is generally used to measure evaporative 

emissions from whole automobile systems as well. 

5.6.2 Fuel Tank Permeation Testing 

We are applying similar fuel tank permeation test procedures to Small SI equipment and 

Marine SI vessels as we currently use for recreational vehicles. This testing includes 

preconditioning, durability testing, and permeation measurement. The differences in the test 

procedure compared to recreational vehicles are minor and are intended to simplify the testing. 

For instance, the durability testing is performed during the preconditioning soak period prior to 

the weight loss testing rather than testing the tank twice; once before durability testing, and once 

after. Figure 5.6-2 provides flow charts for this testing (2) compared to the recreational vehicle 

test (1) which includes the calculation of a deterioration factor. 

5-93 
Final Regulatory Impact Analysis 

Figure 5.6-2: Flow Chart of Fuel Tank Permeation Test with and without a 

Deterioration Factor (DF) Determination 

1: Full Test Procedure 2: Short Test without 

with DF* Determination DF Determination 

begin with

new tank 

preconditioning 

fuel soak 

28 ± 5 C 

E10 fuel 

20 weeks 

use final permeation 

test result for 

certification 

baseline 

permeation test run 

E10 fuel 

28 ± 2 C 

fuel soak 

28 ± 5 C 

E10 fuel 

20 weeks** 

final 

permeation test run 

E10 fuel 

28 ± 2 C 

Pressure Cycling 

10,000 x -0.5 to 2.0 psi 

UV Exposure 

24 W/m 

Slosh Testing 

1 million cycles 

E10 fuel 

Durability Testing 

2 

begin test 

use final permeation

test result for 

certification 

fuel soak 

28 ± 5 C 

E10 fuel 

20 weeks** 

final 

permeation test run 

E10 fuel 

28 ± 2 C 

Pressure Cycling 

10,000 x -0.5 to 2.0 psi 

UV Exposure 

24 W/m 

Slosh Testing 

1 million cycles 

E10 fuel 

Durability Testing 

* The deterioration factor (DF) is the difference 

between the baseline and final permeation test 

runs in the full test procedure. In future tests, the 

first 3 steps would be performed, then a DF could 

be applied to determine the final test result. 

** The length of "soak" during durability testing 

may be included in the fuel soak period provided 

that fuel remains in the tank. Soak periods can be 

shortened to 10 weeks if performed at 43 ± 5 C 

5-94 
Feasibility of Evaporative Emission Control 

For the purpose of this testing, “fuel tank” includes the fuel cap and other components 

directly mounted to the tank that become part of the barrier for the fuel and vapor. During 

testing, fittings and openings in the fuel tank intended for hose connections (or petcock) is sealed 

with an impermeable plug. An opening containing a fuel petcock could also be plugged with an 

impermeable fitting because this is an opening to the fuel hose which will be required to meet 

permeation standards. In many installed marine fuel tanks, the fuel cap is not directly mounted 

on the fuel tank. Instead, the fuel cap is usually linked to the fuel tank by a fill neck hose. In 

this case, the fill neck opening in the fuel tank may be sealed with an impermeable plug during 

permeation testing. 

5.6.2.1 Durability Testing

 Prior to the weight loss test, the fuel tank must be preconditioned to ensure that the 

hydrocarbon permeation rate has stabilized. Under this step, the fuel tank must be filled with a 

10 percent ethanol blend (E10), sealed, and soaked for 20 weeks at a temperature of 28 °C ± 5 

°C. Once the permeation rate has stabilized, the fuel tank is drained and refilled with E10, 

sealed, and tested for a baseline permeation rate. The permeation rate from the fuel tank is 

determined by measuring the weight difference the fuel tank before and after soaking at a 

temperature of 28 °C ± 2 °C over a period of at least 20 weeks. The soak periods could be 

shortened to 10 weeks if performed at 43 °C ± 5 °C. The durability testing described below may 

be performed during the soak period. During the slosh testing, a lower tank fill level, consistent 

with the slosh test, is acceptable. 

To determine a permeation emission deterioration factor, we established three durability 

tests: slosh testing, pressure-vacuum cycling, and ultra-violet (UV) light exposure. The purpose 

of these deterioration tests is to help ensure that the technology is durable and the measured 

emissions are representative of in-use permeation rates. For slosh testing, the fuel tank is filled 

to 40 percent capacity with E10 fuel and rocked for 1 million cycles. The pressure-vacuum 

testing contains 10,000 cycles from -0.5 to 2.0 psi. The slosh testing is designed to assess 

treatment durability as discussed above. These tests are designed to assess surface 

microcracking concerns. These two durability tests are based on a draft recommended SAE 

practice.203 The third durability test is intended to assess potential impacts of UV sunlight (0.2 

μm - 0.4 μm) on the durability of the surface treatment. In this test, the tank must be exposed to 

a UV light of at least 0.40 W-hr/m2

 /min on the tank surface for 15 hours per day for 30 days. 

Alternatively, it can be exposed to direct natural sunlight for an equivalent period of time in 

exposure hours. 

The order of the durability tests is optional. However, we require that the fuel tank be 

soaked to ensure that the permeation rate is stabilized just prior to the weight loss test. If the 

slosh test is run last, the length of the slosh test may be considered as part of this soak period. 

Where possible, the deterioration tests may be run concurrently. For example, the fuel tank 

could be exposed to UV light during the slosh test. In addition, if a durability test can clearly be 

shown to not be appropriate for a given product, manufacturers may petition to have this test 

waived. Only fuel tanks using surface barrier treatments or barriers consisting of postprocessing coatings are subject to the slosh and pressure-vacuum tests. In addition, a fuel tank 

5-95 
Final Regulatory Impact Analysis 

that is only used in vehicles where an outer shell prevents the tank from being exposed to 

sunlight may not be subject UV testing. 

After the durability testing, once the permeation rate has stabilized, the fuel tank is 

drained and refilled with fresh fuel, sealed, and tested for a final permeation rate. The final 

permeation rate from the fuel tank is determined using the same measurement method as for the 

baseline permeation rate. The final permeation rate is used for the emission rate from this fuel 

tank. The difference between the baseline and final permeation rates could be used to determine 

a deterioration factor for use on subsequent testing of similar fuel tanks. 

5.6.2.2 Test Fuel 

As discussed in Chapter 3, about much of the fuel sold in the U.S. contains ethanol and 

this percentage is expected to increase dramatically in 2012 and later. The fuel tank permeation 

test fuel is E10, which is a blend of 90 percent certification gasoline (as specified in 40 CFR 

1065.210) blended with 10 percent ethanol for permeation testing of fuel tanks. As an 

alternative, we would allow testing on ASTM Fuel C blended with 10 percent ethanol (Fuel 

CE10). Fuel CE10 is commonly used in industry standards and test procedures such as in SAE 

recommended practices. 

5.6.2.2.1 Effect of ethanol on fuel tank permeation 

Most plastic nonroad fuel tanks today are made out of high-density polyethylene (HDPE) 

or cross-link polyethylene (XLPE). For Small SI and Marine SI markets, plastic is much more 

widely used than metal for fuel tank constructions. For HDPE, E10 fuel has little effect on 

permeation emissions and may even result in slightly lower emissions according to one study.204 

We tested three 0.5 gallon Small SI fuel tanks for permeation using both certification gasoline 

and E10 and found a slight increase in permeation due to ethanol. ARB also tested several Small 

SI fuel tanks on both gasoline and ethanol blends 205,206,207,208 and saw a small increase in 

permeation. Permeation data was collected on two XLPE marine fuel tanks on E10. The 

measured permeation rates were within the range of data from other XLPE marine fuel tanks 

tested on gasoline presented earlier in Table 5.3-1. This data is presented in Table 5.6-1. 

5-96 
Feasibility of Evaporative Emission Control 

Table 5.6-1: Effect of Ethanol on Permeation for HDPE Fuel Tanks 

Material Test Equipment Tank 

gallons 

Test 

Temp(s) 

gasoline 

[g/m2

/day] 

E10 

[g/m2/day] 

Increase in 

Permeation 

HDPE material sample NA 40/C 90a 69a -23% 

HDPE Small SI fuel 0.5 29/C 11.5 13.9 21% 

tanks 0.5 11.4 13.7 21% 

(EPA Testing) 0.5 11.2 14.4 28% 

HDPE Small SI fuel 

tanks 

0.25 

0.25 

18-41/C 11.6 

10.7 

13.6 

11.6 

18% 

7% 

(ARB Testing) 0.25 

0.25 

12.5 

9.9 

11.4 

10.3 

-9% 

4% 

0.25 9.2 10.3 12% 

0.5 12.7 14.8 17% 

3.9 4.8 5.0 4% 

XLPE marine tanks 

(EPA testing) 

12 

12 

29/C --b 7.5 

8.5 

minimal 

a

 ASTM Fuel C was used as gasoline (50% toluene, 50% isooctane). Units are per mm of thickness 

b

 See Table 5.3-1 for data on similar tanks tested on gasoline. 

Although E10 does not have a large effect on permeation through polyethylene, it does 

have a large effect on most other materials used in fuel systems, especially those designed for 

low permeation. This is supported by the data presented in Appendix 5D of permeation rates for 

several fuel system materials on fuel C, CE10, and C15. In addition, ethanol is commonly 

blended into fuels in-use and alcohol fuels may be used more in the future in an effort to use 

alternative energy sources. Therefore, we are requiring E10 as a test fuel to ensure that the 

permeation standard will be met on in-use fuels. 

One study found that permeation from automotive fuel systems increased significantly 

when gasoline containing ethanol was used compared to gasoline without ethanol.209 In this 

case the ethanol fuel was specifically blended to achieve two weight percent oxygen. This test 

fuel represents California reformulated fuel and contains 5.7 percent by volume ethanol. Table 

5.6-2 presents the test results at 29°C. The average increase in permeation due to using E5.7 was 

60 percent. Presumably, this effect would have been higher on E10. Because most of the fuel 

tanks are metal, the effect is largely due to fuel hose/tubing permeation. 

5-97 
Final Regulatory Impact Analysis 

Table 5.6-2: Effect of Ethanol on Permeation from Automotive Fuel Systems 

Fuel System Fuel Tank Gasoline E5.7 Increase 

2001 Toyota Tacoma 

2000 Honda Odyssey 

1999 Toyota Corolla 

1997 Chrysler Town & Country 

1995 Ford Ranger 

1993 Chevrolet Caprice Classic 

1991 Honda Accord LX 

1989 Ford Taurus GL 

1985 Nissan Sentra 

1978 Olds Cutlass Supreme 

Metal 

Plastic (enhanced evap) 

Metal 

Plastic (enhanced evap) 

HDPE 

Fluorinated HDPE 

Metal 

Metal 

Metal 

Metal 

10 

19 

11 

40 

348 

94 

39 

28 

73 

73 

32 

53 

57 

66 

342 

137 

100 

73 

177 

139 

220% 

179% 

418% 

65% 

-2% 

46% 

156% 

161% 

142% 

90% 

One significant finding with the above study was that switching from one fuel to another 

affects the permeation rate within a few weeks. Although operating on gasoline with ethanol 

changes the fuel tank material in such a way that permeation increases, this effect is reversible 

when gasoline is used in the fuel tank for a long enough period of time. This study found that 

the permeation rate at 40°C typically approached a stabilized level within 1 to 2 weeks of 

switching from one fuel to another. 

To investigate the potential effects of fuel switching, we tested two pairs of 6.6 gallon 

portable marine fuel tanks. These fuel tanks used the barrier platelet technology discussed 

above. The first pair used nylon as a barrier material which is highly sensitive to ethanol while 

the second pair used EVOH which is much less sensitive to ethanol. All four tanks were soaked 

on E10 fuel, then the fuel was drained and replaced for testing. For each pair, one tank was 

tested on EPA certification gasoline and the other was tested on E10 fuel (10 percent ethanol, 90 

percent gasoline). We continued the test for more than six weeks to observe the effects of fuel 

switching on the permeation rates. The results suggest that switching to gasoline significantly 

reduces the permeation rate for the nylon barrier tanks, but has no significant effect on the fuel 

tanks using EVOH as a barrier. Note that the nylon tanks had permeation rates near the 

standards when soaked and tested on gasoline, but have much higher permeation rates when 

tested on E10. This data is presented in Figure 5.6-1. The R-squared values for linear fits to the 

data are also presented. The fuel tank with a nylon barrier that experienced fuel switching had a 

lower R-squared value than the other fuel tanks. 

5-98 
Feasibility of Evaporative Emission Control 

Figure 5.6-1: Effect of Fuel Switching on Permeation from Barrier Platelet Fuel Tanks 

R2 = 0.943 

R2

 = 0.995 

R2

 = 0.997 

0 

20 

40 

60 

80 

100 

120 

140 

Weight Loss [grams] 

Nylon, Gasoline 

Nylon, E10 

EVOH, Gasoline 

EVOH, E10 

0 7 14 21 28 35 42 49 

Test Days 

Fuel tank permeation data on both gasoline and E10 fuel are presented earlier in this 

chapter for nylon handheld tanks, fluorinated and sulfonated Small SI tanks, portable tanks with 

non-continuous nylon barrier platelets, and rotationally molded tanks with a nylon inner barrier. 

This data is repeated here in Table 5.6-3 to better focus on the effect of ethanol on fuel tank 

permeation. As shown by this data and the previous discussion, ethanol in the test fuel tends to 

increase permeation. However, the effect of ethanol on permeation appears to be highly variable 

depending on the materials or surface treatments used in constructing the fuel tank. 

5-99 
Final Regulatory Impact Analysis 

Table 5.6-3: Permeation Rates on Gasoline and E10 for Barrier Fuel Tanks 

Permeation Control Capacity 

[gallons] 

Gasoline 

[g/m2

/day] 

E10 

[g/m2/day] 

% Increase 

nylon 6 0.24 0.34 0.42 

0.48 

32% 

nylon 6, 33% glass 0.05 0.62 1.01 

1.12 

0.93 

65% 

nylon 6, 30% glass 0.06 1.45 2.2 

2.5 

60% 

nylon 6, 30% glass 0.06 1.30 1.4 

2.1 

37% 

fluorination 0.5 0.56 

0.62 

0.22 

0.43 

0.62 

0.62 

19% 

sulfonation 0.5 2.5 

2.7 

2.2 

3.9 

4.2 

2.9 

49% 

non-continuous nylon platelets 2.0 3.7 6.8 84% 

Rotomolded with PA11 liner* 1mm barrier 

thickness 

0.17 

0.24 

0.12 

0.91 

0.72 

0.78 

0.81 

350% 

* based on testing for California (California Phase II gasoline and fuel CE10) 

5.6.2.2.2 Effect of CE10 versus E10 on fuel tank permeation 

As discussed above, we will allow the use of fuel CE10 as an alternative to E10 for fuel 

tank permeation testing. The primary fuel, E10 is representative of in-use fuel and is consistent 

with the certification fuel used for recreational vehicles. However, fuel CE10 is widely used by 

industry for materials testing. Data presented earlier in this chapter suggests that permeation is 

generally significantly higher on fuel CE10 for fuel hoses. We were therefore interested in the 

effect of fuel CE10 versus E10 on fuel tank permeation. We tested several fuel tanks and found 

that permeation was only slightly higher on CE10 than E10 for most of the fuel tanks tested. 

To study the effects of CE10 versus E10 on permeation, we used fuel tanks that had been 

previously tested on fuel E10. All of these tanks were drained and refueled with fresh test fuel. 

Most of the tanks were filled with fuel CE10; however, with some exceptions, one of each tank 

type was filled with fresh E10 for comparison. These fuel tanks were then preconditioned by 

soaking them for 12 weeks with the new test fuel. Note that all of the test tanks had been 

5-100 
Feasibility of Evaporative Emission Control 

soaking with E10 fuel for more than a year (and in some cases multiple years) prior to beginning 

this preconditioning soak. Following the soak period, each tank was drained, refilled with fresh 

fuel, and sealed. Permeation was measured over two weeks at 29/C. The fuel tanks were 

weighed on each weekday during this period. 

Table 5.6-4 presents the results of this testing. In most cases, emissions were only 

slightly higher on CE10 than E10. The exceptions were the nylon 6 and the acetal copolymer 

fuel tanks which showed much higher permeation on CE10. However, the permeation rates for 

these fuel tanks were still below the standard when tested on fuel CE10. The fuel tank with a 

continuous EVOH barrier was well below the standard on fuel CE10. No comparison was made 

to E10 results for this technology. 

Table 5.6-4: Permeation Rates on Gasoline and E10 for Barrier Fuel Tanks 

Permeation Control Capacity 

[gallons] 

E10 

[g/m2

/day] 

CE10 

[g/m2/day] 

% Increase 

nylon 6 0.24 0.69 1.4 

1.2 

90% 

HDPE 0.5 12.5 13.3 

13.5 

7% 

fluorination 0.5 0.41 0.49 

0.52 

21% 

sulfonation 0.5 3.1 4.2 

2.9 

16% 

non-continuous platelets (4% nylon) 6.6 4.5 5.3 16% 

non-continuous platelets (2% EVOH) 6.6 3.0* 3.3 10% 

non-continuous platelets (4% EVOH) 6.6 2.2 2.3 6% 

non-continuous platelets (6% EVOH) 6.6 1.3 1.4 6% 

continuous EVOH barrier 5.6 -- 0.05 

0.01 

NA 

acetal copolymer 0.8 0.25 0.55 

0.65 

140% 

* based on previous testing (presented earlier in this chapter) 

5.6.2.3 Reference Tank 

In cases where the permeation of a fuel tank is low, and the sample tank is properly 

sealed, the effect of air buoyancy can have a significant effect the measured weight loss. Air 

buoyancy refers to the effect on air density on the perceived weight of an object. As air density 

5-101 
Final Regulatory Impact Analysis 

increases, it will provide an upward thrust on the fuel tank and create the appearance of a lighter 

tank. Air density can be determined by measuring relative humidity, air temperature, and air 

pressure.210 

One testing laboratory presented data to EPA on their experience with variability in 

weight loss measurements when performing permeation testing on portable fuel tanks.211 They 

found that the variation was due to air buoyancy effects. By applying correction factors for air 

buoyancy, they were able to greatly remove the variation in the test data. A technical brief on 

the calculations they used is available in the docket.212 

A more direct approach to accounting for the effects of air buoyancy is to use a reference 

fuel tank. In this approach, an identical fuel tank to that being tested for permeation is tested 

without fuel in it and used as a reference fuel tank. Dry sand can be added to this tank to make 

up the difference in mass associated with the test tank being full of fuel. The reference tank is 

then sealed so that the buoyancy effect on the reference tank is the same as the test tank. The 

measured weight loss of the test tank can then be corrected by any measured changes in weight 

in the reference tank. The California Air Resources Board uses this approach for measuring 

portable fuel tank emissions, and they refer to the reference tank as a “trip blank.”213 

5.6.2.4 Engineering Design-Based Certification 

A metal fuel tank automatically meets the design criteria for a design-based certification 

as a low-permeation fuel tank, subject to the restrictions on fuel caps and seals described below. 

There is also a body of existing test data showing that co-extruded fuel tanks from automotive 

applications have permeation rates that are well below the new standard. We are allowing 

design-based certification for co-extruded high-density polyethylene fuel tanks with a continuous 

ethylene vinyl alcohol (EVOH) barrier layer. The EVOH barrier layer is required to be at least 2 

percent of the wall thickness of the fuel tank. In addition, the ethylene content of the EVOH can 

be no higher than 40 mole percent. 

To address the permeability of the gaskets, and seals used on metal and co-extruded 

tanks, the design criteria include a specification that seals (e.g. gaskets and o-rings) not made of 

low-permeation materials must have a total exposed surface area less than 0.25 percent of the 

total inside surface area of the fuel tank. For example, consider a four gallon fuel tank with an 

inside surface area of 0.40 square meters. The total exposed surface area of these seals on the 

fuel tank, in this example, must be smaller than 1000 mm2

 (= 0.25%/100 × 0.40m2 × 1,000,000 

mm2

/m2). This is consistent with the proposed rule and the current requirements for recreational 

vehicles, but allows for larger seals for larger tanks. In addition, if a non-metal fuel cap is 

directly mounted to the fuel tank, the surface area of the fuel cap (determined by the 

cross-sectional area of the fill opening) may not exceed 3.0 percent of the total inside surface 

area of the fuel tank. 

A metal or co-extruded fuel tank with a fuel cap and seals that meet these design criteria 

would be expected to reliably pass the standard. However, we believe it is not appropriate to 

assign an emission level to fuel tanks using a design-based certification option that will allow 

5-102 
Feasibility of Evaporative Emission Control 

them to generate emission credits. Given the uncertainty of emission rates from the seals and 

gaskets, we will not consider these tanks to be any more effective than other fuel tanks meeting 

emission standards. 

In the case where the fuel cap is directly mounted on the fuel tank, we consider the cap 

and associated seals to be part of the fuel tank. As discussed above, we allow the fuel cap to be 

tested either mounted on the fuel tank, or individually. As an alternative to testing the fuel cap, 

the manufacturer may opt to use a default permeation rate of 30 g/m2/day. To be eligible for this 

default rate, the seal on the fuel cap must be made of a low-permeation material, such as a 

fluoroelastomer. The surface area associated with this default value is the cross sectional area of 

the opening that is sealed by the fuel cap. If this default value were used, the fuel fill would be 

sealed with a non-permeable plug during the tank permeation test, and the default permeation 

rate would be factored into the final result. 

For the purposes of this provision, we consider low-permeation materials to be those that 

haves a permeation rate not more than 10 g-mm/m2/day at 23/C on CE10 fuel as tested under the 

procedures specified in SAE J2659.214 

5.6.3 Diurnal Emission Testing 

The test procedure for diurnal emissions is to place the fuel tank in a SHED7

, vary the 

temperature over a prescribed profile, and measure the hydrocarbons escaping from the fuel tank. 

The final result is reported in grams per gallon where the grams are the mass of hydrocarbons 

escaping from the fuel tank over 24 hours and the gallons are the nominal fuel tank capacity. 

The test procedure is based on the automotive evaporative emission test described in 40 CFR 

part 86, subpart B, with modifications specific to marine applications. 

5.6.3.1 Temperature Profile 

For installed marine fuel tanks, we believe that the fuel temperature profile observed in 

the tank has a lower variation in temperature due to the inherent insulation provided by the boat 

hull. Data discussed earlier in this chapter, and presented in Appendix 5A, suggest that the fuel 

temperature in an installed marine tank sees a change in temperature less than that of ambient 

air. Based on this data, the fuel temperature change in boats stored on trailers would be expected 

to be about half of ambient. For boats stored in the water, the fuel temperature change would be 

expected to be about 20 percent of ambient. Based on discussions with industry, we use a boat 

length as a surrogate for determining if a boat is a trailer boat. We consider a boat that is at or 

below 8.5 feet in width and below 26 feet in length as a trailer boat and larger boats as being 

primarily stored in the water. 

To account for the differences between ambient and fuel temperature, we established a 

7

 Sealed Housing for Emission Determination 

5-103 
Final Regulatory Impact Analysis 

test temperature profile of 78-90°F (25.6-32.2°C) for marine fuel tanks installed in boats less 

than 26 feet in length and at or below 8.5 feet in width. For larger boats, we established a test 

temperature profile of 81.6-86.4/F (27.6-30.2/C). These test temperature profiles are based on 

fuel rather than ambient temperature. Figure 5.6-3 presents the three temperature profiles over 

24 hours. Numerical values are presented in Appendix 5E. 

Figure 5.6-3: Diurnal Temperature Profiles 

70 

75 

80 

85 

90 

95 

100 

0 4 8 12 16 20 24 

Elapsed Time [hours] 

Temperature [°F] 

portable (air temp) 

installed <26ft (fuel temp) 

installed >26ft (fuel temp) 

The automotive diurnal test procedure includes a three day temperature cycle. The 

purpose of this test length is to ensure that the carbon canister can hold at least three days of 

diurnal emissions without vapor breaking-through the canister. For vessels using carbon 

canisters as an evaporative emission control strategy, we established a multiple day cycle here as 

well so that the passive purging can be observed. In the automotive test, the canister is loaded, 

then purged during an engine test prior to the first day of testing. Because we are anticipating 

canisters on marine applications to be passively purged we are using a different approach. Prior 

to the first day of testing, the canister is loaded to full working capacity, then run over the 

diurnal test temperature cycle to allow one day of passive purging. The test result is then based 

on the highest recorded value in the following three days. 

For fuel systems using a sealed system (or sealed-system with pressure relief), we do not 

believe that a three day test is necessary. Prior to the first day of testing, the fuel is stabilized at 

the initial test temperature. Following this stabilization, the SHED is purged and a single diurnal 

temperature cycle run. Because this technology does not depend on purging or storage capacity 

of a canister, multiple days of testing should not be necessary. Therefore, we established a oneday test for the following technologies: sealed system without pressure relief, sealed system with 

5-104 
Feasibility of Evaporative Emission Control 

a pressure relief valve, sealed bladder fuel tanks, sealed fuel tanks with a volume compensating 

air bag. 

5.6.3.2 Test Fuel 

Consistent with the automotive test procedures, the test must take place using 

certification gasoline with a vapor pressure of 9.0 RVP. We do not require ethanol to be blended 

into the test fuel. Although ethanol has a significant effect on permeation, it would not be 

expected to affect diurnal emissions except in that it may affect fuel vapor pressure. 

Diurnal emissions are not only a function of temperature and fuel volatility, but of the 

size of the vapor space in the fuel tank as well. Consistent with the automotive procedures, the 

fill level at the start of the test must be 40 percent of the nominal capacity of the fuel tank. 

Nominal capacity of the fuel tank is defined as the volume of fuel, specified by the manufacturer, 

to which the fuel tank can be filled when sitting in its intended position. The vapor space that 

normally occurs in a fuel tank, even when “full,” is not considered in the nominal capacity of the 

fuel tank. 

5.6.3.3 Tank Configuration 

Installed marine fuel tanks are typically equipped with a vent line. As shown above, this 

vent line can impact the emissions determined over the test procedure because it largely restricts 

diffusion losses. Therefore, open vent marine fuel tanks that are designed with a connection for 

a vent line must be equipped with a one meter fuel line to more accurately reflect real world 

emissions. This should only be necessary for baseline configurations. 

The majority of marine fuel tanks are made of plastic. Even plastic fuel tanks designed to 

meet our standards are expected to have some amount of permeation. However, over the length 

of the diurnal test, if it were performed on a new tank that had not been previously exposed to 

fuel, the effect of permeation on the test results should be insignificant. For fuel tanks that have 

reached their stabilized permeation rate (such as testing on in-use tanks), we believe that it is 

appropriate to correct for permeation. In such a case, the permeation rate could be measured 

from the fuel tank and subtracted from the final diurnal test result. The fuel tank permeation rate 

has to be stabilized on the 9 RVP test fuel used for the diurnal test and measured either over the 

diurnal temperature cycle or at a constant temperature (28 ± 2°C). This test measurement is 

made just prior (within 24 hours) to the diurnal emission test to ensure that the permeation rate 

does not change prior to the diurnal test. In addition, the test fuel needs to remain in the fuel 

tank between the permeation and diurnal tests to ensure a stable permeation rate. The fuel tank 

could be emptied to change test fuels and test set ups; however, this period will not be allowed to 

exceed one hour. As an alternative to stabilizing the permeation rate prior to testing, the 

permeation could be measured immediately before and after the diurnal test, and the lower 

permeation rate used to correct the diurnal test results. In this case, the test fuel is not removed 

after the diurnal test, and the second permeation test begins within 8 hours of the end of the 

diurnal test. 

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Final Regulatory Impact Analysis 

5.6.3.4 Carbon Canister Engineering Design 

Design-based certification may be used as an option to performing the above test. For 

vessels using a carbon canister to control diurnal emissions, it is important to ensure that the 

canister design is sufficient to achieve the standards. The following discussion outlines the 

requirements that are necessary to ensure adequate canister design. These design parameters and 

their associated test procedures are largely based on our understanding of current industry 

practices for marine grade carbon.215 

5.6.3.4.1 Carbon canister capacity 

In a passive purge system, the storage capacity of the carbon canister must be properly 

matched to the fuel system. Ideally, the canister is large enough to take full advantage of the 

passive purge caused by cooling of the fuel tank. By creating more open sites in the canister, 

greater vapor collection is possible during the next heating event. If a canister is undersized, 

then the vessel would not likely meet the standards. On the other hand, after a certain point, 

increasing the size of the canister offers little additional emission control. Once the system 

reaches a stabilized purge/load condition, the emission reduction potential is based on the 

portion of the canister that purges and loads rather than the full volume of the canister. 

The storage capacity of a carbon canister is based both on the volume of the canister and 

the working capacity of the carbon. Butane working capacity (BWC) is a measure of the vapor 

storage capacity of the carbon and is expressed in units of mass of butane per unit of volume. 

The BWC of the carbon must be at least 9 g/dL based on the test procedures specified in ASTM 

D5228-92.216 Under this test procedure, butane vapor is fed through a carbon sample at a 

specified rate, until the mass of the carbon sample reaches equilibrium. The butane is then 

purged off with dry air. BWC of the carbon sample is calculated from the difference in the 

measured mass of the carbon sample before and after the purge. 

Using the ASTM test procedure, the BWC represents the full saturated capacity of the 

canister and not the amount of vapor that the canister will hold before breakthrough occurs. 

Under the EPA automotive test procedure in 40 CFR 86.134-96, the canister capacity is based on 

the amount of butane loaded in the canister until 2 grams of breakthrough is measured. 

However, the ASTM procedure gives a repeatable measure that is currently used by industry. 

The design standard of 9 g/dL is based on this test procedure and therefore accounts for the 

differences in the ASTM and existing EPA automotive procedure. 

Based on the data presented earlier in this chapter, we are requiring that the volume of 

the carbon canister must be a minimum of 0.04 liters of carbon per gallon of fuel tank capacity 

for fuel tanks installed in trailerable boats (<26 feet in length and #8.5 feet in width). For larger 

boats, the fuel temperature may be less affected by diurnal temperature swings for two reasons. 

First, these fuel tanks are in larger vessels which are more likely to be stored in the water and 

therefore, subject to smaller temperature fluctuations. Second, these fuel tanks are generally 

larger and have larger thermal inertia in the fuel which may lead to lower temperature 

fluctuation. Therefore, for fuel tanks installed on non-trailerable boats ($26 feet in length or 

5-106 
Feasibility of Evaporative Emission Control 

>8.5 feet in width), the design minimum volume is 0.016 liters of carbon every gallon per gallon 

of fuel tank capacity. 

5.6.3.4.2 Carbon humidity resistance 

In a marine environment, the carbon may be exposed to more humid air, on average, than 

in land-based applications such as cars and trucks. Traditional carbons used in automotive 

applications can adsorb water, thereby closing sites off to hydrocarbons. With active purge and 

carbon heating during refueling vapor collection, the water vapor is easily purged off the carbon. 

Under this rule, we are basing the design specification on a passive purge canister design and are 

not requiring onboard refueling vapor recovery. Therefore, we believe that the carbon should be 

resistant to moisture in the air. In the in-use program discussed above, marine grade carbon was 

used that was developed specifically for high humidity applications.217

 Design-based certification requirements for humidity resistance are based on the 

specifications of the humidity-resistant carbon used in the in-use demonstration program. This 

carbon meets a moisture adsorption capacity maximum of 0.5 grams of water per gram of carbon 

at 90 percent relative humidity and a temperature of 25±5/C. This limit is based on a test 

procedure where dried carbon is exposed to water vapor and the pressure in the sample chamber 

is controlled to achieve the correct partial pressure of the water to achieve the desired relative 

humidity. The adsorption of water in the carbon is calculated based on the reduction in pressure 

in the sample chamber. More detail on this test procedure is available in the docket.218 

5.6.3.4.3 Carbon durability 

Another issue that has been raised with regard to canister use in marine applications is 

the durability of the canister under the shocks that can be observed on a marine vessel. 

Automotive applications see shocks and vibration as well and the carbon is protected by packing 

it under pressure in the canister. To address the concern of carbon durability, however, we are 

including a carbon strength requirement. This strength requirement is consistent with the 

specifications for the carbon used in the in-use test program described above, which was 

designed to have a higher hardness value and lower dust attrition rates than typical automotive 

carbons. 

The industry procedure for carbon pellet strength is to determine the average pellet size 

in a sample of carbon before and after a pan hardness test. Pellet size is determined by 

separating the carbon by size using sieves. The pan hardness test involves shaking the carbon in 

a pan with steel balls over a fixed period of time. The pellet strength is determined by taking the 

ratio of the average pellet size of the carbon before and after the pan and ball attrition test. Pellet 

strength must be at least 85 percent. The test procedure is ASTM D3802-79219 with two 

variations. First, as discussed above, hardness is defined as the ratio of mean particle diameter 

before and after the attrition test. Second, the attrition test uses twenty 1⁄2" steel balls and ten 3⁄4" 

steel balls rather than fifteen of each as specified in ASTM D3802-79. These variations on the 

ASTM procedure reflect common industry practice for pelletized carbons in contrast to the 

original test procedure which were intended for granular carbons.220 

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Final Regulatory Impact Analysis 

5.6.3.4.4 Canister design 

The design of the canister itself is important in building an effective and durable carbon 

canister system. The canister should be made of a material that is compatible with the 

application. For instance, the material should be fuel resistant and durable. Where a flame test 

is required by the Coast Guard, the material should be able to pass this test on its own or with a 

protective cover. In addition, the canister material must have good structural integrity at 

temperatures that it would be exposed to in a boat. If the material changes in dimension at 

temperature, that flexing may loosen the carbon packing, allowing the carbon to move and 

eventually deteriorate. The canister should be installed in the boat in such a way that undue 

stress is not placed on the canister. It should also be properly constructed so that there are no 

leaks in the canister. 

The canister must be packed in such a way that the carbon does not move inside the 

canister in-use. If the carbon were able to move, it would eventually break down under 

vibration. Over time the carbon could deteriorate into dust which could eventually escape from 

the canister. This is not an issue with a carbon canister that uses a properly designed and 

installed volume compensator. The basic design of a volume compensator is that compression is 

held on the carbon bed with a spring. A mesh or foam cover is used on the volume compensator 

that will allow air to pass through, but will hold the carbon pellets in place. 

The carbon should be packed into the canister in such a way that there is a consistent size 

of carbon pellets throughout the canister. If the carbon settles in the storage hopper, it would be 

possible for some canisters to be filled largely with the smallest diameter carbon pellets (or dust) 

which would increase the pressure restriction of the canister. Also, if the carbon is not packed 

properly when placed into the canister, it could later settle leading to a volume reduction of the 

carbon that is too large for the volume compensator to address. 

The carbon canister design must allow for a proper flow path of vapor and air through the 

carbon bed. In current carbon canister designs, an air gap is typically installed upstream of the 

carbon bed. Flow directors may be molded into this air gap. The purpose of the air gap is to 

allow the vapor or purge air to disperse and flow through the entire carbon bed. Even with a 

small air gap, the vapor will disperse because it will attempt to follow the path of least resistance 

through the canister. Without the air gap, the flow could be predominately in the center of the 

carbon (or wherever the intake hose connection is located). In addition, to prevent flow 

restriction, the carbon granules must have a minimum mean diameter of 3.1 mm based on the 

procedures in ASTM D2862.221 

The geometry of a carbon canister can affect the effectiveness of the control system. For 

instance, a long, narrow canister will have higher efficiency than a short wide canister. This is 

because some breakthrough can occur if the pathway is too short for the flow of vapor. Based on 

one study, the effectiveness of the carbon canister increases notably until a length to diameter 

ratio of about 3.5 is achieved.222 At higher ratios, less of an impact on efficiency was observed. 

At too high of a length to diameter ratio, significant back pressure may occur in the system. 

5-108 
Feasibility of Evaporative Emission Control 

5.6.3.4.5 Integration with Fuel System 

It is important that a carbon canister system be appropriately integrated into the fuel 

system. For instance, the canister must be positioned in the vent line, and potentially a liquid 

separation valve added, to ensure that liquid fuel does not reach the canister during refueling. 

We also expect the fuel system design to minimize spit-back out of the fill neck during refueling. 

A design that caused fuel to stream out the fill neck during refueling, even with a fuel nozzle 

shut-off mechanism, is not acceptable. 

5.7 Impacts on Noise, Energy, and Safety 

The Clean Air Act requires EPA to consider potential impacts on noise, energy, and 

safety when establishing the feasibility of new emission standards for marine vessels. 

5.7.1 Noise 

In this case, we do not expect evaporative emission controls to have any impact on noise 

from Small SI equipment or marine vessels because noise from the affected parts of the fuel 

system is insignificant. 

5.7.2 Energy 

We anticipate that the evaporative emission standards will have a positive impact on 

energy. By capturing or preventing the loss of fuel through evaporation, we estimate that the 

lifetime average fuel savings will be about 1.4 gallons for an average piece of Small SI 

equipment and 28 gallons for an average boat. This translates to a fuel savings of about 45 

million gallons for Small SI equipment and 26 million gallons for Marine SI vessels in 2030 

when most of the affected equipment used in the U.S. is expected to have evaporative emission 

control. 

5.7.3 Safety 

As part of the development of this rule, EPA performed a technical study on the safety of 

emission control technology for Small SI equipment and Marine SI vessels.223 The conclusions 

of this study are presented below. Although the study focuses on equipment with engines less 

than 37 kilowatts, the conclusions drawn for marine apply to boats with larger engines as well as 

ABYC, USCG, UL, and SAE requirements do not distinguish between engine sizes. 

EPA has reviewed the fuel hose and fuel tank characteristics for NHH and HH equipment 

and evaluated control technology which could be used to reduce evaporative emissions from 

these two subcategories. This technology is capable of achieving reductions in fuel tank and fuel 

hose permeation without an adverse incremental impact on safety. For fuel hoses and fuel tanks, 

the applicable consensus standards, manufacturer specific test procedures and EPA requirements 

are sufficient to ensure that there will be no increase in the types of fuel leaks that lead to fire 

and burn risk in use. Instead, these standards will reduce vapor emissions both during operation 

5-109 
Final Regulatory Impact Analysis 

and in storage. That reduction, coupled with some expected equipment redesign, is expected to 

lead to reductions in the risk of fire or burn without affecting component durability. 

We also conducted a design and process Failure Mode and Effects Analyses (FMEA) 

comparing current Phase 2 and Phase 3 compliant engines and equipment to evaluate 

incremental changes in risk probability as a way of evaluating the incremental risk of upgrading 

Phase 2 engines to meet Phase 3 emission standards.224 This is an engineering analysis tool to 

help engineers and other professional staff on the FMEA team to identify and manage risk. In a 

FMEA, potential failure modes, causes of failure, and failure effects are identified and a 

resulting risk probability is calculated from these results. This risk probability is used by the 

FMEA team to rank problems for potential action to reduce or eliminate the causal factors. 

Identifying these causal factors is important because they are the elements that a manufacturer 

can consider reducing the adverse effects that might result from a particular failure mode. 

Our FEMA evaluated permeation and running loss controls on nonhandheld engines. We 

found that these controls do not increase the probability of fire and burn risk from those expected 

with current fuel systems, but could in fact lead to directionally improved systems from a safety 

perspective. Finally, the running loss control program for nonhandheld equipment will lead to 

changes that are expected to reduce risk of fire during in-use operation. Moving fuel tanks away 

from heat sources, improving cap designs to limit leakage on tip over, and requiring a tethered 

cap will all help to eliminate conditions which lead to in-use problems related to fuel leaks and 

spillage. Therefore, we believe that the application of emission control technology to reduce 

evaporative emissions from these fuel hoses and fuel tanks will not lead to an increase in 

incremental risk of fires or burns and in some cases is likely to at least directionally reduce such 

risks. 

EPA has reviewed the fuel hose and fuel tank characteristics for marine vessels and 

evaluated control technology which could be used to reduce evaporative emissions from boats. 

With regard to fuel hoses, fuel tanks, and diurnal controls, there are rigorous USCG, ABYC, UL, 

and SAE standards which manufacturers will continue to meet for fuel system components. All 

of these standards are designed to address the in-use performance of fuel systems, with the goal 

of eliminating fuel leaks. The low permeation fuel hoses and tanks needed to meet the Phase 3 

requirements need to pass these standards and every indication is that they will pass. 

Furthermore, the EPA permeation certification requirements related to emissions 

durability will add an additional layer of assurance. Low permeation fuel hoses are used safely 

today in many marine vessels. Low permeation fuel tanks and diurnal emission controls have 

been demonstrated in various applications for many years without an increase in safety risk. 

Furthermore, a properly designed fuel system with fuel tank and fuel hose permeation controls 

and diurnal emission controls will reduce the fuel vapor in the boat, thereby reducing the 

opportunities for fuel related fires. In addition, using improved low permeation materials 

coupled with designs meeting USCG and ABYC requirements should reduce the risk of fuel 

leaks into the vessel. EPA believes that the application of emission control technologies on 

marine engines and vessels for meeting the evaporative emissions standards will not lead to an 

5-110 
Feasibility of Evaporative Emission Control 

increase in incremental risk of fires or burns, and in many cases may incrementally decrease 

safety risks in certain situations. 

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7/10/01 7/12/01 7/14/01 7/16/01 7/18/01 7/20/01 7/22/01 7/24/01

Final Regulatory Impact Analysis 

APPENDIX 5A: Diurnal Temperature Traces 

Figure 5A-1: Temperature Trace for Personal Watercraft on Trailer 

55 

60 

65 

70 

75 

80 

85 

90 

95 

100 

105 

12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 

Temperature [deg F]

Fuel Temp 

Ambient Temp 

Figure 5A-2: Temperature Trace for Jet Boat on Trailer 

45.00 

50.00 

55.00 

60.00 

65.00 

70.00 

75.00 

80.00 

85.00 

90.00 

95.00 

12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 

Temperature [deg F] 

fuel temp 

ambient 

5-112 
10/12/01 10/12/01 10/13/01 10/13/01 10/14/01 10/14/01 10/15/01 10/15/01

1/9/03 12:00

AM

1/9/03 12:00

PM

1/10/03

12:00 AM

1/10/03

12:00 PM

1/11/03

12:00 AM

1/11/03

12:00 PM

1/12/03

12:00 AM

1/12/03

12:00 PM

Feasibility of Evaporative Emission Control 

Figure 5A-3: Temperature Trace for Runabout on Trailer 

55.00 

60.00 

65.00 

70.00 

75.00 

80.00 

85.00 

90.00 

95.00 

100.00 

105.00 

12:00 AM 12:00 PM 12:00 AM 12:00 PM 12:00 AM 12:00 PM 12:00 AM 12:00 PM 

Temperature [deg F]

Fuel Temp 

Ambient Temp 

Figure 5A-4: Temperature Trace for Jet Boat on Trailer 

55.0 

60.0 

65.0 

70.0 

75.0 

80.0 

85.0 

90.0 

95.0 

100.0 

105.0 

Temperature [deg F] 

fuel temp 

ambient 

12:00 AM 12:00 PM 12:00 AM 12:00 PM 12:00 AM 12:00 PM 12:00 AM 12:00 PM 

5-113 
9/12/01 9/15/01 9/18/01 9/21/01 9/24/01 9/27/01 9/30/01 10/3/01

9/5/01 9/6/01 9/7/01 9/8/01 9/9/01 9/10/01 9/11/01 9/12/01 9/13/01

Final Regulatory Impact Analysis 

Figure 5A-5: Temperature Trace for Runabout in Water 

35 

40 

45 

50 

55 

60 

65 

70 

75 

80 

85 

12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 

Temperature [deg F] 

Fuel Temp 

Ambient Temp 

Water Temp 

Figure 5A-6: Temperature Trace of Deckboat in Water 

45 

50 

55 

60 

65 

70 

75 

80 

85 

90 

95 

Temperature [deg F]

Fuel Temp 

Ambient Temp 

Water Temp 

12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 

5-114 
Feasibility of Evaporative Emission Control 

APPENDIX 5B: Emission Results for Small SI Equipment Fuel Tanks 

Showing Effect of Venting on Diffusion 

5B.1 Diffusion Effects from Variable Temperature Diurnal Testing 

Figure 5B-1: Diurnal/Diffusion Test Results for BM Metal Fuel Tank (2 Labs) 

12.0 

6.0 

Temperature 

Stock Cap Vent, Lab 1 

Stock Cap Vent, Lab 2 

Hose Vent, Lab 1 

Hose Vent, Lab 2 

30.0 

4.0 20.0 

2.0 10.0 

0.0 0.0 

60.0 

10.0 50.0 

8.0 40.0 

Temperature [deg C] 

HC [grams] 

0 3 6 9 12 15 18 21 24 

Te st Hours 

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Final Regulatory Impact Analysis 

Figure 5B.1-2: Diurnal/Diffusion Test Results for BP Plastic Fuel Tank 

8.0 40.0 

7.0 35.0 

6.0 30.0 

0 3 6 9 12 15 18 21 24 

Te st Hours 

Temperature 

Modified Cap Vent 

Stock Cap Vent 

Hose Vent 

5.0 25.0 

4.0 20.0 

HC [grams]

3.0 15.0 

10.0 2.0 

1.0 5.0 

0.0 0.0 

Temperature [deg C] 

Figure 5B.1-3: Diurnal/Diffusion Test Results for HP Plastic Fuel Tank 

0.0 

0.2 

0.4 

0.6 

0.8 

1.0 

1.2 

0 3 6 9 12 15 18 21 24 

Test Hours 

HC [grams] 

Temperature 

Stock Cap Vent 

Hose Vent 

8.0 

0.0 

24.0 

32.0 

40.0 

48.0 

Temperature [deg C] 

16.0 

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Feasibility of Evaporative Emission Control 

Figure 5B.1-4: Diurnal/Diffusion Test Results for TP Plastic Fuel Tank 

1.6 40.0 

Temperature 

Stock Cap Vent 

Hose Vent 

1.4 35.0 

1.2 30.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0.0 

HC [grams] 

Temperature [deg C] 

25.0 

20.0 

15.0 

10.0 

5.0 

0.0 

0 3 6 9 12 15 18 21 24 

Test Hours 

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Final Regulatory Impact Analysis 

5B.2 Isothermal Results for Small SI Equipment Fuel Tanks Showing Effect of Venting on 

Diffusion 

Figure 5B.2-1: Isothermal Diffusion Test Results for BM Metal Fuel Tank 

0.00 

1.00 

2.00 

3.00 

4.00 

5.00 

6.00 

7.00 

HC [grams] 

5.0 

0.0 

10.0 

20.0 

25.0 

35.0 

Temperature [deg C] 

15.0 

30.0 

Temp (cap) 

Temp (hose) 

Stock Cap Vent 

Hose Vent 

0 3 6 9 12 15 18 21 24 

Test Hours 

Figure 5B.2-2: Isothermal Diffusion Test Results for BP Plastic Fuel Tank 

7.00 35.0 

6.00 30.0 

5.00 25.0 

1.00 

0 3 6 9 12 15 18 21 24 

Test Hours 

Temp (mod cap) 

Temp (cap) 

Temp (hose) 

Stock Cap Vent 

Stock Cap Vent 

Hose Vent 

5.0 

0.00 0.0 

Temperature [deg C] 

HC [grams] 4.00 20.0 

3.00 15.0 

2.00 10.0 

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Feasibility of Evaporative Emission Control 

Figure 5B.2-3: Isothermal Diffusion Test Results for HP Plastic Fuel Tank 

0.00 

0.05 

0.10 

0.15 

0.20 

0.25 

0.30 

0.35 

HC [grams] 

5.0 

0.0 

10.0 

20.0 

25.0 

35.0 

Temperature [deg C] 

15.0 

30.0 

Temperature 

Stock Cap Vent 

Hose Vent 

0 3 6 9 12 15 18 21 24 

Test Hours 

Figure 5B.2-4: Isothermal Diffusion Test Results for TP Plastic Fuel Tank 

0.00 

0.05 

0.10 

0.15 

0.20 

0.25 

0.30 

0.35 

HC [grams] 

5.0 

0.0 

10.0 

20.0 

25.0 

35.0 

Temperature [deg C] 

15.0 

30.0 

Temp (cap) 

Temp (hose) 

Stock Cap Vent 

Hose Vent 

0 3 6 9 12 15 18 21 24 

Test Hours 

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Final Regulatory Impact Analysis 

APPENDIX 5C: Diurnal Emission Results: Canister and Passive-Purge 

Diurnal Emissions for a 30 Gallon Marine 

Fuel Tank with 2.1 L Canister, 72-96F 

Evaporative HC [grams/day] 

50.00 

45.00 

40.00 

35.00 

30.00 

25.00 

20.00 

15.00 

10.00 

5.00 

0.00 

Diurnal Emissions 

Monday Outliers 

Baseline Emission Level 

0 5 10 15 20 25 

Test Days 

5-120 

30 
Feasibility of Evaporative Emission Control 

APPENDIX 5D: Material Properties of Common Fuel System Materials 

This appendix presents data on permeation rates for a wide range of materials that can be 

used in fuel tanks and hoses. The data also includes effects of temperature and fuel type on 

permeation. Because the data was collected from several sources, there is not complete data on 

each of the materials tested in terms of temperature and test fuel. Table D-1 gives an overview 

of the fuel systems materials included in the data set. Tables D-2 through D-3 present 

permeation rates using Fuel C, a 10 percent ethanol blend (CE10), and a 15 percent methanol 

blend (CE15) for the test temperatures of 23, 40, 50, and 60°C. 

Table 5D-1: Fuel System Materials 

Material Name Composition 

ACN NBR acrylonitrile 

Carilon aliphatic poly-ketone thermoplastic 

Celcon acetal copolymer 

CFM fluoroelastomer 

CO epichlorohydrin homopolymer 

CR polychloroprene polymer 

CSM chlorosulfonated polyethylene 

E14659 fluoropolymer film 

E14944 fluoropolymer film 

ECO epichlorohydrin-ethylene oxide copolymer 

ETER epichlorohydrin-ethylene oxide terpolymer 

ETFE ethylenetetrafluoroethylene, fluoroplastic 

EVOH ethylene vinyl alcohol, thermoplastic 

FEB fluorothermoplastic 

FEP fluorothermoplastic 

FKM fluorocarbon elastomer 

FPA copolymer of tetrafluoroethylene and perfluoroalkoxy monomer 

FVMQ fluorovinyl methal silicone rubber (flourosilicone) 

GFLT fluoroelastomer 

HDPE high-density polyethylene 

HDPE high density polyethylene 

HNBR hydrogenated acrylonitrile-butadiene rubber 

LDPE low density polyethylene 

NBR acrylonitrile-butadiene rubber 

Nylon 12 thermoplastic 

PBT polybutylene terephthalate, thermoplastic 

PFA fluorothermoplastic 

Polyacetal thermoplastic 

PTFE polytetrafluoroethylene, fluoroplastic 

PVDF polyvinylidene fluoride, fluorothermoplastic 

THV tetrafluoroethylene, hexafluoropropylene, vinyledene fluoride 

5-121 
Final Regulatory Impact Analysis 

Table 5D-2: Fuel System Material Permeation Rates at 23°C by Fuel Type 225,226,227,228,229,230 

Material Name Fuel C 

g-mm/m2

/day 

Fuel CE10 

g-mm/m2/day 

CM15 

g-mm/m2/day 

HDPE 

Nylon 12, rigid 

EVOH 

Polyacetal 

PBT 

PVDF 

NBR (33% ACN) 

HNBR (44%ACN) 

FVMQ 

FKM Viton A200 (66%F) 

FKM Viton B70 (66%F) 

FKM Viton GLT (65%F) 

FKM Viton B200 (68%F) 

FKM Viton GF (70%F) 

FKM Viton GFLT (67%F) 

FKM - 2120 

FKM - 5830 

Teflon FEP 1000L 

Teflon PTFE 

Teflon PFA 1000LP 

Tefzel ETFE 1000LZ 

Nylon 12 (GM grade) 

Nitrile 

Silicone Rubber 

Fluorosilicone 

FKM 

FE 5620Q (65.9% fluorine) 

FE 5840Q (70.2% fluorine) 

PTFE 

ETFE 

PFA 

THV 500 

35 

0.2 

– 

– 

– 

– 

669 

230 

455 

0.80 

0.80 

2.60 

0.70 

0.70 

1.80 

8 

1.1 

0.03 

– 

0.18 

0.03 

6.0 

130 

– 

– 

– 

– 

– 

0.05 

0.02 

0.01 

0.03 

– 

– 

– 

– 

– 

– 

1028 

553 

584 

7.5 

6.7 

14 

4.1 

1.1 

6.5 

– 

– 

0.03 

– 

0.03 

0.05 

24 

635 

– 

– 

16 

7 

4 

– 

– 

– 

– 

35 

64 

10 

3.1 

0.4 

0.2 

1188 

828 

635 

36 

32 

60 

12 

3.0 

14 

44 

8 

0.03 

0.05 

0.13 

0.20 

83 

1150 

6500 

635 

– 

– 

– 

0.08* 

0.04* 

0.05* 

0.3 

* tested on CM20. 

5-122 
Feasibility of Evaporative Emission Control 

Table 5D-3: Fuel System Material Permeation Rates at 40°C by Fuel Type 231,232 

Material Name Fuel C 

g-mm/m2

/day 

Fuel CE10 

g-mm/m2/day 

CM15 

g-mm/m2/day 

Carilon 

EVOH - F101 

EVOH - XEP380 

HDPE 

LDPE 

Nylon 12 (L2101F) 

Nylon 12 (L2140) 

Celcon 

Fortron PPS SKX-382 

Celcon Acetal M90 

Celanex PBT 3300 (30% GR) 

Nylon 6 

Dyneon E14659 

Dyneon E14944 

ETFE Aflon COP 

m-ETFE 

ETFE Aflon LM730 AP 

FKM-70 16286 

GFLT 19797 

Nitrile 

FKM 

FE 5620Q (65.9% fluorine) 

FE 5840Q (70.2% fluorine) 

THV-310 X 

THV-500 

THV-610 X 

0.06 

<0.0001 

<0.0001 

90 

420 

2.0 

1.8 

0.38 

– 

– 

– 

– 

0.25 

0.14 

0.24 

0.27 

0.41 

11 

13 

– 

– 

– 

– 

– 

0.31 

– 

1.5 

0.013 

– 

69 

350 

28 

44 

2.7 

0.12 

0.35 

3 

26 

– 

– 

0.67 

– 

0.79 

35 

38 

1540 

86 

40 

12 

– 

– 

– 

13 

3.5 

5.3 

71 

330 

250 

– 

– 

– 

– 

– 

– 

2.1 

1.7 

1.8 

1.6 

2.6 

– 

– 

3500 

120 

180 

45 

5.0 

3.0 

2.1 

Table 5D-4: Fuel System Material Permeation Rates at 50°C by Fuel Type 233 

Material Name Fuel C 

g-mm/m2

/day 

Fuel CE10 

g-mm/m2/day 

CM15 

g-mm/m2/day 

Carilon 

HDPE 

Nylon 12 (L2140) 

Celcon 

ETFE Afcon COP 

FKM-70 16286 

GFLT 19797 

0.2 

190 

4.9 

0.76 

– 

25 

28 

3.6 

150 

83 

5.8 

1.7 

79 

77 

– 

– 

– 

– 

– 

– 

– 

5-123 
Final Regulatory Impact Analysis 

Table 5D-5: Fuel System Material Permeation Rates at 60°C by Fuel Type 234,235,236,237 

Material Name Fuel C 

g-mm/m2

/day 

Fuel CE10 

g-mm/m2/day 

CM15 

g-mm/m2/day 

Carilon 

HDPE 

Nylon 12 (L2140) 

Celcon 

ETFE Afcon COP 

FKM-70 16286 

GFLT 19797 

polyeurethane (bladder) 

THV-200 

THV-310 X 

THV-510 ESD 

THV-500 

THV-500 G 

THV-610 X 

ETFE 6235 G 

THV-800 

FEP 

0.55 

310 

9.5 

1.7 

– 

56 

60 

285 

– 

– 

6.1 

– 

4.1 

2.4 

1.1 

1.0 

0.2 

7.5 

230 

140 

11 

3.8 

170 

130 

460 

54 

– 

18 

11 

10 

5.4 

3.0 

2.9 

0.4 

– 

– 

– 

– 

– 

– 

– 

– 

– 

38 

35 

20 

22 

9.0 

6.5 

6.0 

1.1 

5-124 
Feasibility of Evaporative Emission Control 

APPENDIX 5E: Diurnal Test Temperature Traces 

Table 5E-1: Temperature vs. Time Sequence for Diurnal Testing 

Test 

Time* 

[minutes] 

Portable Fuel Tanks 

SHED Air Temperature 

Installed Fuel Tanks 

Trailerable Boat 

Fuel Temperature 

Installed Fuel Tanks 

Nontrailerable boat 

Fuel Temperature 

Fahrenheit Celsius Fahrenheit Celsius Fahrenheit Celsius 

0 

60 

120 

180 

240 

300 

360 

420 

480 

540 

600 

660 

720 

780 

840 

900 

960 

1020 

1080 

1140 

1200 

1260 

1320 

1380 

1440 

72.0 

72.5 

75.5 

80.3 

85.2 

89.4 

93.1 

95.1 

95.8 

96.0 

95.5 

94.1 

91.7 

88.6 

85.5 

82.8 

80.9 

79.0 

77.2 

75.8 

74.7 

73.9 

73.3 

72.6 

72.0 

22.2 

22.5 

24.2 

26.8 

29.6 

31.9 

33.9 

35.1 

35.4 

35.6 

35.3 

34.5 

33.2 

31.4 

29.7 

28.2 

27.2 

26.1 

25.1 

24.3 

23.7 

23.3 

22.9 

22.6 

22.2 

78.0 

78.3 

79.8 

82.2 

84.6 

86.7 

88.6 

89.6 

89.9 

90.0 

89.8 

89.1 

87.9 

86.3 

84.8 

83.4 

82.5 

81.5 

80.6 

79.9 

79.4 

79.0 

78.7 

78.3 

78.0 

25.6 

25.7 

26.5 

27.9 

29.2 

30.4 

31.4 

32.0 

32.2 

32.2 

32.1 

31.7 

31.0 

30.2 

29.3 

28.6 

28.0 

27.5 

27.0 

26.6 

26.3 

26.1 

25.9 

25.7 

25.6 

81.6 

81.7 

82.3 

83.3 

84.2 

85.1 

85.8 

86.2 

86.4 

86.4 

86.3 

86.0 

85.5 

84.9 

84.3 

83.8 

83.4 

83.0 

82.6 

82.4 

82.1 

82.0 

81.9 

81.7 

81.6 

27.6 

27.6 

27.9 

28.5 

29.0 

29.5 

29.9 

30.1 

30.2 

30.2 

30.2 

30.0 

29.7 

29.4 

29.1 

28.8 

28.5 

28.3 

28.1 

28.0 

27.9 

27.8 

27.7 

27.6 

27.6 

* Repeat as necessary 

5-125 
Final Regulatory Impact Analysis 

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5-126 
Feasibility of Evaporative Emission Control 

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Specifications,” August 31, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0136. 

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Paper 901110, 1990, Docket Identification EPA-HQ-OAR-2004-0008-0170. 

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5-127 
Final Regulatory Impact Analysis 

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35. Letter from Bill Scott, Country Industries Technologies, to Mike Samulski U.S. EPA, regarding a gas tank vent 

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0008-0435. 

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5-128 
Feasibility of Evaporative Emission Control 

50. Nulman, M., Olejnik, A., Samus, M., Fead, E., Rossi, G., “Fuel Permeation Performance of Polymeric 

Materials,” SAE Paper 2001-01-1999, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0162. 

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8, 2001, California Air Resources Board, Docket Identification EPA-HQ-OAR-2004-0008-0146. 

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Resources Board, Docket Identification EPA-HQ-OAR-2004-0008-0149. 

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5-129 
Final Regulatory Impact Analysis 

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Variable Volume Containers.xls,” October 26, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0291. 

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data,” April 9, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0238. 

73. Kathios, D., Ziff, R., Petrulis, A., Bonczyk, J., “Permeation of Gasoline and Gasoline-alcohol Fuel Blends 

Through High-Density Polyethylene Fuel Tanks with Different Barrier Technologies,” SAE Paper 920164, 1992, 

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Docket, Docket Identification EPA-HQ-OAR-2004-0008-0186. 

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August 29, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0200. 

76. “Durability Testing of Barrier Treated High-Density Polyethylene Small Off-Road Engine Fuel Tanks,” 

California Air Resources Board, June 21, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0152. 

77. “Durability Testing of Barrier Treated High-Density Polyethylene Small Off-Road Engine Fuel Tanks,” 

California Air Resources Board, March 7, 2003, Docket Identification EPA-HQ-OAR-2004-0008-0153. 

78. Conversation between Mike Samulski, U.S. EPA and Tom Schmoyer, Sulfo Technologies, June 17, 2002. 

79. “Sulfo Data”, E-mail from Tom Schmoyer, Sulfotechnologies to Mike Samulski, U.S. EPA, March 17, 2003, 

Docket Identification EPA-HQ-OAR-2004-0008-0223. 

80. “ADDENDUM TO: Durability Testing of Barrier Treated High-Density Polyethylene Small Off-Road Engine 

Fuel Tanks,” California Air Resources Board, March 27, 2003, Docket Identification EPA-HQ-OAR-2004-0008-

0154. 

81. “Resin and Additives - SO3 Compatible,” Email from Tom Schmoyer, Sulfo Technologies to Mike Samulski 

and Glenn Passavant, U.S. EPA, June 19, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0215. 

82. Email from Jim Watson, California Air Resources Board, to Mike Samulski, U.S. EPA, “Attachment to Resin 

List,” August 30, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0234. 

83. Walles, B., Nulford, L., “Five Year Durability Tests of Plastic Gas Tanks and Bottles with Sulfonation Barrier,” 

Coalition Technologies, LTD, for Society of Plastics Industry, January 15, 1992, Docket Identification EPA-HQOAR-2004-0008-0233. 

5-130 
Feasibility of Evaporative Emission Control 

84. Kathios, D., Ziff, R., “Permeation of Gasoline and Gasoline-Alcohol Fuel Blends Through High-Density 

Polyethylene Fuel Tanks with Different Barrier Technologies,” SAE Paper 920164, 1992, Docket Identification 

EPA-HQ-OAR-2004-0008-0172. 

85. www.arb.ca.gov/msprog/spillcon/reg.htm, Updated March 26, 2001, Copy of linked data reports available in 

Docket, Docket Identification EPA-HQ-OAR-2004-0008-0186. 

86. “Permeation Rates of Blitz Fluorinated High Density Polyethylene Portable Fuel Containers,” California Air 

Resources Board, April 5, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0155. 

87. Email from Jim Watson, California Air Resources Board, to Phil Carlson, U.S. EPA, “Early Container Data,” 

August 29, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0200. 

88. www.pensteel.co.uk/light/smp/fluorination.htm. A copy of this site, as downloaded on August 13, 2004, is 

available in Docket, Docket Identification EPA-HQ-OAR-2004-0008-0214. 

89. “Durability Testing of Barrier Treated High-Density Polyethylene Small Off-Road Engine Fuel Tanks,” 

California Air Resources Board, June 21, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0152. 

90. “Durability Testing of Barrier Treated High-Density Polyethylene Small Off-Road Engine Fuel Tanks,” 

California Air Resources Board, March 7, 2003, Docket Identification EPA-HQ-OAR-2004-0008-0153. 

91. “OPEI HHPC Comments on EPA Proposed Phase 3 Rule for HH Fuel Tank Permeation,” Outdoor Power 

Equipment Institute,” Presentation to EPA, February 5, 2008. 

92. Kathios, D., Ziff, R., “Permeation of Gasoline and Gasoline-Alcohol Fuel Blends Through High-Density 

Polyethylene Fuel Tanks with Different Barrier Technologies,” SAE Paper 920164, 1992, Docket Identification 

EPA-HQ-OAR-2004-0008-0172. 

93. “SORE Component EO Summary,” email from Jim Watson, California Air Resources Board, to Mike Samulski, 

U.S. EPA, August 18, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0405. 

94. “Fluorination Information,” e-mail from Doug McGregor, BMW, to Mike Samulski, US EPA, August 8, 2003, 

Docket Identification EPA-HQ-OAR-2004-0008-0259. 

95. “Final Report: Permeation Testing of Injection Molded Walk Behind Mower (WBM) Fuel Tanks using 

California’s TP-901 Procedures,” Automotive Testing Laboratories, Inc., August 30, 2005, Docket Identification 

EPA-HQ-OAR-2004-0008-0182. 

96. “Baseline Test Results: Permeation Testing of Injection Molded Walk Behind Mower (WBM) Fuel Tanks using 

Federal Test Procedures,” Automotive Testing Laboratories, Inc., August 30, 2005, Docket Identification EPA-HQOAR-2004-0008-0183. 

97. “Final Results: Permeation Testing of Injection Molded Walk Behind Mower (WBM) Fuel Tanks using Federal 

Test Procedures,” Automotive Testing Laboratories, Inc., July 28, 2006, Docket Identification EPA-HQ-OAR-2004-

0008-0419. 

98. “Selar RB Technical Information,” Faxed from David Zang, Dupont, to Mike Samulski, U.S. EPA on May 14, 

2002, Docket Identification EPA-HQ-OAR-2004-0008-0221. 

99. Lyn, K., “A Study on Problems with Aluminum Fuel Tanks in Recreational Boats,” Underwriters Laboratories 

Inc., sponsored by USCG, 1994, Docket Identification EPA-HQ-OAR-2004-0008-0098. 

5-131 
Final Regulatory Impact Analysis 

100. E-mail from Alan Dubin, Ticona, to Mike Samulski, U.S. EPA, “Fuel Permeation Chart and Aggressive Fuels 

Brochure,” July 31, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0196. 

101. Samulski, M., “Permeation Emission Testing on Three Roto-Molded Acetal Copolymer Fuel Tanks,” Memo to 

Docket OAR-2004-0008, October 25, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0443. 

102. E-mail from Jim Watson, California ARB to Mike Samulski, U.S. EPA, “fuel tank specs.xls,” March 6, 2006, 

Docket Identification EPA-HQ-OAR-2004-0008-0357. 

103. Chambers, J., “Marine Fuel Containment... A Permanent Solution,” Presentation by Engineered Composite 

Structures Inc. at the 2004 International Boatbuilders Exposition, October 25, 2004, Docket Identification EPA-HQOAR-2004-0008-0037. 

104. “Fluorination Information,” e-mail from Doug McGregor, BMW, to Mike Samulski, US EPA, August 8, 2003, 

Docket Identification EPA-HQ-OAR-2004-0008-0259. 

105. Fead, E., Vengadam, R., Rossi, G., Olejnik, A., Thorn, J., “Speciation of Evaporative Emissions from Plastic 

Fuel Tanks,” SAE Paper 981376, 1998, Docket Identification EPA-HQ-OAR-2004-0008-0175. 

106. Email from Dennis Goodenow, California Air Resources Board, to Mike Samulski, U.S. EPA, “Coextruded 

PFC Data, September 11, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0436. 

107. “OPEI HHPC Comments on EPA Proposed Phase 3 Rule for HH Fuel Tank Permeation,” Outdoor Power 

Equipment Institute,” Presentation to EPA, February 5, 2008. 

108. Solvay Advanced Polymers, “Solvay Advanced Polymers Unveils Modified Ixef® Polyarylamide Barrier 

Material for Automotive Fuel Systems,” Press Release, March 2, 200, Docket Identification EPA-HQ-OAR-2004-

0008-0539. 

109. “Test Report: EPA CCD-05-14 Fuel Tank Permeation Testing,” Testing Services Group, TSG Report Numbers 

L706619-1.1, 2.1, 3.1, and 4.1A, October 19, 2007, Docket Identification EPA-HQ-OAR-2004-0008-XXXX. 

110. O’Brien, Partridge, Clay, “New Materials and Multi-Layer Rotomolding Technology for Higher Barrier 

Performance Rotomolded Tanks,” Atofina Chemicals, Inc., Presented at the Topcon Rotational Molding by Design 

Conference, June 6-8, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0044. 

111. Samulski, M., “Permeation Emission Testing of Two Multi-Layer Roto-Molded Fuel Tanks,” Memo to Docket 

OAR-2004-0008, August 31, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0132. 

112. Partridge, R., “Petro-SealTM for Ultra-Low Permeation,” Arkema Inc., Presentation at 2004 International 

Boatbuilders Exposition, October 25, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0038. 

113. “Test Report 16514-1A: NMMA/USCG Tests of Prototype Fuel Tank for Atofina Chemicals, Inc.,” IMANNA 

Laboratory, July 16, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0416. 

114. “Test Report 16544-1A: NMMA/USCG Tests of Prototype Fuel Tank for Atofina Chemicals, Inc.,” IMANNA 

Laboratory, July 16, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0417. 

115. “Test Report 17474-1: NMMA/USCG Tests of 40 Gallon Prototype Fuel Tank for Arkema, Inc.,” IMANNA 

Laboratory, October 12, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0418. 

116. “Final Report, Fuel Tank Testing, Procedure Number: SAE J288 DEC 02, Sections 4.2, 4.3,” MGA Research 

Corporation, October 19, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0406. 

5-132 
Feasibility of Evaporative Emission Control 

117. “SORE Component EO Summary,” email from Jim Watson, California Air Resources Board, to Mike 

Samulski, U.S. EPA, August 18, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0405. 

118. Faler, Gary, “Cyclics CBT® Resin for Dual Layer Applications in Rotomolding,” Cyclics Corporation, August 

2006, Docket Identification EPA-HQ-OAR-2004-0008-0415. 

119. Faler, Gary, ““Cyclics CBT® Resin for Rotomolding,” Cyclics Corporation, Presented at ARMO 2006 

Convention & Exposition, September, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0414. 

120.Graham, B., Cook, D., “Measurement of Fuel Barrier Properties of Rotational Molded Materials,” Article from 

ANTEC 2006 Rotational Molding Division, May 12, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0404. 

121. Fish, D., “Advanced Polymer Concepts,” Presentation at the 2004 International Boatbuilders Exposition, 

October 25, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0039. 

122. Bauman, B., “Advances in Plastic Fuel Tanks,” Presentation by Fluoro-Seal International at the 2004 

International Boatbuilders Exposition, October 25, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0036. 

123. Bauman, B., “Advances in Plastic Fuel Tanks,” Presentation by Fluoro-Seal International at the 2004 

International Boatbuilders Exposition, October 25, 2004, Docket Identification EPA-HQ-OAR-2000-0008, 

Document OAR-2004-0008-0036. 

124. SAE Surface Vehicle Standard, “Marine Fuel Hoses,” Society of Automotive Engineers J 1527, Issued 1985-

12, Revised 1993-02, Docket Identification EPA-HQ-OAR-2004-0008-0177. 

125. American Society for Testing and Materials, “Standard Test Method for Rubber Property–Effects of Liquids,” 

ASTM D 471-06, November 2006, Docket Identification EPA-HQ-OAR-2004-0008-0511. 

126. “Public Hearing on Proposed Evaporative Emission Standards for New Marine Vessels that Use Spark-Ignition 

Engines,” Held on Monday, October 7, 2002 at the U.S. Environmental Protection Agency, Office of Transportation 

and Air Quality, in Ann Arbor, Michigan, De Scribe Reporting, Inc., Docket Identification EPA-HQ-OAR-2004-

0008-0265. 

127. “Test Report: 24 hr MicroShed Test on 3 Standard Fuel Hoses,” Testing Services Group, TSG Report Number 

L201672-2.5, July 29, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0227. 

128. Akron Rubber Development Laboratory, “Test Report PN# 50107” Prepared for the U.S. EPA, December 13, 

2002, Docket Identification EPA-HQ-OAR-2004-0008-0184. 

129. Akron Rubber Development Laboratory, “Test Report PN# 50108” Prepared for the U.S. EPA, December 13, 

2002, Docket Identification EPA-HQ-OAR-2004-0008-0185. 

130. “Test Report: Marine Fuel Hose Testing; 6-hour/28/C Constant Temperature MicroSHED after a cumulative 

13-week soak in IE-10 Test Fuel at 40/C,” Testing Services Group, TSG Report Number L404396-1.1A, January 20, 

2005, Docket Identification EPA-HQ-OAR-2004-0008-0407. 

131. “Test Report: Permeation by Weight Loss,” Testing Services Group, TSG Report Number L505371-6.1, May 

15, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0409. 

132. Harold Haskew, “NMMA/EPA Meeting,” Harold Haskew & Associates, Inc, presented at NMMA/EPA 

meeting on January 24, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0359. 

133. SAE Vehicle Recommended Practice, “Personal Watercraft Fuel Systems,” Society of Automotive Engineers J 

2046, Issued January 19, 1993, Docket Identification EPA-HQ-OAR-2004-0008-0179. 

5-133 
Final Regulatory Impact Analysis 

134. Memorandum from Mike Samulski to Docket A-2000-02, “Hose Permeation Data from Saint-Gobain 

Performance Plastics,” October 17, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0210. 

135. SAE Recommended Practice J30, “Fuel and Oil Hoses,”June 1998, Docket Identification EPA-HQ-OAR2004-0008-0176. 

136. Baltz, G., “Effects of Alcohol Extended Fuels on the Rate of Fuel Hose Permeation,” SAE Paper 880709, 

Presented at the International Congress and Exposition February 29-March 4, 1988, Docket Identification EPA-HQOAR-2004-0008-0167. 

137. “OPEI Fuel Line Permeation Results,” Walbro Engine Management, April 12, 2006, Docket Identification 

EPA-HQ-OAR-2004-0008-0440. 

138. “HHPC Evaluation of EPA Proposed Phase 3 Rule for Fuel Line Permeation,” Outdoor Power Equipment 

Institute, presentation to EPA, February 5, 2008. 

139. Horvath, J., “Optimizing Permeation Resistance and Low Temperature Flexibility in Heat Resistant NBR Fuel 

Hose,” SAE Paper 790661, presented at the Passenger Car Meeting, June 11-15, 1979, Docket Identification EPAHQ-OAR-2004-0008-0166. 

140. MacLachlan, J., “Automotive Fuel Permeation Resistance - A Comparison of Elastomeric Materials,” SAE 

Paper 790657, presented at the Passenger Car Meeting, June 11-15, 1979, Docket Identification EPA-HQ-OAR2004-0008-0165. 

141. Testing Services Group, “Marine Fuel Hose MicroSHED Testing; 6-hour/28°C Constant Temperature 

MicroSHED after a cumulative 13-week soak in IE-10 Test Fuel at 40°,” TSG Report No. L404396-1.1A, January 

24, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0407. 

142. Testing Services Group, “Marine Fuel Hose MicroSHED Testing; 24-hourEPA MicroSHED after a cumulative 

2-week soak in IE-10 Test Fuel at 40°,” TSG Report No. L404396-2.1A, January 24, 2005, Docket Identification 

EPA-HQ-OAR-2004-0008-0408. 

143. Harold Haskew, “Marine Fuel System Hose Permeation Testing: 2nd Progress Report,” Harold Haskew & 

Associates, Inc., testing performed at Sterling Performance Testing Laboratory, October 3, 2005, Docket 

Identification EPA-HQ-OAR-2004-0008-0358. 

144. Harold Haskew, “Marine Fuel System Hose Permeation Testing: 2nd Progress Report,” Harold Haskew & 

Associates, Inc., testing performed at Sterling Performance Testing Laboratory, October 3, 2005, Docket 

Identification EPA-HQ-OAR-2004-0008-0358. 

145. Harold Haskew, “NMMA/EPA Meeting,” Harold Haskew & Associates, Inc, presented at NMMA/EPA 

meeting on January 24, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0359. 

146. “Test Report: Permeation by Weight Loss,” Testing Services Group, TSG Report Number L505371-6.1, May 

15, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0409. 

147. Sterling Performance, “U.S.E.P.A. Fuel Line Permeation 050085; Version 1.0,” August 13, 2005, Docket 

Identification EPA-HQ-OAR-2004-0008-0428. 

148. Denbow, R., Browning, L., Coleman, D., “Report Submitted for WA 2-9, Evaluation of the Costs and 

Capabilities of Vehicle Evaporative Emission Control Technologies,” ICF, ARCADIS Geraghty & Miller, March 

22, 1999, Docket Identification EPA-HQ-OAR-2004-0008-0194. 

5-134 
Feasibility of Evaporative Emission Control 

149. Denbow, R., Browning, L., Coleman, D., “Report Submitted for WA 2-9, Evaluation of the Costs and 

Capabilities of Vehicle Evaporative Emission Control Technologies,” ICF, ARCADIS Geraghty & Miller, March 

22, 1999, Docket Identification EPA-HQ-OAR-2004-0008-0194. 

150. SAE Recommended Practice J2260, “Nonmetallic Fuel System Tubing with One or More Layers,”1996, 

Docket Identification EPA-HQ-OAR-2004-0008-0180. 

151. 33 CFR 183.558 

152. SAE Surface Vehicle Standard, “Marine Fuel Hoses,” Society of Automotive Engineers J 1527, Issued 1985-

12, Revised 1993-02, Docket Identification EPA-HQ-OAR-2004-0008-0177. 

153. “Visit to Dyneon on June 12, 2002,” Memorandum from Mike Samulski, U.S. EPA to Docket A-2000-01, June 

17, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0208. 

154. “Meeting with Avon on June 27, 2002,” Memorandum from Mike Samulski, U.S. EPA to Docket A-2000-01, 

August 6, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0207. 

155. “Meeting with Avon on June 27, 2002,” Memorandum from Mike Samulski, U.S. EPA to Docket A-2000-01, 

August 6, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0207. 

156. Akron Rubber Development Laboratory, “Test Report; PN# 49503,” Prepared for the U.S. EPA, September 3, 

2002, Docket Identification EPA-HQ-OAR-2004-0008-0187. 

157. Akron Rubber Development Laboratory, “Test Report PN# 50107” Prepared for the U.S. EPA, December 13, 

2002, Docket Identification EPA-HQ-OAR-2004-0008-0184. 

158. Akron Rubber Development Laboratory, “Test Report PN# 50108” Prepared for the U.S. EPA, December 13, 

2002, Docket Identification EPA-HQ-OAR-2004-0008-0185. 

159. Akron Rubber Development Laboratory, “Test Report PN# 53609” Prepared for American Honda Motor 

Company, September 26, 2003, Docket Identification EPA-HQ-OAR-2004-0008-0189. 

160. Akron Rubber Development Laboratory, “Test Report PN# 53630” Prepared for the U.S. EPA, September 26, 

2003, Docket Identification EPA-HQ-OAR-2004-0008-0190. 

161. Akron Rubber Development Laboratory, “Test Report PN# 53908” Prepared for the U.S. EPA, October 20, 

2003, Docket Identification EPA-HQ-OAR-2004-0008-0191. 

162. Email from Mike Fauble, Avon Automotive to Mike Frederick Jr., Avon Automotive, “SAE J30 Test Results,” 

April 26, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0394. 

163. Fuller, R., “Unique Low Permeation Elastomeric Laminates for Fuel Hose; F200 Technology used in 

Automotive Fuel Hose,” Hearing Testimony for Dupont-Dow Elastomers on NPRM, October 7, 2002, Docket 

Identification EPA-HQ-OAR-2004-0008-0197. 

164. “Test Report: 24 hr MicroSHED Test of Fuel Line Assemblies After 8 Week Soak in Fuel C,” Testing Services 

Group, TSG Report Number L201672-3.1, June 25, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0229. 

165. “Test Report: EPA MicroSHED Test on Fuel Line Assemblies 24-Hour EPA MicroSHED Test with Multipoint 

@ 8-Weeks,” Testing Services Group, TSG Report Number L201672-2.3, June 17, 2002, Docket Identification 

EPA-HQ-OAR-2004-0008-0228. 

5-135 
Final Regulatory Impact Analysis 

166. “Test Report: EPA MicroSHED Test on Fuel Line Assemblies 24-Hour EPA MicroSHED Re-Test of Part 

#01672-11,” Testing Services Group, TSG Report Number L201672-3.1R, July 8, 2002, Docket Identification EPAHQ-OAR-2004-0008-0230. 

167. Akron Rubber Development Laboratory, “Test Report PN# 50107” Prepared for the U.S. EPA, December 13, 

2002, Docket Identification EPA-HQ-OAR-2004-0008-0184. 

168. Akron Rubber Development Laboratory, “Test Report PN# 50108” Prepared for the U.S. EPA, December 13, 

2002, Docket Identification EPA-HQ-OAR-2004-0008-0185 

169. Akron Rubber Development Laboratory, “Test Report PN# 52318” Prepared for the U.S. EPA, July 24,2003, 

Docket Identification EPA-HQ-OAR-2004-0008-0188. 

170. Harold Haskew, “Marine Fuel System Hose Permeation Testing: 2nd Progress Report,” Harold Haskew & 

Associates, Inc., testing performed at Sterling Performance Testing Laboratory, October 3, 2005, Docket 

Identification EPA-HQ-OAR-2004-0008-0358. 

171. Harold Haskew, “NMMA/EPA Meeting,” Harold Haskew & Associates, Inc, presented at NMMA/EPA 

meeting on January 24, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0359. 

172. Akron Rubber Development Laboratory, “Test Report PN# 52318” Prepared for the U.S. EPA, July 24,2003, 

Docket Identification EPA-HQ-OAR-2004-0008-0188. 

173. “Meeting with DuPont and Teleflex on December 10, 2002,” memorandum from Mike Samulski, U.S. EPA to 

Docket A-2000-02, December 10, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0260. 

174. “Low perm marine fuel hose,” e-mail from Rob Bentley, Teleflex to Alan Stout U.S. EPA, July 16, 2003, 

Docket Identification EPA-HQ-OAR-2004-0008-0225. 

175. Engineered Composite Solutions, “Press Release: Feb 2008 ECS develops low permeation primer bulb,” 

retrieved from http://www.engineeredcompositesolutions.com/press_releases.htm on April 24, 2008. 

176. BluSkies Marine Products, “Primer Bulb; A White Paper,” retrieved from www.bluskies.us on June 25, 2008. 

177. “SORE Component EO Summary,” email from Jim Watson, California Air Resources Board, to Mike 

Samulski, U.S. EPA, August 18, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0405. 

178. Letter from William Guerry, Kelly Drye Collier Shannon, to Glenn Passavant, U.S. EPA, and Susan Bathalon, 

U.S. Consumer Product Safety Commission, “EPA Proposal, Phase III, Small Engine Regulations - Fuel Lines for 

Cold Weather Handheld Products,” January 25, 2007, Docket Identification EPA-HQ-OAR-2004-0008-0524. 

179. Outdoor Power Equipment Institute, “Fuel Hose Design in Relation to the Design and Operation of Handheld 

Power Equipment,” Presentation to EPA, June 21, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0399. 

180. Outdoor Power Equipment Institute, “Comparison of NBR and FPM (Viton) Performance on Hand Held 

Equipment,” Presentation to EPA, Docket Identification EPA-HQ-OAR-2004-0008-0441. 

181. “Alpha List of OEM Approvals,” http://www.precixinc.com/oemlist.html, downloaded August 15, 2006, 

Docket Identification EPA-HQ-OAR-2004-0008-0411. 

182. “Viton: Volume Swell of Viton® Fluoroelastomers in Fuel C / Ethanol Blends,” DuPont Performance 

Elastomers, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0510. 

5-136 
Feasibility of Evaporative Emission Control 

183. “FKM / Genuine Viton®,” http://www.o-ring.info/en/datasheets/fkm-genuine-viton/, downloaded August 15, 

2006, Docket Identification EPA-HQ-OAR-2004-0008-0410. 

184. Hatano, M., Otsuka, M., Ogata, C., Suetsugu, N., Amemiya, T., Kudo, M., “Development of New FKM ORings with Superior Fuel-Oil Resistance and Low-Temperature Properties,” SAE Paper 2005-01-1743, 2005, Docket 

Identification EPA-HQ-OAR-2004-0008-0433. 

185. Yamaguchi, Y., Shojima, D., Ogata, C., Oya, K., Kawasaki, K., Kudo, M., “Development of the New FKM ORing for a Cooling Device,” 2005-01-1753, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0434. 

186. “Technical Information; Dyneon Fluorelastomer LTFE 6400X,” 3M, Issued February, 2003, Docket 

Identification EPA-HQ-OAR-2004-0008-0521. 

187. “Relative Permeation of Elastomers,” Precix, downloaded from www.precixinc.com on February 14, 2007, 

Docket Identification EPA-HQ-OAR-2004-0008-0525. 

188. Balzer, J., “F-TPV: A New Horizon for TPE Technology,” Presented by Daikin America to U.S. EPA on 

February 14, 2007, Docket Identification EPA-HQ-OAR-2004-0008-0522. 

189. Letter from Trevor J. Richards, President Spring Cove Marina, “Fuel Spills While Filling Pleasure Craft 

Tanks,” April 23, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0383. 

190. Letter from Van DePiero, City of Pittsburg, California to Steve Burkholder, Enviro Fill, April 19, 2006, Docket 

Identification EPA-HQ-OAR-2004-0008-0384. 

191. American Boat and Yacht Council, “H-24 Gasoline Fuel Systems,” 2005, Docket Identification EPA-HQOAR-2004-0008-0429. 

192. Email from Steve Burkholder, Enviro-Fill, to Mike Samulski and Alan Stout, U.S. EPA, “Overfill Prevention 

System Developments,” July 25, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0447. 

193. Boat U.S. Foundation, “Foundation Findings #40; Spill? What Spill?; Products to Keep Fuel Where it 

Belongs–In Your Tank,” www.boatus.com/foundation/Findings/findings40, March 2005, Docket Identification 

EPA-HQ-OAR-2004-0008-0431. 

194. Letter from Steve Burkholder, Enviro-Fill, to Mike Samulski, U.S. EPA, March 1, 2006, Docket Identification 

EPA-HQ-OAR-2004-0008-0430. 

195. Letter from Steve Burkholder, Enviro-Fill, to Mike Samulski, U.S. EPA, January 13, 2006, Docket 

Identification EPA-HQ-OAR-2004-0008-0446. 

196. Email from Steve Burkholder, Enviro-Fill, to Mike Samulski and Alan Stout, U.S. EPA, “Overfill Prevention 

System Developments,” July 25, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0447. 

197. SAE Recommended Practice J30, “Fuel and Oil Hoses,” June 1998, Docket Identification EPA-HQ-OAR2004-0008-0176. 

198. SAE Surface Vehicle Standard, “Marine Fuel Hoses,” Society of Automotive Engineers J 1527, Issued 1985-

12, Revised 2007-01. 

199. American Society for Testing and Materials, “Standard Test Method for Rubber Property–Effects of Liquids,” 

ASTM D 471-06, November 2006, Docket Identification EPA-HQ-OAR-2004-0008-0511. 

5-137 
Final Regulatory Impact Analysis 

200. SAE Recommended Practice J1737, “Test Procedure to Determine the Hydrocarbon Losses from Fuel Tubes, 

Hoses, Fittings, and Fuel Line Assemblies by Recirculation,”1997, Docket Identification EPA-HQ-OAR-2004-0008-

0178. 

201. SAE Surface Vehicle Standard, “Nonmetallic Fuel System Tubing with One or More Layers,” Society of 

Automotive Engineers J 2260, Issued 1996-11, Docket Identification EPA-HQ-OAR-2004-0008-0180. 

202. SAE Surface Vehicle Recommended Practice, “Test Procedure to Determine the Hydrocarbon Losses from 

Fuel Tubes, Hoses, Fittings, and Fuel Line Assemblies by Recirculation,” Society of Automotive Engineers J 1737, 

Issued 1997-08, Docket Identification EPA-HQ-OAR-2004-0008-0178. 

203. Draft SAE Information Report J1769, “Test Protocol for Evaluation of Long Term Permeation Barrier 

Durability on Non-Metallic Fuel Tanks,” Docket Identification EPA-HQ-OAR-2004-0008-0195. 

204. Nulman, M., Olejnik, A., Samus, M., Fead, E., Rossi, G., “Fuel Permeation Performance of Polymeric 

Materials,” SAE Paper 2001-01-1999, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0162. 

205. “Permeation Rates of Small Off Road Engine High-Density Polyethylene Fuel Tanks (April 2001 Testing), 

June 8, 2001, California Air Resources Board, Docket Identification EPA-HQ-OAR-2004-0008-0146. 

206. “Permeation Rates of High-Density Polyethylene Fuel Tanks (June 2001), June 12, 2001, California Air 

Resources Board, Docket Identification EPA-HQ-OAR-2004-0008-0148 

207. “Permeation Rates of High-Density Polyethylene Fuel Tanks (May 2001), June 11, 2001, California Air 

Resources Board, Docket Identification EPA-HQ-OAR-2004-0008-0149. 

208. “Average Permeation Rates of High-Density Polyethylene Off-Road Equipment Fuel Tanks Using a Surface 

Area Approach, (March 2002),” March 15, 2002, California Air Resources Board, Docket Identification EPA-HQOAR-2004-0008-0256. 

209. Haskew, H., McClement, D., “Fuel Permeation from Automotive Systems; Final Report,” prepared for the 

California Air Resources Board and the Coordinating Research Council, CRC Project No. E-65, September 2004, 

Docket Identification EPA-HQ-OAR-2004-0008-0151. 

210. Dickson, A., Goyet, C., “Handbook of Methods for the Analysis of the Various Parameters of the Carbon 

Dioxide System in Sea Water; Version 2,” Prepared for the U.S. Department of Energy, SOP21 “Applying air 

buoyancy corrections,” September 29, 1997, Docket Identification EPA-HQ-OAR-2004-0008-0135. 

211. Testing Services Group, “CARB TM-513: Portable Fuel Container Permeation Testing,” Presented to U.S. 

EPA on August 18, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0133. 

212. Testing Services Group, “Technical Brief: Buoyancy Correction for Mass Measurement of Fuel Containers,” 

TB 50819-1, August 19, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0134. 

213. California Air Resources Board, “TP-502: Test Procedure for Determining Diurnal Emissions from Portable 

Fuel Containers,” proposed July 22, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0300. 

214. “Test Method to Measure Fluid Permeation of Polymeric Materials by Speciation,” SAE Surface Vehicle 

Standard J2659, Issued December 2003, Docket Identification EPA-HQ-OAR-2004-0008-0512. 

215. Internal MeadWestvaco memorandum from M. Tschantz to C. Pierson, “Preliminary 3 mm SeaGuardTM 

Specifications,” August 31, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0136. 

5-138 
Feasibility of Evaporative Emission Control 

216. “Standard Test Method for Determination of Butane Working Capacity of Activated Carbon,” ASTM 

International, Designation D5228-92 (Reapproved 2005), Docket Identification EPA-HQ-OAR-2004-0008-0347. 

217. Tschantz, M., “Activated Carbon for Use in Marine Evaporative Control Applications,” Presented by 

MeadWestvaco Corporation at the 2004 International Boatbuilders Exposition, October 25, 2004, Docket 

Identification EPA-HQ-OAR-2004-0008-0040. 

218. "Carbon Specs," email from M. Tschantz , MeadWestvaco to M. Samulski, U.S. EPA, November 18, 2005, 

Docket Identification EPA-HQ-OAR-2004-0008-0421. 

219. “Standard Test Method for Ball-Pan Hardness of Activated Carbon,” ASTM International, Designation D3802-

79 (Reapproved 2005), Docket Identification EPA-HQ-OAR-2004-0008-0348. 

220. “SOP 0960-610 vs. ASTM 3802,” email from Mike Tschantz, MeadWestvaco to Mike Samulski, U.S. EPA, 

January 13, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0412. 

221. “ Standard Test Method for Particle Size Distribution of Granular Activated Carbon,” ASTM International, 

Designation D2862-97 (Reapproved 2004). 

222. Williams, R., Clontz, R., “Impact and Control of Canister Bleed Emissions,” SAE Paper 2001-01-0733, 2001, 

Docket Identification EPA-HQ-OAR-2004-0008-0432. 

223. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower,” U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

224. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower,” U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

225. Hopf, G., Ries, H., Gray, E., “Development of Multilayer Thermoplastic Fuel Lines with Improved Barrier 

Properties,” SAE Paper 940165, 1994, Docket Identification EPA-HQ-OAR-2004-0008-0174. 

226. Stahl, W., Stevens, R., “Fuel-Alcohol Permeation Rates of Fluoroelastomers, Fluoroplastics, and Other Fuel 

Resistant Materials,” SAE Paper 920163, 1992, Docket Identification EPA-HQ-OAR-2004-0008-0171. 

227. “Visit to Dyneon on June 12, 2002,” Memorandum from Mike Samulski, U.S. EPA to Docket A-2000-01, June 

17, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0208. 

228. Goldsberry, D., “Fuel Hose Permeation of Fluoropolymers,” SAE Paper 930992, 1993, Docket Identification 

EPA-HQ-OAR-2004-0008-0173. 

229. Tuckner, P., Baker, J., “Fuel Permeation Testing Using Gravimetric Methods,” SAE Paper 20001-01-1096, 

2000, Docket Identification EPA-HQ-OAR-2004-0008-0160. 

230. Fuller, R., “Unique Low Permeation Elastomeric Laminates for Fuel Hose; F200 Technology used in 

Automotive Fuel Hose,” Hearing Testimony for Dupont-Dow Elastomers on NPRM, October 7, 2002, Docket 

Identification EPA-HQ-OAR-2004-0008-0197. 

231. Nulman, M., Olejnik, A., Samus, M., Fead, E., Rossi, G., “Fuel Permeation Performance of Polymeric 

Materials,” SAE Paper 2001-01-1999, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0162. 

5-139 
Final Regulatory Impact Analysis 

232. Duchesne, D., Hull, D., Molnar, A., “THV Fluorothermoplastics in Automotive Fuel Management Systems,” 

SAE Paper 1999-01-0379, 1999, Docket Identification EPA-HQ-OAR-2004-0008-0159. 

233. Nulman, M., Olejnik, A., Samus, M., Fead, E., Rossi, G., “Fuel Permeation Performance of Polymeric 

Materials,” SAE Paper 2001-01-1999, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0162. 

234. Nulman, M., Olejnik, A., Samus, M., Fead, E., Rossi, G., “Fuel Permeation Performance of Polymeric 

Materials,” SAE Paper 2001-01-1999, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0162. 

235. “Visit to Dyneon on June 12, 2002,” Memorandum from Mike Samulski, U.S. EPA to Docket A-2000-01, June 

17, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0208. 

236. Facsimile from Bob Hazekamp, Top Dog Systems, to Mike Samulski, U.S. EPA, “Permeation of Polyurethane 

versus THV Materials @ 60°C,” January 14, 2002, Docket A-2000-01, Docket Identification EPA-HQ-OAR-2004-

0008-0435. 

237. Duchesne, D., Hull, D., Molnar, A., “THV Fluorothermoplastics in Automotive Fuel Management Systems,” 

SAE Paper 1999-01-0379, 1999, Docket Identification EPA-HQ-OAR-2004-0008-0159. 

5-140 
Costs of Control 

CHAPTER 6: Costs of Control 

This chapter describes our approach to estimating the cost of complying with the new 

emission standards. We start with a general description of the approach used to estimate costs, 

then describe the technology changes we expect and assign costs to them. We also present an 

analysis of the estimated aggregate cost to society. 

6.1 Methodology 

We developed the costs for individual technologies using estimates from ICF 

Incorporated1, conversations with manufacturers, and other information as cited below. The 

technology characterization reflects our current best judgment based on EPA’s technology 

demonstrations, engineering analysis, information from manufacturers, and the published 

literature. 

Costs of control include variable costs (for incremental hardware costs, assembly costs, 

and associated markups) and fixed costs (for tooling, R&D, and certification). Variable costs are 

marked up at a rate of 29 percent to account for the engine or equipment/vessel manufacturers' 

overhead and profit.2

 For technologies sold by a supplier to the engine manufacturers, an 

additional 29 percent markup is included for the supplier's overhead and profit. Labor estimates 

are marked up by 100 percent to reflect fringe and overhead charges including management, 

supervision, general and administrative expenses, etc. All costs are in 2005 dollars. 

The analysis presents an estimate of per-unit costs that will occur in the first year(s) of 

new emission standards and the corresponding long-term costs. Long-term costs decrease due to 

two principal factors. First, fixed costs are assessed for five years, after which they are fully 

amortized and are then no longer part of the cost calculation. Second, manufacturers are 

expected to learn over time to produce the engines with the new technologies or aftertreatment at 

a lower cost. Consistent with analyses from other programs, we reduce estimated variable costs 

by 20 percent beginning with the sixth year of production.3

 The small spark ignited engine 

industry and the marine industry have different reasons for the learning. 

Learning for the Small SI industry is expected to occur in the catalyst muffler designs. It 

will likely occur for two reasons: 1) over time the number of different muffler catalyst designs 

may be reduced thereby decreasing substrate costs due to larger ordering volumes. 2) heat shield 

manufacturing may become automated and/or designs more uniform. Learning will not occur for 

other technologies such as electronic fuel injection systems for they currently exist on some 

Small SI equipment and motorized vehicles such as scooters . 

In the marine industry, manufacturers are less likely to put in the extra R&D effort for 

low-cost manufacturing of engine families of relatively low sales volumes. Learning will occur 

in two basic ways. As manufacturers produce more units, they will make improvements in 

production methods to improve efficiency. The second way learning occurs is materials learning 

where manufacturers reduce scrap. Scrap includes units that are produced but rejected due to 

6-1 
Final Regulatory Impact Analysis 

inadequate quality and material scrap left over from the manufacturing process. As production 

starts, assemblers and production engineers will then be expected to find significant 

improvements in fine-tuning the designs and production processes. 

We believe it is appropriate to apply this learning factor here for the marine industries, 

given that they are facing new emission regulations, some for the first time, and it is reasonable 

to expect learning to occur with the experience of producing and improving emission-control 

technologies. Manufacturers do not have significant experience with most of the emissions 

controls that are anticipated for meeting the standards. 

Many of the engine technologies available to Marine SI and Small SI engine 

manufacturers to control emissions also have the potential to significantly improve engine 

performance. This is clear from the improvements in automotive technologies. As cars have 

continually improved emission controls, they have also greatly improved fuel economy, 

reliability, power, and a reduced reliance on regular maintenance. Similarly, the fuel economy 

improvements associated with converting from two-stroke to four-stroke engines is well 

understood. We attempt to quantify these expected improvements for each type of engine below. 

Even though the analysis does not reflect all the possible technology variations and 

options that are available to engine manufacturers, we believe the projections presented here 

provide a cost estimate representative of the different approaches manufacturers may ultimately 

take. We expect manufacturers in many cases to find and develop approaches to achieve the 

emission standards at a lower cost than we describe in this analysis. 

6.2 Exhaust Emission Control Costs for Small SI Engines 

This section presents our cost estimates for meeting the new exhaust emission standards 

for Small land-based spark-ignition (Small SI) engines. EPA has relied upon model year 2008 

certification data for this analysis to characterize the current Class I and Class II market and the 

technology mix needed to comply with the Phase 3 standards. EPA chose not include data from 

Chinese manufacturers in this analysis because we have no information on actual sales of their 

engines in the United States. Manufacturers do submit sales estimates to EPA at the time of 

certification. However, the sales estimates provided by Chinese manufacturers would suggest 

that sales of Small SI nonhandheld engines have doubled over the last few years. Based on 

discussions with nonhandheld engine manufacturers that have been certifying with EPA for over 

ten years now, we do not believe this is the case and it is our understanding that sales of 

nonhandheld engines from Chinese manufacturers are relatively small at this time. Therefore, 

we believe it is appropriate to not include certification data from Chinese manufacturers in our 

analysis. 

In 1995, EPA finalized the first regulations for reducing emissions from small spark 

ignited (SI) engines <19kW. Small spark ignited engine designs include side valve and overhead 

valve engine configurations designated in two groups by engine displacement. Class I engines 

are <225cc and Class II engines are >225cc and less than 19kW. The Phase 2 regulations for 

these engines were set with the expectation that Class I side valve engines would be converted to 

6-2 
Costs of Control 

overhead valve design. Certification data from 2008 shows that engine manufacturers have been 

able to achieve Phase 2 certification with the continued use of side valve engines in some cases. 

A summary of the 2008 technology market mix is presented in Table 6.2-1. 

For the final Phase 3 standards, the EPA 2008 certification database was referenced. It 

was found that the majority of Class I engines were in need of some emission reduction and 

therefore it is estimated that these engines would use catalysts and the related engine design 

improvements required to use catalysts safely. For Class II engines, the 2008 certification 

database revealed some engine families meet the Phase 3 emission levels and therefore 

technologies are not required on all engine families. For those engine families needing emission 

reduction technology, different technologies were assigned depending on whether the engine was 

a one cylinder or a multiple cylinder engine. A number of one cylinder engine families were 

estimated to use catalysts. For two or more cylinders, the largest engine family per engine 

manufacturer needing emission reduction technology was assigned closed loop electronic fuel 

injection. The remainder were assigned catalysts with the appropriate muffler setup. The 

expected technology market mix is presented in Table 6.2-2. 

Table 6.2-1: 2008 Technology Market Mix 

Class I Class II 

SV 66% 2% 

OHV 34% 98% 

w/ Catalyst 0.003% 0.4% 

w/ Other (EFI and/or watercooled) 0 1% 

Table 6.2-2: Technology Market Mix Expectations for Phase 3 Engines 

HC+NOx Emission Standards: 38% Reduction Class I, 34% Reduction Class II* 

Exhaust Standard Implementation Date 2012 

Class I 

2011 

Class II 

SV 66% 2% 

OHV 34% 98% 

w/ Catalyst 95% 50% 

w/ Other (EFI and/or watercooled) 0 6.6% 

*EPA 2008 certification data

 The following sections describe the technologies and related variable and fixed costs 

followed by an analysis of aggregate costs. The costs are based on a report from ICF 

International entitled “Small SI engine Technologies and Costs.”4 Variable costs to the 

manufacturers vary with the engine size and the emission technologies considered. 

6-3 
Final Regulatory Impact Analysis 

Manufacturers prices of all components were estimated from various sources including 

information from engine and catalyst manufacturers and previous work performed by ICF 

International on spark ignited engine technology. All hardware costs to the engine 

manufacturers are subject to a 29 percent mark-up. This includes manufacturer overhead, profit, 

dealer overhead and profit. A separate supplier markup of 29 percent is also applied to items 

typically purchased from a suppliers such as fuel injection and catalysts. A 5 percent warranty 

mark-up is added to hardware cost of specific technologies including electronics, to represent an 

overhead charge covering warranty claims associated with new parts. 

Fixed costs to the manufacturer include the cost of researching, developing and testing a 

new technology. The cost of retooling the assembly line for the production of new parts as well 

as engine certification including durability testing are also fixed costs. Design and 

development fixed costs per month are listed in Table 6.2-3. Tooling and specific R&D costs are 

listed in the following sections. Fixed costs for certification are listed in Section 6.2.3. 

Table 6.2-3: Design and Development Costs 

for use in Fixed Cost Estimates per Month 5 

Hours Rates Costs 

Design Costs Per Month 

Engineer 160 $64.41 $10,306 

TOTAL Design Costs Per Month $10,306 

Development Costs Per Month 

Engineer 160 $64.41 $10,306 

Technicians 320 $41.87 $13,398 

Dynamometer Test 

Time 

20 tests $250 ea $5,000 

TOTAL Development Costs Per Month $28,704 

6.2.1 Class I 

Class I engines currently emitting at or below the Phase 2 emission standard of 16.1 

g/kWh will need to reduce their engine out HC+NOx emissions by 30-50 percent to comply with 

the Phase 3 emission standard of 10 g/kWh with an appropriate margin. A number of Class I 

side valve (SV) engines have been redesigned for the Phase 1 and Phase 2 rulemakings, however 

SV and overhead valve (OHV) engines will need a different approach to meet these emission 

standards. One technology to reduce emissions to the Phase 3 levels is a three way catalyst with 

appropriate precious metal loading for minimal CO conversion. EPA work has shown that 

catalysts can function effectively through a dynamometer aging of 125 hours with a catalyst 

conversion of about the same amount at high hours as low hours6

. The amount of conversion is 

6-4 
Costs of Control 

only constrained by 1) the size of the catalyst to fit in the existing, or slightly larger, muffler, 2) 

residence time of the exhaust gas along with 3) muffler surface and exhaust gas temperature 

issues with respect to the amount of CO converted within a catalyst. EPA’s work has been 

shown to convert HC+NOx within a range of 3.8-6.7 g/kW-h (median approx 5.7g/kW-h) on 

OHV engines and 3.8-10.3 g/kW-h on SV engines (median of 6.8 g/kW-h). 

EPA’s 2005 Phase 2 certification database lists OHV and SV engine HC+NOx emission 

levels at low hours, a deterioration factor (df) and resultant certification levels. Engine 

manufacturers with most regulated experience were considered for these df ranges for we are 

most familiar with the performance of these engines. Engine families using credits to certify to 

the emission standard with ABT were not included. 

Table 6.2-4: 2005 EPA Certification Database with Catalyst Assumptions7 

Technology 

Type/UL 

Engine Out 

“zero 

hours” 

(Min-Max) 

DF 

(Min-Max) 

Certification 

Level 

(Min-Max) 

Catalyst 

conversion 

(median 

from EPA 

work) 

Engine with Catalyst 

SV/125 10-11 1-1.24 13-14 6.8 6.2-7.2 

OHV/125 6-15 1-1.356 9-16 5.7 3.3-10.3 

OHV/250 7-15 1-1.136 8-12 5.7 2.3-6.3 

OHV/500 8-14 1-1.161 8-15 5.7 2.3-9.3 

Table 6.2-4 is based on median HC+NOx catalyst conversion from EPA test work in the 

Safety Study.8 The Safety Study also shows improvements in the cooling system design will 

provide cooling to the engine and/or catalyst muffler system for reduced muffler skin 

temperatures. Individual engine family applications will vary and engine improvements may be 

required for durable and effective catalyst operation. 

6.2.1.1 Engine Improvements for Class I

 Improvements in engine combustion efficiency and engine cooling will assure the engine 

systems support catalyst durability. Engine improvements for durable catalyst operation include 

changes that are fixed costs and variable costs. Improvements in engine systems resulting in 

fixed costs potentially include the following: 1) improved combustion chamber design for 

optimized combustion, 2) improved piston design for reduced crevice volumes and reduced HC 

emissions, 3) improved machining and casting tolerances for all combustion chamber 

components, 4) improved cylinder head fin design for improved cooling, and 5) improved 

carburetion for fuel delivery and system durability. Some engines would also benefit greatly 

from 6) improved flywheel design in order to provide additional cooling to the engine and 

muffler system. Clearly not all engines need these upgrades and many will implement few or 

6-5 
Final Regulatory Impact Analysis 

none.

 Fixed costs per engine family for engine improvements are estimated at four months of design 

work (one engineer) and six months of development work (one engineer, one technician and 

dynamometer test time) along with tooling costs for the cylinder head, piston, connecting rod, 

camshaft, carburetor, flywheel and setup changes. Tooling costs are estimated to be the same 

across engine useful life categories with the exception of Class I 125 hour SV engines which 

contains some engine families that are sold in much larger volumes and therefore would have 

more tools to be modified. These fixed costs are presented in Table 6.2-5. 

Table 6.2-5: Fixed Costs for Engine Improvements for Class I9 

Engine Class Class I 

Useful life (hrs) 125 125,250,500 

Valving SV OHV 

R&D 

Design (4 months) 41,225 41,225 

Development (6 months) 172,225 172,225 

TOTAL R&D per Engine Line 213,450 213,450 

TOOLING COSTS 

Cylinder Head 50,000 25,000 

Piston 50,000 25,000 

Connecting Rod 30,000 15,000 

Camshaft 16,000 8,000 

Carburetor 120,000 60,000 

Flywheel 70,000 35,000 

Setup Changes 150,000 75,000 

TOTAL TOOLING per Engine Line 486,000 243,000 

TOTAL FIXED $699,450 $456,450 

Variable cost items were identified from EPA field aging of engines from several engine 

manufacturers. EPA performed several lawnmower in-use test programs in 2003 to 2005. 

Several of the SV and OHV engines were equipped with catalysts. The process revealed that 

potentially several engine design characteristics needed improvement in some cases in order for 

catalysts to be successfully applied in-use. Items included: 1) fuel filter to screen out impurities 

(assure do not encounter a stuck float and thereby excessive fuel flowed through the engine 

6-6 
Costs of Control 

coating the catalyst and rendering it inactive.), 2) incorporation of an intake gasket to assure 

leaks do not develop in the intake system thereby resulting in hot engine operation and a number 

of engine operational issues, 3) engine shroud screen over fan (avoid debris collecting in the 

engine fan), and 4) improved engine cooling system for SV engines to assure the engine’s piston 

and combustion chamber walls stay in contact so oil does not seep past the rings and into the 

combustion chamber (see Chapter 4) thereby potentially poisoning the catalyst. Lastly, the 

incorporation of improved induction coils will reduce the opportunity for spark plug wire 

failures and misfire events. Table 6.2-6 lists the variable costs for engine improvements for 

Class I engines certified to various useful lives. Clearly not all engines need these upgrades to 

succeed and many will implement few or none. 

Table 6.2-6: Variable Costs for Engine Improvements for Class I10 

Engine Improvement UL 125 

SV 

UL 125 

OHV 

UL 250 UL 500 

Fuel Filter Screens (80% of engine sales) 

cost/engine: 0.02 

0.02 0.02 0.02 --

Improved Intake Gaskets (75% of engine sales for 

Class I 125 hour useful life) 

cost/engine: 0.03 

0.02 -- -- --

Screen over cooling fan (16% of 125 hr Class I) 

cost/engine: 0.45 

0.07 0.07 -- --

Larger Induction Coils (all) 0.10 0.10 0.10 0.10 

Engine Manufacturer Cost 0.21 0.19 0.12 0.10 

TOTAL w/Markup 

29% OEM 

0.27 0.24 0.15 0.13 

Learning Curve w/ 29% Markup 

(0.8*Total w/Markup)*1.29 

0.22 0.19 0.12 0.10 

6.2.1.2 Catalysts for Class I

 The following paragraphs describe details on catalysts substrates, washcoat and precious 

metal, and muffler shielding for Class I engines. Although commonly in use today, spark 

arresters are discussed in the context of the overall design. 

Based on catalyst/muffler development and emission testing by EPA (2004-2005), an 

engine which has an HC+NOx exhaust ratio of 60/40 is best suited for the use of a catalyst in 

Small SI engines for the catalyst can be designed for minimal CO oxidation and related heat 

generation. This ratio can be found on OHV engines for they have efficient combustion 

chambers. SV engines require slightly larger catalysts due to their less efficient combustion 

chambers and less than optimum HC/NOx ratios. In addition, SV engines are more likely to 

6-7 
Final Regulatory Impact Analysis 

have oil seep past the piston rings due into the exhaust to cylinder distortion. A longer catalyst, 

or the use of a pipe catalyst prior to the brick catalyst, allows it to survive for the full useful life 

for the catalyst is poisoned from the front of the catalyst to the back. According to the EPA 

Phase 2 certification database, Class I SV engine families are certified to the 125 hour useful life 

and therefore the cost analysis includes two different catalyst costs for the 125 hour useful life. 

The engines certified to the 250 and 500 useful life categories are all of OHV engine 

design. As with the 125 hour category, catalyst substrate sizes are calculated as a percentage of 

the engine displacement. The certification database was queried for this engine displacement 

data and the displacements are sales weighted, as seen in Table 6.2-7. Catalyst volumes range 

from 18 percent of the engine displacement for the 125 OHV useful life to 50 percent of the 

engine displacement for the 500 hour useful life. Larger catalysts are needed for longer useful 

life periods in order to provide the emission conversion durability. Specific costs for engines 

within each useful life category will differ. 

The substrate cost is based on an average cost of metallic and ceramic substrates as 

presented in the ICF report11 due to the variety of Small SI equipment types and variety of 

catalysts offered in the marketplace. This cost analysis estimates equal weighting of the substrate 

types and therefore takes an average of the cost for both metallic and ceramic. 

Due to the concern of oil sulfur poisoning in Class I engines, EPA envisions that a 5:1 

ratio of Platinum/Rhodium precious metal would be used for these catalysts. The cost of 

precious metals was taken from a 3 year average in price from 2003-2005. Washcoat material is 

expected to be a 30/70 percent mixture of cerium and alumina oxide, respectively. 

The design of the catalyst/muffler forms the basis for the degree of cooling needed at the 

muffler and exhaust port. EPA’s solution for muffler surface and exhaust gas cooling included 

three steps 1) forcing the cooling air from the engine fan/cylinder head region to the muffler can 

be achieved through a slight redesign of the engine’s shroud, 2) a muffler shroud that is designed 

to guide the cooling air around the entire muffler and exits at a specified location, and lastly 3) 

and if when needed an ejector is added to the muffler at the exhaust gas outlet so the exhaust gas 

can be combined with ambient air before being accessible to the user. 

EPA’s observation of a number of lawnmower engine designs revealed that the majority 

of heat shields currently used on small engines need to be redesigned in order to allow the use of 

air flow from the engine’s fan to flow optimally around the muffler for cooling. The portion of 

engines that do have such systems and will not incur this cost were removed from the cost 

analysis and ICF’s estimates for this technology were adjusted. EPA utilized the 2005 

certification database to estimate sales and to calculate a percentage of engines that will be 

estimated to redesign their muffler heat shield. Table 6.2-7 contains the variable costs for 

catalysts, heat shields and spark arresters. 

6-8 
Costs of Control 

Table 6.2-7: Variable Catalyst Costs for Class I12 

to Achieve the Phase 3 Standards 

Useful Life UL 125 

SV 

UL 125 

OHV 

UL 250 UL 500 

Engine Power (hp) 3.3 5.1 5.0 5.2 

Engine Displacement (cc) 178 180 167 166 

Catalyst Volume (cc) 45 32 55 83 

Substrate Diameter (cm) 3.50 3.50 4.00 4.50 

Substrate $1.97 $1.53 $2.32 $3.22 

Washcoat and Precious 

Metal 

$1.83 $1.31 $2.81 $4.24 

Labor $1.40 $1.40 $1.40 $1.40 

Labor Overhead 40% $0.56 $0.56 $0.56 $0.56 

Supplier Markup 29% $1.67 $1.39 $2.06 $2.73 

Catalyst Manufacturer Price $7.43 $6.19 $9.15 $12.15 

Heat Shield* $0.50 $0.29 $0.18 $0.14 

Spark Arrestors $0.05 $0.05 $0.05 $0.05 

Engine Manufacturer Cost $7.98 $6.53 $9.38 $12.34 

TOTAL w/Markup 

29% OEM 

$10.29 $8.42 $12.10 $15.92 

* Based on EPA’s work with small engine equipment from 2003-2005, it has been observed that 

some manufacturers have heat shielding that is sufficient or only needs slight modification. 

These sales volumes have been removed and the resultant price recalculated. 

The fixed costs related to catalyst development for Class I engine applications include 

design (one engineer), of two months, and development (one engineer, one technician and 

dynamometer time), for five months, of the muffler and heat shield. The inside of the muffler is 

to be redesigned to house the catalyst, provide supplemental air when needed, and provide 

baffling for the exhaust flow in order to maximize heat dissipation from the exhaust flow. The 

muffler stamping will also need to be updated to account for the new design. A second critical 

component of the catalyst/muffler system is the heat shield. The heat shield must be designed to 

allow cooling air from the fan to flow around the muffler to maximize cooling of the muffler and 

then exit at an optimum point. The muffler/heat shield system must be located at a 

predetermined distance from the engine block in order to allow air to flow behind the muffler to 

cool the backside. Setup changes also are incurred with these modified stampings. The total 

tooling per engine line is estimated at $240,000 for Class I engines of 125 hour useful life and 

6-9 
Final Regulatory Impact Analysis 

$120,000 for Class I engines of other useful life periods. The difference is due to the additional 

tooling for high volume SV engine families. Table 6.2-8 presents the fixed costs associated with 

using catalysts on Class I engines. 

Table 6.2-8: Fixed Costs for Catalysts for Class I Engines13 

Engine Class Class I 

Useful life (hrs) 125 125, 250, 500 

Valving SV OHV 

R&D 

Design 

(2 months) 

20,612 20,612 

Development (5 months) 143,521 143,521 

TOTAL R&D per Engine Line 164,133 164,133 

TOOLING COSTS 

Modified Muffler Stamping 100,000 50,000 

Heat Shield Stamping 60,000 30,000 

Engine Shroud Modification 30,000 15,000 

Setup Changes 50,000 25,000 

TOTAL TOOLING per Engine Line 240,000 120,000 

TOTAL FIXED COSTS $404,133 $284,133 

A learning curve of 20 percent is applied to costs for catalyst technology starting in the 

sixth year after the standard is implemented. This somewhat conservative since the learning 

normally occurs at 20 percent with a doubling of production which would thus be in the third or 

fourth year. Optimized catalyst/muffler designs and manufacturing processes will likely be 

developed as the industry becomes experienced in using mufflers with catalysts on Small SI 

engines. The muffler washcoat will still be unique per engine family per engine manufacturer 

for engine out emissions will differ. Table 6.2-9 presents the estimated learning curve impacts 

on variable costs. The precious metal prices are determined in the marketplace and therefore 

would not be affected by the learning curve. 

6-10 
Costs of Control 

Table 6.2-9: Learning Curve Variable Catalyst Costs for Class I 

to Achieve the Phase 3 Standards 

Useful Life UL 125 

- SV 

UL 125 

- OHV 

UL 250 UL 500 

Engine Power (hp) 3.3 5.1 5.0 5.2 

Engine Displacement (cc) 178 180 167 166 

Catalyst Volume (cc) 45 32 55 83 

Substrate Diameter (cm) 3.50 3.50 4.00 4.50 

Substrate $1.57 $1.22 $1.86 $2.58 

Washcoat and Precious 

Metal 

$1.83 $1.31 $2.81 $4.24 

Labor $1.40 $1.40 $1.40 $1.40 

Labor Overhead $0.56 $0.56 $0.56 $0.56 

Supplier Markup 29% $1.55 $1.30 $1.92 $2.55 

Manufacture Price $6.92 $5.80 $8.55 $11.32 

Heat Shield 

(adjusted % for eng w/ 

sufficient heat shield) 

$0.40 $0.23 $0.14 $0.11 

Flame/Spark Arrester $0.05 $0.05 $0.05 $0.05 

Hardware Cost to 

Manufacturer 

$7.37 $6.08 $8.74 $11.49 

w/Markup 

29% OEM 

$9.50 $7.84 $11.28 $14.82 

Table 6.2-10 contains the estimated total costs for Class I Phase 2 compliant engines to 

meet the Phase 3 emission standards. Near term costs are those costs for the first five years. 

Long term costs are those costs to which the learning curve has been applied. 

6-11 
Final Regulatory Impact Analysis 

Table 6.2-10: Class I Estimated Total Costs Per Engine (Variable) and 

Per Engine Family (Fixed) to Achieve the Phase 3 Standards 

Useful Life UL 125 -

SV 

UL 125 -

OHV 

UL 250 UL 500 

Engine Displacement (cc) 178 180 167 166 

Catalyst Volume (cc) 45 32 55 83 

Substrate Diameter (cm) 3.50 3.50 4.00 4.50 

Variable Costs - Near Term 

Engine Improvements $0.27 $0.24 $0.15 $0.13 

Catalyst $10.29 $8.36 $12.10 $15.92 

Total Variable Cost (Near) $10.56 $8.60 $12.25 $16.05 

Variable Costs - Long Term (with Learning) 

Engine Improvements $0.22 $0.19 $0.12 $0.10 

Catalyst $9.50 $7.84 $11.28 $14.82 

Total Variable Cost (Long) $9.72 $8.04 $11.39 $14.92 

Fixed Costs 

Engine Improvements $699,450 $456,450 $456,450 $456,450 

Catalyst $404,133 $284,133 $284,133 $284,133 

Total Fixed Costs $1,103,583 $740,583 $740,583 $740,583 

6.2.2 Class II 

The Phase 3 HC+NOx emission standard for Class II is 8 g/k-Wh which is a 34 percent 

emission reduction from the Phase 2 standards of 12.1 g/k-Wh. This standard is to be met at the 

end of the regulatory useful life for each engine family. The EPA Phase 2 certification database 

shows that the majority of engines in this Class are of OHV design however, approximately 2 

percent of the engines are still side valve engine technology. 

Class II side valve engines are currently certified to the Phase 2 standards with credits 

from lower emitting OHV engines. The EPA 2005 certification database shows the majority of 

overhead valve engines currently certifying HC+NOx at a range of 7-11 g/kW-h and side valve 

engines certifying in the range of 13-14 g/kW-h. Lowering of the emission standard will reduce 

the number of emission credits available for side valves to certify and therefore, it is assumed 

that the remaining side valve engines will be phased out and replaced with currently produced 

overhead valve engines or continue to be certified using ABT credits from a limited number of 

6-12 
Costs of Control 

lower emitting engine families. 

Assuming a 2 g/kW-h compliance margin to 6 g/kW-h, emission reduction technologies 

will need to be designed to reduce emissions 15-57 percent. Table 6.2-11 illustrates potential 

engine out emissions with emission reduction technologies applied to Phase 2 engines. OHV 

engines are expected to potentially include some engine improvements and/or catalysts or 

electronic fuel injection. 

Table 6.2-11: 2005 EPA Certification Database Summary With Catalyst Assumptions14 

UL 

OHV 

Engine Out 

“zero hours” 

(Min-Max)* 

DF 

(Min-Max)** 

Certification 

Level 

(Min-Max)* 

Catalyst 

conversion 

(non-EFI 

engine)15 

Engine with Catalyst 

(Based on Median 

values) 

250 4.8-10.0 

Median: 7.9 

1-1.7 

Median: 1.137 

6.7-12.0 

Median: 8.9 

4.0 2.7-8.0 

500 4.4-10.8 

Median: 8.3 

1-1.6 

Median: 1.039 

5.9-10.9 

Median: 9.5 

4.0 1.9-6.9 

1000 6.0-11.2 

Median: 8.4 

1-1.4 

Median: 1.03 

6.9-11.2 

Median: 8.9 

4.0 2.9-7.2 

* Values of engines that meet the standard. 500 hr UL has a liquid cooled engine with catalyst that meets 

a 2.6 g/kW-h HC+NOx and 1000 hr UL has the same that meets 1.8 g/kW-h HC+NOx. 

**Some engines have catalysts and therefore claim a higher df 

Class II contains several liquid cooled engines. These engines likely have the ability to 

be enleaned to more of a degree due to the additional cooling assistance and therefore may not 

need a catalyst to meet the Phase 3 emission standards. 

6.2.2.1 Engine Improvements for Class II 

Engine improvements include improved engine design and larger induction coils as 

shown in Tables 6.2-12 and 6.2-13. Improvements in engine design will allow for more efficient 

combustion and a more favorable HC:NOx ratio for the use of a reducing catalyst. A larger 

induction coil will reduce the opportunity for spark plug wire failure and misfire events. It is 

estimated that 1000 hour engines currently have sufficient induction coils and will not need this 

improvement. 

6-13 
Final Regulatory Impact Analysis 

Table 6.2-12: Variable Costs for 

Engine Improvements for Class II per Engine16 

UL250 UL 500 UL 1000 

Larger Induction Coils 0.09 0.09 --

TOTAL 

w/Markup 29% OEM 

0.12 0.12 --

Learning w/29% OEM 

(0.8*Total)*1.29 

0.10 0.10 --

Improved engine design includes machining and casting tolerances, improved 

combustion chamber configuration, reduced crevice volumes, better cooling (improved fin 

design on cylinder head and oil control), improved flywheel design and improved carburetion. 

Better carburetor performance is needed to assure floats do not stick and better cooling so 

engines operate at cooler temperatures. Fixed costs include design (one engineer at 4 months), 

development and tooling costs (one engineer, one technician and dynamometer time for 6 

months) per engine family to achieve improved engine design. Projected fixed costs are 

presented in Table 6.2-13. The fixed cost is estimated to be the same per engine family and is 

estimated at $456,450. 

6-14 
Costs of Control 

Table 6.2-13: Fixed Costs for 

Engine Improvements for Class II per Engine Family17 

Engine Class Class II 

Useful life (hrs) 250,500,1000 

Valving OHV 

R&D 

Design (4 months) 41,225 

Development (6 months) 172,225 

TOTAL R&D per Engine Line 213,450 

TOOLING COSTS 

Cylinder Head 25,000 

Piston 25,000 

Connecting Rod 15,000 

Camshaft 8,000 

Carburetor 60,000 

Flywheel 35,000 

Setup Changes 75,000 

TOTAL TOOLING per Engine Line $243,000 

TOTAL FIXED $456,450 

6.2.2.2 Catalysts for Class II 

Further emission reduction can be achieved through the use of catalysts. The catalyst 

must be designed for durability throughout the engine’s regulatory useful life. A catalyst 

efficiency of 25-45 percent is estimated for these engines. The catalyst technology that would 

be utilized would be similar to that used for Class I engines. The exceptions include: 1) Class II 

engines would not use supplemental air because the HC and NOx ratios are more favorable in 

Class II OHV engines due to their more efficient combustion chamber and larger displacement 

and horsepower, and 2) the precious metals in the catalysts range from 

platinum/palladium/rhodium for 250 and 500 hour Class II engines to to palladium/rhodium 

(5:1) for 1000 hour regulatory useful life engines. 

Class II engine designs include engines 1 to 4 cylinders. Engines with two or more 

cylinders have specific issues to be considered in terms of safety with regard to engine exhaust 

and catalyst use and this will be addressed towards the end of this section. The variable costs for 

6-15 
Final Regulatory Impact Analysis 

catalysts of single cylinder engines are listed in Table 6.2-14. The catalyst substrate size is 

calculated based on the engine displacement size. To utilize one value per regulatory useful life 

category for this analysis, the engine horsepower and displacements were sales weighted with 

values from the 2005 EPA certification database information. Catalyst volumes range from 33 

percent of the engine displacement for the 250 useful life to 50 percent of the engine 

displacement for the 1000 hour useful life. Larger catalysts are needed for longer useful life 

periods in order to provide the emission conversion durability. 

Catalyst substrate and heat shield variable costs will be decreased in the sixth year with a 

learning curve of 20 percent. This somewhat conservative since the learning normally occurs at 

20 percent with a doubling of production which would be in the third or fourth year. Optimized 

catalyst/muffler designs and heat shield manufacturing processes will likely be developed as the 

industry becomes experienced in application of the catalyst technology across their product line. 

The muffler washcoat will likely still be unique per engine family per engine manufacturer and 

therefore it is estimated there will likely not be a one size fits all catalyst/muffler design. The 

precious metal prices are determined in the marketplace and therefore are not discounted over 

time. 

6-16 
Costs of Control 

Table 6.2-14: Variable Catalyst Costs for Class II OHV Single Cylinder Engine 

HC+NOx Emission Reduction to Phase 3 Standards 

Near Term Estimates Learning Curve Estimates 

Useful Life 250 500 1000 250 500 1000 

Engine Power (hp) 11.3 11.1 9.5 11.3 11.1 9.5 

Engine Displacement (cc) 406 338 329 406 338 329 

Catalyst Volume (cc) 134 135 165 134 135 165 

Substrate Diameter (cm) 5.25 6.00 7.00 5.25 6.00 7.00 

Substrate* $4.78 $4.81 $5.67 $3.82 $3.84 $4.53 

Washcoat and Precious Metal $4.03 $2.73 $4.10 $4.03 $2.73 $4.10 

Labor $1.40 $1.40 $1.40 $1.40 $1.40 $1.40 

Labor Overhead 40% $0.56 $0.56 $0.56 $0.56 $0.56 $0.56 

Supplier Markup 29% $3.12 $2.75 $3.40 $2.84 $2.47 $3.07 

Manufacture Price $13.89 $12.25 $15.13 $12.65 $11.00 $13.66 

Heat Shield $4.23 $3.96 $4.05 $3.38 $3.17 $3.24 

Spark Arrestor $0.10 $0.05 $0.05 $0.10 $0.05 $0.05 

Hardware Cost to Manufacturer $18.22 $16.26 $19.23 $16.14 $14.23 $16.95 

w/Markup 29% OEM $23.50 $20.97 $24.80 $20.82 $18.35 $21.87 

* 50/50- split of metallic vs ceramic substrates 

Fixed costs involve modification to the existing heat shield and cooling system. If the 

muffler is in close proximity to the engine fan then cost for a heat shield can also be included 

because in some cases the heat shields will need to be improved in order to direct cooling air 

from the engine’s flywheel over the muffler for muffler cooling. These fixed costs are presented 

in Table 6.2-15. 

6-17 
Final Regulatory Impact Analysis 

Table 6.2-15: Fixed Costs for Class II OHV Single Cylinder Engine 

Engine Class II 

Useful life (hrs) 125, 250, 500 

Valving OHV 

R&D 

Design 

(2 months) 

20,612 

Development (5 months) 143,521 

TOTAL R&D per Engine Line 164,133 

TOOLING COSTS 

Modified Muffler Stamping 50,000 

Heat Shield Stamping 30,000 

Engine Shroud Modification 15,000 

Setup Changes 25,000 

TOTAL TOOLING per Engine Line 120,000 

TOTAL FIXED COSTS $284,133 

Carbureted V-Twins 

Carbureted engines with more than one cylinder, ex: V-twins or more, have special 

concerns when considering the use of catalyst application. Multi-cylinder engines may continue 

to run if one cylinder misfires or does not fire at all. If this occurs, the results is raw unburned 

fuel and air from one cylinder and hot exhaust gases from the other cylinder combining in the 

muffler. In a catalyst muffler, this condition will likely result in continuous backfire which 

would create high temperatures within the muffler and potentially destroy the catalyst. One 

solution is to have separate catalyst mufflers for each cylinder. The two cylinders in the V-twins 

currently share one muffler. If two mufflers are used, then the individual mufflers would likely 

need to be slightly larger. Each individual muffler would need to be 25-30 percent larger than 

one half the volume of the original. Since the two cylinders in the V-twins currently share one 

muffler one option for consideration would be to package the two catalysts in separate chambers 

within one larger muffler. 

Costs for this new muffler design are listed in Tables 6.2-16 and 6.2-17. V-twin engines 

from EPA’s certification database were sales weighted for power and engine displacement per 

regulatory useful life. ICF provided the estimates for existing muffler costs and new muffler 

cost estimates.18 

6-18 
Costs of Control 

Table 6.2-16: Variable Costs for Change to Two Mufflers for V-Twins19 

250 OHV 500 OHV 1000 OHV 

Engine Power (hp) 16.3 20.1 17.1 

Engine Displacement - Total (cc) 605 632 627 

Per Cylinder Displacement (cc) 393 411 408 

Current Muffler Cost ($20.24) ($23.13) ($22.57) 

New Muffler Cost (includes 2) $26.31 $30.07 $29.34 

Hardware Cost to Manufacturer $6.07 $6.94 $6.77 

OEM Markup @ 29% $1.76 $2.01 $1.96 

Total Component Costs $7.83 $8.95 $8.73 

Fixed costs include modified muffler stamping, exhaust pipe changes and setup changes. 

These costs are estimated at $100,000 per engine family. Special considerations were not 

accounted for in the case where OEM’s obtain their own muffler and assemble the muffler onto 

the engine once the engine is received from the engine manufacturer. This analysis considers 

that in most cases equipment manufacturers would buy their catalyst mufflers from the engine 

manufacturer in order to avoid engine certification. 

Table 6.2-17: Fixed Costs for Change to Two Mufflers for V-Twins20 

250 OHV 500 OHV 1000 OHV 

Engine Power 16.3hp 20.1hp 17.1hp 

Engine Displacement - Total (cc) 605 632 627 

Per Cylinder Displacement 393 411 408 

Modified Muffler Stamping $50,000 $50,000 $50,000 

Exhaust Pipe Changes $25,000 $25,000 $25,000 

Setup Changes $25,000 $25,000 $25,000 

Total Tooling per Engine Line $100,000 $100,000 $100,000 

In this analysis, catalyst sizes are related to the engine cylinder size and therefore since 

cylinders of V-twin engines are smaller than one cylinder Class II engines, costs are recalculated 

from Table 6.2-14. Note that one catalyst is used in each muffler for a total of two catalysts. 

Tables 6.2-18 and 6.2-19 present the projected variable and fixed catalyst costs for Class II OHV 

V-twin engines. 

6-19 
Final Regulatory Impact Analysis 

Table 6.2-18: Variable Catalyst Costs for Class II OHV V-Twin Engine, 

Near Term and Learning Curve Effect 

Near Term Costs Learning Curve Effect 

Useful Life 250 500 1000 250 500 1000 

Engine Power (hp) 16.3 21.0 17.1 16.3 21.0 17.1 

Engine Displacement per Cylinder 303 316 314 303 316 314 

Catalyst Volume (cc) 100 126 157 100 126 157 

Substrate Diameter (cm) 5.00 5.00 5.50 5.00 5.00 5.50 

Substrate* $3.74 $4.55 $5.44 $2.99 $3.64 $4.35 

Washcoat and Precious Metal $3.00 $2.55 $3.91 $3.00 $2.55 $3.91 

Labor $1.40 $1.40 $1.40 $1.40 $1.40 $1.40 

Labor Overhead 40% $0.56 $0.56 $0.56 $0.56 $0.56 $0.56 

Supplier Markup 29% $2.52 $2.63 $3.28 $2.31 $2.36 $2.96 

Manufacture Price per Catalyst $11.22 $11.68 $14.59 $10.26 $10.51 $13.19 

Two Catalysts ($x2) $22.45 $23.36 $29.18 $20.52 $21.02 $26.37 

Heat Shield (2) $8.53 $9.76 $10.50 $6.82 $7.81 $8.4 

Spark Arrestor (2) $0.20 $0.10 $0.10 $0.20 $O.10 $0.1 

Hardware Cost to Manufacturer $31.18 $33.22 $39.79 $27.54 $28.92 $34.87 

Markup 

29% OEM 

$9.04 $9.63 $11.54 $7.99 $8.39 $10.11 

New Muffler Differential $7.83 $8.95 $8.73 $6.26 $7.16 $6.98 

TOTAL COST $48.05 $51.80 $60.06 $41.97 $44.76 $51.97 

* 50/50- split of metallic vs ceramic substrates 

6-20 
Costs of Control 

Table 6.2-19: Fixed Costs for Class II OHV V-Twin Engine 

Useful Lives 250, 500, 1000 

R&D COSTS 

Design (2 months) $20,612 

Development (5 months) $143,521 

TOTAL R&D $164,133 

TOOLING COSTS 

Heat Shield Stamping $50,000 

Engine Shroud Modification $25,000 

Setup Changes $25,000 

New Muffler Design $100,000 

Total Tooling per Engine Line $200,000 

TOTAL FIXED COSTS $364,133 

Electronic Fuel Injection 

Electronic fuel injection (EFI) is another solution for engines with two or more cylinders. 

EFI will allow more equal fuel delivery between or among the engine cylinders. In addition, it 

enables better atomization and more efficient fuel delivery during load pickup. If an engine 

family is somewhat close to the Phase 3 standard currently then EFI may allow the engine to 

meet the emission standards without a catalyst. If a small catalyst is needed, EFI allows the 

engine to be setup for cylinder monitoring and can be shut down if all cylinders are not operating 

properly. Due to the anticipated higher cost for EFI compared to catalyst, EPA estimates that 

each engine manufacturer will initially apply EFI to the engine family, of two or more cylinders, 

with the highest sales volume. Table 6.2-20 lists the estimated costs to apply electronic fuel 

injection. The cost tables include subtracting the existing carburetor. 

6-21 
Final Regulatory Impact Analysis 

Table 6.2-20: Variable Costs for Electronic Fuel Injection - Open and Closed Loop 

For Class II Engines and Applications with a Battery21 

Open Loop EFI Closed Loop EFI 

Injectors 8.00 8.00 

Pressure Regulator 3.75 3.75 

ECM/MAP Sensor 27.00 27.00 

Throttle Body 2.75 2.75 

Air Temperature Sensor 1.50 1.50 

Fuel Pump 10.50 10.50 

Oxygen Sensor -- 7.00 

Wiring/Related Hardware 12.00 12.00 

HARDWARE COST TO MANUFACTURE 66.75 73.75 

OEM markup @ 29% 19.36 21.39 

Warranty Markup @ 5% 2.85 3.69 

Total Component Cost 88.96 98.83 

Remove existing carburetor ($15) marked up 29% -19.35 -19.35 

EFI Technology Difference $69.61 $79.48 

Fixed costs for electronic fuel injection are listed in Table 6.2-21. Open loop fuel 

injection requires more research and development time due to the fact that it does not use an 

oxygen sensor to keep the air/fuel ratio in check. This analysis estimatess all engines using 

electronic fuel injection will be developed as closed loop fuel injection systems. 

6-22 
Costs of Control 

Table 6.2-21: Fixed Costs for Electronic Fuel Injection - Open and Closed Loop 

For Class II Engines and Applications with a Battery 

Open Loop Closed Loop 

Design $41,225 $20,612 

Development $229,633 $57,408 

Modified Exhaust Manifold for O2 Sensor --- $25,000 

Total Fixed Costs $270,858 $103,020 

6.2.2.3 Equipment Costs 

The majority of Class I engines are sold as a unit and therefore the engine, fuel tank and 

muffler are provided by the engine manufacturer to the equipment manufacturer. As shown in 

EPA’s Technical Study on the “Safety of Emission Controls for Nonroad Spark-Ignition Engines 

<50 Horsepower”, catalysts can be applied to Class I engines such that muffler temperatures are 

equal to or less than those of the current Phase 2 product with minimal changes to the engine 

package. Some engines may require larger mufflers to house a catalyst depending on current 

muffler design. However the majority of equipment housing Class I engines are close coupled to 

the engine with open access for air cooling and therefore it no equipment redesign costs are 

applied to equipment manufacturers. 

The majority of Class II engines are not sold as a unit. The current industry practice 

includes equipment manufacturers purchasing the muffler separate from the engine. Based on 

conversations with industry it is believed that for several reasons this practice will change to the 

dominant practice being the equipment manufacturer purchasing the muffler from the engine 

manufacturer. The offerings by the engine manufacturer will likely be influenced by the largest 

customers and smaller equipment manufacturers will have a few set models from which to 

choose. A limited amount of equipment redesign will be required on products. 

EPA’s work with catalysts in mufflers of two one-cylinder Class II lawn tractor engines 

has revealed that the current muffler on this equipment type has plenty of room to accommodate 

the catalyst and internal baffling to promote cooling of the exhaust gases. Smaller mufflers are 

used in other applications in which engine noise is not of concern. EPA did not work with these 

mufflers and therefore, it is uncertain if the catalyzed muffler will work in these mufflers. It is 

possible that a larger muffler can may be required to accommodate the catalyst. 

Changes that will be required on Class II engines with catalysts includes a heat shield for 

the muffler (counted in catalyst costs), necessary sheet metal to direct cooling from the engine 

flywheel to the muffler and any equipment design changes to accommodate a different engine 

envelope. 

Incorporating shrouding to direct the cooling air to and around the muffler is of most 

6-23 
Final Regulatory Impact Analysis 

importance. The shrouding added includes extending and rerouting some of the engine sheet 

metal that is used to direct the air-flow out of the engine cylinder and blocking off the usual air 

exit into the engine compartment. The air is routed out the bottom of the chassis instead. In 

EPA’s Class II one cylinder engine testing, the “touch-guard” was boxed in by closing off it's 

slots, closing off one end, and reducing the size of the opening on the opposite end. The exhaust 

exit was re-routed to a different location, and an ejector was added over the top of the exhaust. 

The amount of additional metal is fairly minimal and relatively thin-gage. The best examples are 

the Kohler CV490 on one of the Craftsman tractors and the Kohler SV590 on the Cub Cadet. 

Detailed photos of the SV590 installation can be found in EPA’s Safety Study.22 

For equipment that use engines with catalysts and require heat shield or equipment 

design changes, variable costs are estimated for the sheet metal and/or engine structure redesign 

at $1.30 per piece of equipment. Since a portion of engines are assigned to EFI, or will likely 

not require additional heat shield or equipment modifications due to current equipment design, it 

is estimated that 60 percent of equipment will utilize increased sheet metal and/or engine 

structure redesign. This yields a sales weighted average of $0.78 per equipment. Fixed costs 

for R&D for the added sheet metal design and/or engine restructure are estimated at $30,000 per 

equipment model and tooling changes are also estimated at $45,000 per model. These estimates 

are based on the estimates for developing and applying heat shields in the catalyst cost estimates 

for Class II and can be seen in Table 6.2-22. 

Table 6.2-22: Average Equipment Costs Per Equipment Model 

Variable Costs Fixed Costs 

Heat Shield -0- included in catalyst costs -0- included in catalyst costs 

Additional material for 

equipment redesign or air 

entrainment pathway 

1.30 per equipment 

0.78 avg over all for 60% of 

equipment 

n/a 

R&D n/a 30,000 

Tooling Changes n/a 45,000 

6.2.3 Compliance and Certification 

The certification and compliance costs include engine dynamometer aging as well as 

emission testing pre- and post-aging. Certification and compliance costs are included in this 

analysis as fixed costs. After preliminary emission testing, engines are aged on the 

dynamometer to the regulatory useful life. The aged engines are then emission tested. The 

engine’s emission levels must be below the new standards. If not, then the engine family cannot 

be certified unless the excesses are offset with other engine families within a manufacturers 

product line and the manufacturer must be involved in the averaging, banking and trading 

program. Engine families will need to certify to the new emission standards using the updated 

6-24 
Costs of Control 

test procedure found in Chapter 4. 

The Phase 2 certification database was used as the basis for the number of engine 

families to be certified to these standards. The 2005 Certification database contains a number of 

engine manufacturers that have certified to the Phase 1 emission standards (1997) as well as a 

large number of additional engine manufacturers that have certified to the Phase 2 standards 

(2002). 

6.2.3.1 Measurement Protocol 1065 Compliance Costs 

New to the small engine industry are the 1065 protocols for gaseous emission 

measurement. These protocols are found in 40 CFR Part 1065. Depending on the analyzing 

equipment used by the industry, the certification analyzers may have to be upgraded to the 

estimated cost of $250,000. It is possible that less costly upgrades on some analyzers will be 

available. A CVS system can be assembled for $50,000 given manufacturer ingenuity. 

6.2.3.2 Certification Costs 

Certification costs include emission testing after a short engine break-in period and aging 

on a dynamometer to the full useful life and then repeat emission testing. Costs for 

dynamometer aging of each Class and corresponding useful life are found in ICF’s report “Small 

SI Engine Technologies and Costs.”23 The costs per dynamometer aged engines are estimated in 

Table 6.2-3. are based on test setup, data analysis, engine aging operation, dyno costs, scheduled 

maintenance, prototype engine cost and fuel. 

Table 6.2-23: Dynamometer Aging Certification Costs Per Class and Useful Life 

CLASS I CLASS II 

125 $9,532 250 $18,413 

250 $17,462 500 $34,658 

500 $33,353 1,000 $70,069 

The costs for the emission compliance tests are found in Tables 6.2-24 and 6.2-25 and 

they are the same for each engine regardless of useful life category. A total of two emission 

tests after break-in and two at end of useful life are accounted for in this cost analysis. The 

emission test costs are estimated at $2,012 each and are based on the costs for a private test 

laboratory in 2005.24 

Table 6.2-24: Emission Testing Costs Per Class 

CLASS I CLASS II 

all useful lives $8,048 all useful lives $8,048 

6-25 
Final Regulatory Impact Analysis 

Table 6.2-25: Per Engine Family Emission Testing and Dynamometer 

Aging Costs Per Class and Useful Life 

CLASS I CLASS II 

125 $17,580 250 $26,461 

250 $25,510 500 $42,706 

500 $41,401 1,000 $78,117 

6.2.4 LPG/CNG Engine Costs 

Engine manufacturers and equipment manufacturers certify engines to run on LPG. The 

number of engine families are obtained from EPA’s 2008 Certification Database. Certification 

costs found in Section 6.2.3.2 apply to these engines. Part 1065 compliance costs are not applied 

since the engine manufacturers are the same as listed in the gasoline section (costs already 

applied) and it is estimated that equipment manufacturers contract with a test lab due to the high 

cost of maintaining an individual test lab. 

For engine certification, all engine families will be required to be tested for baseline 

emissions, see Table 6.2-26. Small volume engine manufacturers with a production of 10,000 

engines or less can utilize an assigned deterioration factor and do not have to undergo 

dynamometer aging or end of life emission testing. Those listed under dynamometer aging in 

Table 6.2-26 will need to age the engines and perform end of life emission testing. The number 

of engine families listed under catalyst development will need emission reduction technology 

such as catalysts. 

Table 6.2-26: Number of LPG Engine Families Per Class and 

Useful Life Designation for Fixed Cost Analysis 

CLASS I CLASS II 

UL BaselineE 

mission 

Testing 

Dynamo-meter 

Aging + End of 

Life Emission 

Testing 

Catalyst 

Dev 

UL Baseline 

Emission 

Testing 

Dynamo-meter 

Aging + End of 

Life Emission 

Testing 

Catalyst 

Dev 

1cyl/2cyl 

125 -- -- -- 250 9 9 1 2 

250 -- -- -- 500 20 20 2 10 

500 2 2 1 1000 13 13 1 8

 For Phase 3, companies with small volume production (<10,000) can use an assigned df. 

6-26 
Costs of Control 

Table 6.2-27 lists the certification costs. 

Table 6.2-27: Certification Costs - LPG 

Class I Class II

 Baseline Emission Testing $8,048 $169,008

 Dynamometer Aging $66,706 $1,769,774

 End of Life Emission Test $8,048 $169,008

 Total $82,802 $2,107,790 

As mentioned above, the technology to reduce emissions to the Phase 3 levels is 

catalysts. Catalysts are currently being utilized on LPG engines as shown in EPA’s 2008 

Certification Database. Basic engine improvement design changes, accounted for in the gasoline 

engine families, were not accounted for in these engines for they were already made in the base 

engine before they were converted to run on LPG/CNG. Costs that will be applied to these 

engines are R&D for catalyst formulation and variable parts costs which will need to be 

formulated for the exhaust makeup from these engines. The majority of these engines are two 

cylinder engines, however the concerns of the application of catalysts to these engine designs are 

relieved in that some of the V-twin LPG engines are already certified with catalysts. Costs for 

catalyst system redesign for some of the existing engine families are included in order for these 

families to meet the Phase 3 standards. Table 6.2-28 lists the R&D and Tooling costs for 

catalysts for LPG. Table 6.2-29 contains the totals for fixed cost for each class given the total 

number of engine families listed in Table 6.2-26. 

6-27 
Final Regulatory Impact Analysis 

Table 6.2-28: Fixed Costs for Class II OHV Single Cylinder Engine - LPG 

Engine Class II 

Useful life (hrs) 125, 250, 500 

Valving OHV 

R&D 

Design $20,612 

Development (5 months) $143,521 

TOTAL R&D per Engine Line $164,133 

TOOLING COSTS 

TOTAL TOOLING per Engine Line 0* 

TOTAL FIXED COSTS $164,133 

*LPG engines are modified from gasoline version engines. Tooling costs are not included for it 

is estimated that catalyst volume for these engines will be determined based on a percentage of 

engine displacement, as the gasoline version, and therefore the catalysts will fit into the same 

muffler space. 

Table 6.2-29: Total Fixed Costs for LPG 

Engine Families 2005$ 

Class I Class II 

Catalyst R&D $492,399 $6,072,921 

Certification Cost $47,114 $1,146,438 

TOTAL $539,413 $7,219,359 

Certification data on gaseous fueled engines show that the HC:NOx ratio is higher in 

NOx than in HC which is opposite from gasoline engines. Platinum will be used in the precious 

metal mixture in order for the oxygen reduced from the NOx to be utilized to convert CO due to 

the lack of HC. For Class I engines, the cost estimate presented in Table 6.2-7 is applicable 

because it is calculated with a platinum/palladium/rhodium ratio of 5/0/1. For Class II engines, 

the 500 and 1000 hour catalyst cost estimates will be modified in order to include more platinum 

and all useful life periods will have resized catalysts based on the sales weighted engine 

displacement in the certification listing of LPG engines. Table 6.2-30 lists the variable catalyst 

costs for Class II OHV Engines, 250 and 500 hour useful life engines (no 1000 hour UL engines 

are listed in the LPG certification). Two to three cylinder engines have higher displacement and 

therefore costs are recalculated for those engine designs. 

6-28 
Costs of Control 

Table 6.2-30: Variable Catalyst Costs for Class II OHV Engines - LPG 

HC+NOx Emission Reduction to Phase 3 Standards 

1 cylinder 2 cylinders 

Useful Life 250 500 1000** 250 500 1000 

Engine Power (hp) 13.8 17.8 - 18.2 19.2 23 

Engine Displacement (cc) 415 389 - 597 743 751 

Engine/Catalyst 33% 40% - 33% 40% 50% 

Catalyst Volume (cc)*** (per 

cylinder) 

137 156 - 197 297 376 

Substrate Diameter 5.25 6.00 - 5.00 5.00 5.50 

Substrate* (per cylinder) 5.55 8.91 - 3.70 5.20 6.34 

Washcoat and Precious Metal 4.24 4.82 - 2.96 4.46 8.86 

Labor $1.40 $1.40 - $1.40 $1.40 $1.40 

Labor Overhead 40% $0.56 $0.56 - $0.56 $0.56 $0.56 

Supplier Markup 29% $3.41 $4.55 - $2.50 $3.37 $4.97 

Manufacture Price (per catalyst) $15.16 $20.24 - $11.12 $14.99 $22.14 

Total Catalyst Cost $15.16 $20.24 $22.24 $30.00 $44.24 

Heat Shield (2 for v-twin) $4.23 $4.26 - $5.90 $6.92 $7.32 

Spark Arrestor (2 for v-twin) $0.10 $0.05 - $0.20 $0.10 $0.10 

Hardware Cost to Manufacturer $19.49 $24.55 - $28.34 $37.00 $51.69 

w/Markup 29% OEM $25.14 $31.67 - $8.22 $10.73 $14.99 

Add’l Muffler for V-twin - - - $7.83 $8.95 $8.73 

Total Catalyst Cost for LPG 

engines 

$24.14 $31.67 - $44.40 $56.68 $75.41 

Total Catalyst Cost for Gasoline 

Engines 

$23.50 $20.97 - $48.05 $51.80 $60.06 

Cost Difference $1.64 $10.70 - -$3.66 $4.87 $15.37 

* 50/50- split of metallic vs ceramic substrates

 ** No one cylinder LPG engines are certified to the 1000 hour useful life 

*** these catalyst volumes were calculated from the engine disp in EPA’s certification data for 2005 

6-29 
Final Regulatory Impact Analysis 

Calculations for the rulemaking have been completed using gasoline assumptions. To 

account for the increase in costs due to some of the gasoline engines being used as LPG engines, 

an increase in the total cost is added to the current gasoline engine variable cost total. 

Table 6.2.-31 is an example of costs for 2012 in 2005$. 

Table 6.2-31: Change in Variable Cost in 2012, 2005$ - LPG 

Total Engine 

Sales 

Estimate per 

Useful Life 

2012 

% of 

LPG/CNG 

Engines in 

Useful Life 

per Class 

# of Cyl Number 

of 

Engines 

with 

change in 

Cost 

Estimate 

Variable 

Cost 

Change in 

2012 

Total Change in 

costs in 2012 

2005$ 

Class I 

125 OHV 2,953,419 0% 1 0 0 0 

250 905,005 0% 1 0 0 0 

500 623,431 0.63% 1 3574 0 0 

Class II 

250 3,334,488 0.58% 1 14,500 $1.38 $20,027 

2 10,469 -$2.95 -$30,923 

500 724,231 1.94% 1 12,918 $9.25 $119,523 

2 90,630 $5.17 $ 468,553 

1000 821,463 3.19% 2 18,700 $15.59 $ 291,517 

2012 Total Increase $868,698 

* use the same technology as gasoline counterpart 

Table 6.2-32 contains the catalyst cost estimates for LPG engines including a learning 

curve discount. This cost estimate is used in year six of the cost estimates. 

6-30 
Costs of Control 

Table 6.2-32: Variable Catalyst Costs with Learning Curve for Class II OHV Engines -

LPG; HC+NOx Emission Reduction to Phase 3 Standards 

1 cylinder 2 cylinders 

Useful Life 250 500 1000** 250 500 1000 

Engine Power (hp) 13.8 17.8 - 18.2 19.2 23 

Engine Displacement (cc) 415 389 - 597 743 751 

Engine/Catalyst 33% 40% - 33% 40% 50% 

Catalyst Volume (cc)*** (per 

cylinder) 

137 156 - 197 297 376 

Substrate Diameter 5.25 6.00 - 5.00 5.00 5.50 

Substrate* (per cylinder) 4.44 7.13 - 2.96 4.16 5.07 

Washcoat and Precious Metal 4.24 4.82 - 2.96 4.46 8.86 

Labor $1.40 $1.40 - $1.40 $1.40 $1.40 

Labor Overhead 40% $0.56 $0.56 - $0.56 $0.56 $0.56 

Supplier Markup 29% $3.09 $4.03 - $2.29 $3.07 $4.61 

Manufacture Price (per catalyst) $13.73 $17.94 - $10.17 $13.65 $20.50 

Total Catalyst Cost $15.90 $24.88 $20.33 $27.30 $41.00 

Heat Shield (2 for v-twin) $3.38 $3.41 - $4.72 $5.54 $5.86 

Spark Arrestor (2 for v-twin) $0.10 $0.05 - $0.20 $0.10 $0.10 

Hardware Cost to Manufacturer $17.21 $21.40 - $25.25 $32.93 $46.96 

w/Markup 29% OEM $22.20 $27.61 - $7.32 $9.55 $13.62 

Add’l Muffler for V-twin - - - $6.26 $7.16 $6.98 

Total Catalyst Cost for LPG 

engines 

$22.20 $27.61 - $38.84 $49.64 $67.56 

Total Catalyst Cost for Gasoline 

Engines 

$20.82 $18.35 - $41.79 $44.47 $51.97 

Cost Difference $1.38 $9.25 - -$2.95 $5.17 $15.59 

* 50/50- split of metallic vs ceramic substrates

 ** No one cylinder LPG engines are certified to the 1000 hour useful life 

*** these catalyst volumes were calculated from the engine disp in EPA’s certification data for 2005 

6-31 
Final Regulatory Impact Analysis 

6.2.5 Small SI Aggregate Costs 

Costs presented in the previous sections are combined here to present streams of costs. 

The first, Section 6.2.5.1, presents variable costs (recurring costs) for meeting the Phase 3 

exhaust standards. Section 6.2.5.2 presents a stream of fixed costs for meeting the Phase 3 

exhaust standards. Costs are based on assuming all engines are gasoline engines. Additional 

costs for LPG engines are included at the end of this section. 

6.2.5.1 Variable Costs for Meeting Exhaust Standards 

Variable costs for Class I are summarized in Table 6.2-10 for engine improvements and 

catalysts in near term and long term (with learning) costs. Nearly all engines in Class I (96.9% 

125 useful life (UL), 99.4% 250 UL and 72.65% 500 UL) are estimated to have both 

technologies applied and therefore the costs are added according to useful life period and then 

multiplied by the number of engines sold per useful life category, as will be discussed later. The 

resultant variable costs per engine is presented in Table 6.2-33. Long term costs are six years 

after the near term costs and include a 20 percent learning curve reduction for engine 

improvement components, catalyst substrate and heat shield costs. 

Variable costs for Class II are a combination of engine improvements and catalyst or 

engine improvements and electronic fuel injection (EFI), see Section 6.2.2. Information on 

engine designs and related certification emission results in the 2008 EPA Certification Database 

were utilized to determine the percentage of technologies per useful life. A portion of the 

engines, the largest multi-cylinder engine family per engine manufacturer needing emission 

reduction, are assigned the use of electronic fuel injection. The remaining engine families are 

assigned catalysts and related engine improvements. Some engines would not to require any 

costs. Long term costs (learning) are six years after the near term costs and include a 20 percent 

learning curve reduction for engine improvement components, catalyst substrate and heat shield 

costs. 

Table 6.2-32: Percentage Technologies Per Useful Life per Class II 

Useful Life No changes EFI - Class II 

V-twin 

V-twin 

catalyst 

Catalyst-Single 

Cylinder 

250 43.66% 5.88% 0.61% 49.85% 

500 59.84% 5.62% 0.30% 34.24% 

1000 28.50% 10.80% 18.24% 42.46% 

6-32 
Costs of Control 

Table 6.2-33: Variable Costs Per Engine for Meeting 

Exhaust Standards, Per Engine (2005$) 

Useful Life (hrs) 

Class I Class II 

Near Term (2012) Long Term 

(2017)* 

Near Term (2011) Long Term 

(2016)* 

125- SV 10.41 9.43 -- --

125 - OHV 8.55 7.80 -- --

250 12.17 11.33 16.8 14.24 

500 11.71 10.87 11.93 9.87 

1000 -- -- 30.07 25.21 

*Long term includes learning reduction 

The total Small SI engine costs for the first 30 years (2008-2037) were estimated using 

sales and growth estimates from the US EPA’s NONROAD model. The percentage sales per 

useful life category (Class I: 125, 250, 500, Class II: 250, 500, 1000) were calculated from the 

manufacturer prescribed useful life period and yearly estimated sales per engine family in the 

EPA 2008 Phase 2 certification database (confidential information). The percentages in 

Table 6.2-34 were applied to US EPA’s NONROAD model sales estimates and the results are 

presented in Table 6.2-35 Note that snowblowers are not included for they only have to comply 

with the evaporative standards since they are exempted from the exhaust emission standards. 

Table 6.2-34: Small SI Engines 

Sale Percentages per Useful Life 

Useful Life Class I Class II 

125- SV 66% ---

125 - OHV 23% ---

250 6% 74% 

500 5% 11% 

1000 --- 15% 

6-33 
Final Regulatory Impact Analysis 

Table 6.2-35: Class I and Class II Projected Sales 

per Useful Life Category (snowblowers excluded) 

YEAR 

CLASS I CLASS II 

125 125 250 500 250 500 1,000 

SV OHV OHV OHV OHV OHV OHV 

2008 

2009 

2010 

2011 

2012 

2013 

2014 

2015 

2016 

2017 

2018 

2019 

2020 

2021 

2022 

2023 

2024 

2025 

2026 

2027 

2028 

2029 

2030 

2031 

2032 

2033 

2034 

2035 

2036 

2037 

6,139,695 

6,250,204 

6,360,351 

6,474,907 

6,584,353 

6,698,636 

6,810,588 

6,921,857 

7,031,516 

7,144,731 

7,256,744 

7,370,110 

7,482,752 

7,594,978 

7,706,370 

7,818,799 

7,931,065 

8,043,780 

8,157,416 

8,270,846 

8,383,989 

8,497,471 

8,610,967 

8,724,583 

8,838,143 

8,951,587 

9,064,949 

9,178,412 

9,291,898 

9,405,435 

2,112,583 

2,150,608 

2,188,508 

2,227,925 

2,265,584 

2,304,907 

2,343,428 

2,381,714 

2,419,446 

2,458,402 

2,496,944 

2,535,952 

2,574,710 

2,613,326 

2,651,654 

2,690,339 

2,728,969 

2,767,752 

2,806,853 

2,845,883 

2,884,814 

2,923,861 

2,962,913 

3,002,007 

3,041,082 

3,080,116 

3,119,122 

3,158,163 

3,197,212 

3,236,279 

565,168 

575,340 

585,479 

596,025 

606,099 

616,619 

626,924 

637,167 

647,261 

657,683 

667,994 

678,429 

688,798 

699,129 

709,382 

719,732 

730,066 

740,442 

750,902 

761,343 

771,758 

782,204 

792,652 

803,110 

813,564 

824,006 

834,442 

844,886 

855,333 

865,784 

489,249 

498,055 

506,832 

515,961 

524,682 

533,789 

542,710 

551,577 

560,315 

569,337 

578,263 

587,296 

596,272 

605,215 

614,091 

623,051 

631,997 

640,978 

650,034 

659,072 

668,088 

677,131 

686,175 

695,229 

704,278 

713,318 

722,352 

731,393 

740,436 

749,484 

3,375,298 

3,436,078 

3,497,169 

3,560,736 

3,621,924 

3,685,741 

3,747,698 

3,809,238 

3,870,775 

3,933,230 

3,995,499 

4,058,405 

4,120,822 

4,183,226 

4,245,149 

4,307,507 

4,369,904 

4,432,728 

4,495,615 

4,558,320 

4,620,946 

4,683,749 

4,746,567 

4,809,474 

4,872,290 

4,935,044 

4,997,777 

5,060,568 

5,123,362 

5,186,178 

485,273 

494,012 

502,795 

511,934 

520,731 

529,906 

538,814 

547,662 

556,509 

565,488 

574,441 

583,485 

592,459 

601,431 

610,333 

619,299 

628,270 

637,302 

646,344 

655,359 

664,363 

673,392 

682,423 

691,468 

700,499 

709,521 

718,540 

727,568 

736,596 

745,627 

687,306 

699,683 

712,123 

725,067 

737,527 

750,522 

763,138 

775,669 

788,200 

800,917 

813,597 

826,406 

839,116 

851,824 

864,433 

877,131 

889,837 

902,629 

915,435 

928,203 

940,956 

953,744 

966,536 

979,345 

992,137 

1,004,915 

1,017,689 

1,030,475 

1,043,262 

1,056,053 

The Total Variable Costs were calculated using the sales information found in 

Table 6.2-35 and applying the corresponding variable cost from Table 6.2-33. Results are 

presented in Table 6.2-36. Engines used in snowblowers and handheld equipment will require 

only evaporative control measures and these are presented in Section 6.5. 

6-34 
Costs of Control 

Table 6.2-36: Variable Costs for Meeting Phase 3 Exhaust Emission Standards, 2005$ 

Year Class I: Engine only Class II: Engine & Equipment 

125 250 500 250 500 1,000 

2008 

2009 

2010 

2011 

2012 

2013 

2014 

2015 

2016 

2017 

2018 

2019 

2020 

2021 

2022 

2023 

2024 

2025 

2026 

2027 

2028 

2029 

2030 

2031 

2032 

2033 

2034 

2035 

2036 

2037 

-

-

-

-

86,472,768 

87,973,661 

89,443,931 

90,905,230 

92,345,393 

86,511,329 

87,867,634 

89,240,307 

90,604,228 

91,963,103 

93,311,878 

94,673,217 

96,032,587 

97,397,383 

98,773,331 

100,146,794 

101,516,776 

102,890,863 

104,265,113 

105,640,825 

107,015,858 

108,389,476 

109,762,116 

111,135,969 

112,510,105 

113,884,858 

-

-

-

-

7,376,417 

7,504,448 

7,629,867 

7,754,521 

7,877,372 

7,449,638 

7,566,432 

7,684,635 

7,802,085 

7,919,100 

8,035,245 

8,152,473 

8,269,530 

8,387,055 

8,505,540 

8,623,812 

8,741,783 

8,860,108 

8,978,447 

9,096,912 

9,215,318 

9,333,603 

9,451,803 

9,570,108 

9,688,438 

9,806,820 

-

-

-

-

6,141,854 

6,248,457 

6,352,885 

6,456,676 

6,558,965 

6,191,089 

6,288,151 

6,386,385 

6,483,993 

6,581,239 

6,677,763 

6,775,185 

6,872,467 

6,970,137 

7,068,606 

7,166,896 

7,264,937 

7,363,272 

7,461,619 

7,560,070 

7,658,473 

7,756,775 

7,855,006 

7,953,324 

8,051,663 

8,150,046 

-

-

-

59,835,023 

60,863,232 

61,935,618 

62,976,746 

64,010,872 

55,130,893 

56,020,430 

56,907,330 

57,803,283 

58,692,279 

59,581,099 

60,463,047 

61,351,207 

62,239,924 

63,134,711 

64,030,407 

64,923,505 

65,815,481 

66,709,969 

67,604,683 

68,500,650 

69,395,337 

70,289,133 

71,182,631 

72,076,956 

72,971,320 

73,865,999 

-

-

-

6,105,598 

6,210,517 

6,319,944 

6,426,181 

6,531,704 

5,493,685 

5,582,326 

5,670,704 

5,759,984 

5,848,571 

5,937,140 

6,025,024 

6,113,527 

6,202,086 

6,291,250 

6,380,504 

6,469,500 

6,558,384 

6,647,518 

6,736,674 

6,825,955 

6,915,109 

7,004,174 

7,093,210 

7,182,327 

7,271,449 

7,360,602 

-

-

-

21,799,867 

22,174,477 

22,565,182 

22,944,499 

23,321,265 

19,873,736 

20,194,399 

20,514,111 

20,837,087 

21,157,554 

21,477,959 

21,795,886 

22,116,052 

22,436,419 

22,758,975 

23,081,857 

23,403,804 

23,725,346 

24,047,793 

24,370,323 

24,693,303 

25,015,822 

25,338,020 

25,660,111 

25,982,500 

26,304,902 

26,627,419 

6.2.5.2 Fixed Costs 

Fixed costs for the small spark ignition engines include test cell modifications for 1065 

compliance, emission certification of engine families as well as R&D and tooling expenditures 

for engine design changes and equipment modifications. This section presents the aggregate 

fixed costs for small spark ignition engines. 

The test procedure for small spark ignited engines for this rulemaking is governed by Part 

1065 with regulation specific details in Part 1054. Evaluation of Part 1065 reveals that there are 

some differences in calibration procedures with existing Part 90 and programming must be 

changed to calculate via 1065. As industry begins to apply 1065 requirements in its test cells 

6-35 
Final Regulatory Impact Analysis 

there may be some other modifications that will be revealed. To cover these costs, EPA is 

allocating $600,000 per engine manufacturer for 1065 compliance. The number of engine 

manufacturers is taken from the the certification database which lists 16 different engine 

manufacturers of nonhandheld engines and 15 engine manufacturers of handheld engines. The 

certification database also lists a number of new offshore manufacturers. These companies 

typically certify through independent test laboratories within the United States and therefore 

only encounter costs for these upgrades through increased service fees. For this cost analysis, 

one additional manufacturer for nonhandheld and handheld is added to the certification database 

totals to cover test labs. Therefore, for nonhandheld engine manufacturers, a total of 17 test 

facilities at 600,000 per test facility yields a total estimated cost of $10,200,000. For the purpose 

of this cost analysis, this cost is spread evenly across all useful lives per class for a total of 

1,700,000 for each. Upgrades for test cells for handheld engines are calculated at $9,600,000. 

Engine manufacturers are to begin using compliant test cells for new engine family certifications 

beginning in 2013. This cost analysis estimates engine manufacturers will invest in their test 

cells from 2008-2011. 

Table 6.2-37: Fixed Costs for Compliance 

with 1065, 2005$ (thousands) 

CLASS I CLASS II HANDHELD 

125 250 500 250 500 1000 

TOTAL 1,700 1,700 1,700 1,700 1,700 1,700 9,600 

Investment Per Year 

2008 425 425 425 425 425 425 2,400 

2009 425 425 425 425 425 425 2,400 

2010 425 425 425 425 425 425 2,400 

2011 425 425 425 425 425 425 2,400 

Each engine family must certify each year to the emissions standards applicable in that 

year. This cost analysis assumes no carryover data, but that all engine families will undergo 

durability aging and emission testing. The number of engine families per Class and per useful 

life category were taken from EPA’s 2008 Certification Database. For Class I, the 2008 database 

lists 66 engine families from traditionally regulated companies. For Class II, the 2008 database 

lists 121 engine families. The engine families are designated per useful life class by the claim in 

the certification application. The estimates in Table 6.2-38 represent the number of engine 

families per useful life designation used in this cost analysis to calculate fixed costs. Costs for 

certifiers of LPG engines are covered in Section 6.2.4. 

6-36 
Costs of Control 

Table 6.2-38: Number of Engine Families Per Class 

and Useful Life Designation for Certification 

CLASS I CLASS II 

125 31 250 39 

250 15 500 18 

500 20 1000 64 

It should be noted that the certification database does contain certifications from a large 

number of companies that have a short history of compliance and claim large sales numbers. 

These companies were not used in this analysis for we are not yet convinced they are actually 

selling in this country nor in the numbers they claim. Engine families still certified to Phase 1 

(either through credits, small engine family flexibilities or averaging) were also not included. 

For Class II, there are a number of small volume engine families which have not yet been 

certified to Phase 2 due to flexibilities in that rulemaking. Due to the low volume sales, these 

engine families were estimated to be certified to the 250 hour useful life. For Class I-A, engine 

families are being moved to the <80cc category where they already meet the handheld emission 

standard. Class I-B engines are traditionally low volume sales engine families; we believe that 

they will likely be incorporated into the engine manufacturers ABT programs and certification of 

these low volume sales engine families will be covered without engine improvement. 

The total engine exhaust emission certification costs are calculated by taking the number 

of engine families from Table 6.2-38 and multiplying them by the emission test and 

dynamometer aging costs from Table 6.2-23. This analysis estimates that engine certification 

costs are expended over two years prior to standard implementation as shown in Table 6.2-39. 

The combined 1065 compliance and engine certification costs are presented in Table 6.2-40. 

Table 6.2-39: Engine Certification Costs to Exhaust Standards 

CLASS I CLASS II Handheld 

125 250 500 250 500 1000 $0 

2008 

2009 635,064 811,414 3,007,505 

2010 272,490 191325 455,411 635,064 811,414 3,007,505 

2011 272,490 191325 455,411 

Table 6.2-40: Total Stream of Costs for 

Engine Certification by Year, (thousands) 

CLASS I CLASS II 

125 250 500 250 500 1000 Handheld 

2008 425 425 425 425 425 425 2,400 

2009 425 425 425 1,060 1,236 3,432 2,400 

2010 697 616 880 1,060 1,236 3,432 2,400 

2011 697 616 880 425 425 425 2,400

6-37 
Final Regulatory Impact Analysis 

Fixed costs for engine research and development and tooling changes to meet exhaust 

emission standards are presented throughout sections 6.2.1 Class I and 6.2.2. Class II. The fixed 

costs include engine improvements, engine improvements with catalyst development or EFI 

development and application. Class I engine families are assigned engine improvements and/or 

engine improvements and catalyst development costs. The number of engine families per Class 

are from the 2008 EPA Certification Database. Table 6.2-41 presents the number of engine 

families estimated per technology package for Class I and Table 6.2-42 presents the number of 

engine families estimated per technology for Class II. 

Table 6.2-41: Estimated Number of Engine Families per Technology Package, Class I 

Technology/Useful Life 125 250 500 

- Engine Improvements (all) 31 15 20 

- Catalysts 26 13 14 

Table 6.2-42: Estimated Number of Engine Families per Technology Package, Class II 

Technology/Useful Life 250 500 1000 

- Engine Improvements (all) 39 18 64 

- One Cylinder Engine Catalyst 16 4 14 

- Two or More Cylinders per Engine for Catalyst 7 3 27 

- Electronic Fuel Injection on Two or More Cylinder Engines 4 3 5 

Table 6.2-43: Total Fixed Costs (thousands) 

for Engines to Meet Phase 3 Exhaust Emission Standards 

CLASS I CLASS II 

125 125 250 500 250 500 1000 

SV OHV OHV OHV OHV OHV OHV 

R&D 5,286 5,598 5,335 6,567 12,412 5,225 20,780 

Tooling 10,164 5,571 5,205 6,540 12,412 12,412 12,412 

TOTAL 15,450 11,169 10,540 13,107 15,450 15,450 15,450 

Table 6.2-44: Total Fixed Costs Investment (thousands) 

for Engines to Meet Phase 3 Exhaust Emission Standards 

CLASS I CLASS II 

125-sv 125-ohv 250 500 250 500 1000 

2008 1,322 1,400 1,334 1,642 4,301 2,398 7,419 

2009 1,322 1,400 1,334 1,642 11,150 5,263 18,498 

2010 6,404 4,185 3,936 4,912 11,150 5,263 18,498 

2011 6,404 4,185 3,936 4,912 

6-38 
Costs of Control 

Total fixed costs for Small SI exhaust emissions are shown in Table 6.2-45. 

Table 6.2-45: Certification and Technology Fixed Costs

 for Engines to Meet Phase 3 Exhaust Standards 

Class I Class II Handheld 

125 250 500 250 500 1,000 

2008 3,146 1,759 2,067 4,562 2,167 7,352 2,400 

2009 3,146 1,759 2,067 12,046 5,843 21,438 2,400 

2010 11,286 4,553 5,792 12,046 5,843 21,438 2,400 

2011 11,286 4,553 5,792 425 425 425 2,400 

Equipment companies using Class II engines are also estimated to incur fixed costs in 

redesigning equipment models to incorporate Phase 3 Class II engines. The PSR database shows 

there are 413 businesses using Class II engines.25 Assuming each business on average produces 

two unique models requiring clearly different redesign yields a number of 826 redesigns. 

Table 6.2-22 contains equipment costs per equipment model and Table 6.2-46 contains the total 

equipment costs. 

Table 6.2-46: Total Class II Equipment Cost 

250 500 1000 

2009 10325000 10325000 10325000 

2010 10325000 10325000 10325000 

6.2.5.3 Operating Cost Savings 

The application of electronic fuel injection to an estimated 6.6% of the Class II engines is 

expected to result in fuel savings. Fuel savings from the use of fuel injection on Class II engines 

is estimated at 10 percent. Kohler has been offering a fuel injected Class II engine for nearly 10 

years and two articles (1996 OEM Off-Highway and 1998 Diesel Progress)26,27 claim 15-20 

percent fuel savings over carbureted engines. We elected to conservatively use a figure of ten 

percent. In calculating the fuel savings, we use a gasoline price of $1.81 per gallon without 

taxes.28 Table 6.2-47 presents estimated fuel savings for Class II engines with electronic fuel 

injection. The improvements and catalyst application to Class I engines are estimated to result in 

no operating or fuel savings. Fuel savings that are obtained from evaporative reduction 

technologies are presented later in the evaporative portion of this chapter. 

6-39 
Final Regulatory Impact Analysis 

Table 6.2-46: Fuel Savings from the Increased 

Use of Electronic Fuel Injection on Class II Engines 

Year Gallons Fuel Savings $ 

2008 0 0 

2009 0 0 

2010 0 0 

2011 3,916,719 $7,104,929 

2012 7,074,990 $12,834,033 

2013 10,071,145 $18,269,057 

2014 11,966,500 $21,707,230 

2015 13,835,431 $25,097,472 

2016 15,252,178 $27,667,451 

2017 16,221,164 $29,425,191 

2018 16,966,562 $30,777,343 

2019 17,576,831 $31,884,371 

2020 18,104,416 $32,841,410 

2021 18,532,855 $33,618,599 

2022 18,916,185 $34,313,960 

2023 19,267,974 $34,952,106 

2024 19,607,579 $35,568,148 

2025 19,935,933 $36,163,782 

2026 20,259,628 $36,750,965 

2027 20,579,305 $37,330,860 

2028 20,896,206 $37,905,717 

2029 21,210,286 $38,475,459 

2030 21,521,549 $39,040,090 

2031 21,830,758 $39,600,995 

2032 22,138,949 $40,160,054 

2033 22,446,266 $40,717,527 

2034 22,752,947 $41,273,846 

2035 23,059,059 $41,829,132 

2036 23,363,883 $42,382,085 

2037 23,667,468 $42,932,787 

6-40 
Costs of Control 

6.2.5.4 Total Aggregate Costs 

The aggregate costs for meeting the exhaust emission standards are presented in 

Table 6.2-47. Aggregate costs include variable costs and fixed costs for engine manufacturers 

(technology, certification, 1065 compliance), equipment manufacturers and LPG engine families 

and converters. An average cost per engine is presented in Table 6.2-48 and the aggregate costs 

with fuel savings is presented in Table 6.2-49. 

Table 6.2-47: Total Aggregate for 30 year Cost Analysis 

for Exhaust Emission Standard Compliance without Fuel Savings, 2005$ 

Year Exhaust Only 1065 

Certification 

Upgrades 

Handheld 

CLASS I CLASS II 

2008 7,012,721 15,393,779 2,400,000 

2009 7,012,721 71,614,262 2,400,000 

2010 21,671,947 71,614,262 2,400,000 

2011 21,671,947 93,177,678 2,400,000 

2012 99,991,039 93,481,939 0 

2013 101,726,567 95,129,055 0 

2014 103,426,684 96,728,158 0 

2015 105,116,426 98,316,508 0 

2016 106,781,731 85,010,277 0 

2017 100,152,057 86,381,917 0 

2018 101,722,217 87,749,492 0 

2019 103,311,327 89,131,026 0 

2020 104,890,306 90,501,833 0 

2021 106,463,442 91,872,369 0 

2022 108,024,886 93,232,307 0 

2023 109,600,875 94,601,825 0 

2024 111,174,585 95,972,201 0 

2025 112,754,576 97,351,938 0 

2026 114,347,477 98,733,075 0 

2027 115,937,502 100,110,208 0 

2028 117,523,496 101,485,609 0 

2029 119,114,243 102,864,885 0 

2030 120,705,179 104,244,509 0 

2031 122,297,808 105,626,063 0 

2032 123,889,649 107,005,647 0 

2033 125,479,854 108,383,854 0 

2034 127,068,925 109,761,603 0 

2035 128,659,401 111,140,627 0 

2036 130,250,205 112,519,710 0 

2037 131,841,723 113,899,279 0 

Table 6.2-48 presents a sales weighted average per-equipment cost estimate for engines 

6-41 
Final Regulatory Impact Analysis 

meeting the Phase 3 exhaust standards. Note that the fixed costs are invested prior to the 

implementation date for Class I and Class II engines and therefore the variable costs are what 

remain in these years. Near term costs for Class I are from 2012-2016 and for Class II are from 

2011-2015. Long term costs include a learning curve deduction in manufacturing/production for 

these engines in the 6th year and the Class I costs start in 2017 and Class II starts in 2016. 

Table 6.2-48: Sales Weighted Average Per-Equipment 

Cost Estimates (Without Fuel Savings) for Exhaust Standards, 2005$

 Short Term Costs 

(years 1-5) per Class per 

Useful Life 

Class I Class II Handheld 

(no Exhaust) 125 250 500 250 500 1000 

Near Term 10.48 7.51 11.12 17.70 13.66 31.93 0.00 

Long Term* 9.01 11.33 10.87 15.02 10.76 26.49 0.00 

* Long term is with learning, if applicable 

The aggregate costs with fuel savings is presented in Table 6.2-49. Fuel savings are 

available from Class II engines using electronic fuel injection and start in 2011 which is the first 

year of standard implementation. 

6-42 
Costs of Control 

Table 6.2-49: Total Aggregate for 30 year Cost Analysis 

for Exhaust Emission Standard Compliance with Fuel Savings, 2005$ 

Class I Class II Handheld 

2008 7,012,721 15,393,779 2,400,000 

2009 7,012,721 71,614,262 2,400,000 

2010 21,671,947 71,614,262 2,400,000 

2011 21,671,947 89,260,959 2,400,000 

2012 99,991,039 86,406,949 0 

2013 101,726,567 85,057,910 0 

2014 103,426,684 84,761,659 0 

2015 105,116,426 84,481,077 0 

2016 106,781,731 69,758,099 0 

2017 100,152,057 70,160,753 0 

2018 101,722,217 70,782,931 0 

2019 103,311,327 71,554,195 0 

2020 104,890,306 72,397,418 0 

2021 106,463,442 73,339,514 0 

2022 108,024,886 74,316,122 0 

2023 109,600,875 75,333,851 0 

2024 111,174,585 76,364,623 0 

2025 112,754,576 77,416,005 0 

2026 114,347,477 78,473,447 0 

2027 115,937,502 79,530,903 0 

2028 117,523,496 80,589,404 0 

2029 119,114,243 81,654,598 0 

2030 120,705,179 82,722,959 0 

2031 122,297,808 83,795,305 0 

2032 123,889,649 84,866,697 0 

2033 125,479,854 85,937,588 0 

2034 127,068,925 87,008,656 0 

2035 128,659,401 88,081,568 0 

2036 130,250,205 89,155,827 0 

2037 131,841,723 90,231,811 0 

At a 7 percent discount rate, over 30 years, the estimated annualized cost to 

manufacturers for Small SI exhaust emission control, without fuel savings, is $182 million. The 

corresponding estimated annualized fuel savings due to the use of electronic fuel injection on 

Class II engines is $24 million. At a 3 percent discount rate, the estimated annualized cost to 

manufacturers for Small SI exhaust emission control, without fuel savings, is $189 million. The 

corresponding estimated annualized fuel savings due to the use of electronic fuel injection on 

Class II engines is $27 million. 

6-43 
Final Regulatory Impact Analysis 

6.3 Exhaust Emission Control Costs for Outboard and Personal Watercraft 

Marine Engines 

This section presents our cost estimates for meeting the new exhaust emission standards 

for outboard and personal watercraft marine engines. 

As of about a decade ago, outboard and personal watercraft (OB/PWC) engines were 

primarily two-stroke carbureted engines. There were no emission control requirements. Since 

then, manufacturers have used two primary strategies to meet exhaust emission standards. The 

first is two-stroke direct injection. By injecting the fuel directly into the combustion chamber 

after the exhaust port closes, the short-circuiting fuel losses with traditional two-strokes can be 

largely eliminated. The second approach is to convert to using four-stroke engines, either 

carbureted or fuel-injected. One other approach that has been used by one PWC manufacturer 

has been the use of a two-way catalyst in the exhaust of a two-stroke engine. Today, engine 

sales are a mix of old and new technology. We anticipate that the standards will largely be met 

by phasing out the old-technology engines and using technology already available in the 

marketplace. 

Since California ARB has adopted standards similar to the new national standards, 

manufacturers have already started with design and testing efforts to meet our standards. To 

reflect this in the cost analysis, we include no estimated costs for R&D to introduce the various 

emission-control technologies. This reflects the expectation that manufacturers will not need to 

conduct additional R&D for EPA’s requirements, since they are introducing those technologies 

for sale in California. As noted below, we are including estimated R&D expenditures as part a 

compliance cost, because EPA’s NTE standards represent an incremental requirement beyond 

what California ARB has adopted. 

For the purpose of this analysis, we divide outboards into five power categories and PWC 

into three power categories. We present cost estimates of various emission-control technologies 

for each of these power categories. Additional detail on the per-engine costs presented in this 

section is available in the docket.29 Table 6.3-1 presents these power categories and the engine 

size we use to represent each category. 

Table 6.3-1: Engine Sizes Used for Cost Analysis 

Power Range Engine Power Displacement Cylinders 

Outboard Engines 0-25 hp 

25-50 hp 

50-100 hp 

100-175 hp 

>175 hp 

9.9 hp 

40 hp 

75 hp 

125 hp 

225 hp 

0.25 L 

0.76 L 

1.60 L 

1.80 L 

3.00 L 

2 

3 

3 

4 

6 

Personal 

Watercraft 

Engines 

50-100 hp 

100-175 hp 

>175 hp 

85 hp 

130 hp 

175 hp 

1.65 L 

1.85 L 

2.50 L 

2 

3 

4 

6-44 
Costs of Control 

6.3.1 Two-Stroke Direct Injection 

Traditional outboards use carbureted two-stroke engine designs where the fuel and air are 

mixed in the carburetor then pumped into the combustion chamber through the crankcase. The 

piston itself acts to open and close the intake and exhaust ports. As a result, fuel may be lost out 

the exhaust port. Better control of the fuel can be achieved using indirect injection in place of 

the carburetor; however, this does not prevent short-circuiting losses. Indirect injection is 

primarily used on the largest two-stroke engines. Direct-injection has been used by 

manufacturers to reduce emissions from two-stroke outboards. By injecting the fuel directly into 

the cylinder after the exhaust port is closed, short-circuiting losses can be minimized. 

Table 6.3-2 and 6.3-3 present incremental costs of applying direct injection to outboards and 

PWC, respectively. For the largest power category, costs are presented incremental to indirect 

injection. For the remaining categories, costs are presented incremental to carbureted engines. 

For 135 hp PWC engine, incremental costs are presented for both IDI and carbureted engines 

because baseline engines in this power category use both approaches. 

Table 6.3-2: Outboard—Projected Incremental Costs for 2-Stroke Direct Injection 

9.9 hp 

carb. 

40 hp 

carb. 

75 hp 

carb. 

125 hp 

carb. 

225 hp 

IDI 

Hardware Cost to Manufacturer

 carburetor(s)

 fuel metering solenoids 

IDI injectors

 fuel distributer

 pressure regulator

 air compressor

 air regulator

 throttle body position sensor

 intake manifold

 fuel pump

 electronic control module

 air intake temperature sensor

 manifold air pressure sensor

 injection timing sensor/timing wheel

 wiring/related hardware 

Total Incremental Hardware Cost 

($28) 

$36 

$80 

$15 

$30 

$5 

$3 

$85 

$5 

$10 

$5 

$20 

$266 

--

--

--

($114) 

$60 

$100 

$15 

$35 

$5 

$0 

$90 

$5 

$10 

$8 

$30 

$244 

--

--

--

($135) 

$66 

$120 

$17 

$35 

$9 

($5) 

$95 

$5 

$11 

$9 

$30 

$257 

--

--

--

($165) 

$96 

$140 

$20 

$40 

$10 

($6) 

$100 

$5 

$11 

$10 

$50 

$311 

--

--

--

--

$156 

($102) 

($25) 

($35) 

$165 

$22 

$10 

($5) 

($35) 

$0 

$0 

$0 

$0 

$0 

$151 

Engine Manufacturer Markup

 labor at $28/hour

 labor overhead at 40%

 markup at 29%

 warranty markup at 5% 

Total Incremental Component Cost 

$13 

$5 

$82 

$13 

$380 

$15 

$6 

$77 

$12 

$354 

$19 

$8 

$82 

$13 

$379 

$22 

$9 

$99 

$16 

$456 

$14 

$6 

$49 

$8 

$228 

6-45 
Final Regulatory Impact Analysis 

Table 6.3-3: PWC—Projected Incremental Costs for 2-Stroke Direct Injection 

85 hp 

carb. 

130 hp 

carb. 

130 hp 

IDI 

175 hp 

IDI 

Hardware Cost to Manufacturer

 carburetor(s)

 fuel metering solenoids 

IDI injectors

 fuel distributer

 pressure regulator

 air compressor

 air regulator

 throttle body position sensor

 intake manifold

 fuel pump

 electronic control module

 air intake temperature sensor

 manifold air pressure sensor

 injection timing sensor/timing wheel

 wiring/related hardware 

Total Incremental Hardware Cost 

($114) 

$44 

$120 

$17 

$35 

$9 

($5) 

$95 

$5 

$11 

$9 

$20 

$246 

--

--

--

($165) 

$72 

$140 

$20 

$40 

$10 

($6) 

$100 

$5 

$11 

$10 

$30 

$267 

--

--

--

--

$72 

($51) 

($20) 

($30) 

$140 

$20 

$0 

($10) 

($30) 

$0 

$0 

$0 

$0 

$0 

$91 

--

$104 

($68) 

($25) 

($35) 

$165 

$22 

$0 

($5) 

($35) 

$0 

$0 

$0 

$0 

$0 

$123 

Engine Manufacturer Markup

 labor at $28/hour

 labor overhead at 40%

 markup at 29%

 warranty markup at 5% 

Total Incremental Component Cost 

$19 

$8 

$79 

$12 

$364 

$22 

$9 

$86 

$13 

$398 

$12 

$5 

$31 

$5 

$144 

$12 

$5 

$41 

$6 

$186 

6-46 
Costs of Control 

6.3.2 Migration from Two-Stroke to Four-Stroke Engines 

The primary technology that manufacturers are using to meet exhaust emissions 

standards has been to convert their product offering more to four-stroke engines. Because fourstroke engines are common in the market today, we do not include costs for research and 

development or warranty. Rather, we anticipate that manufacturers will sell more of the fourstroke engines and phase out the carbureted two-stroke designs as a result of the new standards. 

Tables 6.3-4 and 6.3-5 below present a comparison between costs for two-stroke and four-stroke 

outboard and PWC engines, respectively. These costs are based on prices for current product 

offerings. 

Table 6.3-4: Outboard—Projected Incremental Costs for 4-Stroke 

9.9 hp 40 hp 75 hp 125 hp 225 hp 

2-stroke baseline technology 

4-stroke control technology 

carb 

carb 

carb 

carb 

carb 

carb 

carb 

EFI 

DFI 

EFI 

2-stroke cost 

4-stroke cost 

Markup at 29% 

$900 

$1,124 

$65 

$2,101 

$2,633 

$154 

$3,076 

$3,861 

$228 

$4,195 

$5,504 

$380 

$6,339 

$7,761 

$412 

Total Incremental Cost $289 $686 $1,013 $1,689 $1,834 

Table 6.3-5: PWC—Projected Incremental Costs for 4-Stroke 

85 hp 130 hp 175 hp 

2-stroke baseline technology 

4-stroke control technology 

carb 

EFI 

DFI 

EFI 

DFI 

EFI 

2-stroke cost 

4-stroke cost 

Markup at 29% 

$3,319 

$4,350 

$299 

$4,578 

$5,587 

$293 

$5,862 

$7,207 

$390 

Total Incremental Cost $1,330 $1,302 $1,735 

6-47 
Final Regulatory Impact Analysis 

6.3.3 Four-Stroke Electronic Fuel Injection 

Manufacturers can gain better control of their fuel and air management through the use of 

electronic fuel injection. This is often used in larger OB/PWC engines today. For this analysis, 

we consider the use of a port fuel-injection system, which refers to individual injectors located at 

each intake port in the engine. In addition to the injectors, this system includes a fuel rail, 

pressure regulator, electronic control module, manifold air pressure and temperature sensors, a 

high pressure fuel pump, a throttle assembly, a throttle position sensor, and a magnetic 

crankshaft pickup for engine speed. Tables 6.3-6 and 6.3-7 present the incremental costs of a 

port fuel-injection system compared to a carburetor-based fuel system for outboards and personal 

watercraft, respectively. 

Table 6.3-6: Outboard—Projected Incremental Costs for 4-Stroke EFI 

9.9 hp 40 hp 75 hp 125 hp 225 hp 

Hardware Costs

 carburetor(s)

 injectors

 fuel rail

 pressure regulator

 intake manifold

 throttle body position sensor

 fuel pump

 electronic control module

 air intake temperature sensor

 manifold air pressure sensor

 injection timing sensor

 wiring/related hardware 

Hardware Cost to Manufacturer 

($28) 

$34 

$40 

$15 

$5 

$30 

$13 

$95 

$5 

$10 

$5 

$20 

$244 

($114) 

$51 

$55 

$15 

$5 

$35 

$10 

$100 

$5 

$10 

$8 

$30 

$210 

($135) 

$51 

$65 

$20 

$6 

$35 

$10 

$105 

$5 

$11 

$9 

$30 

$212 

($165) 

$68 

$70 

$30 

$10 

$40 

$14 

$110 

$5 

$11 

$10 

$40 

$243 

($240) 

$102 

$80 

$35 

$15 

$50 

$17 

$115 

$5 

$11 

$10 

$60 

$260 

Engine Manufacturer Markup

 labor at $28/hour

 labor overhead at 40%

 markup at 29%

 warranty markup at 5% 

Total Incremental Component Cost 

$3 

$1 

$72 

$12 

$332 

$4 

$2 

$63 

$11 

$289 

$4 

$2 

$63 

$11 

$291 

$4 

$2 

$72 

$12 

$333 

$4 

$2 

$77 

$13 

$356 

6-48 
Costs of Control 

Table 6.3-7: PWC—Projected Incremental Costs for 4-Stroke EFI 

85 hp 130 hp 175 hp 

Hardware Costs

 carburetor(s)

 injectors

 fuel rail

 pressure regulator

 intake manifold

 throttle body position sensor

 fuel pump

 electronic control module

 air intake temperature sensor

 manifold air pressure sensor

 injection timing sensor

 wiring/related hardware 

Hardware Cost to Manufacturer 

($135) 

$34 

$65 

$20 

$6 

$35 

$10 

$105 

$5 

$11 

$9 

$20 

$185 

($165) 

$51 

$70 

$30 

$10 

$40 

$14 

$110 

$5 

$11 

$10 

$30 

$216 

($240) 

$68 

$80 

$35 

$15 

$50 

$17 

$115 

$5 

$11 

$10 

$40 

$206 

Engine Manufacturer Markup

 labor at $28/hour

 labor overhead at 40%

 markup at 29%

 warranty markup at 5% 

Total Incremental Component Cost 

$4 

$2 

$55 

$9 

$255 

$4 

$2 

$64 

$11 

$297 

$4 

$2 

$61 

$10 

$283 

6-49 
Final Regulatory Impact Analysis 

6.3.4 Catalysts 

We believe the OB/PWC exhaust emission standards can be achieved without the use of 

catalysts. At this time, three-way catalysts have not been demonstrated on OB/PWC engines. 

However, one manufacturer has been using a two-way catalyst on PWCs with 2-stroke engines 

for several years. We include research and development costs for this technology because it is 

not currently used in the marine industry, but is an alternative we assess in Chapter 11. Catalyst 

sizes and formulations are based on the analysis discussed below for SD/I engines. Tables 6.3-8 

and 6.3-9 present the incremental cost of adding catalysts to four-stroke, electronic fuel-injection 

OB and PWC engines, respectively. 

Table 6.3-8: Outboard—Projected Incremental Costs for Catalytic Control 

9.9 hp 40 hp 75 hp 125 hp 225 hp 

Catalyst Unit Price

 catalyst volume (L)

 substrate diameter (cm)

 substrate

 ceria/alumina

 Pt/Pd/Rd

 can (18 gauge SS) 

Total Material Cost 

Labor

 labor overhead at 40%

 supplier markup at 29% 

Manufacturer Price per Unit 

0.09 

4.5 

$2 

$1 

$2 

$0.4 

$6 

$14 

$6 

$8 

$33 

0.27 

6.0 

$4 

$3 

$7 

$0.8 

$15 

$14 

$6 

$10 

$45 

0.56 

8.5 

$5 

$6 

$16 

$1 

$29 

$14 

$6 

$14 

$62 

0.63 

9.0 

$6 

$7 

$18 

$1 

$32 

$14 

$6 

$15 

$67 

1.05 

10.0 

$8 

$12 

$29 

$2 

$52 

$14 

$6 

$21 

$92 

Hardware Cost to Manufacturer

 catalyst

 exhaust manifold modifications

 oxygen sensor 

Total Incremental Hardware Cost 

$33 

$15 

$25 

$73 

$45 

$17 

$25 

$87 

$62 

$20 

$25 

$107 

$67 

$25 

$25 

$117 

$92 

$30 

$25 

$147 

Engine Manufacturer Markup

 labor at $28/hour

 labor overhead at 40%

 markup at 29%

 warranty markup at 5% 

Total Incremental Component Cost 

$1 

$1 

$22 

$2 

$99 

$1 

$1 

$26 

$2 

$116 

$1 

$1 

$32 

$2 

$143 

$1 

$1 

$34 

$3 

$156 

$1 

$1 

$43 

$3 

$195 

Fixed Cost to Manufacturer

 research & development

 tooling

 units/year

 years to recover 

Fixed Cost/Unit 

$342,788 

$75,000 

5,000 

5 

$23 

$352,938 

$75,000 

5,600 

5 

$21 

$362,068 

$75,000 

6,400 

5 

$19 

$372,980 

$75,000 

5,900 

5 

$21 

$388,643 

$75,000 

4,700 

5 

$27 

Total Incremental Cost $122 $137 $162 $177 $222 

6-50 
Costs of Control 

Table 6.3-9: PWC—Projected Incremental Costs for Catalytic Control 

85 hp 130 hp 175 hp 

Catalyst Unit Price

 catalyst volume (L)

 substrate diameter (cm)

 substrate

 ceria/alumina

 Pt/Pd/Rd

 can (18 gauge SS) 

Total Material Cost 

Labor

 labor overhead at 40%

 supplier markup at 29% 

Manufacturer Price per Unit 

0.58 

9.0 

$5 

$7 

$16 

$1 

$30 

$14 

$6 

$14 

$63 

0.65 

9.0 

$6 

$7 

$18 

$1 

$33 

$14 

$6 

$15 

$68 

0.88 

9.0 

$7 

$10 

$25 

$2 

$44 

$14 

$6 

$18 

$82 

Hardware Cost to Manufacturer

 catalyst

 exhaust manifold modifications

 oxygen sensor 

Total Incremental Hardware Cost 

$63 

$35 

$25 

$123 

$68 

$40 

$25 

$133 

$82 

$45 

$25 

$152 

Engine Manufacturer Markup

 labor at $28/hour

 labor overhead at 40%

 markup at 29%

 warranty markup at 5% 

Total Incremental Component Cost 

$1 

$1 

$36 

$3 

$165 

$1 

$1 

$39 

$3 

$177 

$1 

$1 

$45 

$4 

$202 

Fixed Cost to Manufacturer

 research & development

 tooling

 units/year

 years to recover 

Fixed Cost/Unit 

$363,502 

$75,000 

1,700 

5 

$71 

$371,332 

$75,000 

5,300 

5 

$23 

$381,016 

$75,000 

1,000 

5 

$126 

Total Incremental Cost $236 $200 $328 

6.3.5 Certification and Compliance 

Outboard and PWC engines must already be certified to meet the current EPA HC+NOx 

exhaust emission standards. We therefore do not anticipate any increase in clerical work 

associated with these standards. In addition, manufacturers are likely to meet the new standards 

by selling more of their lower-emission engines, which are certified today. However, 

manufacturers may need to adjust engine calibrations to meet the new standard and collect 

further data to demonstrate compliance with the not-to-exceed zone. We therefore allow on 

average two months of R&D for each engine family as part of the certification process. 

Considering two engineers and three technicians and the corresponding testing costs for the two6-51 
Final Regulatory Impact Analysis 

month period, we estimate a total cost of $130,000 per engine family. Unless engine designs 

were significantly changed, manufacturers could recertify engine families each year using 

carryover of this original test data. If this cost is amortized over five years of engine sales with 

an average volume of 5,500 engines per family for outboards and 4,200 engines per family for 

PWC, the resulting cost is $5 per engine for outboards and $6 for PWC. 

6.3.6 Operating Cost Savings 

We anticipate that the standards will largely be met on average by phasing out old, highemitting technologies, such as carbureted two-stroke engines and replacing them with currently 

available clean technologies such as four-stroke engines and direct-injection two-stroke engines. 

In addition to having lower emissions, these newer-technology engines have significantly lower 

fuel consumption. Over the life of an engine, these fuel savings result in significant operating 

cost savings. In calculating the fuel savings, we use a gasoline price of $1.81 per gallon without 

taxes.30 

The largest portion of the fuel savings would come from phasing out carbureted 

crankcase-scavenged two-stroke engines. As discussed in Chapter 4, scavenging losses from 

these engines can result in more than 25 percent of the fuel passing through the engine unburned. 

In addition, we model incremental fuel-consumption benefits between fuel-injected two-stroke 

engines, carbureted four-stroke engines, and fuel-injected four strokes. These fuel consumption 

rates and their derivation are described in more detail in the docket.31 

Table 6.3-10: Projected Fuel Savings for OB/PWC Engines 

Outboard PWC 

Annual Per-Engine Gallons Consumed 72 225 

Average Life (years) 19 9.9 

Anticipated Reduction in Fuel Consumption 5.2% 4.7% 

Lifetime Gallons Saved 72 103 

Lifetime Cost Savings $130 $187 

Discounted Cost Savings (7%) $75 $142 

6.3.7 Total OB/PWC Engine Costs 

As discussed above, we anticipate that manufacturers would meet the standards largely 

by changing their technology mix from older to newer technologies. For this reason, our 

estimated per-engine costs for the average OB/PWC engine reflect a mix of technology changes. 

Table 6.3-11 presents the baseline technology mix by power class. This technology mix is based 

on an analysis of sales projections submitted to EPA by OB/PWC manufacturers at time of 

certification. These sales projections are confidential, but a general description of this analysis is 

6-52 
Costs of Control 

available in the docket.32 

Table 6.3-11: Baseline Technology Mix for OB/PWC Engines 

2-Stroke 

Carbureted 

2-Stroke 

Indirect Injection 

2-Stroke 

Direct Injection 

4-Stroke 

Carbureted 

4-Stroke 

Fuel Injection 

Outboards

 9.9 hp

 40 hp

 75 hp

 125 hp

 225 hp 

24% 

32% 

20% 

20% 

0% 

0% 

0% 

0% 

0% 

25% 

0% 

2% 

10% 

30% 

60% 

76% 

35% 

0% 

0% 

0% 

0% 

32% 

70% 

50% 

15% 

PWC

 85 hp

 130 hp

 175 hp 

30% 

5% 

0% 

60% 

0% 

70% 

10% 

5% 

30% 

0% 

0% 

0% 

0% 

90% 

0% 

To develop the control technology mix, we made three adjustments to the baseline 

technology mix. First, we considered that all the 2-stroke carbureted and indirect injection 

engines would be replaced by either 2-stroke direct injection or 4-stroke engines. Second, we 

included calibration costs for the for the 2-stroke direct injection and 4-stroke engines for better 

emission performance. These engines are well below the existing HC+NOx standards; however, 

there is currently wide variability in certified emission levels. We believe the standards will 

require engine manufacturers to pay closer attention to emissions calibrations for their higheremitting new technology engines. Third, we included the conversion of a small number of 2-

stroke direct injection engines to 4-stroke based on product plans conveyed to us in private 

conversations with manufacturers. While there is no way of knowing exactly what the actual 

technology mix will be, we believe our analysis represents a reasonable scenario. Table 6.3-12 

presents the projected technology mix for this control scenario. 

6-53 
Final Regulatory Impact Analysis 

Table 6.3-12: Projected Control Technology Mix for OB/PWC Engines 

2-Stroke 

Carbureted 

2-Stroke 

Indirect Injection 

2-Stroke 

Direct Injection 

4-Stroke 

Carbureted 

4-Stroke 

Fuel Injection 

Outboards

 9.9 hp

 40 hp

 75 hp

 125 hp

 225 hp 

0% 

0% 

0% 

0% 

0% 

0% 

0% 

0% 

0% 

0% 

0% 

2% 

10% 

30% 

50% 

100% 

66% 

20% 

0% 

0% 

0% 

32% 

70% 

70% 

50% 

PWC

 85 hp

 130 hp

 175 hp 

0% 

0% 

0% 

0% 

0% 

0% 

0% 

5% 

30% 

100% 

0% 

0% 

0% 

95% 

70% 

We developed the per-engine costs based on the technology mix and technology cost 

tables presented above. As discussed above, our cost estimates include both variable and fixed, 

and we distinguish between near-term and long-term costs. Because our analysis amortizes fixed 

costs over 5 years, the long-term costs are made up of variable costs only. Variable costs are 

lower in the long term due to the learning effect discussed above. Table 6.3-13 presents these 

average per-engine cost estimates. 

Table 6.3-13: OB/PWC Per-Engine Cost Estimates (Without Fuel Savings) 

Short Term (years 1-5) Long Term (years 

6-10) Fixed Variable Total 

OB aggregate

 9.9 hp

 40 hp

 75 hp

 125 hp

 225 hp 

$11 

$5 

$5 

$8 

$15 

$27 

$280 

$69 

$216 

$203 

$338 

$690 

$291 

$74 

$222 

$210 

$353 

$717 

$224 

$55 

$173 

$162 

$270 

$552 

PWC aggregate

 85 hp

 130 hp

 175 hp 

$19 

$29 

$14 

$45 

$340 

$870 

$85 

$1,290 

$359 

$899 

$98 

$1,336 

$272 

$696 

$68 

$1,032 

6.3.8 OB/PWC Aggregate Costs 

Aggregate costs are calculated by multiplying the per-engine variable cost estimates 

described above by projected engine sales. These variable costs are then added to the fixed costs 

6-54 
Costs of Control 

as incurred. Engine sales are based on estimates supplied by the National Marine Manufacturers 

Association (www.nmma.org) and projections for future years are based on the growth rates in 

the NONROAD model. Fuel-consumption reductions are calculated using the NONROAD 

based on population estimates. These population estimates in the NONROAD model are similar 

to those estimated by NMMA. A description of the sales and population data and our analysis of 

the data are available in the docket.33 Table 6.3-14 presents the projected costs of meeting the 

exhaust emission standards over a 30-year time period, with and without the fuel savings. Fuel 

savings from the evaporative emission standards are not included in this table, but they are 

presented separately below. 

The population and sales data reported by NMMA, suggest that the NONROAD model 

may somewhat underestimate the useful life of outboard and personal watercraft marine engines. 

If useful life were back-calculated—dividing NMMA population by sales and adjusted for 

growth—we would get a longer average life estimate. As a result, the per-engine fuel savings 

described above may be understated. Because the current approach gives us a conservative 

benefits estimate, and because we do not have new data on average lives for marine engines to 

update the estimates in the NONROAD model, we are not updating the model at this time. For 

this reason, the 30-year stream may give a better view of the impact of the fuel savings than the 

per-engine analysis. 

At a 7 percent discount rate, over 30 years, the estimated annualized cost to 

manufacturers for OB/PWC exhaust emission control is $95 million. The corresponding 

estimated annualized fuel savings due to more efficient engines is $48 million. At a 3 percent 

discount rate, the estimated annualized cost to manufacturers for OB/PWC exhaust emission 

control is $95 million. The corresponding estimated annualized fuel savings due to more 

efficient engines is $57 million. 

6-55 
Final Regulatory Impact Analysis 

Table 6.3-14: Projected 30-Year Aggregate Cost Stream for OB/PWC Engines 

Year 

Without Fuel Savings With Fuel Savings 

OB PWC OB PWC 

2008 

2009 

2010 

2011 

2012 

2013 

2014 

2015 

2016 

2017 

2018 

2019 

2020 

2021 

2022 

2023 

2024 

2025 

2026 

2027 

2028 

2029 

2030 

2031 

2032 

2033 

2034 

2035 

2036 

2037

 $8,347,493 

$8,347,493 

$83,474,059 

$84,087,276 

$84,700,492 

$85,313,708 

$85,926,924 

$69,232,112 

$69,716,553 

$70,200,994 

$70,685,435 

$71,169,876 

$71,654,317 

$72,138,757 

$72,623,198 

$73,107,639 

$73,592,080 

$74,076,521 

$74,564,028 

$75,051,534 

$75,539,041 

$76,026,548 

$76,514,055 

$77,001,562 

$77,489,069 

$77,976,576 

$78,464,083 

$78,951,590 

$79,439,097 

$79,926,603 

$3,773,815 

$3,773,815 

$26,775,058 

$26,971,752 

$27,168,447 

$27,365,142 

$27,561,836 

$22,206,825 

$22,362,213 

$22,517,602 

$22,672,991 

$22,828,380 

$22,983,769 

$23,139,157 

$23,294,546 

$23,449,935 

$23,605,324 

$23,760,712 

$23,917,085 

$24,073,457 

$24,229,829 

$24,386,201 

$24,542,574 

$24,698,946 

$24,855,318 

$25,011,690 

$25,168,062 

$25,324,435 

$25,480,807 

$25,637,179 

$8,347,493 

$8,347,493 

$79,497,283 

$76,139,850 

$72,816,127 

$69,526,261 

$66,259,388 

$45,684,931 

$42,316,350 

$38,991,304 

$35,708,089 

$32,473,153 

$29,314,449 

$26,232,921 

$23,265,756 

$20,500,653 

$18,356,730 

$16,648,131 

$15,128,141 

$13,767,757 

$12,656,743 

$11,676,039 

$10,870,140 

$10,196,651 

$9,613,547 

$9,148,071 

$8,757,202 

$8,450,580 

$8,228,217 

$8,059,025 

$3,773,815 

$3,773,815 

$24,485,325 

$22,376,416 

$20,292,925 

$18,241,565 

$16,224,620 

$8,714,463 

$6,764,827 

$4,885,794 

$3,100,364 

$1,454,031 

$587,570 

$(9,566)

 $(471,718)

 $(844,125)

 $(1,149,312)

 $(1,387,033)

 $(1,568,545)

 $(1,705,040)

 $(1,796,384)

 $(1,842,344)

 $(1,854,155)

 $(1,865,959)

 $(1,877,784)

 $(1,889,601)

 $(1,901,412)

 $(1,913,224)

 $(1,925,042)

 $(1,936,853) 

6.4 Exhaust Emission Control Costs for Sterndrive/Inboard Marine 

Engines 

This section presents our cost estimates for meeting the new exhaust emission standards 

for sterndrive and inboard marine engines. 

Sterndrive and inboard (SD/I) marine engines are typically “marinized” using automotive 

engine blocks. There are a few exceptions where unique engine blocks are used, but these 

applications represent a very small portion of the sales volume. Typical automotive blocks are 

3.0 liter in-line 4-cylinder engines, 4.3 liter V-6 engines, and V-8 engines ranging from 5.0 to 8.2 

liters total displacement. For purposes of this analysis, we present costs for an in-line 4 cylinder 

engine, a V-6 engine, and three V-8 engine configurations. In addition, this analysis considers 

costs to the original engine manufacturer and to the engine “marinizer.” Additional detail on the 

6-56 
Costs of Control 

projected costs may be found in the docket.34 

Because California ARB has adopted standards similar to the new national standards, 

manufacturers have already started with design and testing efforts to meet our standards. To 

reflect this in the cost analysis, we include no estimated costs for R&D to introduce the various 

emission-control technologies. This reflects the expectation that manufacturers will not need to 

conduct additional R&D for EPA’s requirements, since they are introducing those technologies 

for sale in California. As noted below, we are including estimated R&D expenditures as part a 

compliance cost, because EPA’s NTE standards represent an incremental requirement beyond 

what California ARB has adopted. 

6.4.1 Fuel Injection 

Current SD/I engines are sold with carburetors or with fuel-injection systems. The 

smaller 3.0 L I4 engines are typically carbureted while the larger 8.1 and 8.2 L V8 engines are 

typically fuel injected. Our estimate is that about 25-30 percent of V6 engines and 70-80 percent 

of the 5.0 - 6.2L V8 engines are currently sold with fuel injection. For the purpose of this 

analysis we anticipate that all SD/I engines will need to be fuel injected to meet the new 

emission standards. Fuel injection allows better control of the air-to-fuel ratio in the engine and 

exhaust for better emission design control and catalyst efficiency. 

We consider the use of a port fuel-injection system for this analysis, which refers to 

individual injectors located at each intake port in the engine. In addition to the injectors, this 

system includes a fuel rail, pressure regulator, electronic control module, manifold air pressure 

and temperature sensors, a high pressure fuel pump, a throttle assembly, a throttle position 

sensor, and a magnetic crankshaft pickup for engine speed. We also consider a cool fuel system 

to prevent the occurrence of vapor lock in the fuel lines. Table 6.4-1 presents the incremental 

costs of a port fuel-injection system compared to a carburetor-based fuel system. Because this 

technology is widely used today, we include fixed costs for final calibrations as part of the cost 

of certification and compliance in Section 6.4.4. 

6-57 
Final Regulatory Impact Analysis 

Table 6.4-1: Projected Incremental Hardware Costs for Controlled Port Fuel Injection 

3.0L I4 4.3L V6 5.0L V8 5.7L V8 8.1L V8 

Hardware Cost to Manufacturer

 carburetor

 injectors

 pressure regulator

 fuel filter

 intake manifold

 fuel rail

 throttle assembly (w/ position sensor)

 cool fuel system (w/ pump)

 electronic control module

 air intake temperature sensor

 manifold air pressure sensor

 crank position sensor

 wiring/related hardware 

Total Incremental Hardware Cost 

($140) 

$68 

$15 

$1 

$14 

$80 

$150 

$115 

$70 

$5 

$14 

$16 

$80 

$488 

($145) 

$102 

$15 

$1 

$25 

$80 

$150 

$120 

$65 

$5 

$14 

$16 

$80 

$528 

($145) 

$136 

$15 

$1 

$25 

$80 

$150 

$120 

$65 

$5 

$14 

$16 

$80 

$562 

($145) 

$136 

$15 

$1 

$30 

$80 

$150 

$120 

$65 

$5 

$14 

$16 

$80 

$567 

($145) 

$160 

$15 

$1 

$40 

$80 

$60 

$120 

$60 

$5 

$14 

$16 

$80 

$506 

Engine Manufacturer Markup

 labor at $28/hr

 labor overhead at 40%

 markup at 29%

 warranty markup at 5% 

Total Incremental Component Cost 

$3 

$1 

$143 

$24 

$659 

$4 

$2 

$155 

$26 

$715 

$4 

$2 

$165 

$28 

$760 

$4 

$2 

$166 

$28 

$767 

$4 

$2 

$148 

$25 

$685 

6-58 
Costs of Control 

6.4.2 Exhaust Gas Recirculation 

We do not anticipate that manufacturers will use exhaust gas recirculation (EGR) to meet 

the exhaust emission standards. However, in developing this rule, we considered the option of a 

standard based on emission reductions possible through the use of EGR. This analysis is 

reflected in our alternatives discussion in Chapter 11. For this analysis, we consider an EGR 

system with a valve, plumbing, and modification to the intake manifold. Table 6.4-2 presents 

incremental variable costs of a controlled engine with EGR compared to an uncontrolled engine 

with port fuel injection and no EGR. 

Table 6.4-2: Projected Incremental Hardware Costs for Exhaust Gas Recirculation 

3.0L I4 4.3L V6 5.0L V8 5.7L V8 8.1L V8 

Hardware Cost to Manufacturer

 intake manifold

 exhaust gas recirculation

 exhaust manifold

 oxygen sensors 

Total Incremental Hardware Cost 

$5 

$25 

$2 

$17 

$49 

$5 

$25 

$5 

$34 

$69 

$10 

$25 

$5 

$34 

$74 

$10 

$25 

$5 

$34 

$74 

$10 

$25 

$5 

$34 

$74 

Engine Manufacturer Markup

 labor at $28/hr

 labor overhead at 40%

 markup at 29%

 warranty markup at 5% 

Total Incremental Component Cost 

$1 

$0 

$15 

$2 

$67 

$1 

$0 

$20 

$3 

$94 

$1 

$0 

$22 

$4 

$101 

$1 

$0 

$22 

$4 

$101 

$1 

$0 

$22 

$4 

$101 

6-59 
Final Regulatory Impact Analysis 

6.4.3 Catalysts 

We anticipate that manufacturers will use small three-way catalysts to meet the SD/I 

exhaust emission standards. A catalyst will likely be placed in the riser of each exhaust manifold 

upstream of where the water and exhaust gases mix. Catalyst sizes and configurations are based 

on the developmental catalyst efforts on SD/I engines discussed in Chapter 4. Costs are included 

to modify the exhaust manifolds for packaging of the catalyst. We believe these catalysts will be 

used in conjunction with port fuel injection and closed-loop electronic control. Therefore, we 

include the cost of an oxygen sensor upstream of each catalyst. The costs in Table 6.4-3 are 

presented incremental to an open-loop port fuel injection. 

Table 6.4-3: Projected Incremental Hardware Costs for Catalytic Control 

3.0L I4 4.3L V6 5.0L V8 5.7L V8 8.1L V8 

Catalyst Unit Price

 catalyst volume (L) (each)

 number of catalysts

 substrate diameter (cm)

 substrate

 ceria/alumina

 Pt/Pd/Rd

 can (18 gauge SS) 

Total Material Cost

 labor at $28/hr

 labor overhead at 40%

 supplier markup at 29% 

Manufacturer Price per Unit 

1.00 

1 

9.5 

$8 

$11 

$28 

$3 

$51 

$5 

$2 

$17 

$74 

0.75 

2 

8.3 

$7 

$9 

$21 

$3 

$39 

$5 

$2 

$13 

$59 

0.88 

2 

9.0 

$7 

$10 

$25 

$3 

$45 

$5 

$2 

$15 

$66 

1.00 

2 

9.5 

$8 

$11 

$28 

$3 

$51 

$5 

$2 

$17 

$74 

1.40 

2 

11.0 

$10 

$16 

$39 

$4 

$69 

$5 

$2 

$22 

$98 

Hardware Cost to Manufacturer

 catalysts

 oxygen sensors

 exhaust manifold 

Total Incremental Hardware Cost 

$74 

$17 

$10 

$101 

$119 

$34 

$20 

$173 

$132 

$34 

$20 

$186 

$148 

$34 

$25 

$207 

$195 

$34 

$30 

$259 

Engine Manufacturer Markup

 labor at $28/hr

 labor overhead at 40%

 markup at 29%

 warranty markup at 5% 

Total Incremental Component Cost 

$2 

$1 

$30 

$5 

$139 

$1 

$0 

$50 

$9 

$233 

$1 

$0 

$54 

$9 

$251 

$1 

$0 

$60 

$10 

$279 

$1 

$0 

$76 

$13 

$349 

As discussed above, we do not include research and development costs in our fixed costs 

for SD/I engines. However, we do include tooling costs that would be associated with ramping 

up production of California engines for the entire United States. These tooling costs are 

presented in Table 6.4-4. 

6-60 
Costs of Control 

Table 6.4-4: Projected Incremental Tooling Costs for Catalytic Control 

3.0L I4 4.3L V6 5.0L V8 5.7L V8 8.1L V8 

Fixed Costs to Engine Manufacturer

 tooling

 units/year

 years to recover

 fixed costs/unit 

$30,000 

15,000 

5 

$1 

$35,000 

15,000 

5 

$1 

$40,000 

15,000 

5 

$1 

$40,000 

15,000 

5 

$1 

$45,000 

15,000 

5 

$1 

Fixed Costs to Engine Marinizer

 tooling

 units/year

 years to recover

 fixed costs/unit 

$35,000 

2,000 

5 

$5 

$45,000 

2,000 

5 

$6 

$50,000 

2,000 

5 

$7 

$55,000 

2,000 

5 

$7 

$55,000 

1,000 

5 

$14 

Total Incremental Fixed Costs $5 $6 $7 $8 $15 

6.4.4 Certification and Compliance 

We estimate that certification costs for SD/I engines would come to about $130,000 per 

engine family. We expect that manufacturers would combine similar engines into the same 

family. The above certification cost estimate allows for two months of R&D for each engine 

family as part of the certification process. This would include two engineers and three 

technicians and the corresponding testing costs for the two-month period. Unless engine designs 

were significantly changed, engine families could be recertified each year using carryover of this 

original test data. If this cost is amortized over five years of engine sales with an average 

volume of 2,000 engines per family, the resulting cost is $13 per engine. 

6.4.5 Operating Cost Savings 

We anticipate that manufacturers will convert their remaining carbureted engines to fuel 

injection to meet the new standards. We believe this will result in fuel savings because of the 

better fuel control offered by fuel injection compared to carburetion. The fuel consumption rates 

we use for carbureted and fuel injected SD/I engines and their derivation are described in more 

detail in the docket.35 We use the price of gasoline discussed earlier in this chapter. 

6-61 
Final Regulatory Impact Analysis 

Table 6.4-5: Projected Fuel Savings for SD/I Engines 

Annual Per-Engine Gallons Consumed 228 

Average Life (years) 19.7 

Anticipated Reduction in Fuel Consumption 2.3% 

Lifetime Gallons Saved 101 

Lifetime Cost Savings $185 

Discounted Cost Savings (7%) $105 

6.4.6 Total SD/I Engine Costs 

We expect that SD/I engine manufacturers would use catalytic convertors and electronic 

fuel injection to meet the standards. In 2003, about 60 percent of SD/I engines were sold with 

electronic fuel injection. This estimate is based on confidential sales information submitted to 

the California Air Resources Board by SD/I manufacturers certifying to the 2003 California 

exhaust emission standards. The manufacturers who certified in California represent more than 

90 percent of U.S. sales of SD/I engines. Manufacturers have indicated to us that they are 

moving in the direction of selling more fuel-injected engines and using carburetors only on their 

low-cost “introductory” engines. For this cost analysis, we use the projected technology mix for 

2009 from the NONROAD model which projects that about 85 percent of SD/I engines sold will 

be fuel-injected. Table 6.4-6 presents our estimates of the sales mix between carbureted and fuelinjected SD/I engines. 

Table 6.4-6: Baseline Technology Mix for SD/I Engines 

2003 MY California Certification Projected 2009 Baseline 

Carbureted Fuel Injection Carbureted Fuel Injection 

3.0L I-4 

4.3L V-6 

5.0L V-8 

5.7L V-8 

8.1L V-8 

high performance 

100% 

75% 

40% 

10% 

100% 

--

0% 

25% 

60% 

90% 

0% 

--

50% 

20% 

5% 

0% 

0% 

50% 

50% 

80% 

95% 

100% 

100% 

50% 

We developed the per-engine costs by assigning costs for electronic fuel injection for 

engine models that are projected to be carbureted in 2009. Except for high-performance engines, 

we also apply costs for catalysts. As discussed above, our cost estimates include both variable 

and fixed costs, and we distinguish between near-term and long-term costs. Because our 

analysis amortizes fixed costs over 5 years, the long-term costs are made up of variable costs 

only. These variable costs are lower in the long term due to the learning effect discussed above. 

6-62 
Costs of Control 

Table 6.4-7 presents these average per-engine cost estimates. Fixed costs for high-performance 

engines were based on an engine family size of 50 engines, compared to 2,000 engines for 

traditional SD/I engines. 

Table 6.4-7: SD/I Per-Engine Cost Estimates (Without Fuel Savings) 

Short Term (years 1-5) Long Term (years 

6-10) Fixed Variable Total 

SD/I Aggregate 

3.0L 

4.3L 

5.0L 

5.7L 

8.1L 

high performance 

$21

 $18 

$19 

$20 

$21 

$28 

$280 

$334

 $465 

$377 

$297 

$279 

$349 

$257 

$355

 $483 

$396 

$317 

$300 

$377

 $537 

$266

 $372 

$301 

$238 

$223 

$279 

$216 

6.4.7 SD/I Aggregate Costs 

Aggregate costs are calculated by multiplying the per-engine variable cost estimates 

described above by projected engine sales. These variable costs are then added to the fixed costs 

as incurred. Engine sales are based on estimates supplied by the National Marine Manufacturers 

Association (www.nmma.org) and projections for future years are based on the growth rates in 

the NONROAD model. Fuel consumption reductions are calculated using the NONROAD 

based on population estimates. These population estimates in the NONROAD model are similar 

to those estimated by NMMA. A description of the sales and population data and our analysis of 

the data is available in the docket.36 Table 6.4-8 presents the projected costs of the rule over a 

30-year time period with and without the fuel savings that would be expected from meeting the 

exhaust emission standards. Fuel savings from the evaporative emission standards are not 

included in this table, but they are presented separately below. 

At a 7 percent discount rate, over 30 years, the estimated annualized cost to 

manufacturers for SD/I exhaust emission control is $28 million. The corresponding estimated 

annualized fuel savings due to more efficient engine controls is $8 million. At a 3 percent 

discount rate, over 30 years, the estimated annualized cost to manufacturers for SD/I exhaust 

emission control is $28 million. The corresponding estimated annualized fuel savings due to 

more efficient engine controls is $10 million. 

6-63 
Final Regulatory Impact Analysis 

Table 6.4-8: Projected 30-Year Aggregate Cost Stream for SD/I Engines 

Year Without Fuel Savings With Fuel Savings 

2008 

2009 

2010 

2011 

2012 

2013 

2014 

2015 

2016 

2017 

2018 

2019 

2020 

2021 

2022 

2023 

2024 

2025 

2026 

2027 

2028 

2029 

2030 

2031 

2032 

2033 

2034 

2035 

2036 

2037

 $4,971,723 

$4,971,723 

$31,909,535 

$32,143,949 

$32,378,362 

$32,612,775 

$32,847,189 

$26,361,975 

$26,546,438 

$26,730,902 

$26,915,366 

$27,099,830 

$27,284,293 

$27,468,757 

$27,653,221 

$27,837,685 

$28,022,149 

$28,206,612 

$28,392,244 

$28,577,875 

$28,763,506 

$28,949,137 

$29,134,769 

$29,320,400 

$29,506,031 

$29,691,662 

$29,877,294 

$30,062,925 

$30,248,556 

$30,434,187 

$4,971,723 

$4,971,723 

$31,207,005 

$30,512,049 

$29,822,674 

$29,128,682 

$28,440,869 

$21,040,258 

$20,317,643 

$19,601,606 

$18,896,409 

$18,205,484 

$17,523,304 

$16,828,978 

$16,141,908 

$15,467,722 

$14,804,334 

$14,154,769 

$13,524,906 

$12,917,862 

$12,338,401 

$11,804,572 

$11,474,294 

$11,259,905 

$11,088,594 

$10,948,483 

$10,831,791 

$10,732,954 

$10,650,884 

$10,582,255 

6.5 Evaporative Emission Control Costs for Small SI Equipment 

This section presents our cost estimates for meeting the new evaporative emission 

standards for land-based equipment using small spark-ignition engines. 

In our analysis of the costs of the evaporative emission standards for Small SI equipment, 

we consider the approximately 250 equipment types used in the NONROAD model to determine 

emission inventories. These equipment types are then aggregated into the five engine classes, 

with each class divided by general equipment types and between residential and commercial 

applications. For each of these aggregate categories, we determine weighted average hose 

lengths and tank sizes which we use as inputs to our cost calculations. These inputs are 

presented in more detail in the evaporative emission inventory discussion in Chapter 3. This 

discussion presents our cost estimates as a function of hose length and tank size. In addition, we 

present examples of costs for four typical Small SI equipment configurations which include a 

handheld (HH) configuration, a walk-behind mower (WBM), and two other non-handheld 

6-64 
Costs of Control 

(NHH) configurations. These configurations, which are presented in Table 6.5-1, are based on 

average tank sizes and hose lengths used in our inventory model (see Chapter 3). Although these 

typical configurations do not, by any means, represent all of the equipment types included in our 

cost calculations, they should give a good indication of how we performed our analysis. 

Table 6.5-1: Typical Small SI Equipment Configurations 

HH WBM NHH #1 NHH #2 

Fuel Tank Capacity (gallons) 

Fuel Tank Material* 

Fuel Tank Molding Process 

Fuel Tank Weight (lbs.) 

0.25 

HDPE 

IM/BM 

0.6 

0.5 

HDPE 

IM/BM 

0.8 

2 

HDPE 

IM/BM 

1.8 

5 

XLPE 

RM 

5.9 

Fuel Hose Length (in.) 

Fuel Hose Inner Diameter (in.) 

4 

0.125 

8 

0.25 

24 

0.25 

36 

0.25 

* HDPE = high-density polyethylene, XLPE = cross-link polyethylene 

* IM = injection-molded, BM = blow-molded, RM = rotational-molded 

The fuel tank weights are based on measurements made in our lab on many of the fuel 

tanks that were included in our evaporative emission test programs. The higher weight to 

capacity ratio of the smaller fuel tank is due to the smaller surface to volume ratio and due to 

extra structural components often molded as part of the fuel tanks. We use the fuel tank weight 

to determine costs of material changes. The method used to mold the fuel tank and material used 

affect the permeation control strategies that may be used. This effect is discussed below. 

Note that some handheld equipment has structurally-integrated constructions where the 

fuel tank is part of the structure of the equipment. These fuel tanks are typically made out of 

nylon 6 with up to 30 percent fiberglass reinforcement. Data in Chapter 5 suggest that these fuel 

tanks would be able to meet the tank permeation standards without changing the fuel tank 

material. 

6.5.1 Hose Permeation 

Barrier fuel hose incremental costs estimates are based on costs shared confidentially by 

component manufacturers. These costs are supported by the costs of existing products used in 

other nonroad and automotive applications.37,38,39 For baseline fuel lines, we consider nitrile 

rubber hose such as that used to meet SAE J30 R7 recommendations. For handheld equipment, 

we consider the baseline fuel lines to be injected-molded rubber hose for structurally-integrated 

constructions and clear elastomeric tubing for other equipment. 

For this analysis, we considered three primary approaches to reducing permeation from 

fuel hoses. The first was the use of thermoplastic fuel lines such as those used in automotive 

applications. The incremental cost of these fuel lines is about $0-0.10/ft compared to typical 

hose used on Small SI equipment. However, there have been concerns expressed in the past by 

manufacturers that this fuel line is not flexible or durable enough for small nonroad applications. 

6-65 
Final Regulatory Impact Analysis 

Two other approaches are using thermoplastic or thermoelastomer barrier materials in the 

fuel hose construction. Our estimate is that thermoplastic fuel lines, such as Teflon or THV800, 

would result in an incremental cost to the manufacturer of about $0.75-0.85 per foot. 

Manufacturers have expressed in the past that they would have to upgrade their fuel clamps for 

the use of thermoplastic barrier hose. Therefore, we include an incremental cost for the two 

clamps totaling $0.10. Manufacturers have recently shared with us that they believe the 

standards can be met through the use of a lower cost approach. In this approach, the barrier layer 

is made of a thermoelastomer such as FKM. Our estimate of the incremental cost for this 

approach is $0.20-0.30 per foot. Although the high flexibility of thermoelastomers such as FKM 

may allow manufacturers to use existing hose clamps, we also include the hose clamp cost due to 

the uncertainty of how manufacturers will construct their equipment with the new hose. 

In some handheld applications, the fuel lines are molded in intricate custom shapes rather 

than extruded like traditional hoses. In these designs, a section of the fuel line is inside the fuel 

tank while the remainder is external to the fuel tank. In addition, a vent line may be molded into 

the same part. Because the tanks are typically sealed with a one way valve on the vent, the vent 

lines are exposed to saturated vapor. The fuel lines may be formed from molded cured rubber 

such as NBR or injection-molded out of a rubberized plastic such as Alcryn. A low permeation 

approach would be to mold the fuel lines out of FKM which is a thermoelastomer used in other 

fuel line applications. Based on a sample of six fuel lines (two of which included vent lines) we 

got an average weight of 11 grams (0.025 lbs.). Based on cost estimates of $1.00/lb. for NBR 

and $10-15/lb. for FKM, we get a cost estimate of $0.25 to $0.35 per fuel line. Manufacturers 

have raised the concern that if a new material is used, that they may need to modify their hose 

connectors to make sure that the hose does not pull off the barbs. To account for this, we include 

a $0.10 cost for the addition of clamps or hose connector modifications. 

Table 6.5-2 presents the estimated incremental costs of low permeation hose for four 

typical equipment configurations. These costs include the markup discussed above for overhead 

and profit. Because these hose constructions are established technology, we consider the short 

and long-term costs to be the same. We believe the standards can be achieved using a 

thermoelastic barrier and therefore use these costs in our analysis. 

Table 6.5-2: Fuel Line Permeation Cost Estimates for Typical Small SI Equipment 

HH 

4", 1/8" ID 

WBM 

8", 1/4" ID

 NHH #1 

2 ft, 1/4" I.D. 

NHH #2 

3 ft, 1/4" I.D. 

thermoplastic barrier hose $0.54 $0.86 $2.32 $3.42 

thermoelastic barrier hose $0.28 $0.34 $0.77 $1.10 

thermoelastic molded fuel line $0.48 NA NA NA 

6.5.2 Tank Permeation 

As discussed in earlier chapters, plastic fuel tanks for Small SI equipment are constructed 

in one of three primary molding processes: blow-molding, injection-molding, and rotational 

6-66 
Costs of Control 

molding. Blow-molded tanks are primarily made of high-density polyethylene (HDPE), 

injection-molded tanks are primarily HDPE or nylon, and rotational molded tanks are primarily 

cross-link polyethylene (XLPE). Because the molding process can affect the permeation control 

approaches available, we discuss the technologies for each approach individually. 

6.5.2.1 All HDPE fuel tanks 

Surface treatments can be used to reduce permeation from HDPE fuel tanks, whether 

they are blow-molded, injection-molded, or rotational-molded. Our surface treatment cost 

estimates are based on price quotes from a companies that specialize in fluorination40 and 

sulfonation.41 In the fluorination process, costs are based on the number of fuel tanks that will fit 

into the fluorination treatment chamber. Therefore, costs are higher for larger fuel tanks, 

because less tanks will fit in the chamber. The price sheet referenced for our fluorination prices 

assumes rectangular shaped containers. These fuel tanks would stack easily in the fluorination 

treatment chamber with little wasted space. However, tor irregular shaped fuel tanks, less fuel 

tanks would fit in the treatment chamber due to dead space between the tanks when they are 

placed in the support baskets in the chamber. To account for this inefficiency with typical 

shaped fuel tanks, we consider a void space equal to about 25 percent of the volume of the fuel 

tank. For handheld equipment, we consider a void space of 100 percent because of the 

structurally-integrated nature of many tanks. 

For sulfonation, the shape of the fuel tanks is less of an issue because the treatment 

process is limited only by the spacing on the production line which is roughly the same for the 

range of fuel tank sizes used in Small SI equipment. These prices do not include the cost of 

transporting the tanks; we estimated that shipping, handling and overhead costs would be an 

additional $0.03 to $0.76 per fuel tank depending on tank size (using the same void space 

estimates as above).42 

Manufacturers, with high enough production volumes, could reduce the costs of 

sulfonating fuel tanks by constructing an in-house treatment facility. The cost of a sulfonation 

production line facility that could treat 150-500 thousand fuel tanks per year (depending on tank 

size) would be approximately $800,000.43 This facility, which is designed to last at least 10 

years, is made up of a SO3 generator, a scrubber to clean up used gas, a conveyor belt, and 

injection systems for the SO3 gas and for the neutralizing agent (ammonia solution). The 

manufacturer of this equipment estimates that the operating costs, which includes electricity and 

chemicals, would be about 3 cents per tank. We based our costs on a production capacity of 

300,000 units per year for handheld tanks and 150,000 units per year for non-handheld tanks. In 

the long term, the costs would be based on the full life of the equipment which we estimate to be 

10 years for this analysis. Finally, we use a labor rate of $28/hr with a 40 percent markup for 

overhead which is consistent with our engine costs above and apply one full time employee to 

operation of the sulfonation machine. A manufacturer that sulfonates its fuel tanks in-house 

would not need to pay shipping costs. In the long run, we calculate that this approach will be 

less expensive than shipping tanks to an outside facility. 

6-67 
Final Regulatory Impact Analysis 

6.5.2.2 Blow-molded fuel tanks 

Manufacturers may reduce permeation from blow-molded fuel tanks by blending in a low 

permeation material such as ethylene vinyl alcohol (EVOH) with the HDPE. This is typically 

known by its trade name, Selar. The EVOH in the plastic forms non-continuous barrier platelets 

in the tank during blow-molding that make it harder for fuel to permeation through the walls of 

the tank. Using this approach, no changes should be necessary in the blow-molding equipment, 

so the costs are based on increased material costs. We used 10 percent EVOH which costs about 

$3-4 per pound and 90 percent HDPE which costs about $0.65-0.75 per pound.44 This equates to 

a price increase of about $0.35 per pound. We then applied the material weights shown in 

Table 6.5-1 to estimate costs per tank for this technology. 

For higher production volumes, manufacturers may consider blow molding multi-layer 

fuel tanks with continuous barriers. Practically, a new blow-molding machine would be required 

because four or five additional injection screws would be necessary for the barrier layer, two 

adhesion layers, an additional HDPE layer, and potentially a regrind layer. A machine that could 

blow-mold multi-layer tanks would approximately double the price of the blow-molding 

machine. For this analysis, we use a mono-layer machine cost of $1,000,000 and a multi-layer 

machine cost of $3,000,00045, resulting in an increase in machine cost of $2,000,000. In 

addition, tooling costs for each new tank design would be about $50,000. For this analysis we 

considered a fuel tank with a material composition of 3 percent EVOH at $3.50/lb, 4 percent 

adhesive layer at $1/lb, 45 percent regrind, and the remainder HDPE. Our analysis uses a total 

annual production of 80,000-160,000 blow-molded tanks per year, depending on tank size 

(smaller sizes would allow more tanks per mold), with 5 different molds. Capital costs are 

amortized over 5 years in the short term and 10 years in the long-term (reflecting a 10 year life 

of the machine). 

6.5.2.3 Injection-molded fuel tanks 

The technologies discussed above for blow-molded fuel tanks do not appear to be 

feasible for injection-molded fuel tanks. The non-continuous barrier platelet approach does not 

work well in this process because of the high shear stresses associated with injection molding. 

Multi-layer rotomolded tanks would have to be formed by making separate molds, then fusing 

the layers when the tank sides are welded together. While this may be possible, it would be 

cumbersome. Barrier treatments would work for fuel tanks injected out of HDPE, but many 

handheld tanks are injection molded out of nylon for better thermal resistance. At this time, it 

appears that fluorination and sulfonation would not work effectively on nylon tanks. However, 

nylon has low permeation on gasoline, and some nylon formulations are capable of meeting the 

standards which are based on test fuel with 10 percent ethanol. 

The advantages of injection molding are that it has lower tooling costs than blowmolding and it is a faster molding process than rotational-molding. Although injection-molding 

does not lend itself well to multi-layer construction, there is another process with similar costs 

and production rates called thermoforming which does. Thermoforming entails using sheets of 

plastic that are heated and pulled into a mold using vacuum suction. As with injection molding, 

6-68 
Costs of Control 

two halves are then joined together. In thermoforming, however, the sides are combined while 

the plastic is still molten rather than by welding as is used in injection-molding. By using sheets 

of extruded multi-layer plastic, thermoforming can be used to produce low-permeation, multilayer fuel tanks. 

Because the thermoforming process requires extruded sheets, this process requires the 

addition of an extruder. A small extruder, which would support several thermoforming machines 

considered in this analysis would cost $2-3 million. The thermoforming machine itself would 

cost about two-thirds that of an injection molding machine because it has less moving parts (such 

as the injection screw). However, we estimate that two thermoforming machines would be 

necessary to maintain the cycle time possible with an injection molding machine. At the same 

time, hot plate welding machines would not be necessary because the tanks halves are assembled 

in the thermoforming machine. We use an incremental cost savings of $100,000 for the molding 

machine. Mold costs are somewhat lower for thermoforming as well because they are made of 

aluminum rather than hardened steel. We estimate that a four-cavity injection mold would cost 

about $60-80,000 while a four-cavity thermoforming mold would cost $20-30,000. For this 

analysis we use a production of 300,000 tanks per year using 5 different molds. In the short 

term, we amortize the fixed costs over 5 years, while in the long term we use 10 years to 

represent the full life of the machines. Incremental material costs are based on 3 percent EVOH 

and 4 percent adhesion material to create the barrier layer. 

Another option would be to mold the entire fuel tank of a low permeation material such 

as an acetal copolymer, or a thermoplastic polyester. These materials have list prices in the 

range of about $1- 2 per pound which is about double the material cost of HDPE, but comparable 

to the cost of nylon.46 In addition, these fuel tanks could be made out of metal, which does not 

permeate. For larger marine fuel tanks, metal tanks are available that cost about 25-30 percent 

more than plastic fuel tanks (made under low volume construction). Private conversations with 

Small SI equipment manufacturers suggest that making small fuel tanks out of metal could 

increase the cost of the tanks for Small SI equipment by 200-300 percent and would limit the 

possibility of constructing complex designs. 

6.5.2.4 Rotational-molded fuel tanks 

Many larger fuel tanks are rotationally molded. This process is more cost-effective for 

smaller production volumes than blow-molding or injection-molding because of the lower 

tooling costs for new tank designs. However, this process is slower which limits its usefulness 

for large production volumes. Typically, rotational-molded fuel tanks manufactured for Small SI 

equipment are made of cross-link polyethylene (XLPE). Although XLPE is more expensive than 

HDPE which may also be used in the rotational-molding process, it is considered to be more 

impact resistant than HDPE. This is important because the rotational molded fuel tanks are often 

larger fuel tanks mounted on the outside of the equipment where it could be exposed to impacts 

such as stepping, thrown rocks, branches, etc. 

As discussed in Chapter 5, neither sulfonation or fluorination has been demonstrated to 

be successful in creating a barrier on XLPE that would meet the new standards. Therefore, we 

6-69 
Final Regulatory Impact Analysis 

look to multi-layer approaches for our cost estimates. In the rotational-molding process, fuel 

tanks may be formed with two layers. The traditional method is to add the first material to the 

mold prior to entering the oven, and once that shell forms to add a second material through the 

use of a drop box in the mold. Depending on the complexity and size of a drop box, it can add 

from $1,000 to nearly $9,000 to the cost of the mold.47,48,49 One manufacturer is currently 

making multi-layer rotational-molded fuel tanks for use Small SI equipment without the use of a 

drop box. Their approach is proprietary, but the material manufacturer is making efforts to 

develop an alternative to using a drop box as well.50 For this analysis, we include a $5,000 cost 

for a drop box in the short term, but not in the long term. In addition, we do not project that this 

process will have an increase on the cycle processing time because the increased heating time is 

offset by decreased cooling time. The inner layer could be molded out of an acetal copolymer, 

nylon, or even HDPE which could then be surface treated. Typical acetal copolymers cost about 

the same as XLPE, although the rotational-molding grade may cost a little more.51 We use a cost 

of $1.50/lb. for this acetal copolymer compared to XLPE which is approximately $1.20/lb. 

Nylon, which can range in cost from $2 to $6 depending on the grade may also be used in 

conjunction with XLPE to provide a permeation barrier. The advantage of nylon is that it bonds 

to XLPE better than acetal copolymers. For this analysis, we consider the use of nylon at 

$4.00/lb in a fuel tank with a 1 mm barrier and 4-5mm average total wall thickness. We 

amortize the fixed cost of the drop boxes over 5 years of production of 1000 tanks per year for 

each mold. 

Another material is also available for molding an inner layer in rotomolded XLPE fuel 

tanks. This material is poly butylene terephthalate cyclic oligimor and is known by the trade 

name CBT®. With this material, no drop box is necessary. The CBT is added in the mold with 

the XLPE resin. During the molding process, the XLPE shell forms in the mold. Due to 

differences in viscosity and temperature properties, the CBT goes to the inside of the fuel tank. 

It then polymerizes to form an inner liner. We use a cost of $5/lb. for CBT in this analysis and 

use the same barrier thickness as discussed above. 

Another technology that has been demonstrated for reducing permeation from XLPE fuel 

tanks is a low permeation epoxy barrier. To apply this barrier, an adhesion treatment must first 

be performed to increase the fuel tank surface energy so that the epoxy will adhere to the XLPE. 

This can be done through a low level fluorination treatment. For this analysis, we use the cost of 

level 1 fluorination.52 We use the same void space and shipping costs discussed above for our 

fluorination cost analysis. The epoxy could be applied by dipping the fuel tank or spraying it on 

like paint and then must be cured using UV light. We include a fixed cost of $10,000 for a 

volume of 100,000 fuel tanks per year to account for coating and curing equipment. In addition, 

we apply the cost of one full time employee to apply the coating and use a labor rate of $28/hr 

with a 40 percent markup for overhead which is consistent with our engine costs above. For 

traditional epoxies, we estimate that the cost would be $6-7/lb. Manufacturers have commented 

that UV-curable epoxy, which could be processed much faster, would cost $12-15/lb.53,54 We 

use a cost of $12/lb. for this analysis. Because only a thin coating needed (we use 0.125 mm), 

the epoxy layer makes up only about 3 percent of the material of the fuel tank. Because there are 

benefits to the epoxy coating such as allowing the fuel tank to be painted, there may be an 

incentive to use this technology even on HDPE fuel tanks. For that reason, we estimated the cost 

6-70 
Costs of Control 

for smaller HDPE tanks as well using the same general assumptions except for a larger 

production volume of 150,000 tanks per year due to their smaller size. 

6.5.2.5 Summary of Fuel Tank Costs per Equipment 

Table 6.5-3 summarizes the incremental costs of the fuel tank permeation emissioncontrol strategies discussed above. For technologies sold by a supplier to the engine 

manufacturers, an additional 29 percent markup is included for the supplier's overhead and 

profit. Both long-term and short-term costs are presented. The long-term costs account for the 

stabilization of the capital investments and the learning curve effect discussed above. We use 

the same material and shipping costs for our short-term and long-term estimates because these 

cost components are well established with a wide range of applications. As discussed above, for 

the multilayer fuel tank constructions, we consider an EVOH barrier for hand-held and Class I 

equipment and nylon barrier for Class II equipment. 

Table 6.5-3: Tank Permeation Control Cost Estimates for Typical Small SI Equipment 

HH 

0.25 gallons 

IM/BM 

WBM 

0.5 gallons 

IM/BM 

NHH #1 

2 gallons 

IM/BM 

NHH #2 

5 gallons 

RM 

fluorinationa,b: short term

 long term 

$0.62 

$0.50 

$0.77 

$0.63 

$3.10 

$2.52 

NA 

sulfonationa,b: short term

 long term 

$0.64 

$0.52 

$1.25 

$1.01 

$1.40 

$1.16 

NA 

non-continuous plateletsa $0.17 $0.22 $0.51 NA 

multi-layera

: short term 

EVOH long term 

$4.13 

$2.01 

$4.08 

$1.98 

$3.80 

$1.75 

NA 

multi-layerc

: short term 

PA11 long term 

NA NA NA $5.54 

$3.40 

multi-layerc

: CBT NA NA NA $5.77 

thermo-formingb

: short term

 long term 

$0.36 

$0.20 

$0.53 

$0.29 

$1.50 

$0.82 

NA 

acetal-copolymera,b,c $0.62 $0.79 $1.82 $2.28 

metal constructiona,b,c $1.94 $3.87 $5.16 $9.68 

epoxy coatinga,b,c: short term

 long term 

$1.26 

$1.01 

$1.32 

$1.06 

$2.56 

$2.08 

$5.69 

$4.64 a

 incremental to traditional blow-molding 

b

 incremental to traditional injection-molding 

c

 incremental to traditional rotational-molding 

6-71 
Final Regulatory Impact Analysis 

6.5.3 Venting Losses 

Venting losses are made up of diurnal breathing losses and running losses which are 

similar to diurnal emissions except that the heating event is caused by the engine. We are 

requiring that equipment manufacturers install systems to capture their running losses by sealing 

the fuel tank and venting vapor to the engine intake. For the purpose of our cost analysis, we 

consider a system with a purge hose running from the fuel tank to the engine intake (with 2 hose 

clamps) that is the same length of the fuel hose. We use a cost of $0.25/ft for the hose and $0.10 

each for the two hose clamps. This is consistent with the above cost analysis for low permeation 

hose. We also consider a fuel cap redesign to meet the sealing requirements with a one way 

valve to prevent a vacuum from occurring in the fuel tank as fuel is drawn out to the engine. We 

use a cost of $1 for the valve and cap redesign. Also, we include a cost of $0.10 to account for a 

limiting flow orifice in the purge line. Finally, using the labor costs discussed above, we 

calculate an incremental assembly labor cost of about $0.20 per engine. 

Diurnal emissions could be captured through the use of a carbon canister. The carbon 

then could be purged by air drawn into the fuel tank as the fuel cools. This is known as passive 

purge. This system would be similar to the running loss control system except that venting 

would occur through a canister and the valving would be modified to provide liquid/vapor 

separation. This valve would prevent fuel from entering the canister if the equipment were 

tipped over. We estimate the cost of a canister to vary based on size ranging from about $2 for a 

1 quart tank to about $4 for a five gallon tank. The majority of these canister costs for small fuel 

tanks are for the canister, connections, and mounting hardware. As the fuel tank size increases, 

the carbon becomes a more significant fraction of the cost. For this analysis, we add the cost of 

the canister to the cost of running loss control and include another $0.20 for assembly costs. 

Diurnal emissions could be controlled further through an active purge canister system. In 

an active purge system, the canister would also be purged by the engine during operation. The 

added components of this system compared to the passive purge system would include a line to 

the air filter (or separate air filter for the canister breathing line) and a purge valve. This 

amounts to an additional cost of $0.15/ft for the air line, $0.20 for two clamps, $1 for the purge 

valve, and another $0.20 for assembly. 

6-72 
Costs of Control 

Table 6.5-4: Venting Control Cost Estimates for Typical Small SI Equipment 

WBM 

0.5 gallons 

8", 1/4" ID 

NHH #1 

2 gallons 

2 ft, 1/4" ID 

NHH #1 

5 gallons 

3 ft, 1/4" I.D. 

running loss: short term

long term 

$2.06 

$1.65 

$2.32 

$1.85 

$2.51 

$2.01 

passive purge canister*: short term 

long term 

$3.07 

$2.45 

$3.82 

$3.06 

$4.38 

$3.51 

active purge canister**: short term

long term 

$1.93 

$1.54 

$2.19 

$1.75 

$2.38 

$1.91 

* incremental to running loss control 

** incremental to passive purge canister 

6.5.4 Certification and Compliance 

The running loss standards call for manufacturers to certify their running loss systems 

based on design rather than requiring emission testing. However, they will still need to integrate 

the emission-control technology into their designs and there will be some engineering and 

clerical effort need to submit the required information for certification. We expect that in the 

early years, plastic fuel tank manufacturers will perform durability and permeation testing on 

their fuel tanks for certification. They will be able to carry over this data in future years and will 

be able to carry across this data to other fuel tanks made of similar materials and using the same 

permeation control strategy regardless of tank size or shape. Typical certification costs may be 

spread between the tank manufacturer, hose manufacturer, and equipment manufacturer. For the 

sake of this analysis, we combine the tank, hose, and boat certification costs to calculate the total 

certification of an average fuel system. We estimate that 90 percent of fuel tank sales in Small 

SI equipment are plastic and the remainder are metal. 

For the first year we estimate fuel tank durability and certification testing to cost about 

$15,000 per tank manufacturer on the assumption that the manufacturer will use the same 

materials and permeation control strategy for all of their fuel tanks to reduce costs. Low 

permeation fuel lines are largely an established technology. However, we include a cost of 

$1,000 to perform certification testing on fuel lines. In addition, we estimate about $10,000 for 

engineering and clerical work for the equipment manufacturers. 

For handheld equipment manufacturers, we spread these costs over sales of 500,000 units 

per year. For handheld and Class I equipment manufacturers, which are integrated 

manufacturers, we base the costs on average annual sales per manufacturer. We estimate the 

average annual sales to be about 500,000 units for handheld equipment and 100,000 units for 

Class I equipment. Generally for Class II equipment, a large number equipment manufacturers 

purchase their engines from a smaller number of engine manufacturers. We estimate average 

annual sales per year to be 50,000 units for Class II. 

6-73 
Final Regulatory Impact Analysis 

As with other fixed costs, we amortized the cost over 5 years of sales to calculate per unit 

certification costs. Combining these costs, we get average fuel system integration and 

compliance costs of about $0.01 for handheld equipment, $0.05 for Class I equipment, and $0.10 

for Class II equipment. 

6.5.5 Operating Cost Savings 

Evaporative emissions are essentially fuel that is lost to the atmosphere. Over the 

lifetime of a piece of Small SI equipment, this can result in a significant loss of fuel. The 

reduction in evaporative emissions would therefore result in meaningful fuel savings which can 

be directly related to operating cost savings based on an average density of 6 lbs/gallon for 

gasoline (based on lighter hydrocarbons which evaporate first) and the price of gasoline 

described above. Table 6.5-5 presents the estimated fuel savings for Small SI equipment 

associated with the evaporative emission standards. 

Table 6.5-5: Projected Evaporative Fuel Savings for Small SI Equipment 

Handheld Class I Class II 

Evaporative HC Reduced [lbs/life] 1.4 4.8 28.6 

Lifetime Gallons Saved 0.2 0.8 4.7 

Lifetime Cost Savings $0.41 $1.45 $8.55 

Average Equipment Life [years] 4.2 5.3 5.9 

Discounted Cost Savings (7%) $0.40 $1.31 $5.96 

6.5.6 Total Small SI Equipment Costs 

We expect that Small SI manufacturers will use a variety of technologies to meet the fuel 

tank permeation standards. As discussed above, many options are available so the technologies 

chosen will depend on the baseline fuel tank construction, the equipment application, and the 

manufacturers’ particular design philosophies. Hose permeation standards will likely be met 

through the use of barrier hose constructions. 

For the purpose of this analysis, we divided Small SI equipment into 23 categories to 

better quantify differences in costs that may be associated with different equipment applications. 

Earlier in this chapter, engine costs are presented as a function of design life. However, we 

believe evaporative emission costs are more a function of the application than the design life due 

to the differences in hose lengths and tank sizes and constructions. Manufacturers would not 

likely design a less robust fuel system for equipment used with lower hour engines. Table 6.5-6 

presents our assessment of the mix of the fuel system constructions used today. This assessment 

is based on the NONROAD 2005 model and on confidential information supplied by Small SI 

equipment manufacturers. 

6-74 
Costs of Control 

Table 6.5-6: Baseline Technology Mix for Small SI Equipment 

Equipment Class 

Fuel Line Description Fuel Tank Construction 

Length ft* construction gallons material/process** 

Handheld Equipment 

Class III commercial 

Class III residential 

Class IV commercial 

Class IV residential 

Class V 

0.25 

0.25 

0.33 

0.33 

0.50 

rubber hose 

rubber hose 

6% molded line 

24% molded line 

52% molded line 

0.9 

0.3 

0.4 

0.3 

0.5 

HDPE 

HDPE 

6% Nylon/94% HDPE 

24% Nylon/76% HDPE 

52% Nylon/48% HDPE 

Class I Equipment 

ag/const/gen ind/mat hand 

commercial mowers 

residential mowers 

com. other L&G 

res. other L&G 

pumps/comp/press. wash 

snow equipment 

utility/rec. vehicles 

welders/generators 

0.72 

0.72 

0.62 

0.72 

0.62 

0.72 

0.63 

0.72 

0.72 

rubber hose 

rubber hose 

rubber hose 

rubber hose 

rubber hose 

rubber hose 

rubber hose 

rubber hose 

rubber hose 

1.6 

0.8 

0.4 

1.1 

0.6 

0.8 

0.3 

3.6 

0.8 

100% IM 

90% IM/10% BM 

100% IM 

90% IM/10% BM 

100% IM 

100% IM 

100% IM 

100% IM 

100% IM 

Class II Equipment 

ag/const/gen ind/mat hand 

commercial mowers 

residential mowers 

com. other L&G 

res. other L&G 

pumps/comp/press. wash 

snow equipment 

utility/rec. vehicles 

welders/generators 

3.6 

6.5 

3.2 

1.5 

1.1 

2.6 

1.2 

2.7 

3.8 

rubber hose 

rubber hose 

rubber hose 

rubber hose 

rubber hose 

rubber hose 

rubber hose 

rubber hose 

rubber hose 

5.4 

4.7 

2.6 

1.2 

5.0 

4.7 

0.7 

3.9 

6.0 

60% IM/40% RM 

60% IM/40% RM 

70/18/12% IM/BM/RM 

60% IM/40% RM 

70/18/12% IM/BM/RM 

60% IM/40% RM 

60% IM/40% RM 

60% IM/40% RM 

60% IM/40% RM 

* we use 1/8" I.D. for handheld and 1/4" I.D. for non-handheld hose 

** IM = injection molded HDPE, BM = blow-molded HDPE, RM = rotational-molded XLPE 

We base our fuel tank costs on several technologies. In our cost analysis for handheld 

engines, we model costs based on fluorination for HDPE tanks, but we do not apply costs to 

tanks that are molded out of nylon as these tanks would likely meet the standards today. For 

non-handheld equipment, we split the costs of permeation control of injected molded HDPE fuel 

tanks 50/50 between fluorination and converting to multi-layer thermoformed constructions with 

an EVOH barrier. For blow-molded fuel tanks, we base our costs on using a multi-layer 

blowmolded construction with an EVOH barrier. For rotational-molded XLPE fuel tanks, we 

base our costs on rotational-molding a nylon layer in the tank. 

6-75 
Final Regulatory Impact Analysis 

For fuel line permeation, we distinguish between the costs for traditional hose versus 

molded fuel lines. Fuel hose costs are based on using a fluoroelastomer barrier within the 

traditional construction. For molded fuel lines, we base the costs on molding the parts 

completely out of a high-grade fluoroelastomer. We do not apply costs to fuel lines used in coldweather equipment. 

As discussed above, our cost estimates include both variable and fixed costs, and we 

distinguish between near-term and long-term costs. Because our analysis amortizes fixed costs 

over 5 years, the long-term costs are generally made up of variable costs only. The exception to 

this is fuel tank permeation control strategies where more expensive molding equipment is used. 

We assume an equipment life of 10 years, so in the long term, the amortized additional cost of 

the molding equipment is half, on average, of the short-term amortized cost over 5 years (5 years 

of amortized payments/10 years of equipment life = 1⁄2). In addition, variable costs are lower in 

the long term due to the learning effect discussed in Section 6.1. Table 6.5-7 presents these 

average per-engine cost estimates. 

Table 6.5-7: Small SI per Equipment Cost Estimates (Without Fuel Savings) 

Short Term (years 1-5) Long Term (years 6-10) 

Fixed Variable Total Fixed Variable Total 

Handheld aggregate

 tank permeation

 hose permeation 

$0.01 

$0.01 

$0 

$0.81 

$0.62 

$0.19

 $0.82

 $0.63 

$0.19 

$0 

$0 

$0

 $0.69

 $0.50 

$0.19 

$0.69

 $0.50 

$0.19 

Class I aggregate

 tank permeation

 hose permeation

 running loss 

$0.47 

$0.45 

$0.02 

$0

 $2.58

 $0.33 

$0.33 

$1.92 

$3.05

 $0.78 

$0.35 

$1.92 

$0.19 

$0.19 

$0 

$0

 $2.01

 $0.27 

$0.20 

$1.53 

$2.20

 $0.46 

$0.20 

$1.53 

Class II aggregate

 tank permeation

 hose permeation

 running loss 

$1.26 

$1.21 

$0.04 

$0

 $5.47

 $2.15 

$1.09 

$2.23 

$6.73

 $3.37 

$1.13 

$2.23 

$0.69 

$0.69 

$0 

$0

 $4.48

 $1.73 

$0.96 

$1.78 

$5.16

 $2.42 

$0.96 

$1.78 

6.5.7 Small SI Equipment Aggregate Costs 

Aggregate costs are calculated by multiplying the per-equipment variable cost estimates 

described above by projected equipment sales. Fixed costs are added as incurred. Fuel savings 

are calculated directly from the projected HC reductions due to the evaporative emission 

standards. Table 6.5-8 presents the projected costs of the rule over a 30-year time period with 

and without the fuel savings associated with reducing evaporative emissions. 

At a 7 percent discount rate, over 30 years, the estimated annualized cost to 

manufacturers for Small SI evaporative emission control is $65 million. The estimated 

corresponding annualized fuel savings due to control of evaporative emissions from Small SI 

6-76 
Costs of Control 

equipment is $53 million. At a 3 percent discount rate, the estimated annualized cost to 

manufacturers for Small SI evaporative emission control is $68 million. The estimated 

corresponding annualized fuel savings due to control of evaporative emissions from Small SI 

equipment is $59 million. 

Table 6.5-8: Projected 30-Year Aggregate Cost Stream for Small SI Evap 

Year 

Without Fuel Savings With Fuel Savings 

Handheld Class I Class II Handheld Class I Class II 

2008 

2009 

2010 

2011 

2012 

2013 

2014 

2015 

2016 

2017 

2018 

2019 

2020 

2021 

2022 

2023 

2024 

2025 

2026 

2027 

2028 

2029 

2030 

2031 

2032 

2033 

2034 

2035 

2036 

2037

 $224,312 

$5,942,463 

$5,816,345 

$5,923,313 

$7,752,522 

$7,883,770 

$6,810,314 

$6,922,632 

$7,034,855 

$7,147,090 

$7,259,067 

$7,371,143 

$7,483,470 

$7,595,660 

$7,707,763 

$7,819,853 

$7,931,999 

$8,044,212 

$8,156,448 

$8,268,656 

$8,380,840 

$8,493,060 

$8,605,303 

$8,717,528 

$8,829,741 

$8,941,949 

$9,054,168 

$9,166,396 

$9,278,617 

$9,390,834 

$4,648,719 

$4,732,285 

$9,215,094 

$9,277,641 

$30,008,965 

$29,122,813 

$29,609,400 

$30,093,095 

$30,569,878 

$25,830,285 

$26,235,145 

$26,644,831 

$27,051,954 

$27,457,582 

$27,860,231 

$28,266,579 

$28,672,351 

$29,079,725 

$29,490,381 

$29,900,304 

$30,309,200 

$30,719,307 

$31,129,464 

$31,540,051 

$31,950,436 

$32,360,405 

$32,770,086 

$33,180,125 

$33,590,247 

$34,000,550 

$7,105,928 

$13,749,794 

$12,455,089 

$35,396,135 

$36,003,944 

$35,892,762 

$36,495,479 

$37,094,450 

$32,298,515 

$32,819,027 

$33,338,022 

$33,862,125 

$34,382,368 

$34,902,482 

$35,418,720 

$35,938,441 

$36,458,489 

$36,981,966 

$37,505,944 

$38,028,453 

$38,550,330 

$39,073,626 

$39,597,054 

$40,121,181 

$40,644,586 

$41,167,490 

$41,690,229 

$42,213,436 

$42,736,659 

$43,260,062 

$224,312 

$5,707,932 

$5,135,637 

$4,845,509 

$6,079,623 

$5,677,010 

$4,191,701 

$4,019,074 

$3,902,020 

$3,897,310 

$3,924,431 

$3,968,150 

$4,021,523 

$4,080,576 

$4,139,728 

$4,198,990 

$4,258,379 

$4,317,834 

$4,377,298 

$4,436,735 

$4,496,146 

$4,555,595 

$4,615,066 

$4,674,519 

$4,733,961 

$4,793,398 

$4,852,844 

$4,912,301 

$4,971,750 

$5,031,196 

$3,697,028 

$2,634,260 

$6,081,748 

$5,276,627 

$21,187,318 

$16,186,469 

$13,744,050 

$12,389,454 

$11,344,204 

$5,337,945 

$4,963,819 

$4,768,572 

$4,660,933 

$4,604,761 

$4,586,374 

$4,607,753 

$4,648,613 

$4,691,017 

$4,733,531 

$4,775,266 

$4,815,980 

$4,857,899 

$4,899,855 

$4,942,267 

$4,984,464 

$5,026,247 

$5,067,730 

$5,109,583 

$5,151,512 

$5,193,635 

$4,886,033 

$8,715,782 

$4,833,539 

$20,401,655 

$14,937,731 

$9,525,916 

$6,260,075 

$3,382,349 

$(4,288,346)

 $(5,765,846)

 $(6,881,442)

 $(7,709,855)

 $(8,357,363)

 $(8,820,939)

 $(9,198,114)

 $(9,511,148)

 $(9,799,648)

 $(10,064,140)

 $(10,315,949)

 $(10,558,303)

 $(10,793,367)

 $(11,021,049)

 $(11,243,155)

 $(11,460,730)

 $(11,676,805)

 $(11,890,232)

 $(12,101,049)

 $(12,309,918)

 $(12,516,613)

 $(12,721,142) 

6.6 Costs of Evaporative Emission Controls for Marine Vessels 

This section presents our cost estimates for meeting the new evaporative emission 

standards for marine vessels. 

To determine the cost impacts of the evaporative emission standards on marine fuel 

systems, we considered three primary marine applications. The first is a portable fuel tank with 

a detachable fuel line and a primer bulb. The second is a personal watercraft vessel. The third is 

6-77 
Final Regulatory Impact Analysis 

a larger vessel with an installed fuel tank and fuel lines meeting SAE J1527 specifications. In 

our cost analysis, we consider a wide range of vessel sizes for each of these categories. 

However, to simplify this discussion we only present our cost estimates for the three typical 

applications shown in Table 6.6-1. For this illustration, costs are based on vessels with one fuel 

tank and one engine. Although these typical configurations do not, by any means, represent all 

of the vessel types included in our cost calculations, they should give a good indication of how 

we performed our analysis. 

Table 6.6-1: Typical Marine Vessel Fuel System Configurations 

Portable Tank PWC Installed Tank 

Fuel Tank Capacity (gallons) 

Fuel Tank Material* 

Fuel Tank Molding Process 

Fuel Tank Weight (lbs.) 

6 

HDPE 

blow-molded 

4.4 

17 

HDPE 

blow-molded 

12 

57 

XLPE 

rotational-molded 

55 

Fuel Hose: Length (ft.)

 Inner Diameter (in.) 

Vent Hose: Length (ft.)

 Inner Diameter (in.) 

Fill Neck: Length (ft.)

 Inner Diameter (in.) 

6, primer bulb 

1/4 

– 

– 

– 

– 

5.7 

1/4 

2 

1/4 

1.9 

1.5 

9.9 

3/8 

8.0 

5/8 

10.1 

1.5 

* HDPE = high-density polyethylene, XLPE = cross-link polyethylene 

Fuel tank weights are based on measurements of fuel tanks used in our permeation testing 

and are used to determine material costs. XLPE fuel tanks are typically thicker walled; thus they 

typically weigh more per gallon of capacity. Fuel hose lengths are based on conversations with 

(and confidential business information from) boat builders and fuel system suppliers. This data 

is within the range of hose lengths included in the written comments made by one boat builder 

on our earlier proposal.55 

6.6.1 Hose Permeation 

There are several grades of fuel system hose used in marine applications. For sterndrive 

and inboard (SD/I) applications, Title 33 of the Code of Federal Regulations, Part 183 defines 

fuel system requirements. These requirements reference SAE J1527 for fuel hose specifications. 

For personal watercraft (PWC), fuel line specifications are defined in SAE J2046. For 

outboards, no fuel hose specifications exist. Typically, larger vessels, with installed fuel tanks 

use SAE J1527 Class I hose for lines filled with fuel and Class II hose for lines containing fuel 

vapor. Inner diameters (ID) of these fuel system lines are typically 3/8" for fuel lines, 5/8" for 

vent lines, and 1.5" for fill necks. PWC typically have fuel supply/return hose with a 1/4" ID. 

Portable marine fuel tanks for outboards typically have fuel lines with a 1/4" ID and a primer 

bulb. Fill neck hose is made by wrapping several layers of materials over a mandrill and 

vulcanizing the rubber in an oven. The remaining fuel lines are typically extruded. Fuel hose 

meeting the CFR requirements typically has several layers for durability and flame resistance. 

6-78 
Costs of Control 

Barrier fuel hose incremental costs estimates are based on costs of existing products used 

in marine and automotive applications.56,57,58,59,60 Because the manufacturing process is not 

fundamentally changed in adding a barrier layer, this cost is mostly the result of more expensive 

materials. For 1/4" hose such as used in some small outboards and personal watercraft, we 

estimate a cost increase of $0.25/ft for a thermoelastic barrier and $0.85/ft for a thermoplastic 

barrier. These costs are consistent with the costs described above for Small SI equipment. 

SD/I vessels are required to use marine fuel hose meeting Coast Guard requirements 

specified in 33 CFR part 183. This hose is recommended by the American Boat and Yacht 

Council for outboard boats not using portable fuel tanks as well. Marine hose with a nylon 

barrier is available today that meets these requirements. The cost differential of traditional 

versus marine barrier hose for fuel and vent lines in the market today varies from no cost at all to 

more than $1 per foot. One hose distributer stated that they sell both non-barrier and barrier hose 

at the same price. They stated that the fuel resistance provided by the barrier layer allows the 

hose construction to use a thinner wall and therefore use less rubber. Another hose distributor, 

lists about a $1 cost markup for A1 barrier hose compared to their B1 marine hose. Note that B1 

hose does not meet the Coast Guard fire requirements for fuel lines and this may be part of the 

reason for the cost differential. For this analysis, we use a cost increase of $0.50/ft for fuel hose 

and $1.00 for vent hose for vessels with installed fuel tanks. We use a higher incremental cost 

for vent hose because this hose typically has a larger diameter, requiring more material. 

For 11⁄2" fill neck hose, we estimate a cost increase of $2.00/ft. This cost increase is 

based on our estimates of material and labor costs. The fill neck hose would be constructed in 

the same manner as today except that a thin barrier layer would be included in the multi-layer 

construction. One hose distributer advertises barrier fill-neck hose with a price markup of $9 per 

foot. However, this cost markup likely represents the high costs typical of special orders where 

setup costs must be spread over low hose production. Currently, little or none of this hose is 

purchased by boat builders. Our price estimate is more consistent with differences in cost for 

barrier versus non-barrier chemical hose manufactured in the same manner. 

We do not expect the addition of a barrier layer to affect the flexibility of the hose 

because marine hose is already fairly stiff and because the barrier layer is very thin and flexible. 

In fact, the barrier hose samples we tested appeared a little more flexible than the baseline hose 

because less wall thickness was needed for permeation control. Therefore, we believe special 

hose clamps or fittings will not typically be required. 

Primer bulbs are typically formed from molded cured rubber such as NBR or injectionmolded out of a rubberized plastic such as Alcryn. Primer bulbs could also be molded from 

FKM which is a fluoroelastomer used in fuel line applications. Primer bulbs typically weigh 

between 0.1 and 0.2 lbs, nitrile costs about $1.00/lb and FKM costs about $10-15/lb depending 

on the level of fluorine in the material. If the whole primer bulb was molded out of FKM, it 

would increase the material cost by about $1.50-2.00 per primer bulb. Alternatively, 

manufacturers could save on material costs by injection molding an inner layer of Alcryn and 

curing a coating of FKM over this shell. Using a higher grade of FKM ($15/lb) could help 

minimize the amount of the fluoroelastomer needed. For the multi-layer design, we assume 

6-79 
Final Regulatory Impact Analysis 

about 30-50 percent of the material would be FKM which results in a material cost increase of 

about $0.90 per primer bulb. 

Table 6.6-2 presents our estimates of incremental costs for low permeation marine fuel 

system hose. Primer bulb costs are presented both for 100 percent FKM and multi-layer 

constructions. The incremental cost for the 1/4" fuel lines are presented for the thermoelastic 

barrier and the costs for the heavier fuel hose are based on costs of existing nylon barrier marine 

hose. These costs include a markup, and no long-term cost savings are applied to these costs 

because they are primarily material costs. 

Table 6.6-2: Hose Permeation Control Cost Estimates for Typical Marine Vessels 

Portable Tank 

6', 1/4" ID fuel hose 

primer bulb 

PWC 

5.7', 1/4" ID fuel hose 

1.9', 1.5" ID fill neck 

2.0', 1/4" ID vent hose 

Installed Tank 

9.9', 3/8" ID fuel hose 

10.1', 1.5" ID fill neck 

8.0', 5/8" ID vent hose 

primer bulb

 100% FKM

 multi-layer 

fuel supply/return 

fill neck 

vent hose 

$2.13 

$1.16 

$1.94 

– 

– 

– 

– 

$1.84 

$5.16 

$0.65 

– 

– 

$6.58 

$26.12 

$10.29 

6.6.2 Tank Permeation 

Portable fuel tanks and fuel tanks used in personal watercraft are typically blow-molded 

out of HDPE and have a capacity ranging from 4 to18 gallons. Because of the manufacturing 

process and material used, some permeation control technologies are available that are different 

from what would be feasible for larger rotational-molded fuel tanks. Larger, low-production 

volume marine fuel tanks are typically rotational-molded out of XLPE. Rotational-molding is 

used for smaller production runs because of the much lower relative tooling costs compared to 

blow-molding. For fuel tanks in vessels that are subject to the 33 CFR 183 fuel system 

requirements, manufacturers have found that fuel tanks molded out of HDPE will not pass the 

fire test, while XLPE fuel tanks will. Therefore, XLPE is used in rotational-molded marine fuel 

tanks. 

6.6.2.1 Blow-Molded Fuel Tanks 

Our surface treatment cost estimates are based on price quotes from companies that 

specialize in this fluorination61 and sulfonation.62 The fluorination costs are a function of the 

geometry of the fuel tanks because they are based on how many fuel tanks can be fit in a 

treatment chamber. The price sheet referenced for fluorination assumes rectangular shaped 

containers. For irregular shaped fuel tanks, the costs would be higher because they could not 

efficiently utilize the chamber volume. There would be significant void space. We consider a 

6-80 
Costs of Control 

void space equal to about 25 percent of the volume of the fuel tank. For sulfonation, the shape of 

the fuel tanks is less of an issue because the treatment process is limited only by the spacing on 

the production line which is roughly the same for the range of fuel tank sizes used for 

portable and personal watercraft fuel tanks. These prices do not include the cost of transporting 

the tanks; we estimated that shipping, handling and overhead costs would be an additional $0.40-

$1.40 per fuel tank, for tanks ranging from 4-18 gallons.63 

As discussed above for Small SI fuel tanks, manufacturers, with high enough production 

volumes, could reduce the costs of sulfonating fuel tanks by constructing an in-house treatment 

facility. We base our costs for marine fuel tanks on 150,000 tanks per year and use this approach 

for our long-term cost determination for sulfonation. 

Our estimate of the cost for non-continuous barrier platelets (generally known as Selar) is 

based on increased material costs. No changes should be necessary to the blow-molding 

equipment. We used 10 percent ethylene vinyl alcohol (EVOH) which is about $3-4 per pound 

and 90 percent HDPE which is about $0.65-0.75 per pound.64 This equates to a price increase of 

about $0.35 per pound. We then applied the material weights shown in Table 6.5-1 to estimate 

costs per tank for this technology. 

For higher production volumes, manufacturers may consider blow molding multi-layer 

fuel tanks with continuous barriers. Practically, a new blow-molding machine would be required 

because four or five additional injection screws would be necessary for the barrier layer, two 

adhesion layers, an additional HDPE layer, and potentially a regrind layer. A machine that could 

blow-mold multi-layer tanks would approximately double the price of the blow-molding 

machine For this analysis, we use a mono-layer machine cost of $1,000,000 and a multi-layer 

machine cost of $3,000,000 for smaller tanks and $4,000,000 for larger tanks (>6 gallons)65, 

resulting in an increase in machine cost of $2,000,000-$3,000,000. In addition, tooling costs for 

each new tank design would be about $50,000. For this analysis we considered a fuel tank with 

a material composition of 3 percent EVOH at $3.50/lb, 4 percent adhesive layer at $1/lb, 45 

percent regrind, and the remainder HDPE. Our analysis uses a total annual production of 

60,000-80,000 blow-molded tanks per year, depending on tank size, with 5 different molds. 

Capital costs are amortized over 5 years in the short term and 10 years in the long-term 

(reflecting a 10 year life of the machine). 

6.6.2.2 Rotational-Molded Fuel Tanks 

Most installed fuel tanks are rotational-molded out of XLPE for the reasons discussed 

above. As discussed above, barrier treatments have not been demonstrated to provide effective 

permeation control for XLPE. In addition, Selar and traditional multi-layer blow-molding 

approaches do not work for rotational-molded cross-link polyethylene fuel tanks. 

Two approaches were discussed above in the Small SI section for rotational-molded 

XLPE fuel tanks: 1) dual-layer molding with a barrier layer and 2) epoxy coating of fuel tanks. 

These approaches could also be applied to marine fuel tanks. For the dual layer approach, 

marine fuel tank manufacturers have expressed concern that the acetal copolymer will not adhere 

6-81 
Final Regulatory Impact Analysis 

well to the XLPE. For large fuel tanks, this could be an issue because the layers could pull apart 

and cause leaks at the fittings. As an alternative, one company has developed an approach using 

a high grade, non-hygroscopic nylon known a polyamide 11 as a barrier layer. This material 

costs about $5-7/lb compared to XLPE which costs about $1.20/lb. The barrier layer would 

likely be about 20 percent of the total material. Using a nylon cost of $6/lb. and a barrier fraction 

of 30 percent, we get an average material cost of $2.64/lb. For the short term, we add a $5,000 

cost to the mold or a drop box which we amortize over 100 tanks per year for 5 years. 

Consistent with the analysis for Small SI equipment, we do not include the cost of a drop box in 

the long term because of the ongoing development of a process that does not require a drop 

box.66 In fact, one manufacture is already using a proprietary process to mold multi-layer 

rotational-molded fuel tanks without a drop box. 

Another material is also available for molding an inner layer in rotomolded XLPE fuel 

tanks. This material is poly butylene terephthalate cyclic oligimor and is known by the trade 

name CBT®. With this material, no drop box is necessary. The CBT is added in the mold with 

the XLPE resin. During the molding process, the XLPE shell forms in the mold. Due to 

differences in viscosity and temperature properties, the CBT goes to the inside of the fuel tank. 

It then polymerizes to form an inner liner. We use a cost of $5/lb. for CBT in this analysis and 

use the same barrier thickness as discussed above. 

Another technology that has been demonstrated for reducing permeation from XLPE fuel 

tanks is a low permeation epoxy barrier. To apply this barrier, an adhesion treatment must first 

be performed to increase the fuel tank surface energy so that the epoxy will adhere to the XLPE. 

This can be done through a low level fluorination treatment. For this analysis we use the cost of 

level 1 fluorination.67 We use the same void space and shipping costs discussed above for our 

fluorination cost analysis. Shipping costs are estimated to range from $4-$10 per tank for 

20-130 gallon tanks. The epoxy could be applied by dipping the fuel tank or spraying it on like 

paint and then the epoxy must be allowed to cure. We include a fixed cost of $10,000 for a 

volume of 15,000 fuel tanks per year to account for coating and curing equipment. In addition, 

we apply the cost of part of one employee’s time (using a labor standard of 15,000 tanks 

annually per employee) time to apply the coating and use a labor rate of $28/hr with a 40 percent 

markup for overhead which is consistent with our engine costs above. We estimate that the 

epoxy cost would be $6-7/lb. Manufacturers have commented that UV-curable epoxy, which 

could be processed much faster, would cost $12-15/lb.68,69 We use a cost of $12/lb. for this 

analysis. However with only a thin coating needed (we use 0.125 mm), the epoxy layer makes 

up only about 2.0-2.5 percent of the material of the fuel tank. Because there are benefits to the 

epoxy coating such as allowing the fuel tank to be painted, there may be an incentive to use this 

technology even on HDPE fuel tanks. For that reason, we estimated the cost for portable fuel 

tanks as well using the same general assumptions except for a larger production volume of 

100,000 tanks per year with a increased labor standard due to the smaller tank sizes. 

6.6.2.3 Other Marine Fuel Tank Constructions 

We do not anticipate that the permeation standard would affect the cost of metal fuel 

tanks. Although some permeation can occur at rubber seals (such as for the sending unit), this 

6-82 
Costs of Control 

would be small due to the small exposed surface area of the seals. 

Another type of fuel tank construction that is used in some applications, such as offshore 

racing boats, is fiberglass fuel tanks. This fiberglass is commonly made of vinyl ester or epoxy 

which have high permeation rates. One manufacturer has developed a fiberglass composite that 

uses treated volcanic ash in a carrier matrix to create a non-continuous permeation barrier. This 

composite is known as an unsaturated polyester nanocomposite (UPE). In addition to being a 

low permeation technology for fiberglass tanks, this construction could also be used as an 

alternative for metal or plastic fuel tanks. These low permeation fiberglass constructions can be 

fabricated or molded. We estimate that fabricated fiberglass composite fuel tanks would cost at 

least as much as metal fuel tanks because of the labor involved in hand constructing the tanks. 

However, these fuel tanks may also be molded with an average mold cost of $2,500.70 For the 

purposes of this analysis we use a cost increase of 20 percent when comparing this technology to 

rotational-molded fuel tanks which is a somewhat lower than the cost of a metal fuel tank. 

6.6.2.4 Summary of Fuel Tank Costs per Vessel 

Table 6.6-3 summarizes the incremental costs of the fuel tank permeation emissioncontrol strategies discussed above. For technologies sold by a supplier to the engine 

manufacturers, an additional 29 percent markup is included for the supplier's overhead and 

profit. Both long-term and short-term costs are presented. The long-term costs account for the 

stabilization of the capital investments and the learning curve effect discussed above. We use 

the same material, shipping, and fluorination costs for our short-term and long-term estimates 

because these cost components are well established with a wide range of applications. As 

discussed above, for the multilayer fuel tank constructions, we consider an EVOH barrier for 

portable and PWC fuel tanks and a polyamide 11 barrier for rotational-molded fuel tanks. UPE 

fiberglass nanocomposite costs presented here are incremental to rotational-molded XLPE tanks. 

6-83 
Final Regulatory Impact Analysis 

Table 6.6-3: Tank Permeation Control Cost Estimates for Typical Marine Vessels 

Portable Tank 

6 gallons 

PWC 

17 gallons 

Installed Tank 

57 gallons 

fluorination: short term 

long term 

$9.30 

$7.44 

$26 

$21 

NA 

sulfonation: short term 

long term 

$1.67 

$1.26 

$3.27 

$1.29 

NA 

non-continuous platelets $1.27 $3.37 NA 

multi-layer: short term 

EVOH long term 

$7.74 

$4.22 

$15 

$8.58 

$81 

$68 

multi-layer: short term 

PA11 long term 

NA NA $81 

$68 

multi-layer: CBT NA NA $54 

UPE fiberglass short term 

nanocomposite long term 

NA NA $48 

$39 

epoxy coating: short term 

long term 

$5.47 

$4.85 

$12 

$11 

$43 

$39 

6.6.3 Venting Losses 

For portable fuel tanks, the standards would require the fuel cap to be modified to remove 

the user-controlled screw and add a one-way valve. We estimate that the cost of a vacuum relief 

valve would be about $0.50 more than the manual valve used on portable fuel tanks today. We 

double this cost to account for upgrading the valve for marine applications. For personal 

watercraft, we are not claiming any costs or benefits because these vessels already seal their fuel 

tanks with a pressure relief valve.71 

Larger fuel tanks are currently vented to atmosphere. One emission-control technology 

that could be used to meet our standards would be to seal the fuel tank and use a 1 psi pressure 

relief valve to prevent over-pressure. However, manufacturers have commented that their fuel 

tanks are not designed to withstand pressure and that the current molding process does not lend 

itself to making the fuel tanks more pressure resistant. Their fuel tanks currently deflect 

significantly at pressures as low as 1 psi. However, for some fuel tank constructions, a sealed 

system may be a viable option. For our cost analysis of this approach, we estimate the cost of a 

pressure relief valve to be about $1 based on products available in automotive applications. We 

double this cost to account for either upgrading the valve for marine applications or adding a 

redundant valve for safety reasons. For this case, we consider in the costs, changes in the fuel 

tank design to make it more able to withstand 1 psi of pressure. We estimate that if 

manufacturers were to make changes to the geometry of the fuel tank to help withstand 1 psi of 

pressure without significant deflection, it could increase the material needed by 10 to 30 percent. 

We include a cost estimate of $2,500 for the development of each new mold and amortize it over 

6-84 
Costs of Control 

100 tanks per year for 5 years. If the pressure relief valve is placed in the fill-neck cap, no vent 

hose would be needed, which would reduce the cost of the fuel system. For the long-term cost 

estimate, we consider the cost savings of removing the vent line. For this analysis, based on 

conversations with boat builders, we divide the aftermarket hose price72 by four to represent the 

cost of the hose to the boat builder. 

Diurnal emissions may also be controlled through the use of a carbon canister in the vent 

line. The carbon would be purged by air drawn into the fuel tank as the fuel cools. This is 

known as passive purge. With a canister system, no significant pressure would build up in the 

fuel tank. The canister would be packaged in the existing vent line and a float valve or other 

liquid/vapor separation device would be added to the fuel system to ensure that liquid fuel would 

not enter the vent line during refueling. We include a cost of $2 for this valve and $0.40 for two 

additional hose clamps. In our cost estimates, we consider a canister using marine grade carbon 

which is harder and more moisture resistant than typical carbon used in automotive applications. 

Data shows that about 2 liters of carbon would be necessary for a 50 gallon fuel tank.73 We 

estimate the cost of a canister to vary based on size ranging from about $12 for a 20 gallon tank 

to about $38 for a 100 gallon tank. 

Pressure could be completely eliminated using a bladder fuel tank because there would 

be no vapor space. Based on conversations with a manufacturer of bladder fuel tanks, the 

incremental cost of adding a bladder to a fuel tank would increase the fuel tank cost by 30-100 

percent, depending on the size and shape of the fuel tank. As with a control strategy using a 

pressure relief valve in the fill neck, no vent hose would be needed with a bladder fuel tank. 

Pressure in the fuel tank can be minimized by reducing the vapor space in the fuel tank. 

A volume compensating air bag can be used to minimize pressure. This air bag would need to be 

about 1/4 to 1/3 the volume of the fuel tank. For this analysis we use 1/3 the cost of the bladder 

fuel tank to account for the smaller bag size. We also include the cost of a low pressure psi 

valve which could be used in conjunction with this technology as a safety backup. 

Table 6.6-4: Venting Control Cost Estimates for Typical Marine Vessels 

Portable Fuel Tank 

6 gallons 

Installed Fuel Tank 

57 gallons 

pressure relief valve: short term

long term 

$1.29 

$1.03 

$26 

$21 

passive purge canister: short term 

long term 

NA 

NA 

$32 

$25 

bladder fuel tank: short term 

long term 

NA 

NA 

$259 

$207 

volume compensating short term 

air bag: long term 

NA 

NA 

$91 

$73 

6-85 
Final Regulatory Impact Analysis 

6.6.4 Certification and Compliance 

We anticipate that manufacturers will use design based certification to as an alternative to 

emission testing to meet the diurnal emission requirements. However, they will still need to 

integrate the emission-control technology into their designs and there will be some engineering 

and clerical effort need to submit the required information for certification. We expect that in 

the early years, plastic fuel tank manufacturers will perform durability and permeation testing on 

their fuel tanks for certification. They will be able to carry over this data in future years and will 

be able to carry across this data to other fuel tanks made of similar materials and using the same 

permeation control strategy regardless of tank size or shape. Typical certification costs may be 

spread between the tank manufacturer, hose manufacturer, and boat builder. For the sake of this 

analysis we combine the tank, hose, and boat certification costs to calculate the total certification 

of an average fuel system. We estimate that 80 percent of fuel tank sales are plastic and about 25 

percent of fuel tanks sold are portable fuel tanks. 

For the first year we estimate fuel tank durability and certification testing to cost about 

$15,000 per tank manufacturer on the assumption that the manufacturer will use the same 

materials and permeation control strategy for all of their fuel tanks to reduce costs. Low 

permeation fuel lines are largely established technology. However, we include a cost of $1,000 

to perform certification testing on marine hose. In addition, we estimate about $10,000 for 

engineering and clerical work for the tank and hose manufacturers. Boat builder certification 

should be a simple letter referencing the tank and hose certificates and design requirements. We 

consider a cost of $500 for this effort. 

For portable fuel tank manufacturers we spread these costs over sales of 25,000 tanks per 

year. For PWC manufacturers, which are integrated manufacturers, we base the costs on average 

annual PWC sales which we estimate to be about 15,000 units per year. For vessels with 

installed fuel tanks, the same tank manufacturer will often sell to many boat builders. Therefore, 

we base the cost on average sales per tank manufacturer which we estimate to be about 40,000 

per year. Although there is currently a limited offering of marine fuel hose products today, we 

conservatively use the same lower unit volumes as for fuel tanks when applying hose testing 

costs. This represents the scenario where portable fuel tank manufacturers and PWC 

manufacturers perform their own hose testing, while smaller boat builders rely on data from the 

hose manufacturers. For non-integrated boat builders using installed fuel tanks, we estimate that 

the average sales per year is approximately 250 vessels. 

As with other fixed costs, we amortized the cost over 5 years of sales to calculate per unit 

certification costs. Combining these costs, we get average fuel system integration and 

compliance costs of about $0.22 for portable fuel tanks, $0.35 for PWC, and $0.53 for fuel 

systems on other vessels. 

6.6.5 Operating Cost Savings 

Evaporative emissions are essentially fuel that is lost to the atmosphere. Over the 

lifetime of a marine vessel, this can result in a significant loss of fuel. The reduction in 

6-86 
Costs of Control 

evaporative emissions would therefore result in meaningful fuel savings which can be directly 

related to operating cost savings based on an average density of 6 lbs/gallon for gasoline (based 

on lighter hydrocarbons which evaporate first) and the price of gasoline described above. 

Table 6.6-5 presents the estimated fuel savings for marine vessels associated with the 

evaporative emission standards. 

Table 6.6-5: Projected Evaporative Fuel Savings for Marine Vessels 

Portable PWC Installed 

Evaporative HC Reduced [lbs/life] 80 53 228 

Lifetime Gallons Saved 13 9 38 

Lifetime Cost Savings $24 $16 $68 

Average Equipment Life [years] 12.7 9.9 17 

Discounted Cost Savings (7%) $17 $12 $42 

6.6.6 Total Marine Vessel Costs 

We expect that marine vessel manufactures will make use of a variety of technologies to 

meet the fuel tank permeation and diurnal emission standards. As discussed above, many 

options are available so the technologies chosen will depend on the baseline fuel tank 

construction, the vessel type, and the manufacturer’s particular preferences. The hose 

permeation standards will likely be met through the use of barrier hose constructions. 

In calculating the costs of this rule, we consider the marine vessel categories in the 

NONROAD model. NONROAD divides marine vessels into outboard, personal watercraft, and 

SD/I applications and further subdivides these applications into several engine power categories. 

This analysis uses the unique hose and tank sizes for each subcategory in the NONROAD model 

and described in Chapter 3. For this analysis, we treat all vessels with outboard engines up to 25 

hp as having portable fuel tanks made of plastic. This analysis considers all PWC to have plastic 

fuel tanks as well. Based on our understanding of the market share of plastic versus aluminum 

tanks, we use a split of 30 percent metal and 70 percent plastic for installed fuel tanks. 

We base our cost analysis on likely technologies that manufactures may use. For 

portable and PWC fuel tanks and, we base our tank permeation control costs on multi-layer 

coextrusion with an EVOH barrier. For larger installed fuel tanks, we split the costs 50/50 

between dual-layer rotational-molded tanks with a nylon barrier and the use of a low-permeation 

epoxy coating over the tanks in a post molding process. Diurnal control costs are based on 

sealed systems for portable marine tanks, current technology for PWC, and passive canister 

systems for vessels with installed fuel tanks. Fuel supply line costs are based on thermoelastic 

barrier technology. No costs or benefits are claimed for vent hose or fill neck hose. 

As discussed above, our cost estimates include both variable and fixed costs, and we 

6-87 
Final Regulatory Impact Analysis 

distinguish between near-term and long-term costs. Because our analysis amortizes fixed costs 

over 5 years, the long-term costs are generally made up of variable costs only. The exception to 

this is fuel tank permeation control strategies where more expensive molding equipment is used. 

We assume an equipment life of 10 years, so in the long term, the amortized additional cost of 

the molding equipment is half, on average, of the short-term amortized cost over 5 years (5 years 

of amortized payments/10 years of equipment life = 1⁄2). In addition, variable costs are lower in 

the long term due to the learning effect discussed in Section 6.1. Table 6.6-6 presents these 

average per-engine cost estimates. 

Table 6.6-6: Per Vessel Evaporative Emission Cost Estimates (Without Fuel Savings) 

Short Term (years 1-5) Long Term (years 6-10) 

Fixed Variable Total Fixed Variable Total 

Portable aggregate

 tank permeation

 hose permeation

 diurnal venting 

$6.65 

$6.64 

$0.01 

$0 

$5.39 

$1.00 

$3.10 

$1.29 

$12.04 

$7.65 

$3.10 

$1.29 

$3.21 

$3.21 

$0 

$0 

$5.13 

$1.00 

$3.10 

$1.03 

$8.34 

$4.22 

$3.10 

$1.03 

PWC aggregate

 tank permeation

 hose permeation

 diurnal venting 

$12.95 

$12.93 

$0.01 

$0 

$4.49 

$2.64 

$1.84 

$0 

$17.43 

$15.58 

$1.86 

$0 

$6.30 

$6.30 

$0 

$0 

$4.49 

$2.64 

$1.84 

$0 

$10.79 

$8.94 

$1.84 

$0 

Installed aggregate

 tank permeation

 hose permeation

 diurnal venting 

$0.63 

$0.23 

$0.01 

$0.40 

$73.55 

$35.31 

$6.54 

$31.69 

$74.18 

$35.54 

$6.54 

$32.09 

$0 

$0 

$0 

$0 

$61.53 

$29.63 

$6.54 

$25.35 

$61.53 

$29.63 

$6.54 

$25.35 

6.6.7 Marine Vessel Aggregate Costs 

Aggregate costs are calculated by multiplying the per-vessel variable cost estimates 

described above by projected vessel sales and adding in fixed costs as incurred. Vessel sales are 

based on estimates from the National Marine Manufacturers Association (www.nmma.org) and 

projections for future years are based on the growth rates in the NONROAD model. A 

description of the sales and population data and our analysis of the data are available in the 

docket.74 Fuel savings are calculated directly from the projected HC reductions due to the 

evaporative emission standards. Table 6.6-7 presents the projected costs of the rule over a 30-

year time period with and without the fuel savings associated with reducing evaporative 

emissions. For the purposes of combining these costs with the exhaust emission costs described 

above, we also present the projected costs by engine type in Table 6.6-8. 

The population and sales data reported by NMMA, suggest that the NONROAD model 

may somewhat underestimate the useful life of outboard and personal watercraft marine vessels. 

If useful life were back-calculated—dividing NMMA population by sales and adjusted for 

growth—we would get a longer average life estimate. As a result, the per-vessel fuel savings 

6-88 
Costs of Control 

described above may be understated. Because the current approach gives us a conservative 

benefits estimate, and because we do not have new data on average lives for marine vessels to 

update the estimates in the NONROAD model, we are not updating the model at this time. For 

this reason, the 30-year stream may give a better view of the impact of the fuel savings than the 

per-vessel analysis. 

At a 7 percent discount rate, over 30 years, the estimated annualized cost to 

manufacturers for marine evaporative emission control is $21 million. The estimated 

corresponding annualized fuel savings due to control of evaporative emissions from boats is $22 

million. At a 3 percent discount rate, the estimated annualized cost to manufacturers for marine 

evaporative emission control is $23 million. The estimated corresponding annualized fuel 

savings due to control of evaporative emissions from boats is $27 million. 

Table 6.6-7: Projected 30-Year Aggregate Cost Stream for Marine Vessels 

Year 

Without Fuel Savings With Fuel Savings 

Portable PWC Installed Portable PWC Installed 

2008 

2009 

2010 

2011 

2012 

2013 

2014 

2015 

2016 

2017 

2018 

2019 

2020 

2021 

2022 

2023 

2024 

2025 

2026 

2027 

2028 

2029 

2030 

2031 

2032 

2033 

2034 

2035 

2036 

2037

 $36,474 

$803,917 

$857,095 

$594,826 

$599,164 

$603,502 

$607,839 

$593,848 

$598,004 

$602,159 

$606,314 

$610,470 

$614,625 

$618,781 

$622,936 

$627,091 

$631,247 

$635,402 

$639,584 

$643,765 

$647,947 

$652,129 

$656,310 

$660,492 

$664,674 

$668,855 

$673,037 

$677,219 

$681,400 

$685,582 

$67,297 

$1,461,840 

$1,395,094 

$855,964 

$862,207 

$868,449 

$874,691 

$880,933 

$887,097 

$893,262 

$899,426 

$905,590 

$911,754 

$917,918 

$924,083 

$930,247 

$936,411 

$942,575 

$948,778 

$954,982 

$961,185 

$967,388 

$973,591 

$979,794 

$985,998 

$992,201 

$998,404 

$1,004,607 

$1,010,810 

$1,017,014 

$425,096 

$2,437,783 

$2,118,774 

$13,113,533 

$25,655,601 

$25,841,342 

$26,027,084 

$26,212,826 

$24,120,397 

$22,380,137 

$22,534,578 

$22,689,018 

$22,843,458 

$22,997,898 

$23,152,338 

$23,306,778 

$23,461,218 

$23,615,659 

$23,771,076 

$23,926,494 

$24,081,911 

$24,237,329 

$24,392,747 

$24,548,164 

$24,703,582 

$24,859,000 

$25,014,417 

$25,169,835 

$25,325,252 

$25,480,670 

$36,474 

$550,181 

$299,968 

$(352,563)

 $(787,374)

 $(1,194,787)

 $(1,593,995)

 $(2,011,013)

 $(2,403,445)

 $(2,791,322)

 $(3,170,164)

 $(3,541,264)

 $(3,893,751)

 $(4,217,582)

 $(4,502,321)

 $(4,715,380)

 $(4,892,031)

 $(5,047,877)

 $(5,189,699)

 $(5,318,214)

 $(5,440,156)

 $(5,551,536)

 $(5,655,549)

 $(5,745,992)

 $(5,828,655)

 $(5,903,314)

 $(5,963,979)

 $(6,018,898)

 $(6,068,556)

 $(6,116,187)

 $67,297 

$1,401,963 

$1,271,709 

$516,639 

$308,552 

$103,461 

$(97,802)

 $(295,433)

 $(487,095)

 $(673,068)

 $(850,586)

 $(1,000,808)

 $(1,134,586)

 $(1,212,981)

 $(1,270,967)

 $(1,318,185)

 $(1,357,627)

 $(1,391,089)

 $(1,418,920)

 $(1,441,800)

 $(1,460,469)

 $(1,475,218)

 $(1,486,959)

 $(1,496,432)

 $(1,505,907)

 $(1,515,381)

 $(1,524,855)

 $(1,534,329)

 $(1,543,803)

 $(1,553,278)

 $425,096 

$1,913,103 

$1,028,968 

$10,845,446 

$21,179,415 

$19,143,903 

$17,118,227 

$15,098,006 

$10,806,108 

$6,882,907 

$4,872,062 

$2,878,316 

$901,070 

$(1,069,567)

 $(3,020,477)

 $(4,922,205)

 $(6,725,979)

 $(8,386,163)

 $(9,827,107)

 $(11,086,083)

 $(12,248,543)

 $(13,295,437)

 $(14,225,862)

 $(15,039,376)

 $(15,694,795)

 $(16,270,514)

 $(16,778,147)

 $(17,215,402)

 $(17,601,830)

 $(17,945,566) 

6-89 
Final Regulatory Impact Analysis 

Table 6.6-8: Projected 30-Year Aggregate Cost Stream 

for Marine Vessels by Engine Type 

Year 

Without Fuel Savings With Fuel Savings 

OB PWC SD/I OB PWC SD/I 

2008 

2009 

2010 

2011 

2012 

2013 

2014 

2015 

2016 

2017 

2018 

2019 

2020 

2021 

2022 

2023 

2024 

2025 

2026 

2027 

2028 

2029 

2030 

2031 

2032 

2033 

2034 

2035 

2036 

2037

 $319,871 

$2,656,653 

$2,502,577 

$8,678,125 

$15,269,926 

$15,380,478 

$15,491,029 

$15,583,252 

$14,360,302 

$13,168,410 

$13,259,282 

$13,350,154 

$13,441,026 

$13,531,898 

$13,622,771 

$13,713,643 

$13,804,515 

$13,895,387 

$13,986,834 

$14,078,282 

$14,169,729 

$14,261,176 

$14,352,623 

$14,444,071 

$14,535,518 

$14,626,965 

$14,718,413 

$14,809,860 

$14,901,307 

$14,992,754 

$67,297 

$1,461,840 

$1,395,094 

$855,964 

$862,207 

$868,449 

$874,691 

$880,933 

$887,097 

$893,262 

$899,426 

$905,590 

$911,754 

$917,918 

$924,083 

$930,247 

$936,411 

$942,575 

$948,778 

$954,982 

$961,185 

$967,388 

$973,591 

$979,794 

$985,998 

$992,201 

$998,404 

$1,004,607 

$1,010,810 

$1,017,014 

$141,699 

$585,047 

$473,292 

$5,030,234 

$10,984,838 

$11,064,366 

$11,143,894 

$11,223,423 

$10,358,098 

$9,813,887 

$9,881,610 

$9,949,333 

$10,017,057 

$10,084,780 

$10,152,503 

$10,220,227 

$10,287,950 

$10,355,674 

$10,423,826 

$10,491,978 

$10,560,130 

$10,628,281 

$10,696,433 

$10,764,585 

$10,832,737 

$10,900,889 

$10,969,041 

$11,037,193 

$11,105,345 

$11,173,497 

$319,871 

$1,906,143 

$912,594 

$5,726,980 

$10,170,561 

$8,145,273 

$6,134,930 

$4,108,869 

$776,555 

$(2,506,681)

 $(4,483,567)

 $(6,438,915)

 $(8,363,328)

 $(10,247,532)

 $(12,075,309)

 $(13,785,575)

 $(15,367,391)

 $(16,791,879)

 $(17,990,346)

 $(19,002,879)

 $(19,924,799)

 $(20,741,603)

 $(21,455,586)

 $(22,105,569)

 $(22,684,596)

 $(23,205,543)

 $(23,661,696)

 $(24,055,883)

 $(24,404,310)

 $(24,716,953)

 $67,297 

$1,401,963 

$1,271,709 

$516,639 

$308,552 

$103,461 

$(97,802)

 $(295,433)

 $(487,095)

 $(673,068)

 $(850,586)

 $(1,000,808)

 $(1,134,586)

 $(1,212,981)

 $(1,270,967)

 $(1,318,185)

 $(1,357,627)

 $(1,391,089)

 $(1,418,920)

 $(1,441,800)

 $(1,460,469)

 $(1,475,218)

 $(1,486,959)

 $(1,496,432)

 $(1,505,907)

 $(1,515,381)

 $(1,524,855)

 $(1,534,329)

 $(1,543,803)

 $(1,553,278)

 $141,699 

$557,141 

$416,341 

$4,765,903 

$10,221,480 

$9,803,842 

$9,389,302 

$8,978,125 

$7,626,108 

$6,598,266 

$6,185,465 

$5,775,967 

$5,370,647 

$4,960,383 

$4,552,511 

$4,147,990 

$3,749,381 

$3,357,839 

$2,973,540 

$2,598,583 

$2,236,099 

$1,894,631 

$1,574,175 

$1,320,201 

$1,161,147 

$1,031,715 

$919,570 

$821,583 

$733,924 

$655,200 

6.7 Cost Sensitivity Analysis 

In developing the cost estimates described above, EPA used data from a wide variety of 

sources. These sources included conversations with manufacturers and vendors, published 

material costs, government cost tracking, and sales literature. In addition, we discussed many of 

our cost estimates with industry experts. Through this process we have received information 

suggesting that there is the potential for variability in some of the cost estimates used as inputs to 

this analysis. For instance, fuel prices have been rising over the past few years which affects the 

dollar value of our fuel savings estimates. 

In this section, we perform an analysis of the sensitivity of our cost estimates to the 

6-90 
Costs of Control 

observed variation in costs for several input components of the cost analysis. The input 

components that we are focusing on for the sensitivity analysis are those that would be expected 

to have a significant effect on the final cost results. These are components that we either 

observed high variability when collecting the data, or industry has raised issues about the 

uncertainty of the technology which may lead to cost uncertainty. 

We are focusing on five elements of the cost analysis for this sensitivity analysis. These 

five elements are: 

1. gasoline prices 

2. precious metal costs 

3. fraction of Small SI equipment manufacturers that design their own mufflers 

4. electronic fuel injection on all Class II engines with multiple cylinders 

5. costs of rotational-molded tank technologies 

6.7.1 Gasoline Price Sensitivity 

To estimate fuel savings in the above analysis, we used fuel price information obtained 

from the U.S. Department of Energy, Energy Information Administration (EIA) which posts 

gasoline price samples throughout the year on-line.75 For 2004 and 2005, national fuel prices are 

based on an analysis of fuel prices by PADD as reported by EIA in 2006.76 For years later than 

2005, we use the estimates reported in the 2008 Annual Energy Outlook report also developed 

by EIA.77 Based on this information, the national average fuel price, with taxes, grew from 

$2.20 in 2005 to $2.99 in 2008. This price estimate includes both a $0.184/gallon federal excise 

tax and approximately a $0.21/gallon average state excise tax.78 Subtracting these taxes, we get 

a fuel cost of $2.60/gallon for 2008. 

To investigate the sensitivity of the cost analysis in this chapter to gasoline fuel price, we 

looked at the U.S. average fuel prices for 2004 and 2007. These price estimates were calculated 

in the same manner as the 2005 estimate. Table 6.7-1 presents these estimates. Fuel savings are 

directly related to the gasoline price used in the cost analysis. Therefore, if the 2004 average 

gasoline price were used in the cost analysis, the estimated fuel savings would have been about 

22 percent lower. If the 2008 projected price were used, the estimated fuel savings would have 

been about 33 percent higher. Because of the recent trend of increasing gasoline prices, we may 

be understating the fuel savings in our cost analysis. However, using the 2005 fuel price is 

consistent with our use of 2005 dollars for the costs in this chapter. 

Table 6.7-1 U.S. Average Gasoline Prices [$/Gallon] 

Year with taxes without taxes 

2004 

2005 

2006 

2007 

2008 (projected) 

$1.80 

$2.20 

$2.63 

$2.77 

$2.99 

$1.41 

$1.81 

$2.44 

$2.37 

$2.60 

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Final Regulatory Impact Analysis 

As discussed above, our analysis of fuel savings uses a constant fuel price for all future 

years. To the extent that fuel prices were to fluctuate in future years, this could have an impact 

on realized fuel savings. To investigate the sensitivity of our analysis to future fuel prices, we 

considered fuel price projections from the EIA’s 2008 Annual Energy Outlook.79 EIA 

projections include primary estimates of fuel prices, known as the “reference case,” as well as 

“high price” estimates. These projections, which include taxes on motor gasoline, are shown in 

Figure 6.7-1. EIA projections from AEO 2007 and AEO 2006 are also presented for 

comparison. Note that the EIA reference cases show relatively flat fuel price projections beyond 

2010, when the fuel savings associated with this rule would be realized. 

Figure 6.7-1: EIA Motor Gasoline Projections [Include Taxes] 

EIA Motor Gasoline Projections 

(Sales weighted-average price for all grades. Includes Federal, State, and local taxes) 

2008 2013 2018 2023 2028 

$-

$0.50 

$1.00 

$1.50 

$2.00 

$2.50 

$3.00 

$3.50 

$4.00 

$/gallon (with taxes) 

FRM 

AEO 2006 

AEO 2007 

AEO 2008 

AEO 2008 HIGH PRICE 

Table 6.7-2 presents our fuel savings estimates for this rule and presents a comparison 

with modified estimates using the EIA fuel price projections. Consistent with the above 

discussion, we adjusted the fuel price estimates to remove taxes on motor gasoline. Compared to 

the primary EPA estimate, using the reference case projections would result in about a 9 percent 

increase in estimated fuel savings. Using the high price estimate would result in about a 60 

percent increase in estimated fuel savings. 

6-92 
Costs of Control 

Table 6.7-2: Sensitivity of Fuel Savings Estimates to Gasoline Price Projections 

Year 

Price without Taxes Per Gallon Fuel Savings [million dollars] 

Primary AEO 2008 

Reference 

AEO 2008 

High Price 

Primary AEO 2008 

Reference 

AEO 2008 High 

Price 

2008 

2009 

2010 

2011 

2012 

2013 

2014 

2015 

2016 

2017 

2018 

2019 

2020 

2021 

2022 

2023 

2024 

2025 

2026 

2027 

2028 

2029 

2030 

2031 

2032 

2033 

2034 

2035 

2036 

2037

 $1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$1.81 

$2.60 

$2.36 

$2.16 

$2.09 

$2.02 

$1.95 

$1.94 

$1.86 

$1.80 

$1.82 

$1.84 

$1.91 

$1.97 

$1.93 

$1.95 

$1.96 

$1.95 

$1.97 

$1.98 

$1.99 

$2.02 

$2.04 

$2.06 

$2.06a

 $2.06a

 $2.06a

 $2.06a

 $2.06a

 $2.06a

 $2.06a

 $2.60 

$2.39 

$2.45 

$2.48 

$2.51 

$2.55 

$2.61 

$2.62 

$2.67 

$2.73 

$2.77 

$2.82 

$2.89 

$2.97 

$3.01 

$3.01 

$3.03 

$3.00 

$3.01 

$3.04 

$3.06 

$3.09 

$3.13 

$3.13a

 $3.13a

 $3.13a

 $3.13a

 $3.13a

 $3.13a

 $3.13a 

$3 

$8 

$20 

$45 

$72 

$97 

$118 

$137 

$154 

$168 

$181 

$194 

$204 

$214 

$224 

$233 

$241 

$248 

$255 

$261 

$267 

$272 

$277 

$282 

$286 

$290 

$294 

$297 

$301 

$304 

$5 

$11 

$24 

$52 

$80 

$105 

$126 

$140 

$153 

$168 

$184 

$204 

$221 

$228 

$241 

$251 

$259 

$269 

$278 

$287 

$297 

$306 

$314 

$319 

$324 

$329 

$333 

$337 

$341 

$345 

$5 

$11 

$27 

$61 

$100 

$137 

$169 

$198 

$226 

$253 

$277 

$301 

$325 

$351 

$371 

$386 

$402 

$411 

$423 

$437 

$450 

$464 

$479 

$487 

$494 

$501 

$507 

$514 

$520 

$525 

Annualized Savings 

[million dollars] 

3% 

7% 

$180 

$156 

$197 

$169 

$293 

$249 

a Based on estimate for 2030. AEO 2008 does not project fuel prices beyond 2030. 

6.7.2 Variation in Precious Metal Prices 

Precious metal prices for Platinum and Rhodium have increased over the past 5 years.80 

Prices for palladium are currently at their 1998 levels. However, a large spike in palladium 

prices was seen in 2000 and 2001. Due to the high variability of this market, we get higher 

precious metal cost estimates if we based the price estimates on a recent single month average 

(September 2006). If we look at an average over a longer time period (10 years) we calculate 

lower platinum costs, but higher rhodium and palladium costs. These precious metal price 

estimates are presented in Table 6.7-3. 

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Final Regulatory Impact Analysis 

Table 6.7-3: Precious Metal Prices [per troy oz] 

ICF 3 year Average September 2006 10 Year Average 

Rhodium $1,121 $4,835 $1,356 

Palladium $210 $316 $341 

Platinum $811 $1,134 $623 

6.7.2.1 Sensitivity of Small SI Catalyst Costs to Precious Metal Costs 

To look at the sensitivity of our cost analysis for Small SI exhaust emission control, we 

considered the precious metal cost variability described above. Based on the amount of each of 

these precious metals in our projected catalyst designs, Table 6.7-4 presents the impact on perengine costs of using the spot price and 10 year average price in our analysis. These costs, 

which are broken down by class and useful life, are presented for the near term without fuel 

savings. 

Table 6.7-4: Sensitivity of Small SI Total Per Engine Cost Estimates 

to Precious Metal Costs 

CLASS I I I II II II 

UL 125 250 500 250 500 1000 

TECH OHV/SV OHV OHV OHV OHV OHV 

RULE Cost/Equip 14.12 19.82 26.07 46.21 50.83 92.17 

(3 yr avg precious 

metal price) 

SEPTEMBER 2006 PRICE 

Cost/Equip $15.69 $22.60 $30.25 $47.48 $52.67 $96.11 

Increase $1.57 $2.78 $4.18 $1.27 $1.84 $3.94 

% Increase 10% 12% 14% 3% 4% 4% 

10 YEAR AVERAGE 

Cost/Equip $13.91 $19.45 $25.51 45.84 $51.39 $93.80 

Increase -$0.21 -$0.37 -$0.56 $-0.37 $0.56 $1.63 

%Increase -1.5% -1.9% -2.2% -1% 1% 2% 

6.7.2.1 Sensitivity of SD/I Catalyst Costs to Precious Metal Costs 

To look at the sensitivity of our cost analysis for SD/I exhaust emission control, we 

considered the precious metal cost variability described above. Based on the amount of each of 

6-94 
Costs of Control 

these precious metals in our projected catalyst designs, Table 6.7-5 presents the impact on perengine costs of using the spot price and 10 year average price in our analysis. These costs, 

which are presented for each of the engine sizes used above for the primary cost analysis, are 

near term costs without fuel savings. 

6-95 
Final Regulatory Impact Analysis 

Table 6.7-5: Sensitivity of SD/I Cost Estimates to Precious Metal Costs 

3.0L I4 4.3L V6 5.0L V8 5.7L V8 8.1L V8 

Primary Analysis $483 $396 $317 $300 $377 

September 2006 Precious Metal Prices 

Cost 

Increase 

% Increase 

$511 

$28 

5% 

$417 

$21 

5% 

$342 

$24 

7% 

$328 

$28 

8% 

$416 

$39 

9% 

10 Year Average Precious Metal Prices 

Cost 

Increase 

% Increase 

$479 

-$4 

-1% 

$393 

-$3 

-1% 

$314 

-$4 

-1% 

$296 

-$4 

-1% 

$371 

-$6 

-2% 

Catalyst manufacturers usually buy precious metals on contract, not at the market spot 

price. Our primary analysis values appear reasonable. 

6.7.3 Portion of Equipment Manufacturers Designing Own Muffler System and 

Recertifying the Engine 

This analysis considers that equipment manufacturers will purchase the muffler design 

provided by the engine manufacturer in the engine’s certified engine configuration. However, 

due to the fact that engine manufacturers will likely not be able to provide catalysts in all of the 

muffler designs used by equipment manufacturers, the smaller volume equipment manufacturer 

will need to pick their muffler from the limited offerings of the engine manufacturer. 

The muffler designs may or may not fit into the equipment produced by the equipment 

manufacturer. If it does not, then the equipment manufacturer may choose to utilize the catalyst 

brick from their engine manufacturer and work with a muffler manufacturer to redesign their 

existing muffler. If they choose this option, then they must undergo expenses to redesign the 

muffler and heat shield to apply the catalyst safely. The equipment manufacturer must also pay 

for emission test of the new engine/muffler configuration as well as pay the certification fee to 

EPA for engine certification. 

Applications which may find issues using a predetermined muffler design include those 

that have close coupled equipment shrouding or a closed equipment structure. EPA estimates 

that 10 percent of equipment companies will find themselves in this situation with at least one 

piece of equipment in their product line. Given there are an estimated 413 companies, 41 

companies with three differently designed models each yields 123 models. Given that there are 

at times more than one engine used in an equipment design, we can assume two engine types per 

model - this yields a total of 246 redesigns and certifications. The fixed costs for this work are 

listed in Table 6.7-6. 

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Costs of Control 

Table 6.7-6: Costs for Equipment Manufacturers 

6-97 
Final Regulatory Impact Analysis 

to Perform Engine Certification, Class II OHV 

Fixed Costs 

Muffler/Heat Shield Design $75,000 

Emission Test per Certified Engine Configuration $2012 

Estimated EPA Certification Fee $800 

TOTAL Per Equipment Model Per Engine Type $77,812 

10% of Equipment Manufacturers = 41 (x41) 41 

Three equipment models per equipment mfr. 123 

Two engine types per Equipment Model (x2) 246 

TOTAL ESTIMATED COST $19,141,752 

If this occurred it would add about $19 million dollars to the total compliance cost or 

about 0.86 percent of the total 30 year cost net present value. 

6.7.4 Electronic Fuel Injection on Class II Engines with Multiple Cylinders 

The current analysis states that only a portion of an engine manufacturers Class II engine 

families of two or more cylinders per engine will incorporate electronic fuel injection. In the 

event that success with the technology results in all Class II engines of two or more cylinders 

using the technology, then the cost stream of this rulemaking will change. Table 6.7-7 compares 

the estimated costs of catalysts and fuel injection. 

Table 6.7-7: Cost Comparison Between Catalyst and EFI 

Technology Class II V-twin 

250 500 1000 

Variable Costs 

V-Twin Catalyst $49.59 $53.47 $62.32 

Electronic Fuel 

Injection 

$78.99 $78.99 $78.99 

Difference $28.40 $25.52 $16.67 

Fixed Costs 

V-Twin Catalyst $364,133 $364,133 $364,133 

Electronic Fuel $103,020 $103,020 $103,020 

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Costs of Control 

Difference -$261,113 -$261,113 -$261,113 

The resultant change in cost/equipment for this is shown in Table 6.7-8. The costs 

presented here are for the near term and long term without fuel savings. The reason that costs do 

not change very much overall is due to the fact that there is still a significant portion of Class II 

engines that are single cylinder whose costs estimates are not changing. 

Table 6.7-8 

Sales Weighted Average Cost Per Class II Equipment 

250 500 1000 

Short Term (first year - includes fixed costs)

 Primary analysis $46.21 $50.83 $92.17

 All Class II V-Twin to EFI $46.80 $49.71 $91.55 

Difference $0.59 

1.3% 

-$1.12 

2.2% 

-$0.62 

0.67% 

Long Term (6th year and beyond)

 Primary analysis $32.56 $27.13 $49.80

 All Class II V-Twin to EFI $33.16 $27.15 $50.62 

Difference $0.60 

1.8% 

$0.02 

0.07% 

$0.82 

1.6% 

The estimated fuel savings for a residential riding mower is $39.00 net present value over 

its lifetime. EFI is estimated to cost $79.00 after consideration of the savings from removal of 

the existing carburetor. Therefore, the increase in the overall hardware cost with fuel savings is 

$40.00. 

6.7.5 Costs of Rotational-Molded Tank Technologies 

Many of the fuel tank permeation control technologies discussed in Chapter 5 are used 

widely today. One exception is multi-layer rotationally-molded fuel tanks. One tank 

manufacturer is currently producing fuel tanks for Small SI equipment with a nylon inner layer. 

This manufacturer has stated that they are able to produce these fuel tanks using the normal 

molding process without additional equipment. However, other manufacturers who sell tanks 

into Small SI and marine applications have expressed concern that they do not know how to 

mold tanks with nylon inner liners without the use of a drop box. As described above, a drop 

box is an added component on a mold that opens during the molding process to add a second 

layer of material into the mold. These manufacturers have indicated that they are working with 

another material, CBT (discussed above and in Chapter 5), that would not require a drop box. 

6-99 
Final Regulatory Impact Analysis 

However, they have not finished their evaluation of this technology. Marine fuel tank 

manufacturers have expressed the concern that if the cost of plastic fuel tanks were too high, that 

more boat builders may begin using aluminum fuel tanks. 

To examine the uncertainty in what technologies will be used to reduce permeation from 

rotationally molded fuel tanks, we considered three factors listed below. As with the analysis 

above, we present costs for typical fuel tank sizes rather than trying to present every fuel tank 

size considered in the cost model. The two fuel tank sizes used here are a 5 gallon tank for 

Small SI equipment and a 57 gallon fuel tank for boats. 

1. Cost of using a drop box in the rotational-molding process 

2. Sensitivity to variations in material costs 

3. Consideration of replacing plastic with metal fuel tanks in marine industry 

In the analysis described above, we include a $5,000 cost per mold in the near term to 

account for the cost using drop boxes. This cost was based on a range of cost estimates supplied 

by tank manufacturers ranging from $1,000 to nearly $9,000 per mold for adding drop boxes. In 

the long term we projected that tank manufacturers would all be able to mold fuel tanks without 

the use of a drop box. This projection was based on the current practices of one manufacturer 

and on alternative processes that other manufacturers are investigating today. To look at the 

sensitivity of tank permeation control costs for rotationally-molded fuel tanks, we consider costs 

without drop boxes and with $9,000 drop boxes. 

Table 6.7-9: Sensitivity of Rotomolded Tank Cost Estimates to Drop Box Cost 

5 Gallon Small SI Tank 57 Gallon Boat Tank 

Primary Analysis ($5,000 drop box) $5.54 $81 

Without Drop Box 

Cost 

Increase 

% Increase 

$4.25 

($1.29) 

-23% 

$68 

($13) 

-16% 

With $9,000 Drop Box 

Cost 

Increase 

% Increase 

$6.58 

1.04 

19% 

$92 

$10 

13% 

The analysis above considers three multi-layer approaches to rotationally-molded fuel 

tanks. These approaches are molding with a nylon inner layer using a drop box, molding with a 

slightly more expensive CBT layer without a drop box, and a post processing epoxy coating. All 

three of these approaches would be sensitive to changes in barrier material prices. Because these 

are new materials for fuel tank applications, it would be possible that material costs would 

decrease over time with increased production volumes. At the same time, increases in material 

6-100 
Costs of Control 

costs could occur, especially for materials with prices tied closely to petroleum prices (such as 

polyethylene). To consider the sensitivity of fuel tank cost to material costs, we consider the fuel 

tank construction with a nylon barrier. Here we consider both a 20 percent decrease and a 20 

percent increase in material costs, both for the nylon and the cross-link polyethylene. This 

translates a cross-link polyethylene cost ranging from $0.96 to $1.44/lb. and nylon costs ranging 

from to a nylon cost ranging from $3.20 to $4.80/lb. for Small SI and $4.8 to $7.2/lb. for marine 

fuel tanks. 

Table 6.7-10: Sensitivity of Rotomolded Tank Cost Estimates to Material Cost 

5 Gallon Small SI Tank 57 Gallon Boat Tank 

Primary Analysis $5.54 $81 

20% Decrease in Material Costs 

Cost 

Increase 

% Increase 

$5.18 

($0.85) 

-15% 

$68 

($14) 

-17% 

20% Increase in Material Costs 

Cost 

Increase 

% Increase 

$6.40 

$0.86 

15% 

$95 

($14) 

17% 

Marine fuel tanks that are installed in marine vessels are primarily rotationally-molded 

out of cross-link polyethylene. However, many fuel tank are also made of aluminum. Very 

large fuel tanks (typically greater in size than rotationally-molded fuel tanks) are often made out 

of fiberglass. Marine fuel tank manufacturers making rotationally-molded fuel tanks have 

expressed the concern that if the costs were to increase too high, that many boat builders would 

switch to using aluminum fuel tanks. Based on conversations with industry, plastic fuel tanks 

sell for about 2/3 to 3/4 the price of aluminum fuel tanks. 

One manufacturer of multi-layer rotationally-molded fuel tanks with a nylon inner layer 

has stated that they sell these fuel tanks at a price about 50 percent higher than traditional monolayer fuel tanks. Although this puts the plastic tanks into the price range of metal fuel tanks, 

there are other downstream costs that would also need to be considered. Boat builders have 

indicated that it is common for aluminum fuel tanks to corrode when exposed to water. For this 

reason, they typically include a large access panel to the fuel tank when metal fuel tanks are 

used. The use of an access panel greatly reduces the cost of replacing a fuel tank if necessary. 

This access panel adds cost and complexity to the boat and may affect where the fuel tank can be 

positioned in the boat. Boat manufacturers have indicated that, when plastic fuel tanks are used, 

the only access required is to the hose connections on one end of the fuel tank. 

In addition to the cost of an access panel for removing corroded tanks, the cost of 

replacing the fuel tank must be considered. This would essentially double the price of the metal 

tank, even without considering labor costs. In addition, fuel spills could create other damage in 

6-101 
Final Regulatory Impact Analysis 

the boat or even a safety hazard. Repeated problems with fuel tank corrosion could hurt the 

reputation of the boat builder and leave them open to litigation. For these reasons, many boat 

builders that have already chosen to use plastic fuel tanks would be expected to continue to use 

these fuel tanks, even if they were roughly the same cost as metal fuel tanks. 

We analyzed at two effects that could have an impact on our estimate of the price of low 

permeation plastic fuel tanks. It seems unlikely that a high cost drop box would be necessary 

given that one manufacturer is already producing multi-layer tanks without using a drop box. In 

addition, the CBT technology is designed to not require the use of a drop box. While material 

costs may fluctuate, it is not likely that a 20 percent increase in nylon would be observed. The 

volume of this material sold is large and this rule would not be expected to limit availability of 

the material. In addition, manufacturers have indicated that nylon prices have not risen greatly 

with increased petroleum costs. Even with a 20 percent material price increase it seems unlikely 

that boat builders would switch to using metal tanks. Manufacturers using plastic tanks have 

indicated that they do so more for durability advantages with respect to corrosion than for a price 

savings. In addition, the life time cost savings of plastic fuel tanks would outweigh the material 

price increase. These lifetime cost savings include the installation of access ports to allow 

replacement of the tanks, actual replacement of corroded tanks, and customer perception of poor 

quality if tanks were to corrode. 

6-102 
Costs of Control 

Chapter 6 References 

1. “Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

2. “Update of EPA's Motor Vehicle Emission Control Equipment Retail Price Equivalent (RPE) Calculation 

Formula,” Jack Faucett Associates, Report No. JACKFAU-85-322-3, September 1985, Docket Identification EPAHQ-OAR-2004-0008-0204. 

3. For further information on learning curves, see Chapter 5 of the Economic Impact, from “Regulatory Impact 

Analysis—Control if Air Pollution from New Motor Vehicles: Tier 2 Motor Vehicle Emissions Standards and 

Gasoline Sulfur Control Requirements,” U.S. EPA, December 1999, EPA420-R-99-023. A copy of this document is 

included in Air Docket A-2000-01, at Document No. II-A-83. The interested reader should also refer to previous 

final rules for Tier 2 highway vehicles (65 FR 6698, February 10, 2000), marine diesel engines (64 FR 73300, 

December 29, 1999), nonroad diesel engines (63 FR 56968, October 23, 1998), and highway diesel engines (62 FR 

54694, October 21, 1997). 

4. “Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

5.“Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

6. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower,” U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

7. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower,” U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

8. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower,” U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

9.“Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

10.“Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

11. “Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

12. “Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

13. “Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

6-103 
Final Regulatory Impact Analysis 

14. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower,” U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

15. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower,” U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

16. “Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

17.“Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

18.“Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

19.“Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

20.“Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

21. “Small SI Engine Technologies and Costs, Draft Report” ICF International, prepared for U.S. Environmental 

Protection Agency, August 2006, Docket Identification EPA-HQ-OAR-2004-008-0253. 

22. “EPA Technical Study on the Safety of Emission Controls for Nonroad Spark-Ignition Engines < 50 

Horsepower,” U.S. Environmental Protection Agency, EPA420-R-06-006, March 2006, Docket Identification EPAHQ-OAR-2004-0008-0329. 

23. “Small SI Engine Technologies and Costs, Draft Report,” ICF International, August 2006, Docket Identification 

EPA-HQ-OAR-2004-008-0253. 

24. “Small SI Engine Technologies and Costs, Draft Report,” ICF International, August 2006, Docket Identification 

EPA-HQ-OAR-2004-008-0253. 

25. “Summary of 2002 Nonhandheld Equipment Market by Manufacturer Size”, EPA Memo by Phil Carlson to 

Docket EPA_HQ_OAR_2004_0008_0542. 

26. “Build it, and they will come,” OEM Off-Highway, page 74-78, November 1996. 

27. “EFI Hits the Small Engine Market,” Diesel Progress, pages 52-54, July 1998. 

28. Memorandum from Alex Rogozhin, RTI, to Chi Li, U.S. EPA, “Calculation of Motor Gasoline Prices in Small SI 

Rule EIA,” November 10, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0449. 

29. “Marine Outboard and Personal Watercraft SI Engine Technologies and Costs,” ICF Consulting, prepared for 

the U.S. Environmental Protection Agency, July 2006, Docket Identification EPA-HQ-OAR-2004-0008-0452. 

30. Memorandum from Alex Rogozhin, RTI, to Chi Li, U.S. EPA, “Calculation of Motor Gasoline Prices in Small SI 

Rule EIA,” November 10, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0449. 

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Costs of Control 

31. “Updates to Technology Mix, Emissions Factors, Deterioration Rates, Power Distribution, and Fuel 

Consumption Estimates for SI Marine Engines in the NONROAD Emissions Inventory Model,” Memorandum from 

Mike Samulski, U.S. EPA to Docket, November 30, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0361. 

32. “Updates to Technology Mix, Emissions Factors, Deterioration Rates, Power Distribution, and Fuel 

Consumption Estimates for SI Marine Engines in the NONROAD Emissions Inventory Model,” Memorandum from 

Mike Samulski, U.S. EPA to Docket, November 30, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0361. 

33. Samulski, M., “Marine SI Sales and Price Estimates,” U.S. EPA, August 30, 2004, Docket Identification EPAHQ-OAR-2004-0008-0448. 

34. “Sterndrive and Inboard Marine SI Engine Technologies and Costs,” ICF Consulting, prepared for the U.S. 

Environmental Protection Agency, July 2006, Docket Identification EPA-HQ-OAR-2004-0008-0453. 

35. “Updates to Technology Mix, Emissions Factors, Deterioration Rates, Power Distribution, and Fuel 

Consumption Estimates for SI Marine Engines in the NONROAD Emissions Inventory Model,” Memorandum from 

Mike Samulski, U.S. EPA to Docket, November 30, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0361. 

36. Samulski, M., “Marine SI Sales and Price Estimates,” U.S. EPA, August 30, 2004, Docket Identification EPAHQ-OAR-2004-0008-0448. 

37. Trident Marine Hose, “Retail Price List 2001,” Docket Identification EPA-HQ-OAR-2004-0008-0226. 

38. Denbow, R., Browning, L., Coleman, D., “Report Submitted for WA 2-9, Evaluation of the Costs and 

Capabilities of Vehicle Evaporative Emission Control Technologies,” ICF, ARCADIS Geraghty & Miller, March 

22, 1999, Docket Identification EPA-HQ-OAR-2004-0008-0194. 

39. “Meeting with Avon on June 27, 2002,” Memorandum from Mike Samulski, U.S. EPA to Docket A-2000-01, 

August 6, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0207. 

40. “Information on Costs and Effectiveness of Fluorination Received from Fluoroseal,” Memorandum from Mike 

Samulski to Docket A-2000-1, March 27, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0201. 

41. “Visit to Sulfo Technologies LLC on April 18, 2002,” Memorandum from Mike Samulski, U.S. EPA to Docket 

A-2000-01, April 22, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0232. 

42. “Shipping Costs,” Memorandum from Glenn Passavant, U.S. EPA to Docket A-2000-01, March 27, 2002, 

Docket Identification EPA-HQ-OAR-2004-0008-0222. 

43. “Visit to Sulfo Technologies LLC on April 18, 2002,” Memorandum from Mike Samulski, U.S. EPA to Docket 

A-2000-01, April 22, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0232. 

44. “Plastic News,” Resin Pricing for November 8, 2004, www.plasticnews.com, Docket Identification EPA-HQOAR-2004-0008-0442. 

45. Ward, Geoff, “Potential Small Entity Representative (SER) Response to Initial Outreach Document: Exhaust 

and Evaporative Emissions Control from Small SI Engines and Equipment and Marine SI Engines and Vessels,” 

Agri-Industrial Plastics, July 25, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0427. 

46. “Plastic News,” Resin Pricing for November 8, 2004, www.plasticnews.com, Docket Identification EPA-HQOAR-2004-0008-0442. 

47. “Visit to Kracor, Inc.,” Memorandum from Mike Samulski, U.S. EPA to Docket A-2000-02, March 31, 2003, 

Docket Identification EPA-HQ-OAR-2004-0008-0249. 

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Final Regulatory Impact Analysis 

48. Written comments from Robert Porter, Inca Molded Products to Phil Carlson, U.S.EPA regarding impacts of 

regulation on small business, July 24, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0426. 

49. Written comments from Jim Harden, Grady-White Boats to Phil Carlson, U.S.EPA regarding impacts of 

regulation on small business, July 25, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0437. 

50. “Petro-Seal for Ultra-Low Fuel Permeation,” Ron Partridge, Arkema Inc., Presentation at the International Boat 

Exposition, October 25, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0252. 

51. “Plastic News,” Resin Pricing for November 8, 2004, www.plasticnews.com, Docket Identification EPA-HQOAR-2004-0008-0442. 

52. “Information on Costs and Effectiveness of Fluorination Received from Fluoroseal,” Memorandum from Mike 

Samulski to Docket A-2000-1, March 27, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0201. 

53. Written comments from Robert Porter, Inca Molded Products to Phil Carlson, U.S.EPA regarding impacts of 

regulation on small business, July 24, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0426. 

54. Written comments from Jim Harden, Grady-White Boats to Phil Carlson, U.S.EPA regarding impacts of 

regulation on small business, July 25, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0437. 

55. “Comments by Brunswick Corporation; Notice of Proposed Rulemaking; Part 1045 Control of Emissions from 

Spark-Ignition Marine Vessels,” Rolf Lichtner, Mercury Marine, January 7, 2003, Docket Identification EPA-HQOAR-2004-0008-0192. 

56. Trident Rubber Inc., “Trident Marine Hose, Retail Price List 2001,” Docket Identification EPA-HQOAR-2004-0008-0226. 

57. Denbow, R., Browning, L., Coleman, D., “Report Submitted for WA 2-9, Evaluation of the Costs and 

Capabilities of Vehicle Evaporative Emission Control Technologies,” ICF, ARCADIS Geraghty & Miller, March 

22, 1999, Docket Identification EPA-HQ-OAR-2004-0008-0194. 

58. “Meeting with Avon on June 27, 2002,” Memorandum from Mike Samulski, U.S. EPA to Docket A-2000-01, 

August 6, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0207. 

59. Lawrence Marine; NovaFlex Group, “Industrial Price List: Marine Products,” October 15, 2004, Docket 

Identification EPA-HQ-OAR-2004-0008-0439. 

60. Trident Rubber Inc., “Trident Marine Hose, Retail Price List, October 2005,” Docket Identification EPA-HQOAR-2004-0008-0444. 

61. “Information on Costs and Effectiveness of Fluorination Received from Fluoroseal,” Memorandum from Mike 

Samulski to Docket A-2000-1, March 27, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0201. 

62. “Visit to Sulfo Technologies LLC on April 18, 2002,” Memorandum from Mike Samulski, U.S. EPA to Docket 

A-2000-01, April 22, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0232. 

63. “Shipping Costs,” Memorandum from Glenn Passavant, U.S. EPA to Docket A-2000-01, March 27, 2002, 

Docket Identification EPA-HQ-OAR-2004-0008-0222. 

64. “Plastic News,” Resin Pricing for November 8, 2004, www.plasticnews.com, Docket Identification EPA-HQOAR-2004-0008-0442. 

6-106 
Costs of Control 

65. Ward, Geoff, “Potential Small Entity Representative (SER) Response to Initial Outreach Document: Exhaust 

and Evaporative Emissions Control from Small SI Engines and Equipment and Marine SI Engines and Vessels,” 

Agri-Industrial Plastics, July 25, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0427. 

66. “Petro-Seal for Ultra-Low Fuel Permeation,” Ron Partridge, Arkema Inc., Presentation at the International Boat 

Exposition, October 25, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0252. 

67. “Information on Costs and Effectiveness of Fluorination Received from Fluoroseal,” Memorandum from Mike 

Samulski to Docket A-2000-1, March 27, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0201. 

68. Written comments from Robert Porter, Inca Molded Products to Phil Carlson, U.S.EPA regarding impacts of 

regulation on small business, July 24, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0426. 

69. Written comments from Jim Harden, Grady-White Boats to Phil Carlson, U.S.EPA regarding impacts of 

regulation on small business, July 25, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0437. 

70. “Marine Fuel Containment; A Permanent Solution,” Jason Chambers, Engineered Composite Structures Inc., 

Presentation at the 2004 International Boat Exposition, October 25, 2004, Docket Identification EPA-HQOAR-2004-0008-0247. 

71. Meetings with NMMA on Marine Emission Standards,” Memorandum from Mike Samulski, U.S. EPA to 

Docket A-2000-02, March 4, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0250. 

72. Trident Marine Hose, “Retail Price List 2001,” Docket Identification EPA-HQ-OAR-2004-0008-0226. 

73. “Activated Carbon for Use in Marine Evaporative Control Applications,” MeadWestvaco Corporation, 

Presentation at the International Boat Exposition, October 25, 2004, Docket Identification EPA-HQOAR-2004-0008-0248. 

74. Samulski, M., “Marine SI Sales and Price Estimates,” U.S. EPA, August 30, 2004, Docket Identification EPAHQ-OAR-2004-0008-0448. 

75. Energy Information Administration, “Retail Gasoline Historical Prices,” downloaded from 

http://www.eia.doe.gov/oil_gas/petroleum/data_publications/wrgp/mogas_history.html, on February 28, 2008. 

76. Memorandum from Alex Rogozhin, RTI, to Chi Li, U.S. EPA, “Calculation of Motor Gasoline Prices in Small SI 

Rule EIA,” November 10, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0449. 

77. Energy Information Administration, “Annual Energy Outlook 2008; with Projections to 2030,” 

DOE/EIA-0383(2008), June 2008. 

78. Federal Highway Administration, “Tax Rates on Motor Fuel - 2003," downloaded from 

http://www.eia.doe.gov/oil_gas/petroleum/data_publications/wrgp/gasoline_taxes.html on October 25, 2006, Docket 

Identification EPA-HQ-OAR-2004-0008-0451. 

79. Energy Information Administration, “Annual Energy Outlook 2008; with Projections to 2030,” 

DOE/EIA-0383(2008), June 2008. 

80. Johnson Matthey, “Platinum Today,” www.platinum.matthey.com, downloaded October 25, 2006, Docket 

Identification EPA-HQ-OAR-2004-0008-0422. 

6-107 

Cost Per Ton 

CHAPTER 7: Cost Per Ton 

This Chapter will present the cost effectiveness analysis we completed for our proposed 

small spark ignition engine (<19 kW) and recreational marine (personal water craft, 

sterndrive/inboard and outboard) emission standards. Under Clean Air Act section 213, we are 

required to promulgate standards which reflect the greatest degree of emission reduction 

achievable, giving appropriate consideration to cost, energy, and safety factors. The standards 

setting process is not necessarily premised on setting the most cost effective standards, even 

though this is a significant factor. Cost-effectiveness is a useful tool in evaluating the 

appropriateness of our standards. 

The cost-effectiveness analysis described in this chapter relies in part on cost information 

from Chapter 6 and emissions information from Chapter 3 to estimate the dollars per ton of 

emission reductions produced from our proposed standards. We have calculated the cost 

effectiveness using a 30-year net present value approach that accounts for all costs and emission 

reductions over a 30-year period. Finally, this chapter compares the cost effectiveness of the 

new provisions with the cost effectiveness of other control strategies from previous and potential 

future EPA programs. 

Section 7.1 describes the calculation behind the 30 year net present value cost 

effectiveness and Section 7.2 lists the results of the calculations for our combined small spark 

ignition standards (exhaust and evaporative) and marine engines (exhaust and evaporative). 

Table 7.2-.5 lists the results for the 30-year net present value cost effectiveness analysis for 

Small SI and Marine. The results of the cost-effectiveness of comparative programs are listed in 

Table 7.2-6. 

7.1 30-Year Net Present Value Cost Effectiveness (Cost per Ton) 

We have calculated the cost effectiveness of our program using a “30-year net present 

value” approach that includes all nationwide emission reductions and costs for a 30 year period. 

This timeframe captures both the early period of the program when only the new 

equipment/engines meeting our standards will be in the fleet, and the later period when 

essentially all vehicles/engines in the fleet will meet our standards. The 30-year net present 

value approach does have one important drawback in that it includes the engine costs for engines 

sold 30 years after the program goes into effect, but includes almost none of the emission 

benefits from those engines. Thus the 30-year net present value approach does not necessarily 

match all costs with all the emission reductions that those costs are intended to produce. It is 

presented here, nevertheless, as a reasonable means by which to assess the cost effectiveness of 

these programs. 

We have calculated this “30-year net present value” cost-effectiveness using the net 

present value of the annual emission reductions and costs described in Chapters 3 and 6, 

respectively. The calculation of 30-year net present value cost-effectiveness follows the pattern 

described above for the per-engine analysis: 

7-1 
Final Regulatory Impact Analysis 

DNAE = 3 (NE)i /(1.07)i-2008 

Where: 

DNAE = Reduction in nationwide 30-year net present value emissions in tons 

(NE)i = Reduction in nationwide emissions in tons for year i of the program 

i = Year of the program, counting from year 1 to year 30 

and 

DNAC = 3 (NC)i /(1.07)i-2008 

Where: 

DNAC = Nationwide 30-year net present value costs in dollars 

(NC)i = Nationwide costs in dollars for year i of the program 

i = Year of the program from year 1 to year 30 

The 30-year net present value cost-effectiveness is produced by dividing DNAC by DNAE. The 

nationwide reductions in emissions for each year are given in Chapter 3. The results are given in 

Tables within the following section. 

7.2 Results 

We calculated the cost-effectiveness of our program on a 30-year net present value basis 

separately for our proposed Small SI standards <19kW and recreational marine standards. To do 

this, we summed net present value of total costs from Chapter 6, and divided by the sum of the 

net present value of tons reduced from Chapter 3. These costs and emission reductions are 

repeated in Appendices 7-A and 7-B. The results are given in Table 7.2-1 to 7.2-2 for Small SI 

engines and equipment and 7.2-3 and 7.2-4 for recreational marine engines and vessels. 

Table 7.2-1: 30-year Net Present Value Cost-effectiveness of the Standards 

for Small SI Engines <19kW Without Fuel Savings (7 percent discount rate) 

Pollutants 

HC+NOx 

NPV Costs 

(million $) 

NPV Reduction 

(tons) 

Cost per Ton 

Exhaust $2,257 1,785,000 $1,264 

Evaporative $809 1,098,000 $736 

Exhaust + Evap $3067 2,883,000 $1,063 

7-2 
Cost Per Ton 

Table 7.2-2: 30-year Net Present Value Cost-effectiveness of the Standards 

for Small SI Engines <19kW With Fuel Savings (7 percent discount rate) 

Pollutants 

HC+NOx 

NPV Costs 

(million $) 

NPV Reduction 

(tons) 

Cost per Ton 

Exhaust $1,959 1,785,000 $1,097 

Evaporative $151 1,098,000 $137 

Exhaust + Evap $2,110 2,883,000 $856 

Table 7.2-3: 30-year Net Present Value Cost-effectiveness of the Standards 

for Marine Engines Without Fuel Savings (7 percent discount rate) 

Pollutants 

HC+NOx 

NPV Costs 

(million $) 

NPV Reduction 

(tons) 

Cost per Ton 

Exhaust $1,521 1,826,000 $833 

Evaporative $270 461,000 $585 

Exhaust + Evap $1,790 2,287,000 $783 

Table 7.2-4: 30-year Net Present Value Cost-effectiveness of the Standards 

for Marine Engines With Fuel Savings (7 percent discount rate) 

Pollutants 

HC+NOx 

NPV Costs 

(million $) 

NPV Reduction 

(tons) 

Cost per Ton 

Exhaust $823 1,826,000 $451 

Evaporative ($6) 461,000 --

Exhaust + Evap $817 2,287,000 $357 

Because many of the benefits and costs are manifest in future years, we apply 

discounting methods to adjust the dollar values of these effects to reflect the finding that society 

as a whole typically values the realization (or avoidance) of a given effect differently depending 

on when the effect occurs. In the discounting calculations used to produce the net present values 

that were used in our cost-effectiveness calculations, we used a discount rate of 7 percent, 

consistent with the 7 percent rate reflected in the cost-effectiveness analyses for other recent 

mobile source programs. OMB Circular A-94 requires us to generate benefit and cost estimates 

reflecting a 7 percent rate. 

However, the cost and cost-effectiveness estimates for future proposed mobile source 

programs could also reflect a 3 percent discount rate. The 3 percent rate is in the 2 to 3 percent 

7-3 
Final Regulatory Impact Analysis 

range recommended by the Science Advisory Board’s Environmental Economics Advisory 

Committee for use in EPA social benefit-cost analyses, a recommendation incorporated in EPA's 

new Guidelines for Preparing Economic Analyses (November 2000). Therefore, we have also 

calculated the overall cost-effectiveness of today's rule based on a 3 percent rate to facilitate 

comparison of the cost-effectiveness of this rule with future proposed rules which use the 3 

percent rate. The results are shown in Tables 7.2-5 through 7.2-8. 

Table 7.2-5: 30-year Net Present Value Cost-effectiveness of the Standards 

for Small SI Engines <19kW Without Fuel Savings (3 percent discount rate) 

Pollutants 

HC+NOx 

NPV Costs 

(million $) 

NPV Reduction 

(tons) 

Cost per Ton 

Exhaust $3,718 3,227,000 $1,152 

Evaporative $1,327 1,932,000 $687 

Exhaust + Evap $5,044 5,159,000 $978 

Table 7.2-6: 30-year Net Present Value Cost-effectiveness of the Standards 

for Small SI Engines <19kW With Fuel Savings (3 percent discount rate) 

Pollutants 

HC+NOx 

NPV Costs 

(million $) 

NPV Reduction 

(tons) 

Cost per Ton 

Exhaust $3,181 3,227,000 $986 

Evaporative $170 1,932,000 $88 

Exhaust + Evap $3,351 5,159,000 $650 

Table 7.2-7: 30-year Net Present Value Cost-effectiveness of the Standards 

for Marine Engines Without Fuel Savings (3 percent discount rate) 

Pollutants 

HC+NOx 

NPV Costs 

(million $) 

NPV Reduction 

(tons) 

Cost per Ton 

Exhaust $2,407 3,425,000 $703 

Evaporative $444 885,000 $502 

Exhaust + Evap $2,852 4,310,000 $662 

7-4 
Cost Per Ton 

Table 7.2-8: 30-year Net Present Value Cost-effectiveness of the Standards 

for Marine Engines With Fuel Savings (3 percent discount rate) 

Pollutants 

HC+NOx 

NPV Costs 

(million $) 

NPV Reduction 

(tons) 

Cost per Ton 

Exhaust $1,100 3,425,000 $321 

Evaporative ($86) 885,000 --

Exhaust + Evap $1,014 4,310,000 $235 

Because one primary purpose of cost-effectiveness is to compare our program to 

alternative programs, we listed the cost effectiveness of several previous EPA actions for 

controlled emissions from mobile sources for NOx and NMHC in Table 7.2-9. The programs 

shown in these tables are those for which cost-effectiveness was calculated in a similar manner 

allowing for a comparison. (Note: costs adjusted to 2005 dollars.) 

Table 7.2-9: Cost-effectiveness of 

Recent Mobile Source Exhaust Emission Programs for HC+NOx, 2005$ 

(7 percent discount with fuel savings) 

Program $/ton 

2002 HH engines Phase 2 840 

2001 NHH Engines Phase 2 neg* 

1998 Marine SI engines 1900 

2004 Comm Marine CI 200 

2007 Large SI exhaust 80 

2006 ATV exhaust 300 

2006 off-highway motorcycle 290 

2006 recreational marine CI 700 

2010 snowmobile 1430 

2006 <50cc highway motorcycle 1860 

2010 Class 3 highway motorcycle 1650 

* fuel savings outweigh engineering/hardware costs 

Costs adjusted to 2005$ using http://www1.jsc.nasa.gov/bu2/inflateGDP.html 

Permeation and other evaporative emission control measures we have implemented for 

highway and off-highway motorcycles, large SI engines, ATVs, and snowmobiles have all had 

cost effectiveness values of less than $0/ton due to the fuel savings. 

The analyses supporting the values in Table 7.2-6 were conducted over the past ten years 

and thus not all were done on a purely identical basis in terms of their analytical approach (e.g., 

factors such as cost streams and cost recovery). By comparing values in Table 7.2-6 for 

NOx+HC to those presented above we can see that the cost-effectiveness of our proposed Small 

SI and recreational Marine SI standards fall within the range of these other programs. Some 

7-5 
Final Regulatory Impact Analysis 

previous programs have been more cost effective (lower $/ton) than the program we are 

proposing today. However, it should be expected that the next generation of standards will be 

more expensive than the last, because earlier reductions are usually easier and less expensive to 

achieve and the least costly means for reducing emissions is generally pursued first. 

This proposed rule also will bring environmental benefits related to reductions in carbon 

monoxide (CO) emissions and emissions of direct particulate matter (PM). We have elected to 

base our cost effectiveness analysis solely on HC+NOx for two reasons. First, with regard to 

PM and CO, no new or additional technology beyond that needed to achieve the proposed 

HC+NOx standards is expected to be required. These reductions will occur as part of the 

technology and related efforts to meet the HC+NOx standards. Second, in the case of PM, we 

are not setting standards but do expect reductions to occur as a result of engine changes and in 

some cases the use of aftertreatment. In neither case is significant additional effort needed. 

7-6 
Final Regulatory Impact Analysis 

CHAPTER 8: Cost-Benefit Analysis 

8.1 Overview 

This chapter presents our analysis of the health and environmental benefits that are 

estimated to occur as a result of the final Small SI and Marine SI engine standards throughout 

the period from initial implementation through 2030. Nationwide, the engines subject to the 

final emission standards in this rule are a significant source of nonroad mobile source air 

pollution. The final standards will reduce exposure to direct PM2.5, NOx, VOCs and air 

toxics emissions and help avoid a range of adverse health effects associated with ambient 

ozone and PM2.5 levels. 

EPA is required by Executive Order (E.O.) 12866 to estimate the benefits and costs of 

regulations with estimated annual impacts of over 100 million dollars. Such regulations tend 

to include major new pollution control regulations. To estimate these benefits and costs, the 

analysis presented here attempts to answer three questions: (1) what are the physical health 

and welfare effects projected to result from particulate matter (PM) and ozone precursors 

(direct PM, VOCs and NOx)? (2) what is the monetary value of the projected changes in 

health and welfare attributable to the final rule? and (3) how do the projected monetized 

benefits compare to the projected costs? This analysis constitutes one part of EPA’s thorough 

examination of the relative merits of this regulation. 

The benefits analysis relies on three major components to answer these questions: 

•	 Calculation of the projected impact of the final rule on the national nonroad emissions 

inventory of precursors to ozone and PM2.5, specifically NOx, VOCs and direct PM, for 

two future years (2020 and 2030). 

•	 Air quality modeling for 2020 and 2030 to determine projected changes in ambient 

concentrations of ozone and PM2.5, reflecting baseline and post-control emissions 

inventories. 

•	 A benefits analysis to determine the projected changes in human health and welfare, both 

in terms of physical effects and monetary value, that result from the projected changes in 

ambient concentrations of ozone and PM2.5 for the modeled standards. 

A wide range of human health and welfare effects are linked with exposure to PM, 

VOCs and NOx. Recent studies have linked short-term ozone exposures with premature 

mortality. Exposure to ozone has also been linked to a variety of respiratory effects including 

hospital admissions and illnesses resulting in school absences. Potential human health effects 

associated with PM2.5 range from premature mortality to morbidity effects linked to long-term 

(chronic) and shorter-term (acute) exposures (e.g., respiratory and cardiovascular symptoms 

resulting in hospital admissions, asthma exacerbations, and acute and chronic bronchitis). 

Welfare effects potentially linked to PM include materials damage and visibility impacts, 

8-1 
Cost-Benefit Analysis 

while ozone can adversely affect the agricultural and forestry sectors by decreasing yields of 

crops and forests. 

The benefits modeling is based on peer-reviewed studies of air quality and health and 

welfare effects associated with improvements in air quality and peer-reviewed studies of the 

dollar values of those public health and welfare effects. All of the benefit estimates for the 

control options in this analysis are based on an analytical structure and sequence consistent 

with benefits analyses performed for the recent analysis of the final Ozone NAAQS and the 

final PM NAAQS analysis.1,2 For a more detailed discussion of the principles of benefits 

analysis used here, we refer the reader to those documents, as well as to the EPA Guidelines 

for Economic Analysis. 

Table 8.1-1 summarizes the annual monetized health and welfare benefits associated 

with the final standards for two years, 2020 and 2030. The estimates in Table 8.1-1, and all 

monetized benefits presented in this chapter, are in year 2005 dollars. There are a few items 

to note about these benefits: 

•	 Using a conservative benefits estimate, the 2020 benefits outweigh the costs by a factor of 

5. Using the upper end of the benefits range, the benefits could outweigh the costs by a 

factor of 19. Likewise, in 2030 benefits outweigh the costs by at least a factor of 8 and 

could be as much as a factor of 34. Thus, even taking the most conservative benefits 

assumptions, benefits of the final standards clearly outweigh the costs. 

•	 Emissions and air quality modeling decisions are made early in the analytical process. For 

this reason, the emission control scenarios used in the air quality and benefits modeling 

are slightly different than the final emission control program. The differences reflect 

further refinements of the regulatory program since we performed the air quality modeling 

for this rule. Chapter 3 of the RIA describes the changes in the inputs and resulting 

emission inventories between the preliminary assumptions used for the air quality 

modeling and the final regulatory scenario. 

•	 The RIA for the proposal for this rulemaking only quantified benefits from PM; in the 

current RIA we quantify and monetize the ozone-related health impacts associated with 

the final rule. The science underlying the analysis is based on the current ozone criteria 

document.3

 The analytic approach to characterizing uncertainty is consistent with the 

analysis used in the RIA for the final Ozone NAAQS. 

•	 In a recent report on the estimation of ozone-related premature mortality published by the 

National Research Council (NRC),4 a panel of experts and reviewers concluded that 

ozone-related mortality should be included in estimates of the health benefits of reducing 

ozone exposure. The report also recommended that the estimation of ozone-related 

premature mortality be accompanied by broad uncertainty analyses while giving little or 

no weight to the assumption that there is no causal association between ozone exposure 

and premature mortality. Because EPA has yet to develop a coordinated response to the 

NRC report’s findings and recommendations, however, we have retained the approach to 

8-2 
Final Regulatory Impact Analysis 

estimating ozone-related premature mortality used in RIA for the final Ozone NAAQS. 

EPA will specifically address the report's findings and recommendations in future 

rulemakings. 

Table 8.1-1. Estimated Monetized PM- and Ozone-Related Health Benefits of the Small 

SI and Marine SI Engine Standards 

2030 Total Ozone and PM Benefits – PM Mortality Derived from American Cancer Society Analysisa 

Premature Ozone 

Mortality Function or 

Assumption 

Reference Mean Total Benefits 

(Billions, 2005$, 3% 

Discount Rate)c,d 

Mean Total Benefits 

(Billions, 2005$, 7% 

Discount Rate) c,d 

NMMAPS Bell et al., 2004 $2.4 $2.2 

Meta-analysis Bell et al., 2005 $3.7 $3.5 

Ito et al., 2005 $4.4 $4.2 

Levy et al., 2005 $4.4 $4.3 

Assumption that association is not causale $1.8 $1.6 

2030 Total Ozone and PM Benefits – PM Mortality Derived from Expert Elicitationb 

Premature Ozone 

Mortality Function or 

Assumption 

Reference Mean Total Benefits 

(Billions, 2005$, 3% 

Discount Rate) c,d 

Mean Total Benefits 

(Billions, 2005$, 7% 

Discount Rate) c,d 

NMMAPS Bell et al., 2004 $1.7 - $9.7 $1.6 - $8.8 

Meta-analysis Bell et al., 2005 $3.0 - $11 $2.9 - $10 

Ito et al., 2005 $3.7 - $12 $3.6 - $11 

Levy et al., 2005 $3.7 - $12 $3.7 - $11 

Assumption that association is not causale $1.1 to $9.1 $1.0 - $8.2 a

 Total includes ozone and PM2.5 benefits. Range was developed by adding the estimate from the ozone 

premature mortality function to the estimate of PM2.5-related premature mortality derived from the American 

Cancer Society analysis (Pope et al., 2002).

b

 Total includes ozone and PM2.5 benefits. Range was developed by adding the estimate from the ozone 

premature mortality function to both the lower and upper ends of the range of the PM2.5 premature mortality 

functions characterized in the expert elicitation. The effect estimates of five of the twelve experts included in the 

elicitation panel fall within the empirically-derived range provided by the ACS and Six-Cities studies. One of 

the experts fall below this range and six of the experts are above this range. Although the overall range across 

experts is summarized in this table, the full uncertainty in the estimates is reflected by the results for the full set 

of 12 experts. The twelve experts’ judgments as to the likely mean effect estimate are not evenly distributed 

across the range illustrated by arraying the highest and lowest expert means. c

 Note that total benefits presented here do not include a number of unquantified benefits categories. A 

detailed listing of unquantified health and welfare effects is provided in Table 8.4-1. 

d

 Results reflect the use of both a 3 and 7 percent discount rate, as recommended by EPA’s Guidelines 

for Preparing Economic Analyses and OMB Circular A-4. Results are rounded to two significant digits for ease 

of presentation and computation. e

 A recent report published by the National Research Council (NRC, 2008) recommended that EPA 

“give little or no weight to the assumption that there is no causal association between estimated reductions in 

premature mortality and reduced ozone exposure.” 

Table 8.1-1 reflects those human health and welfare effects we are able to quantify and 

monetize. However, the full complement of known or suspected human health and welfare 

effects associated with PM, ozone and air toxics remain unquantified because of current 

limitations in methods or available data. We have not quantified potential health and welfare 

effects of ozone and PM because impact functions are not available or do not provide easily 

interpretable outcomes (e.g., changes in heart rate variability, acid and particulate deposition 

8-3 
Cost-Benefit Analysis 

damage to cultural monuments and other materials, and reductions in acidification of lakes 

and streams and eutrophication in coastal areas). As a result, we may underestimate the total 

benefits attributable to the implementation of the final standards. 

This chapter is organized as follows. In Section 8.2, we provide an overview of the air 

quality impacts modeled for the final standards that are used as inputs to the benefits analysis. 

In Section 8.3, we discuss how uncertainty is characterized in this analysis. Section 8.4 

discusses the literature on ozone- and PM-related health effects and describes the specific set 

of health impact functions we used in the benefits analysis. Section 8.5 describes the 

economic values selected to estimate the dollar value of ozone- and PM-related health 

impacts. In Section 8.6, we report the results of the analysis for human health and welfare 

effects. Finally, Section 8.7 presents a comparison of the costs and benefits associated with 

the final standards. There are also two appendices associated with this chapter. The first, 

Appendix 8A, presents the results of the health-based cost effectiveness analysis. The second, 

Appendix 8A, presents the results of sensitivity analyses of key parameters in the benefits 

analysis. 

8.2 Air Quality Impacts for Benefits Analysis 

In Chapter 2, we summarize the methods for and results of estimating air quality for 

the 2020 and 2030 base case and final control scenario. These air quality results are in turn 

associated with human populations and ecosystems to estimate changes in health and welfare 

effects. For the purposes of the benefits analysis, we focus on the health effects that have 

been linked to ambient changes in ozone and PM2.5 related to emission reductions estimated 

to occur due to the final standards. We estimate ambient PM2.5 and ozone concentrations 

using the Community Multiscale Air Quality model (CMAQ). The air quality modeling 

Technical Support Document (TSD), which can be found in the docket for this rule, contains 

detailed information about the modeling conducted for this rule. In this section, we describe 

how the modeled air quality results were used for the benefits analysis. 

We remind the reader that the emission control scenarios used in the air quality and 

benefits modeling are slightly different than the final emission control program. The 

differences reflect further refinements of the regulatory program since we performed the air 

quality modeling for this rule. Emissions and air quality modeling decisions are made early in 

the analytical process. Chapter 3 of the RIA describes the changes in the inputs and resulting 

emission inventories between the preliminary assumptions used for the air quality modeling 

and the final regulatory scenario. 

8.2.1 Converting CMAQ Outputs to Full-Season Profiles for Benefits Analysis 

This analysis extracted hourly, surface-layer PM and ozone concentrations for each 

grid cell from the standard CMAQ output files. For ozone, these model predictions are used 

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Final Regulatory Impact Analysis 

in conjunction with the observed concentrations obtained from the Aerometric Information 

Retrieval System (AIRS) to generate ozone concentrations for the entire ozone season.A,B 

The predicted changes in ozone concentrations from the future-year base case to future-year 

control scenario serve as inputs to the health and welfare impact functions of the benefits 

analysis (i.e., the Environmental Benefits Mapping and Analysis Program [BenMAP]). 

To estimate ozone-related health and welfare effects for the contiguous United States, 

full-season ozone data are required for every BenMAP grid-cell. Given available ozone 

monitoring data, we generated full-season ozone profiles for each location in two steps: (1) 

we combined monitored observations and modeled ozone predictions to interpolate hourly 

ozone concentrations to a grid of 12-km by 12-km population grid cells for the contiguous 48 

states, and (2) we converted these full-season hourly ozone profiles to an ozone measure of 

interest, such as the daily 8-hour maximum.C,D 

For PM2.5, we also use the model predictions in conjunction with observed monitor 

data. CMAQ generates predictions of hourly PM species concentrations for every grid. The 

species include a primary coarse fraction (corresponding to PM in the 2.5 to 10 micron size 

range), a primary fine fraction (corresponding to PM less than 2.5 microns in diameter), and 

several secondary particles (e.g., sulfates, nitrates, and organics). PM2.5 is calculated as the 

sum of the primary fine fraction and all of the secondarily formed particles. Future-year 

estimates of PM2.5 were calculated using relative reduction factors (RRFs) applied to 2002 

ambient PM2.5 and PM2.5 species concentrations. A gridded field of PM2.5 concentrations was 

created by interpolating Federal Reference Monitor ambient data and IMPROVE ambient 

data. Gridded fields of PM2.5 species concentrations were created by interpolating EPA 

speciation network (ESPN) ambient data and IMPROVE data. The ambient data were 

interpolated to the CMAQ 12 km grid. 

The procedures for determining the RRFs are similar to those in EPA’s draft guidance 

for modeling the PM2.5 standard (EPA, 1999). The guidance recommends that model 

predictions be used in a relative sense to estimate changes expected to occur in each major 

PM2.5 species. The procedure for calculating future-year PM2.5 design values is called the 

“Speciated Modeled Attainment Test (SMAT).” EPA used this procedure to estimate the 

ambient impacts of the final emissions controls. Full documentation of the revised SMAT 

methodology is contained in the Air Quality Modeling TSD. 

A The ozone season for this analysis is defined as the 5-month period from May to September. 

B

 Based on AIRS, there were 961 ozone monitors with sufficient data (i.e., 50 percent or more days reporting at 

least nine hourly observations per day [8 am to 8 pm] during the ozone season). 

C

 The 12-km grid squares contain the population data used in the health benefits analysis model, BenMAP. 

D This approach is a generalization of planar interpolation that is technically referred to as enhanced Voronoi 

Neighbor Averaging (EVNA) spatial interpolation. See the BenMAP manual for technical details, available for 

download at http://www.epa.gov/air/benmap. 

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Cost-Benefit Analysis 

8.2.2 Ozone and PM2.5 Air Quality Results 

This section provides a summary of the predicted ambient PM2.5 and ozone 

concentrations from the CMAQ model for the 2020 and 2030 base cases and changes 

associated with the final rule. Table 8.2-1 provides those ozone and PM2.5 metrics for grid 

cells in the modeled domain that enter the health impact functions for health benefits 

endpoints. The population-weighted average reflects the baseline levels and predicted 

changes for more populated areas of the nation. This measure better reflects the potential 

benefits through exposure changes to these populations. 

Table 8.2-1. Summary of CMAQ-Derived Population-Weighted Ozone and PM2.5 Air 

Quality Metrics for Health Benefits Endpoints Due to the Final Small SI and Marine SI 

Engine Standards 

2020 2030 

Statistica Baseline Changeb

 Baseline Changeb 

Ozone Metrics: National Population-Weighted Average (ppb)c 

Daily 1-Hour Maximum Concentration 47.60 0.078 46.91 0.108 

Daily 8-Hour Maximum Concentration 44.07 0.066 43.47 0.093 

Daily 8-Hour Average Concentration 42.63 0.062 42.06 0.088 

Daily 24-Hour Average Concentration 35.39 0.047 35.02 0.068 

PM2.5 Metrics: National Population-Weighted Average (ug/m3

) 

Annual Average Concentration 9.41 0.015 9.38 0.021 a

 Ozone and PM2.5 metrics are calculated at the CMAQ grid-cell level for use in health effects estimates 

based on the results of spatial and temporal Voronoi Neighbor Averaging. Ozone metrics are calculated over 

relevant time periods during the daylight hours of the “ozone season” (i.e., May through September). For the 8-

hour average, for example, the relevant time period is 9 am to 5 pm. 

b

 The change is defined as the base-case value minus the control-case value. 

c

 Calculated by summing the product of the projected CMAQ grid-cell population and the estimated 

CMAQ grid cell seasonal ozone concentration and then dividing by the total population. 

8.3 Characterizing Uncertainty: Moving Toward a Probabilistic 

Framework for Benefits Assessment 

The National Research Council (NRC)5 highlighted the need for EPA to conduct 

rigorous quantitative analysis of uncertainty in its benefits estimates and to present these 

estimates to decision makers in ways that foster an appropriate appreciation of their inherent 

uncertainty. In response to these comments, EPA’s Office of Air and Radiation (OAR) is 

developing a comprehensive strategy for characterizing the aggregate impact of uncertainty in 

key modeling elements on both health incidence and benefits estimates. Components of that 

process include emissions modeling, air quality modeling, health effects incidence estimation, 

and valuation. 

In benefit analyses of air pollution regulations conducted to date, the estimated impact 

of reductions in premature mortality has accounted for 85% to 95% of total benefits. 

8-6 
Final Regulatory Impact Analysis 

Therefore, it is particularly important to characterize the uncertainties associated with 

reductions in premature mortality. The health impact functions used to estimate avoided 

premature deaths associated with reductions in ozone have associated standard errors that 

represent the statistical errors around the effect estimates in the underlying epidemiological 

studies.E

 In our results, we report credible intervals based on these standard errors, reflecting 

the uncertainty in the estimated change in incidence of avoided premature deaths. We also 

provide multiple estimates, to reflect model uncertainty between alternative study designs. In 

addition, we characterize the uncertainty introduced by the inability of existing empirical 

studies to discern whether the relationship between ozone and pre-mature mortality is causal 

by providing an effect estimate preconditioned on an assumption that the effect estimate for 

pre-mature mortality from ozone is zero. 

For premature mortality associated with exposure to PM, we follow the same approach 

that has been used in several recent RIAs.F,G,H First, we use Monte Carlo methods for 

estimating random sampling error associated with the concentration response functions from 

epidemiological studies and economic valuation functions. Monte Carlo simulation uses 

random sampling from distributions of parameters to characterize the effects of uncertainty on 

output variables, such as incidence of premature mortality. Specifically, we used Monte 

Carlo methods to generate confidence intervals around the estimated health impact and dollar 

benefits. Distributions for individual effect estimates are based on the reported standard 

errors in the epidemiological studies. Distributions for unit values are described in Table 8.5-

1. 

Second, we use the results of our expert elicitation of the concentration response 

function describing the relationship between premature mortality and ambient PM2.5 

concentration.I, J Incorporating only the uncertainty from random sampling error omits 

important sources of uncertainty (e.g., in the functional form of the model; whether or not a 

E

 Health impact functions measure the change in a health endpoint of interest, such as hospital admissions, for a 

given change in ambient ozone or PM concentration. 

F

 U.S. Environmental Protection Agency, 2004a. Final Regulatory Analysis: Control of Emissions from 

Nonroad Diesel Engines. EPA420-R-04-007. Prepared by Office of Air and Radiation. Available at 

http://www.epa.gov/nonroad-diesel/2004fr/420r04007.pdf 

G U.S. Environmental Protection Agency, 2005. Regulatory Impact Analysis for the Clean Air Interstate Rule. 

EPA 452/-03-001. Prepared by Office of Air and Radiation. Available at: 

http://www.epa.gov/interstateairquality/tsd0175.pdf 

H U.S. Environmental Protection Agency, 2006. Regulatory Impact Analysis for the PM NAAQS. EPA Prepared 

by Office of Air and Radiation. Available at: http://www.epa.gov/ttn/ecas/regdata/RIAs/Chapter%205--

Benefits.pdf 

I

 Expert elicitation is a formal, highly structured and well documented process whereby expert judgments, 

usually of multiple experts, are obtained (Ayyb, 2002). 

J

 Industrial Economics, Inc. 2006. Expanded Expert Judgment Assessment of the Concentration-Response 

Relationship Between PM2.5 Exposure and Mortality. Prepared for EPA Office of Air Quality Planning and 

Standards, September. Available at: http://www.epa.gov/ttn/ecas/regdata/Uncertainty/pm_ee_report.pdf 

8-7 
Cost-Benefit Analysis 

threshold may exist). This second approach attempts to incorporate these other sources of 

uncertainty. 

Use of the expert elicitation and incorporation of the standard errors approaches 

provide insights into the likelihood of different outcomes and about the state of knowledge 

regarding the benefits estimates. Both approaches have different strengths and weaknesses, 

which are fully described in Chapter 5 of the PM NAAQS RIA. 

These multiple characterizations, including confidence intervals, omit the contribution 

to overall uncertainty of uncertainty in air quality changes, baseline incidence rates, 

populations exposed and transferability of the effect estimate to diverse locations. 

Furthermore, the approach presented here does not yet include methods for addressing 

correlation between input parameters and the identification of reasonable upper and lower 

bounds for input distributions characterizing uncertainty in additional model elements. As a 

result, the reported confidence intervals and range of estimates give an incomplete picture 

about the overall uncertainty in the estimates. This information should be interpreted within 

the context of the larger uncertainty surrounding the entire analysis. 

8.4 Health Impact Functions 

Health impact functions measure the change in a health endpoint of interest, such as 

hospital admissions, for a given change in ambient ozone or PM concentration. Health impact 

functions are derived from primary epidemiology studies, meta-analyses of multiple 

epidemiology studies, or expert elicitations. A standard health impact function has four 

components: 1) an effect estimate from a particular study; 2) a baseline incidence rate for the 

health effect (obtained from either the epidemiology study or a source of public health 

statistics such as the Centers for Disease Control); 3) the size of the potentially affected 

population; and 4) the estimated change in the relevant ozone or PM summary measures. 

A typical health impact function might look like: 

β ⋅Δx Δy = y0 ⋅(e −1), 

where y0 is the baseline incidence (the product of the baseline incidence rate times the 

potentially affected population), $ is the effect estimate, and )x is the estimated change in the 

summary pollutant measure. There are other functional forms, but the basic elements remain 

the same. Section 6.2 described the ozone and PM air quality inputs to the health impact 

functions. The following subsections describe the sources for each of the other elements: 

size of potentially affected populations; effect estimates; and baseline incidence rates. 

8.4.1 Potentially Affected Populations 

The starting point for estimating the size of potentially affected populations is the 

2000 U.S. Census block level dataset.6 Benefits Modeling and Analysis Program (BenMAP) 

incorporates 250 age/gender/race categories to match specific populations potentially affected 

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Final Regulatory Impact Analysis 

by ozone and other air pollutants. The software constructs specific populations matching the 

populations in each epidemiological study by accessing the appropriate age-specific 

populations from the overall population database. BenMAP projects populations to 2020 

using growth factors based on economic projections.7 

8.4.2 Effect Estimate Sources 

The most significant monetized benefits of reducing ambient concentrations of ozone 

and PM are attributable to reductions in human health risks. EPA’s Ozone and PM Criteria 

Documents8,9 and the World Health Organization’s 2003 and 200410,11 reports outline 

numerous health effects known or suspected to be linked to exposure to ambient ozone and 

PM. EPA recently evaluated the PM literature for use in the benefits analysis for the 2006 

PM NAAQS RIA. Because we used the same literature for the PM benefits analysis in this 

RIA, and also in the RIA for the proposed rule, we do not provide a detailed discussion of 

individual effect estimates for PM in this section. Instead, we refer the reader to the 2006 PM 

NAAQS RIA and the proposed Small SI and Marine SI RIA for details.K 

The RIA for the proposal for this rulemaking only quantified benefits from PM; in the 

current RIA we quantify and monetize the ozone-related health and environmental impacts 

associated with the final rule using an approach consistent with the final ozone NAAQS RIA. 

More than one thousand new ozone health and welfare studies have been published since EPA 

issued the 8-hour ozone standard in 1997. Many of these studies investigated the impact of 

ozone exposure on health effects such as: changes in lung structure and biochemistry; lung 

inflammation; asthma exacerbation and causation; respiratory illness-related school absence; 

hospital and emergency room visits for asthma and other respiratory causes; and premature 

death. We provide a discussion of those ozone-related impacts in this section. For a more 

detailed discussion of the health effects of ozone exposure, we point the reader to EPA’s 

ozone Criteria Document.12 

It is important to note that we were not able to separately quantify all of the PM and 

ozone health effects that have been reported in the ozone and PM criteria documents in this 

analysis for four reasons: (1) the possibility of double counting (such as hospital admissions 

for specific respiratory diseases); (2) uncertainties in applying effect relationships that are 

based on clinical studies to the potentially affected population; (3) the lack of an established 

concentration-response relationship; or 4) the inability to appropriately value the effect (for 

example, changes in forced expiratory volume) in economic terms. Table 8.4-1 lists the 

human health and welfare effects of pollutants affected by the final standards. Table 8.4-2 

lists the health endpoints included in this analysis. 

K U.S. Environmental Protection Agency, 2005. Regulatory Impact Analysis for the PM NAAQS. EPA Prepared 

by Office of Air and Radiation. Available at: http://www.epa.gov/ttn/ecas/regdata/RIAs/Chapter%205--

Benefits.pdf pp. 5-29. 

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CO Health Behavioral effects 

Cost-Benefit Analysis 

 Table 8.4-1 Human Health and Welfare Effects of Pollutants Affected by the 

Final Standards 

Quantified and Monetized in Base 

Pollutant/Effect Estimatesa Unquantified Effects - Changes in: 

Premature mortality based on both 

cohort study estimates and on expert 

elicitationc,d 

Bronchitis: chronic and acute 

Hospital admissions: respiratory 

and cardiovascular 

Emergency room visits for asthma 

Nonfatal heart attacks (myocardial 

PM/Healthb	 	 infarction) 

Lower and upper respiratory illness 

Minor restricted-activity days 

Work loss days 

Asthma exacerbations (asthmatic 

population) 

Respiratory symptoms (asthmatic 

population) 

Infant mortality 

Subchronic bronchitis cases 

Low birth weight 

Pulmonary function 

Chronic respiratory diseases other than chronic bronchitis 

Nonasthma respiratory emergency room visits 

UVb exposure (+/-)e 

Visibility in Southeastern Class I areas 

Visibility in northeastern and Midwestern Class I areas 

Household soiling PM/Welfare 	 	 Visibility in western U.S. Class I areas 

Visibility in residential and non-Class I areas 

UVb exposure (+/-)e 

Premature mortality: short-term 

exposures 

Hospital admissions: respiratory 

Emergency room visits for asthma 

Ozone/Healthf	 	 Minor restricted-activity days 

School loss days 

Asthma attacks 

Acute respiratory symptoms 

Cardiovascular emergency room visits 

Chronic respiratory damageg 

Premature aging of the lungsg 

Nonasthma respiratory emergency room visits 

UVb exposure (+/-)e 

Decreased outdoor worker Yields for commercial crops 

productivity Yields for commercial forests and noncommercial crops 

Damage to urban ornamental plants Ozone/Welfare	 	 Recreational demand from damaged forest aesthetics 

Ecosystem functions 

UVb exposure (+/-)e 

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Final Regulatory Impact Analysis 

Quantified and Monetized in Base 

Pollutant/Effect Estimatesa Unquantified Effects - Changes in: 

Nitrogen 

Deposition/ 

Welfare 

Commercial forests due to acidic sulfate and nitrate 

deposition 

Commercial freshwater fishing due to acidic deposition 

Recreation in terrestrial ecosystems due to acidic 

deposition 

Commercial fishing, agriculture, and forests due to 

nitrogen deposition 

Recreation in estuarine ecosystems due to nitrogen 

deposition 

Ecosystem functions 

Passive fertilization 

Lung irritation 

NOx/Health Lowered resistance to respiratory infection 

Hospital admissions for respiratory and cardiac diseases 

Cancer, including lung (benzene, 1,3-butadiene, 

formaldehyde, acetaldehyde, naphthalene) 

Anemia (benzene) 

Disruption of production of blood components (benzene) 

Reduction in the number of blood platelets (benzene) 

Excessive bone marrow formation (benzene) 

Depression of lymphocyte counts (benzene) 

HC/Toxics 	 Reproductive and developmental effects (1,3-butadiene) 

Healthh 	 Irritation of eyes and mucus membranes (formaldehyde) 

Respiratory irritation (formaldehyde) 

Asthma attacks in asthmatics (formaldehyde) 

Asthma-like symptoms in non-asthmatics (formaldehyde) 

Irritation of the eyes, skin, and respiratory tract 

(acetaldehyde) 

Upper respiratory tract irritation and congestion (acrolein) 

Neurotoxicity (n-hexane, toluene, xylenes) 

Direct toxic effects to animals 

HC/Toxics Bioaccumulation in the food chain 

Welfareh Damage to ecosystem function 

Odor a

 Primary quantified and monetized effects are those included when determining the primary estimate of 

total monetized benefits of the final standards. 

b

 In addition to primary economic endpoints, there are a number of biological responses that have been 

associated with PM health effects including morphological changes and altered host defense mechanisms. The 

public health impact of these biological responses may be partly represented by our quantified endpoints. c

 Cohort estimates are designed to examine the effects of long term exposures to ambient pollution, but 

relative risk estimates may also incorporate some effects due to shorter term exposures (see Kunzli, 2001 for a 

discussion of this issue). 

d While some of the effects of short-term exposure are likely to be captured by the cohort estimates, 

there may be additional premature mortality from short-term PM exposure not captured in the cohort estimates 

included in the primary analysis. e

 May result in benefits or disbenefits. 

f

 The public health impact of biological responses such as increased airway responsiveness to stimuli, 

inflammation in the lung, acute inflammation and respiratory cell damage, and increased susceptibility to 

respiratory infection are likely partially represented by our quantified endpoints. 

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Cost-Benefit Analysis 

g

 The public health impact of effects such as chronic respiratory damage and premature aging of the 

lungs may be partially represented by quantified endpoints such as hospital admissions or premature mortality, 

but a number of other related health impacts, such as doctor visits and decreased athletic performance, remain 

unquantified.

h

 The categorization of unquantified toxic health and welfare effects is not exhaustive. 

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Final Regulatory Impact Analysis 

Table 8.4-2. Ozone- and PM-Related Health Endpoints 

Endpoint Pollutant Study Study Population 

Premature Mortality 

Premature mortality – 

daily time series, nonaccidental 

ozone Bell et al (2004) (NMMAPS study)13 

Meta-analyses: 

Bell et al (2005)14 

Ito et al (2005)15 

Levy et al (2005)16 

All ages 

Premature mortality 

—cohort study, allcause 

PM2.5 Pope et al. (2002)17 

Laden et al. (2006)18 >29 years 

>25 years 

Premature mortality, 

total exposures 

PM2.5 Expert Elicitation (IEc, 2006)19 >24 years 

Premature mortality 

— all-cause 

PM2.5 Woodruff et al. (1997)20 Infant (<1 year) 

Chronic Illness 

Chronic bronchitis PM2.5 Abbey et al. (1995)21 >26 years 

Nonfatal heart attacks PM2.5 Peters et al. (2001)22 Adults (>18 years) 

Hospital Admissions 

Respiratory 

ozone 

Pooled estimate: 

Schwartz (1995) - ICD 460-519 (all resp)23 

Schwartz (1994a; 1994b) - ICD 480-486 

(pneumonia)24,25 

Moolgavkar et al. (1997) - ICD 480-487 

(pneumonia)26 

Schwartz (1994b) - ICD 491-492, 494-496 

(COPD) 

Moolgavkar et al. (1997) – ICD 490-496 

(COPD) 

>64 years 

Burnett et al. (2001)27 <2 years 

PM2.5 Pooled estimate: 

Moolgavkar (2003)—ICD 490-496 (COPD)28 

Ito (2003)—ICD 490-496 (COPD)29 

>64 years 

PM2.5 Moolgavkar (2000)—ICD 490-496 (COPD)30 20–64 years 

PM2.5 Ito (2003)—ICD 480-486 (pneumonia) >64 years 

PM2.5 Sheppard (2003)—ICD 493 (asthma)31 <65 years 

Cardiovascular PM2.5 Pooled estimate: 

Moolgavkar (2003)—ICD 390-429 (all 

cardiovascular) 

Ito (2003)—ICD 410-414, 427-428 (ischemic 

heart disease, dysrhythmia, heart failure) 

>64 years 

PM2.5 Moolgavkar (2000)—ICD 390-429 (all 

cardiovascular) 

20–64 years 

Asthma-related ER 

visits 

ozone 

Pooled estimate: 

Jaffe et al (2003)32 

Peel et al (2005)33 

Wilson et al (2005)34 

5–34 years 

All ages 

All ages 

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Cost-Benefit Analysis 

Endpoint Pollutant Study Study Population 

Asthma-related ER 

visits (con’t) 

PM2.5 Norris et al. (1999)35 0–18 years 

Other Health Endpoints 

Acute bronchitis PM2.5 Dockery et al. (1996)36 8–12 years 

Upper respiratory 

symptoms 

PM2.5 Pope et al. (1991)37 Asthmatics, 9–11 

years 

Lower respiratory 

symptoms 

PM2.5 Schwartz and Neas (2000)38 7–14 years 

Asthma exacerbations PM2.5 Pooled estimate: 

Ostro et al. (2001)39 (cough, wheeze and 

shortness of breath) 

Vedal et al. (1998)40 (cough) 

6–18 yearsa 

Work loss days PM2.5 Ostro (1987)41 18–65 years 

School absence days 

ozone 

Pooled estimate: 

Gilliland et al. (2001)42 

Chen et al. (2000)43 

5–17 yearsb 

Minor Restricted 

Activity Days 

(MRADs) 

ozone Ostro and Rothschild (1989)44 18–65 years 

PM2.5 Ostro and Rothschild (1989) 18–65 years 

a

 The original study populations were 8 to 13 for the Ostro et al. (2001) study and 6 to 13 for the Vedal et al. 

(1998) study. Based on advice from the Science Advisory Board Health Effects Subcommittee (SAB-HES), 

we extended the applied population to 6 to 18, reflecting the common biological basis for the effect in 

children in the broader age group. See: U.S. Science Advisory Board. 2004. Advisory Plans for Health 

Effects Analysis in the Analytical Plan for EPA’s Second Prospective Analysis –Benefits and Costs of the 

Clean Air Act, 1990—2020. EPA-SAB-COUNCIL-ADV-04-004. See also National Research Council 

(NRC). 2002. Estimating the Public Health Benefits of Proposed Air Pollution Regulations. Washington, 

DC: The National Academies Press. 

b

 Gilliland et al. (2001) studied children aged 9 and 10. Chen et al. (2000) studied children 6 to 11. Based on 

recent advice from the National Research Council and the EPA SAB-HES, we have calculated reductions in 

school absences for all school-aged children based on the biological similarity between children aged 5 to 17. 

In selecting epidemiological studies as sources of effect estimates, we applied several 

criteria to develop a set of studies that is likely to provide the best estimates of impacts in the 

U.S. To account for the potential impacts of different health care systems or underlying 

health status of populations, we give preference to U.S. studies over non-U.S. studies. In 

addition, due to the potential for confounding by co-pollutants, we give preference to effect 

estimates from models including both ozone and PM over effect estimates from singlepollutant models.45,46 

A number of endpoints that are not health-related also may significantly contribute to 

monetized benefits. Potential welfare benefits associated with ozone exposure include: 

increased outdoor worker productivity; increased yields for commercial and non-commercial 

crops; increased commercial forest productivity; reduced damage to urban ornamental plants; 

increased recreational demand for undamaged forest aesthetics; and reduced damage to 

ecosystem functions.47,48 While we include estimates of the value of increased outdoor 

worker productivity, estimation of other welfare impacts is beyond the scope of this analysis. 

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Final Regulatory Impact Analysis 

8.4.2.1 Ozone Exposure Metric 

Both the NMMAPS analysis and the individual time series studies upon which the 

meta-analyses were based use the 24-hour average or 1-hour maximum ozone levels as 

exposure metrics. L The 24-hour average is not the most relevant ozone exposure metric to 

characterize population-level exposure. Given that the majority of the people tend to be 

outdoors during the daylight hours and concentrations are highest during the daylight hours, 

the 24-hour average metric is not appropriate. The maximum 1-hour average metric uses an 

exposure window different than that that used for the current ozone NAAQS. Together, this 

means that the most biologically relevant metric is the maximum 8-hour average, which has 

also been the metric for ozone NAAQS since 1997. Thus, for the final rule analysis, we have 

converted ozone mortality health impact functions that use a 24-hour average or 1-hour 

maximum ozone metric to maximum 8-hour average ozone concentration using standard 

conversion functions. 

This practice is consistent both with the available exposure modeling and with the 

form of the current ozone standard. This conversion also does not affect the relative 

magnitude of the health impact function. An equivalent change in the 24-hour average, 

maximum1-hour average, and maximum 8-hour average will provide the same overall change 

in incidence of a health effect. The conversion ratios are based on observed relationships 

between the 24-hour average and maximum 8-hour average ozone values. For example, in the 

Bell et al., 2004 analysis of ozone-related premature mortality, the authors found that the 

relationship between the 24-hour average, the maximum 8-hour average, and the maximum 1-

hour average was 2:1.5:1, so that the derived health impact effect estimate based on the 

maximum 1-hour average should be half that of the effect estimate based on the 24-hour 

values (and the maximum 8-hour average three-quarters of the 24-hour effect estimate). 

8.4.2.2 Premature Mortality Effect Estimates 

While particulate matter is the criteria pollutant most clearly associated with 

premature mortality, recent research suggests that short-term repeated ozone exposure likely 

contributes to premature death. The 2006 Ozone Criteria Document states: “Consistent with 

observed ozone-related increases in respiratory- and cardiovascular-related morbidity, several 

newer multi-city studies, single-city studies, and several meta-analyses of these studies have 

provided relatively strong epidemiologic evidence for associations between short-term ozone 

exposure and all-cause mortality, even after adjustment for the influence of season and PM” 

(EPA, 2006: E-17).49 The epidemiologic data are also supported by newly available 

experimental data from both animal and human studies which provide evidence suggestive of 

L

 An exposure metric is a measure of air quality calculated as the average or maximum of modeled ambient 

concentrations over a relevant time period, such as during the daylight hours of the “ozone season” (which is 

May through September for this analysis). The 24-hour average is therefore calculated as the average of all 

hourly ozone concentrations throughout the day (from 12am to 11:59pm). The 8-hour maximum is the 

maximum hourly value observed between 9am and 5pm each day. The 1-hour maximum is the maximum hourly 

value observed throughout an entire day. 

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Cost-Benefit Analysis 

plausible pathways by which risk of respiratory or cardiovascular morbidity and mortality 

could be increased by ambient ozone. With respect to short-term exposure, the ozone Criteria 

Document concludes: “This overall body of evidence is highly suggestive that ozone directly 

or indirectly contributes to non-accidental and cardiopulmonary-related mortality, but 

additional research is needed to more fully establish underlying mechanisms by which such 

effects occur” (pg. E-18). 

With respect to the time-series studies, the conclusion regarding the relationship 

between short-term exposure and premature mortality is based, in part, upon recent cityspecific time-series studies such as the Schwartz (2004) analysis in Houston and the Huang et 

al. (2004) analysis in Los Angeles.M This conclusion is also based on recent meta-analyses by 

Bell et al. (2005), Ito et al. (2005), and Levy et al. (2005), and a new analysis of the National 

Morbidity, Mortality, and Air Pollution Study (NMMAPS) data set by Bell et al. (2004), 

which specifically sought to disentangle the roles of ozone, PM, weather-related variables, 

and seasonality. The 2006 Criteria Document states that “the results from these metaanalyses, as well as several single- and multiple-city studies, indicate that co-pollutants 

generally do not appear to substantially confound the association between ozone and 

mortality” (p. 7-103). However, CASAC raised questions about the implications of these 

time-series results in a policy context. Specifically, CASAC emphasized that “...while the 

time-series study design is a powerful tool to detect very small effects that could not be 

detected using other designs, it is also a blunt tool” (Henderson, 2006: 3). They point to 

findings (e.g., Stieb et al., 2002, 2003) that indicated associations between premature 

mortality and all of the criteria pollutants, indicating that “findings of time-series studies do 

not seem to allow us to confidently attribute observed effects to individual pollutants” (id.). 

They note that “not only is the interpretation of these associations complicated by the fact that 

the day-to-day variation in concentrations of these pollutants is, to a varying degree, 

determined by meteorology, the pollutants are often part of a large and highly correlated mix 

of pollutants, only a very few of which are measured” (id.). Even with these uncertainties, the 

CASAC Ozone Panel, in its review of EPA’s Staff Paper, found “...premature total nonaccidental and cardiorespiratory mortality for inclusion in the quantitative risk assessment to 

be appropriate.” 

Consistent with the methodology used in the ozone risk assessment found in the 

Characterization of Health Risks found in the Review of the National Ambient Air Quality 

Standards for Ozone: Policy Assessment of Scientific and Technical Information, we included 

ozone mortality in the primary health effects analysis, with the recognition that the exact 

magnitude of the effects estimate is subject to continuing uncertainty. We used effect 

estimates from the Bell et al. (2004) NMMAPS analysis, as well as effect estimates from the 

three meta-analyses. 

M For an exhaustive review of the city-specific time-series studies considered in the ozone staff paper, see: U.S. 

Environmental Protection Agency, 2007. Review of the National Ambient Air Quality Standards for Ozone: 

Policy Assessment of Scientific and Technical Information. Prepared by the Office of Air and Radiation. 

Available at http://www.epa.gov/ttn/naaqs/standards/ozone/data/2007_01_ozone_staff_paper.pdf. pp. 5-36. 

8-16 
Final Regulatory Impact Analysis 

In a recent report on the estimation of ozone-related premature mortality published by 

the National Research Council (NRC),50 a panel of experts and reviewers concluded that 

ozone-related mortality should be included in estimates of the health benefits of reducing 

ozone exposure. The report also recommended that the estimation of ozone-related premature 

mortality be accompanied by broad uncertainty analyses while giving little or no weight to the 

assumption that there is no causal association between ozone exposure and premature 

mortality. Because EPA has yet to develop a coordinated response to the NRC report’s 

findings and recommendations, however, we have retained the approach to estimating ozonerelated premature mortality used in RIA for the final Ozone NAAQS. EPA will specifically 

address the report's findings and recommendations in future rulemakings. 

We estimate the change in mortality incidence and estimated credible intervalN 

resulting from application of the effect estimate from each study and present them separately 

to reflect differences in the study designs and assumptions about causality. However, it is 

important to note that this procedure only captures the uncertainty in the underlying 

epidemiological work, and does not capture other sources of uncertainty, such as uncertainty 

in the estimation of changes in air pollution exposure (Levy et al., 2000). 

8.4.2.3 Respiratory Hospital Admissions Effect Estimates 

Detailed hospital admission and discharge records provide data for an extensive body 

of literature examining the relationship between hospital admissions and air pollution. This is 

especially true for the portion of the population aged 65 and older, because of the availability 

of detailed Medicare records. In addition, there is one study (Burnett et al., 2001) providing 

an effect estimate for respiratory hospital admissions in children under two. 

Because the number of hospital admission studies we considered is so large, we used 

results from a number of studies to pool some hospital admission endpoints. Pooling is the 

process by which multiple study results may be combined in order to produce better estimates 

of the effect estimate, or β. For a complete discussion of the pooling process, see Abt (2005).O 

To estimate total respiratory hospital admissions associated with changes in ambient ozone 

concentrations for adults over 65, we first estimated the change in hospital admissions for 

each of the different effects categories that each study provided for each city. These cities 

included Minneapolis, Detroit, Tacoma and New Haven. To estimate total respiratory 

hospital admissions for Detroit, we added the pneumonia and COPD estimates, based on the 

effect estimates in the Schwartz study (1994). Similarly, we summed the estimated hospital 

admissions based on the effect estimates the Moolgavkar study reported for Minneapolis 

(Moolgavkar et al., 1997). To estimate total respiratory hospital admissions for Minneapolis 

using the Schwartz study (1994), we simply estimated pneumonia hospital admissions based 

on the effect estimate. Making this assumption that pneumonia admissions represent the total 

N A credible interval is a posterior probability interval used in Bayesian statistics, which is similar to a 

confidence interval used in frequentist statistics. 

O Abt Associates, Incorporated. Environmental Benefits Mapping and Analysis Program, Technical Appendices. 

May 2005. pp. I-3 

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Cost-Benefit Analysis 

impact of ozone on hospital admissions in this city will give some weight to the possibility 

that there is no relationship between ozone and COPD, reflecting the equivocal evidence 

represented by the different studies. We then used a fixed-effects pooling procedure to 

combine the two total respiratory hospital admission estimates for Minneapolis. Finally, we 

used random effects pooling to combine the results for Minneapolis and Detroit with results 

from studies in Tacoma and New Haven from Schwartz (1995). As noted above, this pooling 

approach incorporates both the precision of the individual effect estimates and between-study 

variability characterizing differences across study locations. 

8.4.2.4 Asthma-Related Emergency Room Visits Effect Estimates 

We used three studies as the source of the concentration-response functions we used to 

estimate the effects of ozone exposure on asthma-related emergency room (ER) visits: Peel et 

al. (2005); Wilson et al. (2005); and Jaffe et al. (2003). We estimated the change in ER visits 

using the effect estimate(s) from each study and then pooled the results using the random 

effects pooling technique (see Abt, 2005). The study by Jaffe et al. (2003) examined the 

relationship between ER visits and air pollution for populations aged five to 34 in the Ohio 

cities of Cleveland, Columbus and Cincinnati from 1991 through 1996. In single-pollutant 

Poisson regression models, ozone was linked to asthma visits. We use the pooled estimate 

across all three cities as reported in the study. The Peel et al. study (2005) estimated asthmarelated ER visits for all ages in Atlanta, using air quality data from 1993 to 2000. Using 

Poisson generalized estimating equations, the authors found a marginal association between 

the maximum daily 8-hour average ozone level and ER visits for asthma over a 3-day moving 

average (lags of 0, 1, and 2 days) in a single pollutant model. Wilson et al. (2005) examined 

the relationship between ER visits for respiratory illnesses and asthma and air pollution for all 

people residing in Portland, Maine from 1998-2000 and Manchester, New Hampshire from 

1996-2000. For all models used in the analysis, the authors restricted the ozone data 

incorporated into the model to the months ozone levels are usually measured, the springsummer months (April through September). Using the generalized additive model, Wilson et 

al. (2005) found a significant association between the maximum daily 8-hour average ozone 

level and ER visits for asthma in Portland, but found no significant association for 

Manchester. Similar to the approach used to generate effect estimates for hospital 

admissions, we used random effects pooling to combine the results across the individual study 

estimates for ER visits for asthma. The Peel et al. (2005) and Wilson et al. (2005) Manchester 

estimates were not significant at the 95 percent level, and thus, the confidence interval for the 

pooled incidence estimate based on these studies includes negative values. This is an artifact 

of the statistical power of the studies, and the negative values in the tails of the estimated 

effect distributions do not represent improvements in health as ozone concentrations are 

increased. Instead these should be viewed as a measure of uncertainty due to limitations in 

the statistical power of the study. Note that we included both hospital admissions and ER 

visits as separate endpoints associated with ozone exposure, because our estimates of hospital 

admission costs do not include the costs of ER visits, and because most asthma ER visits do 

not result in a hospital admission. 

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Final Regulatory Impact Analysis 

8.4.2.5 Minor Restricted Activity Days Effects Estimate 

Minor restricted activity days (MRADs) occur when individuals reduce most usual 

daily activities and replace them with less-strenuous activities or rest, but do not miss work or 

school. We estimated the effect of ozone exposure on MRADs using a concentrationresponse function derived from Ostro and Rothschild (1989). These researchers estimated 

the impact of ozone and PM2.5 on MRAD incidence in a national sample of the adult working 

population (ages 18 to 65) living in metropolitan areas. We developed separate coefficients 

for each year of the Ostro and Rothschild analysis (1976-1981), which we then combined for 

use in EPA’s analysis. The effect estimate used in the impact function is a weighted average 

of the coefficients in Ostro and Rothschild (1989, Table 4), using the inverse of the variance 

as the weight. 

8.4.2.6 School Absences Effect Estimate 

Children may be absent from school due to respiratory or other acute diseases caused, 

or aggravated by, exposure to air pollution. Several studies have found a significant 

association between ozone levels and school absence rates. We use two studies (Gilliland et 

al., 2001; Chen et al., 2000) to estimate changes in school absences resulting from changes in 

ozone levels. The Gilliland et al. study estimated the incidence of new periods of absence, 

while the Chen et al. study examined daily absence rates. We converted the Gilliland et al. 

estimate to days of absence by multiplying the absence periods by the average duration of an 

absence. We estimated 1.6 days as the average duration of a school absence, the result of 

dividing the average daily school absence rate from Chen et al. (2000) and Ransom and Pope 

(1992) by the episodic absence duration from Gilliland et al. (2001). Thus, each Gilliland et 

al. period of absence is converted into 1.6 absence days. 

Following recent advice from the National Research Council (2002), we calculated 

reductions in school absences for the full population of school age children, ages five to 17. 

This is consistent with recent peer-reviewed literature on estimating the impact of ozone 

exposure on school absences (Hall et al. 2003). We estimated the change in school absences 

using both Chen et al. (2000) and Gilliland et al. (2001) and then, similar to hospital 

admissions and ER visits, pooled the results using the random effects pooling procedure. 

8.4.2.7 Worker Productivity 

To monetize benefits associated with increased worker productivity resulting from 

improved ozone air quality, we used information reported in Crocker and Horst (1981). 

Crocker and Horst examined the impacts of ozone exposure on the productivity of outdoor 

citrus workers. The study measured productivity impacts. Worker productivity is measuring 

the value of the loss in productivity for a worker who is at work on a particular day, but due to 

ozone, cannot work as hard. It only applies to outdoor workers, like fruit and vegetable 

pickers, or construction workers. Here, productivity impacts are measured as the change in 

income associated with a change in ozone exposure, given as the elasticity of income with 

respect to ozone concentration. The reported elasticity translates a ten percent reduction in 

ozone to a 1.4 percent increase in income. Given the national median daily income for 

8-19 
Cost-Benefit Analysis 

outdoor workers engaged in strenuous activity reported by the U.S. Census Bureau (2002), 

$68 per day (2000$), a ten percent reduction in ozone yields about $0.97 in increased daily 

wages. We adjust the national median daily income estimate to reflect regional variations in 

income using a factor based on the ratio of county median household income to national 

median household income. No information was available for quantifying the uncertainty 

associated with the central valuation estimate. Therefore, no uncertainty analysis was 

conducted for this endpoint. 

8.4.2.8 Unquantified Effects 

8.4.2.8.1 Direct Ozone Effects on Vegetation 

The Ozone Criteria Document notes that “current ambient concentrations in many 

areas of the country are sufficient to impair growth of numerous common and economically 

valuable plant and tree species.” (U.S. EPA, 2006, page 9-1). Changes in ground-level ozone 

resulting from the implementation of alternative ozone standards are expected to affect crop 

and forest yields throughout the affected area. Recent scientific studies have also found the 

ozone negatively impacts the quality or nutritive value of crops (U.S. EPA, 2006, page 9-16). 

Well-developed techniques exist to provide monetary estimates of these benefits to 

agricultural producers and to consumers. These techniques use models of planting decisions, 

yield response functions, and the supply of and demand for agricultural products. The 

resulting welfare measures are based on predicted changes in market prices and production 

costs. Models also exist to measure benefits to silvicultural producers and consumers. 

However, these models have not been adapted for use in analyzing ozone-related forest 

impacts. Because of resource limitations, we are unable to provide agricultural or benefits 

estimates for the final rule. 

An additional welfare benefit expected to accrue as a result of reductions in ambient 

ozone concentrations in the United States is the economic value the public receives from 

reduced aesthetic injury to forests. There is sufficient scientific information available to 

reliably establish that ambient ozone levels cause visible injury to foliage and impair the 

growth of some sensitive plant species (U.S. EPA, 2006, page 9-19). However, present 

analytic tools and resources preclude EPA from quantifying the benefits of improved forest 

aesthetics. 

Urban ornamentals (floriculture and nursery crops) represent an additional vegetation 

category likely to experience some degree of negative effects associated with exposure to 

ambient ozone levels and likely to affect large economic sectors. In the absence of adequate 

exposure-response functions and economic damage functions for the potential range of effects 

relevant to these types of vegetation, no direct quantitative economic benefits analysis has 

been conducted. The farm production value of ornamental crops was estimated at over $14 

billion in 2003 (USDA, 2004). This is therefore a potentially important welfare effects 

category. However, information and valuation methods are not available to allow for 

8-20 
Final Regulatory Impact Analysis 

plausible estimates of the percentage of these expenditures that may be related to impacts 

associated with ozone exposure. 

8.4.2.8.2 Nitrogen Deposition 

Deposition to Estuarine and Coastal Waters 

Excess nutrient loads, especially of nitrogen, cause a variety of adverse consequences 

to the health of estuarine and coastal waters. These effects include toxic and/or noxious algal 

blooms such as brown and red tides, low (hypoxic) or zero (anoxic) concentrations of 

dissolved oxygen in bottom waters, the loss of submerged aquatic vegetation due to the lightfiltering effect of thick algal mats, and fundamental shifts in phytoplankton community 

structure (Bricker et al., 1999). A recent study found that for the period 1990-2002, 

atmospheric deposition accounted for 17 percent of nitrate loadings in the Gulf of Mexico, 

where severe hypoxic zones have been existed over the last two decades (Booth and 

Campbell, 2007)P

. 

Reductions in atmospheric deposition of NOx are expected to reduce the adverse 

impacts associated with nitrogen deposition to estuarine and coastal waters. However, direct 

functions relating changes in nitrogen loadings to changes in estuarine benefits are not 

available. The preferred WTP-based measure of benefits depends on the availability of these 

functions and on estimates of the value of environmental responses. Because neither 

appropriate functions nor sufficient information to estimate the marginal value of changes in 

water quality exist at present, calculation of a WTP measure is not possible. 

Deposition to Agricultural and Forested Land 

Implementation strategies for alternative standards which reduce NOX emissions, will 

also reduce nitrogen deposition on agricultural land and forests. There is some evidence that 

nitrogen deposition may have positive effects on agricultural output through passive 

fertilization. Holding all other factors constant, farmers’ use of purchased fertilizers or 

manure may increase as deposited nitrogen is reduced. Estimates of the potential value of this 

possible increase in the use of purchased fertilizers are not available, but it is likely that the 

overall value is very small relative to other health and welfare effects. The share of nitrogen 

requirements provided by this deposition is small, and the marginal cost of providing this 

nitrogen from alternative sources is quite low. In some areas, agricultural lands suffer from 

nitrogen over-saturation due to an abundance of on-farm nitrogen production, primarily from 

animal manure. In these areas, reductions in atmospheric deposition of nitrogen from PM 

represent additional agricultural benefits. 

P

 Booth, M.S., and C. Campbell. 2007. Spring Nitrate Flux in the Mississippi River Basin: A Landscape Model 

with Conservation Applications. Environ. Sci. Technol.; 2007; ASAP Web Release Date: 20-Jun-2007; (Article) 

DOI: 10.1021/es070179e 

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Cost-Benefit Analysis 

Information on the effects of changes in passive nitrogen deposition on forests and 

other terrestrial ecosystems is very limited. The multiplicity of factors affecting forests, 

including other potential stressors such as ozone, and limiting factors such as moisture and 

other nutrients, confound assessments of marginal changes in any one stressor or nutrient in 

forest ecosystems. However, reductions in deposition of nitrogen could have negative effects 

on forest and vegetation growth in ecosystems where nitrogen is a limiting factor (US EPA, 

1993). Moreover, any positive effect that nitrogen deposition has on forest productivity would 

enhance the level of carbon dioxide sequestration as well.Q,R,S 

On the other hand, there is evidence that forest ecosystems in some areas of the United 

States (such as the western U.S.) are nitrogen saturated (US EPA, 1993). Once saturation is 

reached, adverse effects of additional nitrogen begin to occur such as soil acidification which 

can lead to leaching of nutrients needed for plant growth and mobilization of harmful 

elements such as aluminum. Increased soil acidification is also linked to higher amounts of 

acidic runoff to streams and lakes and leaching of harmful elements into aquatic ecosystems. 

8.4.2.8.3 Ultraviolet Radiation 

Atmospheric ozone absorbs a harmful band of ultraviolet radiation from the sun called 

UV-B, providing a protective shield to the Earth's surface. The majority of this protection 

occurs in the stratosphere where 90% of atmospheric ozone is located. The remaining 10% of 

the Earth's ozone is present at ground level (referred to as tropospheric ozone) (NAS, 1991; 

NASA). Only a portion of the tropospheric fraction of UV-B shielding is from anthropogenic 

sources (e.g., power plants, byproducts of combustion). The portion of ground level ozone 

associated with anthropogenic sources varies by locality and over time. Even so, it is 

reasonable to assume that reductions in ground level ozone would lead to increases in the 

same health effects linked to in UV-B exposures. These effects include fatal and nonfatal 

melanoma and non-melanoma skin cancers and cataracts. The values of $15,000 per case for 

non-fatal melanoma skin cancer, $5,000 per case for non-fatal non-melanoma skin cancer, and 

$15,000 per case of cataracts have been used in analyses of stratospheric ozone depletion 

(U.S. EPA, 1999). Fatal cancers are valued using the standard VSL estimate, which for 2020 

is $6.6 million (1999$). UV-B has also been linked to ecological effects including damage to 

crops and forest. For a more complete listing of quantified and unquantified UV-B radiation 

effects, see Table G-4 and G-7 in the Benefits and Costs of the Clean Air Act, 1990-2010 

(U.S. EPA, 1999. UV-B related health effects are also discussed in the context of 

stratospheric ozone in a 2006 report by ICF Consulting, prepared for the U.S. EPA. 

Q Peter M. Vitousek et. al., “Human Alteration of the Global Nitrogen Cycle: Causes and Consequences” Issues 

in Ecology No. 1 (Spring) 1997. 

R

 Knute J. Nadelhoffer et. al., “Nitrogen deposition makes a minor contribution to carbon sequestration in 

temperate forests” Nature 398, 145-148 (11 March 1999) 

S

 Martin Köchy and Scott D. Wilson, “Nitrogen deposition and forest expansion in the northern Great Plains 

Journal of Ecology Journal of Ecology 89 (5), 807–817 

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Final Regulatory Impact Analysis 

There are many factors that influence UV-B radiation penetration to the earth’s 

surface, including latitude, altitude, cloud cover, surface albedo, PM concentration and 

composition, and gas phase pollution. Of these, only latitude and altitude can be defined with 

small uncertainty in any effort to assess the changes in UV-B flux that may be attributable to 

any changes in tropospheric ozone as a result of any revision to the ozone NAAQS. Such an 

assessment of UV-B related health effects would also need to take into account human habits, 

such as outdoor activities (including age- and occupation-related exposure patterns), dress and 

skin care to adequately estimate UV-B exposure levels. However, little is known about the 

impact of these factors on individual exposure to UV-B. 

Moreover, detailed information does not exist regarding other factors that are relevant 

to assessing changes in disease incidence, including: type (e.g., peak or cumulative) and time 

period (e.g., childhood, lifetime, current) of exposures related to various adverse health 

outcomes (e.g., damage to the skin, including skin cancer; damage to the eye, such as 

cataracts; and immune system suppression); wavelength dependency of biological responses; 

and interindividual variability in UV-B resistance to such health outcomes. Beyond these well 

recognized adverse health effects associated with various wavelengths of UV radiation, the 

Criteria Document (section 10.2.3.6) also discusses protective effects of UV-B radiation. 

Recent reports indicate the necessity of UV-B in producing vitamin D, and that vitamin D 

deficiency can cause metabolic bone disease among children and adults, and may also 

increase the risk of many common chronic diseases (e.g., type I diabetes and rheumatoid 

arthritis) as well as the risk of various types of cancers. Thus, the Criteria Document 

concludes that any assessment that attempts to quantify the consequences of increased UV-B 

exposure on humans due to reduced ground-level ozone must include consideration of both 

negative and positive effects. However, as with other impacts of UVB on human health, this 

beneficial effect of UVB radiation has not previously been studied in sufficient detail. 

The Agency is currently evaluating the feasibility of estimating the effects of 

increased UVB exposures resulting from reductions in tropospheric ozone. Please refer to the 

final Ozone NAAQS RIA for a sensitivity analysis that explores the quantification of UV-Brelated health effects.51 

8.4.2.8.4 Climate Implications of Tropospheric Ozone 

Although climate and air quality are generally treated as separate issues, they are 

closely coupled through atmospheric processes. Ozone, itself, is a major greenhouse gas and 

climate directly influences ambient concentrations of ozone. 

The concentration of tropospheric ozone has increased substantially since the preindustrial era and has contributed to warming. Tropospheric ozone is (after CO2 and CH4) 

the third most important contributor to greenhouse gas warming. The National Academy of 

Sciences recently statedT

 that regulations targeting ozone precursors would have combined 

T

 National Academy of Sciences, “Radiative Forcing of Climate Change: Expanding the Concept and Addressing 

Uncertainties,” October 2005. 

8-23 
Cost-Benefit Analysis 

benefits for public health and climate. As noted in the OAQPS Staff Paper, the overall body 

of scientific evidence suggests that high concentrations of ozone on a regional scale could 

have a discernible influence on climate. However, the Staff Paper concludes that insufficient 

information is available at this time to quantitatively inform the secondary NAAQS process 

with regard to this aspect of the ozone-climate interaction. 

Climate change can affect tropospheric ozone by modifying emissions of precursors, 

chemistry, transport and removal.U Climate change affects the sources of ozone precursors 

through physical response (lightning), biological response (soils, vegetation, and biomass 

burning) and human response (energy generation, land use, and agriculture). Increases in 

regional ozone pollution are expected due to higher temperatures and weaker circulation. 

Simulations with global climate models for the 21st century indicate a decrease in the lifetime 

of tropospheric ozone due to increasing water vapor which could decrease global background 

ozone concentrations. 

The Intergovernmental Panel on Climate Change (IPCC) recently released a reportV 

which projects, with “virtual certainty,” declining air quality in cities due to warmer and 

fewer cold days and nights and/or warmer/more frequent hot days and nights over most land 

areas. The report states that projected climate change-related exposures are likely to affect the 

health status of millions of people, in part, due to higher concentrations of ground level ozone 

related to climate change. 

The IPCC also reportsW that the current generation of tropospheric ozone models is 

generally successful in describing the principal features of the present-day global ozone 

distribution. However, there is much less confidence in the ability to reproduce the changes 

in ozone associated with perturbations of emissions or climate. There are major discrepancies 

with observed long-term trends in ozone concentrations over the 20th century, including after 

1970 when the reliability of observed ozone trends is high. Resolving these discrepancies is 

needed to establish confidence in the models. 

UDenman, K.L., G. Brasseur, A. Chidthaisong, P. Ciais, P.M. Cox, R.E. Dickinson, D. Hauglustaine, C. Heinze, 

E. Holland, D. Jacob, U. Lohmann, S Ramachandran, P.L. da Silva Dias, S.C. Wofsy and X. Zhang, 2007: 

Couplings Between Changes in the Climate System and Biogeochemistry. In: Climate Change 2007: The 

Physical Science Basis. Contribution of Working Group I to the Fourth Assessment 

Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. 

Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United 

Kingdom and New York, NY, USA. 

V IPCC, Climate Change 2007: Climate Change Impacts, Adaptation and Vulnerability, 

Summary for Policymakers 

W Denman, et al, 2007: Couplings Between Changes in the Climate System and Biogeochemistry. In: Climate 

Change 2007: The Physical Science Basis. 

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Final Regulatory Impact Analysis 

The EPA is currently leading a research effort with the goal of identifying changes in 

regional US air quality that may occur in a future (2050) climate, focusing on fine particles 

and ozone. The research builds first on an assessment of changes in US air quality due to 

climate change, which includes direct meteorological impacts on atmospheric chemistry and 

transport and the effect of temperature changes on air pollution emissions. Further research 

will result in an assessment that adds the emission impacts from technology, land use, 

demographic changes, and air quality regulations to construct plausible scenarios of US air 

quality 50 years into the future. As noted in the Staff Paper, results from these efforts are 

expected to be available for consideration in the next review of the ozone NAAQS. 

8.4.3 Baseline Incidence Rates 

Epidemiological studies of the association between pollution levels and adverse health 

effects generally provide a direct estimate of the relationship of air quality changes to the 

relative risk of a health effect, rather than estimating the absolute number of avoided cases. 

For example, a typical result might be that a 100 ppb decrease in daily ozone levels might, in 

turn, decrease hospital admissions by 3 percent. The baseline incidence of the health effect is 

necessary to convert this relative change into a number of cases. A baseline incidence rate is 

the estimate of the number of cases of the health effect per year in the assessment location, as 

it corresponds to baseline pollutant levels in that location. To derive the total baseline 

incidence per year, this rate must be multiplied by the corresponding population number. For 

example, if the baseline incidence rate is the number of cases per year per 100,000 people, 

that number must be multiplied by the number of 100,000s in the population. 

Table 8.4-3 summarizes the sources of baseline incidence rates and provides average 

incidence rates for the endpoints included in the analysis. For both baseline incidence and 

prevalence data, we used age-specific rates where available. We applied concentrationresponse functions to individual age groups and then summed over the relevant age range to 

provide an estimate of total population benefits. In most cases, we used a single national 

incidence rate, due to a lack of more spatially disaggregated data. Whenever possible, the 

national rates used are national averages, because these data are most applicable to a national 

assessment of benefits. For some studies, however, the only available incidence information 

comes from the studies themselves; in these cases, incidence in the study population is 

assumed to represent typical incidence at the national level. Regional incidence rates are 

available for hospital admissions, and county-level data are available for premature mortality. 

We have projected mortality rates such that future mortality rates are consistent with our 

projections of population growth (Abt Associates, 2005). 

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Cost-Benefit Analysis 

Table 8.4-3. National Average Baseline Incidence Ratesa 

Endpoint Source Notes Rate per 100 people per yeard by Age Group 

<18 18-24 25-34 35-44 45-54 55-64 65+ 

Mortality CDC Compressed Mortality File, 

accessed through CDC Wonder 

(1996-1998) 

nonaccidental 0.025 0.022 0.057 0.150 0.383 1.006 4.937 

Respiratory 

Hospital 

Admissions. 

1999 NHDS public use data filesb incidence 0.043 0.084 0.206 0.678 1.926 4.389 11.62 

9 

Asthma ER visits 2000 NHAMCS public use data 

filesc

; 1999 NHDS public use data 

filesb 

incidence 1.011 1.087 0.751 0.438 0.352 0.425 0.232 

Minor Restricted 

Activity Days 

(MRADs) 

Ostro and Rothschild 

(1989, p. 243) 

incidence – 780 780 780 780 780 – 

School Loss 

Days 

National Center for Education 

Statistics (1996) and 1996 HIS 

(Adams et al., 1999, Table 47); 

estimate of 180 school days per 

year 

all-cause 990.0 – – – – – – 

Endpoint Source Notes Rate per 100 people per year 

Asthma 

Exacerbations 

Ostro et al. (2001) Incidence (and 

prevalence) among 

asthmatic AfricanAmerican children 

Daily wheeze 

Daily cough 

Daily dyspnea 

0.076 (0.173) 

0.067 (0.145) 

0.037 (0.074) 

Vedal et al. (1998) Incidence among 

asthmatic children 

Daily wheeze 

Daily cough 

Daily dyspnea 

0.038 

0.086 

0.045 

a

 The following abbreviations are used to describe the national surveys conducted by the National Center for 

Health Statistics: HIS refers to the National Health Interview Survey; NHDS - National Hospital Discharge Survey; 

NHAMCS - National Hospital Ambulatory Medical Care Survey. b

 See ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Datasets/NHDS/ c

 See ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Datasets/NHAMCS/ d

 All of the rates reported here are population-weighted incidence rates per 100 people per year. Additional details 

on the incidence and prevalence rates, as well as the sources for these rates are available upon request. 

8.5 Economic Values for Health Outcomes 

Reductions in ambient concentrations of air pollution generally lower the risk of future 

adverse health effects for a large population. Therefore, the appropriate economic measure is 

willingness-to-pay (WTP) for changes in risk of a health effect rather than WTP for a health 

effect that would occur with certainty (Freeman, 1993). Epidemiological studies generally 

provide estimates of the relative risks of a particular health effect that is avoided because of a 

reduction in air pollution. We converted those to units of avoided statistical incidence for ease 

of presentation. We calculated the value of avoided statistical incidences by dividing 

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Final Regulatory Impact Analysis 

individual WTP for a risk reduction by the related observed change in risk. For example, 

suppose a pollution-reduction regulation is able to reduce the risk of premature mortality from 

2 in 10,000 to 1 in 10,000 (a reduction of 1 in 10,000). If individual WTP for this risk 

reduction is $100, then the WTP for an avoided statistical premature death is $1 million 

($100/0.0001 change in risk). 

WTP estimates generally are not available for some health effects, such as hospital 

admissions. In these cases, we used the cost of treating or mitigating the effect as a primary 

estimate. These cost-of-illness (COI) estimates generally understate the true value of 

reducing the risk of a health effect, because they reflect the direct expenditures related to 

treatment, but not the value of avoided pain and suffering (Harrington and Portney, 1987; 

Berger, 1987). We provide unit values for health endpoints (along with information on the 

distribution of the unit value) in Table 8.5-1. All values are in constant year 2000 dollars, 

adjusted for growth in real income out to 2020 using projections provided by Standard and 

Poor’s. Economic theory argues that WTP for most goods (such as environmental protection) 

will increase if real income increases. Many of the valuation studies used in this analysis 

were conducted in the late 1980s and early 1990s. Because real income has grown since the 

studies were conducted, people’s willingness to pay for reductions in the risk of premature 

death and disease likely has grown as well. We did not adjust cost of illness-based values 

because they are based on current costs. Similarly, we did not adjust the value of school 

absences, because that value is based on current wage rates. Table 8.5-1 presents the values 

for individual endpoints adjusted to year 2020 income levels. The discussion below provides 

additional details on ozone related endpoints not previously included in the proposal for this 

rule. For details on valuation estimates for PM-related endpoints, see the 2006 PM NAAQS 

RIA and the proposed Small SI and Marine SI RIA. 

8.5.1 Mortality Valuation 

To estimate the monetary benefit of reducing the risk of premature death, we used the 

“value of statistical lives” saved (VSL) approach, which is a summary measure for the value 

of small changes in mortality risk for a large number of people. The VSL approach applies 

information from several published value-of-life studies to determine a reasonable monetary 

value of preventing premature mortality. The mean value of avoiding one statistical death is 

estimated to be roughly $6.2 million at 1990 income levels (2005$), and $7.5 million at 2020 

income levels. This represents an intermediate value from a variety of estimates in the 

economics literature (see the 2006 PM NAAQS RIA for more details on the calculation of 

VSL). 

8.5.2 Hospital Admissions Valuation 

In the absence of estimates of societal WTP to avoid hospital visits/admissions for 

specific illnesses, estimates of total cost of illness (total medical costs plus the value of lost 

productivity) typically are used as conservative, or lower bound, estimates. These estimates 

are biased downward, because they do not include the willingness-to-pay value of avoiding 

pain and suffering. 

8-27 
Cost-Benefit Analysis 

The International Classification of Diseases (ICD-9, 1979) code-specific COI 

estimates used in this analysis consist of estimated hospital charges and the estimated 

opportunity cost of time spent in the hospital (based on the average length of a hospital stay 

for the illness). We based all estimates of hospital charges and length of stays on statistics 

provided by the Agency for Healthcare Research and Quality (AHRQ 2000). We estimated 

the opportunity cost of a day spent in the hospital as the value of the lost daily wage, 

regardless of whether the hospitalized individual is in the workforce. To estimate the lost 

daily wage, we divided the 1990 median weekly wage by five and inflated the result to year 

2005$ using the CPI-U “all items.” The resulting estimate is $135.59. The total cost-ofillness estimate for an ICD code-specific hospital stay lasting n days, then, was the mean 

hospital charge plus $136 C n. 

8.5.3 Asthma-Related Emergency Room Visits Valuation 

To value asthma emergency room visits, we used a simple average of two estimates 

from the health economics literature. The first estimate comes from Smith et al. (1997), who 

reported approximately 1.2 million asthma-related emergency room visits in 1987, at a total 

cost of $186.5 million (1987$). The average cost per visit that year was $155; in 2005$, that 

cost was $386.32 (using the CPI-U for medical care to adjust to 2005$). The second estimate 

comes from Stanford et al. (1999), who reported the cost of an average asthma-related 

emergency room visit at $323.23 (in 2005$), based on 1996-1997 data. A simple average of 

the two estimates yields a (rounded) unit value of $355. 

8.5.4 Minor Restricted Activity Days Valuation 

No studies are reported to have estimated WTP to avoid a minor restricted activity 

day. However, one of EPA’s contractors, IEc (1993) has derived an estimate of willingness to 

pay to avoid a minor respiratory restricted activity day, using estimates from Tolley et al. 

(1986) of WTP for avoiding a combination of coughing, throat congestion and sinusitis. The 

IEc estimate of WTP to avoid a minor respiratory restricted activity day is $38.37 (1990$), or 

about $59 (2005$). 

Although Ostro and Rothschild (1989) statistically linked ozone and minor restricted 

activity days, it is likely that most MRADs associated with ozone exposure are, in fact, minor 

respiratory restricted activity days. For the purpose of valuing this health endpoint, we used 

the estimate of mean WTP to avoid a minor respiratory restricted activity day. 

8.5.5 School Absences 

To value a school absence, we: (1) estimated the probability that if a school child 

stays home from school, a parent will have to stay home from work to care for the child; and 

(2) valued the lost productivity at the parent’s wage. To do this, we estimated the number of 

families with school-age children in which both parents work, and we valued a school-loss 

day as the probability that such a day also would result in a work-loss day. We calculated this 

value by multiplying the proportion of households with school-age children by a measure of 

8-28 
Final Regulatory Impact Analysis 

lost wages. 

We used this method in the absence of a preferable WTP method. However, this 

approach suffers from several uncertainties. First, it omits willingness to pay to avoid the 

symptoms/illness that resulted in the school absence; second, it effectively gives zero value to 

school absences that do not result in work-loss days; and third, it uses conservative 

assumptions about the wages of the parent staying home with the child. Finally, this method 

assumes that parents are unable to work from home. If this is not a valid assumption, then 

there would be no lost wages. 

For this valuation approach, we assumed that in a household with two working 

parents, the female parent will stay home with a sick child. From the Statistical Abstract of 

the United States (U.S. Census Bureau, 2001), we obtained: (1) the numbers of single, 

married and “other” (widowed, divorced or separated) working women with children; and (2) 

the rates of participation in the workforce of single, married and “other” women with 

children. From these two sets of statistics, we calculated a weighted average participation rate 

of 72.85 percent. 

Our estimate of daily lost wage (wages lost if a mother must stay at home with a sick 

child) is based on the year 2000 median weekly wage among women ages 25 and older (U.S. 

Census Bureau, 2001). This median weekly wage is $551. Dividing by five gives an estimated 

median daily wage of $103. To estimate the expected lost wages on a day when a mother has 

to stay home with a school-age child, we first estimated the probability that the mother is in 

the workforce then multiplied that estimate by the daily wage she would lose by missing a 

work day: 72.85 percent times $103, for a total loss of $75. Using the CPI-U for all items to 

adjust to 2005$, the value equals approximately $85. This valuation approach is similar to 

that used by Hall et al. (2003). 

8-29 
Co

Table 8.5-1. Unit Values Used for Economic Valuation of Health Endpoints (2005$)a 

Health Endpoint 

Central Estimate of Value Per Statistical 

Incidence 

Derivation of Estimates 

1990 Income 

Level 

2020 Income 

Levelb 

2030 Income 

Levelb 

Premature Mortality (Value of a 

Statistical Life): PM2.5- and 

Ozone-related 

$6,200,000 $7,500,000 $7,700,000 Point estimate is the mean of a normal distri

confidence interval between $1 and $10 milinterval is based on two meta-analyses of th$1 million represents the lower end of the inMrozek and Taylor (2002)52 meta-analysis a

the upper end of the interquartile range from (2003)53 meta-analysis. Adjusted for 2005$

approximately $6.2 million. The VSL reprechange in mortality risk aggregated over the 

Chronic Bronchitis (CB) $380,000 $470,000 $490,000 Point estimate is the mean of a generated dis

case of pollution-related CB. WTP to avoid CB is derived by adjusting WTP (as describ

to avoid a severe case of CB for the differeninto account the elasticity of WTP with resp

Nonfatal Myocardial Infarction 

(heart attack) 

 3% discount rate Age 0–24  Age 25–44 Age 45–54 Age 55–65 

Age 66 and over

 7% discount rate Age 0–24  Age 25–44 Age 45–54 Age 55–65 

Age 66 and over 

$82,958 $92,598 $97,754 $174,405 $82,958 $80,963 $90,705 $95,320 $163,945 $80,963 

$82,958 $92,598 $97,754 $174,405 $82,958 $80,963 $90,705 $95,320 $163,945 $80,963 

$82,958 $92,598 $97,754 $174,405 $82,958 $80,963 $90,705 $95,320 $163,945 $80,963 

Age-specific cost-of-illness values reflect lo

medical costs over a 5-year period following 

earnings estimates are based on Cropper and 

medical costs are based on simple average oal. (1998)56 and Wittels et al. (1990).57 

Lost earnings: Cropper and Krupnick (1990). Present disco

lost earnings: 

age of onset: at 3% at 7% 25-44 $10,880 $9,74045-54 $16,036 $14,357 55-65 $92,685 $82,958 

Direct medical expenses: An average of: 1. Wittels et al. (1990) ($127,296—no disco2. Russell et al. (1998), 5-year period ($27,6

$26,180 at 7% discount rate)

 (continued) 

8-30
Final Regulatory Impact Analysis 

Table 8.5-1. Unit Values Used for Economic Valuation of Health Endpoints (2005$)a (continued) 

Health Endpoint 

Central Estimate of Value Per Statistical 

Incidence 

Derivation of Estimates 

1990 Income 

Level 

2020 Income 

Levelb 

2030 Income 

Levelb 

Hospital Admissions Chronic Obstructive Pulmonary 

Disease (COPD) 

(ICD codes 490-492, 494-496) 

$15,345 $15,345 $15,345 The COI estimates (lost earnings plus direc

on ICD-9 code-level information (e.g., aveaverage length of hospital stay, and weightcategory illnesses) reported in Agency for Quality (2000)58 (www.ahrq.gov). 

Pneumonia (ICD codes 480-487) 

$18,219 $18,219 $18,219 The COI estimates (lost earnings plus direc

on ICD-9 code-level information (e.g., aveaverage length of hospital stay, and weightpneumonia category illnesses) reported in Research and Quality (2000) (www.ahrq.g

Asthma Admissions $8,226 $8,226 $8,226 The COI estimates (lost earnings plus direc

on ICD-9 code-level information (e.g., aveaverage length of hospital stay, and weightcategory illnesses) reported in Agency for Quality (2000) (www.ahrq.gov). 

All Cardiovascular (ICD codes 390-429) 

$22,800 $22,800 $22,800 The COI estimates (lost earnings plus direc

on ICD-9 code-level information (e.g., aveaverage length of hospital stay, and weightcardiovascular category illnesses) reported Research and Quality (2000) (www.ahrq.g

Emergency Room Visits for 

Asthma 

$355 $355 $355 Simple average of two unit COI values: 

(1) $386.32, from Smith et al. (1997)59 and 

(2) $323.23, from Stanford et al. (1999).60

 (continued) 

8-31
Co

Table 8.5-1. Unit Values Used for Economic Valuation of Health Endpoints (2005$)a (continued) 

Health Endpoint 

Central Estimate of Value Per Statistical 

Incidence 

Derivation of Estimates 

1990 Income 

Level 

2020 Income 

Levelb 

2030 Income 

Levelb 

Respiratory Ailments Not Requiring Hospitalization Upper Respiratory Symptoms 

(URS) 

$28 $30 $30 Combinations of the three symptoms for w

available that closely match those listed by different “symptom clusters,” each describ

dollar value was derived for each type of Uestimates of WTP (IEc, 1994)61 to avoid e

and assuming additivity of WTPs. The doaverage of the dollar values for the seven d

Lower Respiratory Symptoms 

(LRS) 

$18 $19 $19 Combinations of the four symptoms for wh

available that closely match those listed by 11 different “symptom clusters,” each descdollar value was derived for each type of Lestimates of WTP (IEc, 1994) to avoid eacand assuming additivity of WTPs. The doaverage of the dollar values for the 11 diffe

Asthma Exacerbations $47 $51 $51 Asthma exacerbations are valued at $47 pe

on the mean of average WTP estimates for definitions of a “bad asthma day,” describe(1986).62 This study surveyed asthmatics 

avoidance of a “bad asthma day,” as definepurposes of valuation, an asthma attack is to a day in which asthma is moderate or woRowe and Chestnut (1986) study. 

Acute Bronchitis $407 $434 $438 Assumes a 6-day episode, with daily value 

low and high values for related respiratory in Neumann et al. (1994).63

 (continued) 

8-32
Final Regulatory Impact Analysis 

Table 8.5-1. Unit Values Used for Economic Valuation of Health Endpoints (2005$)a (continued) 

Health Endpoint 

Central Estimate of Value Per Statistical 

Incidence 

Derivation of Estimates 

1990 Income 

Level 

2020 Income 

Levelb 

2030 Income 

Levelb 

Restricted Activity and Work/School Loss Days Work Loss Days (WLDs) Variable 

(national median = ) 

County-specific median annual wages div

of vacation) and then by 5—to get median Census, compiled by Geolytics, Inc. 

School Absence Days $85 $85 $85 Based on expected lost wages from parent 

Estimated daily lost wage (if a mother muchild) is based on the median weekly wagolder in 2000 (U.S. Census Bureau, StatisStates: 2001, Section 12: Labor Force, ETable No. 621). This median wage is $55estimated median daily wage of $103.. 

The expected loss in wages due to a day o

mother would have to stay home with her probability that the mother is in the workfwould lose if she missed a day = 72.85% 

Worker Productivity $1.07 per 

worker per 10% change in ozone per day 

$1.07 per 

worker per 10% change in ozone per day 

$1.07 per 

worker per 10% change in ozone per day 

Based on $68 ($77 in 2005$) – median da

farming, forestry and fishing – from Table the United States (“Full-Time Wage and SEarnings: 1985 to 2000") (Source of data Labor Statistics, Bulletin 2307 and Emplo

Minor Restricted Activity Days 

(MRADs) 

$58 $61 $62 Median WTP estimate to avoid one MRA

a All annual benefit estimates associated with the final standards have been inflated to reflect values in year 2005 dollars. We use the 

Indexes to adjust both WTP- and COI-based benefits estimates to 2005 dollars from 2000 dollars.65 For WTP-based estimates, we us

1.13 based on the CPI-U for “all items.” For COI-based estimates, we use an inflation factor of 1.24 based on the CPI-U for medical 

b Our analysis accounts for expected growth in real income over time. Economic theory argues that WTP for most goods (such as en

will increase if real incomes increase. Benefits are therefore adjusted by multiplying the unadjusted benefits by the appropriate adjus

for income growth over time. For a complete discussion of how these adjustment factors were derived, we refer the reader to the PM 

impact analysis. Note that similar adjustments do not exist for cost-of-illness-based unit values. For these, we apply the same unit va

future year of analysis.

8-33
Cost-Benefit Analysis 

8.6 Benefits Analysis Results for the Final Standards 

Applying the impact and valuation functions described previously in this chapter to 

the estimated changes in PM2.5 and ozone associated with the final standards results in 

estimates of the changes in health damages (e.g., premature mortalities, cases, admissions) 

and the associated monetary values for those changes. Estimates of physical health impacts 

are presented in Table 8.6-1. Monetized values for those health endpoints are presented in 

Table 8.6-2. Total aggregate monetized benefits are presented in Table 8.6-3 and Table 8.6-4 

using either a 3 percent or 7 percent discount rate, respectively. All of the monetary benefits 

are in constant-year 2005 dollars. For each endpoint presented in Tables 8.6-1 and 8.6-2, we 

provide both the mean estimate and the 90% confidence interval. 

In addition to omitted benefits categories such as air toxics and various welfare 

effects, not all known PM2.5- and ozone-related health and welfare effects could be quantified 

or monetized. The estimate of total monetized health benefits of the final standards is thus 

equal to the subset of monetized PM2.5- and ozone-related health benefits we are able to 

quantify plus the sum of the nonmonetized health and welfare benefits. We believe the total 

benefits are therefore likely underestimated. 

Total monetized benefits are dominated by benefits of mortality risk reductions. We 

provide results for particulate matter based on PM2.5 concentration response functions from 

the American Cancer Society Study (ACS), Six Cities, and Expert Elicitation to give an 

indication of the sensitivity of the benefits estimates to alternative assumptions. Following the 

recommendations of the NRC report (NRC, 2002), we identify those estimates which are 

based on empirical data, and those which are based on expert judgments. EPA recently asked 

its Science Advisory Board (SAB) to evaluate how EPA has incorporated expert elicitation 

results into the benefits analysis, and the extent to which they find the presentation in this RIA 

responsive to the NRC (2002) guidance to incorporate uncertainty into the main analysis and 

further, whether the agency should move toward presenting a central estimate with 

uncertainty bounds or continue to provide separate estimates for each of the 12 experts as well 

as from the ACS and Six Cities studies. EPA has not yet had a chance to incorporate the 

results of the SAB’s July 11, 2008 report (EPA-COUNCIL-08-002). 

Using the ACS and Six-Cities results, we estimate that the final standards would result 

in between 150 and 340 cases of avoided PM2.5-related premature deaths annually in 2020 and 

between 230 and 510 avoided premature deaths annually in 2030. When the range of expert 

opinion is used, we estimate between 80 and 840 fewer premature mortalities in 2020 and 

between 120 and 1,300 fewer premature mortalities in 2030. Note that in the case of the 

premature mortality estimates derived from the expert elicitation, we report the 90% credible 

interval, which encompasses a broader representation of uncertainty relative to the statistical 

confidence intervals provided for the effect estimates derived from the epidemiology 

literature. 

The range of ozone benefits associated with the final standards is based on risk 

reductions estimated using several sources of ozone-related mortality effect estimates. This 

8-34 
Final Regulatory Impact Analysis 

analysis presents four alternative estimates for the association based upon different functions 

reported in the scientific literature, derived from both the National Morbidity, Mortality, and 

Air Pollution Study (NMMAPS) (Bell et al., 2004) and from a series of recent meta-analyses 

(Bell et al., 2005, Ito et al., 2005, and Levy et al., 2005). This approach is not inconsistent 

with recommendations provided by the NRC in their recent report (NRC, 2008) on the 

estimation of ozone-related mortality risk reductions, “The committee recommends that the 

greatest emphasis be placed on estimates from new systematic multicity analyses that use 

national databases of air pollution and mortality, such as in the NMMAPS, without excluding 

consideration of meta-analyses of previously published studies.” 

Prior to the publication of the NRC ozone mortality report, EPA considered the 

possibility that the observed associations between ozone and mortality may not be causal in 

nature. The report, however, recommended that EPA give “little or no weight to the 

assumption that there is no causal association between ozone exposure and premature 

mortality.” Because EPA has yet to develop a coordinated response to the NRC report’s 

findings and recommendations, we have retained the approach to estimating ozone-related 

premature mortality used in RIA for the final Ozone NAAQS. EPA will specifically address 

the report's findings and recommendations in future rulemakings. 

For ozone-related premature mortality, we estimate a range of between 46 to 210 

fewer premature mortalities as a result of the final rule in 2020 and between 77 to 350 in 

2030, assuming that there is a causal relationship between ozone exposure and mortality. The 

increase in annual benefits from 2020 to 2030 reflects additional emission reductions from the 

final standards, as well as increases in total population and the average age (and thus baseline 

mortality risk) of the population. 

Our estimate of total monetized benefits in 2020 for the final standards, using the ACS 

and Six-Cities PM mortality studies and the range of ozone mortality assumptions, is between 

$1.2 billion and $4.0 billion, assuming a 3 percent discount rate, or between $1.1 billion and 

$3.8 billion, assuming a 7 percent discount rate. In 2030, we estimate the monetized benefits 

to be between $1.8 billion and $6.4 billion, assuming a 3 percent discount rate, or between 

$1.6 billion and $6.1 billion, assuming a 7 percent discount rate. The monetized benefit 

associated with reductions in the risk of both ozone- and PM2.5-related premature mortality 

ranges between 90 to 98 percent of total monetized health benefits, in part because we are 

unable to quantify a number benefits categories (see Table 8.4-1). These unquantified 

benefits may be substantial, although their magnitude is highly uncertain. 

The next largest benefit is for reductions in chronic illness (chronic bronchitis and 

nonfatal heart attacks), although this value is more than an order of magnitude lower than for 

premature mortality. Hospital admissions for respiratory and cardiovascular causes, minor 

restricted activity days, and work loss days account for the majority of the remaining benefits. 

The remaining categories each account for a small percentage of total benefit; however, they 

represent a large number of avoided incidences affecting many individuals. A comparison of 

the incidence table to the monetary benefits table reveals that there is not always a close 

correspondence between the number of incidences avoided for a given endpoint and the 

monetary value associated with that endpoint. For example, there are over 100 times more 

8-35 
Cost-Benefit Analysis 

work loss days than PM-related premature mortalities (based on the ACS study), yet work 

loss days account for only a very small fraction of total monetized benefits. This reflects the 

fact that many of the less severe health effects, while more common, are valued at a lower 

level than the more severe health effects. Also, some effects, such as hospital admissions, are 

valued using a proxy measure of willingness-to-pay (e.g., cost-of-illness). As such, the true 

value of these effects may be higher than that reported in Table 8.6-2. 

Following these tables, we also provide a more comprehensive presentation of the 

distributions of incidence generated using the available information from empirical studies 

and expert elicitation. Tables 8.6-5 and 8.6-6 present the distributions of the reduction in 

PM2.5-related premature mortality based on the C-R distributions provided by each expert, as 

well as that from the data-derived health impact functions, based on the statistical error 

associated with the ACS study (Pope et al., 2002) and the Six-cities study (Laden et al., 2006). 

The 90% confidence interval for each separate estimate of PM-related mortality is also 

provided. 

The effect estimates of five of the twelve experts included in the elicitation panel fall 

within the empirically-derived range provided by the ACS and Six-Cities studies. One of the 

experts fall below this range and six of the experts are above this range. Although the overall 

range across experts is summarized in these tables, the full uncertainty in the estimates is 

reflected by the results for the full set of 12 experts. The twelve experts’ judgments as to the 

likely mean effect estimate are not evenly distributed across the range illustrated by arraying 

the highest and lowest expert means. 

8-36 
Final Regulatory Impact Analysis 

Table 8.6-1. Estimated Reduction in Incidence of Adverse Health Effects Related to the 

Final Standardsa

2020 2030 

Health Effect Mean Incidence Reduction 

(5th – 95th %ile) 

PM-Related Endpoints 

Premature Mortality – 

Derived from Epidemiology 

Literature 

Adult, age 30+ - ACS cohort 

study (Pope et al., 2002) 

150 

(60 - 240) 

230 

(88 – 360) 

Adult, age 25+ - Six-Cities 

study (Laden et al., 2006) 

340 

(190 – 500) 

510 

(280 – 740) 

Infant, age <1 year – 

Woodruff et al. 1997 

0 

(0 – 1) 

1 

(0 – 1) 

Premature Mortality – 

Derived from Expert 

Elicitationb 

Adult, age 25+ - Lower 

Bound (Expert K) 

81 

(0 – 380) 

120 

(0 – 580) 

Adult, age 25+ - Upper Bound 

(Expert E) 

840 

(420 – 1,300) 

1,300 

(650 – 1,900) 

Chronic bronchitis (adult, age 26 and over) 150 

(28 – 270) 

220 

(40 – 400) 

Acute myocardial infarction (adults, age 18 and older) 330 

(180 – 480) 

530 

(280 – 770) 

Hospital admissions—respiratory (all ages)c 40 

(20 – 59) 

61 

(30 – 88) 

Hospital admissions—cardiovascular (adults, age >18)d

 81 

(50 – 110) 

130 

(82 – 180) 

Emergency room visits for asthma (age 18 years and younger) 150 

(85 – 210) 

210 

(120 – 300) 

Acute bronchitis (children, age 8–12) 400 

(-14 – 810) 

580 

(-20 – 1,200) 

Lower respiratory symptoms (children, age 7–14) 2,700 

(1,300 – 4,000) 

3,800 

(1,800 – 5,800) 

Upper respiratory symptoms (asthmatic children, age 9–18) 1,900 

(610 – 3,300) 

2,800 

(880 – 4,700) 

Asthma exacerbation (asthmatic children, age 6–18) 2,400 

(270 – 7,000) 

3,500 

(380 – 10,000) 

Work loss days (adults, age 18–65) 17,000 

(15,000 – 19,000) 

23,000 

(20,000 – 26,000) 

Minor restricted-activity days (adults, age 18–65) 100,000 

(86,000 – 120,000) 

140,000 

(120,000 – 160,000) 

Ozone-Related Endpoints 

Premature Mortality, All ages 

– Derived from NMMAPS 

Bell et al., 2004 46 

(20 – 72) 

77 

(34 – 120) 

Premature Mortality, All ages 

– Derived from Meta-analyses 

Bell et al., 2005 150 

(84 – 210) 

250 

(140 – 360) 

Ito et al., 2005 200 

(140 – 270) 

340 

(230 – 450) 

Levy et al., 2005 210 

(160 – 260) 

350 

(260 - 440) 

Premature Mortality – Assumption that association between 

ozone and mortality is not causale 

0 0 

Hospital admissions- respiratory causes (children, under 2; 540 1,000 

8-37 
Cost-Benefit Analysis 

adult, 65 and older)f (170 – 900) (290 – 1,700) 

Emergency room visit for asthma (all ages) 200 

(0 – 510) 

320 

(0 - 810) 

Minor restricted activity days (adults, age 18-65) 310,000 

(160,000 – 460,000) 

450,000 

(230,000 – 670,000) 

School absence days 110,000 

(40,000 – 200,000) 

180,000 

(62,000 – 320,000) a

 Incidence is rounded to two significant digits. PM and ozone estimates represent impacts from the 

final standards nationwide. 

b

 Based on effect estimates derived from the full-scale expert elicitation assessing the uncertainty in the 

concentration-response function for PM-related premature mortality (IEc, 2006).66 The effect estimates of five 

of the twelve experts included in the elicitation panel fall within the empirically-derived range provided by the 

ACS and Six-Cities studies. One of the experts fall below this range and six of the experts are above this range. 

Although the overall range across experts is summarized in this table, the full uncertainty in the estimates is 

reflected by the results for the full set of 12 experts. The twelve experts’ judgments as to the likely mean effect 

estimate are not evenly distributed across the range illustrated by arraying the highest and lowest expert means. c

 Respiratory hospital admissions for PM include admissions for chronic obstructive pulmonary disease 

(COPD), pneumonia, and asthma. 

d

 Cardiovascular hospital admissions for PM include total cardiovascular and subcategories for 

ischemic heart disease, dysrhythmias, and heart failure. e

 A recent report published by the National Research Council (NRC, 2008) recommended that EPA 

“give little or no weight to the assumption that there is no causal association between estimated reductions in 

premature mortality and reduced ozone exposure.” 

f

 Respiratory hospital admissions for ozone include admissions for all respiratory causes and 

subcategories for COPD and pneumonia. 

8-38 
Final Regulatory Impact Analysis 

Table 8.6-2. Estimated Monetary Value in Reductions in Incidence of Health and 

Welfare Effects (in millions of 2005$)a,b

2020 2030 

PM2.5-Related Health Effect Estimated Mean Value of Reductions 

(5th and 95th %ile) 

Premature Mortality – 

Derived from 

Epidemiology 

Studiesc,d, 

Adult, age 30+ - ACS study 

(Pope et al., 2002) 

3% discount rate 

7% discount rate 

$1,000 

($240 - $2,100) 

$910 

($220 - $1,900) 

$1,600 

($370 - $3,200) 

$1,400 

($330 - $2,800) 

Adult, age 25+ - Six-cities study 

(Laden et al., 2006) 

3% discount rate 

7% discount rate 

$2,300 

($630 - $4,400) 

$2,100 

($570 - $3,900) 

$3,500 

($970 - $6,700) 

$3,200 

($870 - $6,000) 

Infant Mortality, <1 year – 

(Woodruff et al. 1997) 

3% discount rate 

7% discount rate 

$3.2 

($0.8 - $6.2) 

$2.9 

($0.8 - $5.6) 

$3.9 

($1.0 - $7.7) 

$3.5 

($0.9 - $6.9) 

Premature mortality – 

Derived from Expert 

Elicitationc,d,e 

Adult, age 25+ - Lower bound 

(Expert K) 

3% discount rate 

7% discount rate 

$540 

($0 - $2,600) 

$490 

($0 - $2,400) 

$850 

($0 - $4,100) 

$760 

($0 - $3,700) 

Adult, age 25+ - Upper bound 

(Expert E) 

3% discount rate 

7% discount rate 

$5,600 

($1,500 - $11,000) 

$5,100 

($1,400 - $10,000) 

$8,800 

($2,400 - $17,000) 

$8,000 

($2,100 - $16,000) 

Chronic bronchitis (adults, 26 and over) $70 

($5.7 - $230) 

$110 

($8.6 - $350) 

Non-fatal acute myocardial infarctions 

3% discount rate 

7% discount rate 

$34 

($10 - $72) 

$33 

($10 - $70) 

$52 

($15 - $110) 

$51 

($14 - $110) 

Hospital admissions for respiratory causes $0.8 

($0.4 - $1.2) 

$1.3 

($0.6 - $1.8) 

Hospital admissions for cardiovascular causes $2.2 

($1.3 - $2.9) 

$3.5 

($2.2 - $4.7) 

Emergency room visits for asthma $0.05 

($0.03 - $0.08) 

$0.07 

($0.04 - $0.1) 

Acute bronchitis (children, age 8–12) $0.2 

($0 - $0.4) 

$0.2 

($0 - $0.6) 

Lower respiratory symptoms (children, 7–14) $0.05 

($0.02 - $0.09) 

$0.07 

($0.03 - $0.1) 

Upper respiratory symptoms (asthma, 9–11) $0.06 $0.08 

8-39 
Cost-Benefit Analysis 

($0.02 - $0.1) ($0.02 - $0.2) 

Asthma exacerbations $0.1 

($0.01 - $0.4) 

$0.2 

($0.02 - $0.5) 

Work loss days $2.5 

($2.2 - $2.8) 

$3.4 

($3.0 - $3.8) 

Minor restricted-activity days (MRADs) $2.9 

($0.3 – $5.7) 

$4.0 

($0.4 - $7.7) 

Recreational Visibility, 86 Class I areas $17 

(na)f 

$7 

(na) 

Ozone-related Health Effect 

Premature Mortality, All 

ages – Derived from 

NMMAPS 

Bell et al., 2004 $340 

($86 - $680) 

$590 

($150 - $1,200) 

Premature Mortality, All 

ages – Derived from Metaanalyses 

Bell et al., 2005 $1,100 

($310 - $2,100) 

$1,900 

($530 - $3,600) 

Ito et al., 2005 $1,500 

($450 - $2,800) 

$2,600 

($760 - $4,700) 

Levy et al., 2005 $1,600 

($470 - $2,700) 

$2,600 

($800 - $4,700) 

Premature Mortality – Assumption that association between 

ozone and mortality is not causalf 

$0 $0 

Hospital admissions- respiratory causes (children, under 2; 

adult, 65 and older) 

$8.7 

($2.1 - $15) 

$17 

($3.8 - $31) 

Emergency room visit for asthma (all ages) $0.07 

($0 - $0.2) 

$0.1 

($0 - $0.3) 

Minor restricted activity days (adults, age 18-65) $19 

($8.5 - $31) 

$27 

($13 - $46) 

School absence days $9.7 

($3.4 - $17) 

$15 

($5.4 - $27) 

Worker Productivity $3.1 

(na)g 

$5.1 

(na)g 

a

 Monetary benefits are rounded to two significant digits for ease of presentation and computation. PM 

and ozone benefits are nationwide. 

b

 Monetary benefits adjusted to account for growth in real GDP per capita between 1990 and the 

analysis year (2020 or 2030) c

 Valuation assumes discounting over the SAB recommended 20 year segmented lag structure. Results 

reflect the use of 3 percent and 7 percent discount rates consistent with EPA and OMB guidelines for preparing 

economic analyses (EPA, 2000; OMB, 2003). 

d

 The valuation of adult premature mortality, derived either from the epidemiology literature or the 

expert elicitation, is not additive. Rather, the valuations represent a range of possible mortality benefits. e

 Based on effect estimates derived from the full-scale expert elicitation assessing the uncertainty in the 

concentration-response function for PM-related premature mortality (IEc, 2006). The effect estimates of five of 

the twelve experts included in the elicitation panel fall within the empirically-derived range provided by the ACS 

and Six-Cities studies. One of the experts fall below this range and six of the experts are above this range. 

Although the overall range across experts is summarized in this table, the full uncertainty in the estimates is 

reflected by the results for the full set of 12 experts. The twelve experts’ judgments as to the likely mean effect 

estimate are not evenly distributed across the range illustrated by arraying the highest and lowest expert means. 

f A recent report published by the National Research Council (NRC, 2008) recommended that EPA 

“give little or no weight to the assumption that there is no causal association between estimated reductions in 

premature mortality and reduced ozone exposure.” 

8-40 
Final Regulatory Impact Analysis 

g We are unable at this time to characterize the uncertainty in the estimate of benefits of worker 

productivity and improvements in visibility at Class I areas. As such, we treat these benefits as fixed and add 

them to all percentiles of the health benefits distribution. 

Table 8.6-3 Total Monetized Benefits of the Final Small SI and Marine SI Engine Rule – 

3% Discount Rate 

Total Ozone and PM Benefits (billions, 2005$) – 

PM Mortality Derived from the ACS and Six Cities Studies 

2020 2030 

Ozone 

Mortality 

Function 

Reference Mean Total 

Benefits 

Ozone 

Mortality 

Function 

Reference Mean Total 

Benefits 

NMMAPS Bell et al., 

2004 

$1.5 - $2.8 NMMAPS Bell et al., 

2004 

$2.4 - $4.3 

Bell et al., 

2005 

$2.3 - $3.6 

Meta-analysis Ito et al., 2005 $2.7 - $4.0 

Levy et al., 

2005 

$2.7 - $4.0 

Bell et al., 

2005 

$3.7 - $5.6 

Meta-analysis Ito et al., 2005 $4.4 - $6.4 

Levy et al., 

2005 

$4.4 - $6.4 

Assumption that association is 

not causala 

$1.2 - $2.5 Assumption that association is 

not causala 

$1.8 - $3.8 

Total Ozone and PM Benefits (billions, 2005$) – 

PM Mortality Derived from Expert Elicitation (Lowest and Highest Estimate) 

2020 2030 

Ozone 

Mortality 

Function 

Reference Mean Total 

Benefits 

Ozone 

Mortality 

Function 

Reference Mean Total 

Benefits 

NMMAPS Bell et al., 

2004 

$1.1 - $6.1 NMMAPS Bell et al., 

2004 

$1.7 - $9.7 

Bell et al., 

2005 

$1.8 - $6.9 

Meta-analysis Ito et al., 2005 $2.2 - $7.3 

Levy et al., 

2005 

$2.3 - $7.4 

Bell et al., 

2005 

$3.0 - $11 

Meta-analysis Ito et al., 2005 $3.7 - $12 

Levy et al., 

2005 

$3.7 - $12 

Assumption that association is 

not causala 

$0.7 - $5.8 Assumption that association is 

not causala 

$1.1 - $9.1 

a A recent report published by the National Research Council (NRC, 2008) recommended that EPA “give little or 

no weight to the assumption that there is no causal association between estimated reductions in premature 

mortality and reduced ozone exposure.” 

8-41 
Cost-Benefit Analysis 

Table 8.6-4 Total Monetized Benefits of the Final Small SI and Marine SI Engine Rule – 

7% Discount Rate 

Total Ozone and PM Benefits (billions, 2005$) – 

PM Mortality Derived from the ACS and Six Cities Studies 

2020 2030 

Ozone 

Mortality 

Function 

Reference Mean Total 

Benefits 

Ozone 

Mortality 

Function 

Reference Mean Total 

Benefits 

NMMAPS Bell et al., 

2004 

$1.4 - $2.6 NMMAPS Bell et al., 

2004 

$2.2 - $4.0 

Bell et al., 

2005 

$2.2 - $3.4 

Meta-analysis Ito et al., 2005 $2.6 - $3.7 

Levy et al., 

2005 

$2.6 - $3.8 

Bell et al., 

2005 

$3.5 - $5.3 

Meta-analysis Ito et al., 2005 $4.2 - $6.0 

Levy et al., 

2005 

$4.3 - $6.1 

Assumption that association is 

not causala 

$1.1 - $2.2 Assumption that association is 

not causala 

$1.6 - $3.4 

Total Ozone and PM Benefits (billions, 2005$) – 

PM Mortality Derived from Expert Elicitation (Lowest and Highest Estimate) 

2020 2030 

Ozone 

Mortality 

Function 

Reference Mean Total 

Benefits 

Ozone 

Mortality 

Function 

Reference Mean Total 

Benefits 

NMMAPS Bell et al., 

2004 

$1.0 - $5.6 NMMAPS Bell et al., 

2004 

$1.6 - $8.8 

Bell et al., 

2005 

$1.8 - $6.4 

Meta-analysis Ito et al., 2005 $2.2 - $6.8 

Levy et al., 

2005 

$2.2 - $6.8 

Bell et al., 

2005 

$2.9 - $10 

Meta-analysis Ito et al., 2005 $3.6 - $11 

Levy et al., 

2005 

$3.7 - $11 

Assumption that association is 

not causala 

$0.7 - $5.2 Assumption that association is 

not causala 

$1.0 - $8.2 

a A recent report published by the National Research Council (NRC, 2008) recommended that EPA “give little or 

no weight to the assumption that there is no causal association between estimated reductions in premature 

mortality and reduced ozone exposure.” 

8-42 
Final Regulatory Impact Analysis 

Table 8.6-5. Results of Application of Expert Elicitation: Annual Reductions in 

Premature Mortality in 2020 Associated with the Final Standards 

Source of Mortality 

Estimate 

2020 Primary Option 

5th Percentile Mean 95th Percentile 

Pope et al. (2002) 59 150 240 

Laden et al. (2006) 190 340 500 

Expert A 120 670 1,200 

Expert B 64 510 1,100 

Expert C 92 510 1,100 

Expert D 74 350 580 

Expert E 420 840 1,300 

Expert F 320 460 670 

Expert G 0 300 550 

Expert H 1 380 870 

Expert I 80 500 900 

Expert J 120 410 900 

Expert K 0 81 380 

Expert L 45 350 690 

Table 8.6-6. Results of Application of Expert Elicitation: Annual Reductions in 

Premature Mortality in 2030 Associated with the Final Standards 

Source of Mortality 

Estimate 

2030 Primary Option 

5th Percentile Mean 95th Percentile 

Pope et al. (2002) 88 230 360 

Laden et al. (2006) 280 510 740 

Expert A 190 1,000 1,900 

Expert B 97 780 1,700 

Expert C 140 780 1,700 

Expert D 110 540 890 

Expert E 650 1,300 1,900 

Expert F 490 700 1,000 

Expert G 0 450 840 

Expert H 2 580 1,300 

Expert I 120 770 1,400 

Expert J 190 620 1,400 

Expert K 0 120 580 

Expert L 67 530 1,100 

8-43 
Cost-Benefit Analysis 

8.7 Comparison of Costs and Benefits 

In estimating the net benefits of the final standards, the appropriate cost measure is 

‘social costs.’ Social costs represent the welfare costs of a rule to society. These costs do not 

consider transfer payments (such as taxes) that are simply redistributions of wealth. Table 

8.7-1 contains the estimates of monetized benefits and estimated social welfare costs for the 

final rule and each of the final control programs. The annual social welfare costs of all 

provisions of this final rule are described more fully in Chapter 9 of this RIA. 

The results in Table 8.7-1 suggest that the 2020 monetized benefits of the final 

standards are greater than the expected social welfare costs. Specifically, the annual benefits 

of the total program will range between $1.2 to $4.0 billion annually in 2020 using a three 

percent discount rate, or between $1.1 to $3.8 billion assuming a 7 percent discount rate, 

compared to estimated social costs of approximately $210 million in that same year. These 

benefits are expected to increase to between $1.8 and $6.4 billion annually in 2030 using a 

three percent discount rate, or between $1.6 and $6.1 billion assuming a 7 percent discount 

rate, while the social costs are estimated to be approximately $190 million. Though there are 

a number of health and environmental effects associated with the final standards that we are 

unable to quantify or monetize (see Table 8.4-1), the benefits of the final standards far 

outweigh the projected costs. When we examine the benefit-to-cost comparison for the rule 

standards separately, we also find that the benefits of the specific engine standards outweigh 

their projected costs. 

Using a conservative benefits estimate, the 2020 benefits outweigh the costs by a 

factor of 5. Using the upper end of the benefits range, the benefits could outweigh the costs 

by a factor of 19. Likewise, in 2030 benefits outweigh the costs by at least a factor of 8 and 

could be as much as a factor of 34. Thus, even taking the most conservative benefits 

assumptions, benefits of the final standards clearly outweigh the costs. 

8-44 
Final Regulatory Impact Analysis 

Table 8.7-1. Summary of Annual Benefits and Costs of the Final Standardsa 

(Millions of 2005 dollars) 

Description 2020 2030 

Estimated Social Costsb

 Small SI 

 Marine SI 

Total Social Costs 

$163 

$44 

$210 

$185 

$0.8 

$190 

Estimated Health Benefits of the Final Standardsc,d,e,f

 Small SI 

3 percent discount rate 

7 percent discount rate 

 Marine SI 

3 percent discount rate 

7 percent discount rate 

Total Benefits 

 3 percent discount rate

 7 percent discount rate 

$860 to $2,600 

$790 to $2,500 

$340 to $1,400 

$310 to $1,300 

$1,200 to $4,000 

$1,100 to $3,800 

$820 to $2,900 

$710 to $2,800 

$980 to $3,500 

$890 to $3,300 

$1,800 to $6,400 

$1,600 to $6,100 

Annual Net Benefits (Total Benefits – Total Costs) 

 3 percent discount rate

 7 percent discount rate 

$990 to $3,800 

$890 to $3,600 

$1,600 to $6,200 

$1,400 to $5,900 

a

 All estimates represent annualized benefits and costs anticipated for the years 2020 and 2030. Totals 

may not sum due to rounding.

b

 The calculation of annual costs does not require amortization of costs over time. Therefore, the 

estimates of annual cost do not include a discount rate or rate of return assumption (see Chapter 9 of the RIA). 

In Chapter 9, however, we use both a 3 percent and 7 percent social discount rate to calculate the net present 

value of total social costs consistent with EPA and OMB guidelines for preparing economic analyses (US EPA, 

2000 and OMB, 2003). c

 Total includes ozone and PM2.5 benefits. Range was developed by adding the estimate from the ozone 

premature mortality function, including an assumption that the association is not causal, to PM2.5-related 

premature mortality derived from the ACS (Pope et al., 2002) and Six Cities (Laden et al., 2006) studies. 

d Annual benefits analysis results reflect the use of a 3 percent and 7 percent discount rate in the 

valuation of premature mortality and nonfatal myocardial infarctions, consistent with EPA and OMB guidelines 

for preparing economic analyses (US EPA, 2000 and OMB, 2003). e Valuation of premature mortality based on long-term PM exposure assumes discounting over the SAB 

recommended 20-year segmented lag structure described in the Regulatory Impact Analysis for the Final Clean 

Air Interstate Rule (March, 2005). 

f Not all possible benefits or disbenefits are quantified and monetized in this analysis. Potential benefit 

categories that have not been quantified and monetized are listed in Table 8.4-1. 

8-45 
Cost-Benefit Analysis 

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Project. Rockville, MD. http://www.ahrq.gov/HCUPnet/. 

59 Smith, D.H., D.C. Malone, K.A. Lawson, L.J. Okamoto, C. Battista, and W.B. Saunders. 1997. “A National 

Estimate of the Economic Costs of Asthma.” American Journal of Respiratory and Critical Care Medicine 

156(3 Pt 1):787-793. 

60 Stanford, R., T. McLaughlin, and L.J. Okamoto. 1999. “The Cost of Asthma in the Emergency Department 

and Hospital.” American Journal of Respiratory and Critical Care Medicine 160(1):211-215. 

61 Industrial Economics, Incorporated (IEc). March 31, 1994. Memorandum to Jim DeMocker, Office of Air 

and Radiation, Office of Policy Analysis and Review, U.S. Environmental Protection Agency. 

62 Rowe, R.D., and L.G. Chestnut. 1986. “Oxidants and Asthmatics in Los Angeles: A Benefits Analysis— 

Executive Summary.” Prepared by Energy and Resource Consultants, Inc. Report to the U.S. Environmental 

Protection Agency, Office of Policy Analysis. EPA-230-09-86-018. Washington, DC. 

63 Neumann, J.E., M.T. Dickie, and R.E. Unsworth. March 31, 1994. “Linkage Between Health Effects 

Estimation and Morbidity Valuation in the Section 812 Analysis—Draft Valuation Document.” Industrial 

Economics Incorporated (IEc) Memorandum to Jim DeMocker, U.S. Environmental Protection Agency, Office 

of Air and Radiation, Office of Policy Analysis and Review. 

64 Tolley, G.S. et al. January 1986. Valuation of Reductions in Human Health Symptoms and Risks. University 

of Chicago. Final Report for the U.S. Environmental Protection Agency. 

65 Council of Economic Advisors. 2005. The Annual Report of the Council of Economic Advisors. In: 

Economic Report of the President. Table B-60. U.S. Government Printing Office: Washington, DC. 

66 Industrial Economics, Incorporated (IEc). 2006. Expanded Expert Judgment Assessment of the 

Concentration-Response Relationship Between PM2.5 Exposure and Mortality. Peer Review Draft. Prepared 

for: Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle 

Park, NC. August. 

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Appendix 8A: Sensitivity Analyses of Key Parameters in the Benefits Analysis 

The primary analysis presented in Chapter 8 is based on our current interpretation of the 

scientific and economic literature. That interpretation requires judgments regarding the best 

available data, models, and modeling methodologies and the assumptions that are most 

appropriate to adopt in the face of important uncertainties and resource limitations. The 

majority of the analytical assumptions used to develop the primary estimates of benefits have 

been used to support similar rulemakings and approved by EPA=s Science Advisory Board 

(SAB). Both EPA and the SAB recognize that data and modeling limitations as well as 

simplifying assumptions can introduce significant uncertainty into the benefit results and that 

alternative choices exist for some inputs to the analysis, such as the mortality C-R functions. 

This appendix supplements our primary estimates of benefits with a series of sensitivity 

calculations that use other sources of health effect estimates and valuation data for key 

benefits categories. The supplemental estimates examine sensitivity to both valuation issues 

and for physical effects issues. These supplemental estimates are not meant to be 

comprehensive. Rather, they reflect some of the key issues identified by EPA or commenters 

as likely to have a significant impact on total benefits. The individual adjustments in the 

tables should not simply be added together because: 1) there may be overlap among the 

alternative assumptions; and 2) the joint probability among certain sets of alternative 

assumptions may be low. 

8.A.1 Premature Mortality – Alternative Threshold Analysis 

To consider the impact of a threshold in the response function for the chronic mortality 

endpoint, we have constructed a sensitivity analysis by assigning different cutpoints below 

which changes in PM2.5 are assumed to have no impact on premature mortality. In applying 

the cutpoints, we have adjusted the mortality function slopes accordingly.A Five cutpoints 

(including the base case assumption) were included in the sensitivity analysis: (a) 14 μg/m3 

(assumes no impacts below the alternative annual NAAQS), (b) 12 μg/m3 (c) 10 μg/m3 

(reflects comments from CASAC, 2005) 1, (d) 7.5 μg/m3 (reflects recommendations from 

SAB-HES to consider estimating mortality benefits down to the lowest exposure levels 

considered in the Pope 2002 study used as the basis for modeling chronic mortality) 2 and (e) 

background or 3 μg/m3 (reflects NRC recommendation to consider effects all the way to 

background).3

 We repeat this sensitivity analysis for the RIA of the final standards, the 

results of which can be found in Table 8A-1. 

A Note that this analysis only adjusted the mortality slopes for the 10 μg/m3

, 12 μg/m3 and 14 μg/m3 cutpoints 

since the 7.5 μg/m3

 and background cutpoints were at or below the lowest measured exposure levels reported in 

the Pope et al. (2002) study for the combined exposure dataset. 

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Table 8A-1. PM-Related Mortality Benefits of the Final Standards: Cutpoint Sensitivity 

Analysis Using the ACS Study (Pope et al., 2002)a 

Certainty that Benefits 

are At Least Specified 

Value 

Level of 

Assumed 

Threshold 

PM Mortality Incidence 

2020 2030 

More Certain that 

Benefits Are at Least 

as Large 

Less Certain that 

Benefits Are at Least 

as Large 

14 μg/m3 b 6 7 

12 μg/m3 29 40 

10 μg/m3 c 150 230 

7.5 μg/m3 d 220 340 

3 μg/m3 e 250 380 

a

 Note that this table only presents the effects of a cutpoint on PM-related mortality incidence. 

b

 Alternative annual PM NAAQS. 

c Primary threshold assumption based on CASAC (2005).85 

d

 SAB-HES (2004)86 

e

 NAS (2002)87 

8.A.2 Premature Mortality - Alternative Lag Structures 

Over the last ten years, there has been a continuing discussion and evolving advice regarding 

the timing of changes in health effects following changes in ambient air pollution. It has been 

hypothesized that some reductions in premature mortality from exposure to ambient PM2.5 

will occur over short periods of time in individuals with compromised health status, but other 

effects are likely to occur among individuals who, at baseline, have reasonably good health 

that will deteriorate because of continued exposure. No animal models have yet been 

developed to quantify these cumulative effects, nor are there epidemiologic studies bearing on 

this question. 

The SAB-HES has recognized this lack of direct evidence. However, in early advice, they 

also note that “although there is substantial evidence that a portion of the mortality effect of 

PM is manifest within a short period of time, i.e., less than one year, it can be argued that, if 

no lag assumption is made, the entire mortality excess observed in the cohort studies will be 

analyzed as immediate effects, and this will result in an overestimate of the health benefits of 

improved air quality. Thus some time lag is appropriate for distributing the cumulative 

mortality effect of PM in the population,” (EPA-SAB-COUNCIL-ADV-00-001, 1999, p. 9).4 

In recent advice, the SAB-HES suggests that appropriate lag structures may be developed 

based on the distribution of cause-specific deaths within the overall all-cause estimate (EPASAB-COUNCIL-ADV-04-002, 2004). They suggest that diseases with longer progressions 

should be characterized by longer-term lag structures, while air pollution impacts occurring in 

populations with existing disease may be characterized by shorter-term lags. 

A key question is the distribution of causes of death within the relatively broad categories 

analyzed in the long-term cohort studies. Although it may be reasonable to assume the 

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Final Regulatory Impact Analysis 

cessation lag for lung cancer deaths mirrors the long latency of the disease, it is not at all clear 

what the appropriate lag structure should be for cardiopulmonary deaths, which include both 

respiratory and cardiovascular causes. Some respiratory diseases may have a long period of 

progression, while others, such as pneumonia, have a very short duration. In the case of 

cardiovascular disease, there is an important question of whether air pollution is causing the 

disease, which would imply a relatively long cessation lag, or whether air pollution is causing 

premature death in individuals with preexisting heart disease, which would imply very short 

cessation lags. 

The SAB-HES provides several recommendations for future research that could support the 

development of defensible lag structures, including using disease-specific lag models and 

constructing a segmented lag distribution to combine differential lags across causes of death 

(EPA-SAB-COUNCIL-ADV-04-002, 2004). The SAB-HES indicated support for using “a 

Weibull distribution or a simpler distributional form made up of several segments to cover the 

response mechanisms outlined above, given our lack of knowledge on the specific form of the 

distributions,” (EPA-SAB-COUNCIL-ADV-04-002, 2004, p. 24). However, they noted that 

“an important question to be resolved is what the relative magnitudes of these segments 

should be, and how many of the acute effects are assumed to be included in the cohort effect 

estimate,” (EPA-SAB-COUNCIL-ADV-04-002, 2004, p. 24-25). Since the publication of 

that report in March 2004, EPA has sought additional clarification from this committee. In its 

follow-up advice provided in December 2004, the SAB suggested that until additional 

research has been completed, EPA should assume a segmented lag structure characterized by 

30 percent of mortality reductions occurring in the first year, 50 percent occurring evenly over 

years 2 to 5 after the reduction in PM2.5, and 20 percent occurring evenly over the years 6 to 

20 after the reduction in PM2.5 (EPA-COUNCIL-LTR-05-001, 2004).5 The distribution of 

deaths over the latency period is intended to reflect the contribution of short-term exposures 

in the first year, cardiopulmonary deaths in the 2- to 5-year period, and long-term lung disease 

and lung cancer in the 6- to 20-year period. Furthermore, in their advisory letter, the SABHES recommended that EPA include sensitivity analyses on other possible lag structures. In 

this appendix, we investigate the sensitivity of premature mortality-reduction related benefits 

to alternative cessation lag structures, noting that ongoing and future research may result in 

changes to the lag structure used for the primary analysis. 

In previous advice from the SAB-HES, they recommended an analysis of 0-, 8-, and 15-year 

lags, as well as variations on the proportions of mortality allocated to each segment in the 

segmented lag structure (EPA-SAB-COUNCIL-ADV-00-001, 1999, 

(EPA-COUNCIL-LTR-05-001, 2004). The 0-year lag is representative of EPA=s assumption 

in previous RIAs. The 8- and 15-year lags are based on the study periods from the Pope et al. 

(1995)6

 and Dockery et al. (1993)7 studies, respectively.B However, neither the Pope et al. nor 

Dockery et al. studies assumed any lag structure when estimating the relative risks from PM 

exposure. In fact, the Pope et al. and Dockery et al. analyses do not support or refute the 

existence of a lag. Therefore, any lag structure applied to the avoided incidences estimated 

from either of these studies will be an assumed structure. The 8- and 15-year lags implicitly 

FF Although these studies were conducted for 8 and 15 years, respectively, the choice of the duration of the study 

by the authors was not likely due to observations of a lag in effects but is more likely due to the expense of 

conducting long-term exposure studies or the amount of satisfactory data that could be collected during this time 

period. 

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Cost-Benefit Analysis 

assume that all premature mortalities occur at the end of the study periods (i.e., at 8 and 15 

years). 

 In addition to the simple 8- and 15-year lags, we have added two additional sensitivity 

analyses examining the impact of assuming different allocations of mortality to the segmented 

lag of the type suggested by the SAB-HES. The first sensitivity analysis assumes that more of 

the mortality impact is associated with chronic lung diseases or lung cancer and less with 

acute cardiopulmonary causes. This illustrative lag structure is characterized by 20 percent of 

mortality reductions occurring in the first year, 50 percent occurring evenly over years 2 to 5 

after the reduction in PM2.5, and 30 percent occurring evenly over the years 6 to 20 after the 

reduction in PM2.5. The second sensitivity analysis assumes the 5-year distributed lag 

structure used in previous analyses, which is equivalent to a three-segment lag structure with 

50 percent in the first 2-year segment, 50 percent in the second 3-year segment, and 0 percent 

in the 6- to 20-year segment. 

The estimated impacts of alternative lag structures on the monetary benefits associated with 

reductions in PM-related premature mortality (estimated with the Pope et al. ACS impact 

function) are presented in Table 8A-2. These estimates are based on the value of statistical 

lives saved approach (i.e., $5.5 million per incidence) and are presented using both a 3 percent 

and 7 percent discount rate over the lag period. 

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 Cost-Benefit Analysis 

Table 8A-2. Sensitivity of Benefits of Premature Mortality Reductions to Alternative Lag Assumptions 

(Relative to Primary Benefits Estimates of the Final Standards) 

Avoided Incidences Value 

(ACS; Pope et al., 2002)a (million 2006$)b 

Description of Sensitivity Analysis 2020 2030 2020 2030 

Alternative Lag Structures for PM-Related Premature Mortality 

30 percent of incidences occur in 1st 

year, 50 percent in years 2 to 5, and 

Primary 20 percent in years 6 to 20

 3% Discount Rate 150 230 $1,000 $1,600

 7% Discount Rate 150 230 $900 $1,400 

None Incidences all occur in the first year 150 230 $1,100 $1,700 

8-year Incidences all occur in the 8th year 

 3% Discount Rate 150 230 $910 $1,400

 7% Discount Rate 150 230 $690 $1,100 

15-year Incidences all occur in the 15th year 

 3% Discount Rate 150 230 $740 $1,100

 7% Discount Rate 150 230 $430 $660 

20 percent of incidences occur in 1st 

Alternative year, 50 percent in years 2 to 5, and 

Segmented 30 percent in years 6 to 20

 3% Discount Rate 150 230 $1,100 $1,500

 7% Discount Rate 150 230 $1,000 $1,300 

50 percent of incidences occur in 

5-Year years 1 and 2 and 50 percent in years 

Distributed 2 to 5 

 3% Discount Rate 150 230 $980 $1,600

 7% Discount Rate 150 230 $850 $1,500 a

 Incidences rounded to two significant digits. 

b

 Dollar values rounded to two significant digits. The alternative lag structure analysis presents benefits calculated 

using both a 3 percent and 7 percent discount rate. 

The results of the scaled alternative lag sensitivity analysis demonstrate that choice of lag 

structure can have a large impact on benefits. Because of discounting of delayed benefits, the lag 

structure may have a large downward impact on monetized benefits if an extreme assumption 

that no effects occur until after 15 years is applied. However, for most reasonable distributed lag 

structures, differences in the specific shape of the lag function have relatively small impacts on 

overall benefits. 

8.A.3 Visibility Benefits in Additional Class I Areas 

The Chestnut and Rowe (1990)viii study from which the primary visibility valuation estimates are 

derived only examined WTP for visibility changes in Class I areas (national parks and wilderness 

areas) in the southeast, southwest, and California. To obtain estimates of WTP for visibility 

changes at national parks and wilderness areas in the northeast, northwest, and central regions of 

the U.S., we have to transfer WTP values from the studied regions. This introduces additional 

uncertainty into the estimates. However, we have taken steps to adjust the WTP values to 

account for the possibility that a visibility improvement in parks in one region is not necessarily 

the same environmental quality good as the same visibility improvement at parks in a different 

region. This may be due to differences in the scenic vistas at different parks, uniqueness of the 

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c 

Final Regulatory Impact Analysis 

parks, or other factors, such as public familiarity with the park resource. To take this potential 

difference into account, we adjusted the WTP being transferred by the ratio of visitor days in the 

two regions. 

Based on this benefits transfer methodology (implemented within the preference calibration 

framework discussed in Chapter 5 and Appendix I of the final PM NAAQS RIA), estimated 

additional visibility benefits in the northwest, central, and northeastern U.S. are provided in 

Table 8.A-3. 

Table 8.A-3: Monetary Benefits Associated with Improvements in Visibility in Additional Federal Class I 

Areas in 2020 and 2030 (in millions of 2006$)a 

Year Northwestb

 Centralc Northeastd Total 

2020 $3.9 $1.7 $9.2 $15 

2030 $15 $17 $12 $44 a All estimates are rounded to 2 significant digits. All rounding occurs after final summing of unrounded 

estimates. As such, totals will not sum across columns 

b Northwest Class I areas include Crater Lake, Mount Rainier, North Cascades, and Olympic national parks, and 

Alpine Lakes, Diamond Peak, Eagle Cap, Gearhart Mountain, Glacier Peak, Goat Rocks, Hells Canyon, 

Kalmiopsis, Mount Adams, Mount Hood, Mount Jefferson, Mount Washington, Mountain Lakes, Pasayten, 

Strawberry Mountain, and Three Sisters wilderness areas. 

Central Class I areas include Craters of the Moon, Glacier, Grand Teton, Theodore Roosevelt, Badlands, Wind 

Cave, and Yellowstone national parks, and Anaconda-Pintlar, Bob Marshall, Bridger, Cabinet Mountains, 

Fitzpatrick, Gates of the Mountain, Lostwood, Medicine Lake, Mission Mountain, North Absaroka, Red Rock 

Lakes, Sawtooth, Scapegoat, Selway-Bitterroot, Teton, U.L. Bend, and Washakie wilderness areas. 

d Northeast Class I areas include Acadia, Big Bend, Guadalupe Mountains, Isle Royale, 

Voyageurs, and Boundary Waters Canoe national parks, and Brigantine, Caney Creek, Great 

Gulf, Hercules-Glades, Lye Brook, Mingo, Moosehorn, Presidential Range-Dry Roosevelt 

Campobello, Seney, Upper Buffalo, and Wichita Mountains wilderness areas. 

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Appendix 8B: Health-Based Cost-Effectiveness of Reductions in Ambient O3 and PM2.5 

Associated with the Final Small SI and Recreational Marine Engine Rule 

8B.1 Introduction 

Health-based cost-effectiveness analysis (CEA) and cost-utility analysis (CUA) have been used 

to analyze numerous health interventions but have not been widely adopted as tools to analyze 

environmental policies. Analyses of environmental regulations have typically used benefit-cost 

analysis to characterize impacts on social welfare. Benefit-cost analyses allow for aggregation of 

the benefits of reducing mortality risks with other monetized benefits of reducing air pollution, 

including reduced risk of acute and chronic morbidity, and non-health benefits. One of the great 

advantages of the benefit-cost paradigm is that a wide range of quantifiable benefits can be 

compared to costs to evaluate the economic efficiency of particular actions. However, alternative 

paradigms such as CEA and CUA analyses may also provide useful insights. CEA involves 

estimation of the costs per unit of benefit (e.g., lives or life years saved). CUA is a special type 

of CEA using preference-based measures of effectiveness, such as quality-adjusted life years 

(QALYs). 

QALYs were developed to evaluate the effectiveness of individual medical treatments, and EPA 

is still evaluating the appropriate methods for CEA for environmental regulations. Agency 

concerns with the standard QALY methodology include the treatment of people with fewer years 

to live (the elderly); fairness to people with preexisting conditions that may lead to reduced life 

expectancy and reduced quality of life; and how the analysis should best account for non-health 

benefits. 

The Office of Management and Budget (OMB) recently issued Circular A-4 guidance on 

regulatory analyses, requiring federal agencies to “prepare a CEA for all major rulemakings for 

which the primary benefits are improved public health and safety to the extent that a valid 

effectiveness measure can be developed to represent expected health and safety outcomes.” 

Environmental quality improvements may have multiple health and ecological benefits, however, 

making application of CEA more difficult and less straightforward. 

The Institute of Medicine (a member institution of the National Academies of Science) 

established the Committee to Evaluate Measures of Health Benefits for Environmental, Health, 

and Safety Regulation to assess the scientific validity, ethical implications, and practical utility 

of a wide range of effectiveness measures used or proposed in CEA. This committee prepared a 

report titled “Valuing Health for Regulatory Cost-Effectiveness Analysis” which concluded that 

CEA is a useful tool for assessing regulatory interventions to promote human health and safety, 

although not sufficient for informed regulatory decisions (Miller, Robinson, and Lawrence, 

2006). They emphasized the need for additional data and methodological improvements for CEA 

analyses, and urged greater consistency in the reporting of assumptions, data elements, and 

analytic methods. They also provided a number of recommendations for the conduct of 

regulatory CEA analyses. EPA is evaluating these recommendations and will determine a 

response for upcoming analyses. 

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Final Regulatory Impact Analysis 

CEA and CUA are most useful for comparing programs that have similar goals, for example, 

alternative medical interventions or treatments that can save a life or cure a disease. They are less 

readily applicable to programs with multiple categories of benefits, such as those reducing 

ambient air pollution, because the cost-effectiveness calculation is based on the quantity of a 

single benefit category. In other words, we cannot readily convert non-health benefits, such as 

visibility improvements associated with reductions in PM2.5 or increases in worker productivity 

associated with reductions in O3, to a health metric such as life years saved. For these reasons, 

environmental economists prefer to present results in terms of monetary benefits and net 

benefits. 

However, QALY-based CUA has been widely adopted within the health economics literature 

(Neumann, 2003; Gold et al., 1996) and in the analysis of public health interventions (US FDA, 

2004). QALY-based analyses have not been as accepted in the environmental economics 

literature because of concerns about the theoretical consistency of QALYs with individual 

preferences (Hammitt, 2002), treatment of nonhuman health benefits, and a number of other 

factors (Freeman, Hammitt, and De Civita, 2002). For environmental regulations, benefit-cost 

analysis has been the preferred method of choosing among regulatory alternatives in terms of 

economic efficiency. Recently several academic analyses have proposed the use of life yearsbased benefit-cost or CEAs of air pollution regulations (Cohen, Hammitt, and Levy, 2003; Coyle 

et al., 2003; Rabl, 2003; Carrothers, Evans, and Graham, 2002). In addition, the World Health 

Organization has adopted the use of disability-adjusted life years, a variant on QALYs, to assess 

the global burden of disease due to different causes, including environmental pollution (Murray 

et al., 2002; de Hollander et al., 1999). 

One of the ongoing controversies in health impact assessment regards whether reductions in 

mortality risk should be reported and valued in terms of statistical lives saved or in terms of 

statistical life years saved. Life years saved measures differentiate among premature mortalities 

based on the remaining life expectancy of affected individuals. In general, under the life years 

approach, older individuals will gain fewer life years than younger individuals for the same 

reduction in mortality risk during a given time period, making interventions that benefit older 

individuals seem less beneficial relative to similar interventions benefiting younger individuals. 

A further complication in the debate is whether to apply quality adjustments to life years lost. 

Under this approach, individuals with preexisting health conditions would have fewer QALYs 

lost relative to healthy individuals for the same loss in life expectancy, making interventions that 

primarily benefit individuals with poor health seem less beneficial than similar interventions 

affecting primarily healthy individuals. 

In this CEA, based largely on a report prepared under contract with Abt Associates,3

 we 

calculated both life years saved and statistical lives saved. Following the methodology used in 

the CEAs for the PM and O3 NAAQS RIAs, we did not assign QALY weights to the life years 

saved – i.e., we calculated life years saved, rather than QALYs gained from mortality avoided. 

Put another way, we assumed weights of 1.0 for all life years saved. Life years saved in the 

future, however, were discounted to reflect people’s time preference (i.e., a benefit received now 

3

 The full report prepared by Abt Associates is included in the docket for the Final Small SI and Recreational Marine 

Engine Rule (EPA-HQ-OAR-2004-0008). 

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 Cost-Benefit Analysis 

is worth more than the same benefit received in the future). We used discount rates of 3 percent 

and 7 percent. 

Where possible, benefits that could not be quantified in the denominator of our cost-effectiveness 

ratios were monetized and subtracted from the cost of the regulation in the numerator. For 

example, developing QALYs for acute health effects is problematic (Bala and Zarkin, 2000). 

Therefore, rather than try to derive QALYs for the acute morbidity endpoints, we instead applied 

valuation estimates and subtracted the total monetized value of all avoided acute morbidity 

effects from the cost of the regulation, in the numerator of the cost-effectiveness ratios. The 

monetized benefits of non-health improvements, where they were estimated, were similarly 

subtracted from the cost of the regulation. Finally, although QALY estimates were derived for 

the (PM2.5-related) chronic morbidity endpoints, the medical and opportunity costs associated 

with these chronic illnesses were also subtracted from the cost of the regulation. 

PM2.5-related benefits derive not only from avoided cases of premature mortality and acute 

morbidity, but from avoided cases of chronic morbidity (chronic bronchitis and non-fatal 

myocardial infarction) as well. In the CEAs for the PM and O3 NAAQS RIAs, EPA derived 

QALYs for these two chronic morbidity endpoints (see, for example, Appendix G of the PM 

NAAQS RIA, http://www.epa.gov/ttn/ecas/regdata/RIAs/Appendix%20G--

Health%20Based%20Cost%20Effectiveness%20Analysis.pdf) and used an alternative aggregate 

effectiveness metric, Morbidity Inclusive Life Years (MILYs), to address some of the concerns 

about aggregation of life extension and quality-of-life impacts. MILYs represent the sum of life 

years gained due to reductions in premature mortality and the QALYs gained due to reductions 

in chronic morbidity. This measure may be preferred to existing QALY aggregation approaches 

because it does not devalue life extensions in individuals with preexisting illnesses that reduce 

quality of life. However, the MILY measure is still based on life years and thus still inherently 

gives more weight to interventions that reduce mortality and morbidity impacts for younger 

populations with higher remaining life expectancy. 

For this analysis, we present several metrics: lives saved, life years saved, cost of the regulation 

(net of the monetized benefits not included in the denominator) per life saved and per life year 

saved, and MILYs gained and the cost of the regulation (net of the monetized benefits not 

included in the denominator) per MILY gained. 

Note that, like future life years saved, future QALYs gained from avoided cases of chronic 

bronchitis and myocardial infarction are discounted. All costs and monetized benefits are in 

2005 dollars. 

Monte Carlo simulation methods as implemented in the Crystal BallTM software program were 

used to propagate uncertainty in several of the model parameters throughout the analysis. In 

particular, we incorporated uncertainty surrounding the coefficients in the concentrationresponse (C-R) functions, the unit values for the various morbidity endpoints included in the 

analysis, and the quality of life weights for the two chronic morbidity endpoints for which we 

developed QALYs. 

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Final Regulatory Impact Analysis 

We characterized overall uncertainty in the results with 95 percent credible or confidence 

intervals based on the Monte Carlo simulations. In addition, we examined the impacts on the cost 

effectiveness metrics of changing key parameters and/or assumptions, including 

•	 the discount rate (for the cost of the regulation in the numerator and future lives or life 

years saved and QALYs gained in the denominator); 

•	 the C-R functions for O3-related and PM2.5-related mortality ; and 

•	 the life expectancies (and therefore years of potential life lost) of individuals who die as a 

result of exposure to O3 (as explained in Section 8B.4 below). 

The methodology presented in this appendix is not intended to stand as precedent either for 

future air pollution regulations or for other EPA regulations where it may be inappropriate. It is 

intended solely to demonstrate one particular approach to estimating the cost-effectiveness of 

reductions in ambient PM2.5 and O3 in achieving improvements in public health. Reductions in 

ambient PM2.5 and O3 are estimated to have other health and environmental benefits that will not 

be reflected in this CEA. Other EPA regulations affecting other aspects of environmental quality 

and public health may require additional data and models that may preclude the development of 

similar health-based CEAs. A number of additional methodological issues must be considered 

when conducting CEAs for environmental policies, including treatment of non-health effects, 

aggregation of acute and long-term health impacts, and aggregation of life extensions and 

quality-of-life improvements in different populations. The appropriateness of health-based CEA 

should be evaluated on a case-by-case basis subject to the availability of appropriate data and 

models, among other factors. 

The remainder of this appendix provides an overview of the methods used to derive the cost 

effectiveness metrics developed for this CEA and presents the resulting metrics. Section 8B.2 

provides an overview of effectiveness measures. Section 8B.3 discusses general issues in 

constructing cost-effectiveness ratios. Section 8B.4 presents methods and results. Finally, 

Section 8B.5 presents concluding remarks. 

8B.2 Effectiveness Measures 

For the purposes of CEA, we focus the effectiveness measures on the quantifiable health impacts 

of the reductions in PM2.5 and O3 estimated to occur as a result of this rule. If the main impact of 

interest is reductions in mortality risk from air pollution, the effectiveness measures are relatively 

straightforward to develop. Mortality impacts can be characterized similar to the benefits 

analysis, by counting the number of premature deaths avoided, or can be characterized in terms 

of increases in life expectancy or life years.4

 Estimates of premature mortality have the benefit 

4

 Life expectancy is an ex ante concept, indicating the impact on an entire population’s 

expectation of the number of life years they have remaining, before knowing which individuals 

will be affected. Life expectancy thus incorporates both the probability of an effect and the 

impact of the effect if realized. Life years is an ex post concept, indicating the impact on 

individuals who actually die from exposure to air pollution. Changes in population life 

expectancy will always be substantially smaller than changes in life years per premature 

mortality avoided, although the total life years gained in the population will be the same. This is 

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 Cost-Benefit Analysis 

of being relatively simple to calculate, are consistent with the benefit-cost analysis, and do not 

impose additional assumptions on the degree of life shortening. However, some have argued that 

counts of premature deaths avoided are problematic because a gain in life of only a few months 

would be considered equivalent to a gain of many life years, and the true effectiveness of an 

intervention is the gain in life expectancy or life years (Rabl, 2003; Miller and Hurley, 2003). 

Calculations of changes in life years and life expectancy can be accomplished using standard life 

table methods (Miller and Hurley, 2003). However, the calculations require assumptions about 

the baseline mortality risks for each age cohort affected by air pollution. A general assumption 

may be that air pollution mortality risks affect the general mortality risk of the population in a 

proportional manner. However, some concerns have been raised that air pollution affects mainly 

those individuals with preexisting cardiovascular and respiratory disease, who may have reduced 

life expectancy relative to the general population. This issue is explored in more detail below. 

Air pollution is also associated with a number of significant chronic and acute morbidity 

endpoints. Failure to consider these morbidity effects may understate the cost-effectiveness of 

air pollution regulations or give too little weight to reductions in particular pollutants that have 

large morbidity impacts but no effect on life expectancy. The QALY approach explicitly 

incorporates morbidity impacts into measures of life years gained and is often used in health 

economics to assess the cost-effectiveness of medical spending programs (Gold et al., 1996). 

Using a QALY rating system, health quality ranges from 0 to 1, where 1 may represent full 

health, 0 death, and some number in between (e.g., 0.8) an impaired condition. QALYs thus 

measure morbidity as a reduction in quality of life over a period of life. QALYs assume that 

duration and quality of life are equivalent, so that 1 year spent in perfect health is equivalent to 2 

years spent with quality of life half that of perfect health. QALYs can be used to evaluate 

environmental rules under certain circumstances, although some very strong assumptions 

(detailed below) are associated with QALYs. The U.S. Public Health Service Panel on Cost 

Effectiveness in Health and Medicine recommended using QALYs when evaluating medical and 

public health programs that primarily reduce both mortality and morbidity (Gold et al., 1996). 

Although there are significant non-health benefits associated with air pollution regulations, over 

90 percent of quantifiable monetized benefits are health-related. Thus, it can be argued that 

QALYs are more applicable for these types of regulations than for other environmental policies. 

However, the value of non-health benefits should not be ignored. As discussed below, we have 

chosen to subtract the value of non-health benefits from the costs in the numerator of the costeffectiveness ratio. 

The use of QALYs is predicated on the assumptions embedded in the QALY analytical 

framework. As noted in the QALY literature, QALYs are consistent with the utility theory that 

underlies most of economics only if one imposes several restrictive assumptions, including 

independence between longevity and quality of life in the utility function, risk neutrality with 

respect to years of life (which implies that the utility function is linear), and constant 

proportionality in trade-offs between quality and quantity of life (Pliskin, Shepard, and 

Weinstein, 1980; Bleichrodt, Wakker, and Johannesson, 1996). To the extent that these 

assumptions do not represent actual preferences, the QALY approach will not provide results 

because life expectancy gains average expected life years gained over the entire population, 

while life years gained measures life years gained only for those experiencing the life extension. 

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Final Regulatory Impact Analysis 

that are consistent with a benefit-cost analysis based on the Kaldor-Hicks criterion.5 Even if the 

assumptions are reasonably consistent with reality, because QALYs represent an average 

valuation of health states rather than the sum of societal WTP, there are no guarantees that the 

option with the highest QALY per dollar of cost will satisfy the Kaldor-Hicks criterion (i.e., 

generate a potential Pareto improvement [Garber and Phelps, 1997]). 

Benefit-cost analysis based on WTP is not without potentially troubling underlying structures as 

well, incorporating ability to pay (and thus the potential for equity concerns) and the notion of 

consumer sovereignty (which emphasizes wealth effects). Table 8B-1 compares the two 

approaches across a number of parameters. For the most part, WTP allows parameters to be 

determined empirically, while the QALY approach imposes some conditions a priori. 

Table 8B-1. Comparison of QALY and WTP Approaches 

Parameter QALY WTP 

Risk aversion Risk neutral Empirically determined 

Relation of duration and quality Independent Empirically determined 

Proportionality of duration/ quality trade-off Constant Variable 

Treatment of time/age in utility function Utility linear in time Empirically determined 

Preferences Community/Individual Individual 

Source of preference data Stated Revealed and stated 

Treatment of income and prices Not explicitly considered Constrains choices 

8B.3 Construction of Cost-Effectiveness Ratios: General Issues 

8B.3.1 Dealing with Morbidity Health Effects and Non-health Effects 

Health effects from exposure to PM2.5 and O3 air pollution encompass a wide array of chronic 

and acute conditions in addition to premature mortality. EPA’s Ozone and PM Criteria 

Documents outline numerous health effects known or suspected to be linked to exposure to 

ambient ozone and PM (US EPA, 2006; US EPA, 2005; Anderson et al., 2004). Although 

chronic conditions and premature mortality generally account for the majority of monetized 

benefits, acute symptoms can affect a broad population or sensitive populations (e.g., asthmarelated emergency room visits among asthmatics). In addition, reductions in air pollution may 

result in a broad set of non-health environmental benefits, including improved worker 

productivity, improved visibility in national parks, increased agricultural and forestry yields, 

reduced acid damage to buildings, and a host of other impacts. Lives saved, life years saved, and 

5

 The Kaldor-Hicks efficiency criterion requires that the “winners” in a particular case be 

potentially able to compensate the “losers” such that total societal welfare improves. In this 

case, it is sufficient that total benefits exceed total costs of the regulation. This is also known as 

a potential Pareto improvement, because gains could be allocated such that at least one person in 

society would be better off while no one would be worse off. 

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 Cost-Benefit Analysis 

QALYs gained address only health impacts, and the OMB guidance notes that “where regulation 

may yield several different beneficial outcomes, a cost-effectiveness comparison becomes more 

difficult to interpret because there is more than one measure of effectiveness to incorporate in the 

analysis.” 

With regard to acute health impacts, Bala and Zarkin (2000) suggest that QALYs are not 

appropriate for valuing acute symptoms, because of problems with both measuring utility for 

acute health states and applying QALYs in a linear fashion to very short duration health states. 

Johnson and Lievense (2000) suggest using conjoint analysis to get healthy-utility time 

equivalences that can be compared across acute effects, but it is not clear how these can be 

combined with QALYs for chronic effects and loss of life expectancy. There is also a class of 

effects that EPA has traditionally treated as acute, such as hospital admissions, which may also 

result in a loss of quality of life for a period of time following the effect. For example, life after 

asthma hospitalization has been estimated with a utility weight of 0.93 (Bell et al., 2001; 

Kerridge, Glasziou, and Hillman, 1995). 

How should these effects be combined with QALYs for chronic and mortality effects? One 

method would be to convert the acute effects to QALYs; however, as noted above, there are 

problems with the linearity assumption (i.e., if a year with asthma symptoms is equivalent to 0.7 

year without asthma symptoms, then 1 day without asthma symptoms is equivalent to 0.0019 

QALY gained). This is troubling from both a conceptual basis and a presentation basis. An 

alternative approach is simply to treat acute health effects like non-health benefits and subtract 

the dollar value (based on WTP or COI) from compliance costs in the CEA. 

To address the issues of incorporating acute morbidity and non-health benefits, OMB suggests 

that agencies “subtract the monetary estimate of the ancillary benefits from the gross cost 

estimate to yield an estimated net cost.” As with benefit-cost analysis, any unquantified benefits 

and/or costs should be noted and an indication of how they might affect the cost-effectiveness 

ratio should be described. We followed this recommended “net cost” approach, specifically in 

netting out the benefits of health improvements other than reduced mortality and improved 

quality of life from avoided chronic illness – in particular, the monetized benefits of acute 

morbidity avoided, the medical and opportunity costs (“cost of illness”) of avoided chronic 

illness, and the benefits of non-health improvements, including increases in worker productivity 

associated with reductions in O3 and visibility improvements at national parks associated with 

reductions in PM2.5 (see Chapter 8 for more details on these benefit categories). 

8B.3.2 Should Life Years Gained Be Adjusted for Initial Health Status? 

The methods outlined below in Section 8B.4 provide estimates of the total number of life years 

gained in a population, regardless of the quality of those life years, or equivalently, assuming that 

all life years gained are in perfect health. In some CEAs (Cohen, Hammitt, and Levy, 2003; 

Coyle et al., 2003), analysts have adjusted the number of life years gained to reflect the fact that 

1) the general public is not in perfect health and thus “healthy” life years are less than total life 

years gained and 2) those affected by air pollution may be in a worse health state than the general 

population and therefore will not gain as many “healthy” life years adjusted for quality, from an 

air pollution reduction. This adjustment, which converts life years gained into QALYs, raises a 

number of serious ethical issues. Proponents of QALYs have promoted the nondiscriminatory 

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Final Regulatory Impact Analysis 

nature of QALYs in evaluating improvements in quality of life (e.g., an improvement from a 

score of 0.2 to 0.4 is equivalent to an improvement from 0.8 to 1.0), so the starting health status 

does not affect the evaluation of interventions that improve quality of life. However, for lifeextending interventions, the gains in QALYs will be directly proportional to the baseline health 

state (e.g., an individual with a 30-year life expectancy and a starting health status of 0.5 will 

gain exactly half the QALYs of an individual with the same life expectancy and a starting health 

status of 1.0 for a similar life-extending intervention). This is troubling because it imposes an 

additional penalty for those already suffering from disabling conditions. Brock (2002) notes that 

“the problem of disability discrimination represents a deep and unresolved problem for resource 

prioritization.” 

OMB (2003) has recognized this issue in their Circular A-4 guidance, which includes the 

following statement: 

When CEA is performed in specific rulemaking contexts, you should be prepared to 

make appropriate adjustments to ensure fair treatment of all segments of the 

population. Fairness is important in the choice and execution of effectiveness 

measures. For example, if QALYs are used to evaluate a lifesaving rule aimed at a 

population that happens to experience a high rate of disability (i.e., where the rule is 

not designed to affect the disability), the number of life years saved should not 

necessarily be diminished simply because the rule saves the lives of people with lifeshortening disabilities. Both analytic simplicity and fairness suggest that the 

estimated number of life years saved for the disabled population should be based on 

average life expectancy information for the relevant age cohorts. More generally, 

when numeric adjustments are made for life expectancy or quality of life, analysts 

should prefer use of population averages rather than information derived from 

subgroups dominated by a particular demographic or income group. (p. 13) 

This suggests two adjustments to the standard QALY methodology: one adjusting the relevant 

life expectancy of the affected population, and the other affecting the baseline quality of life for 

the affected population. 

In addition to the issue of fairness, potential measurement issues are specific to the air pollution 

context that might argue for caution in applying quality-of-life adjustments to life years gained 

due to air pollution reductions. A number of epidemiological and toxicological studies link 

exposure to air pollution with chronic diseases, such as CB and atherosclerosis (Abbey et al., 

1995; Schwartz, 1993; Suwa et al., 2002). If these same individuals with chronic disease caused 

by exposure to air pollution are then at increased risk of premature death from air pollution, there 

is an important dimension of “double jeopardy” involved in determining the correct baseline for 

assessing QALYs lost to air pollution (see Singer et al. [1995] for a broader discussion of the 

double-jeopardy argument). 

Analyses estimating mortality from acute exposures that ignore the effects of long-term exposure 

on morbidity may understate the health impacts of reducing air pollution. Individuals exposed to 

chronically elevated levels of air pollution may realize an increased risk of death and chronic 

disease throughout life. If at some age they contract heart (or some other chronic) disease as a 

result of the exposure to air pollution, they will from that point forward have both reduced life 

8-64 
 Cost-Benefit Analysis 

expectancy and reduced quality of life. The benefit to that individual from reducing lifetime 

exposure to air pollution would be the increase in life expectancy plus the increase in quality of 

life over the full period of increased life expectancy. If the QALY loss is determined based on 

the underlying chronic condition and life expectancy without regard to the fact that the person 

would never have been in that state without long-term exposure to elevated air pollution, then the 

person is placed in double jeopardy. In other words, air pollution has placed more people in the 

susceptible pool, but then we penalize those people in evaluating policies by treating their 

subsequent deaths as less valuable, adding insult to injury, and potentially downplaying the 

importance of life expectancy losses due to air pollution. If the risk of chronic disease and risk 

of death are considered together, then there is no conceptual problem with measuring QALYs, 

but this has not been the case in recent applications of QALYs to air pollution (Carrothers, 

Evans, and Graham, 2002; Coyle et al., 2003). The use of QALYs thus highlights the need for a 

better understanding of the relationship between chronic disease and long-term exposure and 

suggests that analyses need to consider morbidity and mortality jointly, rather than treating each 

as a separate endpoint (this is an issue for current benefit-cost approaches as well). 

Because of the fairness and measurement concerns discussed above, for the purposes of this 

analysis, we do not reduce the number of life years gained to reflect any differences in 

underlying health status that might reduce quality of life in remaining years. Thus, we maintain 

the assumption that all direct gains in life years resulting from mortality risk reductions will be 

assigned a weight of 1.0. The U.S. Public Health Service Panel on Cost Effectiveness in Health 

and Medicine recommends that “since lives saved or extended by an intervention will not be in 

perfect health, a saved life year will count as less than 1 full QALY” (Gold et al., 1996). 

However, for the purposes of this analysis, we propose an alternative to the traditional aggregate 

QALY metric that keeps separate quality adjustments to life expectancy and gains in life 

expectancy. As such, we do not make any adjustments to life years gained to reflect the less than 

perfect health of the general population. Gains in quality of life will be addressed as they accrue 

because of reductions in the incidence of chronic diseases. This is an explicit equity choice in 

the treatment of issues associated with quality-of-life adjustments for increases in life expectancy 

that still capitalizes on the ability of QALYs to capture both morbidity and mortality impacts in a 

single effectiveness measure. 

8B.3.3 Constructing Cost-Effectiveness Ratios 

Construction of cost-effectiveness ratios requires estimates of effectiveness (in this case 

measured by lives saved, life years gained, or MILYs gained) in the denominator and estimates 

of costs in the numerator. The estimate of costs in the numerator should include both the direct 

costs of the controls necessary to achieve the reduction in ambient concentrations of the air 

pollutant and the avoided costs (cost savings) associated with the reductions in morbidity (Gold 

et al., 1996). In general, because reductions in air pollution do not require direct actions by the 

affected populations, there are no specific costs to affected individuals (aside from the overall 

increases in prices that might be expected to occur as control costs are passed on by affected 

industries). Likewise, because individuals do not engage in any specific actions to realize the 

health benefit of the pollution reduction, there are no decreases in utility (as might occur from a 

medical intervention) that need to be adjusted for in the denominator. Thus, the elements of the 

numerator are direct costs of controls minus the avoided costs of illness (COI) associated with 

chronic illnesses. In addition, as noted above, to account for the value of reductions in acute 

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Final Regulatory Impact Analysis 

health impacts and non-health benefits, we netted out the monetized value of these benefits from 

the numerator to yield a “net cost” estimate. 

The denominators of the cost-effectiveness ratios we calculated are either lives saved, life years 

saved, or MILYs gained. For the MILY aggregate effectiveness measure, the denominator is 

simply the sum of life years gained from increased life expectancy and QALYs gained from the 

reductions in incidence of chronic illnesses associated with PM2.5 – chronic bronchitis (CB) and 

nonfatal acute myocardial infarction (AMI). 

8B.4 Cost Effectiveness Metrics 

In this section we describe the development of cost effectiveness metrics. To generate health 

outcomes, we used the same framework as for the benefit-cost analysis described in Chapter 8. 

For convenience, we summarize the basic methodologies here. For more details, see Chapter 8 

and the Environmental Benefits Mapping and Analysis Program (BenMAP) user’s manual 

(http://www.epa.gov/ttn/ecas/benmodels.html). 

BenMAP uses health impact functions to generate changes in the incidence of health effects. 

Health impact functions are derived from the C-R functions reported in the epidemiology 

literature. A standard health impact function has four components: an effect estimate from a 

particular epidemiological study, a baseline incidence rate for the health effect (obtained from 

either the epidemiology study or a source of public health statistics, such as CDC), the affected 

population, and the estimated change in the relevant pollutant summary measure. 

A typical health impact function might look like this: 

Δ y y = 0 ⋅ (eβ⋅Δx − 1) , 

where y0 is the baseline incidence, equal to the baseline incidence rate times the potentially 

affected population; $ is the effect estimate; )x is the estimated change in the pollutant (e.g., 

PM2.5 or O3) and )y is the estimated change in incidence of the health effect (e.g., the number of 

deaths avoided) associated with the change in the pollutant, )x. There are other functional 

forms, but the basic elements remain the same. 

8B.4.1 Reductions in O3-Related Premature Deaths 

To calculate O3-related life years saved under the Final Small SI and Recreational Marine Engine 

Rule (hereafter, Final SSI & RME Rule), we first calculated the numbers of O3-related statistical 

lives saved within 5-year age groups, using BenMAP. (For more details on the calculation of 

statistical lives saved using BenMAP, see Chapter 8 or the BenMAP user’s manual 

(http://www.epa.gov/ttn/ecas/benmodels.html). We used two studies used in the benefit analysis 

for the Final SSI & RME Rule RIA – Bell et al. (2004) and Levy et al. (2005). Both studies 

report estimated C-R functions of the association between premature mortality and short-term 

exposures to ambient O3. Bell et al. (2004) is a multi-city study of 95 cities, and as such may 

avoid the potential for publication bias that may be inherent in single-city studies or meta8-66 
 Cost-Benefit Analysis 

analyses of single-city studies. This study provides the lowest estimate of O3-related premature 

deaths among the mortality studies included in the Final SSI & RME Rule RIA benefit analysis. 

An upper bound estimate of O3-related premature deaths in the Final SSI & RME Rule RIA 

benefit analysis was provided by Levy et al. (2005). More extensive discussions of these studies 

are given in Chapter 8. 

We checked to confirm that the total number of O3-related statistical lives saved, summed across 

all age groups, equals the corresponding number calculated in the Final SSI & RME Rule RIA 

benefit analysis. Age group-specific O3-related premature deaths avoided under the Final SSI & 

RME Rule in 2020 and in 2030 are given in Table 8B-2. 

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Final Regulatory Impact Analysis 

Table 8B-2. Estimated Reduction in Incidence of O3-Related Premature Mortality Under the Final 

SSI & RME Rule in 2020 and 2030 

Reduction in O3-Related Premature Mortality 

(95% CI)* 

Age 2020 2030 

Interval Bell et al. (2004) Levy et al. (2005) Bell et al. (2004) Levy et al. (2005) 

0 - 4 0 

(0 - 0) 

1 

(1 - 1) 

0 

(0 - 0) 

1 

(1 - 2) 

5 - 9 0 

(0 - 0) 

0 

(0 - 1) 

0 

(0 - 0) 

1 

(0 - 1) 

10 - 14 0 

(0 - 0) 

0 

(0 - 1) 

0 

(0 - 0) 

1 

(0 - 1) 

15 - 19 0 

(0 - 0) 

1 

(0 - 1) 

0 

(0 - 0) 

1 

(1 - 1) 

20 - 24 0 

(0 - 0) 

1 

(1 - 2) 

0 

(0 - 0) 

2 

(1 - 2) 

25 - 29 0 

(0 - 0) 

2 

(1 - 2) 

0 

(0 - 0) 

2 

(2 - 3) 

30 - 34 0 

(0 - 0) 

2 

(1 - 2) 

0 

(0 - 0) 

2 

(1 - 3) 

35 - 39 0 

(0 - 1) 

3 

(2 - 3) 

1 

(0 - 1) 

4 

(3 - 5) 

40 - 44 0 

(0 - 1) 

2 

(2 - 3) 

1 

(0 - 1) 

3 

(2 - 4) 

45 - 49 1 

(0 - 2) 

5 

(3 - 6) 

1 

(0 - 2) 

7 

(5 - 9) 

50 - 54 1 

(0 - 2) 

5 

(4 - 7) 

1 

(0 - 2) 

5 

(4 - 7) 

55 - 59 3 

(1 - 5) 

13 

(9 - 18) 

3 

(1 - 6) 

16 

(11 - 20) 

60 - 64 3 

(1 - 5) 

13 

(9 - 17) 

4 

(1 - 6) 

16 

(11 - 21) 

65 - 69 6 

(2 - 9) 

25 

(17 - 33) 

9 

(3 - 16) 

42 

(29 - 54) 

70 - 74 4 

(1 - 7) 

20 

(14 - 26) 

8 

(3 - 13) 

35 

(24 - 46) 

75 - 79 7 

(2 - 12) 

31 

(22 - 41) 

15 

(5 - 26) 

67 

(46 - 88) 

80 - 84 5 

(2 - 8) 

20 

(14 - 26) 

9 

(3 - 15) 

39 

(27 - 51) 

85+ 15 

(5 - 25) 

65 

(45 - 85) 

24 

(8 - 40) 

100 

(72 - 140) 

Total: 46 

(15 - 77) 

210 

(140 - 270) 

77 

(25 - 130) 

350 

(240 - 460) 

*95 percent confidence or credible intervals (CIs) are based on the uncertainty about the 

coefficient in the mortality C-R functions. All estimates rounded to two significant figures. 

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 Cost-Benefit Analysis 

8B.4.2 Life Years Saved as a Result of Reductions in O3-Related Mortality Risk 

The number of life years saved depends not only on the number of statistical lives saved, but also 

on the life expectancies associated with those statistical lives. As was pointed out in the CEAs 

for the PM and O3 NAAQS RIAs, age-specific life expectancies for the general population are 

calculated from mortality rates for the general population, and these reflect the prevalence of 

chronic disease, which shortens life expectancies. The only reason one might use lower life 

expectancies than those for the general population in the CEA for the Final SSI & RME Rule 

RIA is if the population at risk from exposure to O3 was limited solely or disproportionately to 

individuals with preexisting chronic illness, whose life expectancies were, on average, shorter 

than those of the general population (unless all of those individuals had preexisting chronic 

illness because of long-term exposure to O3). 

It is reasonable to assume that someone who dies from exposure to an air pollutant is already in a 

compromised state. However, there are both acute and chronic compromised states. If an 

individual has an acute illness (e.g., pneumonia) that puts him at risk of mortality when exposed 

to a high concentration of an air pollutant, then in the absence of that high concentration he could 

be expected to recover from the illness and go on to live the expected number of years for 

someone his age – i.e., he would have the age-specific life expectancy of the general population. 

If an individual has a chronic illness that makes him vulnerable to a high concentration of an air 

pollutant, then an important question is whether or not he would have had that chronic illness if 

he had not been exposed over the long term to high levels of the air pollutant. 

We can categorize individuals who are at risk of dying because of exposure to an air pollutant 

into three groups: 

•	 those who are vulnerable because of a preexisting acute condition; 

•	 those who are vulnerable because of a preexisting chronic condition that they would not 

have had, had they not been exposed over the long term to high levels of the air pollutant; 

and 

•	 those who are vulnerable because of a preexisting chronic condition that they would have 

had even in the absence of long term exposure to high levels of the air pollutant. 

The age-specific life expectancies of the general population should apply to the first two groups, 

and the age-specific life expectancies of the subpopulation with the relevant chronic condition(s) 

should apply to the third group. If we knew the proportions of people who die from exposure to 

O3 who are in each group, and the life expectancies of people in the third group, we could 

calculate the number of life years saved as follows: 

Total life years saved = ∑ Mi * ( p1i * LEi + p2i * LEi + p3i * LEi 

*

) 

i 

where 

Mi denotes the number of O3-related deaths of individuals age i, 

LEi denotes the general population life expectancy for age i, 

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Final Regulatory Impact Analysis 

LEi

*

 denotes the life expectancy for age i of the subpopulation with the relevant chronic 

condition(s) – i.e., the third group; 

p1i denotes the proportion of the Mi O3-related deaths that are in the first group; 

p2i denotes the proportion of the Mi O3-related deaths that are in the second group; and 

p3i denotes the proportion of the Mi O3-related deaths that are in the third group. 

Unlike for PM2.5 (discussed below), we currently lack information that would allow us to 

estimate the relevant proportions necessary to estimate the set of life expectancies that would be 

appropriate to apply to O3-related deaths. Although there is substantial evidence linking 

premature mortality to short-term exposures to O3, there is currently not similar evidence for 

long-term exposures. We therefore do not know if the second group above is relevant in the case 

of O3-related mortality. Nor do we know what proportion of O3-related deaths can be attributed 

to preexisting acute conditions (the first group) versus preexisting chronic conditions that these 

individuals would have had even in the absence of long term exposure to O3 (the third group). 

Because we currently lack the necessary information to determine the appropriate set of life 

expectancies to use in calculating life years saved associated with O3-related premature mortality 

avoided, we calculated life years saved based on four different underlying assumptions: 

•	 A lower bound assumption of zero life years saved, based on the hypothesis that the 

observed statistical association between premature mortality and short-term exposures to 

O3 is not actually a causal relationship; 

•	 An upper bound assumption that an O3-related premature death of an individual of a 

given age will result in a loss of life years equal to the life expectancy in the general 

population of that age; 

•	 Two intermediate assumptions: That the proportions of O3-related premature deaths in 

the three groups delineated above (p1i, p2i, and p3i) are such that, on average, the agespecific life expectancies among people who die O3-related premature deaths are those 

of 

o	 people with severe preexisting chronic conditions, whose life expectancies are 

substantially shorter than those of the general population; and 

o	 people with preexisting chronic conditions of a range of severities, whose life 

expectancies are somewhat shorter than those of the general population. 

Life years saved based on the upper bound assumption were calculated from age-specific 

mortality probabilities for the general population taken from the Centers for Disease Control 

(CDC) National Vital Statistics Reports, Vol. 56, No. 9, December 28, 2007, Table 1. Life table 

for the total population: United States, 2004.6

 We used a simplified method of calculating life 

expectancies from these age-specific mortality probabilities that yielded life expectancies that 

were close to the life expectancies derived using the more complicated method employed by the 

http://www.cdc.gov/nchs/data/nvsr/nvsr56/nvsr56_09.pdf 

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6 
 Cost-Benefit Analysis 

CDC.7 In particular, starting with a cohort of size 1,000,000 at birth, we calculated the life-years 

lived between ages x and (x+1), for x = 0, 1, 2, ..., 99, using the age-specific mortality 

probabilities taken from the CDC Vital Statistics Report (see above) and assuming that all deaths 

that occurred between ages x and (x+1) occurred midway through the year (i.e., we assigned 0.5 

life-year to each year of death). The life expectancy at age n was then calculated as the sum of 

the life-years lived from age n through age 100 divided by the cohort size at age n. The life 

expectancy at age n is the number of life years lost due to an O3-related premature mortality of 

an individual age n. 

To estimate life years saved under the two intermediate assumptions about the life years lost as a 

result of O3-related premature mortality, we turned to the epidemiological evidence of a 

statistically significant association between short-term exposures to O3 and respiratory hospital 

admissions. This evidence suggests that these short-term exposures may exacerbate respiratory 

conditions that were preexisting. It is reasonable to suppose that some of these hospitalizations 

for respiratory illnesses on days of relatively high O3 concentrations might result in death. It 

may also be the case that some individuals who did not go to the hospital might also die. We 

therefore looked for information on life expectancies of people with chronic respiratory 

conditions. 

While there is information readily available in vital statistics sources on rates of death from 

chronic respiratory diseases, there is not similarly available information on rates of death among 

that subpopulation who suffer from those diseases. It is the latter rate – the rate of death among 

that subpopulation who suffers from those diseases – that is of interest. 

A recent study of people with and without chronic obstructive pulmonary disease (COPD) 

provided data from which we were able to construct estimates of the mortality rates of interest. 

Mannino et al. (2006) followed a cohort of 15,440 subjects ages 43 to 66 for up to 11 years. The 

cohort subjects were selected from the larger cohort of the Atherosclerosis Risk in Communities 

(ARIC) study, which selected its subjects from the population of four U.S. communities by 

probability sampling.8

 The subjects in the Mannino study were limited to the ARIC participants 

who provided baseline information on respiratory symptoms and diagnoses, who underwent 

pulmonary function testing, and for whom follow-up data were available. 

Using a modification of the criteria developed by the Global Initiative on Obstructive Lung 

Disease (GOLD), Mannino et al. (2006) classified the study subjects into COPD severity groups 

(or stages), with GOLD stage 0 (presence of respiratory symptoms in the absence of any lung 

function abnormality) being the least severe COPD group, and GOLD stages 3 and 4 being the 

most severe. The unadjusted death rates of the study participants (taken from Table 1 of 

Mannino et al., 2006), ratios of (unadjusted) death rates, and hazard ratios, based on Cox 

7

 We calculated life expectancies from the mortality probabilities rather than using the life 

expectancies given in the CDC table because we were going to also calculate life expectancies 

for the subpopulations with severe COPD and with “average” COPD by adjusting the agespecific mortality probabilities and then calculating life expectancies using these adjusted 

probabilities.

8

 In one of the four communities probability sampling was used to select African-Americans 

only. 

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Final Regulatory Impact Analysis 

proportional hazard regressions, which took into account several covariates (including, among 

others, age, sex, race, smoking status, and education level) are shown in the table below. In 

addition, the right-most column of the table below shows the proportion of COPD subjects in the 

study in each GOLD category. 

Table 8B-3. Death Rates and Hazard Ratios for Subjects with Varying Degrees of Severity of 

COPD (from Mannino et al., 2006) 

GOLD* Category N Deaths (%) PersonYears 

Death Rate 

per 1,000 

Person-Years 

Ratio of Death Rate 

to Death Rate for 

Normal Population 

Hazard 

Ratio** 

Proportion of COPD 

Subjects in GOLD 

Category 

GOLD 3 or 4 271 92 33.9% 2,143 42.9 7.97 5.7 4.77% 

GOLD 2 1,484 232 15.6% 12,852 18.1 3.35 2.4 26.14% 

GOLD 1 1,679 137 8.2% 15,031 9.1 1.69 1.4 29.57% 

GOLD 0 2,244 204 9.1% 20,191 10.1 1.88 1.5 39.52% 

Restricted 1,101 150 13.6% 9,644 15.6 2.89 2.3 

Normal 8,661 427 4.9% 79,317 5.4 1.00 1.0 

Total 15,440 1,242 8.0% 139,178 8.9 

*Global Inititative on Obstructive Lung Disease (GOLD) guidelines for the staging of COPD severity. 

**See Mannino et al. (2006), p. 117. 

The ratios of unadjusted death rates are somewhat larger than the corresponding hazard ratios 

because these ratios were not adjusted for age. COPD is a progressive disease, so it would be 

expected that the proportion of older individuals would increase as the stages (and severity) 

increased, and this was indeed the case in the Mannino study. The hazard ratios, being based on 

regressions that took age into account, avoid this problem. We therefore used the hazard ratios 

to derive age-specific mortality rates for individuals with (1) severe COPD and (2) COPD of 

“average” severity. In particular, to derive age-specific mortality probabilities for the 

subpopulation with severe COPD, we multiplied each age-specific mortality probability for the 

general population by 5.7 (the hazard ratio for GOLD 3 or 4); to derive age-specific mortality 

probabilities for the subpopulation with “average” COPD, we multiplied each age-specific 

mortality probability for the general population by a weighted average of the GOLD categoryspecific hazard ratios, where the weight for a GOLD category was the proportion of COPD 

subjects in that GOLD category (given in the right-most column of Table 1 above). The 

weighted average hazard ratio was 1.906. Age-specific life expectancies were then derived for 

the severe COPD and “average” COPD subpopulations using these adjusted mortality 

probabilities and the method for calculating life expectancies described above. 

Once an appropriate set of life expectancies has been determined (e.g., life expectancies for the 

general population or life expectancies for a subpopulation with severe COPD), these then 

provide the number of life years lost for an individual who dies at a given age. This information 

can then be combined with the estimated number of O3-related premature deaths at each age 

calculated with BenMAP (see previous subsection). Because BenMAP calculates numbers of 

premature deaths avoided within age intervals, we can either allocate the premature deaths 

avoided within an age interval uniformly to the ages within the interval or, alternatively, we can 

calculate average life expectancies for the age intervals. We illustrate the first approach in 

8-72 
 Cost-Benefit Analysis 

calculating O3-related life years saved and the second approach in calculating PM2.5-related life 

years saved (see Section 8B.4.4). 

Total O3-related life years gained was calculated as the sum of life years gained at each age: 

N 

Total life years gained = = ∑LEi × Mi 

i=0 

where LEi is the remaining life expectancy for age i, Mi is the number of premature deaths 

avoided among individuals age i, and N is the oldest age considered. 

For the purposes of determining cost effectiveness, it is also necessary to consider the timedependent nature of the gains in life years. Standard economic theory suggests that benefits 

occurring in future years should be discounted relative to benefits occurring in the present. OMB 

and EPA guidance suggest discount rates of three and seven percent. Selection of a 3 percent 

discount rate is also consistent with recommendations from the U.S. Public Health Service Panel 

on Cost Effectiveness in Health and Medicine (Gold et al., 1996). 

Discounted total life years gained is calculated as follows: 

LE 

Discounted LY = ∫0 e −rtdt, 

where r is the discount rate, t indicates time, and LE is the life expectancy at the time when the 

premature death would have occurred. Because O3-related premature mortality is associated 

only with short-term exposures, all O3-related premature deaths are assumed to occur in the year 

of exposure. We therefore did not discount O3-related premature deaths avoided. 

Undiscounted age-specific life expectancies, and age-specific life expectancies using discount 

rates of 3 percent and 7 percent are given for the general population, the subpopulation of 

individuals with severe COPD, and the subpopulation of individuals with COPD of average 

severity in Tables 8B-4, 8B-5, and 8B-6, respectively. The O3-related (discounted) life years 

saved, based on each of the two O3-mortality studies and each of the assumptions about relevant 

life expectancies, are given, using 3 percent and 7 percent discount rates, in Tables 8B-7 and 8B8, respectively. The O3-related (discounted) life years saved, under the first assumption – that 

the observed statistical association between premature mortality and short-term exposures to O3 

is not actually a causal relationship – is zero in all cases (i.e., regardless of the mortality study 

used and the scenario considered), and is therefore not shown in these Tables. 

8-73 
Final Regulatory Impact Analysis 

Table 8B-4. Undiscounted and Discounted Age-Specific Life Expectancies for the General 

Population 

Age at Age-Specific 3% Discounted 7% Discounted 

Beginning Mortality Deaths in Life-Years Life Remaining Life Remaining Life 

of Year Probability* Cohort Size Year in Year Expectancy Expectancy Expectancy 

0 0.006799 1,000,000 6,799 996,600 77.8 30.9 15.2 

1 0.000483 993,201 480 992,961 77.3 30.8 15.2 

2 0.000297 992,721 295 992,574 76.4 30.7 15.2 

3 0.000224 992,427 222 992,315 75.4 30.6 15.2 

4 0.000188 992,204 187 992,111 74.4 30.5 15.2 

5 0.000171 992,017 170 991,932 73.4 30.4 15.2 

6 0.000161 991,847 159 991,768 72.4 30.3 15.2 

7 0.000151 991,688 149 991,613 71.4 30.2 15.2 

8 0.000136 991,538 135 991,471 70.4 30.1 15.2 

9 0.000119 991,403 118 991,345 69.5 29.9 15.1 

10 0.000106 991,286 105 991,233 68.5 29.8 15.1 

11 0.000112 991,180 111 991,125 67.5 29.7 15.1 

12 0.000149 991,070 148 990,996 66.5 29.5 15.1 

13 0.000227 990,922 225 990,809 65.5 29.4 15.1 

14 0.000337 990,697 333 990,530 64.5 29.2 15.1 

15 0.000460 990,363 456 990,135 63.5 29.1 15.1 

16 0.000579 989,907 573 989,621 62.5 28.9 15.1 

17 0.000684 989,334 677 988,996 61.6 28.8 15.0 

18 0.000763 988,657 755 988,280 60.6 28.6 15.0 

19 0.000819 987,902 809 987,498 59.7 28.4 15.0 

20 0.000873 987,093 862 986,662 58.7 28.3 15.0 

21 0.000926 986,231 913 985,775 57.8 28.1 15.0 

22 0.000960 985,318 946 984,845 56.8 27.9 15.0 

23 0.000972 984,372 957 983,893 55.9 27.8 14.9 

24 0.000969 983,415 953 982,939 54.9 27.6 14.9 

25 0.000960 982,462 943 981,991 54.0 27.4 14.9 

26 0.000954 981,519 936 981,051 53.0 27.2 14.9 

27 0.000952 980,583 933 980,117 52.1 27.0 14.8 

28 0.000958 979,650 939 979,181 51.1 26.8 14.8 

29 0.000973 978,712 952 978,235 50.2 26.5 14.8 

30 0.000994 977,759 972 977,273 49.2 26.3 14.7 

31 0.001023 976,787 999 976,287 48.3 26.1 14.7 

32 0.001063 975,788 1,038 975,269 47.3 25.9 14.7 

33 0.001119 974,750 1,091 974,205 46.4 25.6 14.6 

34 0.001192 973,659 1,160 973,079 45.4 25.4 14.6 

35 0.001275 972,499 1,240 971,879 44.5 25.1 14.5 

36 0.001373 971,259 1,334 970,592 43.5 24.9 14.5 

37 0.001493 969,925 1,448 969,201 42.6 24.6 14.4 

38 0.001634 968,477 1,582 967,686 41.7 24.3 14.4 

39 0.001788 966,895 1,729 966,031 40.7 24.0 14.3 

40 0.001945 965,166 1,877 964,228 39.8 23.7 14.3 

41 0.002107 963,290 2,029 962,275 38.9 23.5 14.2 

42 0.002287 961,260 2,198 960,161 38.0 23.2 14.1 

43 0.002494 959,062 2,392 957,866 37.0 22.8 14.0 

44 0.002727 956,670 2,609 955,366 36.1 22.5 14.0 

45 0.002982 954,061 2,845 952,639 35.2 22.2 13.9 

46 0.003246 951,216 3,088 949,672 34.3 21.9 13.8 

8-74 
 Cost-Benefit Analysis 

Table 8B-4. Undiscounted and Discounted Age-Specific Life Expectancies for the General 

Population (cont’d) 

Age at Age-Specific 3% Discounted 7% Discounted 

Beginning Mortality Deaths in Life-Years Life Remaining Life Remaining Life 

of Year Probability* Cohort Size Year in Year Expectancy Expectancy Expectancy 

47 0.003520 948,129 3,337 946,460 33.5 21.6 13.7 

48 0.003799 944,792 3,589 942,997 32.6 21.2 13.6 

49 0.004088 941,203 3,848 939,279 31.7 20.9 13.5 

50 0.004404 937,355 4,128 935,291 30.8 20.5 13.4 

51 0.004750 933,227 4,433 931,010 30.0 20.2 13.3 

52 0.005113 928,794 4,749 926,419 29.1 19.8 13.2 

53 0.005488 924,045 5,071 921,510 28.2 19.4 13.0 

54 0.005879 918,974 5,403 916,273 27.4 19.1 12.9 

55 0.006295 913,571 5,751 910,696 26.6 18.7 12.7 

56 0.006754 907,820 6,131 904,755 25.7 18.3 12.6 

57 0.007280 901,689 6,564 898,407 24.9 17.9 12.4 

58 0.007903 895,125 7,074 891,588 24.1 17.5 12.3 

59 0.008633 888,051 7,667 884,217 23.3 17.1 12.1 

60 0.009493 880,384 8,357 876,205 22.5 16.7 11.9 

61 0.010449 872,027 9,112 867,471 21.7 16.2 11.8 

62 0.011447 862,915 9,878 857,976 20.9 15.8 11.6 

63 0.012428 853,037 10,601 847,736 20.1 15.4 11.4 

64 0.013408 842,435 11,295 836,788 19.4 15.0 11.2 

65 0.014473 831,140 12,029 825,126 18.6 14.5 11.0 

66 0.015703 819,111 12,863 812,680 17.9 14.1 10.7 

67 0.017081 806,249 13,771 799,363 17.2 13.7 10.5 

68 0.018623 792,477 14,758 785,098 16.5 13.2 10.3 

69 0.020322 777,719 15,805 769,817 15.8 12.8 10.0 

70 0.022104 761,915 16,841 753,494 15.1 12.3 9.8 

71 0.024023 745,073 17,899 736,124 14.4 11.9 9.5 

72 0.026216 727,174 19,064 717,642 13.7 11.5 9.3 

73 0.028745 708,110 20,355 697,933 13.1 11.0 9.0 

74 0.031561 687,756 21,706 676,903 12.5 10.6 8.7 

75 0.034427 666,050 22,930 654,585 11.9 10.2 8.4 

76 0.037379 643,120 24,039 631,100 11.3 9.7 8.2 

77 0.040756 619,080 25,231 606,465 10.7 9.3 7.9 

78 0.044764 593,849 26,583 580,558 10.1 8.9 7.6 

79 0.049395 567,266 28,020 553,256 9.6 8.5 7.3 

80 0.054471 539,246 29,373 524,560 9.0 8.1 7.0 

81 0.059772 509,873 30,476 494,635 8.5 7.7 6.7 

82 0.065438 479,397 31,371 463,712 8.1 7.3 6.4 

83 0.071598 448,026 32,078 431,987 7.6 6.9 6.1 

84 0.078516 415,949 32,659 399,619 7.1 6.5 5.8 

85 0.085898 383,290 32,924 366,828 6.7 6.2 5.6 

86 0.093895 350,366 32,897 333,917 6.3 5.8 5.3 

87 0.102542 317,468 32,554 301,192 5.9 5.5 5.0 

88 0.111875 284,915 31,875 268,977 5.5 5.1 4.7 

89 0.121928 253,040 30,853 237,613 5.1 4.8 4.5 

90 0.132733 222,187 29,492 207,441 4.8 4.5 4.2 

91 0.144318 192,695 27,809 178,791 4.4 4.2 3.9 

92 0.156707 164,886 25,839 151,967 4.1 3.9 3.7 

93 0.169922 139,047 23,627 127,234 3.7 3.6 3.4 

94 0.183975 115,420 21,234 104,803 3.4 3.3 3.1 

95 0.198875 94,186 18,731 84,820 3.0 3.0 2.8 

96 0.214620 75,454 16,194 67,357 2.7 2.6 2.5 

97 0.231201 59,260 13,701 52,410 2.3 2.2 2.2 

98 0.248600 45,559 11,326 39,896 1.8 1.8 1.8 

99 0.266786 34,233 9,133 29,667 1.2 1.2 1.2 

100 1.000000 25,100 25,100 12,550 0.5 0.5 0.5 

*Mortality probabilities for the general population taken from Table 1. Life table for the total population: 

United States, 2004. CDC National Vital Statistics Reports, Vol. 56, No. 9, December 28, 2007 

http://www.cdc.gov/nchs/data/nvsr/nvsr56/nvsr56_09.pdf 

8-75
Final Regulatory Impact Analysis 

Table 8B-5. Undiscounted and Discounted Age-Specific Life Expectancies for the Subpopulation 

with Severe COPD 

Age at Age-Specific 3% Discounted 7% Discounted 

Beginning Mortality Deaths in Life-Years Life Remaining Life Remaining Life 

of Year Probability* Cohort Size Year in Year Expectancy Expectancy Expectancy 

0 0.038755 1,000,000 38,755 980,622 54.5 27.5 14.9 

1 0.002752 961,245 2,646 959,922 55.7 27.7 14.9 

2 0.001692 958,599 1,622 957,788 54.9 27.5 14.9 

3 0.001277 956,977 1,222 956,366 53.9 27.4 14.9 

4 0.001074 955,755 1,026 955,242 53.0 27.2 14.9 

5 0.000978 954,729 933 954,263 52.1 27.0 14.8 

6 0.000916 953,796 873 953,359 51.1 26.8 14.8 

7 0.000859 952,923 819 952,513 50.2 26.5 14.8 

8 0.000777 952,104 739 951,734 49.2 26.3 14.7 

9 0.000677 951,365 644 951,043 48.2 26.1 14.7 

10 0.000606 950,721 576 950,433 47.3 25.8 14.7 

11 0.000636 950,145 605 949,842 46.3 25.6 14.6 

12 0.000850 949,540 807 949,137 45.3 25.3 14.6 

13 0.001295 948,733 1,229 948,119 44.4 25.1 14.5 

14 0.001918 947,505 1,818 946,596 43.4 24.8 14.5 

15 0.002625 945,687 2,482 944,446 42.5 24.6 14.4 

16 0.003301 943,205 3,113 941,648 41.6 24.3 14.4 

17 0.003901 940,092 3,667 938,258 40.8 24.0 14.3 

18 0.004351 936,424 4,075 934,387 39.9 23.8 14.3 

19 0.004671 932,350 4,355 930,172 39.1 23.5 14.2 

20 0.004976 927,995 4,618 925,686 38.3 23.3 14.1 

21 0.005278 923,377 4,873 920,941 37.5 23.0 14.1 

22 0.005472 918,504 5,026 915,991 36.7 22.7 14.0 

23 0.005542 913,478 5,063 910,947 35.9 22.4 13.9 

24 0.005522 908,415 5,016 905,907 35.1 22.2 13.9 

25 0.005470 903,399 4,942 900,928 34.2 21.9 13.8 

26 0.005436 898,458 4,884 896,016 33.4 21.6 13.7 

27 0.005425 893,573 4,847 891,150 32.6 21.2 13.6 

28 0.005461 888,726 4,853 886,300 31.8 20.9 13.5 

29 0.005547 883,873 4,903 881,422 31.0 20.6 13.4 

30 0.005668 878,970 4,982 876,479 30.1 20.2 13.3 

31 0.005830 873,988 5,095 871,440 29.3 19.9 13.2 

32 0.006061 868,893 5,266 866,260 28.5 19.5 13.1 

33 0.006380 863,626 5,510 860,872 27.6 19.2 12.9 

34 0.006792 858,117 5,828 855,203 26.8 18.8 12.8 

35 0.007269 852,289 6,195 849,191 26.0 18.4 12.7 

36 0.007827 846,094 6,622 842,783 25.2 18.0 12.5 

37 0.008510 839,472 7,144 835,900 24.4 17.6 12.3 

38 0.009312 832,328 7,750 828,452 23.6 17.2 12.2 

39 0.010191 824,577 8,403 820,376 22.8 16.8 12.0 

40 0.011084 816,174 9,047 811,651 22.0 16.4 11.8 

41 0.012008 807,128 9,692 802,282 21.3 16.0 11.7 

42 0.013035 797,436 10,395 792,238 20.5 15.6 11.5 

43 0.014215 787,041 11,187 781,447 19.8 15.2 11.3 

44 0.015546 775,854 12,061 769,823 19.1 14.8 11.1 

45 0.016996 763,792 12,981 757,301 18.4 14.4 10.9 

46 0.018503 750,811 13,892 743,865 17.7 14.0 10.7 

8-76 
 Cost-Benefit Analysis 

Table 8B-5. Undiscounted and Discounted Age-Specific Life Expectancies for the Subpopulation 

with Severe COPD (cont’d) 

Age at Age-Specific 3% Discounted 7% Discounted 

Beginning Mortality Deaths in Life-Years Life Remaining Life Remaining Life 

of Year Probability* Cohort Size Year in Year Expectancy Expectancy Expectancy 

47 0.020061 736,919 14,784 729,527 17.0 13.6 10.4 

48 0.021652 722,135 15,636 714,317 16.3 13.1 10.2 

49 0.023303 706,500 16,464 698,268 15.7 12.7 10.0 

50 0.025103 690,036 17,322 681,375 15.0 12.3 9.8 

51 0.027075 672,714 18,214 663,607 14.4 11.9 9.5 

52 0.029144 654,500 19,075 644,963 13.8 11.5 9.3 

53 0.031280 635,425 19,876 625,487 13.2 11.1 9.0 

54 0.033512 615,549 20,628 605,235 12.6 10.7 8.8 

55 0.035880 594,921 21,346 584,248 12.0 10.3 8.5 

56 0.038497 573,575 22,081 562,535 11.5 9.9 8.2 

57 0.041497 551,494 22,885 540,052 10.9 9.5 8.0 

58 0.045046 528,609 23,812 516,703 10.3 9.0 7.7 

59 0.049211 504,797 24,842 492,376 9.8 8.6 7.4 

60 0.054108 479,956 25,969 466,971 9.3 8.2 7.1 

61 0.059560 453,986 27,040 440,467 8.8 7.9 6.9 

62 0.065249 426,947 27,858 413,018 8.3 7.5 6.6 

63 0.070839 399,089 28,271 384,953 7.9 7.1 6.3 

64 0.076425 370,818 28,340 356,648 7.4 6.8 6.0 

65 0.082495 342,478 28,253 328,352 7.0 6.4 5.8 

66 0.089507 314,225 28,125 300,163 6.6 6.1 5.5 

67 0.097361 286,100 27,855 272,173 6.2 5.7 5.2 

68 0.106149 258,245 27,413 244,539 5.8 5.4 5.0 

69 0.115833 230,833 26,738 217,463 5.4 5.1 4.7 

70 0.125993 204,094 25,714 191,237 5.1 4.8 4.4 

71 0.136933 178,380 24,426 166,167 4.7 4.5 4.2 

72 0.149433 153,954 23,006 142,451 4.4 4.2 3.9 

73 0.163847 130,948 21,455 120,220 4.1 3.9 3.7 

74 0.179896 109,493 19,697 99,644 3.8 3.6 3.5 

75 0.196231 89,795 17,621 80,985 3.5 3.4 3.2 

76 0.213062 72,175 15,378 64,486 3.2 3.1 3.0 

77 0.232309 56,797 13,194 50,200 3.0 2.9 2.8 

78 0.255152 43,603 11,125 38,040 2.7 2.7 2.6 

79 0.281552 32,477 9,144 27,905 2.5 2.4 2.4 

80 0.310486 23,333 7,245 19,711 2.3 2.2 2.2 

81 0.340699 16,089 5,481 13,348 2.1 2.0 2.0 

82 0.372994 10,607 3,956 8,629 1.9 1.9 1.8 

83 0.408108 6,651 2,714 5,294 1.7 1.7 1.7 

84 0.447543 3,937 1,762 3,056 1.5 1.5 1.5 

85 0.489619 2,175 1,065 1,642 1.4 1.4 1.4 

86 0.535199 1,110 594 813 1.3 1.3 1.2 

87 0.584489 516 302 365 1.1 1.1 1.1 

88 0.637689 214 137 146 1.0 1.0 1.0 

89 0.694992 78 54 51 0.9 0.9 0.9 

90 0.756579 24 18 15 0.8 0.8 0.8 

91 0.822612 6 5 3 0.6 0.6 0.6 

92 0.893232 1 0 0 0.0 0.0 0.0 

*Mortality probabilities derived from mortality probabilities for the general population by multiplying 

by the hazard ratio (5.7) for GOLD 3 or 4, from Mannino et al. (2006). 

8-77
Final Regulatory Impact Analysis 

Table 8B-6. Undiscounted and Discounted Age-Specific Life Expectancies for the Subpopulation 

with COPD of Average Severity 

Age at Age-Specific 3% Discounted 7% Discounted 

Beginning Mortality Deaths in Life-Years Life Remaining Life Remaining Life 

of Year Probability* Cohort Size Year in Year Expectancy Expectancy Expectancy 

0 0.012960 1,000,000 12,960 993,520 69.6 29.9 15.1 

1 0.000920 987,040 908 986,586 69.5 29.9 15.1 

2 0.000566 986,132 558 985,853 68.6 29.8 15.1 

3 0.000427 985,574 421 985,363 67.6 29.7 15.1 

4 0.000359 985,153 354 984,976 66.7 29.5 15.1 

5 0.000327 984,799 322 984,638 65.7 29.4 15.1 

6 0.000306 984,477 301 984,326 64.7 29.3 15.1 

7 0.000287 984,176 283 984,034 63.7 29.1 15.1 

8 0.000260 983,893 256 983,765 62.7 29.0 15.1 

9 0.000226 983,638 223 983,526 61.8 28.8 15.1 

10 0.000203 983,415 199 983,315 60.8 28.6 15.0 

11 0.000213 983,216 209 983,111 59.8 28.5 15.0 

12 0.000284 983,006 279 982,867 58.8 28.3 15.0 

13 0.000433 982,727 426 982,514 57.8 28.1 15.0 

14 0.000642 982,302 630 981,986 56.8 27.9 15.0 

15 0.000878 981,671 862 981,241 55.9 27.8 14.9 

16 0.001104 980,810 1,083 980,268 54.9 27.6 14.9 

17 0.001304 979,727 1,278 979,088 54.0 27.4 14.9 

18 0.001455 978,449 1,424 977,737 53.1 27.2 14.9 

19 0.001562 977,025 1,526 976,262 52.1 27.0 14.8 

20 0.001664 975,499 1,623 974,688 51.2 26.8 14.8 

21 0.001765 973,876 1,719 973,017 50.3 26.6 14.8 

22 0.001830 972,157 1,779 971,268 49.4 26.4 14.7 

23 0.001853 970,378 1,798 969,479 48.5 26.1 14.7 

24 0.001846 968,580 1,788 967,686 47.6 25.9 14.7 

25 0.001829 966,792 1,769 965,907 46.7 25.7 14.6 

26 0.001818 965,023 1,754 964,146 45.7 25.5 14.6 

27 0.001814 963,269 1,747 962,395 44.8 25.2 14.5 

28 0.001826 961,521 1,756 960,643 43.9 25.0 14.5 

29 0.001855 959,766 1,780 958,875 43.0 24.7 14.5 

30 0.001896 957,985 1,816 957,077 42.1 24.4 14.4 

31 0.001949 956,169 1,864 955,237 41.1 24.2 14.3 

32 0.002027 954,305 1,934 953,338 40.2 23.9 14.3 

33 0.002133 952,371 2,032 951,355 39.3 23.6 14.2 

34 0.002271 950,339 2,158 949,260 38.4 23.3 14.1 

35 0.002431 948,181 2,305 947,028 37.5 23.0 14.1 

36 0.002617 945,876 2,476 944,638 36.6 22.7 14.0 

37 0.002846 943,400 2,685 942,058 35.7 22.4 13.9 

38 0.003114 940,716 2,929 939,251 34.8 22.0 13.8 

39 0.003408 937,786 3,196 936,189 33.9 21.7 13.7 

40 0.003707 934,591 3,464 932,859 33.0 21.4 13.6 

41 0.004016 931,127 3,739 929,257 32.1 21.0 13.5 

42 0.004359 927,388 4,042 925,366 31.2 20.7 13.4 

43 0.004753 923,345 4,389 921,151 30.4 20.3 13.3 

44 0.005199 918,956 4,777 916,567 29.5 20.0 13.2 

45 0.005683 914,179 5,196 911,581 28.7 19.6 13.1 

46 0.006187 908,983 5,624 906,171 27.8 19.2 13.0 

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 Cost-Benefit Analysis 

Table 8B-6. Undiscounted and Discounted Age-Specific Life Expectancies for the Subpopulation 

with COPD of Average Severity (cont’d) 

Age at Age-Specific 3% Discounted 7% Discounted 

Beginning Mortality Deaths in Life-Years Life Remaining Life Remaining Life 

of Year Probability* Cohort Size Year in Year Expectancy Expectancy Expectancy 

47 0.006709 903,359 6,060 900,329 27.0 18.9 12.8 

48 0.007241 897,298 6,497 894,050 26.2 18.5 12.7 

49 0.007793 890,801 6,942 887,331 25.3 18.1 12.5 

50 0.008395 883,860 7,420 880,150 24.5 17.7 12.4 

51 0.009054 876,440 7,935 872,472 23.7 17.3 12.2 

52 0.009746 868,505 8,464 864,273 23.0 16.9 12.1 

53 0.010460 860,040 8,996 855,542 22.2 16.5 11.9 

54 0.011207 851,044 9,537 846,276 21.4 16.1 11.7 

55 0.011999 841,507 10,097 836,458 20.6 15.7 11.5 

56 0.012874 831,410 10,703 826,058 19.9 15.3 11.3 

57 0.013877 820,707 11,389 815,012 19.1 14.8 11.1 

58 0.015064 809,318 12,191 803,222 18.4 14.4 10.9 

59 0.016456 797,127 13,118 790,568 17.7 14.0 10.7 

60 0.018094 784,009 14,186 776,916 17.0 13.5 10.4 

61 0.019917 769,823 15,333 762,157 16.3 13.1 10.2 

62 0.021820 754,490 16,463 746,259 15.6 12.7 10.0 

63 0.023689 738,028 17,483 729,286 14.9 12.3 9.7 

64 0.025557 720,545 18,415 711,337 14.3 11.8 9.5 

65 0.027587 702,130 19,370 692,445 13.6 11.4 9.2 

66 0.029932 682,760 20,436 672,542 13.0 11.0 8.9 

67 0.032558 662,324 21,564 651,542 12.4 10.5 8.7 

68 0.035497 640,760 22,745 629,388 11.8 10.1 8.4 

69 0.038735 618,015 23,939 606,046 11.2 9.7 8.1 

70 0.042133 594,076 25,030 581,561 10.6 9.3 7.8 

71 0.045791 569,046 26,057 556,017 10.1 8.9 7.6 

72 0.049971 542,989 27,134 529,422 9.6 8.4 7.3 

73 0.054791 515,855 28,264 501,723 9.0 8.0 7.0 

74 0.060158 487,591 29,333 472,924 8.5 7.6 6.7 

75 0.065621 458,258 30,071 443,223 8.0 7.3 6.4 

76 0.071249 428,187 30,508 412,933 7.6 6.9 6.1 

77 0.077685 397,679 30,894 382,232 7.1 6.5 5.8 

78 0.085324 366,785 31,296 351,137 6.7 6.1 5.6 

79 0.094152 335,489 31,587 319,696 6.2 5.8 5.3 

80 0.103828 303,902 31,554 288,125 5.8 5.4 5.0 

81 0.113932 272,349 31,029 256,834 5.5 5.1 4.7 

82 0.124731 241,319 30,100 226,269 5.1 4.8 4.5 

83 0.136473 211,219 28,826 196,806 4.8 4.5 4.2 

84 0.149661 182,394 27,297 168,745 4.4 4.2 4.0 

85 0.163731 155,096 25,394 142,399 4.1 3.9 3.7 

86 0.178974 129,702 23,213 118,096 3.8 3.7 3.5 

87 0.195456 106,489 20,814 96,082 3.5 3.4 3.3 

88 0.213247 85,675 18,270 76,540 3.3 3.2 3.1 

89 0.232409 67,405 15,666 59,572 3.0 3.0 2.8 

90 0.253004 51,740 13,090 45,194 2.8 2.7 2.7 

91 0.275086 38,649 10,632 33,333 2.6 2.5 2.5 

92 0.298702 28,017 8,369 23,833 2.4 2.4 2.3 

93 0.323890 19,649 6,364 16,467 2.2 2.2 2.1 

94 0.350677 13,285 4,659 10,955 2.0 2.0 2.0 

95 0.379078 8,626 3,270 6,991 1.9 1.8 1.8 

96 0.409089 5,356 2,191 4,261 1.7 1.7 1.6 

97 0.440695 3,165 1,395 2,468 1.5 1.5 1.5 

98 0.473858 1,770 839 1,351 1.3 1.3 1.3 

99 0.508523 931 474 695 1.0 1.0 1.0 

100 1.000000 458 458 229 0.5 0.5 0.5 

*Mortality probabilities derived from mortality probabilities for the general population (see Table 2) by multiplying 

by the weighted average of hazard ratios for the GOLD severity categories (1.906) from Mannino et al. (2006). 

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Final Regulatory Impact Analysis 

Table 8B-7. Estimated O3-Related Life Years Saved in 2020 and in 2030 Under the Final SSI & 

RME Rule, Using a 3 Percent Discount Rate 

Estimated O3-Related Life Years Saved 

(95% CI)* 

2020 2030 

Mortality Study: Bell et al (2004) Levy et al. (2005) Bell et al (2004) Levy et al. (2005) 

Assuming Life Expectancies of the 

General Population 

500 

(150 - 800) 

2,200 

(1,500 - 2,900) 

700 

(250 - 1,200) 

3,500 

(2,400 - 4,600) 

Assuming Life Expectancies of the SubPopulation with COPD of Average 

Severity 

360 

(120 - 600) 

1,700 

(1,200 - 2,200) 

560 

(180 - 900) 

2,700 

(1,800 - 3,500) 

Assuming Life Expectancies of the SubPopulation with Severe COPD 

190 

(60 - 320) 

1,000 

(700 - 1,300) 

290 

(100 - 490) 

1,500 

(1,000 - 1,900) 

*95 percent confidence or credible intervals are based on the uncertainty about the coefficient in the mortality C-R 

functions. All estimates rounded to two significant figures. 

Table 8B-8. Estimated O3-Related Life Years Saved in 2020 and in 2030 Under the Final SSI & RME 

Rule, Using a 7 Percent Discount Rate 

Estimated O3-Related Life Years Saved 

(95% CI)* 

2020 2030 

Mortality Study: Bell et al (2004) Levy et al. (2005) Bell et al (2004) Levy et al. (2005) 

Assuming Life Expectancies of the 

General Population 

360 

(120 - 600) 

1,700 

(1,200 - 2,200) 

590 

(190 - 1,000) 

2,700 

(1,900 - 3,500) 

Assuming Life Expectancies of the SubPopulation with COPD of Average 

Severity 

290 

(90 - 500) 

1,400 

(900 - 1,800) 

460 

(150 - 800) 

2,100 

(1,500 - 2,800) 

Assuming Life Expectancies of the SubPopulation with Severe COPD 

170 

(50 - 280) 

800 

(600 - 1,100) 

250 

(80 - 430) 

1,200 

(800 - 1,600) 

*95 percent confidence or credible intervals are based on the uncertainty about the coefficient in the mortality C-R 

functions. All estimates rounded to two significant figures. 

8B.4.3 Reductions in PM2.5-Related Premature Deaths 

To generate PM2.5-related health outcomes, we used the same framework as for the benefit-cost 

analysis described in Chapter 8 and briefly summarized above in the introductory portion of 

Section 8B.4. 

As in several recent air pollution health impact assessments (e.g., Kunzli et al., 2000; EPA, 

2004), we focused on the prospective cohort long-term exposure studies in deriving the health 

impact function for the estimate of premature mortality. Cohort analyses are better able to 

capture the full public health impact of exposure to air pollution over time (Kunzli et al., 2001; 

NRC, 2002). We selected an effect estimate from the extended analysis of the ACS cohort (Pope 

et al., 2002) as well as from the Harvard Six City Study (Laden et al., 2006). Given the focus in 

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 Cost-Benefit Analysis 

this analysis on developing a broader expression of uncertainties in the benefits estimates, and 

the weight that was placed on both the ACS and Harvard Six-city studies by experts participating 

in the PM2.5 mortality expert elicitation, we elected to provide estimates derived from both Pope 

et al. (2002) and Laden et al. (2006). 

This latest re-analysis of the ACS cohort data (Pope et al, 2002) provides additional refinements 

to the analysis of PM-related mortality by (a) extending the follow-up period for the ACS study 

subjects to 16 years, which triples the size of the mortality data set; (b) substantially increasing 

exposure data, including consideration for cohort exposure to PM2.5 following implementation of 

PM2.5 standard in 1999; (c) controlling for a variety of personal risk factors including 

occupational exposure and diet; and (d) using advanced statistical methods to evaluate specific 

issues that can adversely affect risk estimates, including the possibility of spatial autocorrelation 

of survival times in communities located near each other. The effect estimate from Pope et al. 

(2002) quantifies the relationship between annual mean PM2.5 levels and all-cause mortality in 

adults 30 and older. We selected the effect estimate estimated using the measure of PM 

representing average exposure over the follow-up period, calculated as the average of 1979–1984 

and 1999–2000 PM2.5 levels. The effect estimate from this study is 0.0058, which is equivalent 

to a relative risk of 1.06 for a 10 :g change in PM2.5. 

A recent follow up to the Harvard 6-city study (Laden et al., 2006) both confirmed the effect size 

from the first study and provided additional confirmation that reductions in PM2.5 directly result 

in reductions in the risk of premature death. This additional evidence stems from the observed 

reductions in PM2.5 in each city during the extended follow-up period. Laden et al. (2006) found 

that mortality rates consistently went down at a rate proportionate to the observed reductions in 

PM2.5. The effect estimate obtained from Laden et al. (2006) is 0.0148, which is equivalent to a 

relative risk of 1.16 for a 10 μg/m3 change in PM2.5. 

Age, cause, and county-specific mortality rates were obtained from CDC for the years 1996 

through 1998. CDC maintains an online data repository of health statistics, CDC Wonder, 

accessible at http://wonder.cdc.gov/. The mortality rates provided are derived from U.S. death 

records and U.S. Census Bureau postcensal population estimates. Mortality rates were averaged 

across 3 years (1996 through 1998) to provide more stable estimates. When estimating rates for 

age groups that differed from the CDC Wonder groupings, we assumed that rates were uniform 

across all ages in the reported age group. For example, to estimate mortality rates for individuals 

ages 30 and up, we scaled the 25- to 34-year old death count and population by one-half and then 

generated a population-weighted mortality rate using data for the older age groups. 

The reductions in incidence of PM2.5-related premature mortality within each age group 

associated with the Final SSI & RME Rule in 2020 and 2030 are summarized in Table 8B-9. 

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Final Regulatory Impact Analysis 

Table 8B-9: Estimated Reduction in Incidence of PM2.5-Related All-Cause Premature Mortality 

Under the Final SSI & RME Rule in 2020 and 2030 

Reduction in PM2.5-Related Premature Mortality 

(90% CI)* 

Age 

Interval 

2020 2030 

Pope et al. (2002) Laden et al. (2006) Pope et al. (2002) Laden et al. (2006) 

25 - 29 --- 3 

(2 - 5) --- 4 (2 - 5) 

30 - 34 1 

(0 - 2) 

3 

(2 - 4) 

2 

(1 - 3) 

4 

(2 - 5) 

35 - 44 3 

(1 - 5) 

7 

(4 - 10) 

5 

(2 - 8) 

11 

(6 - 17) 

45 - 54 5 

(2 - 9) 

12 

(7 - 18) 

9 

(3 - 14) 

20 

(11 - 29) 

55 - 64 13 

(5 - 21) 

29 

(16 - 43) 

22 

(9 - 35) 

50 

(27 - 72) 

65 - 74 19 

(7 - 30) 

42 

(23 - 61) 

51 

(20 - 81) 

110 

(62 - 170) 

75 - 84 31 

(12 - 49) 

69 

(38 - 100) 

69 

(27 - 110) 

160 

(85 - 230) 

85+ 47 

(18 - 75) 

110 

(57 - 150) 

68 

(27 - 110) 

150 

(84 - 220) 

Total: 120 

(47 - 190) 

270 

(150 - 390) 

230 

(88 - 360) 

510 

(280 - 750) 

*90 percent confidence or credible intervals (CIs) are based on the uncertainty about the 

coefficient in the mortality C-R functions. All estimates rounded to two significant figures. 

8B.4.4 Life Years Saved as a Result of Reductions in PM2.5-Related Mortality Risk 

To calculate life years saved associated with a given change in air pollution, we used a life table 

approach coupled with age-specific estimates of reductions in premature mortality. We began 

with the complete unabridged life table for the United States in 2000, obtained from CDC (CDC, 

2002). For each 1-year age interval (e.g., zero to one, one to two) the life table provides 

estimates of the baseline probability of dying during the interval, person years lived in the 

interval, and remaining life expectancy. From this unabridged life table, we constructed an 

abridged life table to match the age intervals for which we have predictions of changes in 

incidence of premature mortality. We used the abridgement method described in CDC (2002). 

Table 8B-10 presents the abridged life table for 10-year age intervals for adults over 30 (to match 

the Pope et al. [2002] study population). Note that the abridgement actually includes one 5-year 

interval, covering adults 30 to 34, with the remaining age intervals covering 10 years each. This 

is to provide conformity with the age intervals available for mortality rates. 

From the abridged life table (Table 8B-10), we obtained the remaining life expectancy for each 

age cohort, conditional on surviving to that age. This is then the number of life years lost for an 

individual in the general population dying during that age interval. This information can then be 

combined with the estimated number of premature deaths in each age interval calculated with 

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 Cost-Benefit Analysis 

BenMAP (see previous subsection). Total life years gained will then be the sum of life years 

gained in each age interval: 

N 

TotalLife Years = ∑LEi × M i , i =1 

where LEi is the remaining life expectancy for age interval i, Mi is the change in incidence of 

mortality in age interval i, and N is the number of age intervals. 

As noted above, for the purposes of determining cost-effectiveness, it is also necessary to 

consider the time-dependent nature of the gains in life years. Standard economic theory suggests 

that benefits occurring in future years should be discounted relative to benefits occurring in the 

present. OMB and EPA guidance suggest discount rates of three and seven percent. Selection of 

a 3 percent discount rate is also consistent with recommendations from the U.S. Public Health 

Service Panel on Cost Effectiveness in Health and Medicine (Gold et al., 1996). 

Table 8B-10. Abridged Life Table for the Total Population, United States, 2000 

Total 

Person Number of 

Probability Number Years Person 

of Dying Dying Lived Years 

Between Number Between Between Lived Expectation 

Ages x to Surviving to Ages x to Ages x to Above Age of Life at 

Age Interval x+1 Age x x+1 x+1 x Age x 

Start 

Age 

End 

Age qx Ix dx Lx Tx ex 

30 35 0.00577 97,696 564 487,130 4,723,539 48.3 

35 45 0.01979 97,132 1,922 962,882 4,236,409 43.6 

45 55 0.04303 95,210 4,097 934,026 3,273,527 34.4 

55 65 0.09858 91,113 8,982 872,003 2,339,501 25.7 

65 75 0.21779 82,131 17,887 740,927 1,467,498 17.9 

75 85 0.45584 64,244 29,285 505,278 726,571 11.3 

85 95 0.79256 34,959 27,707 196,269 221,293 6.3 

95 100 0.75441 7,252 5,471 20,388 25,024 3.5 

100+ 1.00000 1,781 1,781 4,636 4,636 2.6 

Unlike O3-related premature deaths, PM2.5-related premature deaths are associated with longterm exposures. We therefore did not assume that these deaths all occur in 2020 or 2030. The 

PM2.5-related premature deaths avoided and associated life years saved are thus further 

discounted to account for the lag between the reduction in ambient PM2.5 and the corresponding 

reduction in mortality risk. We used the same 20-year segmented lag structure that is used in the 

benefit-cost analysis (see Chapter 8). 

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Final Regulatory Impact Analysis 

The most complete estimate of the impacts of PM2.5 on life years is calculated using the Pope et 

al. (2002) C-R function relating all-cause mortality in adults 30 and over with ambient PM2.5 

concentrations averaged over the periods 1979–1983 and 1999–2000. Use of all-cause mortality 

is appropriate if there are no differences in the life expectancy of individuals dying from air 

pollution-related causes and those dying from other causes. The argument that long-term 

exposure to PM2.5 may affect mainly individuals with serious preexisting illnesses is not 

supported by current empirical studies. For example, the Krewski et al. (2000) ACS reanalysis 

suggests that the mortality risk is no greater for those with preexisting illness at time of 

enrollment in the study. Life expectancy for the general population in fact includes individuals 

with serious chronic illness. Mortality rates for the general population then reflect prevalence of 

chronic disease, and as populations age the prevalence of chronic disease increases. 

The only reason one might use a lower life expectancy is if the population at risk from air 

pollution was limited solely to those with preexisting disease. Also, note that the OMB Circular 

A-4 notes that “if QALYs are used to evaluate a lifesaving rule aimed at a population that 

happens to experience a high rate of disability (i.e., where the rule is not designed to affect the 

disability), the number of life years saved should not necessarily be diminished simply because 

the rule saves lives of people with life-shortening disabilities. Both analytic simplicity and 

fairness suggest that the estimate number of life years saved for the disabled population should 

be based on average life expectancy information for the relevant age cohorts.” As such, use of a 

general population life expectancy is preferred over disability-specific life expectancies. Our 

primary life years calculations are thus consistent with the concept of not penalizing individuals 

with disabling chronic health conditions by assessing them reduced benefits of mortality risk 

reductions. PM2.5-Related life years saved under the Final SSI & RME Rule in 2020 and 2030 

are given in Table 8B-11. 

Table 8B-11. Estimated PM2.5-Related Life Years Saved Under the Final SSI & RME Rule in 2020 

and 2030 

Estimated PM2.5-Related Life Years Saved 

(95% CI)* 

2020 2030 

Pope et al (2002) Laden et al. (2006) Pope et al (2002) Laden et al. (2006) 

Discounted back to 2020 or 2030, 

using a 3 percent discount rate: 

1,100 

(400 - 1,800) 

2,600 

(1,400 - 4,000) 

2,200 

(900 - 3,500) 

5,000 

(2,700 - 7,000) 

Discounted back to 2020 or 2030, 

using a 7 percent discount rate: 

800 

(300 - 1,200) 

1,800 

(1,000 - 2,500) 

1,500 

(600 - 2,400) 

3,500 

(1,900 - 5,100) 

*95 percent confidence or credible intervals (CIs) are based on the uncertainty about the coefficient in the mortality C-R 

functions. All estimates rounded to two significant figures. 

For this analysis, direct impacts on life expectancy are measured only through the estimated 

change in mortality risk based on the Pope et al. (2002) C-R function. The SAB-HES has 

advised against including additional gains in life expectancy due to reductions in incidence of 

chronic disease or nonfatal heart attacks (EPA-SAB-COUNCIL-ADV-04-002). Although 

reductions in these endpoints are likely to result in increased life expectancy, the HES has 

suggested that the cohort design and relatively long follow-up period in the Pope et al. study 

8-84 
 Cost-Benefit Analysis 

should capture any life-prolonging impacts associated with those endpoints. Impacts of CB and 

nonfatal heart attacks on quality of life will be captured separately in the QALY calculation as 

years lived with improved quality of life. The methods for calculating this benefit are discussed 

below. 

8B.4.5 Calculating Changes in the Quality of Life Years (PM2.5-Related Chronic Morbidity) 

In addition to directly measuring the quantity of life gained, measured by life years, it may also 

be informative to measure gains in the quality of life. The indirect reductions in levels of PM2.5 

also lead to reductions in serious illnesses that affect quality of life. These include chronic 

bronchitis (CB) and cardiovascular disease, for which we are able to quantify changes in the 

incidence of nonfatal heart attacks. To capture these important benefits in the measure of 

effectiveness, they must first be converted into a life-year equivalent so that they can be 

combined with the direct gains in life expectancy. 

For the cost effectiveness analyses for the PM and O3 NAAQS RIAs, we developed estimates of 

the QALYs gained from reductions in the incidence of CB and nonfatal heart attacks associated 

with reductions in ambient PM2.5. In general, QALY calculations require four elements: 

1. the estimated change in incidence of the health condition, 

2. the duration of the health condition, 

3. the quality-of-life weight with the health condition, and 

4. the quality-of-life weight without the health condition (i.e., the baseline health state). 

The first element is derived using the health impact function approach. The second element is 

based on the medical literature for each health condition. The third and fourth elements are 

derived from the medical cost-effectiveness and cost-utility literature. In the following two 

subsections, we discuss the choices of elements for CB and nonfatal heart attacks. 

The preferred source of quality-of-life weights are those based on community preferences, rather 

than patient or clinician ratings (Gold et al., 1996). Several methods are used to estimate qualityof-life weights. These include rating scale, standard gamble, time trade-off, and person trade-off 

approaches (Gold, Stevenson, and Fryback, 2002). Only the standard gamble approach is 

completely consistent with utility theory. However, the time trade-off method has also been 

widely applied in eliciting community preferences (Gold, Stevenson, and Fryback, 2002). 

Quality-of-life weights can be directly elicited for individual specific health states or for a more 

general set of activity restrictions and health states that can then be used to construct QALY 

weights for specific conditions (Horsman et al., 2003; Kind, 1996). For this analysis, we used 

weights based on community-based preferences, using time trade-off or standard gamble when 

available. In some cases, we used patient or clinician ratings when no community preferencebased weights were available. Sources for weights are discussed in more detail below. Table 8B12 summarizes the key inputs for calculating QALYs associated with chronic health endpoints. 

8-85 
Final Regulatory Impact Analysis 

Table 8B-12. Summary of Key Parameters Used in QALY Calculations for Chronic Disease 

Endpoints 

Parameter Value(s) Source(s) 

Discount rate 0.03 (0.07 

sensitivity 

analysis) 

Gold et al. (1996), U.S. EPA (2000), U.S. OMB (2003) 

Quality of life preference 

score for chronic 

bronchitis 

0.5 – 0.7 Triangular distribution centered at 0.7 with upper bound at 

0.9 (Vos, 1999a) (slightly better than a mild/moderate case) 

and a lower bound at 0.5 (average weight for a severe case 

based on Vos [1999a] and Smith and Peske [1994]) 

Duration of acute phase 

of acute myocardial 

infarction (AMI) 

5.5 days – 22 

days 

Uniform distribution with lower bound based on average 

length of stay for an AMI (AHRQ, 2000) and upper bound 

based on Vos (1999b). 

Probability of CHF post 

AMI 

0.2 Vos, 1999a (WHO Burden of Disease Study, based on 

Cowie et al., 1997) 

Probability of angina post 

AMI 

0.51 American Heart Association, 2003 

(Calculated as the population with angina divided by the 

total population with heart disease) 

Quality-of-life preference 

score for post-AMI with 

CHF (no angina) 

0.80 – 0.89 Uniform distribution with lower bound at 0.80 (Stinnett et 

al., 1996) and upper bound at 0.89 (Kuntz et al., 1996). 

Both studies used the time trade-off elicitation method. 

Quality-of-life preference 

score for post-AMI with 

CHF and angina 

0.76 – 0.85 Uniform distribution with lower bound at 0.76 (Stinnett et 

al., 1996, adjusted for severity) and upper bound at 0.85 

(Kuntz et al., 1996). Both studies used the time trade-off 

elicitation method. 

Quality-of-life preference 

score for post-AMI with 

angina (no CHF) 

0.7 – 0.89 Uniform distribution with lower bound at 0.7, based on the 

standard gamble elicitation method (Pliskin, Stason, and 

Weinstein, 1981) and upper bound at 0.89, based on the 

time trade-off method (Kuntz et al., 1996). 

Quality-of-life preference 

score for post-AMI (no 

angina, no CHF) 

0.93 Only one value available from the literature. Thus, no 

distribution is specified. Source of value is Kuntz et al. 

(1996). 

8B.4.5.1 Calculating QALYs Associated with Reductions in the Incidence of Chronic Bronchitis 

CB is characterized by mucus in the lungs and a persistent wet cough for at least 3 months a year 

for several years in a row. CB affects an estimated 5 percent of the U.S. population (American 

Lung Association, 1999). For gains in quality of life resulting from reduced incidences of PMinduced CB, discounted QALYs are calculated as 

* CB DISCOUNTED QALYGAINED = ∑ΔCBi × Di × (wi − wi )

i 

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 Cost-Benefit Analysis 

where )CBi is the number of incidences of CB avoided in age interval i, wi is the average QALY 

weight for the ith age interval, wi

CB is the QALY weight associated with CB in the ith age 

interval, and Di 

* is the discounted duration of life with CB for individuals with onset of disease in 

Di 

the ith age interval, equal to ∫ e−rtdt , where Di is the duration of life with CB for individuals 

0 with onset of disease the ith age interval. 

A limited number of studies have estimated the impact of air pollution on new incidences of CB. 

Schwartz (1993) and Abbey et al. (1995) provide evidence that long-term PM exposure gives 

rise to the development of CB in the United States. Only the Abbey et al. (1995) study was used, 

because it is the only study focusing on the relationship between PM2.5 and new incidences of 

CB. The number of cases of CB in each age interval was derived by applying the impact 

function from Abbey et al. (1995) to the population in each age interval with the appropriate 

baseline incidence rate.9

 The effect estimate from the Abbey et al. (1995) study is 0.0137, 

which, based on the logistic specification of the model, is equivalent to a relative risk of 1.15 for 

a 10 :g change in PM2.5. Table 8B-13 presents the estimated reduction in new incidences of CB 

associated with the Final SSI & RME Rule in 2020 and 2030. 

CB is assumed to persist for the remainder of an affected individual’s lifespan. Duration of CB 

will thus equal life expectancy conditioned on having CB. CDC has estimated that COPD (of 

which CB is one element) results in an average loss of life years equal to 4.26 per COPD death, 

relative to a reference life expectancy of 75 years (CDC, 2003). Thus, we subtracted 4.26 from 

the remaining life expectancy for each age group, up to age 75. For age groups over 75, we 

applied the ratio of 4.26 to the life expectancy for the 65 to 74 year group (0.237) to the life 

expectancy for the 75 to 84 and 85 and up age groups to estimate potential life years lost and 

then subtracted that value from the base life expectancy. 

9

 Prevalence rates for CB were obtained from the 1999 National Health Interview Survey 

(American Lung Association, 2002). Prevalence rates were available for three age groups: 18– 

44, 45–64, and 65 and older. Prevalence rates per person for these groups were 0.0367 for 18– 

44, 0.0505 for 45–64, and 0.0587 for 65 and older. The incidence rate for new cases of CB 

(0.00378 per person) was taken directly from Abbey et al. (1995). 

8-87 
Final Regulatory Impact Analysis 

Table 8B-13. Estimated Reduction in Incidence of Chronic Bronchitis Under the Final SSI & RME 

Rule in 2020 and 2030 

Reduction in PM2.5-Related Chronic Bronchitis 

(90% CI)* 

Age Interval 2020 2030 

27 - 34 18 

(3 - 33) 

22 

(4 - 40) 

35 - 44 15 

(3 - 28) 

26 

(5 - 48) 

45 - 54 14 

(3 - 26) 

22 

(4 - 40) 

55 - 64 16 

(3 - 28) 

22 

(4 - 40) 

65 - 74 11 

(2 - 19) 

21 

(4 - 38) 

75 - 84 6 

(1 - 11) 

12 

(2 - 22) 

85+ 3 

(1 - 5) 

4 

(1 - 8) 

Total: 84 

(16 - 150) 

130 

(24 - 240) 

*90 percent confidence or credible intervals (CIs) are based on the uncertainty 

about the coefficient in the mortality C-R functions. All estimates rounded to 

two significant figures. 

Quality of life with chronic lung diseases has been examined in several studies. In an analysis of 

the impacts of environmental exposures to contaminants, de Hollander et al. (1999) assigned a 

weight of 0.69 to years lived with CB. This weight was based on physicians’ evaluations of 

health states similar to CB. Salomon and Murray (2003) estimated a pooled weight of 0.77 

based on visual analogue scale, time trade-off, standard gamble, and person trade-off techniques 

applied to a convenience sample of health professionals. The Harvard Center for Risk Analysis 

catalog of preference scores reports a weight of 0.40 for severe COPD, with a range from 0.2 to 

0.8, based on the judgments of the study’s authors (Bell et al., 2001). The Victoria Burden of 

Disease (BoD) study used a weight of 0.47 for severe COPD and 0.83 for mild to moderate 

COPD, based on an analysis by Stouthard et al. (1997) of chronic diseases in Dutch populations 

(Vos, 1999a). Based on the recommendations of Gold et al. (1996), quality-of-life weights based 

on community preferences are preferred for CEA of interventions affecting broad populations. 

Use of weights based on health professionals is not recommended. It is not clear from the 

Victoria BoD study whether the weights used for COPD are based on community preferences or 

judgments of health professionals. The Harvard catalog score is clearly identified as based on 

author judgment. Given the lack of a clear preferred weight, we selected a triangular distribution 

centered at 0.7 with an upper bound at 0.9 (slightly better than a mild/moderate case defined by 

the Victoria BoD study) and a lower bound at 0.5 based on the Victoria BoD study. We will 

need additional empirical data on quality of life with chronic respiratory diseases based on 

community preferences to improve our estimates. 

8-88 
 Cost-Benefit Analysis 

Selection of a reference weight for the general population without CB is somewhat uncertain. It 

is clear that the general population is not in perfect health; however, there is some uncertainty as 

to whether individuals’ ratings of health states are in reference to a perfect health state or to a 

generally achievable “normal” health state given age and general health status. The U.S. Public 

Health Service Panel on Cost Effectiveness in Health and Medicine recommends that “since 

lives saved or extended by an intervention will not be in perfect health, a saved life year will 

count as less than 1 full QALY” (Gold et al., 1996). Following Carrothers, Evans, and Graham 

(2002), we assumed that the reference weight for the general population without CB is 0.95. To 

allow for uncertainty in this parameter, we assigned a triangular distribution around this weight, 

bounded by 0.9 and 1.0. Note that the reference weight for the general population is used solely 

to determine the incremental quality-of-life improvement applied to the duration of life that 

would have been lived with the chronic disease. For example, if CB has a quality-of-life weight 

of 0.7 relative to a reference quality-of-life weight of 0.9, then the incremental quality-of-life 

improvement in 0.2. If the reference quality-of-life weight is 0.95, then the incremental qualityof-life improvement is 0.25. As noted above, the population is assumed to have a reference 

weight of 1.0 for all life years gained due to mortality risk reductions. 

We present discounted QALYs over the duration of the lifespan with CB using a 3 percent 

discount rate. Based on the assumptions defined above, we used Monte Carlo simulation 

methods as implemented in the Crystal BallTM software program to develop the distribution of 

QALYs gained per incidence of CB for each age interval.10 Based on the assumptions defined 

above, the mean 3 percent discounted QALY gained per incidence of CB for each age interval 

along with the 95 percent confidence interval resulting from the Monte Carlo simulation is 

presented in Table 8B-14. Table 8B-14 presents both the undiscounted and discounted QALYs 

gained per incidence, using a 3 percent discount rate. 

10 Monte Carlo simulation uses random sampling from distributions of parameters to characterize 

the effects of uncertainty on output variables. For more details, see Gentile (1998). 

8-89 
Final Regulatory Impact Analysis 

Table 8B-14. QALYs Gained per Avoided Incidence of CB 

Age Interval 

Start Age End Age Undiscounted Discounted (3%) 

25 34 12.15 

(4.40-19.95) 

6.52 

(2.36-10.71) 

35 44 9.91 

(3.54-16.10) 

5.94 

(2.12-9.66) 

45 54 7.49 

(2.71-12.34) 

5.03 

(1.82-8.29) 

55 64 5.36 

(1.95-8.80) 

4.03 

(1.47-6.61) 

65 74 3.40 

(1.22-5.64) 

2.84 

(1.02-4.71) 

75 84 2.15 

(0.77-3.49) 

1.92 

(0.69-3.13) 

85+ 0.79 

(0.27-1.29) 

0.77 

(0.26-1.25) 

QALYs Gained per Incidencea 

a

 Mean of Monte Carlo generated distribution; 95% confidence interval presented in parentheses. 

8B.4.5.2 Calculating QALYs Associated with Reductions in the Incidence of Nonfatal 

Myocardial Infarctions 

Nonfatal heart attacks, or acute myocardial infarctions, require more complicated calculations to 

derive estimates of QALY impacts. The actual heart attack, which results when an area of the 

heart muscle dies or is permanently damaged because of oxygen deprivation, and subsequent 

emergency care are of relatively short duration. Many heart attacks result in sudden death. 

However, for survivors, the long-term impacts of advanced coronary heart disease (CHD) are 

potentially of long duration and can result in significant losses in quality of life and life 

expectancy. 

In this phase of the analysis, we did not independently estimate the gains in life expectancy 

associated with reductions in nonfatal heart attacks. Based on recommendations from the SABHES, we assumed that all gains in life expectancy are captured in the estimates of reduced 

mortality risk provided by the Pope et al. (2002) analysis. We estimated only the change in 

quality of life over the period of life affected by the occurrence of a heart attack. This may 

understate the QALY impacts of nonfatal heart attacks but ensures that the overall QALY impact 

estimates across endpoints do not double-count potential life-year gains. 

Our approach adapts a CHD model developed for the Victoria Burden of Disease study (Vos, 

1999b). This model accounts for the lost quality of life during the heart attack and the possible 

health states following the heart attack. Figure 8B-1 shows the heart attack QALY model in 

diagrammatic form. 

The total gain in QALYs is calculated as: 

8-90 
 Cost-Benefit Analysis 

DISCOUNTED AMI QALY GAINED =

*AMI AMI *PostAMI postAMI ∑ Δ AMI × D × (w − w ) + ∑ ∑

4 

i i i i Δ AMI i j ij × p D × (w i ij − w ) i i j=1 

where )AMIi is the number of nonfatal acute myocardial infarctions avoided in age interval i, 

wi

AMI is the QALY weight associated with the acute phase of the AMI, pj is the probability of 

being in the jth post-AMI status, wij

postAMI is the QALY weight associated with post-AMI health 

= e status j, wi is the average QALY weight for age interval i, Di 

*AMI ∫t

D 

=1 

i

AMI 

−rt dt , the discounted 

value of D = e

i

AMI , the duration of the acute phase of the AMI, and Di 

*postAMI ∫t 

D

=1 

i

postAMI 

−rt dt , is the 

discounted value of Dij

PostAMI , the duration of post-AMI health status j. 

8-91 
Final Regulatory Impact Analysis 

Acute Treatment Stage Chronic Post-AMI Follow up Stage 

Post AMI QALY with Angina and CHF 

Nonfatal AMI 

Congestive Heart Failure 

Yes 

No 

Angina 

Angina 

Yes 

No 

No 

Yes 

Post AMI QALY with CHF without Angina 

Post AMI QALY with Angina without CHF 

Post AMI QALY without Angina or CHF 

Figure 8B-1. Decision Tree Used in Modeling Gains in QALYs from Reduced Incidence of 

Nonfatal Acute Myocardial Infarctions 

Nonfatal heart attacks have been linked with short-term exposures to PM2.5 in the United States 

(Peters et al., 2001) and other countries (Poloniecki et al., 1997). We used a recent study by 

Peters et al. (2001) as the basis for the impact function estimating the relationship between PM2.5 

and nonfatal heart attacks. Peters et al. is the only available U.S. study to provide a specific 

estimate for heart attacks. Other studies, such as Samet et al. (2000) and Moolgavkar (2000), 

show a consistent relationship between all cardiovascular hospital admissions, including for 

nonfatal heart attacks, and PM. Given the lasting impact of a heart attack on longer-term health 

costs and earnings, we chose to provide a separate estimate for nonfatal heart attacks based on 

the single available U.S. effect estimate. The finding of a specific impact on heart attacks is 

consistent with hospital admission and other studies showing relationships between fine particles 

and cardiovascular effects both within and outside the United States. These studies provide a 

weight of evidence for this type of effect. Several epidemiologic studies (Liao et al., 1999; Gold 

et al., 2000; Magari et al., 2001) have shown that heart rate variability (an indicator of how much 

8-92 
 Cost-Benefit Analysis 

the heart is able to speed up or slow down in response to momentary stresses) is negatively 

related to PM levels. Heart rate variability is a risk factor for heart attacks and other CHDs 

(Carthenon et al., 2002; Dekker et al., 2000; Liao et al., 1997, Tsuji et al., 1996). As such, 

significant impacts of PM on heart rate variability are consistent with an increased risk of heart 

attacks. 

The number of avoided nonfatal AMI in each age interval was derived by applying the impact 

function from Peters et al. (2001) to the population in each age interval with the appropriate 

baseline incidence rate.11 The effect estimate from the Peters et al. (2001) study is 0.0241, 

which, based on the logistic specification of the model, is equivalent to a relative risk of 1.27 for 

a 10 :g change in PM2.5. Table 8B-15 presents the estimated reduction in nonfatal AMI 

associated with the Final SSI & RME Rule in 2020 and 2030. 

Table 8B-15. Estimated Reduction in Nonfatal Acute Myocardial Infarctions Under the Final SSI & 

RME Rule in 2020 and 2030 

Reduction in PM2.5-Related Acute Myocardial Infarction 

(90% CI)* 

Age Interval 2020 2030 

18 - 24 0 

(0 - 0) 

0 

(0 - 0) 

25 - 29 1 

(1 - 2) 

2 

(1 - 3) 

35 - 44 10 

(5 - 14) 

16 

(9 - 23) 

45 - 54 29 

(16 - 42) 

43 

(23 - 63) 

55 - 64 68 

(37 - 98) 

99 

(53 - 140) 

65 - 74 94 

(51 - 140) 

160 

(84 - 230) 

75 - 84 48 

(26 - 69) 

140 

(76 - 210) 

85+ 42 

(23 - 62) 

67 

(36 - 98) 

Total: 290 

(160 - 420) 

530 

(280 - 770) 

*90 percent confidence or credible intervals (CIs) are based on the uncertainty 

about the coefficient in the mortality C-R functions. All estimates rounded to 

two significant figures. 

11 Daily nonfatal myocardial infarction incidence rates per person were obtained from the 1999 

National Hospital Discharge Survey (assuming all diagnosed nonfatal AMI visit the hospital). 

Age-specific rates for four regions are used in the analysis. Regional averages for populations 18 

and older are 0.0000159 for the Northeast, 0.0000135 for the Midwest, 0.0000111 for the South, 

and 0.0000100 for the West. 

8-93 
Final Regulatory Impact Analysis 

Acute myocardial infarction results in significant loss of quality of life for a relatively short 

duration. The WHO Global Burden of Disease study, as reported in Vos (1999b), assumes that 

the acute phase of an acute myocardial infarction lasts for 0.06 years, or around 22 days. An 

alternative assumption is the acute phase is characterized by the average length of hospital stay 

for an AMI in the United States, which is 5.5 days, based on data from the Agency for 

Healthcare Research and Quality’s Healthcare Cost and Utilization Project (HCUP).12 We 

assumed a distribution of acute phase duration characterized by a uniform distribution between 

5.5 and 22 days, noting that due to earlier discharges and in-home therapy available in the United 

States, duration of reduced quality of life may continue after discharge from the hospital. In the 

period during and directly following an AMI (the acute phase), we assigned a quality of life 

weight equal to 0.605, consistent with the weight for the period in treatment during and 

immediately after an attack (Vos, 1999b). 

During the post-AMI period, a number of different health states can determine the loss in quality 

of life. We chose to classify post-AMI health status into four states defined by the presence or 

absence of angina and congestive heart failure (CHF). This makes a very explicit assumption 

that without the occurrence of an AMI, individuals would not experience either angina or CHF. 

If in fact individuals already have CHF or angina, then the quality of life gained will be 

overstated. We do not have information about the percentage of the population have been 

diagnosed with angina or CHF with no occurrence of an AMI. Nor do we have information on 

what proportion of the heart attacks occurring due to PM exposure are first heart attacks versus 

repeat attacks. Probabilities for the four post-AMI health states sum to one. 

Given the occurrence of a nonfatal AMI, the probability of congestive heart failure is set at 0.2, 

following the heart disease model developed by Vos (1999b). The probability is based on a 

study by Cowie et al. (1997), which estimated that 20 percent of those surviving AMI develop 

heart failure, based on an analysis of the results of the Framingham Heart Study. 

The probability of angina is based on the prevalence rate of angina in the U.S. population. Using 

data from the American Heart Association, we calculated the prevalence rate for angina by 

dividing the estimated number of people with angina (6.6 million) by the estimated number of 

people with CHD of all types (12.9 million). We then assumed that the prevalence of angina in 

the population surviving an AMI is similar to the prevalence of angina in the total population 

with CHD. The estimated prevalence rate is 51 percent, so the probability of angina is 0.51. 

Combining these factors leads to the probabilities for each of the four health states as follows: 

I. Post AMI with CHF and angina = 0.102 

II. Post AMI with CHF without angina = 0.098 

III. Post AMI with angina without CHF = 0.408 

IV. Post AMI without angina or CHF = 0.392 

12 Average length of stay estimated from the HCUP data includes all discharges, including those 

due to death. As such, the 5.5-day average length of stay is likely an underestimate of the 

average length of stay for AMI admissions where the patient is discharged alive. 

8-94 
 Cost-Benefit Analysis 

Duration of post-AMI health states varies, based in part on assumptions regarding life 

expectancy with post-AMI complicating health conditions. Based on the model used for 

established market economies (EME) in the WHO Global Burden of Disease study, as reported 

in Vos (1999b), we assumed that individuals with CHF have a relatively short remaining life 

expectancy and thus a relatively short period with reduced quality of life (recall that gains in life 

expectancy are assumed to be captured by the cohort estimates of reduced mortality risk). 

Table 8B-16 provides the duration (both discounted and undiscounted) of CHF assumed for postAMI cases by age interval. 

Table 8B-16. Assumed Duration of Congestive Heart Failure 

Age Interval Duration of Heart Failure (years) 

Start Age End Age Undiscounted Discounted (3%) 

18 24 7.11 6.51 

25 34 6.98 6.40 

35 44 6.49 6.00 

45 54 5.31 4.99 

55 64 1.96 1.93 

65 74 1.71 1.69 

75 84 1.52 1.50 

85+ 1.52 1.50 

Duration of health states without CHF is assumed to be equal to the life expectancy of 

individuals conditional on surviving an AMI. Ganz et al. (2000) note that “Because patients with 

a history of myocardial infarction have a higher chance of dying of CHD that is unrelated to 

recurrent myocardial infarction (for example, arrhythmia), this cohort has a higher risk for death 

from causes other than myocardial infarction or stroke than does an unselected population.” 

They go on to specify a mortality risk ratio of 1.52 for mortality from other causes for the cohort 

of individuals with a previous (nonfatal) AMI. The risk ratio is relative to all-cause mortality for 

an age-matched unselected population (i.e., general population). We adopted the same ratios and 

applied them to each age-specific all-cause mortality rate to derive life expectancies (both 

discounted and undiscounted) for each age group after an AMI, presented in Table 8B-17. These 

life expectancies were then used to represent the duration of non-CHF post-AMI health states (III 

and IV). 

8-95 
Final Regulatory Impact Analysis 

Table 8B-17. Assumed Duration of Non-CHF Post-AMI Health States 

Age Interval Post-AMI Years of Life Expectancy (non-CHF) 

Start Age End Age Undiscounted Discounted (3%) 

18 24 55.5 27.68 

25 34 46.1 25.54 

35 44 36.8 22.76 

45 54 27.9 19.28 

55 64 19.8 15.21 

65 74 12.8 10.82 

75 84 7.4 6.75 

85+ 3.6 3.47 

For the four post-AMI health states, we used QALY weights based on preferences for the 

combined conditions characterizing each health state. A number of estimates of QALY weights 

are available for post-AMI health conditions. 

The first two health states are characterized by the presence of CHF, with or without angina. 

The Harvard Center for Risk Analysis catalog of preference scores provides several specific 

weights for CHF with and without mild or severe angina and one set specific to post-AMI CHF. 

Following the Victoria Burden of Disease model, we assumed that most cases of angina will be 

treated and thus kept at a mild to moderate state. We thus focused our selection on QALY 

weights for mild to moderate angina. The Harvard database includes two sets of community 

preference-based scores for CHF (Stinnett et al., 1996; Kuntz et al., 1996). The scores for CHF 

with angina range from 0.736 to 0.85. The lower of the two scores is based on angina in general 

with no delineation by severity. Based on the range of the scores for mild to severe cases of 

angina in the second study, one can infer that an average case of angina has a score around 0.96 

of the score for a mild case. Applying this adjustment raises the lower end of the range of 

preference scores for a mild case of angina to 0.76. We selected a uniform distribution over the 

range 0.76 to 0.85 for CHF with mild angina, with a midpoint of 0.81. The same two studies in 

the Harvard catalog also provide weights for CHF without angina. These scores range from 

0.801 to 0.89. We selected a uniform distribution over this range, with a midpoint of 0.85. 

The third health state is characterized by angina, without the presence of CHF. The Harvard 

catalog includes five sets of community preference-based scores for angina, one that specifies 

scores for both mild and severe angina (Kuntz et al., 1996), one that specifies mild angina only 

(Pliskin, Stason, and Weinstein, 1981), one that specifies severe angina only (Cohen, Breall, and 

Ho, 1994), and two that specify angina with no severity classification (Salkeld, Phongsavan, and 

Oldenburg, 1997; Stinnett et al., 1996). With the exception of the Pliskin, Stason, and Weinstein 

score, all of the angina scores are based on the time trade-off method of elicitation. The Pliskin, 

Stason, and Weinstein score is based on the standard gamble elicitation method. The scores for 

the nonspecific severity angina fall within the range of the two scores for mild angina 

specifically. Thus, we used the range of mild angina scores as the endpoints of a uniform 

distribution. The range of mild angina scores is from 0.7 to 0.89, with a midpoint of 0.80. 

8-96 
 Cost-Benefit Analysis 

For the fourth health state, characterized by the absence of CHF and/or angina, there is only one 

relevant community preference score available from the Harvard catalog. This score is 0.93, 

derived from a time trade-off elicitation (Kuntz et al., 1996). Insufficient information is 

available to provide a distribution for this weight; therefore, it is treated as a fixed value. 

Similar to CB, we assumed that the reference weight for the general population without AMI is 

0.95. To allow for uncertainty in this parameter, we assigned a triangular distribution around this 

weight, bounded by 0.9 and 1.0. 

Based on the assumptions defined above, we used Monte Carlo simulation methods as 

implemented in the Crystal BallTM software program to develop the distribution of QALYs 

gained per incidence of nonfatal AMI for each age interval. For the Monte Carlo simulation, all 

distributions were assumed to be independent. The mean QALYs gained per incidence of 

nonfatal AMI for each age interval is presented in Table 8B-18, along with the 95 percent 

confidence interval resulting from the Monte Carlo simulation. Table 8B-18 presents both the 

undiscounted and discounted QALYs gained per incidence. 

Table 8B-18. QALYs Gained per Avoided Nonfatal Myocardial Infarction 

Age Interval QALYs Gained per Incidencea 

Start Age End Age Undiscounted Discounted (3%) 

18 24 4.18 

(1.24-7.09) 

2.17 

(0.70-3.62) 

25 34 3.48 

(1.09-5.87) 

2.00 

(0.68-3.33) 

35 44 2.81 

(0.88-4.74) 

1.79 

(0.60-2.99) 

45 54 2.14 

(0.67-3.61) 

1.52 

(0.51-2.53) 

55 64 1.49 

(0.42-2.52) 

1.16 

(0.34-1.95) 

65 74 0.97 

(0.30-1.64) 

0.83 

(0.26-1.39) 

75 84 0.59 

(0.20-0.97) 

0.54 

(0.19-0.89) 

85+ 0.32 

(0.13-0.50) 

0.31 

(0.13-0.49) a

 Mean of Monte Carlo generated distribution; 95% confidence interval presented in parentheses. 

8B.4.6 Aggregating Life Expectancy and Quality-of-Life Gains 

Given the estimates of changes in life expectancy and quality of life, the next step is to aggregate 

life expectancy and quality-of-life gains to form an effectiveness measure that can be compared 

to costs to develop cost-effectiveness ratios. This section discusses the proper characterization of 

the combined effectiveness measure for the denominator of the cost-effectiveness ratio. 

8-97 
Final Regulatory Impact Analysis 

To develop an integrated measure of changes in health, we simply sum together the gains in life 

years from reduced mortality risk in each age interval with the gains in QALYs from reductions 

in incidence of chronic morbidity endpoints (CB and acute myocardial infarctions). The 

resulting measure of effectiveness then forms the denominator in the cost-effectiveness ratio. 

This combined measure of effectiveness is not a QALY measure in a strict sense, because we 

have not adjusted life-expectancy gains for preexisting health status (quality of life). It is 

however, an effectiveness measure that adds a scaled morbidity equivalent to the standard life 

years calculation. Thus, we term the aggregate measure morbidity inclusive life years, or 

MILYs. Alternatively, the combined measure could be considered as QALYs with an 

assumption that the community preference weight for all life-expectancy gains is 1.0. If one 

considers that this weight might be considered to be a “fair” treatment of those with preexisting 

disabilities, the effectiveness measure might be termed “fair QALY” gained. However, this 

implies that all aspects of fairness have been addressed, and there are clearly other issues with 

the fairness of QALYs (or other effectiveness measures) that are not addressed in this simple 

adjustment. The MILY measure violates some of the properties used in deriving QALY weights, 

such as linear substitution between quality of life and quantity of life. However, in aggregating 

life expectancy and quality-of-life gains, it merely represents an alternative social weighting that 

is consistent with the spirit of the recent OMB guidance on CEA. The guidance notes that 

“fairness is important in the choice and execution of effectiveness measures” (OMB, 2003). The 

resulting aggregate measure of effectiveness will not be consistent with a strict utility 

interpretation of QALYs; however, it may still be a useful index of effectiveness. 

Applying the life expectancies and distributions of QALYs per incidence for CB and AMI to 

estimated distributions of incidences yields distributions of life expectancy and QALYs gained 

under the Final SSI & RME Rule. These distributions reflect both the quantified uncertainty in 

estimates of avoided incidence and the quantified uncertainty in QALYs gained per incidence 

avoided. 

Tables 8B-19 and 8B-20 present the discounted life years, QALYs, and MILYs gained, based on 

each combination of O3-mortality study, PM2.5-mortality study, and life expectancy assumption 

for O3-related life years saved used for the analysis, using a 3 percent discount rate, for 2020 and 

2030, respectively. Tables 8B-21 and 8B-22 present the corresponding results using a 7 percent 

discount rate. 

8-98 
 

Table 8B-19. Estimated Gains in Discounted MILYs Under the Final SSI & RME Rule in 2020, Using a 3 Percent Dis

O3 Mortality Study PM2.5 Mortality Study Life Expectancy Assumption for O3 - Related Mortality 

(95% CI) 

O3-Related Life Years 

Gained from Mortality 

Risk 

Reductions 

(95% CI) 

PM2.5-Related Life 

Years Gained from 

Mortality Risk 

Reductions 

(95% CI) 

QALYs Gained from 

Reductions in PM2.5-

Related Chronic 

Bronchitis 

QALY

Redu

Rela

Myoca

Bell et al. (2004) Pope et al. (2002) General Population 500 (200 - 800) Bell et al. (2004) Pope et al. (2002) Subpopulation with Average COPD 400 (100 - 600) 

Bell et al. (2004) Pope et al. (2002) Subpopulation with Severe COPD 200 (100 - 300) 1,100 

Levy et al. (2005) Pope et al. (2002) General Population 2,200 (1,500 - 2,900) (400 - 1,800) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Average COPD 1,700 (1,200 - 2,200) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Severe COPD 1,000 (700 - 1,300) 390 

Bell et al. (2004) Laden et al. (2006) General Population 500 (200 - 800) (50 - 900) 

Bell et al. (2004) Laden et al. (2006) Subpopulation with Average COPD 400 (100 - 600) 

Bell et al. (2004) Laden et al. (2006) Subpopulation with Severe COPD 200 (100 - 300) 2,600 

Levy et al. (2005) Laden et al. (2006) General Population 2,200 (1,500 - 2,900) (1,400 - 4,000) 

Levy et al. (2005) Laden et al. (2006) Subpopulation with Average COPD 1,700 (1,200 - 2,200) Levy et al. (2005) Laden et al. (2006) Subpopulation with Severe COPD 1,000 (700 - 1,300) 

*Life years, QALYs, and MILYs are discounted back to 2020. 95% confidence or credible intervals (CIs) around the point estimates are based on the unc

estimates (coefficients) in the C-R functions and, for QALYs and MILYs, the uncertainty surrounding the quality of life weights. All estimates rounded to t

8-99
Final Regulatory Impact Analysis 

Table 8B-20. Estimated Gains in Discounted MILYs Under the Final SSI & RME Rule in 2030, Using a 3 Percent Dis

O3 Mortality Study PM2.5 Mortality Study Life Expectancy Assumption for O3 - Related Mortality 

(95% CI) 

O3-Related Life Years 

Gained from Mortality 

Risk 

Reductions 

(95% CI) 

PM2.5-Related Life 

Years Gained from 

Mortality Risk 

Reductions 

(95% CI) 

QALYs Gained from 

Reductions in PM2.5-

Related Chronic 

Bronchitis 

QALY

Redu

Rela

Myoca

Bell et al. (2004) Pope et al. (2002) General Population 700 (200 - 1,200) Bell et al. (2004) Pope et al. (2002) Subpopulation with Average COPD 600 (200 - 900) 

Bell et al. (2004) Pope et al. (2002) Subpopulation with Severe COPD 300 (100 - 500) 2,200 

Levy et al. (2005) Pope et al. (2002) General Population 3,500 (2,400 - 4,600) (900 - 3,500) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Average COPD 2,700 (1,800 - 3,500) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Severe COPD 1,500 (1,000 - 1,900) 590 

Bell et al. (2004) Laden et al. (2006) General Population 700 (200 - 1,200) (80 - 1,400) (Bell et al. (2004) Laden et al. (2006) Subpopulation with Average COPD 600 (200 - 900) 

Bell et al. (2004) Laden et al. (2006) Subpopulation with Severe COPD 300 (100 - 500) 5,000 

Levy et al. (2005) Laden et al. (2006) General Population 3,500 (2,400 - 4,600) (2,700 - 7,000) 

Levy et al. (2005) Laden et al. (2006) Subpopulation with Average COPD 2,700 (1,800 - 3,500) Levy et al. (2005) Laden et al. (2006) Subpopulation with Severe COPD 1,500 (1,000 - 1,900) *Life years, QALYs, and MILYs are discounted back to 2030. 95% confidence or credible intervals (CIs) around the point estimates are based on the unc

estimates (coefficients) in the C-R functions and, for QALYs and MILYs, the uncertainty surrounding the quality of life weights. All estimates rounded to t

8-100
 

Table 8B-21. Estimated Gains in Discounted MILYs Under the Final SSI & RME Rule in 2020, Using a 7 Percent Dis

O3 Mortality Study PM2.5 Mortality Study Life Expectancy Assumption for O3 - Related Mortality 

(95% CI) 

O3-Related Life Years 

Gained from Mortality 

Risk 

Reductions 

(95% CI) 

PM2.5-Related Life 

Years Gained from 

Mortality Risk 

Reductions 

(95% CI) 

QALYs Gained from 

Reductions in PM2.5-

Related Chronic 

Bronchitis 

QALY

Redu

Rela

Myoc

Bell et al. (2004) Pope et al. (2002) General Population 360 

(120 - 600) 

Bell et al. (2004) Pope et al. (2002) Subpopulation with Average COPD 290 

(90 - 500) 

Bell et al. (2004) Pope et al. (2002) Subpopulation with Severe COPD 170 800 

(50 - 280) 

Levy et al. (2005) Pope et al. (2002) General Population 1,700 (300 - 1,200) 

(1,200 - 2,200) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Average COPD 1,400 

(900 - 1,800) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Severe COPD 800 300 

(600 - 1,100) 

Bell et al. (2004) Laden et al. (2006) General Population 360 (30 - 600) 

(120 - 600) 

Bell et al. (2004) Laden et al. (2006) Subpopulation with Average COPD 290 

(90 - 500) 

Bell et al. (2004) Laden et al. (2006) Subpopulation with Severe COPD 170 1,800 

(50 - 280) 

Levy et al. (2005) Laden et al. (2006) General Population 1,700 (1,000 - 2,500) 

(1,200 - 2,200) 

Levy et al. (2005) Laden et al. (2006) Subpopulation with Average COPD 1,400 

(900 - 1,800) 

Levy et al. (2005) Laden et al. (2006) Subpopulation with Severe COPD 800 

(600 - 1,100) 

*Life years, QALYs, and MILYs are discounted back to 2020. 95% confidence or credible intervals (CIs) around the point estimates are based on the uncestimates (coefficients) in the C-R functions and, for QALYs and MILYs, the uncertainty surrounding the quality of life weights. All estimates rounded to 

8-101
Final Regulatory Impact Analysis 

Table 8B-22. Estimated Gains in Discounted MILYs Under the Final SSI & RME Rule in 2030, Using a 7 Percent Dis

O3 Mortality Study PM2.5 Mortality Study Life Expectancy Assumption for O3 - Related Mortality 

(95% CI) 

O3-Related Life Years 

Gained from Mortality 

Risk 

Reductions 

(95% CI) 

PM2.5-Related Life 

Years Gained from 

Mortality Risk 

Reductions 

(95% CI) 

QALYs Gained from 

Reductions in PM2.5-

Related Chronic 

Bronchitis 

QALY

Redu

Rela

Myoc

Bell et al. (2004) Pope et al. (2002) General Population 590 

(190 - 1,000) 

Bell et al. (2004) Pope et al. (2002) Subpopulation with Average COPD 460 

(150 - 800) 

Bell et al. (2004) Pope et al. (2002) Subpopulation with Severe COPD 250 800 

(80 - 430) 

Levy et al. (2005) Pope et al. (2002) General Population 2,700 (300 - 1,200) 

(1,900 - 3,500) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Average COPD 2,100 

(1,500 - 2,800) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Severe COPD 1,200 400 

(800 - 1,600) 

Bell et al. (2004) Laden et al. (2006) General Population 590 (50 - 900) 

(190 - 1,000) 

Bell et al. (2004) Laden et al. (2006) Subpopulation with Average COPD 460 

(150 - 800) 

Bell et al. (2004) Laden et al. (2006) Subpopulation with Severe COPD 250 1,800 

(80 - 430) 

Levy et al. (2005) Laden et al. (2006) General Population 2,700 (1,000 - 2,500) 

(1,900 - 3,500) 

Levy et al. (2005) Laden et al. (2006) Subpopulation with Average COPD 2,100 

(1,500 - 2,800) 

Levy et al. (2005) Laden et al. (2006) Subpopulation with Severe COPD 1,200 

(800 - 1,600) 

*Life years, QALYs, and MILYs are discounted back to 2030. 95% confidence or credible intervals (CIs) around the point estimates are based on the uncestimates (coefficients) in the C-R functions and, for QALYs and MILYs, the uncertainty surrounding the quality of life weights. All estimates rounded to 

8-102
 Cost-Benefit Analysis 

8B.4.7 Estimating the Avoided Costs of Chronic Illness 

Construction of cost-effectiveness ratios requires estimates of effectiveness (in this case 

measured by lives saved, life years gained, or MILYs gained) in the denominator and estimates 

of costs in the numerator. As noted above (see Section 8B.3.1), our estimate of costs in the 

numerator is net of the avoided costs (cost savings) associated with the reductions in morbidity 

(Gold et al., 1996). Among the morbidity costs subtracted from the direct costs of controls in the 

numerator are the avoided costs of illness (COI) associated with PM2.5-related CB and nonfatal 

AMI. 

Avoided costs for CB and nonfatal AMI are based on estimates of lost earnings and medical 

costs.13 Using age-specific annual lost earnings and medical costs estimated by Cropper and 

Krupnick (1990) and a 3 percent discount rate, we estimated a lifetime present discounted value 

(in 2005$) due to CB of $179,305 for someone between the ages of 27 and 44; $116,892 for 

someone between the ages of 45 and 64; and $13,741 for someone over 65. The corresponding 

age-specific estimates of lifetime present discounted value (in 2005$) using a 7 percent discount 

rate are $102,300, $86,359, and $11,190, respectively. These estimates assumed that 1) lost 

earnings continue only until age 65, 2) medical expenditures are incurred until death, and 3) life 

expectancy is unchanged by CB. 

Because the costs associated with a myocardial infarction extend beyond the initial event itself, 

we consider costs incurred over several years. Using age-specific annual lost earnings estimated 

by Cropper and Krupnick (1990) and a 3 percent discount rate, we estimated a present 

discounted value in lost earnings (in 2005$) over 5 years due to a myocardial infarction of 

$10,389 for someone between the ages of 25 and 44, $15,313 for someone between the ages of 

45 and 54, and $88,508 for someone between the ages of 55 and 65. The corresponding agespecific estimates of lost earnings (in 2005$) using a 7 percent discount rate are $9,301, $13,709, 

and $79,241, respectively. Cropper and Krupnick (1990) do not provide lost earnings estimates 

for populations under 25 or over 65. Thus, we do not include lost earnings in the cost estimates 

for these age groups. 

Two estimates of the direct medical costs of myocardial infarction are used. The first estimate is 

from Wittels, Hay, and Gotto (1990), which estimated expected total medical costs of MI over 5 

years to be $51,211 (in 1986$) for people who were admitted to the hospital and survived 

hospitalization (there does not appear to be any discounting used). Using the CPI-U for medical 

care, the Wittels estimate is $135,667 in year 2005$. This estimated cost is based on a medical 

cost model, which incorporated therapeutic options, projected outcomes, and prices (using 

“knowledgeable cardiologists” as consultants). The model used medical data and medical 

13 Gold et al. (1996) recommend not including lost earnings in the cost-of-illness estimates, 

suggesting that in some cases, they may be already be counted in the effectiveness measures. 

However, this requires that individuals fully incorporate the value of lost earnings and reduced 

labor force participation opportunities into their responses to time-tradeoff or standard-gamble 

questions. For the purposes of this analysis and for consistency with the way costs-of-illness are 

calculated for the benefit-cost analysis, we have assumed that individuals do not incorporate lost 

earnings in responses to these questions. This assumption can be relaxed in future analyses with 

improved understanding of how lost earnings are treated in preference elicitations. 

8-103 
Final Regulatory Impact Analysis 

decision algorithms to estimate the probabilities of certain events and/or medical procedures 

being used. The second estimate is from Russell et al. (1998), which estimated first-year direct 

medical costs of treating nonfatal myocardial infarction of $15,540 (in 1995$), and $1,051 

annually thereafter. Converting to year 2005$, that would be $27,674 for a 5-year period (using 

a 3 percent discount rate). 

The two estimates from these studies are substantially different, and we have not adequately 

resolved the sources of differences in the estimates. Because the wage-related opportunity cost 

estimates from Cropper and Krupnick (1990) cover a 5-year period, we used estimates for 

medical costs that similarly cover a 5-year period. We used a simple average of the two 5-year 

estimates, or $81,671, and add it to the 5-year opportunity cost estimate. The resulting estimates 

are given in Table 8B-23. 

Table 8B-23. Estimated Costs Over a 5-Year Period (in 2005$) of a Nonfatal Myocardial Infarction 

Age of Onset Opportunity Cost1 Medical Cost2 Total Cost* 

0 - 24 

25 - 44 

45 - 54 

55 - 65 

> 65 

$0 

$10,389 

$15,313 

$88,508 

$0 

$81,671 

$81,671 

$81,671 

$81,671 

$81,671 

$81,671 

$92,060 

$96,984 

$170,179 

$81,671 1

 Positive opportunity costs are based on Cropper and Krupnick (1990), using a 3 percent 

discount rate. 

2

 An average of the 5-year costs estimated by Wittels, Hay, and Gotto (1990) and Russell et al. 

(1998). 

The total avoided COI by age group associated with the reductions in CB and nonfatal acute 

myocardial infarctions (using a 3 percent discount rate) is provided in Table 8B-24. The total 

avoided COI associated with the Final SSI & RME Rule (using a 3 percent discount rate) is 

about $42 million in 2020 and about $71 million in 2030. Note that these estimates do not 

include any direct avoided medical costs associated with premature mortality. Nor do they 

include any medical costs that occur more than 5 years from the onset of a nonfatal AMI. 

Therefore, they are likely underestimates of the true avoided COI associated with the Final SSI 

& RME Rule in 2020 and 2030. 

8-104 
 Cost-Benefit Analysis 

Table 8B-24. Avoided Costs of Illness Associated with Reductions in Chronic Bronchitis and 

Nonfatal Acute Myocardial Infarctions Under the Final SSI & RME Rule in 2020 and 

2030 

Avoided Cost of Illness (in millions of 2005$)* 

Age Interval 2020 2030 

Chronic Bronchitis Nonfatal Acute 

Myocardial Infarction Chronic Bronchitis Nonfatal Acute Myocardial Infarction 

18 - 24 

25 - 29 

35 - 44 

45 - 54 

55 - 64 

65 - 74 

75 - 84 

85+ 

---

$4.1 

$3.4 

$2.1 

$2.2 

$0.2 

$0.1 

$0.1 

$0.0 

$0.1 

$0.9 

$2.8 

$11.5 

$7.7 

$3.9 

$3.5 

---

$4.9 

$6.0 

$3.2 

$3.3 

$0.4 

$0.2 

$0.1 

$0.0 

$0.2 

$1.5 

$4.2 

$16.8 

$12.8 

$11.6 

$5.5 

Total: $12.1 $30.4 $18.1 $52.5 

*Discounted using a 3 percent discount rate. 

8B.4.8 Cost-Effectiveness Ratios 

Construction of cost-effectiveness ratios requires estimates of effectiveness (in this case 

measured by lives saved, life years gained, or MILYs gained) in the denominator and estimates 

of costs in the numerator. As noted above (see Section 8B.3.1), the estimate of costs in the 

numerator should include both the direct costs of the controls necessary to achieve the reduction 

in ambient PM2.5 and O3 and the avoided costs (cost savings) associated with the reductions in 

morbidity (Gold et al., 1996). In general, because reductions in air pollution do not require direct 

actions by the affected populations, there are no specific costs to affected individuals (aside from 

the overall increases in prices that might be expected to occur as control costs are passed on by 

affected industries). Likewise, because individuals do not engage in any specific actions to 

realize the health benefit of the pollution reduction, there are no decreases in utility (as might 

occur from a medical intervention) that need to be adjusted for in the denominator. Thus, the 

elements of the numerator are direct costs of controls minus the avoided COI associated with CB 

and nonfatal AMI. In addition, to account for the value of reductions in O3- and PM2.5-related 

acute health impacts and non-health benefits, we netted out the monetized value of these benefits 

from the numerator to yield a “net cost” estimate. For the MILY aggregate effectiveness 

measure, the denominator is simply the sum of (O3- and PM2.5-related) life years gained from 

increased life expectancy and QALYs gained from the (PM2.5-related) reductions in CB and 

nonfatal AMI. The separate O3- and PM2.5-related inputs to the denominators of the costeffectiveness ratios are summarized above in Tables 8B-19 through 8B-22. The costeffectiveness ratios and 95 percent confidence (credible) intervals resulting from all of the 

sources of uncertainty considered, using Monte Carlo procedures as implemented in the Crystal 

BallTM software program and incorporating both the O3- and PM2.5-related benefits are shown in 

the tables below. Tables 8B-25 and 8B-26 show cost per life saved, using a 3 percent and 7 

percent discount rate, respectively. Tables 8B-27 and 8B-28 show cost per life year saved at the 

two discount rates; and Tables 8B-29 and 8B-30 show cost per MILY gained. 

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Final Regulatory Impact Analysis 

Table 8B-25. Estimated Net Cost (2005$) per O3- and PM2.5-Related Life Saved Under the Final SSI 

& RME Rule in 2020 and 2030, Using a 3 Percent Discount Rate 

O3 Mortality Study PM2.5 Mortality Study 

Cost Effectiveness Ratio: Net Cost (in Thousand $) per 

Life Saved* 

(95% CI)** 

2020 2030 

Bell et al. (2004) Pope et al. (2002) $260 

($110 - $580) 

$74 

($-99 - $280) 

Bell et al. (2004) Laden et al. (2006) $110 

($54 - $220) 

$34 

($-44 - $120) 

Levy et al. (2005) Pope et al. (2002) $180 

($85 - $320) 

$44 

($-58 - $140) 

Levy et al. (2005) Laden et al. (2006) $96 

($48 - $170) 

$26 

($-34 - $83) 

*The cost of the regulation is estimated to be $207.4 million in 2020 and $185.5 million in 2030. PM2.5-related avoided 

deaths are discounted back to 2020 or 2030. O3-related deaths are assumed to occur in 2020 or 2030. 

**95 percent confidence or credible intervals incorporate uncertainty surrounding the O3 and PM2.5 coefficients in the 

mortality and morbidity C-R functions as well as the uncertainty surrounding unit values of morbidity endpoints. All 

estimates rounded to two significant figures. 

Table 8B-26. Estimated Net Cost (2005$) per O3- and PM2.5-Related Life Saved Under the Final SSI 

& RME Rule in 2020 and 2030, Using a 7 Percent Discount Rate 

O3 Mortality Study PM2.5 Mortality Study 

Cost Effectiveness Ratio: Net Cost (in Thousand $) per 

Life Saved* 

(95% CI)** 

2020 2030 

Bell et al. (2004) Pope et al. (2002) $300 

($130 - $660) 

$99 

($-87 - $330) 

Bell et al. (2004) Laden et al. (2006) $130 

($67 - $250) 

$47 

($-39 - $140) 

Levy et al. (2005) Pope et al. (2002) $200 

($100 - $350) 

$57 

($-49 - $160) 

Levy et al. (2005) Laden et al. (2006) $110 

($58 - $190) 

$35 

($-30 - $95) 

*The cost of the regulation is estimated to be $207.4 million in 2020 and $185.5 million in 2030. PM2.5-related avoided 

deaths are discounted back to 2020 or 2030. O3-related deaths are assumed to occur in 2020 or 2030. 

**95 percent confidence or credible intervals incorporate uncertainty surrounding the O3 and PM2.5 coefficients in the 

mortality and morbidity C-R functions as well as the uncertainty surrounding unit values of morbidity endpoints. All 

estimates rounded to two significant figures. 

8-106 
 

Table 8B-27. Estimated Net Cost (2005$) per O3- and PM2.5-Related Life Year Saved Under the Final SSI & RME Rul

Using a 3 Percent Discount Rate 

O3 Mortality Study PM2.5 Mortality Study Life Expectancy Assumption for O3-Related Mortality 

Cost Effectiveness Ratio: Ne

Life Year 

(95% 

2020 

Bell et al. (2004) Pope et al. (2002) General Population $23 ($9.9 - $54) 

Bell et al. (2004) Pope et al. (2002) Subpopulation with Average COPD $24 ($10 - $56) 

Bell et al. (2004) Pope et al. (2002) Subpopulation with Severe COPD $25 ($10 - $61) 

Levy et al. (2005) Pope et al. (2002) General Population $16 ($7.8 - $30) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Average COPD $18 ($8.3 - $34) Levy et al. (2005) Pope et al. (2002) Subpopulation with Severe COPD $21 ($9.2 - $44) 

Bell et al. (2004) Laden et al. (2006) General Population $10 ($5 - $20) Bell et al. (2004) Laden et al. (2006) Subpopulation with Average COPD $11 ($5 - $21) Bell et al. (2004) Laden et al. (2006) Subpopulation with Severe COPD $11 ($5.1 - $21) 

Levy et al. (2005) Laden et al. (2006) General Population $8.8 ($4.4 - $16) Levy et al. (2005) Laden et al. (2006) Subpopulation with Average COPD $9.2 ($4.5 - $17) Levy et al. (2005) Laden et al. (2006) Subpopulation with Severe COPD $9.9 ($4.8 - $19) 

*The cost of the regulation is estimated to be $207.4 million in 2020 and $185.5 million in 2030. All life years are discounted back to the year 

avoided deaths are discounted back to 2020 or 2030. O 3-related deaths are assumed to occur in 2020 or 2030.

**95 percent confidence or credible intervals (CIs) incorporate uncertainty surrounding the O3 and PM2.5 coefficients in the mortality and morbi

the uncertainty surrounding unit values of morbidity endpoints. All estimates rounded to two significant figures.

8-107
Final Regulatory Impact Analysis 

Table 8B-28. Estimated Net Cost (2005$) per O3- and PM2.5-Related Life Year Saved Under the Final SSI & RME Rul

Using a 7 Percent Discount Rate 

O3 Mortality Study PM2.5 Mortality Study Life Expectancy Assumption for O3-Related Mortality 

Cost Effectiveness Ratio: Net 

Life Year S

(95% C

2020 

Bell et al. (2004) Pope et al. (2002) General Population $36 ($16 - $81) 

Bell et al. (2004) Pope et al. (2002) Subpopulation with Average COPD $37 ($16 - $85) Bell et al. (2004) Pope et al. (2002) Subpopulation with Severe COPD $39 ($17 - $93) Levy et al. (2005) Pope et al. (2002) General Population $24 ($12 - $44) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Average COPD $26 ($13 - $49) Levy et al. (2005) Pope et al. (2002) Subpopulation with Severe COPD $31 ($15 - $62) Bell et al. (2004) Laden et al. (2006) General Population $16 ($7.8 - $30) 

Bell et al. (2004) Laden et al. (2006) Subpopulation with Average COPD $16 ($7.9 - $31) 

Bell et al. (2004) Laden et al. (2006) Subpopulation with Severe COPD $17 ($8 - $32) 

Levy et al. (2005) Laden et al. (2006) General Population $13 ($6.8 - $23) 

Levy et al. (2005) Laden et al. (2006) Subpopulation with Average COPD $14 ($7.1 - $24) 

Levy et al. (2005) Laden et al. (2006) Subpopulation with Severe COPD $15 ($7.5 - $28) 

*The cost of the regulation is estimated to be $207.4 million in 2020 and $185.5 million in 2030. All life years are discounted back to the year of 

avoided deaths are discounted back to 2020 or 2030. O 3-related deaths are assumed to occur in 2020 or 2030.

**95 percent confidence or credible intervals (CIs) incorporate uncertainty surrounding the O3 and PM2.5 coefficients in the mortality and morbidit

the uncertainty surrounding unit values of morbidity endpoints. All estimates rounded to two significant figures.

8-108
 

Table 8B-29. Estimated Net Cost (2005$) per O3- and PM2.5-Related MILY Gained Under the Final SSI & RME Rule in 

Using a 3 Percent Discount Rate 

O3 Mortality Study PM2.5 Mortality Study Life Expectancy Assumption for O3-Related Mortality 

Cost Effectiveness Ratio: Ne

MILY G

(95% 

2020 

Bell et al. (2004) Pope et al. (2002) General Population $20 ($9 - $42) 

Bell et al. (2004) Pope et al. (2002) Subpopulation with Average COPD $21 ($9.3 - $44) Bell et al. (2004) Pope et al. (2002) Subpopulation with Severe COPD $21 ($9.4 - $46) Levy et al. (2005) Pope et al. (2002) General Population $15 ($7.2 - $26) Levy et al. (2005) Pope et al. (2002) Subpopulation with Average COPD $16 ($7.6 - $29) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Severe COPD $18 ($8.4 - $36) 

Bell et al. (2004) Laden et al. (2006) General Population $9.8 ($4.7 - $18) 

Bell et al. (2004) Laden et al. (2006) Subpopulation with Average COPD $9.9 ($4.8 - $19) 

Bell et al. (2004) Laden et al. (2006) Subpopulation with Severe COPD $10 ($4.8 - $19) 

Levy et al. (2005) Laden et al. (2006) General Population $8.3 ($4.2 - $14) 

Levy et al. (2005) Laden et al. (2006) Subpopulation with Average COPD $8.7 ($4.3 - $16) 

Levy et al. (2005) Laden et al. (2006) Subpopulation with Severe COPD $9.3 ($4.5 - $17) 

*The cost of the regulation is estimated to be $207.4 million in 2020 and $185.5 million in 2030. PM2.5-related avoided deaths are 

2030. O3-related deaths are assumed to occur in 2020 or 2030. 

**95 percent confidence or credible intervals (CIs) incorporate uncertainty surrounding the O3 and PM2.5 coefficients in the mortal

functions as well as the uncertainty surrounding unit values of morbidity endpoints. All estimates rounded to two significant figure

8-109
Final Regulatory Impact Analysis 

Table 8B-30. Estimated Net Cost (2005$) per O3- and PM2.5-Related MILY Gained Under the Final SSI & RME Rule in 

Using a 7 Percent Discount Rate 

O3 Mortality Study PM2.5 Mortality Study Life Expectancy Assumption for O3-Related Mortality 

Cost Effectiveness Ratio: Ne

MILY G

(95% 

2020 

Bell et al. (2004) Pope et al. (2002) General Population $110 ($58 - $190) 

Bell et al. (2004) Pope et al. (2002) Subpopulation with Average COPD $33 ($15 - $70) 

Bell et al. (2004) Pope et al. (2002) Subpopulation with Severe COPD $31 ($15 - $64) 

Levy et al. (2005) Pope et al. (2002) General Population $31 ($15 - $66) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Average COPD $27 ($13 - $51) 

Levy et al. (2005) Pope et al. (2002) Subpopulation with Severe COPD $22 ($12 - $38) 

Bell et al. (2004) Laden et al. (2006) General Population $23 ($12 - $42) 

Bell et al. (2004) Laden et al. (2006) Subpopulation with Average COPD $15 ($7.6 - $29) Bell et al. (2004) Laden et al. (2006) Subpopulation with Severe COPD $15 ($7.4 - $27) Levy et al. (2005) Laden et al. (2006) General Population $15 ($7.5 - $28) Levy et al. (2005) Laden et al. (2006) Subpopulation with Average COPD $14 ($7.1 - $25) Levy et al. (2005) Laden et al. (2006) Subpopulation with Severe COPD $13 ($6.5 - $21) *The cost of the regulation is estimated to be $207.4 million in 2020 and $185.5 million in 2030. PM2.5-related avoided deaths are 

2030. O3-related deaths are assumed to occur in 2020 or 2030. 

**95 percent confidence or credible intervals (CIs) incorporate uncertainty surrounding the O3 and PM2.5 coefficients in the mortal

functions as well as the uncertainty surrounding unit values of morbidity endpoints. All estimates rounded to two significant figure

8-110
Final Regulatory Impact Analysis 

8B.5 Conclusions 

We estimated the cost effectiveness of attaining the Final Small SI and Recreational Marine 

Engine Rule in 2020 and in 2030, based on reductions in premature deaths and incidence of 

chronic disease. We measured effectiveness using several different metrics, including lives 

saved, life years saved, and QALYs gained (for improvements in quality of life due to reductions 

in incidence of chronic disease). We suggested a new metric for aggregating life years saved and 

improvements in quality of life, morbidity inclusive life years (MILY) which assumes that 

society assigns a weight of one to years of life extended regardless of preexisting disabilities or 

chronic health conditions. 

CEA of environmental regulations that have substantial public health impacts may be 

informative in identifying programs that have achieved cost-effective reductions in health 

impacts and can suggest areas where additional controls may be justified. However, the overall 

efficiency of a regulatory action can only be judged through a complete benefit-cost analysis that 

takes into account all benefits and costs, including both health and non-health effects. The 

benefit-cost analysis for the Final Small SI and Recreational Marine Engine Rule, provided in 

Chapter 8, shows that the rule has potentially large net benefits, indicating that implementation 

of the Final Small SI and Recreational Marine Engine Rule will likely result in improvements in 

overall public welfare. 

8-111 
 Cost-Benefit Analysis 

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Economic Impact Analysis 

CHAPTER 9: Economic Impact Analysis 

We prepared an Economic Impact Analysis (EIA) to estimate the economic impacts of 

the final emission control program on the Small SI and Marine SI engine and equipment 

markets. In this chapter we describe the Economic Impact Model (EIM) developed to estimate 

the market-level changes in price and outputs for affected markets and the social costs of the 

program as well as the expected distribution of those costs across affected economic sectors. We 

also present the results of our analysis. 

We estimate the net social costs of the final program to be about $186 million in 2030.1 

This estimate reflects the estimated compliance costs associated with the Small SI and Marine SI 

engine standards and the expected fuel savings from improved evaporative controls. When the 

fuel savings are not taken into account, the results of the economic impact modeling suggest that 

the social costs of these programs are expected to be about $459 million in 2030. Consumers of 

Small SI and Marine products are expected to bear about 86 percent of these costs. Engine and 

equipment manufacturers are expected to bear 3.3 percent and 10.3 percent, respectively. We 

estimate fuel savings of about $273 million in 2030, which will accrue to consumers. 

With regard to market-level impacts in 2030, the average price increase for Small SI 

engines is expected to be about 7.4 percent ($12 per unit). The average price increase for Marine 

SI engines is expected to be about 1.9 percent ($213 per unit). The largest average price increase 

for Small SI equipment is expected to be about 5.6 percent ($15 per unit) for Class I equipment. 

The largest average price increase for Marine SI vessels is expected to be about 2.4 percent 

($204 per unit) for Personal Watercraft. 

9.1 Overview and Results 

9.1.1 What is an Economic Impact Analysis? 

An Economic Impact Analysis (EIA) is prepared to inform decision makers about the 

potential economic consequences of a regulatory action. The analysis consists of estimating the 

social costs of a regulatory program and the distribution of these costs across stakeholders. 

These estimated social costs can then be compared with estimated social benefits (as presented in 

Chapter 8). As defined in EPA’s Guidelines for Preparing Economic Analyses (EPA 2000, p 

113), social costs are the value of the goods and services lost by society resulting from a) the use 

of resources to comply with and implement a regulation and b) reductions in output. In this 

analysis, social costs are explored in two steps. In the market analysis, we estimate how prices 

and quantities of goods affected by the final emission control program can be expected to 

1

All estimates presented in this section are in 2005$. The fuel savings in this net social cost is calculated by 

2005 gasoline price. 2005 Petroleum Marketing Annual (Table 31). U.S. Department of Energy, Energy Information 

Administration (DoE 2005). 

9-1 
Final Regulatory Impact Analysis 

change once the program goes into effect. In the economic welfare analysis, we look at the total 

social costs associated with the program and their distribution across stakeholders. 

9.1.2 What Methodology Did EPA Use in this Economic Impact Assessment? 

The Economic Impact Model (EIM) is a behavioral model developed for this proposal to 

estimate price and quantity changes and total social costs associated with the emission controls 

under consideration. The model relies on basic microeconomic theory to simulate how 

producers and consumers of affected products can be expected to respond to an increase in 

production costs as a result of the final emission control program. The economic theory that 

underlies the model is described in detail in Section 9.2. 

The EIM is designed to estimate the economic impacts of the final program by simulating 

economic behavior. This is done by creating a model of the initial, pre-control market for a 

product, shocking it by the estimated compliance costs, and observing the impacts on the market. 

At the initial, pre-control market equilibrium, a market is characterized by a price and quantity 

combination at which consumers are willing to purchase the same amount of a product that 

producers are willing to produce at that price (demand is equal to supply). The control program 

under consideration would increase the production costs of affected goods by the amount of the 

compliance costs. This generates a “shock” to the initial equilibrium market conditions. 

Producers of affected products will try to pass some or all of the increased costs on to the 

consumers of these goods through price increases. In response to the price increases, consumers 

will decrease their demand for the affected goods. Producers will react to the decrease in 

quantity demanded by decreasing the quantity they produce; the market will react by setting a 

higher price for those fewer units. These interactions continue until a new market equilibrium 

price and quantity combination is achieved. The amount of the compliance costs that can be 

passed on to consumers is ultimately limited by the price sensitivity of purchasers and producers 

in the relevant market (price elasticity of demand and supply). The EIM explicitly models these 

behavioral responses and estimates new equilibrium prices and output and the resulting 

distribution of social costs across these stakeholders (producers and consumers). 

The EIM is a behavioral model. The estimated social costs of this emission control 

program are a function of the ways in which producers and consumers of the engines and 

equipment affected by the standards change their behavior in response to the costs incurred in 

complying with the standards. These behavioral responses are incorporated in the EIM through 

the price elasticity of supply and demand (reflected in the slope of the supply and demand 

curves), which measure the price sensitivity of consumers and producers. An “inelastic” price 

elasticity (less than one) means that supply or demand is not very responsive to price changes (a 

one percent change in price leads to less than one percent change in supply or demand ). An 

“elastic” price elasticity (more than one) means that supply or demand is sensitive to price 

changes (a one percent change in price leads to more than one percent change in supply or 

demand). A price elasticity of one is unit elastic, meaning there is a one-to-one correspondence 

between a change in price and change in demand. The price elasticities used in this analysis are 

described in Section 9.3 and were estimated using well-established econometric methods. It 

9-2 
Economic Impact Analysis 

should be noted that demand in the engine markets is internally derived from the Small SI 

equipment and Marine SI vessel markets as part of the process of running the model. This is an 

important feature of the EIM, which allows it to link the engine and equipment components of 

each model and simulate how compliance costs can be expected to ripple through the affected 

market. 

9.1.3 What Economic Sectors are Included in the Economic Impact Model? 

There are two broad economic sectors affected by the emission control program 

described in this proposal: (1) Small SI engines and equipment, and (2) Marine SI engines and 

equipment. For Small SI engines and equipment we model one integrated handheld engine and 

equipment category. On the nonhandheld side, the model distinguishes between 9 engine 

categories, depending on engine class and useful life (Class I: UL125, UL250, and UL500; 

Class I -snowblower: UL 125, UL250, and UL 500; Class II: UL250, UL500, UL1000), and 8 

nonhandheld equipment categories (agriculture/construction/ general industrial; utility and 

recreational vehicles; lawn mowers; tractors; other lawn and garden; gensets/welders; 

pumps/compressors/pressure washers; and snowblowers). For Marine SI engines and 

equipment, the model distinguishes between sterndrives and inboards (SD/I), outboards (OB), 

and personal watercraft (PWC); SD/I and OB are further classified by whether they are luxury or 

not. These markets are described in Section 9.3 and in more detail in the industry 

characterizations prepared for this proposal. 

This analysis assumes that the all of these products are purchased and used by residential 

households. This means that to model the behavior change associated with final standards we 

model all uses as residential lawn and garden care, power generation (Small SI) or personal 

recreation (Marine SI). We do not explicitly model commercial uses (how the costs of 

complying with the final programs may affect the production of goods and services that use 

Small SI or Marine SI engines or equipment as production inputs); we treat all commercial uses 

as if they were residential uses. We believe this approach is reasonable because the commercial 

share of the end use markets for both Small SI and Marine SI equipment is very small (see 

Section 9.3.1.1). In addition, for any commercial uses of these products the share of the cost of 

these products to total production costs is also small (e.g., the cost of a Small SI generator is only 

a very small part of the total production costs for a construction firm). Therefore, a price 

increase of the magnitude anticipated for this control program is not expected to have a 

noticeable impact on prices or quantities of goods or services produced using Small SI or Marine 

SI equipment as inputs (e.g., commercial turf care, construction, or fishing). 

In the EIM the Small SI and Marine SI markets are not linked (there is no feedback 

mechanism between the Small SI and Marine SI market segments). This is appropriate because 

the affected equipment is not interchangeable and because there is very little overlap between the 

engine producers in each market. These two sectors represent different aspects of economic 

activity (lawn and garden care and power generation as opposed to recreational marine) and 

production and consumption of one product is not affected by the other. In other words, an 

increase in the price of lawnmowers is not expected to have an impact on the production and 

supply of personal watercraft, and vice versa. Production and consumption of each of these 

9-3 
Final Regulatory Impact Analysis 

products are the results of other factors that have little crossover impacts (the need for residential 

garden upkeep or power generation; the desire for personal recreation). 

Consistent with the final emission controls, this Economic Impact Analysis covers 

engines sold in 49 states. California engines are not included because California has its own 

state-level controls for Small SI and Marine SI engines. The sole exceptions are Small SI 

engines used in agriculture and construction applications in California: these engines are 

included in the control program of this analysis because the Clean Air Act preempts California 

from setting standards for those engines. 

Table 9.1-1 summarizes the markets included in this Economic Impact Analysis. More 

detailed information on the markets and model data inputs is provided in Section 9.3.3, and in 

the industry profiles prepared for this proposal (See Chapter 1, & RTI, 2006 ). 

9-4 
Economic Impact Analysis 

Table 9.1-1: Summary of Markets in Economic Impact Model 

Model Dimension Small SI Marine SI 

Description of Markets HANDHELD 

No distinction between engine and 

equipment types for this analysis 

NONHANDHELD 

Engine types

 Class I (125, 250, 500 hours)

 Class II (250, 500, 1000 hours) 

Equipment types

 Lawn mowers

 Lawn and garden tractors

 Pumps/compressors/pressure washers

 Agriculture/construction/industrial

 Other lawn and garden

 Gensets/welders

 Snowblowers

 Utility and recreational vehicles 

Engine and equipment types

 SD/I recreational (runabouts,

 airboats, jetboats)

 SD/I luxury (yachts, cruisers, offshore)

 OB recreational (runabouts, pontoons,

 fishing)

 OB luxury (yacht, cruiser, express 

fish)

 Personal watercraft (PWC) 

Engine sizes

 Less than 25 hp

 26 to 50 hp

 51 to 100 hp

 101 to 175 hp

 176 to 300 hp

 Greater than 300 hp 

Geographic scope 49 state, plus agriculture and 

construction for California 

49 state

 (no California engines or equipment) 

Market structure Competitive Competitive 

Baseline population EPA certification database 

PSR OE Link sales database 

EPA and CARB certification database 

NMMA published statistical data 

Growth projections EPA’s 2005 Nonroad model EPA’s 2005 Nonroad model 

Supply elasticity Econometric estimate (elastic) Econometric estimate (elastic) 

Demand elasticity Econometric estimate

 Gensets, all handheld: elastic

 Lawn mowers & other LG: inelastic

 All others: unit elastic 

Econometric estimate (elastic) 

Regulatory shock Handheld (integrated market): direct 

compliance costs (fixed + variable) 

cause shift in supply function 

Nonhandheld: 

Engine: direct compliance costs 

cause shift in supply function 

Equipment (Class I): no direct 

compliance costs but higher engine 

prices cause shift in supply function 

Equipment (Class II): direct 

compliance costs plus higher engine 

prices cause shift in supply function 

PWC (integrated): direct compliance 

costs (fixed + variable) cause shift in 

supply function 

SD/I and Outboard luxury: 

Engine: direct compliance costs 

cause shift in supply function 

Vessel: direct compliance costs plus 

higher engine prices cause shift in 

supply function 

Outboard recreational: 

Engine: direct compliance costs 

cause shift in supply function 

Vessel: direct compliance costs 

cause shift in supply function 
Final Regulatory Impact Analysis 

9.1.4 Summary of Results 

The EIA consists of two parts: a market analysis and welfare analysis. The market 

analysis looks at expected changes in prices and quantities for affected products. The welfare 

analysis looks at economic impacts in terms of annual and present value changes in social costs. 

We performed a market analysis for all years and all engines and equipment markets. In 

this section we present summarized results for selected markets and years. More detail can be 

found in the appendices to this chapter and in the docket for this rule (Li, 2007). Also, included 

in Appendix 9H are sensitivity analyses for several key inputs. 

In this analysis, initial market equilibrium conditions are shocked by either the fixed cost 

or the variable cost. For the market analysis, this leads to a small increase in estimated price 

impacts for the years 2008 through 2014, the period during which the costs change over time 

reflecting the phase-in of either the different costs (variable and fixed costs) or the different 

standards. The increase is small because, for many elements of the program, annual per unit 

compliance costs are relatively smaller than engine or equipment per unit price . For the 

welfare analysis, applying both fixed and variable costs means that the burden of the social costs 

attributable to producers and consumers remains fixed throughout the period of analysis. This is 

because producers pass the fixed costs to consumers at the same rate as the variable costs instead 

of having to absorb them internally. 

9.1.4.1 Market Analysis Results 

In the market analysis, we estimate how prices and quantities of goods affected by the 

final emission control program can be expected to change once the program goes into effect. 

The analysis relies on the initial market equilibrium prices and quantities for each type of 

equipment and the price elasticity of supply and demand. It predicts market reactions to the 

increase in production costs due to the new compliance costs (variable and fixed). It should be 

noted that this analysis does not allow any other factors of production to vary. In other words, it 

does not consider that manufacturers may adjust their production processes or marketing 

strategies in response to the control program. Also, as explained above, while the markets are 

shocked by both fixed and variable costs, the market shock is not offset by fuel savings. 

A summary of the estimated market impacts is presented in Table 9.1-2 for 2014, 2018, 

and 2030. These years were chosen because 2014 is the year of highest compliance cost; the 

market impacts reflect the compliance costs for all the programs as well as growth in equipment 

population; 2018 is the year in which the learning curve is expected to be applied to the variable 

cost; and 2030 illustrates the long-term impacts of the program. 

Market level impacts are reported for the engine and equipment markets separately. This 

is because the EIM is a two-level model that treats these markets separately. However, changes 

in equipment prices and quantities are due to impacts of both direct equipment compliance costs 

9-6 
Economic Impact Analysis 

and indirect engine compliance costs that are passed through to the equipment market from the 

engine market through higher engine prices. 

The average market-level impacts presented in this section are designed to provide a 

broad overview of the expected market impacts that is useful when considering the impacts of 

the rule on the economy as a whole. The average price impacts are product-weighted averages 

of the results for the individual engine and equipment categories included in that sub-sector (e.g., 

the estimated Marine SI engine price and quantity changes are weighted averages of the 

estimated results for all of the Marine SI engine markets). The average quantity impacts are the 

sum of the decrease in units produced units across sub-markets. Price increases and quantity 

decreases for specific types of engines and equipment are likely to be different. 

Although each of the affected equipment in this analysis generally require one engine 

(the exception being Marine SI sterndrive/inboards), the estimated decrease in the number of 

engines produced in Table 9.1-2 is less than the estimated decrease in the number of equipment 

produced. At first glance, this result seems counterintuitive because it does not reflect the 

approximate one-to-one correspondence between engines and equipment. This discrepancy 

occurs because the engine market-level analysis examines only output changes for engines that 

are produced by independent engine manufacturers and subsequently sold to independent 

equipment manufacturers. Engines produced and consumed by vertically integrated 

equipment/engine manufactures are not explicitly modeled. Therefore, the market-level analysis 

only reflects engines sold on the "open market," and estimates of output changes for engines 

consumed internally are not reflected in this number.2 Despite the fact that changes in 

consumption of internally consumed engines in not directly reported in the market-level analysis 

results, the costs associated with these engines are included in the market-level analysis (as 

supply shift for the equipment markets). In addition, the cost and welfare analyses include the 

compliance costs associated with internally consumed engines. 

9.1.4.1.1 Marine SI Market Analysis 

The average price increase for Marine SI engines in 2014, the high cost year, is estimated 

to be about 2.4 percent, or $266. By 2018, this average price increase is expected to decline to 

about 1.9 percent, or $213, and remain at that level for later years. The market impact analysis 

predicts that with these increases in engine prices the expected average decrease in total sales in 

2014 is about 2.7 percent, or 10,883 engines. This decreases to about 2.2 percent in 2018, or 

about 9,055 engines. 

On the vessel side, the average price change reflects the direct equipment compliance 

costs plus the portion of the engine costs that are passed on to the equipment purchaser (via 

higher engine prices). The average price increase in 2014 is expected to be about 1.6 percent, or 

2

For example, PWC and handheld equipment producers generally integrate equipment and engine 

manufacturing processes and are included in the EIM as one-level equipment markets. Since there is no engine 

market for these engines, the EIM does not include PWC and handheld engine consumption changes in engine 

market-level results. 

9-7 
Final Regulatory Impact Analysis 

$285. By 2018, this average price increase is expected to decline to about 1.3 percent, or $231. 

These price increases are expected to vary across vessel categories. The category with the 

largest price increase in 2014 is expected to be personal watercraft , with an estimated price 

increase of about 3.0 percent in 2014; this is expected to decrease to 2.4 percent in 2018. The 

smallest expected change in 2014 is expected to be for sterndrive/inboards vessels, which are 

expected to see price increases of about 0.9 percent. The market impact analysis predicts that 

with these increases in vessel prices the expected average decrease in quantity produced in 2014 

is about 3.2 percent, or 12,230 vessels. This is expected to decrease to about 2.6 percent in 

2018, or about 10,145 vessels. The personal watercraft category is expected to experience the 

largest decline in 2014, about 6.0 percent (4,800 vessels). The smallest percentage decrease in 

production is expected for sterndrive/inboards at 1.7 percent (1,580 vessels); the smallest 

absolute decrease in quantity is expected for outboard recreational vessels, at 144 vessels (2.0 

percent). 

9.1.4.1.2 Small SI Market Analysis 

The average price increase for Small SI engines in 2014, the high cost year, is estimated to 

be about 8.3 percent, or $14. By 2018, this average price increase is expected to decline to about 

7.4 percent, or $12, and remain at that level for later years. The market impact analysis predicts 

that with these increases in engine prices the expected average decrease in total sales in 2014 is 

expected to be about 1.9 percent, or 304,000 engines. This is expected to decrease to about 1.7 

percent in 2018, or about 285,000 engines. 

On the equipment side, the average price change reflects the direct equipment compliance 

costs plus the portion of the engine costs that are passed on to the equipment purchaser (via 

higher engine prices). The average price increase for all Small SI equipment in 2014 is expected 

to be about 2.6 percent, or $10. By 2018, this average price increase is expected to decline to 

about 2.3 percent, or $8. The average price increase and quantity decrease differs by category of 

equipment. As shown in Table 9.1-2, the price increase for Class I equipment is estimated to be 

about 6.2 percent ($17) in 2014, decreasing to 5.6 percent ($15) in 2018. The market impact 

analysis predicts that with these increases in equipment prices the expected average decrease in 

the quantity of Class I equipment produced in 2014 is about 2.1 percent, or 209,000 units. This 

is expected to decrease to about 1.9 percent in 2018, or about 200,000 units. For Class II 

equipment, a higher price increase is expected, about 2.6 percent ($24) in 2014, decreasing to 2.2 

percent ($20) in 2018. The expected average decrease in the quantity of Class II equipment 

produced in 2014 is about 2.8 percent, or 101,000 units, decreasing to 2.4 percent, or about 

92,000 units, in 2018. 

For the handheld equipment market, prices are expected to increase about 0.2 percent for 

all years, and quantities are expected to decrease about 0.3 percent. 

9-8 
Economic Impact Analysis 

Table 9.1-2: Summary of Estimated Market Impacts for 2014, 2018, 2030 (2005$) 

Market 

Change in Price Change in Quantity 

Absolute Percent Absolute Percent 

2014 

Marine

 Engines $266 2.4% -10,883 -2.7%

 Equipment $285 1.6% -12,229 -3.2%

 SD/I $299 0.9% -1,578 -1.7%

 OB Recreational $870 1.0% -144 -2.0%

 OB Luxury $271 1.4% -5,666 -2.8%

 PWC $253 3.0% -4,841 -6.0% 

Small SI

 Engines $14 8.3% -303,992 -1.9%

 Equipment $10 2.6% -360,310 -1.4%

 Class I $17 6.2% -209,284 -2.1%

 Class II $24 2.6% -101,104 -2.8%

 HH $0.3 0.2% -49,922 -0.3% 

2018 

Marine

 Engines $213 1.9% -9,055 -2.2%

 Equipment $231 1.3% -10,145 -2.6%

 SD/I $244 0.7% -1,318 -1.4%

 OB Recreational $702 0.8% -119 -1.6%

 OB Luxury $218 1.1% -4,697 -2.3%

 PWC $204 2.4% -4,010 -4.8% 

Small SI

 Engines $12 7.4% -284,995 -1.7%

 Equipment $8 2.3% -347,189 -1.2%

 Class I $15 5.6% -200,155 -1.9%

 Class II $20 2.2% -91,871 -2.4%

 HH $0.3 0.2% -55,164 -0.3% 

2030 

Marine

 Engines $213 1.9% -9,802 -2.2%

 Equipment $231 1.3% -10,981 -2.6%

 SD/I $244 0.7% -1,426 -1.4%

 OB Recreational $702 0.8% -129 -1.6%

 OB Luxury $218 1.1% -5,085 -2.3%

 PWC $204 2.4% -4,341 -4.8% 

Small SI

 Engines $12 7.4% -338,346 -1.7%

 Equipment $8 2.3% -412,103 -1.2%

 Class I $15 5.6% -237,485 -1.9%

 Class II $20 2.2% -109,120 -2.4%

 HH $0.3 0.2% -65,498 -0.3% 

9-9 
Final Regulatory Impact Analysis 

9.1.4.2 Economic Welfare Results 

In the economic welfare analysis we look at the costs to society of the final program in 

terms of losses to consumer and producer surplus. These surplus losses are combined with 

estimated fuel savings to estimate the net economic welfare impacts of the program. Estimated 

annual net social costs for selected years are presented in Table 9.1-3. This table shows that total 

social costs for each year are slightly less than the total engineering costs. This is because the 

total engineering costs do not reflect the decreased sales of engines and equipment that are 

incorporated in the total social costs. 

9-10 
Economic Impact Analysis 

Table 9.1-3: Estimated Annual Engineering and Social Costs Through 2037 

(2005$, $million) 

Year 

Total 

Engineering 

Costs 

Total Social 

Costs Fuel Savings 

Net Engineering 

Costs 

(including fuel 

savings) 

Net Social 

Costs 

(including fuel 

savings) 

2008 $53.8 $53.8 $3.2 $50.7 $50.6 

2009 $126.8 $126.2 $8.1 $118.7 $118.1 

2010 $271.0 $267.4 $19.6 $251.5 $247.8 

2011 $328.7 $324.1 $43.9 $284.8 $280.2 

2012 $441.6 $435.5 $70.8 $370.8 $364.7 

2013 $445.4 $439.3 $95.7 $349.7 $343.6 

2014 $450.0 $443.8 $115.9 $334.1 $327.9 

2015 $411.6 $406.8 $134.3 $277.3 $272.5 

2016 $408.8 $404.2 $150.9 $258.0 $253.3 

2017 $398.3 $393.8 $165.3 $233.0 $228.6 

2018 $403.3 $398.8 $178.3 $225.0 $220.5 

2019 $408.3 $403.8 $190.4 $217.9 $213.4 

2020 $413.4 $408.8 $201.4 $212.0 $207.4 

2021 $418.4 $413.7 $211.1 $207.2 $202.6 

2022 $423.4 $418.6 $220.5 $202.9 $198.2 

2023 $428.4 $423.6 $229.3 $199.0 $194.3 

2024 $433.4 $428.6 $237.1 $196.3 $191.5 

2025 $438.4 $433.6 $244.2 $194.2 $189.3 

2026 $443.5 $438.6 $250.8 $192.7 $187.8 

2027 $448.5 $443.6 $256.9 $191.6 $186.6 

2028 $453.6 $448.6 $262.7 $190.8 $185.8 

2029 $458.6 $453.5 $268.1 $190.5 $185.4 

2030 $463.7 $458.6 $273.0 $190.6 $185.5 

2031 $468.7 $463.6 $277.6 $191.1 $185.9 

2032 $473.8 $468.6 $281.9 $191.9 $186.7 

2033 $478.8 $473.6 $285.8 $193.0 $187.7 

2034 $483.9 $478.5 $289.6 $194.2 $188.9 

2035 $488.9 $483.6 $293.3 $195.6 $190.3 

2036 $494.0 $488.6 $296.8 $197.2 $191.8 

2037 $499.0 $493.6 $300.1 $198.9 $193.5 

NPV at 3%a $7,705.3 $7,616.6 $3,374.6 $4,330.7 $4,242.0 

NPV at 7%a $4,559.3 $4,506.2 $1,774.7 $2,784.6 $2,731.4 

a EPA presents the present value of cost and benefits estimates using both a three percent and a seven percent 

social discount rate. According to OMB Circular A-4, "the 3 percent discount rate represents the 'social rate 

of time preference'... [which] means the rate at which 'society' discounts future consumption flows to their 

present value"; "the seven percent rate is an estimate of the average before-tax rate of return to private capital 

in the U.S. economy ... [that] approximates the opportunity cost of capital." 

9-11 
Final Regulatory Impact Analysis 

Figure 9.1-1: Estimated Engineering, Total Social, Net Social Costs and Fuel Savings 

Table 9.1-4 shows how total social costs are expected to be shared across stakeholders, for 

selected years. According to these results, consumers in the Marine SI market are expected to 

bear approximately 76 percent of the cost of the Marine SI program. This is expected to be offset 

by the fuel savings. Vessel manufacturers are expected to bear about 17 percent of that program, 

and engine manufacturers the remaining 6 percent. In the Small SI market, consumers are 

expected to bear 91 percent of the cost of the Small SI program. This will also be offset by the 

fuel savings. Equipment manufacturers are expected to bear about 7 percent of that program, and 

engine manufacturers the remaining 2 percent. The estimated percentage changes in surplus are 

the same for all years because the initial equilibrium conditions are shocked by both fixed and 

variable costs; producers would pass the fixed costs to consumers at the same rate as the variable 

costs. 

9-12 
Economic Impact Analysis 

Table 9.1-4: Summary of Estimated Social Costs for 2014, 2018, 2030 (2005$, $million) 

Market 

Absolute Change 

in Surplus 

Percent Change in 

Surplus 

Fuel 

Savings 

Total Change in 

Surplus 

2014 

Marine SI

 Engine Manufacturers -$10.5 6% -$10.5

 Equipment Manufacturers -$29.7 17% -$29.7

 End User (Households) -$130.0 76% $45.4 -$84.6 

Subtotal -$170.2 -$124.8 

Small SI

 Engine Manufacturers -$5.4 2% -$5.4

 Equipment Manufacturers -$18.1 7% -$18.1

 End User (Households) -$250.2 91% $70.4 -$179.7 

Subtotal -$273.6 -$203.2 

TOTAL -$443.8 $115.9 -$327.9 

2018 

Marine SI

 Engine Manufacturers -$8.7 6% - -$8.7

 Equipment Manufacturers -$25.0 18% -$25.0

 End User (Households) -$108.2 76% $82.7 -$25.6 

Subtotal -$142.0 -$59.3 

Small SI

 Engine Manufacturers -$5.0 2% -$5.0

 Equipment Manufacturers -$16.9 7% -$16.9

 End User (Households) -$235.0 91% $95.6 -$139.4 

Subtotal -$256.8 -$161.2 

TOTAL -$398.8 $178.3 -$220.5 

2030 

Marine SI

 Engine Manufacturers -$9.4 6% -$9.4

 Equipment Manufacturers -$27.1 18% -$27.1

 End User (Households) -$117.2 76% $152.9 $35.8 

Subtotal -$153.7 -$0.8 

Small SI

 Engine Manufacturers -$5.9 2% -$5.9

 Equipment Manufacturers -$20.0 7% -$20.0

 End User (Households) -$278.9 91% $120.1 -$158.8 

Subtotal -$304.9 -$184.8 

TOTAL -$458.6 $273.0 -$185.5 

Table 9.1-5 contains more detailed information on the sources of the social costs for 2014. 

This table shows that engines and equipment manufacturers are expected to bear more of the 

burden of the program than end users. The loss of producer surplus for the small SI equipment 

and vessel manufacturers has two sources. First, they would bear part of the burden of the 

equipment costs. Second, they would also bear part of the engine costs, which are passed on to 

vessel manufacturers in the form of higher engine prices. In comparing with small SI equipment 

manufactures, marine SI vessel manufacturers would be able to pass along a relatively smaller 

share of compliance costs to end consumers due to the elastic price elasticity of demand for 

consumers of these vessels. As indicated in Table 9.3-22, the price elasticity of small SI 

equipment demand is inelastic while the price elasticity of vessel demand is very elastic. 

9-13 
Final Regulatory Impact Analysis 

Table 9.1-5: Estimated Surplus Changes by Market and Stakeholder for 2014 

(2005$, $million) 

Scenario 

Engineering 

Compliance 

Costs 

Producer 

Surplus 

Consumer 

Surplus 

Total 

Surplus 

Fuel 

Savings 

Net 

Surplus 

Engine Manufacturers 

Equipment

 Manufacturers 

Engine Price

 Changes 

Equipment Cost

 Changes 

 End User

 (Households) 

Engine Price

 Changes 

Equipment Price

 Changes 

Subtotal 

$118.7 

$55.1 

$173.8 

Marine SI 

-$10.5 

-$29.7 

-$13.2 

-$16.5 

-$130.0 

-$93.6 

-$36.4 

-$40.2 -$130.0 

-$10.5 

-$29.7 

-$130.0 

-$170.2 

$45.4 

$45.4 

-$10.5 

-$29.7 

-$84.6 

-$124.8 

Small SI

 Engine $227.2 -$5.4 -$5.4 -$5.4 

Manufacturers 

 Equipment $49.0 -$18.1 -$18.1 -$18.1 

Manufacturers 

Engine Price -$13.0 

Changes 

Equipment Cost -$5.1

 Changes 

 End User -$250.1 -$250.1 $70.4 -$179.6 

(Households) 

Engine Price -$206.6 

Changes 

Equipment Cost -$43.5 

Changes 

Subtotal $276.2 -$23.6 -$250.1 -$273.6 $70.4 -$203.2 

TOTAL $450.0 -$63.7 -$380.1 -$443.8 $115.9 -$327.9 

The present value of net social costs of the final standards through 2037 at a 3 percent 

discount rate, shown in Table 9.1-6, is estimated to be $4.2 billion, taking the fuel savings into 

account. We also performed an analysis using a 7 percent social discount rate. Using that 

discount rate, the present value of the net social costs through 2037 is estimated to be $2.7 billion, 

including the fuel savings. 

9-14 
Economic Impact Analysis 

Table 9.1-6. Estimated Net Social Costs Through 2037 by Stakeholder (2005$, $million) 

Market 

Total Change in 

Surplus 

Percentage Change 

in Total Surplus Fuel Savings 

Net Change in 

Surplus 

Net Present Value 3% 

Marine SI

 Engine Manufacturers 

 Equipment Manufacturers 

End User (Households) 

Subtotal 

Small SI

 Engine Manufacturers 

 Equipment Manufacturers 

End User (Households) 

Subtotal 

TOTAL 

-$167.0 6% 

-$474.5 17% 

-$2,079.0 76% 

-$2,720.5 

-$94.1 2% 

-$329.9 7% 

-$4,472.1 91% 

-$4,896.1 

-$7,616.6 

$1,730.8 

$1,730.8 

$1,643.8 

$1,643.8 

$3,374.6 

-$167.0 

-$474.5 

-$348.1 

-$989.6 

-$94.1 

-$329.9 

-$2,828.3 

-$3,252.3 

-$4,242.0 

Marine SI

 Engine Manufacturers 

 Equipment Manufacturers 

End User (Households) 

Subtotal 

Small SI

 Engine Manufacturers 

 Equipment Manufacturers 

End User (Households) 

Subtotal 

TOTAL 

Net Present Value 7% 

-$100.8 6% 

-$285.2 17% 

-$1,257.1 77% 

-$1,643.2 

-$54.8 2% 

-$195.4 7% 

-$2,612.8 91% 

-$2,863.0 

-$4,506.2 

$881.0 

$881.0 

$893.8 

$893.8 

$1,774.7 

-$100.8 

-$285.2 

-$376.1 

-$762.2 

-$54.8 

-$195.4 

-$1,719.1 

-$1,969.2 

-$2,731.4 

9-15 
Final Regulatory Impact Analysis 

9.2 Economic Methodology 

Economic impact analysis uses a combination of theory and econometric modeling to 

evaluate potential behavior changes associated with a new regulatory program. As noted above, 

the goal is to estimate the impact of the regulatory program on producers and consumers. This is 

done by creating a mathematical model based on economic theory and populating the model using 

publically available price and quantity data. A key factor in this type of analysis is the 

responsiveness of the quantity of engines and equipment demanded by consumers or supplied by 

producers to a change in the price of that product. This relationship is called the elasticity of 

demand or supply. 

The EIM’s methodology is rooted in applied microeconomic theory and was developed 

following the OAQPS Economic Analysis Resource Document (EPA 1999). This section 

discusses the economic theory underlying the modeling for this EIA and several key issues that 

affect the way the model was developed. 

9.2.1 Behavioral Economic Models 

Models incorporating different levels of economic decision making can generally be 

categorized as with-behavior responses or without-behavior responses. The EIM is a behavioral 

model. 

Engineering cost analysis is an example of the latter and provides detailed estimates of the 

cost of a regulation based on the projected number of affected units and engineering estimates of 

the annualized costs. The result is an estimate of the total compliance costs for a program. 

However, these models do not attempt to estimate how a regulatory program will change the prices 

or output of an affected industry. Therefore, the results may over-estimate the total costs of a 

program because they do not take decreases in quantity produced into account. 

The with-behavior response approach builds on the engineering cost analysis and 

incorporates economic theory related to producer and consumer behavior to estimate changes in 

market conditions. As Bingham and Fox (1999) note, this framework provides “a richer story” of 

the expected distribution of economic welfare changes across producers and consumers. In 

behavioral models, manufacturers of goods affected by a regulation are economic agents that can 

make adjustments, such as changing production rates or altering input mixes, that will generally 

affect the market environment in which they operate. As producers change their production levels 

in response to a new regulation, consumers of the affected goods are typically faced with changes 

in prices that cause them to alter the quantity that they are willing to purchase. These changes in 

price and output resulting from the market adjustments are used to estimate the distribution of 

social costs between consumers and producers. 

If markets are competitive and per-unit regulatory costs are small, the behavioral approach 

will yield approximately the same total cost impact as the engineering cost approach. However, 

the advantage of the with-behavior response approach is that it illustrates how the costs flow 

9-16 
Economic Impact Analysis 

through the economic system and it identifies which stakeholders, producers, and consumers are 

most likely to be affected. 

9.2.2 What Is the Economic Theory Underlying the EIM? 

The EIM is a multi-market partial-equilibrium numerical simulation model that estimates 

price and quantity changes in the intermediate run under competitive market conditions. Each of 

these model features is described in this section. 

9.2.2.1 Partial Equilibrium Multi-Market Model 

In the broadest sense, all markets are directly or indirectly linked in the economy, and a 

new regulatory program will theoretically affect all commodities and markets to some extent. 

However, not all regulatory programs have noticeable impacts on all markets. For example, a 

regulation that imposes significant per unit compliance costs on an important manufacturing input, 

such as steel, will have a larger impact on the national economy. A regulation that imposes a 

small direct compliance cost on an important input, or any direct compliance costs on an input that 

is only a small share of production costs, would be expected to have less of an impact on all 

markets in the economy. 

The appropriate level of market interactions to be included in an economic impact analysis 

is determined by the number of industries directly affected by the requirements and the ability of 

affected firms to pass along the regulatory costs in the form of higher prices. There are at least 

three alternative approaches for modeling interactions between economic sectors, that reflect three 

different levels of analysis. 

In a partial equilibrium model, individual markets are modeled in isolation. The only 

factor affecting the market is the cost of the regulation on facilities in the industry being modeled; 

there are no interaction effects with other markets. Conditions in other markets are assumed either 

to be unaffected by a policy or unimportant for cost estimation. 

In a multi-market model, a subset of related markets is modeled together, with sector 

linkages, and hence selected interaction effects, explicitly specified. This approach represents an 

intermediate step between a simple, single-market partial equilibrium approach and a full general 

equilibrium approach. This technique has most recently been referred to in the literature as 

"partial equilibrium analysis of multiple markets" (Berck and Hoffmann, 2002). 

In a general equilibrium model, all sectors of the economy are modeled together, 

incorporating interaction effects between all sectors included in the model. General equilibrium 

models operationalize neoclassical microeconomic theory by modeling not only the direct effects 

of control costs but also potential input substitution effects, changes in production levels 

associated with changes in market prices across all sectors, and the associated changes in welfare 

economy-wide. A disadvantage of general equilibrium modeling is that substantial time and 

resources are required to develop a new model or tailor an existing model for analyzing regulatory 

alternatives. 

9-17 
Final Regulatory Impact Analysis 

This analysis uses a partial equilibrium approach in that it models only those markets that 

are directly affected by the final emission control program: the Small SI and Marine SI markets. 

In addition, these markets are modeled separately. This approach is appropriate because the Small 

SI and Marine SI sector represent different activities (residential garden care and personal 

recreation), and production and consumption of one is not affected by the other. In other words, 

an increase in the price of lawnmowers is not expected to have an impact on the production and 

supply of recreational marine vessels, and vice versa. Production and consumption of these 

products are the result of other factors that have little cross-over impacts. 

The EIM uses a single-market approach for some sectors (Small SI handheld, Class I 

nonhandheld, personal watercraft, outboards recreational) and a two-market approach for the 

others (Small SI Class II nonhandheld; sterndrive/inboards; and outboards luxury) reflecting 

whether the markets are integrated and whether the controls affect only engines or both engines 

and equipment. The advantage of a two-market approach is that it allows us to describe the 

expected distribution of the program’s effects across equipment and engine markets as well as the 

effects on purchasers of these engines and equipment. To simulate these relationships, the EIM 

consists of a series of standard partial equilibrium models that are linked through interactions 

between the equipment and engine markets. As a result, the model estimates changes in prices and 

quantities across all markets simultaneously for each of the linked engine and equipment markets. 

The EIM does not specifically estimate potential price and quantity impacts on final goods 

and services that may be produced by equipment that would be subject to the final controls in the 

agricultural and construction sectors. This is appropriate because the vast majority of engines and 

equipment that would be subject to the final standards are purchased for residential use 

(recreational marine; home lawn and garden and residential utility uses; see Section 9.3 and the 

industry characterization prepared for this rule). Not only is the share of commercial users of this 

equipment small, but such equipment represents only a small portion of the total production costs 

for application markets such as agriculture, construction or manufacturing. The final standards 

would affect only a very small part of total inputs for those markets and would not be expected to 

result in an adverse impact on output and prices of goods produced in these commercial 

application sectors. 

It should also be noted that the economic impact model employed for this analysis 

estimates the market-level economic impacts of the rule. It is not a firm-level analysis and 

therefore the impact for any particular manufacturer may be greater or less than the average impact 

for the market as a whole. This difference can be important, particularly where the rule affects 

different firms’ costs over different volumes of production. However, to the extent there are 

differential effects, EPA believes that the wide array of flexibilities provided in this rule are 

adequate to address any cost inequities that are likely to arise. 

9.2.2.2 Competitive Market Structure Model 

In a market oriented economic analysis, the analyst must determine the market structure 

according to most appropriate characteristics of the market under study. This market structure will 

form the basis of the economic impact model and determine the economic relationship to be 

9-18 
Economic Impact Analysis 

reflected in the model. There are several types of market structures in economics: perfect 

competition, oligopoly, monopolistic competition, and monopoly. The typical economic impact 

analysis assumes a competitive market structure, although circumstance may require relaxing this 

assumption.3

 The assumption of a competitive market is not about the number of firms in a market. It is 

about wether producers in the market are price takers or wether they have sufficient market power 

to influence the market price. In a competitive market, producers are price takers. Indicators of a 

competitive market include absence of barriers to entry, absence of strategic behavior among firms 

in the market, and product differentiation.4 In addition, according to contestable market theory, 

oligopolies and even monopolies will behave very much like firms in a competitive market if it is 

possible to enter particular markets costlessly (i.e., there are no sunk costs associated with market 

entry or exit). This would be the case, for example, when products are substantially similar. 

In imperfectly competitive markets, producers have some ability to influence the market 

price of output they produce. One of the classic reasons firms may be able to do this is their ability 

to produce commodities with unique attributes that differentiate them from competitors’ products. 

This allows them to limit supply, which in turn increases the market price, given the traditional 

downward-sloping demand curve. Decreasing the quantity produced increases the monopolist’s 

profits but decreases total social surplus because a less than optimal amount of the product is being 

consumed. In the monopolistic equilibrium, the value society (consumers) places on the marginal 

product exceeds the marginal cost to society (producers) of producing the last unit. Thus, social 

welfare would be increased by inducing the monopolist to increase production. Social cost 

estimates associated with a final regulation are larger with monopolistic market structures and 

other forms of imperfect competition because the regulation exacerbates the existing social 

inefficiency of too little output from a social perspective. The Office of Management and Budget 

(OMB) explicitly mentions the need to consider these market power-related welfare costs in 

evaluating regulations under Executive Order 12866 (OMB, 1996). 

This EIA is based on a competitive market structure. This is appropriate because the 

markets under analysis do not exhibit evidence of noncompetitive behavior: there are no 

indications of barriers to entry, the firms in these markets are not price setters, and there is no 

evidence of high levels of strategic behavior in the price and quantity decisions of the firms. 

As described in the industry profiles for this final regulation (RTI, 2004), several of the 

recreational marine and Small SI sectors are highly concentrated and thus have the potential for the 

emergence of imperfect competition and price-setting behavior. Nonetheless, our analysis 

suggests that mitigating factors will limit this potential for raising price above marginal cost and 

thus that the assumption of a competitive market structure is justified. Among the mitigating 

factors are the presence of substantial import competition, relative ease of entry, existing excess 

3

U.S. EPA. 2000. Guidelines for Preparing Economics Analyses, EPA-240-R-00-003, page 126; 1999. 

OAQPS Economic Analysis Resource Document, page 5-8. 

4

The number of firms in a market is not a necessary condition for a perfectly competitive market. See 

Robert H. Frank, Microeconomics and Behavior, 1991, McGraw-Hill, Incl., p. 33. 

9-19 
Final Regulatory Impact Analysis 

production capacity, and a historical tendency of market participants to compete on price. These 

markets are also mature markets, as evidenced by unit sales growing at the rate of population 

increases. Pricing power in such markets is typically limited, and empirical data indicates that 

price pressure has existed in these markets for years and firms in these markets are price takers.5 

In addition, the products produced within each market are somewhat homogeneous in that engines 

and equipment from one firm can be purchased instead of engines and equipment from another 

firm, enhancing competition. 

According to contestable market theory, oligopolies and even monopolies will behave very 

much like firms in a competitive market if it is possible to enter particular markets costlessly (i.e., 

there are no sunk costs associated with market entry or exit). This is the case with these markets 

as there is significant excess production capacity in both the Small SI and Marine SI industries, in 

part due to improved productivity and efficiency in current plants. Data on domestic plant 

capacity utilization rates are published by the U.S. Census (U.S. Census, 2005). The full 

production capability is defined as "the maximum level of production that an establishment could 

reasonably expect to attain under normal and realistic operating conditions fully utilizing the 

machinery and equipment in place." Recent domestic data for 2000 to 2004 indicate the internal 

combustion engine industry (NAICS 333618 Other Equipment Manufacturing) operated at 53 to 

73 percent of full production capability. Similar data for vessels (NAICS 336612 Boat Building) 

indicate this industry operated between 59 and 62 percent of full production capability. The small 

SI equipment industry (NAICS 333112, lawn & garden tractor and home & lawn garden 

equipment manufacturing) operated at 50 to 65 percent of full production capability. Idle 

production capacity also limits the ability of firms to raise prices, since competitors can easily 

capture market share by increasing their production at the expense of a producer that increases its 

prices. 

Finally, domestic producers face substantial competition from foreign manufacturers (RTI, 

2006). These overseas firms may have strong incentives to compete vigorously on price with the 

well-established U.S. firms. For all of these reasons it is appropriate to use a competitive market 

structure model to estimate the economic impacts of this proposal. 

9.2.2.3 Intermediate-Run Model 

In developing the multi-market partial equilibrium model, the choices available to 

producers must be considered. For example, are producers able to increase their factors of 

production (e.g., increase production capacity) or alter their production mix (e.g., substitution 

between materials, labor, and capital)? These modeling issues are largely dependent on the time 

horizon for which the analysis is performed. Three benchmark time horizons are discussed below: 

the very short run, the long run, and the intermediate run. This discussion relies in large part on 

the material contained in the OAQPS Economic Analysis Resource Guide (U.S. EPA, 1999). 

5

 RTI (2006). Historical Market Data and Trends, Industry Profile for Small SI Engines and Equipment, 

Section 2.5. Draft Report 

9-20 
Economic Impact Analysis 

The EIM models market impacts in the intermediate run. The use of the intermediate run 

means that some factors of production are fixed and some are variable. This modeling period 

allows analysis of the economic effects of the rule's compliance costs on current producers. As 

described below, a short-run analysis imposes all compliance costs on producers, while a long-run 

analysis imposes all costs on consumers. The use of the intermediate time frame is consistent with 

economic practices for this type of analysis. 

In the very short run, all factors of production are assumed to be fixed, leaving the directly 

affected entity with no means to respond to increased costs associated with the regulation (e.g., 

they cannot adjust labor or capital inputs). Within a very short time horizon, regulated producers 

are constrained in their ability to adjust inputs or outputs due to contractual, institutional, or other 

factors and can be represented by a vertical supply curve, as shown in Figure 9.2-1. In essence, 

this is equivalent to the nonbehavioral model described earlier. Neither the price nor quantity 

changes and the manufacturer’s compliance costs become fixed or sunk costs. Under this time 

horizon, the impacts of the regulation fall entirely on the regulated entity. Producers incur the 

entire regulatory burden as a one-to-one reduction in their profit. This is referred to as the 

“full-cost absorption” scenario and is equivalent to the engineering cost estimates. Although there 

is no hard and fast rule for determining what length of time constitutes the very short run, it is 

inappropriate to use this time horizon for this analysis because it assumes economic entities have 

no flexibility to adjust factors of production. 

Figure 9.2-1: Short Run: All Costs Born by Producers 

Price 

P 

Q 

S 

D 

Output 

In the long run, all factors of production are variable, and producers can be expected to 

adjust production plans in response to cost changes imposed by a regulation (e.g., using a different 

labor/capital mix). Figure 9.2-2 illustrates a typical, if somewhat simplified, long-run industry 

supply function. The function is horizontal, indicating that the marginal and average costs of 

9-21 
Final Regulatory Impact Analysis 

production are constant with respect to output.6 This horizontal slope reflects the fact that, under 

long-run constant returns to scale, technology and input prices ultimately determine the market 

price, not the level of output in the market. 

Market demand is represented by the standard downward-sloping curve. The market is 

assumed here to be competitive; equilibrium is determined by the intersection of the supply and 

demand curves. In this case, the upward shift in the market supply curve represents the 

regulation’s effect on production costs. The shift causes the market price to increase by the full 

amount of the per-unit control cost (i.e., from P to PN). With the quantity demanded sensitive to 

price, the increase in market price leads to a reduction in output in the new with-regulation 

equilibrium (i.e., Q to QN). As a result, consumers incur the entire regulatory burden as 

represented by the loss in consumer surplus (i.e., the area P ac PN). In the nomenclature of EIAs, 

this long-run scenario is typically referred to as “full-cost pass-through” and is illustrated in Figure 

9.2-2. 

Figure 9.2-2: Long Run: Full-Cost Pass-Through 

$ d 

Increase 

Q1 Q0 

Unit Cost Increase }

c 

a 

b S1

: With Regulation P} 1 Price 

P0 S0

: Without Regulation 

D 

Output 

Taken together, impacts modeled under the long-run/full-cost-pass-through scenario reveal 

an important point: under fairly general economic conditions, a regulation's impact on producers is 

transitory. Ultimately, the costs are passed on to consumers in the form of higher prices. 

6

 The constancy of marginal costs reflects an underlying assumption of constant returns to scale of 

production, which may or may not apply in all cases. 

9-22 
Economic Impact Analysis 

However, this does not mean that the impacts of a regulation will have no impact on producers of 

goods and services affected by a regulation. For example, the long run may cover the time taken 

to retire all of today's capital vintage, which could take decades. Therefore, transitory impacts 

could be protracted and could dominate long-run impacts in terms of present value. In addition, to 

evaluate impacts on current producers, the long-run approach is not appropriate. Consequently a 

time horizon that falls between the very short-run/full-cost-absorption case and the 

long-run/full-cost-pass-through case is most appropriate for this EIA. 

The intermediate run time frame allows examination of impacts of a regulatory program 

during the transition between the short run and the long run. In the intermediate run, some factors 

are fixed; some are variable. In other words, producers can adjust some, but not all, factors of 

production, meaning they will bear some portion of the costs of the regulatory program. The 

existence of fixed production factors generally leads to diminishing returns to those fixed factors. 

This typically manifests itself in the form of a marginal cost (supply) function that rises with the 

output rate, as shown in Figure 9.2-3. 

Figure 9.2-3: Intermediate Run: Partial-Cost Pass-Through 

P1 

P0 

c 

b 

a 

$ g 

e 

d 

f 

S1: With Regulation 

S0: Without Regulation Price 

Increase }

Unit Cost Increase } 

Q1 Q0 Output 

Again, the regulation causes an upward shift in the supply function. The lack of resource 

mobility may cause producers to suffer profit (producer surplus) losses in the face of regulation; 

however, producers are able to pass through some of the associated costs to consumers, to the 

extent the market will allow. As shown, in this case, the market-clearing process generates an 

increase in price (from P to PN) that is less than the per-unit increase in costs, so that the regulatory 

9-23 
Final Regulatory Impact Analysis 

burden is shared by producers (net reduction in profits) and consumers (rise in price). In other 

words, there is a loss of both producer and consumer surplus. 

Consistent with other economic impact analyses performed by EPA, this EIM uses an 

intermediate run approach. This approach allows us to examine the market and social welfare 

impacts of the program as producers adjust their output and consumers adjust their consumption of 

affected products in response to the increased production costs. During this period, the 

distribution of the welfare losses between producer and consumer depends in large part on the 

relative supply and demand elasticity parameters used in the model. For example, if demand for 

Small SI equipment is relatively inelastic (i.e., demand does not decrease much as price increases), 

then most of the direct compliance cost on refiners will be passed along to Small SI equipment 

consumers in the form of higher prices. 

9.2.3 How is the EIM Used to Estimate Economic Impacts? 

9.2.3.1 Estimation of Market Impacts (Single Market) 

A graphical representation of a general economic competitive model of price formation, as 

shown in Figure 9.2-4(a), posits that market prices and quantities are determined by the 

intersection of the market supply and market demand curves. Under the baseline scenario, a 

market price and quantity (p,Q) are determined by the intersection of the downward-sloping 

market demand curve (DM) and the upward-sloping market supply curve (SM). The market supply 

curve reflects the sum of the domestic (Sd) and import (Si) supply curves. 

9-24 
Economic Impact Analysis 

Figure 9.2-4: Market Equilibrium without and with Regulation 

p 

Sd Sf SM 

DM 

+ p = p

qd qf Q 

Domestic Supply Foreign Supply Market 

a) Baseline Equilibrium 

p 

Sf 

SM′

DM 

+ p = p

p′

Sd SM 

p′ p′

S′

d 

S′

f 

q′

d qd q′f qf Q′ Q 

Domestic Supply Foreign Supply Market 

b) With-Regulation Equilibrium 

With the regulation, the costs of production increase for suppliers. The imposition of these 

regulatory control costs is represented as an upward shift in the supply curve for domestic and 

import supply by the estimated compliance costs. As a result of the upward shift in the supply 

curve, the market supply curve will also shift upward as shown in Figure 9.2-3(b) to reflect the 

increased costs of production. 

At baseline without the final rule, the industry produces total output, Q, at price, p, with 

domestic producers supplying the amount qd and imports accounting for Q minus qd, or qf

. With 

the regulation, the market price increases from p to pN, and market output (as determined from the 

market demand curve) decreases from Q to QN. This reduction in market output is the net result of 

reductions in domestic and import supply. 

9-25 
Final Regulatory Impact Analysis 

As indicated in Figure 9.2-4, when the final standards are applied the supply curve will 

shift upward by the amount of the estimated compliance costs. The demand curve, however, does 

not shift in this analysis. This is explained by the dynamics underlying the demand curve. The 

demand curve represents the relationship between prices and quantity demanded. Changes in 

prices lead to changes in the quantity demanded and are illustrated by movements along a fixed 

demand curve. In contrast, changes in any of the other variables would lead to change in demand 

and are illustrated as shifts in the position of the demand curve.7

 For example, an increase in the 

number of consumers in a market would cause the demand curve to shift outward because there are 

more individuals willing to buy the good at every price. Similarly, an exogenous increase in 

nominal income would also lead the demand curve to shift outward as people choose to buy more 

of a good at a given price. Changes in the prices of related good and tastes or preferences can also 

lead to demand curve shifts. 

The final standards are expected to increase the costs of production in the Small SI engine 

and equipment and Marine SI engine vessel markets and ultimately lead to higher equilibrium 

prices in the affected markets. As these prices increase, the quantity demanded falls (i.e., the price 

change leads to a movement along the demand curve).8

 However, the final program is not 

expected to lead to shifts in the demand curve for several reasons. First, the assume the program 

will not directly influence prices of related goods (i.e., prices of any potential substitutes remain 

constant in the analysis). In addition, the program will not change nominal incomes through 

public finance mechanisms (e.g., lump sum subsidies/taxes) or change labor supply decisions. 

Finally, we assume tastes and preference will not change during the period of analysis. For all of 

these reasons, it would be inappropriate to shift the demand curve for this analysis. 

9.2.3.2 Incorporating Multi-Market Interactions 

The above description is typical of the expected market effects for a single product markets 

(e.g., Small SI handheld and Class I nonhandheld; personal watercraft) considered in isolation. 

However, several of the markets considered in this EIA are more complicated because the engine 

and equipment manufacturers are not integrated. 

When both engine and equipment markets are considered separately, the regulatory 

program will affect equipment producers in two ways. First, equipment producers are affected by 

higher input costs (increases in the price of gasoline engines) associated with the rule. Second, the 

standards will also impose additional production costs on equipment producers associated with 

7

 An accessible detailed discussion of these concepts can be found in Chapter 5-7 of Nicholson’s (1998) 

intermediate microeconomics textbook. 

8

 Nicholson (1998) provides an example of the effects of a price increase on the quantity consumed (p: 134-

135). Throughout this discussion, we use uncompensated Marshallian demand functions. As a result, a price 

increase will also change an individual’s “real” income and reinforce substitution quantity responses to a good’s 

price change through an “income” effect. Both substitution and (real) income effects are therefore built in the 

Marshallian demand function used for this analysis. It is important to note, however, that this type of “income” 

effect is conceptually different from an exogenous change in nominal income that leads to a shift in a demand 

function. 

9-26 
Economic Impact Analysis 

equipment changes necessary to accommodate changes in engine design. In the sections that 

follow, we describe the demand relationships between these markets and how they are 

incorporated in the economic model. 

In markets such as Class II nonhandheld or SD/I marine, the demand for engines is directly 

linked to the production of equipment or vessels that uses those engines.9 This means that it is 

reasonable to assume that the input-output relationship between the gasoline engines and the 

equipment is strictly fixed and that the demand for engines varies directly with the demand for 

equipment.10 A demand curve specified in terms of its downstream consumption is referred to as a 

derived demand curve. Figure 9.2-5 illustrates how a derived demand curve is identified. 

9

 In marine applications, one or two engines are used per boat, depending on its intrinsic design, and this 

configuration is insensitive to small changes in engine used. In the case of Small SI equipment, the one-to-one 

correspondence is exact. Furthermore, there is no potential for technical substitution, i.e., to make gasoline 

equipment one needs a gasoline engine. 

10 This one-to-one relationship holds for engines sold on the market and for engines consumed internally by 

integrated engine/equipment manufacturers. 

9-27 
S

S

∆Peng 

Price 

Engines 

($/Q) 

Q – Engines ∆Q 

Final Regulatory Impact Analysis 

Figure 9.2-5: Derived Demand for Engines 

Price 

Equipment 

($/Q) 

∆PE 

Q – Equipment ∆QE 

DE 

N

SE 

SE 

SN

eng 

Seng 

} Unit Cost Increase 

Derived 

Demand 

eng 

∆QE = ∆Qeng 

Consider an event in the marine equipment market that causes the price of equipment to 

increase by )P (such as an increase in the price of engines). This increase in the price of 

equipment will cause the supply curve in the equipment market to shift up, leading to a decreased 

quantity ()QE). The change in equipment production leads to a decrease in the demand for 

engines ()QEng). The new point (QE – )QE, P – )P) traces out the derived demand curve. Note 

that the supply and demand curves in the marine equipment markets are needed to identify the 

derived demand in the engine market. All of the market supply and demand curves and the 

elasticity parameters used in the EIM are described in Appendix 9E 

9-28 
Economic Impact Analysis 

9.2.3.3 Estimation of Social Costs 

The economic welfare implications of the market price and output changes with the 

regulation can be examined by calculating consumer and producer net “surplus” changes 

associated with these adjustments. This is a measure of the negative impact of an environmental 

policy change and is commonly referred to as the “social cost” of a regulation. It is important to 

emphasize that this measure does not include the benefits that occur outside of the market, that is, 

the value of the reduced levels of air pollution with the regulation. Including this benefit will 

reduce the net cost of the regulation and even make it positive. 

The demand and supply curves that are used to project market price and quantity impacts 

can be used to estimate the change in consumer, producer, and total surplus or social cost of the 

regulation (see Figure 9.2-6). 

The difference between the maximum price consumers are willing to pay for a good and 

the price they actually pay is referred to as “consumer surplus.” Consumer surplus is measured as 

the area under the demand curve and above the price of the product. Similarly, the difference 

between the minimum price producers are willing to accept for a good and the price they actually 

receive is referred to as “producer surplus.” Producer surplus is measured as the area above the 

supply curve below the price of the product. These areas can be thought of as consumers’ net 

benefits of consumption and producers’ net benefits of production, respectively. 

In Figure 9.2-6, baseline equilibrium occurs at the intersection of the demand curve, D, and 

supply curve, S. Price is Pl

 with quantity Ql. The increased cost of production with the regulation 

will cause the market supply curve to shift upward to SN. The new equilibrium price of the product 

is P2. With a higher price for the product there is less consumer welfare, all else being unchanged. 

In Figure 9.2-6(a), area A represents the dollar value of the annual net loss in consumers’ welfare 

associated with the increased price. The rectangular portion represents the loss in consumer 

surplus on the quantity still consumed due to the price increase, Q2, while the triangular area 

represents the foregone surplus resulting from the reduced quantity consumed, Ql – Q2. 

In addition to the changes in consumers’ welfare, there are also changes in producers’ 

welfare with the regulatory action. With the increase in market price, producers receive higher 

revenues on the quantity still purchased, Q2. In Figure 9.2-6(b), area B represents the increase in 

revenues due to this increase in price. The difference in the area under the supply curve up to the 

original market price, area C, measures the loss in producer surplus, which includes the loss 

associated with the quantity no longer produced. The net change in producers’ welfare is 

represented by area B – C. 

9-29 
Final Regulatory Impact Analysis 

Figure 9.2-6: Market Surplus Changes with Regulations 

Consumer and Producer Surplus 

P 1 

P 2 

S 

S′

D 

$/Q 

A 

Q2 Q1 Q/t 

(a) Change in Consumer Surplus with 

Regulation 

$/Q 

P 2 

P 1 

S 

S′

D 

B 

C 

Q 2 Q 1 Q/t 

(b) Change in Producer Surplus with 

Regulation 

P 1 

P 2 

S 

S′

D 

$/Q 

D 

Q2 Q1 Q/t 

(c) Net Change in Economic Welfare with 

Regulation 

9-30 
Economic Impact Analysis 

The change in economic welfare attributable to the compliance costs of the regulations is 

the sum of consumer and producer surplus changes, that is, –(A) + (B–C). Figure 9.2-6(c) shows 

the net (negative) change in economic welfare associated with the regulation as area D. 

9.2.4 How Are Special Market Characteristics Addressed? 

In addition to the general model features described in Section 9.2.2, there are several 

specific characteristics of the Small SI and Marine SI markets that need to be addressed in the 

EIM. These are the treatment of fixed and variable costs, fuel savings, programmatic flexibilities, 

and substitution, and distribution systems effects. 

9.2.4.1 Fixed and Variable Costs in a Competitive Market 

The estimated engineering compliance costs, consisting of fixed costs (R&D, 

capital/tooling, certification costs), variable costs, and operating costs provide an initial measure of 

total annual compliance costs without accounting for behavioral responses. The starting point for 

assessing the market impacts of a regulatory action is to incorporate the regulatory compliance 

costs into the production decision of the firm. 

In general, shifting the supply curve by the total cost per unit implies that both capital and 

operating costs vary with output levels. At least in the case of capital, this raises some questions. 

In the long run, all inputs (and their costs) can be expected to vary with output. But a short(er)-run 

analysis typically holds some capital factors fixed. For instance, to the extent that a market supply 

function is tied to existing facilities, there is an element of fixed capital (or one-time R&D). As 

indicated above, the current market supply function might reflect these fixed factors with an 

upward slope. As shown in Figure 9.2-7, the marginal cost (MC) curve will only be affected, or 

shift upwards, by the per-unit variable compliance costs (c1= TVCC/q), while the average total 

cost (ATAC) curve will shift up by the per-unit total compliance costs (c2 = TCC/q). Thus, the 

variable costs will directly affect the production decision (optimal output rate), and the fixed costs 

will affect the closure decision by establishing a new higher reservation price for the firm (i.e., 

Pm'). In other words, the fixed costs are important in determining whether the firm will stay in this 

line of business (i.e., produce anything at all), and the variable costs determine the level (quantity) 

of production. 

9-31 
Final Regulatory Impact Analysis 

Figure 9.2-7: Modeling Fixed Costs 

$/q MCN

MC 

TVCC 1 =C

q 

ATACN TCC C2 = Pm q N ATAC 

Pm 

qm qmN qM q/t 

(a) Upward-sloping supply function 

Depending on the industry type, fixed costs associated with complying with a new 

regulation can generally be treated differently in an analysis of market impacts. In a competitive 

market, the industry supply curve is generally based on the market’s marginal cost curve; fixed 

costs do not influence production decisions at the margin. Therefore, the market anlaysis for a 

competitive market is based on variable costs only. 

The nature of the Small SI and Marine SI markets suggests the market supply curve shifts 

in the model should include fixed compliance cost and variable compliance cost. This is because 

Small SI and Marine SI engine and equipment manufacturers produce a product that changes very 

little over time. These manufacturers may not engage in research and development to improve 

their products on a continuous basis (as opposed to highway vehicles or nonroad engines and 

equipment). In this case, the product changes that would be required to comply with the final 

standards would require these manufacturers to devote new funds and resources to product 

redesign and facilities changes. In this situation, Small SI and Marine SI engine and equipment 

manufacturers would be expected to increase their prices in attempting to recover both fixed and 

variable costs. This is in contrast to the nonroad diesel engine and equipment markets: 

manufacturers in those markets generally allocate redesign resources each year to accommodate a 

changing market. As stated in the section 9.3.3, this analysis applied fixed costs in the year in 

which they occur prior to the rule taking effect, and variable costs during the years that the rule is 

implemented. To reflect these conditions, the supply shift in this EIM is based on either fixed costs 

prior to the rule or variable costs after the rule starts, even though the model assumes a competitive 

market structure. 

9-32 
Economic Impact Analysis 

9.2.4.2 Fuel Savings and Fuel Taxes 

If all the costs of the regulation are not reflected in the supply shift, then the producer and 

consumer surplus changes reflected in Figure 9.2-6(c) will not capture the total social costs of the 

regulation. This will be the case, for example, if there are cost savings attributable to a program 

that are not readily apparent to consumers. 

In this case, the final evaporative and exhaust controls are expected to result in fuel savings 

for users. Small SI engine and equipment manufacturers are expected to use fuel injection 

techniques to comply with the final standards for some of their two-cylinder Class II engines. 

These fuel injected engines are expected to have better fuel efficiency than carbureted engines. 

Marine SI manufacturers are expected to use 4-stroke and direction-injection 2-stroke technology 

for outboards and PWC. In addition, all sterndrive and inboard engines are expected to use fuel 

injection. These technologies are expected to result in reductions in fuel consumption. 

These fuel savings are not included in the market analysis for this economic impact 

analysis. This is because all available evidence suggests that fuel savings do not affect consumer 

decisions with respect to the purchase of this equipment. Unlike motor vehicles or other consumer 

goods, neither Small SI nor Marine SI equipment is labeled with expected fuel consumption or 

expected annual operating costs. Therefore, there is no information available for the consumer to 

use or make this decision. Instead consumers base their purchase decision on other attributes of 

the product for which the manufacturer provides information. For lawn mowers this may be the 

horsepower of the engine, whether the machine has a bag or has a mulching feature, its blade size, 

etc. For PWC it may be how many people it can carry, its maximum speed, its horsepower, etc. In 

many cases, especially for Small SI equipment, the consumer may not even be aware of the fuel 

savings when operating the equipment, especially if he or she uses the same portable fuel storage 

container to fuel several different pieces of equipment. 

These fuel savings are included in the social cost analysis. This is because they are savings 

that accrue to society. These savings are attributed to consumers of the relevant equipment. As 

explained in more detail in 9.3.5, the social cost analysis is based on the equivalent of the pre-tax 

price of gasoline in that analysis. Although the consumer will realize a savings equal to the pump 

price of gasoline (post-tax), part of that savings is offset by a tax loss to governmental agencies 

and is thus a loss to consumers of the services supported by those taxes. This tax revenue loss, 

considered a transfer payment in this analysis, does not affect the benefit-cost analysis results. 

9.2.4.3 Flexibility Provisions 

Consistent with the engineering cost estimates, the EIM does not include cost savings 

associated with compliance flexibility provisions or averaging, banking, and trading provisions. 

As a result, the results of this EIA can be viewed as somewhat conservative. 

9.2.4.4 Substitution 

Gasoline-powered SI engines convert the potential energy contained in the fuel into 

mechanical energy, which can then be used to do useful work, to provide locomotion, and/or to 

9-33 
Final Regulatory Impact Analysis 

generate electricity. These machines are technologically similar compression-ignition engines 

powered by diesel fuel, and often compete in the same equipment and applications markets. 

Similarly, electric motors are capable of performing many of the same tasks as gasoline engines in 

small and inexpensive equipment. 

The relationships modeled in the EIM do not include substitution away from Small SI and 

Marine SI engines and equipment to diesel or electric alternatives. This is appropriate because 

consumers are not likely to make these substitutions. Diesel engines’ superior efficiency in energy 

conversion makes them more attractive for large engines, and for those with long required service 

lives, whether measured in operating hours or years of service. Gasoline-powered engines, on the 

other hand, have lower initial cost, and utilization in garden or recreational activities is not high 

enough for diesel fuel efficiency to overcome this gasoline advantage. On the SI marine side, the 

current population of recreational boats is overwhelmingly powered by gasoline engines, even in 

the large horsepower classes where diesel’s superior efficiency would seem to provide significant 

cost advantages, and gasoline engines are the prevalent choice for garden equipment and 

residential generators. On the Small SI side, substitution to diesel is not a viable option for most 

residential consumers, either because diesel equipment does not exist (e.g., diesel string trimmers) 

or because there would be a large price premium that would discourage the use of diesel 

equipment (e.g., diesel lawnmowers and diesel recreational marine vessels). In addition, most 

households are not equipped to handle the additional fuel type and misfueling would carry a high 

cost. Finally, the lack of a large infrastructure system already in place like the one supporting the 

use of gasoline equipment for residential and recreational purposes, including refueling and 

maintenance, represents a large barrier to substitution from gasoline to diesel equipment. With 

regard to electric alternatives, the impact of substitution to electric for Small SI equipment (there 

are no comparable options for Marine SI) is also expected to be negligible. Gasoline is the power 

source of choice for small and inexpensive equipment due to its low initial cost. Gasoline 

equipment is also inherently portable, which make them more attractive to competing electric 

equipment that must be connected with a power grid or use batteries that require frequent 

recharging. Data that would allow investigation of the details of this clear consumer preference 

are not available, but it is reasonable to assume that increases in the cost of gasoline engines of the 

magnitude associated with this program would not cause widespread substitution to diesel or 

electric alternatives. 

9.2.4.5 Distribution System Effects 

The market interactions modeled in the EIM are those between producers and consumers of 

the specified engines and equipment that use those engines. The EIM does not consider sales 

distribution networks or how the regulated goods are sold to final consumers through wholesalers 

and/or retailers. This is appropriate because the final regulatory program does not impose 

additional costs on the distribution networks and those relationships are not expected to change as 

a result of the standards. 

In the case of Small SI equipment, however, concerns have been raised about the potential 

for dominant retailers (big box stores such as Wal-Mart, Sears and K-Mart) to affect market 

equilibria and the ability of manufacturers to pass along cost increases associated with new 

9-34 
Economic Impact Analysis 

emission control requirements. Specifically, some Small SI equipment manufacturers assert that 

Big Box stores impose a price structure that would force them to absorb the compliance costs 

associated with the final standards. They contend that this is a relatively new phenomenon for 

their market and that EPA should consider these effects in the economic impact analysis for this 

proposal. 

Dominant retailers are a fairly well-understood sector of the consumer good distribution 

network, especially with regard to clothing and household goods. These stores reduce product 

prices by exerting important influences on relevant producers. Specifically, they discipline 

markets by encouraging manufacturers to compete on price, and force inefficient firms to cut costs 

or leave the market. 

Dominant retailers may also prevent efficient producers from passing on extra increases in 

fixed costs to consumers, including R&D costs associated with engine or equipment redesign. So, 

for example, it may be the case that if a particular firm redesigns a lawnmower to produce more 

power a dominant retailer may not choose to change its pricing structure to account for that 

redesign. Nevertheless, the firm may still choose to incorporate the design change in the hope of 

capturing a greater share of the market and/or improve its name recognition. 

It is unlikely, however, that a dominant retailer could prevent firms from passing on 

market-wide increases in average costs or marginal costs in response to a regulatory program. 

Profit maximizing manufacturers will continue to follow a marginal cost equals price pricing rule 

regardless of the distribution arrangements. A dominant retailer could not force the manufacturer 

to produce units where the marginal cost exceeds the price. If large retail distributors attempted to 

prevent efficient manufacturers from raising prices in response to the standards, manufacturers 

would likely respond to a retailer’s price pressure by reducing output. This would result in large 

excess demand in the equipment market which would ultimately have to be satisfied through some 

sort of arbitrage mechanism to a new higher equilibrium price. 

An individual manufacturing company has little, if any, ability to pass on a cost increase if 

it is the only entity affected by that cost increase. In such a case, retailers would clearly have an 

incentive to purchase comparable engines or equipment that were not affected by the cost increase, 

placing the affected firm at a competitive disadvantage and reducing its market share. However, in 

this case all engine manufacturers will face increased average costs or marginal costs of 

production associated with the regulatory program. Therefore, the program does not necessarily 

put one engine manufacturer at a competitive disadvantage, although manufacturers that can more 

easily accommodate the new requirements will likely see lower costs than those who cannot. 

9.3 EIM Data Inputs and Model Solution 

9-35 
Final Regulatory Impact Analysis 

The EIM is a computer model comprised of a series of spreadsheet modules that simulate 

the supply and demand characteristics of the markets under consideration. The model equations, 

presented in Appendix D to this chapter, are based on the economic relationships described in 

Section 9.2. The EIM analysis consists of four basic steps: 

•	 Define the initial equilibrium conditions of the markets under consideration 

(equilibrium prices and quantities and behavioral parameters; these yield 

equilibrium supply and demand curves). 

•	 Introduce a policy "shock" into the model based on estimated compliance costs that 

shift the supply functions. 

•	 Use a solution algorithm to estimate a new, with-regulation equilibrium price and 

quantity for all markets. 

•	 Estimate the change in producer and consumer surplus in all markets included in 

the model. 

Supply responses and market adjustments can be conceptualized as an interactive process. 

Producers facing increased production costs due to compliance are willing to supply smaller 

quantities at the baseline price. This reduction in market supply leads to an increase in the market 

price that all producers and consumers face, which leads to further responses by producers and 

consumers and thus new market prices, and so on. The new with-regulation equilibrium reflects 

the new market prices where total market supply equals market demand. 

The remainder of this section describes the data used to construct the EIM: initial 

equilibrium market conditions (equilibrium prices and quantities), compliance cost inputs, and 

model elasticity parameters. Also included is a brief discussion of the analytical expression used 

to estimate with-regulation market conditions. 

9.3.1 Description of Product Markets 

This EIM estimates the behavioral responses of the Small SI and Marine SI markets to the 

cost of complying with the final emission control program. Each of these markets is very briefly 

described below. More information can be found in the industry characterizations prepared for 

this proposal (Chapter 1 and RTI 2006). 

9.3.1.1 Small SI Market 

The Small SI market is the market for a variety of nonroad equipment powered by twostroke or four-stroke spark-ignition engines rated up to 19 kW (25 hp). This economic impact 

assessment distinguishes between two Small SI market sectors: handheld and nonhandheld. The 

handheld (HH) sector consists generally of equipment that is carried by the operator and is 

operated multipositionally, although some equipment in this category may have two wheels. HH 

equipment includes string trimmers, edgers, leaf blowers, and chain saws. The nonhandheld 

(NHH) sector consists mostly of wheeled equipment such as lawn mowers, garden tractors, and 

wheeled trimmers, blowers, and edgers. Also included in the Small SI market are generators, 

9-36 
Economic Impact Analysis 

compressors, and construction, agricultural, and small industrial equipment, as well as some 

recreational and utility vehicles and snowblowers. 

The HH market can be characterized as an integrated market in which producers 

manufacture both the engine and the associated equipment. In the NHH market, in contrast, the 

engine and equipment manufacturers are typically separate entities. Engines produced by a 

manufacturer for use in its own equipment are called “captive” engines. Engines produced by 

manufacturers for sale on the open market to anyone who wants to buy them are called “merchant” 

engines. This distinction is important because compliance costs affect captive and merchant 

engines differently. Engine-related compliance costs for captive engines are absorbed into the 

equipment costs of integrated suppliers in their entirety. In contrast, nonintegrated suppliers who 

buy merchant engines absorb only part of the engine compliance costs into their equipment costs; 

the rest is borne by the engine manufacturer. Depending on the price sensitivity of demand in the 

engine market, the pass-through of engine compliance costs to the equipment manufacturer may be 

larger (more inelastic demand) or smaller (more elastic demand). 

This analysis makes the simplifying assumption that virtually all Small SI equipment is 

sold to residential end-users for their personal use and a negligible number are sold to commercial 

entities for use as an input to the production of goods or services. This simplifying assumption 

allows us to disregard the impact of the compliance costs on the production of goods and services 

that would have Small SI equipment as an input. Any such impacts would be expected to be 

negligible given the relative share of Small SI equipment to any such production processes. This 

assumption is supported by data from the Outdoor Power Equipment and Engine Service 

Association (OPEESA), contained in Table 9.3-1, which indicates that only about 3 percent of the 

NHH products sold in 2003 and 2004 were sold to commercial users. The rest, 97 percent, were 

sold to residential users. While this data reflects only NHH equipment, a similar situation likely 

exists for HH equipment given the nature of that equipment (light-duty lawn and garden equipment 

or gensets). Recent EPA certification data also supports this simplifying assumption. According 

to model year 2005 data, about 5 percent of Class I and 7 percent of Class II engines were high 

hour useful life (commercial) categories, or a total of about 9 percent of Classes I and II combined. 

About 19 percent of HH engines were high useful life categories. 

Table 9.3-1: Share of Residential and Commercial Small SI Shipments (Various years) 

2003 2004 

Total Commercial Turf Products 297,085 234,475 

Total Consumer NHH Products 8,598,901 8.188,614 

Commercial Unit Volume NHH Share 3.3% 2.8% 

HH products (assumed consumer) 12,600,440 11,949,557 

Commercial share - all Small SI 1.4% 1.2% 

Source: Outdoor Power Equipment & Engine Service Association, 2004. 

The analysis also assumes that there is a one-to-one correspondence between engines and 

equipment (there is only one engine per equipment unit) and that there is no market for loose 

9-37 
Final Regulatory Impact Analysis 

engines. These assumptions are reasonable given the nature of this equipment and because owners 

generally do not repower this equipment when the engine fails; instead, they repair the engine or 

replace the equipment. This assumption makes it possible to estimate the number of engines 

produced directly from the number of equipment. 

9.3.1.1.1 Handheld Market 

The HH engine market consists of Class III (< 20 cc), IV (20-50 cc) and V (>50 cc) 

engines. These engines are used in similar types of equipment, all of which are small and 

relatively lightweight. According to the industry profile prepared for this rule, the HH market is 

an integrated market in that about 90 percent of HH engines are “captive” engines, with the engine 

and equipment manufacturer being the same company (RTI, 2006). An integrated market means 

the EIM can use a one-market approach. 

For the purpose of this analysis, all HH engines and equipment are grouped into one 

engine/equipment market. This is reasonable both because it is an integrated market and because 

the estimated compliance costs for the HH standards are expected to be similar for all types of HH 

engines and equipment regardless of size or application. The final standards for HH consist only 

of evaporative emission controls and the cost to comply with the standards are primarily related to 

fuel tank volume and fuel hose length, which do not vary significantly for most equipment. 

9.3.1.1.2 Nonhandheld Market 

The NHH engine market consists of Class I (<225 cc) and Class II (>225 cc) engines. 

There are three useful life categories for each and the costs for complying with the exhaust 

standards will vary by useful life category for each engine class. According to the industry profile 

prepared for this rule, the NHH market is not integrated in that about 95 percent of Class I and 

Class II NHH engines are merchant engines (RTI, 2006). The model thus explores the impacts on 

engine producers and equipment producers separately. This means it is necessary to use a twomarket approach, with the engine and equipment markets sharing some of the compliance costs 

and consumers bearing the rest. 

Snowblowers engines are treated differently under EPA’s final program. The final 

program would impose only evaporative controls on these engines. Because Class I manufacturers 

of snowblower engines make the whole engine as a set (i.e., including fuel tank and fuel lines), it 

was decided to place all of the compliance costs on the engine manufacturer. These manufacturers 

are expected to produce a separate snowblower engine to be used in this equipment. Class II 

engines are commonly sold without fuel tanks, and so the evaporative controls for Class II 

snowblowers are attributed to the equipment manufacturer. 

The nine Small SI nonhandheld engine markets are summarized in Table 9.3-2. 

Table 9.3-2: Small SI Nonhandheld Engine Categories 

9-38 
Economic Impact Analysis 

Class Useful Life 

Class I 125 hours 

250 hours 

500 hours 

Class I - Snowblower 125 hours 

250 hours 

500 hours 

Class II 250 hours 

500 hours 

1000 hours 

The EIM includes eight types of NHH equipment, as described in Table 9.3-3. However, 

because not all engine/equipment combinations are applicable, there are a total of 40 

engine/equipment markets. Specifically, there are no Class II lawnmowers, there are no Class I 

tractors, and all equipment in the “other lawn and garden” category using Class I engines are in the 

UL125 grouping. 

Table 9.3-3: Nonhandheld Equipment Categories 

Equipment Class I Class II 

Agriculture/construction/general industrial Yes Yes 

Utility and recreational vehicles Yes Yes 

Lawn mowers Yes No 

Tractors No Yes 

Lawn and garden, other UL125 only Yes 

Gensets/welders Yes Yes 

Pumps/compressors/pressure washers Yes Yes 

Snowblowers Yes Yes 

9.3.1.2 Marine SI market 

The Marine SI market is the market for a variety of marine vessels powered by gasoline 

engines. These final Marine SI standards discussed here are for propulsion engines only. 

Auxiliary Marine SI engines <37 kW are included as Small SI engines for this rule. Larger 

auxiliary Marine SI engines were covered in the new standards for Large SI engines. Many of the 

auxiliary Marine SI engines are being designed with catalysts independent of the final standards, 

so the final standards will codify what is already happening in the industry and force new entrants 

9-39 
Final Regulatory Impact Analysis 

in the market to employ the same types of emission controls. Given that the industry is already 

using catalysts, the estimated costs of complying are with the final standards are negligible. These 

engines typically use the same fuel tank as the propulsion engines so evaporative emission controls 

for these engines impose a nominal cost that is already covered in the vessel costs since the vessel 

costs include costs for hoses and tanks. The impact of treating marine Auxiliary Marine SI 

engines in this way are expected to be minimal because the number of vessels with installed 

auxiliary units is small and limited to sterndrive/inboard and outboard luxury vessels: about 21,700 

out of a total of 356,300 vessels. 

9.3.1.2.1 Marine SI Engine Markets 

Unlike Small SI engines that can be used in a variety of different types of equipment, 

Marine SI engines are designed and manufactured for specific applications. Engines used in 

sterndrive or inboard vessels are different from those used in outboard applications, and are made 

by different manufacturers. Outboards and SD/I engines produced for luxury vessels are different 

from those produced for the general market. Personal watercraft, on the other hand, are generally 

an integrated system. Taking this into consideration, there are 13 engine markets included in this 

EIA, based on design and horsepower. These are described in Table 9.3-4. 

Table 9.3-4: Marine SI Engine Markets 

Engine Design <25 hp 25-50 hp 51-100 hp 101-175 hp 176-300 hp >301 hp 

SD/I Recreation XXX XXX XXX 

SD/I Luxury XXX XXX 

OB Recreational XXX XXX XXX XXX XXX 

OB Luxury XXX XXX 

OB Loose XXX 

Similar to the Small SI market, most marine SI engines are used for recreational purposes. 

According to a 2000 study of the boat building industry, about 79 percent of Marine SI vessels are 

used for recreational purposes and only 7 percent for commercial purposes, with the remaining 14 

percent for other purposes (CCA, 2000).11 The propulsion system of choice for commercial 

marine vessels is diesel due to its greater reliability and lower fuel costs. The combustion 

characteristics of diesel engines also make them a better choice for vessels that are likely to spend 

large amounts of time at sea. While gasoline marine engines are used in applications such as 

lifeboats, patrol boats and small fishing vessels, their numbers are not large enough to warrant 

separate consideration in this Economic Impact Analysis. 

11This study looked at NAICS 336612 – establishments primarily engaged in building boats, defined as 

watercraft not built in shipyards and typically of the type suitable or intended for personal use; it is not clear what is 

meant by "other" in this study. 

9-40 
Economic Impact Analysis 

For the purposes of this analysis, all personal watercraft manufacturers are considered to be 

integrated manufacturers, and thus the engines are “captive.” This is reasonable because personal 

watercraft are similar to land-based recreational vehicles in that the engines are produced by the 

equipment manufacturer specifically for certain models. 

The other two primary types of SI marine engines are outboards and sterndrives/inboards 

(SD/I). For these engines, we model a merchant relationship between the engine manufacturers 

and boat builders. This is reasonable because these engines are typically sold on the open market 

(outboards) or sold internally but through a market-type relationship between the engine and the 

equipment businesses (SD/I). 

Outboard engines are typically produced by the engine manufacturer with little or no 

knowledge of what vessels the engines will be used on. Outboards are a self-contained assembly, 

with a power unit and drive unit, that can be fit to a wide range of boats. They may be used either 

with a portable fuel tank or connected to a fuel system installed on a vessel. In most cases, the 

engine manufacturer and boat builder are separate companies. However, it is becoming more 

common for engine manufacturing companies to purchase boat builders. Based on conversations 

with engine manufacturers and boat builders, we have received indications that this trend has not 

significantly changed the relationship between the engine business units and the boat building 

business units. The boat builders typically pay market price for the engines and there is little 

integration of design beyond a typical manufacturer/supplier relationship. It seems that engine 

manufacturers generally buy outboard vessel building companies to gain access to target markets 

rather than to develop an integrated design. Generally, the vessel is sold without the engine and 

the consumer chooses the engine at the point of sale. This means that the vessel builder may not 

be involved in the transaction and that the distribution of the compliance costs is between the 

engine builder and the end consumer rather than between the engine builder and the vessel builder. 

The relationship between engine manufacturers and boat builders is similar for SD/I 

engines as for outboard engines. One difference is that there are only two large businesses and 

many small businesses producing SD/I engines. These small businesses typically do not produce 

boats or own companies that do. SD/I engines are often sold to buyer groups created by boat 

builders to gain volume discounts on engines. Because of this, SD/I engine manufacturers often 

do not know what boats their engines are being used in. In the case where a large SD/I 

manufacturer has purchased boat building companies, the relationship is similar to that for 

outboards. Nevertheless, the distribution of compliance costs would be between the engine 

manufacturer and the vessel builder, since the engine is integrated in the final vessel design. 

9.3.1.2.2 Marine SI Equipment Markets 

There are five types of marine vessel markets: 

• SD/I recreational (runabouts, airboats, jetboats) 

• SD/I luxury (yachts, cruisers offshore) 

• OB recreational (runabouts, pontoons, fishing) 

• OB luxury (yacht, cruiser, express fish) 

9-41 
Final Regulatory Impact Analysis 

• Personal watercraft 

Of the 30 possible engine/vessel combinations, there are 15 combinations that are not 

applicable. For example, SD/I vessels use engines above 100 hp only. Personal watercraft use 

engines above 50 hp but do not use engines above 300 hp. This yields a total of 15 engine/vessel 

markets. 

Table 9.3-5: Marine SI Vessel Types 

Vessel <25 hp 25-50 hp 51-100 hp 101-175 hp 176-300 hp >301 hp 

PWC XXX XXX XXX 

SD/I Recreational XXX XXX XXX 

SD/I Luxury XXX XXX 

OB Recreational XXX XXX XXX XXX XXX 

OB Luxury XXX XXX 

Unlike Small SI equipment, there is not a one-to-one relationship between engines and 

equipment. Some vessels may have more than one propulsion engine. Table 9.3-6 shows the 

average number of engines per vessel assumed for the purposes of this analysis. In this table, OB 

engines per boat sale represents the average number of engines per outboard vessel in general. 

This average consists of three components: 1) some outboard vessels have more than one engine; 

2) engines that are made as replacement engines; and 3) loose engines that are not sold with the 

boat, such as “kicker” engines which are used for low speed trolling. 

Table 9.3-6: Average Number of Marine SI Engines per Vessel (2005) 

Vessel <25 hp 25-50 

hp 

51-100 

hp 

101-175 

hp 

176-300 

hp 

>301 hp Average 

PWC 1.00 1.00 1.00 1.00 

SD/I Recreational 1.00 1.02 1.01 1.01 

SD/I Luxury 1.25 1.52 1.39 

OB Recreational 1.25 1.25 1.29 1.29 1.29 1.28 

OB Luxury 2.50 2.50 2.50 

OB Engine/boat sale 1.47 

9.3.1.3 Market Linkages 

In the EIM, the Small SI and Marine SI markets are not linked (there is no feedback 

mechanism between the Small SI and Marine SI market segments). This is appropriate because 

the affected equipment is not interchangeable and because there is very little overlap between the 

engine producers in each market. These two sectors represent different aspects of economic 

activity (lawn and garden care and power generation as opposed to recreational marine) and 

9-42 
Economic Impact Analysis 

production and consumption of one product is not affected by the other. In other words, an 

increase in the price of lawnmowers is not expected to have an impact on the production and 

supply of personal watercraft, and vice versa. Production and consumption of each of these 

productions are the results of other factors that have little cross-over impacts (the need for 

residential garden upkeep or power generation; the desire for personal recreation). 

9.3.2 Market Equilibrium Conditions 

The starting point for the economic impact analysis is initial market equilibrium conditions 

(prices and quantities) that exist prior to the implementation of new standards. At pre-control 

market equilibrium conditions, consumers are willing to purchase the same amount of a product 

that producers are willing to produce at the market price. 

9.3.2.1 Small SI Initial Equilibrium Quantities and Prices 

9.3.2.1.1 Small SI Engine and Equipment Initial Equilibrium Quantities 

The EIM uses the same engine sales quantities that are used in the Small SI cost analysis 

presented in Chapter 6. The sales numbers for 2005 are reproduced in Tables 9.3-7 and 9.3-8. 

They are based on engine and equipment sales are for 49 states (all states except California) for 

2005. However, the sales numbers include construction and agriculture equipment sold in 

California, since that equipment is not covered by California’s small engine program. 

These engine sales numbers are taken from EPA’s NONROAD 2005 emission inventory 

model. To breakout the sales data by equipment, industry information from Power Systems 

Research database-OELink was used to characterize the distribution of equipment by the eight 

different equipment categories noted earlier. In addition, the sales within each equipment category 

were apportioned to the different useful life categories based on the fraction of engines certified in 

each class determined from EPA certification data for model year 2005. 

Because of the one-to-one correspondence between Small SI engines and equipment, the 

number of equipment is equal to the number of engines sold in a given year. 

Table 9.3-7: Small SI Handheld Engine and Equipment Sales (2005) 

Sales - All Handheld Engines, Equipment 

8,153,106 

9-43 
Final Regulatory Impact Analysis 

Table 9.3-8: Small SI Nonhandheld Engine and Equipment Sales (2005) 

Application 

Class I Class II Total 

UL 125 UL 250 UL 500 UL 250 UL 500 UL 1000 

Agricultural/Construction/ 

General Industrial/ 

Material Handling Equip 

Utility and Rec Vehicles 

Lawn Mowers 

Tractors 

Lawn and Garden Other 

Gensets/ Welders 

Pumps/ Compressors/ 

Pressure Washers 

71,682 

81,703 

5,895,706 

NA 

647,256 

271,391 

579,775 

7,675 

8,748 

631,254 

NA 

NA 

29,058 

62,077 

5,287 

6,026 

434,846 

NA 

NA 

20,017 

42,762 

71,380 

173,846 

NA 

1,701,351 

127,915 

605,169 

253,971 

15,503 

37,757 

NA 

369,516 

27,782 

131,437 

55,160 

17,585 

42,828 

NA 

419,141 

31,513 

149,088 

62,568 

189,112 

350,908 

6,961,805 

2,490,008 

834,465 

1,206,160 

1,056,313 

Snowblowers 551,509 59,050 40,677 475,353 103,242 117,107 1,346,938 

Total 8,099,022 797,861 549,615 3,408,985 740,396 839,829 14,435,709 

9.3.2.1.2 Small SI Engine and Equipment Initial Equilibrium Prices 

The initial equilibrium prices for Small SI engines and equipment are contained in Tables 

9.3-9 and 9.3-10. The engine prices were prices estimated by EPA using prices compiled from 

various websites and obtained from manufacturers. The engine prices were averaged for each 

useful life category for each class. The equipment prices were gathered through a survey of 

retailers, government dealers, and equipment websites (Caffrey, 2006). 

For the handheld market, although all costs are placed on the engine manufacturer, the 

engine and equipment manufacturers are integrated so only the equipment price is necessary for 

the analysis. 

Table 9.3-9: Small SI Handheld Engine and 

Equipment Prices (2005$) 

Equipment Price 

$210 

Table 9.3-10a: Small SI Nonhandheld Engine Prices (2005$) 

Class I Class II 

UL 125 

$125 

UL 250 

$217 

UL 500 

$218 

UL 250 

$208 

UL 500 

$409 

UL 1000 

$757 

9-44 
Economic Impact Analysis 

Table 9.3-10b: Small SI Nonhandheld Equipment Prices (2005$) 

Application 

Class I Class II 

UL 125 UL 250 UL 500 UL 250 UL 500 UL 1000 

Agricultural/Construction/ General 

Industrial/ Material Handling Equip 

Utility and Rec Vehicles 

Lawn Mowers 

Tractors 

Lawn and Garden Other 

Gensets/ Welders 

Pumps/ Compressors/ Pressure Washers 

Snowblowers 

$1,108 

$570 

$218 

$245 

$999 

$96 

$324 

$1,621 

$750 

$420 

$1,428 

$661 

$480 

$2,133 

$931 

$2,786 

$1,856 

$1,225 

$637 

$1,825 

$2,894 

$1,937 

$312 

$666 

$349 

$665 

$3,538 

$3,981 

$5,241 

$969 

$1,414 

$1,485 

$890 

$5,251 

$5,068 

$6,841 

$1,626 

$2,162 

$2,834 

$1,115 

9.3.2.2 Marine SI Initial Equilibrium Quantities and Prices 

9.3.2.2.1 Marine SI Engine and Equipment InitialEquilibrium Quantities 

The EIM uses the same engine sales quantities that are used in the Marine SI cost analysis 

presented in Chapter 6. The sales numbers for 2005 are reproduced in Tables 9.3-11 and 9.3-12. 

The engine sales data are derived for 2003 from certification databases for EPA and the California 

Air Resources Board and nationwide statistical data published by the National Marine 

Manufacturers Association (Samulski, 2004). These 2003 sales were adjusted to 2005 and future 

years using the growth rate described in 9.3.4. 

Table 9.3-11: Marine SI Engine Sales (2005) 

Vessel <25 hp 25-50 hp 51-100 hp 101-175 hp 176-300 hp >301 hp Total 

PWC 19,327 53,137 3,496 75,960 

SD/I Recreational 13,985 33,101 24,106 71,192 

SD/I Luxury 8,877 12,027 20,904 

OB Recreational 35,756 49,055 73,393 42,903 39,609 240,716 

OB Luxury 8,393 8,393 16,785 

OB loose engines 30,317 30,317 

Total 66,073 49,055 92,720 118,417 93,476 36,133 455,875 

9-45 
Final Regulatory Impact Analysis 

Table 9.3-12: Marine SI Vessel Sales (2005) 

Vessel <25 hp 25-50 hp 51-100 hp 101-175 hp 176-300 hp >301 hp Total 

PWC 19,327 53,137 3,496 75,960 

SD/I Recreational 13,985 32,383 23,799 70,168 

SD/I Luxury 7,081 7,927 15,009 

OB Recreational 28,605 39,244 56,780 33,191 30,644 188,464 

OB Luxury 3,357 3,357 6,714 

Total 28,605 39,244 76,107 103,670 76,961 31,727 356,314 

9.3.2.2.2 Marine SI Engine and Vessel Initial Equilibrium Prices 

The Marine SI engine and vessel initial equilibrium prices are contained in Tables 9.3-13 

and 9.3-14. They are based on advertised prices in trade literatures and on the web and on 

statistical data collected by the National Marine Manufacturers Association (Samulski, 2004). For 

the estimated vessel prices, replacement engines are included but are discounted at 7 percent for 

outboard recreational and luxury outboard and sterndrive vessels. The discount is used to account 

for the assumption that replacement engines are purchased several years after the boat is 

purchased. For this analysis, the discount is based on the average useful engine life estimates in 

the NONROAD2005 model. The original price data was 2003 data; these were adjusted by 

applying the Product Price Index Series published by the U.S. Bureau of Labor Statistics.12 

Table 9.3-13: Marine SI Engine Prices (2005$) 

Vessel <25 hp 25-50 hp 51-100 hp 101-175 hp 176-300 hp >301 hp 

PWC N/A N/A N/A 

SD/I Recreational $7,577 $12,604 $18,715 

SD/I Luxury $16,508 $31,959 

OB Recreational $2,606 $5,693 $9,114 $13,481 $20,786 

OB Luxury $26,001 $40,074 

OB loose engines $2,491 

12For Marine SI engines, the PPI for Gasoline Engines (except aircraft, automobile, highway truck, bus, and 

tank; PCU3336183336181) was used; the ratio for this index is 110.1/105.7 = 1.042. For marine vessel, the PPI for 

Boat Building (PCU 336612336612) was used; the ratio for this index is 206.7/194.2 = 1.064. 

9-46 
Economic Impact Analysis 

Table 9.3-14: Marine SI Vessel Prices* (2005$) 

Vessel <25 hp 25-50 hp 51-100 hp 101-175 

hp 

176-300 

hp 

>301 hp 

PWC $7,566 $9,982 $11,960 

SD/I Recreational $16,549 $32,356 $46,432 

SD/I Luxury $58,024 $205,658 

OB Recreational $3,658 $10,884 $21,561 $32,467 $49,420 

OB Luxury $65,097 $104,562 

*Includes replacement engines discounted at 7% for outboard recreational and luxury outboard 

in sterndrive/inboard vessels. 

9.3.3 Compliance Costs 

The social costs of the final standards are estimated by shocking the initial market 

equilibrium conditions by the amount of the compliance costs. The compliance costs used in this 

analysis are the engineering compliance costs described in Chapters 6 of this RIA and are 

summarized in this section. 

This analysis applies fixed costs in the year in which they occur prior to the rule taking 

effect. The small SI exhaust standards begin in 2011 for Class II and 2012 for Class I. Fixed costs 

are applied during 3 years (2008 to 2010) for Class II or 4 years (2008-2011) for Class I. The 

fixed costs include research and development, tooling, certification, and 1065 compliance. The 

marine exhaust standards generally begin in 2010; however, there are some exceptions for SD/I 

engines, where additional lead time was given in specific instances to provide regulatory 

flexibility. All fixed costs associated with marine exhaust standards are applied in the year of 

2008 and 2009. The implementation dates for the small SI evaporative emission standards are 

staggered beginning in 2008, with regulatory flexibility providing some small delays until as late 

as 2013. The implementation dates for the marine evaporative emission standards are staggered 

beginning in 2009, with regulatory flexibility providing some small delays until as late as 2015. 

Fixed costs due to evaporative emission standard are applied in the two years before the primary 

effective date for each of the evaporative emission standards (tank permeation, hose permeation, 

and diurnal emissions). For simplicity, all of the fixed costs associated with certification are 

applied in 2008 and 2009. Variable costs for either exhaust or evaporative emission standards on 

small SI and marine SI begin to be incurred only when the programs go into effect. 

9-47 
Final Regulatory Impact Analysis 

9.3.3.1 Small SI Market Compliance Costs 

The Small SI engine and equipment compliance costs are summarized in Tables 9.3-15 and 9.3-

16. There is one set of compliance costs for HH engines, since there is only one market. There are 

seven sets of engine compliance costs for NHH engines, one for each engine market. These costs 

begin in 2008 for HH and NHH; the costs changes over time reflecting the phase-in of the 

different standards. 

There are no equipment compliance cost estimates for HH or for Class I NHH equipment. 

Since the HH market is integrated, all costs are applied to engines. For NHH Class I equipment, 

the engine manufacturers typically produce a complete engine and fuel system package. Therefore, 

the final program is not expected to impose any additional costs on the equipment manufacturers. 

Costs are provided for NHH Class II equipment, reflecting the need for evaporative and emission 

controls. An average cost for Class II equipment was applied in this analysis to each of the 

equipment categories. 

Table 9.3-15: Compliance Costs per Engine - Small SI (2005$) 

Class 

Useful 

life 

Cost 

type 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017+ 

Handheld 

All engines Variable $0.00 $0.65 $0.65 $0.65 $0.84 $0.84 $0.71 $0.71 $0.71 $0.71 

Fixed $0.30 $0.30 $0.27 $0.26 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 

Total $0.30 $0.95 $0.92 $0.91 $0.84 $0.84 $0.71 $0.71 $0.71 $0.71 

Nonhandheld 

1 125 Variable $0.34 $0.34 $0.53 $0.53 $12.71 $12.58 $12.58 $12.58 $12.58 $11.34 

Fixed $0.51 $0.50 $1.90 $1.87 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 

Total $0.85 $0.84 $2.44 $2.40 $12.71 $12.58 $12.58 $12.58 $12.58 $11.34 

1 250 Variable $0.34 $0.34 $0.53 $0.53 $15.11 $14.98 $14.98 $14.98 $14.98 $13.66 

Fixed $3.24 $3.19 $8.36 $8.21 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 

Total $3.58 $3.52 $8.89 $8.75 $15.11 $14.98 $14.98 $14.98 $14.98 $13.66 

1 500 Variable $0.34 $0.34 $0.53 $0.53 $14.65 $14.52 $14.52 $14.52 $14.52 $13.21 

Fixed $4.44 $4.36 $12.09 $11.88 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 

Total $4.77 $4.70 $12.63 $12.41 $14.65 $14.52 $14.52 $14.52 $14.52 $13.21 

1 125/250/500 Variable $0.34 $0.34 $0.53 $0.53 $2.94 $2.81 $2.81 $2.81 $2.81 $2.33 

snow- Fixed $0.13 $0.13 $0.18 $0.18 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 

blower Total $0.47 $0.47 $0.71 $0.71 $2.94 $2.81 $2.81 $2.81 $2.81 $2.33 

2 250 Variable $0.00 $0.00 $0.00 $16.80 $16.80 $16.80 $16.80 $14.24 $14.24 $14.24 

Fixed $1.40 $3.55 $3.49 $0.12 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 

Total $1.40 $3.55 $3.49 $16.92 $16.80 $16.80 $16.80 $14.24 $14.24 $14.24 

2 500 Variable $0.00 $0.00 $0.00 $12.05 $12.05 $12.05 $12.05 $9.98 $9.98 $9.98 

Fixed $5.82 $13.16 $12.93 $0.83 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 

Total $5.82 $13.16 $12.93 $12.88 $12.05 $12.05 $12.05 $9.98 $9.98 $9.98 

2 1,000 Variable $0.00 $0.00 $0.00 $30.56 $30.56 $30.56 $30.56 $25.71 $25.71 $25.71 

Fixed $11.41 $31.34 $30.80 $0.59 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 

Total $11.41 $31.34 $30.80 $31.15 $30.56 $30.56 $30.56 $25.71 $25.71 $25.71 

9-48 
Economic Impact Analysis 

Table 9.3-16: Compliance Costs per Equipment - Small SI (2005$) 

Class 

Useful 

life 

Cost 

type 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017+ 

Handheld 

All engines Variable 

Fixed 

Total 

No equipment costs for HH, all costs are allocated to engine manufacturers 

Nonhandheld 

1 125-500 Variable 

Fixed 

Total 

No equipment costs for NHH Class I, all costs are allocated to engine manufacturers 

2 250 

ag/const 

Variable 

Fixed 

Total 

 $1.29 

 $0.26 

$1.55 

$1.29 

$4.47 

$5.76 

$1.29 

$4.13 

$5.42 

$9.60 

$0.00 

$9.60 

$9.60 

$0.00 

$9.60 

$9.47 

$0.00 

$9.47 

$9.47 

$0.00 

$9.47 

$9.47 

$0.00 

$9.47 

$8.16 

$0.00 

$8.16 

$8.16 

$0.00 

$8.16 

2 250 

tractor res 

Variable 

Fixed 

Total 

 $1.21 

 $0.26 

$1.47 

$1.21 

$4.84 

$6.05 

$1.21 

$4.50 

$5.71 

$7.07 

$0.00 

$7.07 

$7.07 

$0.00 

$7.07 

$6.94 

$0.00 

$6.94 

$6.94 

$0.00 

$6.94 

$6.94 

$0.00 

$6.94 

$6.08 

$0.00 

$6.08 

$6.08 

$0.00 

$6.08 

2 250 

L&G other 

Variable 

Fixed 

Total 

 $0.60 

 $0.26 

$0.86 

$0.60 

$3.68 

$4.28 

$0.60 

$3.36 

$3.96 

$5.44 

$0.00 

$5.44 

$5.44 

$0.00 

$5.44 

$5.32 

$0.00 

$5.32 

$5.32 

$0.00 

$5.32 

$5.32 

$0.00 

$5.32 

$4.63 

$0.00 

$4.63 

$4.63 

$0.00 

$4.63 

2 250 

pumps 

Variable 

Fixed 

Total 

 $0.96 

 $0.26 

$1.22 

$0.96 

$4.32 

$5.28 

$0.96 

$3.99 

$4.95 

$8.53 

$0.00 

$8.53 

$8.53 

$0.00 

$8.53 

$8.41 

$0.00 

$8.41 

$8.41 

$0.00 

$8.41 

$8.41 

$0.00 

$8.41 

$7.23 

$0.00 

$7.23 

$7.23 

$0.00 

$7.23 

2 250 

utility 

Variable 

Fixed 

Total 

 $1.00 

$0.26 

$1.26 

$1.00 

$4.14 

$5.14 

$1.00 

$3.81 

$4.81 

$7.96 

$0.00 

$7.96 

$7.96 

$0.00 

$7.96 

$7.83 

$0.00 

$7.83 

$7.83 

$0.00 

$7.83 

$7.83 

$0.00 

$7.83 

$6.76 

$0.00 

$6.76 

$6.76 

$0.00 

$6.76 

2 250 

weld/press 

Variable 

Fixed 

Total 

 $1.34 

 $0.26 

$1.60 

$1.34 

$4.58 

$5.93 

$1.34 

$4.25 

$5.59 

$10.09 

$0.00 

$10.09 

$10.09 

$0.00 

$10.09 

$9.96 

$0.00 

$9.96 

$9.96 

$0.00 

$9.96 

$9.96 

$0.00 

$9.96 

$8.58 

$0.00 

$8.58 

$8.58 

$0.00 

$8.58 

2 500 

ag/const 

Variable 

Fixed 

Total 

 $1.29 

 $0.26 

$1.55 

$1.29 

$22.36 

$23.65 

$1.29 

$21.72 

$23.01 

$9.60 

$0.00 

$9.60 

$9.60 

$0.00 

$9.60 

$9.47 

$0.00 

$9.47 

$9.47 

$0.00 

$9.47 

$9.47 

$0.00 

$9.47 

$8.16 

$0.00 

$8.16 

$8.16 

$0.00 

$8.16 

2 500 

tractor com 

Variable 

Fixed 

Total 

 $1.21 

 $0.26 

$1.47 

$1.21 

$22.73 

$23.94 

$1.21 

$22.08 

$23.29 

$7.07 

$0.00 

$7.07 

$7.07 

$0.00 

$7.07 

$6.94 

$0.00 

$6.94 

$6.94 

$0.00 

$6.94 

$6.94 

$0.00 

$6.94 

$6.08 

$0.00 

$6.08 

$6.08 

$0.00 

$6.08 

2 500 

L&G other 

Variable 

Fixed 

Total 

 $0.60 

 $0.26 

$0.86 

$0.60 

$21.58 

$22.18 

$0.60 

$20.95 

$21.55 

$5.44 

$0.00 

$5.44 

$5.44 

$0.00 

$5.44 

$5.32 

$0.00 

$5.32 

$5.32 

$0.00 

$5.32 

$5.32 

$0.00 

$5.32 

$4.63 

$0.00 

$4.63 

$4.63 

$0.00 

$4.63 

2 500 

pumps 

Variable 

Fixed 

Total 

 $0.96 

 $0.26 

$1.22 

$0.96 

$22.21 

$23.17 

$0.96 

$21.57 

$22.53 

$8.53 

$0.00 

$8.53 

$8.53 

$0.00 

$8.53 

$8.41 

$0.00 

$8.41 

$8.41 

$0.00 

$8.41 

$8.41 

$0.00 

$8.41 

$7.23 

$0.00 

$7.23 

$7.23 

$0.00 

$7.23 

2 500 

utility 

Variable 

Fixed 

Total 

 $1.00 

$0.26 

$1.26 

$1.00 

$22.04 

$23.04 

$1.00 

$21.39 

$22.40 

$7.96 

$0.00 

$7.96 

$7.96 

$0.00 

$7.96 

$7.83 

$0.00 

$7.83 

$7.83 

$0.00 

$7.83 

$7.83 

$0.00 

$7.83 

$6.76 

$0.00 

$6.76 

$6.76 

$0.00 

$6.76 

2 500 

weld/press 

Variable 

Fixed 

Total 

 $1.34 

 $0.26 

$1.60 

$1.34 

$22.48 

$23.82 

$1.34 

$21.83 

$23.17 

$10.09 

$0.00 

$10.09 

$10.09 

$0.00 

$10.09 

$9.96 

$0.00 

$9.96 

$9.96 

$0.00 

$9.96 

$9.96 

$0.00 

$9.96 

$8.58 

$0.00 

$8.58 

$8.58 

$0.00 

$8.58 

2 1,000 

ag/const 

Variable 

Fixed 

Total 

 $1.29 

 $0.26 

$1.55 

$1.29 

$16.22 

$17.51 

$1.29 

$15.68 

$16.97 

$9.60 

$0.00 

$9.60 

$9.60 

$0.00 

$9.60 

$9.47 

$0.00 

$9.47 

$9.47 

$0.00 

$9.47 

$9.47 

$0.00 

$9.47 

$8.16 

$0.00 

$8.16 

$8.16 

$0.00 

$8.16 

9-49 
Final Regulatory Impact Analysis 

Class 

Useful 

life 

Cost 

type 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017+ 

2 1,000 

tractor com 

Variable 

Fixed 

Total 

 $1.21 

 $0.26 

$1.47 

$1.21 

$16.59 

$17.80 

$1.21 

$16.04 

$17.25 

$7.07 

$0.00 

$7.07 

$7.07 

$0.00 

$7.07 

$6.94 

$0.00 

$6.94 

$6.94 

$0.00 

$6.94 

$6.94 

$0.00 

$6.94 

$6.08 

$0.00 

$6.08 

$6.08 

$0.00 

$6.08 

2 1,000 

L&G other 

Variable 

Fixed 

Total 

 $0.60 

 $0.26 

$0.86 

$0.60 

$15.44 

$16.04 

$0.60 

$14.91 

$15.51 

$5.44 

$0.00 

$5.44 

$5.44 

$0.00 

$5.44 

$5.32 

$0.00 

$5.32 

$5.32 

$0.00 

$5.32 

$5.32 

$0.00 

$5.32 

$4.63 

$0.00 

$4.63 

$4.63 

$0.00 

$4.63 

2 1,000 

pumps 

Variable 

Fixed 

Total 

 $0.96 

 $0.26 

$1.22 

$0.96 

$16.07 

$17.03 

$0.96 

$15.53 

$16.49 

$8.53 

$0.00 

$8.53 

$8.53 

$0.00 

$8.53 

$8.41 

$0.00 

$8.41 

$8.41 

$0.00 

$8.41 

$8.41 

$0.00 

$8.41 

$7.23 

$0.00 

$7.23 

$7.23 

$0.00 

$7.23 

2 1,000 

utility 

Variable 

Fixed 

Total 

 $1.00 

$0.26 

$1.26 

$1.00 

$15.89 

$16.89 

$1.00 

$15.36 

$16.36 

$7.96 

$0.00 

$7.96 

$7.96 

$0.00 

$7.96 

$7.83 

$0.00 

$7.83 

$7.83 

$0.00 

$7.83 

$7.83 

$0.00 

$7.83 

$6.76 

$0.00 

$6.76 

$6.76 

$0.00 

$6.76 

2 1,000 

weld/press 

Variable 

Fixed 

Total 

 $1.34 

 $0.26 

$1.60 

$1.34 

$16.33 

$17.68 

$1.34 

$15.79 

$17.14 

$10.09 

$0.00 

$10.09 

$10.09 

$0.00 

$10.09 

$9.96 

$0.00 

$9.96 

$9.96 

$0.00 

$9.96 

$9.96 

$0.00 

$9.96 

$8.58 

$0.00 

$8.58 

$8.58 

$0.00 

$8.58 

2 250/500/1000 

snowblower 

Variable 

Fixed 

Total

 $0.51 

 $0.26 

 $0.77 

$0.51 

$0.47 

$0.97 

$0.51 

$0.20 

$0.71 

$3.98 

$0.00 

$3.98 

$3.98 

$0.00 

$3.98 

$3.85 

$0.00 

$3.85 

$3.85 

$0.00 

$3.85 

$3.85 

$0.00 

$3.85 

$3.27 

$0.00 

$3.27 

$3.27 

$0.00 

$3.27 

9.3.3.2 Marine SI Market Compliance Costs 

The Marine SI engine and equipment compliance costs are summarized in Tables 9.3-17 

and 9.3-18. Cost estimates are given for each of the 15 engine/equipment combinations, plus cost 

estimates for loose OB engines. The engine costs begin in 2008 and increase in 2010 when the 

variable costs for exhaust emission standards begin to be incurred. In addition, we apply a one 

time learning curve correction to the variable cost in the sixth year. The engine compliance costs 

remain the same for 2015 and later years. The equipment costs are more complicated due to the 

phase in of the different standards. They begin in 2009, increase in 2011 or 2012 , and then 

decrease in 2015. Equipment compliance costs remain the same for 2015 and later years. 

9-50 
Table 9.3-17: Compliance Costs per Engine - Marine SI (2005$) 

Application 

Category 

HP 

Category 

Cost 

Type 

2008 2009 2010 2011 2012 2013 2014 2015 2016 2

PWC 50-100 Variable $0 $0 $870 $870 $870 $870 $870 $696 $696 $

Fixed $73 $73 $0 $0 $0 $0 $0 $0 $0 

Total $73 $73 $870 $870 $870 $870 $870 $696 $696 $

PWC 100-175 Variable $0 $0 $85 $85 $85 $85 $85 $68 $68 

Fixed $34 $34 $0 $0 $0 $0 $0 $0 $0 

Total $34 $34 $85 $85 $85 $85 $85 $68 $68 

PWC 175-300 Variable $0 $0 $1,290 $1,290 $1,290 $1,290 $1,290 $1,032 $1,032 $1

Fixed $113 $113 $0 $0 $0 $0 $0 $0 $0 

Total $113 $113 $1,290 $1,290 $1,290 $1,290 $1,290 $1,032 $1,032 $1

SD/I 100-175 Variable $0 $0 $465 $465 $465 $465 $465 $372 $372 $

recreational Fixed $45 $45 $0 $0 $0 $0 $0 $0 $0 

Total $45 $45 $465 $465 $465 $465 $465 $372 $372 $

SD/I 175-300 Variable $0 $0 $320 $320 $320 $320 $320 $256 $256 $

recreational Fixed $50 $50 $0 $0 $0 $0 $0 $0 $0 

Total $50 $50 $320 $320 $320 $320 $320 $256 $256 $

SD/I 300+ Variable $0 $0 $297 $297 $297 $297 $297 $238 $238 $

recreational Fixed $57 $57 $0 $0 $0 $0 $0 $0 $0 

Total $57 $57 $297 $297 $297 $297 $297 $238 $238 $

SD/I 175-300 Variable $0 $0 $320 $320 $320 $320 $320 $256 $256 $

luxury Fixed $50 $50 $0 $0 $0 $0 $0 $0 $0 

Total $50 $50 $320 $320 $320 $320 $320 $256 $256 $

SD/I 300+ Variable $0 $0 $297 $297 $297 $297 $297 $238 $238 $

luxury Fixed $57 $57 $0 $0 $0 $0 $0 $0 $0 

Total $57 $57 $297 $297 $297 $297 $297 $238 $238 $
Application 

Category 

HP 

Category 

Cost 

Type 

2008 2009 2010 2011 2012 2013 2014 2015 2016 2

OB <25 Variable $0 $0 $69 $69 $69 $69 $69 $55 $55 

recreational Fixed $12 $12 $0 $0 $0 $0 $0 $0 $0 

Total $12 $12 $69 $69 $69 $69 $69 $55 $55 

OB 25-50 Variable $0 $0 $216 $216 $216 $216 $216 $173 $173 $

recreational Fixed $14 $14 $0 $0 $0 $0 $0 $0 $0 

Total $14 $14 $216 $216 $216 $216 $216 $173 $173 $

OB 50-100 Variable $0 $0 $203 $203 $203 $203 $203 $162 $162 $

recreational Fixed $20 $20 $0 $0 $0 $0 $0 $0 $0 

Total $20 $20 $203 $203 $203 $203 $203 $162 $162 $

OB 100-175 Variable $0 $0 $338 $338 $338 $338 $338 $270 $270 $

recreational Fixed $37 $37 $0 $0 $0 $0 $0 $0 $0 

Total $37 $37 $338 $338 $338 $338 $338 $270 $270 $

OB 175-300 Variable $0 $0 $690 $690 $690 $690 $690 $552 $552 $

recreational Fixed $67 $67 $0 $0 $0 $0 $0 $0 $0 

Total $67 $67 $690 $690 $690 $690 $690 $552 $552 $

OB 100-175 Variable $0 $0 $338 $338 $338 $338 $338 $270 $270 $

luxury Fixed $37 $37 $0 $0 $0 $0 $0 $0 $0 

Total $37 $37 $338 $338 $338 $338 $338 $270 $270 $

OB 175-300 Variable $0 $0 $690 $690 $690 $690 $690 $552 $552 $

luxury Fixed $67 $67 $0 $0 $0 $0 $0 $0 $0 

Total $67 $67 $690 $690 $690 $690 $690 $552 $552 $

OB <25 Variable $0 $0 $69 $69 $69 $69 $69 $55 $55 

loose engines Fixed $12 $12 $0 $0 $0 $0 $0 $0 $0 

Total $12 $12 $69 $69 $69 $69 $69 $55 $55 
Table 9.3-18: Compliance Costs per Equipment- Marine SI (2005$) 

Application 

Category 

HP 

Category 

Cost 

Type 

2008 2009 2010 2011 2012 2013 2014 2015 2016 2

PWC 50-100 Variable $0.0 $1.6 $1.6 $9.7 $9.7 $9.7 $9.7 $9.7 $9.7 $9

Fixed $0.9 $15.5 $14.7 $0.0 $0.0 $0.0 $0.0 $0.0 $0.0 $0

Total $0.9 $17.1 $16.2 $9.7 $9.7 $9.7 $9.7 $9.7 $9.7 $9

PWC 100-175 Variable $0.0 $1.9 $1.9 $11.2 $11.2 $11.2 $11.2 $11.2 $11.2 $1

Fixed $0.9 $17.0 $16.1 $0.0 $0.0 $0.0 $0.0 $0.0 $0.0 $0

Total $0.9 $18.9 $18.1 $11.2 $11.2 $11.2 $11.2 $11.2 $11.2 $1

PWC 175-300 Variable $0.0 $1.9 $1.9 $11.2 $11.2 $11.2 $11.2 $11.2 $11.2 $1

Fixed $0.9 $17.0 $16.1 $0.0 $0.0 $0.0 $0.0 $0.0 $0.0 $0

Total $0.9 $18.9 $18.1 $11.2 $11.2 $11.2 $11.2 $11.2 $11.2 $1

SD/I 100-175 Variable $0.0 $3.8 $3.8 $31.4 $67.2 $67.2 $67.2 $67.2 $61.7 $5

recreational Fixed $1.5 $1.5 $0.3 $0.3 $0.0 $0.0 $0.0 $0.0 $0.0 $0

Total $1.5 $5.3 $4.1 $31.7 $67.2 $67.2 $67.2 $67.2 $61.7 $5

SD/I 175-300 Variable $0.0 $4.6 $4.6 $43.7 $94.4 $94.4 $94.4 $94.4 $86.6 $8

recreational Fixed $1.5 $1.5 $0.3 $0.3 $0.0 $0.0 $0.0 $0.0 $0.0 $0

Total $1.5 $6.2 $4.9 $44.0 $94.4 $94.4 $94.4 $94.4 $86.6 $8

SD/I 300+ Variable $0.0 $5.2 $5.2 $71.6 $157.6 $157.6 $157.6 $157.6 $144.3 $13

recreational Fixed $1.5 $1.5 $0.3 $0.3 $0.0 $0.0 $0.0 $0.0 $0.0 $0

Total $1.5 $6.8 $5.5 $71.9 $157.6 $157.6 $157.6 $157.6 $144.3 $13

SD/I 175-300 Variable $0.0 $5.7 $5.7 $53.6 $115.7 $115.7 $115.7 $115.7 $106.1 $9

luxury Fixed $1.9 $1.9 $0.4 $0.4 $0.0 $0.0 $0.0 $0.0 $0.0 $0

Total $1.9 $7.5 $6.0 $54.0 $115.7 $115.7 $115.7 $115.7 $106.1 $9
Application 

Category 

HP 

Category 

Cost 

Type 

2008 2009 2010 2011 2012 2013 2014 2015 2016 2

SD/I 300+ Variable $0.0 $7.8 $7.8 $107.2 $236.1 $236.1 $236.1 $236.1 $216.2 $2

luxury Fixed $2.3 $2.3 $0.4 $0.4 $0.0 $0.0 $0.0 $0.0 $0.0 $

Total $2.3 $10.1 $8.3 $107.7 $236.1 $236.1 $236.1 $236.1 $216.2 $2

OB <25 Variable $0.0 $3.9 $5.5 $10.8 $10.8 $10.8 $10.8 $10.4 $10.4 $

recreational Fixed $0.7 $10.8 $10.1 $0.0 $0.0 $0.0 $0.0 $0.0 $0.0 $

Total $0.7 $14.6 $15.5 $10.8 $10.8 $10.8 $10.8 $10.4 $10.4 $

OB 25-50 Variable $0.0 $5.5 $5.5 $21.6 $38.6 $38.6 $38.6 $38.6 $35.4 $

recreational Fixed $1.6 $1.6 $0.4 $0.4 $0.0 $0.0 $0.0 $0.0 $0.0 $

Total $1.6 $7.2 $5.9 $22.0 $38.6 $38.6 $38.6 $38.6 $35.4 $

OB 50-100 Variable $0.0 $8.3 $8.3 $34.6 $61.6 $61.6 $61.6 $61.6 $56.4 $

recreational Fixed $1.7 $1.7 $0.4 $0.4 $0.0 $0.0 $0.0 $0.0 $0.0 $

Total $1.7 $10.0 $8.7 $34.9 $61.6 $61.6 $61.6 $61.6 $56.4 $

OB 100-175 Variable $0.0 $10.0 $10.0 $52.4 $95.4 $95.4 $95.4 $95.4 $86.9 $

recreational Fixed $1.7 $1.7 $0.4 $0.4 $0.0 $0.0 $0.0 $0.0 $0.0 $

Total $1.7 $11.7 $10.4 $52.8 $95.4 $95.4 $95.4 $95.4 $86.9 $

OB 175-300 Variable $0.0 $11.7 $11.7 $74.9 $138.3 $138.3 $138.3 $138.3 $125.6 $1

recreational Fixed $1.7 $1.7 $0.4 $0.4 $0.0 $0.0 $0.0 $0.0 $0.0 $

Total $1.7 $13.3 $12.0 $75.2 $138.3 $138.3 $138.3 $138.3 $125.6 $1

OB 100-175 Variable $0.0 $19.4 $19.4 $101.4 $184.5 $184.5 $184.5 $184.5 $168.1 $1

luxury Fixed $3.2 $3.2 $0.7 $0.7 $0.0 $0.0 $0.0 $0.0 $0.0 $

Total $3.2 $22.6 $20.1 $102.1 $184.5 $184.5 $184.5 $184.5 $168.1 $1

OB 175-300 Variable $0.0 $22.6 $22.6 $144.8 $267.4 $267.4 $267.4 $267.4 $243.0 $2

luxury Fixed $3.2 $3.2 $0.7 $0.7 $0.0 $0.0 $0.0 $0.0 $0.0 $

Total $3.2 $25.8 $23.3 $145.5 $267.4 $267.4 $267.4 $267.4 $243.0 $2

OB <25 Variable $0.0 $3.1 $4.4 $8.6 $8.6 $8.6 $8.6 $8.3 $8.3 $

loose Fixed $0.6 $8.6 $8.1 $0.0 $0.0 $0.0 $0.0 $0.0 $0.0 $

engine Total $0.6 $11.7 $12.4 $8.6 $8.6 $8.6 $8.6 $8.3 $8.3 $
Economic Impact Analysis 

9.3.4 Growth Rates 

The growth rates used in this analysis for future Small SI and Marine SI engines and 

equipment sales are from EPA's Nonroad 2005 model and are the same the same as those use for 

the cost analysis (EPA 2004b). Because the growth rates are linear, the annual growth rate 

decreases over time. For Small SI, the growth rate is approximately 2 percent per year beginning 

in 2008 to decreases to approximately 1.5 percent for 2020 and later years. The growth rate for 

Marine SI is about 0.8 percent per year in the early years and 0.6 percent in later years. 

9.3.5 Fuel Savings 

As noted in Section 9.2.4.2, there are fuel savings attributable to the final emission control 

program, reflecting the reduction in evaporative emissions and the use of more fuel-efficient 

engine technology to meet the final engine exhaust standards. As explained in that section, these 

savings are included in the economic welfare analysis as a separate line item. Consumers of Small 

SI and Marine SI engines and equipment will realize an increase in their welfare equivalent to the 

amount of gallons of gasoline saved multiplied by the retail price of the gasoline (post-tax price). 

In the engineering cost analysis the fuel savings are estimated in this manner. However, in the 

context of the social welfare analysis, some of this increase in consumer welfare is offset by lost 

tax revenues to local, state, and federal governments. These welfare losses must be accounted for 

as well. Therefore, the net change in social welfare is the difference between the increase in 

consumer welfare and the lost tax revenues. This is equivalent to using the pre-tax price of 

gasoline to estimate the fuel savings for the social welfare analysis. 

The amount of gallons of gasoline fuel saved is composed of two parts. First, upgrades in 

engine technology is expected to reduce fuel consumption rates. These fuel consumption 

reductions were calculated using the NONROAD2005 model. In addition, fuel savings due to 

evaporative emission control is estimated based on the VOC reductions attributable to these 

controls. Tons of annual VOC reductions are translated to gallons of gasoline saved using a fuel 

density of 6 lbs per gallon (for lighter hydrocarbons which evaporate first). 

Because the gallons of gasoline saved are based on estimated national reductions and were 

not estimated by PADD, we estimated a national average retail gasoline price (RTI, Memorandum 

on Calculation Motor Gasoline Prices in Small SI rule EIA, 2006). This estimate is the sum of the 

weighted average of pre-tax gasoline prices by PADD and the weighted average gasoline tax by 

PADD, using data from the 2005 Petroleum Marketing Annual (DoE 2005, Table 31). The results 

of this analysis are shown in Tables 13.3-19 and 13.3-20. 

9-55 
Table 9.3-19: Estimated National Average Fuel Prices (2005$) 

PADD Weight Pre-tax 

Price/Gallon 

Average State 

Taxes 

Federal Tax Post-Tax 

Price/Gallon 

PADD 1 0.40 $1.819 $0.207 $0.184 $2.210 

PADD 2 0.31 $1.792 $0.209 $0.184 $2.185 

PADD 3 0.18 $1.787 $0.194 $0.184 $2.165 

PADD 4 0.04 $1.848 $0.225 $0.184 $2.257 

PADD 5 

(excluding CA) 

0.07 $1.938 $0.198 $0.184 $2.320 

Total $1.814 $2.204 

Source: 2005 Petroleum Marketing Annual (Table 31). U.S. Department of Energy, Energy Information 

Administration (DoE 2005). Memorandum on Calculation Motor Gasoline Prices in Small SI Rule EIA, RTI, 2006. 

From 2008 until 2020 the estimated consumer savings associated with reduced gasoline 

consumption from the small SI and marine SI programs gas can controls increases sharply, from 

$3.2 million to $201 million. After 2020 the savings continue to accrue, but at a reduced rate as 

the engines and equipment population turns over and fuel savings are due to the continuing 

benefits of using compliant engines and equipment. Similarly, the tax revenue losses are expected 

to be increased from $0.7 million in 2008 to $43 million in 2020. 
Economic Impact Analysis 

Table 9.3-20: Estimated Fuel Savings and Tax Revenue Impacts (2005$) 

Tax 

Consumer Revenue Net Fuel 

Small SI Marine SI Fuel Savings Impacts Savings 

Year Gallons Gallons Total Gallons (Million$) (Million$) (Million$) 

2008 1,748,394 0 1,748,394 $3.9 $0.7 $3.2 

2009 4,060,953 398,339 4,459,291 $9.8 $1.7 $8.1 

2010 6,304,081 4,488,257 10,792,339 $23.8 $4.2 $19.6 

2011 14,982,484 9,200,101 24,182,584 $53.3 $9.4 $43.9 

2012 24,473,425 14,543,630 39,017,055 $86.0 $15.2 $70.8 

2013 32,954,248 19,806,738 52,760,987 $116.3 $20.6 $95.7 

2014 38,823,924 25,044,187 63,868,112 $140.8 $24.9 $115.9 

2015 43,779,918 30,265,803 74,045,720 $163.2 $28.9 $134.3 

2016 47,746,869 35,426,120 83,172,989 $183.3 $32.4 $150.9 

2017 50,580,035 40,529,842 91,109,877 $200.8 $35.5 $165.3 

2018 52,702,739 45,571,856 98,274,595 $216.6 $38.3 $178.3 

2019 54,429,770 50,527,419 104,957,189 $231.3 $40.9 $190.4 

2020 55,917,371 55,085,140 111,002,511 $244.6 $43.3 $201.4 

2021 57,171,954 59,222,320 116,394,274 $256.5 $45.4 $211.1 

2022 58,309,088 63,220,853 121,529,941 $267.9 $47.4 $220.5 

2023 59,361,292 67,056,116 126,417,408 $278.6 $49.3 $229.3 

2024 60,376,870 70,326,971 130,703,841 $288.1 $51.0 $237.1 

2025 61,369,887 73,270,886 134,640,773 $296.7 $52.5 $244.2 

2026 62,353,284 75,906,088 138,259,372 $304.7 $53.9 $250.8 

2027 63,326,668 78,313,723 141,640,391 $312.2 $55.2 $256.9 

2028 64,292,904 80,527,973 144,820,877 $319.2 $56.5 $262.7 

2029 65,253,036 82,543,743 147,796,779 $325.7 $57.6 $268.1 

2030 66,207,356 84,310,121 150,517,478 $331.7 $58.7 $273.0 

2031 67,157,496 85,894,203 153,051,700 $337.3 $59.7 $277.6 

2032 68,105,401 87,275,207 155,380,608 $342.5 $60.6 $281.9 

2033 69,050,694 88,524,271 157,574,965 $347.3 $61.5 $285.8 

2034 69,993,828 89,672,904 159,666,732 $351.9 $62.3 $289.6 

2035 70,935,570 90,731,710 161,667,280 $356.3 $63.1 $293.3 

2036 71,874,840 91,713,009 163,587,849 $360.5 $63.8 $296.7 

2037 72,811,766 92,624,481 165,436,247 $364.6 $64.5 $300.1 

9-57 
Final Regulatory Impact Analysis 

9.3.6 Supply and Demand Elasticity Estimates 

The estimated market impacts and economic welfare costs of this emission control program 

are a function of the ways in which producers and consumers of the Small SI and Marine SI 

engines and equipment affected by the standards change their behavior in response to the costs 

incurred in complying with the standards. These behavioral responses are incorporated in the EIM 

through the price elasticity of supply and demand (reflected in the slope of the supply and demand 

curves), which measure the price sensitivity of consumers and producers. 

Because we were unable to find published supply and demand elasticities for the Small SI 

and Marine SI markets, we estimated these parameters using the procedures described in Appendix 

9E. These methods are well-documented and are consistent with generally accepted econometric 

practice. It should be noted that these elasticities reflect intermediate-run behavioral changes. In 

the long run, supply and demand elasticities are expected to be more elastic. It should also be 

noted that the aggregate data (6 digits NAICS code or 4 digit SIC code industry data) we used to 

estimate elasticities include data on other markets as well as the Small SI or Marine SI markets. If 

we had been able to obtain market-specific data for Small SI or Marine SI only, the estimated price 

elasticities may have been different. 

The estimated supply and demand elasticities were based on best data we could find. For 

supply elasticities, we used the establishment-level or plant-level data from Census of 

Manufactures, conducted by the U. S. Census Bureau to estimate the production function for 

affected industries by this rule. The estimated coefficients of the production function were then 

used to calculate the supply elasticity for the industry. Establishments-level data were selected 

from 6 digit NAICS code industry for five Census years between 1972 and 1997. The supply 

elasticities estimated from plant-level data are more elastic than industry-level data, as we 

previously used for the EIA chapter in the NPRM 

For demand elasitcities, we used the industry-level data published by the National Bureau 

of Economic Research (NBER)-Center for Economic Studies (Bartlesman, Becker, and Gray, 

2000). In addition to NBER data, we also used the Current Industrial Reports (CIR) series from 

the U.S. Census Bureau to produce an annual summary of the production of motors and generators 

and a summary of production of several types of lawn and garden equipment; both of these reports 

include the number of units manufactured and the value of production (U.S. Census Bureau, 1998; 

2000). For walk-behind lawnmowers, we used several data series reported in a study by Air 

Improvement Resource, Inc., and National Economic Research Associates (AIR/NERA, 2003). 

The U.S. Census Bureau publishes historical data on household income and housing starts (U.S. 

Census Bureau, 2002; 2004), and we collected price, wage, and material cost indexes from the 

Bureau of Labor Statistics (BLS, 2004a,b,c,d,e). In cases where a price index was not available, 

we used the most recent implicit gross domestic product (GDP) price deflator reported by the U.S. 

Bureau of Economic Analysis (BEA, 2004).13 

13In estimating demand elasticity, all values are expressed in 1987$. 

9-58 
Economic Impact Analysis 

Tables 9.3-21 and 9.3-22 provide a summary of the demand and supply elasticities used to 

estimate the economic impact of the final rule. 

The estimated supply elasticities for all of the equipment and engine markets are elastic, 

ranging from 3.8 for all recreational marine except PWC, to 8.8 for generators, 5.2 for PWCs and, 

10 for all Small SI applications except generators, and 9.5 for engines. This means that quantities 

supplied are expected to be fairly sensitive to price changes (e.g., a 1 percent change in price 

yields a 8.8 percent change in quantity of generator producers are willing to supply ). 

On the demand side, the Marine SI equipment market estimated demand elasticity is 

elastic, at -2.0. This is consistent with the discretionary nature of purchases of recreational marine 

vessels (consumers can easily decide to spend their recreational budget on other alternatives). 

The estimated demand elasticity for handheld equipment is elastic, at -1.9. This suggests 

that consumers are more sensitive to price changes for handheld equipment than for other Small SI 

equipment. In other words, they are more likely to change their purchase decision for a small 

change in the price of a string trimmer, perhaps opting for trimmer shears or deciding to forego 

trimming altogether. 

The estimated demand elasticity for lawnmowers is very inelastic at -0.2. This suggests 

that consumers of this equipment are not very sensitive to price changes. Most of this equipment 

is sold to individual homeowners, who are often required by local authorities to keep their lawns 

trimmed. Household ownership of a gasoline lawnmower is often their least expensive option. 

Lawncare services are more expensive since the price for these services includes labor and other 

factors of production. Purchasing other equipment may also not be attractive, since electric and 

diesel mowers are generally more expensive and often less convenient. Finally, the option of 

using landscape alternatives (e.g., prairie, wildflower, or rock gardens) may not be attractive for 

home homeowners who may also use their yards for recreational purposes. For all these reasons, 

the price sensitivity of homeowners to lawnmower prices would be expected to be inelastic. 

All the other demand elasticities, for gensets, welders, compressors, and agriculture/ 

construction equipment, are about unit elastic, at -1.0 meaning a 1 percent change in price is 

expected to result in a 1 percent change in demand. 

The demand elasticities for the engine markets are internally derived as part of the process 

of running the model. This is an important feature of the EIM, which allows it to link the engine 

and equipment components of each model and simulate how compliance costs can be expected to 

ripple through the affected market. In actual markets, for example, the quantity of lawnmowers 

produced in a particular period depends on the price of engines (the Small SI engine market) and 

the demand for equipment by residential consumers. Similarly, the number of engines produced 

depends on the demand for engines (the lawnmower market), which depends on consumer demand 

for equipment. Changes in conditions in one of these markets will affect the others. By designing 

the model to derive the engine demand elasticities, the EIM simulates these connections between 

supply and demand among the product markets and replicates the economic interactions between 

producers and consumers. 

9-59 
Final Regulatory Impact Analysis 

As discussed in 9.2.3.2, the EIM model uses a derived demand approach for the engine 

market to incorporate the interaction between the equipment and engine markets. The demand 

curve for the engine market is solely derived from the equipment market. The derived demand is 

not affected by the product attributes that could shift the demand curve. In other words, as 

explained in 9.2.3.1, the demand curves for either the equipment or engine markets do not shift in 

response to any change in consumer preferences that may occur due to the compliance strategies of 

the producers in the analysis. We explore the impacts of relaxing this assumption in a sensitivity 

analysis (see 9.H.4). The engine and equipment changes needed to meet emission standards may 

affect the demand because of the potential changes to fuel consumption and engine performance. 

Section 9H.1 contains a sensitivity analysis that evaluates the effect of increased or decreased 

demand elasticities on the estimates of social cost of the rule. How this demand change affects the 

total social welfare of the rule is outside the scope of the analysis presented in Chapter 9 because 

the corresponding market failure (e.g., the health effects of air pollution) is not explicitly modeled; 

for example the economic impact of this regulation through reducing selected air pollutants is 

discussed separately in Chapter 8. 

Because the elasticity estimates are a key input to the model, a sensitivity analysis for 

supply and demand elasticity parameters was performed as part of this analysis in considering the 

uncertainty involved in the estimated elasticities. The results are presented in Appendix 9H. 

9-60 
Economic Impact Analysis 

Table 9.3-21: Summary of Market Supply Elasticities Used in EIM 

Market Estimate Source Method Input Data Source 

Engine Markets

 Small SI and Marine SI 

9.5 EPA econometric 

estimate 

Cobb-Douglas 

production function 

Census of 

Manufacture, US 

Census Bureau; five 

years between 1972 

and 1997; NAICS 

333618 

Marine Equipment Markets

 PWC 

All other vessel types 

5.2 

3.8 

EPA econometric 

estimate 

EPA econometric 

estimate 

Cobb-Douglas 

production function 

Cobb-Douglas 

production function 

Census of 

Manufacture, US 

Census Bureau; five 

years between 1972 

and 1997; NAICS 

336999 

Census of 

Manufacture, US 

Census Bureau; five 

years between 1972 

and 1997; NAICS 

336612 

Small SI Equipment Markets

 Gensets/welders 

 All other Small SI

 equipment (handheld

 and nonhandheld) 

8.8 

10.0 

EPA econometric 

estimate 

EPA econometric 

estimate 

Cobb-Douglas 

production function 

Cobb-Douglas 

production function 

Census of 

Manufacture, US 

Census Bureau; five 

years between 1972 

and 1997; NAICS 

335312 

Census of 

Manufacture, US 

Census Bureau; five 

years between 1972 

and 1997; NAICS 

333618 

9-61 
Final Regulatory Impact Analysis 

Table 9.3-22: Summary of Market Demand Elasticities Used in EIM 

Market Estimate Source Method Input Data Source 

Engine Markets

 Small SI and Marine SI 

Derived Demand 

Marine Equipment Markets

 All vessel types -2.0 EPA econometric 

estimate 

Simultaneous 

equation (3SLS) 

Bartlesman et al (2000); 

Manufacturing Industry 

Data from US Census 

Bureau: 1958-1996; SIC 

3732 

Small SI Equipment Markets 

HANDHELD: All -1.9 EPA econometric 

estimate 

NONHANDHELD

 Lawn mowers -0.2 EPA econometric 

estimate 

Other lawn and garden -0.9 EPA econometric 

estimate 

Gensets/welders - Class I -1.4 EPA econometric 

estimate 

Gensets/welders - Class II -1.1 EPA econometric 

estimate 

All other nonhandheld -1.0 EPA econometric 

estimate 

Simultaneous 

equation (2SLS) 

Simultaneous 

equation (3SLS) 

Simultaneous 

equation (2SLS) 

Simultaneous 

equation (2SLS) 

Simultaneous 

equation (2SLS) 

Simultaneous 

equation (2SLS) 

U.S. Census Bureau, 

Current Industrial 

Reports, MA333A 2000 

and selected previous 

years; 1980-1997 

AIR/NERA (2003); 

1973-2002 

Bureau, Current 

Industrial Reports, 

MA333A 2000 and 

selected previous years; 

1980-1997 

Bureau, Current 

Industrial Reports, 

MA333A 2000 and 

selected previous years; 

1980-1997 

Bureau, Current 

Industrial Reports, 

MA333A 2000 and 

selected previous years; 

1980-1997 

U.S. Census Bureau, 

Current Industrial 

Reports, MA333A 2000 

and selected previous 

years; 1980-1997 

9-62 
Economic Impact Analysis 

9.3.7 Economic Impact Model Structure 

9.3.7.1 Computing Baseline and With-Regulation Equilibrium Conditions 

The economic impact analysis is conducted using the data and the supply and demand 

framework described above. The price and quantity data, along with the supply and demand 

elasticities, are used to identify the market supply and demand curves. The regulatory costs are 

then used to shift the supply curve, and the resulting new equilibrium determines the market 

impacts and distribution of social impacts. 

Figure 9.3-1 illustrates the economic impact modeling structure. Point A represents the 

initial baseline equilibrium price and quantity (corresponding to the prices and quantities presented 

in section 9.3.2). The slope of the supply and demand curves passing through the baseline point A 

are determined by applying the appropriate supply and demand elasticities presented in section 

9.3.6. These slopes reflect the responsiveness of producers and consumers when prices change 

and determine how much of the compliance costs producers are able to pass along to consumers in 

the with-regulation equilibrium. 

The compliance costs associated with the regulation (presented in Section 9.3.3) enter the 

model expressed as per-unit costs and result in an upward shift in the supply curve from S0 to S1 in 

Figure 9.3-1. Note that the demand curve does not shift because consumer preferences and income 

are not affected by the regulation. 

With the addition of the compliance costs, if prices were not allowed to adjust demanders 

would still want to consume the quantity at point A, but suppliers would only be willing to supply 

the quantity at point B (i.e., demand exceeds supply at the baseline price, P). The model then 

solves for the new equilibrium price (P*) where the quantity demanded equals the quantity 

supplied. The movement from the baseline equilibrium point A to with-regulation equilibrium 

point C determines the market impacts (changes in price and quantity) as well as the distribution of 

social costs. Appendix 9D describes the set of supply and demand equations included in the 

model. Given the number of equations included in the model, the solution algorithm described 

below is used to identify the new with-regulation set of equilibrium prices and quantities (Point C). 

The analysis illustrated in Figure 9.3-1 is repeated for each year included in the period of 

analysis. For future years, a projected time series of prices and quantities are developed and used 

as the baseline (point A) from which market changes are evaluated. The engineering cost analysis 

provides quantities for future years using historical annual growth rates. In contrast, there is much 

more uncertainty surrounding future prices for these markets. As a result, we use a constant 2005 

observed prices for the relevant markets during the period of analysis. 

9.3.7.2 Solution Algorithm 

Supply responses and market adjustments can be conceptualized as an interactive process. 

Producers facing increased production costs due to compliance are willing to supply smaller 

quantities at the baseline price. This reduction in market supply leads to an increase in the market 

9-63 
Final Regulatory Impact Analysis 

price that all producers and consumers face, which leads to further responses by producers and 

consumers and thus new market prices, and so on. The new with-regulation equilibrium is the 

result of a series of iterations in which price is adjusted and producers and consumers respond, 

until a set of stable market prices arises where total market supply equals market demand. Market 

price adjustment takes place based on a price-revision rule, described below, that adjusts price 

upward (downward) by a given percentage in response to excess demand (excess supply). 

The EIM model uses a similar type of algorithm for determining with-regulation equilibria 

and the process can be summarized by six recursive steps: 

1.	 Impose the control costs on affected supply segments, thereby affecting their supply 

decisions. 

2.	 Recalculate the market supply in each market. Excess demand currently exists. 

3.	 Determine the new prices via a price revision rule. We use a rule similar to the 

factor price revision rule described by Kimbell and Harrison (1986). Pi

 is the market 

price at iteration I, qd is the quantity demanded, and qs is the quantity supplied. The 

parameter z influences the magnitude of the price revision and speed of 

convergence. The revision rule increases the price when excess demand exists, 

lowers the price when excess supply exists, and leaves the price unchanged when 

market demand equals market supply. The price adjustment is expressed as follows: 

Pi+1 = P1 • 

⎛

⎜

⎝ 

q

q

d 

s 

⎞

⎟

⎠ 

z 

(10.1) 

4.	 Recalculate market supply with new prices, 

5.	 Compute market demand in each market. 

6.	 Compare supply and demand in each market. If equilibrium conditions are not 

satisfied, go to Step 3, resulting in a new set of market prices. Repeat until 

equilibrium conditions are satisfied (i.e., the ratio of supply and demand is arbitrarily 

close to one). When the ratio is appropriately close to one, the market-clearing 

condition of supply equals demand is satisfied. 

9.3.7.3 Estimating Impacts 

Using the static partial equilibrium analysis, the EIM model loops through each year 

calculating new market equilibriums based on the projected baseline economic conditions and 

compliance cost estimates that shift the supply curves in the model. The model calculates price 

and quantity changes and uses these measures to estimate the social costs of the rule and partition 

the impact between producers and consumers. 

9.4 Methods for Describing Uncertainty 

9-64 
Economic Impact Analysis 

Every economic impact analysis examining the market and social welfare impacts of a 

regulatory program is limited to some extent by limitations in model capabilities, deficiencies in 

the economic literatures with respect to estimated values of key variables necessary to configure 

the model, and data gaps. In this EIA, there are three main potential sources of uncertainty: (1) 

uncertainty resulting from the way the EIM is designed, particularly from the use of a partial 

equilibrium model; (2) uncertainty resulting from the values for key model parameters, particularly 

the price elasticity of supply and demand; and (3) uncertainty resulting from the values for key 

model inputs, particularly baseline equilibrium price and quantities. Sources of uncertainty that 

have a bearing on the results of the EIA for the final program are listed and described in more 

detail in Table 9.4-1. 

The values used for the price elasticities of supply and demand are critical parameters in 

the EIM. The values of these parameters have an impact on both the estimated change in price and 

quantity produced expected as a result of compliance with the final standards and on how the 

burden of the social costs will be shared among producer and consumer groups. In selecting the 

values to use in the EIM it is important that they reflect the behavioral responses of the industries 

under analysis. 

The first source of values for elasticities of supply and demand is the published economic 

literature. These estimates are peer reviewed and generally constitute reasonable estimates for the 

industries in question. In this analysis, because we were unable to find published supply and 

demand elasticities for the Small SI and Marine SI markets, we estimated these parameters 

econometrically using the procedures described in Appendix 9E. 

The previous estimates of supply elasticities reflect a production function approach using 

data at the aggregate industry level. This method was chosen because of limitations with the 

available data; we were not able to obtain firm-level or plant-level production data for companies 

that operate in the affected sectors. However, the use of aggregate industry level data may not be 

appropriate or an accurate way to estimate the price elasticity of supply compared to firm-level or 

plant-level data. This is because, at the aggregate industry level, the size of the data sample is 

limited to the time series of the available years and because aggregate industry data may not reveal 

each individual firm or plant production function (heterogeneity). There may be significant 

differences among the firms that may be hidden in the aggregate data but that may affect the 

estimated elasticity. In addition, the use of time series aggregate industry data may introduce time 

trend effects that are difficult to isolate and control. 

To address these concerns, EPA has investigated estimates for the price elasticity of supply 

for the affected industries for which published estimates are not available, using alternative 

methods and data inputs. This research program used the cross-sectional data model at the 

firm-level or plant level from the U.S. Census Bureau to estimate these elasticities. We used the 

results of this research for the analysis. 

Table 9 .4-1 Primary Sources of Uncertainty in the Economic Impact Analysis 

9-65 
Final Regulatory Impact Analysis 

Source of Uncertainty Description Potential Impact 

UNCERTAINTIES ASSOCIATED WITH ECONOMIC IMPACT MODEL STRUCTURE 

Partial equilibrium 

model 

The EIM domain is limited to the economic sectors 

directly affected by the emission control program; 

impacts on secondary markets are not accounted for. 

However, such impacts are not expected to be large 

since directly affected products and services (small SI 

equipment and marine SI vessels) are mostly used by 

households and only a very small portion of these 

engines and equipment are used as production inputs 

to other industry (e.g., agriculture, manufacturing, 

construction). In addition, Small SI engines and 

equipment would not be a large share of total 

production costs for final goods and services in those 

commercial markets. 

Results understate social costs; 

magnitude of impact is 

uncertain. 

National level model The EIM considers only national-level impacts; 

regional impacts are not modeled. This is appropriate 

because Small SI engine and equipment or Marine SI 

engine and vessel markets are national markets. While 

there may be some regional differences these are likely 

to be small due to the competitive nature of the 

manufacture industry. 

Impacts uncertain 

Supply side 

assumptions 

On the supply side, industries are assumed to be 

mature and behave linearly within the range of 

analysis; no substitution between production inputs. 

This is appropriate because per unit compliance costs 

are not large enough to prompt a major change in 

product design or assembly. 

Impacts uncertain 

Demand side 

assumption 

On the demand side, end consumer’s preferences or 

consumption patterns are assumed to be constant and 

behave linearly within the range of analysis. This is 

appropriate because all other factors in the demand 

function will not be changed by the final rule. 

Impacts uncertain 

Constant price 

assumption 

Prices are assumed to be constant across the period of 

analysis. This is a reasonable assumption since it is 

not possible to predict changes in these prices over 

time (see Appendix G). 

Impacts uncertain 

Period of analysis Each period of analysis is assumed to be independent 

of previous period and producers are assumed to not 

engage in long-term planning to smooth the 

compliance costs over a longer period of time. 

Because the new exhaust standards will not go into 

effect for several years after the program is finalized, 

producers may in fact take the full program into 

account in production plans to minimize their costs. 

Estimated price changes may 

be too high for early periods, 

too low for later periods; 

magnitude of impact is 

uncertain 

9-66 
Economic Impact Analysis 

Market shock In the EIM, the market is shocked by either fixed or 

variable compliance costs. This is appropriate because 

producers in these industries may not engage in R&D 

on a continuous basis and thus the product changes 

that would be required to comply with the final 

standards would require manufacturers to devote new 

funds and resources to product redesign. 

Results may overstate 

distribution of social costs to 

some producers, understate 

market impacts; magnitude of 

impact is uncertain 

UNCERTAINTIES ASSOCIATED WITH PRICE ELASTICITY ESTIMATION 

Uncertainty resulting from the functional form used in 

the estimation, the data used (aggregate or firm-level), 

the time period involved, sample size. 

Impacts on distribution of 

social costs among 

stakeholders (e.g., higher 

supply elasticity would result 

in less social costs for 

manufacturers and more social 

costs for consumers) 

Impacts on market analysis 

(change in price, change in 

quantity produced) 

Magnitude of impact is 

uncertain 

UNCERTAINTIES ASSOCIATED WITH DATA INPUTS 

Submarket groupings Submarket data is assumed to be representative and 

capture the range of affected equipment. However, 

the product groupings in NAICS or SIC 4-digit 

categories may include other engines or equipment 

that may not have the same production or consumption 

characteristics; these groupings not behave the same 

way as the directly-affected industries. 

Impacts on social welfare and 

market analyses uncertain 

Baseline equilibrium 

prices 

Estimated baseline equilibrium prices are assumed to 

be representative and capture the range of affected 

equipment, and reflect actual transaction prices. 

However, the actual prices paid by consumers may be 

different. Also, the mix of products included in price 

analysis may not be representative of the population. 

Impacts on market analysis 

uncertain 

Baseline equilibrium 

quantities 

Estimated baseline equilibrium quantities and future 

quantities assumed to be representative; these are the 

same as the cost analysis. 

Impacts on market analysis 

uncertain 

To explore the effects of key sources of uncertainty, we performed a sensitivity analysis in 

which we examine the results of using alternative values for the price elasticity of supply and 

demand (using the upper and lower bound of at 95 percent confidence interval around the point 

estimate for each elasticity estimate), and alternative baseline equilibrium prices for lawnmowers 

9-67 
Final Regulatory Impact Analysis 

and tractors. The results of these analyses are contained in Appendix 9H. A summary of the 

results are presented in Table 9.4-2. 

Table 9.4-2. Results of Sensitivity Analysis 

Parameter Year Change in Value Impact 

Price Elasticity 

of Supply 

2014 More elastic 

(upper bound of 

95 percent 

confidence 

interval for each 

elasticity estimate) 

Negligible impact on expected price increase and quantity 

decrease (less than 0.2 additional increase in price increase 

compared to primary analysis; less than 0.2 additional 

increase in quantity decrease compared to primary analysis) 

More elasticity price elasticity of supply associated with 

increase in social cost burden for users of Small SI and 

Marine SI engines and equipment (shift of about 3.6 percent 

of burden of compliance costs from producers to consumers in 

Marine SI market; shift of about 2.5 percent of burden of 

compliance costs from producers to consumers in Small SI 

market) 

2014 Less Elastic 

(lower bound of 

95 percent 

confidence 

interval for each 

elasticity estimate) 

Negligible impact on expected price increase and quantity 

decrease (less than 0.2 additional increase in price increase 

compared to primary analysis; less than 0.2 percent additional 

increase in quantity decrease compared to primary analysis) 

Higher value associated with increase in social cost burden 

for producers of Small SI and Marine SI engines and 

equipment (shift of about 6 percent of burden of compliance 

costs from consumers to producers in Marine SI market; shift 

of about 6 percent of burden of compliance costs from 

consumers to producers in Small SI market) 

Price Elasticity 

of Demand 

2014 More Elastic 

(upper bound of 

95 percent 

confidence 

interval for each 

elasticity estimate) 

Negligible impact on expected price increase and quantity 

decrease (less than 0.5 percent additional increase in price 

increase compared to primary analysis; less than 1.5 percent 

additional increase in quantity decrease, compared to primary 

analysis) 

More elastic price elasticity of demand associated with 

increase in social cost burden for producers of Small SI and 

Marine SI engines and equipment (shift of about 11 percent of 

burden of compliance costs from consumers to producers in 

Marine SI market; shift of about 5 percent of burden of 

compliance costs from consumers to producers in Small SI 

market) 

9-68 
Economic Impact Analysis 

2014 Less Elastic 

(lower bound of 

95 percent 

confidence 

interval for each 

elasticity estimate) 

Negligible impact on expected price increase and quantity 

decrease (less than 1 percent additional increase in price 

increase compared to primary analysis; less than 3 additional 

increase in quantity decrease, compared to primary analysis) 

Less elastic price elasticity of demand associated with 

increase in social cost burden for users of Small SI and 

Marine SI engines and equipment (shift of about 22 percent of 

burden of compliance costs from producers to consumers in 

Marine SI market; shift of about 6 percent of burden of 

compliance costs from producers to consumers in Small SI 

market) 

Alternative 

Baseline 

Equilibrium 

Price -

Lawnmowers 

and Tractors 

2014 Lower baseline 

equilibrium price 

Larger percent increase in price and percent decrease in 

quantity, although absolute changes are smaller (less than 2 

percent additional price change for both sectors compared to 

primary analysis; about 0.3 percent additional quantity 

decrease for lawn mowers and about 1 percent additional 

quantity decrease for tractors compared to primary analysis) 

Social welfare impacts unchanged. 

9-69 
Final Regulatory Impact Analysis 

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0491. 

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Li, Chi. June 6, 2008. Memorandum to Docket EPA-HQ-OAR-2004-0008 Detailed Results 

From Economic Impact Model for the Final Rule. 

Li, Chi. May 19, 2008. Memorandum to Docket EPA-HQ-OAR-2004-0008 Supply Elasticity 

Estimation Report. 

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Economic Impact Analysis 

NBER-CES. National Bureau of Economic Research and U.S. Census Bureau, Center for 

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http://www.nber.org/nberces/nbprod96.htm 

Nicholson, W. 1998. Microeconomic Theory: Basic Principles and Extensions. Fort Worth: 

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EPA-HQ-OAR-2004-0008-0478. 

Raboy, David. 1987. “Results of an Economic Analysis of Proposed Excise Taxes on Boats.” 

Washington, DC. Docket Identification EPA-HQ-OAR-2004-0008-0462. 

RTI International (RTI). 2005. “Economic Impact Analysis (EIA) for Additional Tier of Emissions 

Standards for Nonroad Spark Ignition Engines and Equipment: Revised Draft Analysis Plan.” 

EPA Contract No. 68-D-99-024. Docket Identification EPA-HQ-OAR-2004-0008-0463. 

RTI International (RTI). 2006a. “Draft Industry Profile for Recreational Marine Industry.” 

Research Triangle Park, NC: RTI. EPA Contract No. 68-D-99-024. Docket Identification EPAHQ-OAR-2004-0008-0492 

RTI International (RTI). 2006b. “Draft Industry Profile for Small Nonroad Spark-Ignition Engines 

and Equipment.” Research Triangle Park, NC: RTI. EPA Contract No. 68-D-99-024. Docket 

Identification EPA-HQ-OAR-2004-0008-0469. 

RTI International (RTI). 2006c. “Memorandum on Calculation Motor Gasoline Prices in Small SI 

rule EIA”. EPA Contract No. 68-D-99-024. A copy of this document is available in EPA-HQOAR-2004-0008. Docket Identification EPA-HQ-OAR-2004-0008-0449. 

Samulski, M. August 2004. Memorandum to Docket EPA-HQ-OAR-2004-0008 Re: Draft Marine 

SI Sales and Prices Estimates. Docket Identification EPA-HQ-OAR-2004-0008-0448. 

U.S. Bureau of Economic Analysis. 2004. Table 1.1.9, Implicit Price Deflators for Gross Domestic 

Product. Last revised April 29, 2004. Docket Identification EPA-HQ-OAR-2004-0008-0473. 

U.S. Bureau of Labor Statistics. 2004a. Producer Price Index Industry Data: (1) Plastic Material 

and Resins Manufacturing. Series ID: PCU325211325211 (May 14, 2004), (2) Consumer 

Nonriding Lawn, Garden, and Snow Equipment. Series ID: PCU3331123331121 (May 20, 2004), 

9-71 
Final Regulatory Impact Analysis 

(3) Other Engine Equipment Manufacturing. Series ID: PCU3336183336181 (May 20, 2004), (4) 

Rotary, Push Type Gasoline Engine Powered. Series ID: WPU12660201 ( August 10, 2004). A 

copy of this document is available in the Docket. Docket Identification EPA-HQ-OAR-2004-0008-

0474. 

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Building: Series ID CEU3133661206; Farm Machinery and Equipment: Series ID EEU31352306). 

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Machinery and Lawn and Garden Equipment. MA333A (MA35A prior to 1998). Washington, DC: 

U.S. Government Printing Office. Docket Identification EPA-HQ-OAR-2004-0008-0476. 

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<http://www.census.gov/prod/2005pubs/mqc1-04.pdf>. Table 1a. 

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Research Triangle Park, NC: EPA. A copy of this document can be found at 

http://www.epa.gov/ttn/ecas/econdata/6807-305.pdf. 

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EPA-240-R-00-003, September 2000. 

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from Nonroad Diesel Engines. EPA-420-R-04-007. Research Triangle Park, NC: EPA. 

9-72 
Economic Impact Analysis 

Appendix 9A: Impacts on Small SI Markets 

This appendix provides the time series of impacts from 2008 through 2037 for the 

following Small SI engines and equipment markets; a complete set of results for all markets can be 

found in the docket for this rule (Li, 2008). Results are presented for equipment in the Class I 

UL125 and Class II UL250 categories because those are the categories with the highest sales. 

• Class I engines 

• Class II engines 

• Handheld equipment 

• Agriculture/construcion/general industrial, UL125 and UL250 

• Utility and recreational vehicles, UL125 and UL250 

• Lawn mowers, UL125 

• Tractors, UL250 

• Lawn and garden other, UL125 and UL250 

• Gensets/welders, UL125 and 250 

• Pumps/compressors, pressure washers, UL125 and UL250 

• Snowblowers, UL125 and UL250 

Table 9A-1 through Table 9A-17 provide the time series of impacts for each engine class 

market and each selected equipment market, respectively, includes the following: 

• average engine or equipment price 

• average engineering costs (variable and fixed) per engine or equipment 

• absolute change in the market price ($) 

• relative change in market price (%) 

• relative change in market quantity (%) 

• total engineering costs associated with each engine or equipment market 

• changes in producer surplus associated with each engine or equipment market 

All prices and costs are presented in 2005 dollars and real engine or equipment prices are 

assumed to be constant during the period of analysis. Net present values were estimated using 

social discount rates of 3 percent and 7 percent over the period of analysis. 

9-73 
Final Regulatory Impact Analysis 

Table 9A-1: Impact on Small SI Engine Market 

Class I (Average Price per Engine = $140)a,b 

Small SI Engine (Class I) 

Total Change in Engine 

Absolute Change in Engineering Manufacturers 

Engineering Change in Change in Quantity Costs Surplus 

Year Cost/Unit Price Price (%) (%) (million $) (million $) 

2008 $1 $1 0.8% –0.1% $11.4 –$0.1 

2009 $1 $1 0.8% –0.1% $11.5 –$0.2 

2010 $3 $3 2.3% –0.4% $32.3 –$0.6 

2011 $3 $3 2.2% –0.4% $32.4 –$0.5 

2012 $12 $12 8.9% –1.9% $131.3 –$2.8 

2013 $12 $12 8.8% –1.9% $132.2 –$2.7 

2014 $12 $12 8.8% –1.9% $134.4 –$2.8 

2015 $12 $12 8.8% –1.9% $136.6 –$2.8 

2016 $12 $12 8.8% –1.9% $138.8 –$2.9 

2017 $11 $11 7.9% –1.7% $127.1 –$2.6 

2018 $11 $11 7.9% –1.7% $129.1 –$2.6 

2019 $11 $11 7.9% –1.7% $131.1 –$2.7 

2020 $11 $11 7.9% –1.7% $133.1 –$2.7 

2021 $11 $11 7.9% –1.7% $135.1 –$2.8 

2022 $11 $11 7.9% –1.7% $137.1 –$2.8 

2023 $11 $11 7.9% –1.7% $139.1 –$2.8 

2024 $11 $11 7.9% –1.7% $141.1 –$2.9 

2025 $11 $11 7.9% –1.7% $143.1 –$2.9 

2026 $11 $11 7.9% –1.7% $145.1 –$3.0 

2027 $11 $11 7.9% –1.7% $147.1 –$3.0 

2028 $11 $11 7.9% –1.7% $149.1 –$3.0 

2029 $11 $11 7.9% –1.7% $151.2 –$3.1 

2030 $11 $11 7.9% –1.7% $153.2 –$3.1 

2031 $11 $11 7.9% –1.7% $155.2 –$3.2 

2032 $11 $11 7.9% –1.7% $157.2 –$3.2 

2033 $11 $11 7.9% –1.7% $159.2 –$3.2 

2034 $11 $11 7.9% –1.7% $161.3 –$3.3 

2035 $11 $11 7.9% –1.7% $163.3 –$3.3 

2036 $11 $11 7.9% –1.7% $165.3 –$3.4 

2037 $11 $11 7.9% –1.7% $167.3 –$3.4 

NPV (3%) $2,340.8 –$47.5 

NPV (7%) $1,331.1 –$27.0 

a Figures are in 2005 dollars. b

 Average price per engine is a weighted average price of engines by UL. 

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Economic Impact Analysis 

Table 9A-2. Impact on Small SI Engine Market 

Class II (Average Price per Engine = $310)a,b 

Small SI Engine (Class II) 

Total Change in Engine 

Absolute Change in Change in Engineering Manufacturers 

Engineering Change in Price Quantity Costs Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $3 $3 1.1% –0.3% $15.4 –$0.4 

2009 $9 $8 2.7% –0.9% $40.6 –$1.5 

2010 $9 $8 2.7% –0.9% $40.6 –$1.5 

2011 $19 $18 5.8% –1.9% $89.4 –$2.5 

2012 $18 $18 5.7% –1.9% $89.7 –$2.5 

2013 $18 $18 5.7% –1.9% $91.2 –$2.6 

2014 $18 $18 5.7% –1.9% $92.8 –$2.6 

2015 $16 $15 4.8% –1.7% $79.7 –$2.3 

2016 $16 $15 4.8% –1.6% $80.9 –$2.3 

2017 $16 $15 4.8% –1.6% $82.2 –$2.3 

2018 $16 $15 4.8% –1.6% $83.5 –$2.4 

2019 $16 $15 4.8% –1.6% $84.9 –$2.4 

2020 $16 $15 4.8% –1.6% $86.2 –$2.4 

2021 $16 $15 4.8% –1.6% $87.5 –$2.5 

2022 $16 $15 4.8% –1.6% $88.8 –$2.5 

2023 $16 $15 4.8% –1.6% $90.1 –$2.5 

2024 $16 $15 4.8% –1.6% $91.4 –$2.6 

2025 $16 $15 4.8% –1.6% $92.7 –$2.6 

2026 $16 $15 4.8% –1.6% $94.0 –$2.7 

2027 $16 $15 4.8% –1.6% $95.3 –$2.7 

2028 $16 $15 4.8% –1.6% $96.6 –$2.7 

2029 $16 $15 4.8% –1.6% $97.9 –$2.8 

2030 $16 $15 4.8% –1.6% $99.2 –$2.8 

2031 $16 $15 4.8% –1.6% $100.6 –$2.8 

2032 $16 $15 4.8% –1.6% $101.9 –$2.9 

2033 $16 $15 4.8% –1.6% $103.2 –$2.9 

2034 $16 $15 4.8% –1.6% $104.5 –$2.9 

2035 $16 $15 4.8% –1.6% $105.8 –$3.0 

2036 $16 $15 4.8% –1.6% $107.1 –$3.0 

2037 $16 $15 4.8% –1.6% $108.4 –$3.1 

NPV (3%) $1,633.5 –$46.6 

NPV (7%) $967.4 –$27.8 

a Figures are in 2005 dollars. b

 Average price per engine is a weighted average price of engines by UL. 

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Final Regulatory Impact Analysis 

Table 9A-3: Impact on Small SI Equipment Market 

Handheld (Average Price per Equipment = $210)a 

Small SI Equipment (Handheld) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $0 $0 0.1% –0.2% $2.6 –$0.4 

2009 $1 $1 0.4% –0.7% $8.3 –$1.3 

2010 $1 $1 0.4% –0.7% $8.2 –$1.3 

2011 $1 $1 0.4% –0.7% $8.3 –$1.3 

2012 $1 $1 0.3% –0.6% $7.8 –$1.2 

2013 $1 $1 0.3% –0.6% $7.9 –$1.3 

2014 $1 $1 0.3% –0.5% $6.8 –$1.1 

2015 $1 $1 0.3% –0.5% $6.9 –$1.1 

2016 $1 $1 0.3% –0.5% $7.0 –$1.1 

2017 $1 $1 0.3% –0.5% $7.1 –$1.1 

2018 $1 $1 0.3% –0.5% $7.3 –$1.2 

2019 $1 $1 0.3% –0.5% $7.4 –$1.2 

2020 $1 $1 0.3% –0.5% $7.5 –$1.2 

2021 $1 $1 0.3% –0.5% $7.6 –$1.2 

2022 $1 $1 0.3% –0.5% $7.7 –$1.2 

2023 $1 $1 0.3% –0.5% $7.8 –$1.3 

2024 $1 $1 0.3% –0.5% $7.9 –$1.3 

2025 $1 $1 0.3% –0.5% $8.0 –$1.3 

2026 $1 $1 0.3% –0.5% $8.2 –$1.3 

2027 $1 $1 0.3% –0.5% $8.3 –$1.3 

2028 $1 $1 0.3% –0.5% $8.4 –$1.3 

2029 $1 $1 0.3% –0.5% $8.5 –$1.4 

2030 $1 $1 0.3% –0.5% $8.6 –$1.4 

2031 $1 $1 0.3% –0.5% $8.7 –$1.4 

2032 $1 $1 0.3% –0.5% $8.8 –$1.4 

2033 $1 $1 0.3% –0.5% $8.9 –$1.4 

2034 $1 $1 0.3% –0.5% $9.1 –$1.5 

2035 $1 $1 0.3% –0.5% $9.2 –$1.5 

2036 $1 $1 0.3% –0.5% $9.3 –$1.5 

2037 $1 $1 0.3% –0.5% $9.4 –$1.5 

NPV (3%) $151.3 –$24.2 

NPV (7%) $92.8 –$14.8 

a Figures are in 2005 dollars. 

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Economic Impact Analysis 

Table 9A-4: Impact on Small SI Equipment Market: Class I Ag/Constr./Gen. Ind/ Material 

Handling Equipment UL 125 (Average Price per Equipment = $1,108)a 

Class 1 Agricultural/Construction/General Industrial/ Material 

Handling Equipment UL 125 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $0 $1 0.1% –0.1% $0.0 $0.0 

2009 $0 $1 0.1% –0.1% $0.0 $0.0 

2010 $0 $2 0.2% –0.2% $0.0 $0.0 

2011 $0 $2 0.2% –0.2% $0.0 $0.0 

2012 $0 $11 1.0% –1.0% $0.0 –$0.1 

2013 $0 $11 1.0% –1.0% $0.0 –$0.1 

2014 $0 $11 1.0% –1.0% $0.0 –$0.1 

2015 $0 $11 1.0% –1.0% $0.0 –$0.1 

2016 $0 $11 1.0% –1.0% $0.0 –$0.1 

2017 $0 $10 0.9% –0.9% $0.0 –$0.1 

2018 $0 $10 0.9% –0.9% $0.0 –$0.1 

2019 $0 $10 0.9% –0.9% $0.0 –$0.1 

2020 $0 $10 0.9% –0.9% $0.0 –$0.1 

2021 $0 $10 0.9% –0.9% $0.0 –$0.1 

2022 $0 $10 0.9% –0.9% $0.0 –$0.1 

2023 $0 $10 0.9% –0.9% $0.0 –$0.1 

2024 $0 $10 0.9% –0.9% $0.0 –$0.1 

2025 $0 $10 0.9% –0.9% $0.0 –$0.1 

2026 $0 $10 0.9% –0.9% $0.0 –$0.1 

2027 $0 $10 0.9% –0.9% $0.0 –$0.1 

2028 $0 $10 0.9% –0.9% $0.0 –$0.1 

2029 $0 $10 0.9% –0.9% $0.0 –$0.1 

2030 $0 $10 0.9% –0.9% $0.0 –$0.1 

2031 $0 $10 0.9% –0.9% $0.0 –$0.1 

2032 $0 $10 0.9% –0.9% $0.0 –$0.1 

2033 $0 $10 0.9% –0.9% $0.0 –$0.1 

2034 $0 $10 0.9% –0.9% $0.0 –$0.1 

2035 $0 $10 0.9% –0.9% $0.0 –$0.1 

2036 $0 $10 0.9% –0.9% $0.0 –$0.1 

2037 $0 $10 0.9% –0.9% $0.0 –$0.1 

NPV (3%) $0.0 –$1.7 

NPV (7%) $0.0 –$1.0 

a Figures are in 2005 dollars. 

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Final Regulatory Impact Analysis 

Table 9A-5: Impact on Small SI Equipment Market: Class I Utility and Recreational Vehicles UL 

125 (Average Price per Equipment = $570)a 

Small SI Equipment (Class I Utility and Recreational Vehicles UL 

125) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $0 $1 0.1% –0.1% $0.0 $0.0 

2009 $0 $1 0.1% –0.1% $0.0 $0.0 

2010 $0 $2 0.4% –0.4% $0.0 $0.0 

2011 $0 $2 0.4% –0.4% $0.0 $0.0 

2012 $0 $11 2.0% –2.0% $0.0 –$0.1 

2013 $0 $11 2.0% –2.0% $0.0 –$0.1 

2014 $0 $11 2.0% –2.0% $0.0 –$0.1 

2015 $0 $11 2.0% –2.0% $0.0 –$0.1 

2016 $0 $11 2.0% –2.0% $0.0 –$0.1 

2017 $0 $10 1.8% –1.8% $0.0 –$0.1 

2018 $0 $10 1.8% –1.8% $0.0 –$0.1 

2019 $0 $10 1.8% –1.8% $0.0 –$0.1 

2020 $0 $10 1.8% –1.8% $0.0 –$0.1 

2021 $0 $10 1.8% –1.8% $0.0 –$0.1 

2022 $0 $10 1.8% –1.8% $0.0 –$0.1 

2023 $0 $10 1.8% –1.8% $0.0 –$0.1 

2024 $0 $10 1.8% –1.8% $0.0 –$0.1 

2025 $0 $10 1.8% –1.8% $0.0 –$0.1 

2026 $0 $10 1.8% –1.8% $0.0 –$0.1 

2027 $0 $10 1.8% –1.8% $0.0 –$0.1 

2028 $0 $10 1.8% –1.8% $0.0 –$0.1 

2029 $0 $10 1.8% –1.8% $0.0 –$0.1 

2030 $0 $10 1.8% –1.8% $0.0 –$0.1 

2031 $0 $10 1.8% –1.8% $0.0 –$0.1 

2032 $0 $10 1.8% –1.8% $0.0 –$0.1 

2033 $0 $10 1.8% –1.8% $0.0 –$0.1 

2034 $0 $10 1.8% –1.8% $0.0 –$0.1 

2035 $0 $10 1.8% –1.8% $0.0 –$0.1 

2036 $0 $10 1.8% –1.8% $0.0 –$0.1 

2037 $0 $10 1.8% –1.8% $0.0 –$0.1 

NPV (3%) $0.0 –$1.9 

NPV (7%) $0.0 –$1.1 

a Figures are in 2005 dollars. 

9-78 
Economic Impact Analysis 

Table 9A-6: Impact on Small SI Equipment Market: Class I Lawn Mowers UL 125 

(Average Price per Equipment = $218)a 

Small SI Equipment (Class I Lawn Mowers UL 125) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $0 $1 0.4% –0.1% $0.0 –$0.1 

2009 $0 $1 0.4% –0.1% $0.0 –$0.1 

2010 $0 $2 1.1% –0.2% $0.0 –$0.3 

2011 $0 $2 1.1% –0.2% $0.0 –$0.3 

2012 $0 $12 5.6% –1.1% $0.0 –$1.6 

2013 $0 $12 5.5% –1.1% $0.0 –$1.6 

2014 $0 $12 5.5% –1.1% $0.0 –$1.7 

2015 $0 $12 5.5% –1.1% $0.0 –$1.7 

2016 $0 $12 5.5% –1.1% $0.0 –$1.7 

2017 $0 $11 5.0% –0.9% $0.0 –$1.6 

2018 $0 $11 5.0% –0.9% $0.0 –$1.6 

2019 $0 $11 5.0% –0.9% $0.0 –$1.6 

2020 $0 $11 5.0% –0.9% $0.0 –$1.6 

2021 $0 $11 5.0% –0.9% $0.0 –$1.7 

2022 $0 $11 5.0% –0.9% $0.0 –$1.7 

2023 $0 $11 5.0% –0.9% $0.0 –$1.7 

2024 $0 $11 5.0% –0.9% $0.0 –$1.7 

2025 $0 $11 5.0% –0.9% $0.0 –$1.8 

2026 $0 $11 5.0% –0.9% $0.0 –$1.8 

2027 $0 $11 5.0% –0.9% $0.0 –$1.8 

2028 $0 $11 5.0% –0.9% $0.0 –$1.8 

2029 $0 $11 5.0% –0.9% $0.0 –$1.9 

2030 $0 $11 5.0% –0.9% $0.0 –$1.9 

2031 $0 $11 5.0% –0.9% $0.0 –$1.9 

2032 $0 $11 5.0% –0.9% $0.0 –$1.9 

2033 $0 $11 5.0% –0.9% $0.0 –$2.0 

2034 $0 $11 5.0% –0.9% $0.0 –$2.0 

2035 $0 $11 5.0% –0.9% $0.0 –$2.0 

2036 $0 $11 5.0% –0.9% $0.0 –$2.0 

2037 $0 $11 5.0% –0.9% $0.0 –$2.1 

NPV (3%) $0.0 –$28.6 

NPV (7%) $0.0 –$16.2 

a Figures are in 2005 dollars. 

9-79 
Final Regulatory Impact Analysis 

Table 9A-7: Impact on Small SI Equipment Market: Class I Other Lawn and Garden Equipment 

UL 125 (Average Price per Equipment = $245)a 

Small SI Equipment (Class I Other Lawn and Garden Equipment 

UL 125) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $0 $1 0.3% –0.3% $0.0 –$0.1 

2009 $0 $1 0.3% –0.3% $0.0 –$0.1 

2010 $0 $2 0.9% –0.8% $0.0 –$0.1 

2011 $0 $2 0.9% –0.8% $0.0 –$0.1 

2012 $0 $11 4.7% –4.2% $0.0 –$0.7 

2013 $0 $11 4.6% –4.1% $0.0 –$0.8 

2014 $0 $11 4.6% –4.1% $0.0 –$0.8 

2015 $0 $11 4.6% –4.1% $0.0 –$0.8 

2016 $0 $11 4.6% –4.1% $0.0 –$0.8 

2017 $0 $10 4.2% –3.7% $0.0 –$0.7 

2018 $0 $10 4.2% –3.7% $0.0 –$0.7 

2019 $0 $10 4.2% –3.7% $0.0 –$0.7 

2020 $0 $10 4.2% –3.7% $0.0 –$0.8 

2021 $0 $10 4.2% –3.7% $0.0 –$0.8 

2022 $0 $10 4.2% –3.7% $0.0 –$0.8 

2023 $0 $10 4.2% –3.7% $0.0 –$0.8 

2024 $0 $10 4.2% –3.7% $0.0 –$0.8 

2025 $0 $10 4.2% –3.7% $0.0 –$0.8 

2026 $0 $10 4.2% –3.7% $0.0 –$0.8 

2027 $0 $10 4.2% –3.7% $0.0 –$0.8 

2028 $0 $10 4.2% –3.7% $0.0 –$0.8 

2029 $0 $10 4.2% –3.7% $0.0 –$0.9 

2030 $0 $10 4.2% –3.7% $0.0 –$0.9 

2031 $0 $10 4.2% –3.7% $0.0 –$0.9 

2032 $0 $10 4.2% –3.7% $0.0 –$0.9 

2033 $0 $10 4.2% –3.7% $0.0 –$0.9 

2034 $0 $10 4.2% –3.7% $0.0 –$0.9 

2035 $0 $10 4.2% –3.7% $0.0 –$0.9 

2036 $0 $10 4.2% –3.7% $0.0 –$0.9 

2037 $0 $10 4.2% –3.7% $0.0 –$1.0 

NPV (3%) $0.0 –$13.1 

NPV (7%) $0.0 –$7.4 

a Figures are in 2005 dollars. 

9-80 
Economic Impact Analysis 

Table 9A-8: Impact on Small SI Equipment Market: Class I Gensets/Welders UL 125 

(Average Price per Equipment = $999)a 

Small SI Equipment (Class I Gensets/Welders UL 125) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $0 $1 0.1% –0.1% $0.0 $0.0 

2009 $0 $1 0.1% –0.1% $0.0 $0.0 

2010 $0 $2 0.2% –0.3% $0.0 –$0.1 

2011 $0 $2 0.2% –0.3% $0.0 –$0.1 

2012 $0 $11 1.1% –1.5% $0.0 –$0.5 

2013 $0 $11 1.1% –1.5% $0.0 –$0.5 

2014 $0 $11 1.1% –1.5% $0.0 –$0.5 

2015 $0 $11 1.1% –1.5% $0.0 –$0.5 

2016 $0 $11 1.1% –1.5% $0.0 –$0.5 

2017 $0 $10 1.0% –1.4% $0.0 –$0.5 

2018 $0 $10 1.0% –1.4% $0.0 –$0.5 

2019 $0 $10 1.0% –1.4% $0.0 –$0.5 

2020 $0 $10 1.0% –1.4% $0.0 –$0.5 

2021 $0 $10 1.0% –1.4% $0.0 –$0.5 

2022 $0 $10 1.0% –1.4% $0.0 –$0.5 

2023 $0 $10 1.0% –1.4% $0.0 –$0.5 

2024 $0 $10 1.0% –1.4% $0.0 –$0.5 

2025 $0 $10 1.0% –1.4% $0.0 –$0.5 

2026 $0 $10 1.0% –1.4% $0.0 –$0.5 

2027 $0 $10 1.0% –1.4% $0.0 –$0.6 

2028 $0 $10 1.0% –1.4% $0.0 –$0.6 

2029 $0 $10 1.0% –1.4% $0.0 –$0.6 

2030 $0 $10 1.0% –1.4% $0.0 –$0.6 

2031 $0 $10 1.0% –1.4% $0.0 –$0.6 

2032 $0 $10 1.0% –1.4% $0.0 –$0.6 

2033 $0 $10 1.0% –1.4% $0.0 –$0.6 

2034 $0 $10 1.0% –1.4% $0.0 –$0.6 

2035 $0 $10 1.0% –1.4% $0.0 –$0.6 

2036 $0 $10 1.0% –1.4% $0.0 –$0.6 

2037 $0 $10 1.0% –1.4% $0.0 –$0.6 

NPV (3%) $0.0 –$8.7 

NPV (7%) $0.0 –$4.9 

a Figures are in 2005 dollars. 

9-81 
Final Regulatory Impact Analysis 

Table 9A-9: Impact on Small SI Equipment Market: Class I Pumps/Compressors/Pressure 

Washers UL 125 (Average Price per Equipment = $96)a 

Small SI Equipment (Class I Pumps/Compressors/Pressure 

Washers UL 125) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $0 $1 0.8% –0.7% $0.0 $0.0 

2009 $0 $1 0.8% –0.7% $0.0 –$0.1 

2010 $0 $2 2.3% –2.3% $0.0 –$0.1 

2011 $0 $2 2.2% –2.2% $0.0 –$0.1 

2012 $0 $11 11.8% –11.8% $0.0 –$0.7 

2013 $0 $11 11.7% –11.6% $0.0 –$0.7 

2014 $0 $11 11.7% –11.6% $0.0 –$0.8 

2015 $0 $11 11.6% –11.6% $0.0 –$0.8 

2016 $0 $11 11.6% –11.6% $0.0 –$0.8 

2017 $0 $10 10.5% –10.4% $0.0 –$0.7 

2018 $0 $10 10.5% –10.4% $0.0 –$0.7 

2019 $0 $10 10.5% –10.4% $0.0 –$0.7 

2020 $0 $10 10.5% –10.4% $0.0 –$0.8 

2021 $0 $10 10.5% –10.4% $0.0 –$0.8 

2022 $0 $10 10.5% –10.4% $0.0 –$0.8 

2023 $0 $10 10.5% –10.4% $0.0 –$0.8 

2024 $0 $10 10.5% –10.4% $0.0 –$0.8 

2025 $0 $10 10.5% –10.4% $0.0 –$0.8 

2026 $0 $10 10.5% –10.4% $0.0 –$0.8 

2027 $0 $10 10.5% –10.4% $0.0 –$0.8 

2028 $0 $10 10.5% –10.4% $0.0 –$0.8 

2029 $0 $10 10.5% –10.4% $0.0 –$0.9 

2030 $0 $10 10.5% –10.4% $0.0 –$0.9 

2031 $0 $10 10.5% –10.4% $0.0 –$0.9 

2032 $0 $10 10.5% –10.4% $0.0 –$0.9 

2033 $0 $10 10.5% –10.4% $0.0 –$0.9 

2034 $0 $10 10.5% –10.4% $0.0 –$0.9 

2035 $0 $10 10.5% –10.4% $0.0 –$0.9 

2036 $0 $10 10.5% –10.4% $0.0 –$0.9 

2037 $0 $10 10.5% –10.4% $0.0 –$0.9 

NPV (3%) $0.0 –$13.0 

NPV (7%) $0.0 –$7.4 

a Figures are in 2005 dollars. 

9-82 
Economic Impact Analysis 

Table 9A-10: Impact on Small SI Equipment Market: Class I Snowblowers UL 125 

(Average Price per Equipment = $324)a 

Small SI Equipment (Class I Snowblowers UL 125) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $0 $0 0.1% –0.1% $0.0 $0.0 

2009 $0 $0 0.1% –0.1% $0.0 $0.0 

2010 $0 $1 0.2% –0.2% $0.0 $0.0 

2011 $0 $1 0.2% –0.2% $0.0 $0.0 

2012 $0 $3 0.8% –0.8% $0.0 –$0.2 

2013 $0 $2 0.8% –0.8% $0.0 –$0.2 

2014 $0 $2 0.8% –0.8% $0.0 –$0.2 

2015 $0 $2 0.8% –0.8% $0.0 –$0.2 

2016 $0 $2 0.8% –0.8% $0.0 –$0.2 

2017 $0 $2 0.6% –0.6% $0.0 –$0.2 

2018 $0 $2 0.6% –0.6% $0.0 –$0.2 

2019 $0 $2 0.6% –0.6% $0.0 –$0.2 

2020 $0 $2 0.6% –0.6% $0.0 –$0.2 

2021 $0 $2 0.6% –0.6% $0.0 –$0.2 

2022 $0 $2 0.6% –0.6% $0.0 –$0.2 

2023 $0 $2 0.6% –0.6% $0.0 –$0.2 

2024 $0 $2 0.6% –0.6% $0.0 –$0.2 

2025 $0 $2 0.6% –0.6% $0.0 –$0.2 

2026 $0 $2 0.6% –0.6% $0.0 –$0.2 

2027 $0 $2 0.6% –0.6% $0.0 –$0.2 

2028 $0 $2 0.6% –0.6% $0.0 –$0.2 

2029 $0 $2 0.6% –0.6% $0.0 –$0.2 

2030 $0 $2 0.6% –0.6% $0.0 –$0.2 

2031 $0 $2 0.6% –0.6% $0.0 –$0.2 

2032 $0 $2 0.6% –0.6% $0.0 –$0.2 

2033 $0 $2 0.6% –0.6% $0.0 –$0.2 

2034 $0 $2 0.6% –0.6% $0.0 –$0.2 

2035 $0 $2 0.6% –0.6% $0.0 –$0.2 

2036 $0 $2 0.6% –0.6% $0.0 –$0.2 

2037 $0 $2 0.6% –0.6% $0.0 –$0.2 

NPV (3%) $0.0 –$2.8 

NPV (7%) $0.0 –$1.6 

a Figures are in 2005 dollars. 

9-83 
Final Regulatory Impact Analysis 

Table 9A-11: Impact on Small SI Equipment Market: Class II Agri/Constr./G. Ind/ Material 

Handling Equipment UL 250 (Average Price per Equipment = $1,825)a 

Small SI Equipment (Class II Agricultural/Construction/ General 

Industrial/ Material Handling Equipment UL 250) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $2 $3 0.1% –0.1% $0.0 $0.0 

2009 $6 $8 0.5% –0.5% $0.5 –$0.1 

2010 $5 $8 0.4% –0.4% $0.5 –$0.1 

2011 $10 $24 1.3% –1.3% $0.8 –$0.2 

2012 $10 $24 1.3% –1.3% $0.8 –$0.2 

2013 $9 $23 1.3% –1.3% $0.8 –$0.2 

2014 $9 $23 1.3% –1.3% $0.9 –$0.2 

2015 $9 $21 1.2% –1.2% $0.9 –$0.2 

2016 $8 $20 1.1% –1.1% $0.8 –$0.2 

2017 $8 $20 1.1% –1.1% $0.8 –$0.2 

2018 $8 $20 1.1% –1.1% $0.8 –$0.2 

2019 $8 $20 1.1% –1.1% $0.8 –$0.2 

2020 $8 $20 1.1% –1.1% $0.8 –$0.2 

2021 $8 $20 1.1% –1.1% $0.8 –$0.2 

2022 $8 $20 1.1% –1.1% $0.8 –$0.2 

2023 $8 $20 1.1% –1.1% $0.9 –$0.2 

2024 $8 $20 1.1% –1.1% $0.9 –$0.2 

2025 $8 $20 1.1% –1.1% $0.9 –$0.2 

2026 $8 $20 1.1% –1.1% $0.9 –$0.2 

2027 $8 $20 1.1% –1.1% $0.9 –$0.2 

2028 $8 $20 1.1% –1.1% $0.9 –$0.2 

2029 $8 $20 1.1% –1.1% $0.9 –$0.2 

2030 $8 $20 1.1% –1.1% $0.9 –$0.2 

2031 $8 $20 1.1% –1.1% $1.0 –$0.2 

2032 $8 $20 1.1% –1.1% $1.0 –$0.2 

2033 $8 $20 1.1% –1.1% $1.0 –$0.2 

2034 $8 $20 1.1% –1.1% $1.0 –$0.2 

2035 $8 $20 1.1% –1.1% $1.0 –$0.3 

2036 $8 $20 1.1% –1.1% $1.0 –$0.3 

2037 $8 $20 1.1% –1.1% $1.0 –$0.3 

NPV (3%) $15.7 –$3.7 

NPV (7%) $9.3 –$2.2 

a Figures are in 2005 dollars. 

9-84 
Economic Impact Analysis 

Table 9A-12: Impact on Small SI Equipment Market: Class II Utility and Recreational Vehicle UL 

250 (Average Price per Equipment = $2,894)a 

Small SI Equipment (Class II Utility and Recreational Vehicle UL 

250) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $1 $2 0.1% –0.1% $0.3 –$0.1 

2009 $5 $8 0.3% –0.3% $1.0 –$0.2 

2010 $5 $7 0.3% –0.3% $1.0 –$0.2 

2011 $8 $22 0.8% –0.8% $1.7 –$0.5 

2012 $8 $22 0.8% –0.8% $1.7 –$0.5 

2013 $8 $22 0.8% –0.8% $1.7 –$0.5 

2014 $8 $22 0.8% –0.8% $1.7 –$0.5 

2015 $7 $20 0.7% –0.7% $1.8 –$0.5 

2016 $7 $19 0.6% –0.6% $1.6 –$0.4 

2017 $7 $19 0.6% –0.6% $1.6 –$0.4 

2018 $7 $19 0.6% –0.6% $1.6 –$0.4 

2019 $7 $19 0.6% –0.6% $1.6 –$0.5 

2020 $7 $19 0.6% –0.6% $1.7 –$0.5 

2021 $7 $19 0.6% –0.6% $1.7 –$0.5 

2022 $7 $19 0.6% –0.6% $1.7 –$0.5 

2023 $7 $19 0.6% –0.6% $1.7 –$0.5 

2024 $7 $19 0.6% –0.6% $1.8 –$0.5 

2025 $7 $19 0.6% –0.6% $1.8 –$0.5 

2026 $7 $19 0.6% –0.6% $1.8 –$0.5 

2027 $7 $19 0.6% –0.6% $1.8 –$0.5 

2028 $7 $19 0.6% –0.6% $1.9 –$0.5 

2029 $7 $19 0.6% –0.6% $1.9 –$0.5 

2030 $7 $19 0.6% –0.6% $1.9 –$0.5 

2031 $7 $19 0.6% –0.6% $1.9 –$0.5 

2032 $7 $19 0.6% –0.6% $2.0 –$0.5 

2033 $7 $19 0.6% –0.6% $2.0 –$0.6 

2034 $7 $19 0.6% –0.6% $2.0 –$0.6 

2035 $7 $19 0.6% –0.6% $2.0 –$0.6 

2036 $7 $19 0.6% –0.6% $2.1 –$0.6 

2037 $7 $19 0.6% –0.6% $2.1 –$0.6 

NPV (3%) $31.8 –$8.5 

NPV (7%) $19.0 $5.0 

a Figures are in 2005 dollars. 

9-85 
Final Regulatory Impact Analysis 

Table 9A-13: Impact on Small SI Equipment Market: Class II Tractors UL 250 (Average 

Price per Equipment = $1,937)a 

Small SI Equipment (Class II Tractors UL 250) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $1 $3 0.1% –0.1% $2.9 –$0.5 

2009 $6 $9 0.4% –0.4% $12.0 –$1.7 

2010 $6 $8 0.4% –0.4% $11.6 –$1.7 

2011 $7 $21 1.1% –1.1% $14.6 –$4.4 

2012 $7 $21 1.1% –1.1% $14.8 –$4.5 

2013 $7 $21 1.1% –1.1% $14.8 –$4.5 

2014 $7 $21 1.1% –1.1% $15.1 –$4.6 

2015 $7 $19 1.0% –1.0% $15.3 –$4.2 

2016 $6 $18 0.9% –0.9% $13.7 –$4.1 

2017 $6 $18 0.9% –0.9% $13.9 –$4.1 

2018 $6 $18 0.9% –0.9% $14.1 –$4.2 

2019 $6 $18 0.9% –0.9% $14.3 –$4.3 

2020 $6 $18 0.9% –0.9% $14.5 –$4.3 

2021 $6 $18 0.9% –0.9% $14.8 –$4.4 

2022 $6 $18 0.9% –0.9% $15.0 –$4.5 

2023 $6 $18 0.9% –0.9% $15.2 –$4.5 

2024 $6 $18 0.9% –0.9% $15.4 –$4.6 

2025 $6 $18 0.9% –0.9% $15.6 –$4.6 

2026 $6 $18 0.9% –0.9% $15.9 –$4.7 

2027 $6 $18 0.9% –0.9% $16.1 –$4.8 

2028 $6 $18 0.9% –0.9% $16.3 –$4.8 

2029 $6 $18 0.9% –0.9% $16.5 –$4.9 

2030 $6 $18 0.9% –0.9% $16.7 –$5.0 

2031 $6 $18 0.9% –0.9% $17.0 –$5.0 

2032 $6 $18 0.9% –0.9% $17.2 –$5.1 

2033 $6 $18 0.9% –0.9% $17.4 –$5.2 

2034 $6 $18 0.9% –0.9% $17.6 –$5.2 

2035 $6 $18 0.9% –0.9% $17.9 –$5.3 

2036 $6 $18 0.9% –0.9% $18.1 –$5.4 

2037 $6 $18 0.9% –0.9% $18.3 –$5.4 

NPV (3%) $284.9 –$81.0 

NPV (7%) $171.7 –$47.6 

a Figures are in 2005 dollars. 

9-86 
Economic Impact Analysis 

Table 9A-14: Impact on Small SI Equipment Market: Class II Other Lawn and Garden Equipment 

UL 250 (Average Price per Equipment = $312)a 

Small SI Equipment (Class II Other Lawn and Garden Equipment 

UL 250) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $1 $2 0.6% –0.6% $0.1 $0.0 

2009 $4 $7 2.2% –2.0% $0.6 –$0.1 

2010 $4 $7 2.1% –1.9% $0.6 –$0.1 

2011 $5 $20 6.4% –5.8% $0.8 –$0.3 

2012 $5 $20 6.4% –5.7% $0.9 –$0.3 

2013 $5 $20 6.4% –5.7% $0.9 –$0.3 

2014 $5 $20 6.4% –5.7% $0.9 –$0.3 

2015 $5 $18 5.6% –5.1% $0.9 –$0.3 

2016 $5 $17 5.4% –5.0% $0.8 –$0.3 

2017 $5 $17 5.4% –4.9% $0.8 –$0.3 

2018 $5 $17 5.4% –4.9% $0.8 –$0.3 

2019 $5 $17 5.4% –4.9% $0.8 –$0.3 

2020 $5 $17 5.4% –4.9% $0.8 –$0.3 

2021 $5 $17 5.4% –4.9% $0.8 –$0.3 

2022 $5 $17 5.4% –4.9% $0.9 –$0.3 

2023 $5 $17 5.4% –4.9% $0.9 –$0.3 

2024 $5 $17 5.4% –4.9% $0.9 –$0.3 

2025 $5 $17 5.4% –4.9% $0.9 –$0.3 

2026 $5 $17 5.4% –4.9% $0.9 –$0.3 

2027 $5 $17 5.4% –4.9% $0.9 –$0.3 

2028 $5 $17 5.4% –4.9% $0.9 –$0.3 

2029 $5 $17 5.4% –4.9% $0.9 –$0.3 

2030 $5 $17 5.4% –4.9% $1.0 –$0.3 

2031 $5 $17 5.4% –4.9% $1.0 –$0.3 

2032 $5 $17 5.4% –4.9% $1.0 –$0.3 

2033 $5 $17 5.4% –4.9% $1.0 –$0.3 

2034 $5 $17 5.4% –4.9% $1.0 –$0.3 

2035 $5 $17 5.4% –4.9% $1.0 –$0.3 

2036 $5 $17 5.4% –4.9% $1.0 –$0.3 

2037 $5 $17 5.4% –4.9% $1.0 –$0.3 

NPV (3%) $16.2 –$5.0 

NPV (7%) $9.7 –$2.9 

a Figures are in 2005 dollars. 

9-87 
Final Regulatory Impact Analysis 

Table 9A-15: Impact on Small SI Equipment Market: Class II Gensets/Welders UL 250 

(Average Price per Equipment = $666)a 

Small SI Equipment (Class II Gensets/Welders UL 250) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $2 $3 0.4% –0.4% $1.1 –$0.2 

2009 $6 $8 1.2% –1.4% $4.2 –$0.7 

2010 $6 $8 1.2% –1.3% $4.0 –$0.7 

2011 $10 $24 3.5% –3.9% $7.4 –$2.1 

2012 $10 $23 3.5% –3.9% $7.5 –$2.2 

2013 $10 $23 3.5% –3.9% $7.6 –$2.2 

2014 $10 $23 3.5% –3.9% $7.7 –$2.2 

2015 $10 $21 3.2% –3.5% $7.8 –$2.1 

2016 $9 $20 3.0% –3.3% $6.8 –$2.0 

2017 $9 $20 3.0% –3.3% $7.0 –$2.0 

2018 $9 $20 3.0% –3.3% $7.1 –$2.0 

2019 $9 $20 3.0% –3.3% $7.2 –$2.1 

2020 $9 $20 3.0% –3.3% $7.3 –$2.1 

2021 $9 $20 3.0% –3.3% $7.4 –$2.1 

2022 $9 $20 3.0% –3.3% $7.5 –$2.1 

2023 $9 $20 3.0% –3.3% $7.6 –$2.2 

2024 $9 $20 3.0% –3.3% $7.7 –$2.2 

2025 $9 $20 3.0% –3.3% $7.8 –$2.2 

2026 $9 $20 3.0% –3.3% $8.0 –$2.3 

2027 $9 $20 3.0% –3.3% $8.1 –$2.3 

2028 $9 $20 3.0% –3.3% $8.2 –$2.3 

2029 $9 $20 3.0% –3.3% $8.3 –$2.4 

2030 $9 $20 3.0% –3.3% $8.4 –$2.4 

2031 $9 $20 3.0% –3.3% $8.5 –$2.4 

2032 $9 $20 3.0% –3.3% $8.6 –$2.5 

2033 $9 $20 3.0% –3.3% $8.7 –$2.5 

2034 $9 $20 3.0% –3.3% $8.8 –$2.5 

2035 $9 $20 3.0% –3.3% $9.0 –$2.6 

2036 $9 $20 3.0% –3.3% $9.1 –$2.6 

2037 $9 $20 3.0% –3.3% $9.2 –$2.6 

NPV (3%) $139.8 –$38.9 

NPV (7%) $83.1 –$22.8 

a Figures are in 2005 dollars. 

9-88 
Economic Impact Analysis 

Table 9A-16: Impact on Small SI Equipment Market: Class II Pumps/Compressors/ Pressure 

Washers UL 250 (Average Price per Equipment = $349)a 

Small SI Equipment (Class II Pumps/Compressors/Pressure 

Washers UL 250) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $1 $2 0.7% –0.7% $0.4 –$0.1 

2009 $5 $8 2.3% –2.3% $1.6 –$0.2 

2010 $5 $8 2.2% –2.2% $1.5 –$0.2 

2011 $9 $23 6.5% –6.6% $2.6 –$0.7 

2012 $9 $23 6.5% –6.5% $2.7 –$0.7 

2013 $8 $22 6.4% –6.4% $2.7 –$0.7 

2014 $8 $22 6.4% –6.4% $2.7 –$0.7 

2015 $8 $20 5.8% –5.9% $2.8 –$0.7 

2016 $7 $19 5.5% –5.5% $2.4 –$0.6 

2017 $7 $19 5.5% –5.5% $2.5 –$0.6 

2018 $7 $19 5.5% –5.5% $2.5 –$0.7 

2019 $7 $19 5.5% –5.5% $2.5 –$0.7 

2020 $7 $19 5.5% –5.5% $2.6 –$0.7 

2021 $7 $19 5.5% –5.5% $2.6 –$0.7 

2022 $7 $19 5.5% –5.5% $2.7 –$0.7 

2023 $7 $19 5.5% –5.5% $2.7 –$0.7 

2024 $7 $19 5.5% –5.5% $2.7 –$0.7 

2025 $7 $19 5.5% –5.5% $2.8 –$0.7 

2026 $7 $19 5.5% –5.5% $2.8 –$0.7 

2027 $7 $19 5.5% –5.5% $2.9 –$0.7 

2028 $7 $19 5.5% –5.5% $2.9 –$0.8 

2029 $7 $19 5.5% –5.5% $2.9 –$0.8 

2030 $7 $19 5.5% –5.5% $3.0 –$0.8 

2031 $7 $19 5.5% –5.5% $3.0 –$0.8 

2032 $7 $19 5.5% –5.5% $3.1 –$0.8 

2033 $7 $19 5.5% –5.5% $3.1 –$0.8 

2034 $7 $19 5.5% –5.5% $3.1 –$0.8 

2035 $7 $19 5.5% –5.5% $3.2 –$0.8 

2036 $7 $19 5.5% –5.5% $3.2 –$0.8 

2037 $7 $19 5.5% –5.5% $3.2 –$0.8 

NPV (3%) $49.6 –$12.5 

NPV (7%) $29.5 –$7.3 

a Figures are in 2005 dollars. 

9-89 
Final Regulatory Impact Analysis 

Table 9A-17: Impact on Small SI Equipment Market: Class II Snowblowers UL 250 

(Average Price per Equipment = $665)a 

Small SI Equipment (Class II Snowblowers UL 250) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $1 $1 0.1% –0.1% $0.4 $0.0 

2009 $1 $1 0.1% –0.1% $0.5 –$0.1 

2010 $1 $1 0.1% –0.1% $0.4 $0.0 

2011 $4 $4 0.5% –0.5% $2.3 –$0.2 

2012 $4 $4 0.5% –0.5% $2.3 –$0.2 

2013 $4 $4 0.5% –0.5% $2.3 –$0.2 

2014 $4 $4 0.5% –0.5% $2.3 –$0.2 

2015 $4 $4 0.5% –0.5% $2.4 –$0.2 

2016 $3 $3 0.4% –0.4% $2.0 –$0.2 

2017 $3 $3 0.4% –0.4% $2.1 –$0.2 

2018 $3 $3 0.4% –0.4% $2.1 –$0.2 

2019 $3 $3 0.4% –0.4% $2.1 –$0.2 

2020 $3 $3 0.4% –0.4% $2.2 –$0.2 

2021 $3 $3 0.4% –0.4% $2.2 –$0.2 

2022 $3 $3 0.4% –0.4% $2.2 –$0.2 

2023 $3 $3 0.4% –0.4% $2.3 –$0.2 

2024 $3 $3 0.4% –0.4% $2.3 –$0.2 

2025 $3 $3 0.4% –0.4% $2.3 –$0.2 

2026 $3 $3 0.4% –0.4% $2.4 –$0.2 

2027 $3 $3 0.4% –0.4% $2.4 –$0.2 

2028 $3 $3 0.4% –0.4% $2.4 –$0.2 

2029 $3 $3 0.4% –0.4% $2.5 –$0.2 

2030 $3 $3 0.4% –0.4% $2.5 –$0.2 

2031 $3 $3 0.4% –0.4% $2.5 –$0.2 

2032 $3 $3 0.4% –0.4% $2.6 –$0.2 

2033 $3 $3 0.4% –0.4% $2.6 –$0.2 

2034 $3 $3 0.4% –0.4% $2.6 –$0.2 

2035 $3 $3 0.4% –0.4% $2.6 –$0.2 

2036 $3 $3 0.4% –0.4% $2.7 –$0.2 

2037 $3 $3 0.4% –0.4% $2.7 –$0.3 

NPV (3%) $40.4 –$3.7 

NPV (7%) $23.7 –$2.2 

a Figures are in 2005 dollars. 

9-90 
Economic Impact Analysis 

Appendix 9B: Impacts on Marine SI Markets 

This appendix provides the time series of impacts from 2008 through 2037 for the 

following Small SI engines and equipment markets; a complete set of results for all markets can be 

found in the docket for this rule (Li, 2008). For engine markets, Results are presented for the 

aggregated categories by power. For the vessel markets, results are presented for the categories 

with the highest sales. 

• Marine SI engines: <25 hp; 26-50 hp; 51-100 hp; 101-175 hp; 176-300 hp; >300 hp 

• SD/I, 175-300 hp and >300 hp 

• OB recreational, 50-100 hp 

• OB luxury, 175-300 hp 

• PWC 100-175 hp 

Table 9B-1 through Table 9B-11 provide the time series of impacts for each engine class 

market and each selected equipment market, respectively, includes the following: 

• average engine or equipment price 

• average engineering costs (variable and fixed) per engine or equipment 

• absolute change in the market price ($) 

• relative change in market price (%) 

• relative change in market quantity (%) 

• total engineering costs associated with each engine or equipment market 

• changes in producer surplus associated with each engine or equipment market 

All prices and costs are presented in 2005 dollars and real engine or equipment prices are 

assumed to be constant during the period of analysis. Net present values were estimated using 

social discount rates of 3 percent and 7 percent over the period of analysis. 

9-91 
Final Regulatory Impact Analysis 

Table 9B-1: Impact on Marine SI Engine Market: 

<25hp (Average Price per Engine = $2,500)a,b 

Marine SI Engine (<25hp) 

Total Change in Engine 

Absolute Change in Change in Engineering Manufacturers 

Engineering Change in Price Quantity Costs Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $12 $10 0.4% –0.8% $0.8 –$0.2 

2009 $12 $8 0.3% –1.6% $0.8 –$0.3 

2010 $69 $54 2.2% –5.5% $4.7 –$1.0 

2011 $69 $55 2.2% –5.2% $4.8 –$1.0 

2012 $69 $55 2.2% –5.2% $4.8 –$1.0 

2013 $69 $55 2.2% –5.2% $4.8 –$1.0 

2014 $69 $55 2.2% –5.2% $4.9 –$1.0 

2015 $55 $44 1.7% –4.3% $3.9 –$0.8 

2016 $55 $44 1.7% –4.3% $3.9 –$0.8 

2017 $55 $44 1.7% –4.3% $4.0 –$0.8 

2018 $55 $44 1.7% –4.3% $4.0 –$0.8 

2019 $55 $44 1.7% –4.3% $4.0 –$0.8 

2020 $55 $44 1.7% –4.3% $4.1 –$0.8 

2021 $55 $44 1.7% –4.3% $4.1 –$0.8 

2022 $55 $44 1.7% –4.3% $4.1 –$0.9 

2023 $55 $44 1.7% –4.3% $4.1 –$0.9 

2024 $55 $44 1.7% –4.3% $4.2 –$0.9 

2025 $55 $44 1.7% –4.3% $4.2 –$0.9 

2026 $55 $44 1.7% –4.3% $4.2 –$0.9 

2027 $55 $44 1.7% –4.3% $4.3 –$0.9 

2028 $55 $44 1.7% –4.3% $4.3 –$0.9 

2029 $55 $44 1.7% –4.3% $4.3 –$0.9 

2030 $55 $44 1.7% –4.3% $4.3 –$0.9 

2031 $55 $44 1.7% –4.3% $4.4 –$0.9 

2032 $55 $44 1.7% –4.3% $4.4 –$0.9 

2033 $55 $44 1.7% –4.3% $4.4 –$0.9 

2034 $55 $44 1.7% –4.3% $4.4 –$0.9 

2035 $55 $44 1.7% –4.3% $4.5 –$0.9 

2036 $55 $44 1.7% –4.3% $4.5 –$0.9 

2037 $55 $44 1.7% –4.3% $4.5 –$0.9 

NPV (3%) $78.2 –$16.1 

NPV (7%) $47.7 –$9.8 

a Figures are in 2005 dollars. b Average price per engine is a weighted average price of engine by equipment type. 

9-92 
Economic Impact Analysis 

Table 9B-2: Impact on Marine SI Engine Market: 

26–50hp (Average Price per Engine = $5,700)a,b 

Marine SI Engine (26–50hp) 

Total Change in Engine 

Absolute Change in Change in Engineering Manufacturers 

Engineering Change in Price Quantity Costs Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $14 $12 0.2% –0.2% $0.7 –$0.1 

2009 $14 $12 0.2% –0.3% $0.7 –$0.1 

2010 $216 $198 3.5% –3.0% $11.0 –$0.9 

2011 $216 $197 3.5% –3.2% $11.1 –$1.0 

2012 $216 $196 3.4% –3.4% $11.2 –$1.0 

2013 $216 $196 3.4% –3.4% $11.2 –$1.1 

2014 $216 $196 3.4% –3.4% $11.3 –$1.1 

2015 $173 $156 2.7% –2.8% $9.1 –$0.9 

2016 $173 $156 2.7% –2.8% $9.2 –$0.9 

2017 $173 $157 2.7% –2.7% $9.2 –$0.9 

2018 $173 $157 2.7% –2.7% $9.3 –$0.9 

2019 $173 $157 2.7% –2.7% $9.4 –$0.9 

2020 $173 $157 2.7% –2.7% $9.4 –$0.9 

2021 $173 $157 2.7% –2.7% $9.5 –$0.9 

2022 $173 $157 2.7% –2.7% $9.6 –$0.9 

2023 $173 $157 2.7% –2.7% $9.6 –$0.9 

2024 $173 $157 2.7% –2.7% $9.7 –$0.9 

2025 $173 $157 2.7% –2.7% $9.8 –$0.9 

2026 $173 $157 2.7% –2.7% $9.8 –$0.9 

2027 $173 $157 2.7% –2.7% $9.9 –$0.9 

2028 $173 $157 2.7% –2.7% $9.9 –$0.9 

2029 $173 $157 2.7% –2.7% $10.0 –$0.9 

2030 $173 $157 2.7% –2.7% $10.1 –$0.9 

2031 $173 $157 2.7% –2.7% $10.1 –$0.9 

2032 $173 $157 2.7% –2.7% $10.2 –$1.0 

2033 $173 $157 2.7% –2.7% $10.3 –$1.0 

2034 $173 $157 2.7% –2.7% $10.3 –$1.0 

2035 $173 $157 2.7% –2.7% $10.4 –$1.0 

2036 $173 $157 2.7% –2.7% $10.5 –$1.0 

2037 $173 $157 2.7% –2.7% $10.5 –$1.0 

NPV (3%) $179.6 –$16.6 

NPV (7%) $108.8 –$10.0 

a Figures are in 2005 dollars. b Average price per engine is a weighted average price of engine by equipment type. 

9-93 
Final Regulatory Impact Analysis 

Table 9B-3: Impact on Marine SI Engine Market: 

51–100hp (Average Price per Engine = $9,100)a,b 

Marine SI Engine (51–100hp) 

Total Change in Engine 

Absolute Change in Change in Engineering Manufacturers 

Engineering Change in Price Quantity Costs Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $20 $18 0.2% –0.2% $1.5 $1.5 

2009 $20 $18 0.2% –0.2% $1.5 $1.5 

2010 $203 $188 2.1% –1.5% $15.5 $15.5 

2011 $203 $187 2.1% –1.7% $15.6 $15.6 

2012 $203 $185 2.0% –1.8% $15.7 $15.7 

2013 $203 $185 2.0% –1.8% $15.8 $15.8 

2014 $203 $185 2.0% –1.8% $15.9 $15.9 

2015 $162 $148 1.6% –1.5% $12.8 $12.8 

2016 $162 $148 1.6% –1.5% $12.9 $12.9 

2017 $162 $148 1.6% –1.5% $13.0 $13.0 

2018 $162 $148 1.6% –1.5% $13.1 $13.1 

2019 $162 $148 1.6% –1.5% $13.2 $13.2 

2020 $162 $148 1.6% –1.5% $13.3 $13.3 

2021 $162 $148 1.6% –1.5% $13.4 $13.4 

2022 $162 $148 1.6% –1.5% $13.4 $13.4 

2023 $162 $148 1.6% –1.5% $13.5 $13.5 

2024 $162 $148 1.6% –1.5% $13.6 $13.6 

2025 $162 $148 1.6% –1.5% $13.7 $13.7 

2026 $162 $148 1.6% –1.5% $13.8 $13.8 

2027 $162 $148 1.6% –1.5% $13.9 $13.9 

2028 $162 $148 1.6% –1.5% $14.0 $14.0 

2029 $162 $148 1.6% –1.5% $14.1 $14.1 

2030 $162 $148 1.6% –1.5% $14.2 $14.2 

2031 $162 $148 1.6% –1.5% $14.3 $14.3 

2032 $162 $148 1.6% –1.5% $14.3 $14.3 

2033 $162 $148 1.6% –1.5% $14.4 $14.4 

2034 $162 $148 1.6% –1.5% $14.5 $14.5 

2035 $162 $148 1.6% –1.5% $14.6 $14.6 

2036 $162 $148 1.6% –1.5% $14.7 $14.7 

2037 $162 $148 1.6% –1.5% $14.8 $14.8 

NPV (3%) $253.5 –$21.6 

NPV (7%) $153.8 –$13.0 

a Figures are in 2005 dollars. b Average price per engine is a weighted average price of engine by equipment type. 

9-94 
Economic Impact Analysis 

Table 9B-4: Impact on Marine SI Engine Market: 

101–175hp (Average Price per Engine =$12,700)a,b 

Marine SI Engine (101–175hp) 

Total Change in Engine 

Absolute Change in Change in Engineering Manufacturers 

Engineering Change in Price Quantity Costs Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $39 $36 0.3% –0.2% $2.6 –$0.2 

2009 $39 $36 0.3% –0.3% $2.6 –$0.2 

2010 $365 $338 2.7% –2.0% $24.7 –$1.8 

2011 $365 $336 2.6% –2.2% $24.9 –$2.0 

2012 $365 $333 2.6% –2.4% $25.1 –$2.2 

2013 $365 $333 2.6% –2.4% $25.3 –$2.2 

2014 $365 $333 2.6% –2.4% $25.5 –$2.2 

2015 $292 $266 2.1% –2.0% $20.5 –$1.9 

2016 $292 $266 2.1% –2.0% $20.7 –$1.8 

2017 $292 $266 2.1% –1.9% $20.8 –$1.8 

2018 $292 $266 2.1% –1.9% $20.9 –$1.8 

2019 $292 $266 2.1% –1.9% $21.1 –$1.8 

2020 $292 $266 2.1% –1.9% $21.2 –$1.9 

2021 $292 $266 2.1% –1.9% $21.4 –$1.9 

2022 $292 $266 2.1% –1.9% $21.5 –$1.9 

2023 $292 $266 2.1% –1.9% $21.7 –$1.9 

2024 $292 $266 2.1% –1.9% $21.8 –$1.9 

2025 $292 $266 2.1% –1.9% $21.9 –$1.9 

2026 $292 $266 2.1% –1.9% $22.1 –$1.9 

2027 $292 $266 2.1% –1.9% $22.2 –$1.9 

2028 $292 $266 2.1% –1.9% $22.4 –$1.9 

2029 $292 $266 2.1% –1.9% $22.5 –$2.0 

2030 $292 $266 2.1% –1.9% $22.7 –$2.0 

2031 $292 $266 2.1% –1.9% $22.8 –$2.0 

2032 $292 $266 2.1% –1.9% $23.0 –$2.0 

2033 $292 $266 2.1% –1.9% $23.1 –$2.0 

2034 $292 $266 2.1% –1.9% $23.2 –$2.0 

2035 $292 $266 2.1% –1.9% $23.4 –$2.0 

2036 $292 $266 2.1% –1.9% $23.5 –$2.0 

2037 $292 $266 2.1% –1.9% $23.7 –$2.1 

NPV (3%) $406.1 –$34.9 

NPV (7%) $246.7 –$21.1 

a Figures are in 2005 dollars. b Average price per engine is a weighted average price of engine by equipment type. 

9-95 
Final Regulatory Impact Analysis 

Table 9B-5: Impact on Marine SI Engine Market: 

176–300hp (Average Price per Engine =$17,600)a,b 

Marine SI Engine (176–300hp) 

Total Change in Engine 

Absolute Change in Change in Engineering Manufacturers 

Engineering Change in Price Quantity Costs Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $59 $55 0.3% –0.2% $5.4 –$0.4 

2009 $59 $54 0.3% –0.2% $5.5 –$0.4 

2010 $517 $480 2.7% –1.7% $48.3 –$3.4 

2011 $517 $477 2.7% –1.9% $48.6 –$3.7 

2012 $517 $474 2.7% –2.0% $49.0 –$4.0 

2013 $517 $474 2.7% –2.0% $49.3 –$4.1 

2014 $517 $474 2.7% –2.0% $49.7 –$4.1 

2015 $414 $378 2.1% –1.7% $40.0 –$3.4 

2016 $414 $379 2.2% –1.7% $40.3 –$3.4 

2017 $414 $379 2.2% –1.6% $40.6 –$3.4 

2018 $414 $379 2.2% –1.6% $40.9 –$3.4 

2019 $414 $379 2.2% –1.6% $41.2 –$3.4 

2020 $414 $379 2.2% –1.6% $41.4 –$3.5 

2021 $414 $379 2.2% –1.6% $41.7 –$3.5 

2022 $414 $379 2.2% –1.6% $42.0 –$3.5 

2023 $414 $379 2.2% –1.6% $42.3 –$3.5 

2024 $414 $379 2.2% –1.6% $42.6 –$3.5 

2025 $414 $379 2.2% –1.6% $42.8 –$3.6 

2026 $414 $379 2.2% –1.6% $43.1 –$3.6 

2027 $414 $379 2.2% –1.6% $43.4 –$3.6 

2028 $414 $379 2.2% –1.6% $43.7 –$3.6 

2029 $414 $379 2.2% –1.6% $44.0 –$3.7 

2030 $414 $379 2.2% –1.6% $44.2 –$3.7 

2031 $414 $379 2.2% –1.6% $44.5 –$3.7 

2032 $414 $379 2.2% –1.6% $44.8 –$3.7 

2033 $414 $379 2.2% –1.6% $45.1 –$3.8 

2034 $414 $379 2.2% –1.6% $45.4 –$3.8 

2035 $414 $379 2.2% –1.6% $45.7 –$3.8 

2036 $414 $379 2.2% –1.6% $45.9 –$3.8 

2037 $414 $379 2.2% –1.6% $46.2 –$3.9 

NPV (3%) $793.5 –$65.0 

NPV (7%) $482.1 –$39.2 

a Figures are in 2005 dollars. b Average price per engine is a weighted average price of engine by equipment type. 

9-96 
Economic Impact Analysis 

Table 9B-6: Impact on Marine SI Engine Market: 

300+ hp (Average Price per Engine = $22,000)a,b 

Marine SI Engine (300+ hp) 

Total Change in Engine 

Absolute Change in Change in Engineering Manufacturers 

Engineering Change in Price Quantity Costs Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $57 $54 0.2% –0.1% $2.1 –$0.1 

2009 $57 $54 0.2% –0.1% $2.1 –$0.1 

2010 $297 $283 1.3% –0.6% $11.1 –$0.5 

2011 $297 $280 1.3% –0.8% $11.2 –$0.6 

2012 $297 $276 1.3% –1.0% $11.3 –$0.8 

2013 $297 $276 1.3% –1.0% $11.4 –$0.8 

2014 $297 $276 1.3% –1.0% $11.5 –$0.8 

2015 $238 $220 1.0% –0.8% $9.2 –$0.7 

2016 $238 $220 1.0% –0.8% $9.3 –$0.7 

2017 $238 $221 1.0% –0.8% $9.4 –$0.7 

2018 $238 $221 1.0% –0.8% $9.4 –$0.7 

2019 $238 $221 1.0% –0.8% $9.5 –$0.7 

2020 $238 $221 1.0% –0.8% $9.6 –$0.7 

2021 $238 $221 1.0% –0.8% $9.6 –$0.7 

2022 $238 $221 1.0% –0.8% $9.7 –$0.7 

2023 $238 $221 1.0% –0.8% $9.8 –$0.7 

2024 $238 $221 1.0% –0.8% $9.8 –$0.7 

2025 $238 $221 1.0% –0.8% $9.9 –$0.7 

2026 $238 $221 1.0% –0.8% $10.0 –$0.7 

2027 $238 $221 1.0% –0.8% $10.0 –$0.7 

2028 $238 $221 1.0% –0.8% $10.1 –$0.7 

2029 $238 $221 1.0% –0.8% $10.1 –$0.7 

2030 $238 $221 1.0% –0.8% $10.2 –$0.7 

2031 $238 $221 1.0% –0.8% $10.3 –$0.7 

2032 $238 $221 1.0% –0.8% $10.3 –$0.8 

2033 $238 $221 1.0% –0.8% $10.4 –$0.8 

2034 $238 $221 1.0% –0.8% $10.5 –$0.8 

2035 $238 $221 1.0% –0.8% $10.5 –$0.8 

2036 $238 $221 1.0% –0.8% $10.6 –$0.8 

2037 $238 $221 1.0% –0.8% $10.7 –$0.8 

NPV (3%) $184.7 –$12.8 

NPV (7%) $112.8 –$7.7 

a Figures are in 2005 dollars. b Average price per engine is a weighted average price of engine by equipment type. 

9-97 
Final Regulatory Impact Analysis 

Table 9B-7: Impact on Marine Vessels Market: 

SD/I Recreational 175–300 hp (Average Price per Equipment = $32,356)a 

Marine Vessel (SD/I Recreational 175–300 hp) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $2 $33 0.1% –0.2% $0.1 –$0.6 

2009 $6 $35 0.1% –0.2% $0.2 –$0.6 

2010 $5 $205 0.6% –1.3% $0.2 –$3.6 

2011 $44 $230 0.7% –1.4% $1.5 –$4.1 

2012 $94 $261 0.8% –1.6% $3.2 –$4.7 

2013 $94 $261 0.8% –1.6% $3.2 –$4.7 

2014 $94 $261 0.8% –1.6% $3.3 –$4.8 

2015 $94 $220 0.7% –1.4% $3.3 –$4.0 

2016 $87 $216 0.7% –1.3% $3.0 –$4.0 

2017 $81 $212 0.7% –1.3% $2.8 –$3.9 

2018 $81 $212 0.7% –1.3% $2.9 –$4.0 

2019 $81 $212 0.7% –1.3% $2.9 –$4.0 

2020 $81 $212 0.7% –1.3% $2.9 –$4.0 

2021 $81 $212 0.7% –1.3% $2.9 –$4.1 

2022 $81 $212 0.7% –1.3% $2.9 –$4.1 

2023 $81 $212 0.7% –1.3% $3.0 –$4.1 

2024 $81 $212 0.7% –1.3% $3.0 –$4.1 

2025 $81 $212 0.7% –1.3% $3.0 –$4.2 

2026 $81 $212 0.7% –1.3% $3.0 –$4.2 

2027 $81 $212 0.7% –1.3% $3.0 –$4.2 

2028 $81 $212 0.7% –1.3% $3.1 –$4.2 

2029 $81 $212 0.7% –1.3% $3.1 –$4.3 

2030 $81 $212 0.7% –1.3% $3.1 –$4.3 

2031 $81 $212 0.7% –1.3% $3.1 –$4.3 

2032 $81 $212 0.7% –1.3% $3.1 –$4.4 

2033 $81 $212 0.7% –1.3% $3.2 –$4.4 

2034 $81 $212 0.7% –1.3% $3.2 –$4.4 

2035 $81 $212 0.7% –1.3% $3.2 –$4.4 

2036 $81 $212 0.7% –1.3% $3.2 –$4.5 

2037 $81 $212 0.7% –1.3% $3.2 –$4.5 

NPV (3%) $50.5 –$75.6 

NPV (7%) $29.2 –$45.6 

a Figures are in 2005 dollars. 

9-98 
Economic Impact Analysis 

Table 9B-8: Impact on Marine Vessels Market: 

SD/I Luxury 300+ hp (Average Price per Equipment = $205,658)a 

Marine Vessel (SD/I Luxury 300+ hp) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $2 $56 0.0% –0.1% $0.0 –$0.2 

2009 $10 $61 0.0% –0.1% $0.1 –$0.3 

2010 $8 $291 0.1% –0.3% $0.1 –$1.3 

2011 $108 $354 0.2% –0.3% $0.9 –$1.6 

2012 $236 $435 0.2% –0.4% $2.0 –$1.9 

2013 $236 $435 0.2% –0.4% $2.0 –$1.9 

2014 $236 $435 0.2% –0.4% $2.0 –$2.0 

2015 $236 $378 0.2% –0.4% $2.0 –$1.7 

2016 $216 $365 0.2% –0.4% $1.9 –$1.7 

2017 $206 $359 0.2% –0.3% $1.8 –$1.6 

2018 $206 $359 0.2% –0.3% $1.8 –$1.7 

2019 $206 $359 0.2% –0.3% $1.8 –$1.7 

2020 $206 $359 0.2% –0.3% $1.8 –$1.7 

2021 $206 $359 0.2% –0.3% $1.8 –$1.7 

2022 $206 $359 0.2% –0.3% $1.8 –$1.7 

2023 $206 $359 0.2% –0.3% $1.9 –$1.7 

2024 $206 $359 0.2% –0.3% $1.9 –$1.7 

2025 $206 $359 0.2% –0.3% $1.9 –$1.7 

2026 $206 $359 0.2% –0.3% $1.9 –$1.7 

2027 $206 $359 0.2% –0.3% $1.9 –$1.8 

2028 $206 $359 0.2% –0.3% $1.9 –$1.8 

2029 $206 $359 0.2% –0.3% $1.9 –$1.8 

2030 $206 $359 0.2% –0.3% $1.9 –$1.8 

2031 $206 $359 0.2% –0.3% $2.0 –$1.8 

2032 $206 $359 0.2% –0.3% $2.0 –$1.8 

2033 $206 $359 0.2% –0.3% $2.0 –$1.8 

2034 $206 $359 0.2% –0.3% $2.0 –$1.8 

2035 $206 $359 0.2% –0.3% $2.0 –$1.9 

2036 $206 $359 0.2% –0.3% $2.0 –$1.9 

2037 $206 $359 0.2% –0.3% $2.0 –$1.9 

NPV (3%) $31.3 –$31.1 

NPV (7%) $18.0 –$18.6 

a Figures are in 2005 dollars. 

9-99 
Final Regulatory Impact Analysis 

Table 9B-9: Impact on Marine Vessels Market: 

OB Recreational 50–100 hp (Average Price per Equipment = $21,561)a 

Marine Vessel (OB Recreational 50–100 hp) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $2 $16 0.1% –0.2% $0.1 $0.0 

2009 $10 $21 0.1% –0.2% $0.6 –$0.2 

2010 $9 $165 0.8% –1.5% $0.5 –$0.2 

2011 $35 $181 0.8% –1.7% $2.1 –$0.7 

2012 $62 $197 0.9% –1.8% $3.7 –$1.3 

2013 $62 $197 0.9% –1.8% $3.7 –$1.3 

2014 $62 $197 0.9% –1.8% $3.7 –$1.3 

2015 $62 $165 0.8% –1.5% $3.8 –$1.3 

2016 $56 $162 0.8% –1.5% $3.5 –$1.2 

2017 $50 $158 0.7% –1.5% $3.1 –$1.1 

2018 $50 $158 0.7% –1.5% $3.1 –$1.1 

2019 $50 $158 0.7% –1.5% $3.1 –$1.1 

2020 $50 $158 0.7% –1.5% $3.2 –$1.1 

2021 $50 $158 0.7% –1.5% $3.2 –$1.1 

2022 $50 $158 0.7% –1.5% $3.2 –$1.1 

2023 $50 $158 0.7% –1.5% $3.2 –$1.1 

2024 $50 $158 0.7% –1.5% $3.2 –$1.1 

2025 $50 $158 0.7% –1.5% $3.3 –$1.1 

2026 $50 $158 0.7% –1.5% $3.3 –$1.1 

2027 $50 $158 0.7% –1.5% $3.3 –$1.1 

2028 $50 $158 0.7% –1.5% $3.3 –$1.1 

2029 $50 $158 0.7% –1.5% $3.3 –$1.2 

2030 $50 $158 0.7% –1.5% $3.4 –$1.2 

2031 $50 $158 0.7% –1.5% $3.4 –$1.2 

2032 $50 $158 0.7% –1.5% $3.4 –$1.2 

2033 $50 $158 0.7% –1.5% $3.4 –$1.2 

2034 $50 $158 0.7% –1.5% $3.5 –$1.2 

2035 $50 $158 0.7% –1.5% $3.5 –$1.2 

2036 $50 $158 0.7% –1.5% $3.5 –$1.2 

2037 $50 $158 0.7% –1.5% $3.5 –$1.2 

NPV (3%) $56.6 –$19.5 

NPV (7%) $33.3 –$11.4 

a Figures are in 2005 dollars. 

9-100 
Economic Impact Analysis 

Table 9B-10: Impact on Marine Vessels Market: 

OB Luxury 175–300 hp (Average Price per Equipment = $104,562)a 

Marine Vessel (OB Luxury 175–300 hp) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $3 $98 0.1% –0.2% $0.0 –$0.2 

2009 $26 $111 0.1% –0.2% $0.1 –$0.2 

2010 $23 $1,009 1.0% –1.9% $0.1 –$1.9 

2011 $145 $1,079 1.0% –2.1% $0.5 –$2.0 

2012 $267 $1,150 1.1% –2.2% $0.9 –$2.1 

2013 $267 $1,150 1.1% –2.2% $1.0 –$2.2 

2014 $267 $1,150 1.1% –2.2% $1.0 –$2.2 

2015 $267 $951 0.9% –1.8% $1.0 –$1.8 

2016 $243 $937 0.9% –1.8% $0.9 –$1.8 

2017 $227 $928 0.9% –1.8% $0.8 –$1.8 

2018 $227 $928 0.9% –1.8% $0.8 –$1.8 

2019 $227 $928 0.9% –1.8% $0.8 –$1.8 

2020 $227 $928 0.9% –1.8% $0.8 –$1.8 

2021 $227 $928 0.9% –1.8% $0.9 –$1.8 

2022 $227 $928 0.9% –1.8% $0.9 –$1.9 

2023 $227 $928 0.9% –1.8% $0.9 –$1.9 

2024 $227 $928 0.9% –1.8% $0.9 –$1.9 

2025 $227 $928 0.9% –1.8% $0.9 –$1.9 

2026 $227 $928 0.9% –1.8% $0.9 –$1.9 

2027 $227 $928 0.9% –1.8% $0.9 –$1.9 

2028 $227 $928 0.9% –1.8% $0.9 –$1.9 

2029 $227 $928 0.9% –1.8% $0.9 –$1.9 

2030 $227 $928 0.9% –1.8% $0.9 –$2.0 

2031 $227 $928 0.9% –1.8% $0.9 –$2.0 

2032 $227 $928 0.9% –1.8% $0.9 –$2.0 

2033 $227 $928 0.9% –1.8% $0.9 –$2.0 

2034 $227 $928 0.9% –1.8% $0.9 –$2.0 

2035 $227 $928 0.9% –1.8% $0.9 –$2.0 

2036 $227 $928 0.9% –1.8% $0.9 –$2.0 

2037 $227 $928 0.9% –1.8% $0.9 –$2.0 

NPV (3%) $14.9 –$34.4 

NPV (7%) $8.7 –$20.8 

a Figures are in 2005 dollars. 

9-101 
Final Regulatory Impact Analysis 

Table 9B-11: Impact on Marine Vessels Market: 

PWC 100–175 hp (Average Price per Equipment = $9,982)a 

Marine Vessel (PWC 100–175 hp) 

Total 

Absolute Change Change in Engineering Change in Equipment 

Engineering Change in in Price Quantity Costs Manufacturers Surplus 

Year Cost/Unit Price (%) (%) (million $) (million $) 

2008 $35 $25 0.3% –0.5% $1.9 –$0.5 

2009 $53 $38 0.4% –0.8% $2.9 –$0.8 

2010 $103 $74 0.7% –1.5% $5.7 –$1.6 

2011 $96 $69 0.7% –1.4% $5.3 –$1.5 

2012 $96 $69 0.7% –1.4% $5.4 –$1.5 

2013 $96 $69 0.7% –1.4% $5.4 –$1.5 

2014 $96 $69 0.7% –1.4% $5.5 –$1.5 

2015 $79 $57 0.6% –1.1% $4.5 –$1.3 

2016 $79 $57 0.6% –1.1% $4.6 –$1.3 

2017 $79 $57 0.6% –1.1% $4.6 –$1.3 

2018 $79 $57 0.6% –1.1% $4.6 –$1.3 

2019 $79 $57 0.6% –1.1% $4.6 –$1.3 

2020 $79 $57 0.6% –1.1% $4.7 –$1.3 

2021 $79 $57 0.6% –1.1% $4.7 –$1.3 

2022 $79 $57 0.6% –1.1% $4.7 –$1.3 

2023 $79 $57 0.6% –1.1% $4.8 –$1.3 

2024 $79 $57 0.6% –1.1% $4.8 –$1.3 

2025 $79 $57 0.6% –1.1% $4.8 –$1.3 

2026 $79 $57 0.6% –1.1% $4.9 –$1.4 

2027 $79 $57 0.6% –1.1% $4.9 –$1.4 

2028 $79 $57 0.6% –1.1% $4.9 –$1.4 

2029 $79 $57 0.6% –1.1% $5.0 –$1.4 

2030 $79 $57 0.6% –1.1% $5.0 –$1.4 

2031 $79 $57 0.6% –1.1% $5.0 –$1.4 

2032 $79 $57 0.6% –1.1% $5.1 –$1.4 

2033 $79 $57 0.6% –1.1% $5.1 –$1.4 

2034 $79 $57 0.6% –1.1% $5.1 –$1.4 

2035 $79 $57 0.6% –1.1% $5.2 –$1.4 

2036 $79 $57 0.6% –1.1% $5.2 –$1.4 

2037 $79 $57 0.6% –1.1% $5.2 –$1.4 

NPV (3%) $92.7 –$25.6 

NPV (7%) $57.4 –$15.8 

a Figures are in 2005 dollars. 

9-102 
Economic Impact Analysis 

Appendix 9C: Time Series Projections of Social Cost 

This appendix provides a time series of the rule’s projected social costs for each year 

through 2037. Costs are presented in 2005 dollars. In addition, this appendix includes the net 

present values by stakeholder using social discount rates of 3 percent and 7 percent over the period 

of analysis. As a result, it illustrates how the choice of the discount rate determines the present 

value of the total social costs of the program. 

9-103 
Table 9C: Time Series Projection of Social Costs: 2008 to 2038 (Million $)a 

2008 2009 2010 2011 2012 2013 2014 2015 20

Consumer Surplus Change, Total –$46.3 –$109.2 –$224.9 –$272.1 –$372.8 –$376.1 –$380.2 –$349.8 –$3

Marine SI 

End users (households) –$13.2 –$15.8 –$113.2 –$120.0 –$128.2 –$129.1 –$130.0 –$108.5 –$1

Small SI 

End users (households) –$33.1 –$93.4 –$111.7 –$152.1 –$244.6 –$247.0 –$250.2 –$241.4 –$2

Producer Surplus Change, Total –$7.5 –$17.0 –$42.5 –$52.0 –$62.7 –$63.2 –$63.6 –$57.0 –$

Marine SI –$4.1 –$5.7 –$30.2 –$34.5 –$39.6 –$39.9 –$40.2 –$34.7 –$

Engine manufacturers –$1.0 –$1.3 –$8.8 –$9.5 –$10.3 –$10.4 –$10.5 –$8.8 –

Equipment manufacturers –$3.1 –$4.4 –$21.4 –$25.0 –$29.3 –$29.5 –$29.7 –$25.9 –$

Small SI –$3.4 –$11.3 –$12.3 –$17.5 –$23.1 –$23.3 –$23.4 –$22.3 –$

Engine manufacturers –$0.6 –$1.7 –$2.1 –$3.0 –$5.3 –$5.3 –$5.4 –$5.2 –

Equipment manufacturers –$2.9 –$9.6 –$10.2 –$14.5 –$17.8 –$18.0 –$18.1 –$17.2 –$

Fuel Savings $3.2 $8.1 $19.6 $43.9 $70.8 $95.7 $115.9 $134.3 $1

Consumer savings $3.9 $9.8 $23.8 $53.3 $86.0 $116.3 $140.8 $163.2 $1

Fuel $3.2 $8.1 $19.6 $43.9 $70.8 $95.7 $115.9 $134.3 $1

Tax $0.7 $1.7 $4.2 $9.4 $15.2 $20.6 $24.9 $28.9 $

Government revenue –$0.7 –$1.7 –$4.2 –$9.4 –$15.2 –$20.6 –$24.9 –$28.9 –$

Total Surplus Change –$50.6 –$118.1 –$247.8 –$280.2 –$364.7 –$343.6 –$327.9 –$272.5 –$2
Table 9C: Time Series Projection of Social Costs (Million $) (continued) 

2019 2020 2021 2022 2023 2024 2025 2026 20

Consumer Surplus Change, Total –$347.6 –$352.0 –$356.4 –$360.8 –$365.2 –$369.6 –$374.0 –$378.4 –$3

Marine SI 

End users (households) –$109.0 –$109.7 –$110.5 –$111.2 –$112.0 –$112.7 –$113.4 –$114.2 –$1

Small SI 

End users (households) –$238.6 –$242.3 –$245.9 –$249.6 –$253.2 –$256.9 –$260.5 –$264.2 –$2

Producer Surplus Change, Total –$56.2 –$56.7 –$57.3 –$57.9 –$58.5 –$59.0 –$59.6 –$60.2 –$

Marine SI –$34.0 –$34.2 –$34.4 –$34.7 –$34.9 –$35.1 –$35.4 –$35.6 –$

Engine manufacturers –$8.8 –$8.8 –$8.9 –$9.0 –$9.0 –$9.1 –$9.1 –$9.2 –

Equipment manufacturers –$25.2 –$25.4 –$25.5 –$25.7 –$25.9 –$26.0 –$26.2 –$26.4 –$

Small SI –$22.2 –$22.5 –$22.9 –$23.2 –$23.6 –$23.9 –$24.2 –$24.6 –$

Engine manufacturers –$5.1 –$5.1 –$5.2 –$5.3 –$5.4 –$5.4 –$5.5 –$5.6 –

Equipment manufacturers –$17.1 –$17.4 –$17.7 –$17.9 –$18.2 –$18.5 –$18.7 –$19.0 –$

Fuel Savings $190.4 $201.4 $211.1 $220.5 $229.3 $237.1 $244.2 $250.8 $2

Consumer savings $231.3 $244.6 $256.5 $267.9 $278.6 $288.1 $296.7 $304.7 $3

Fuel $190.4 $201.4 $211.1 $220.5 $229.3 $237.1 $244.2 $250.8 $2

Tax $40.9 $43.3 $45.4 $47.4 $49.3 $51.0 $52.5 $53.9 $

Government revenue –$40.9 –$43.3 –$45.4 –$47.4 –$49.3 –$51.0 –$52.5 –$53.9 –$

Total Surplus Change –$213.4 –$207.4 –$202.6 –$198.2 –$194.3 –$191.5 –$189.3 –$187.8 –$1
Table 9C: Time Series Projection of Social Costs (million $) (continued) 

2030 2031 2032 2033 2034 2035 2036 2037 

Consumer Surplus Change, Total –$396.1 –$400.5 –$404.9 –$409.4 –$413.8 –$418.2 –$422.6 –$427.1 

Marine SI 

End users (households) –$117.2 –$117.9 –$118.7 –$119.4 –$120.2 –$120.9 –$121.7 –$122.4 

Small SI 

End users (households) –$278.9 –$282.6 –$286.3 –$290.0 –$293.6 –$297.3 –$301.0 –$304.7 

Producer Surplus Change, Total –$62.5 –$63.0 –$63.6 –$64.2 –$64.8 –$65.3 –$65.9 –$66.5 

Marine SI –$36.5 –$36.8 –$37.0 –$37.2 –$37.5 –$37.7 –$37.9 –$38.2 

Engine manufacturers –$9.4 –$9.5 –$9.6 –$9.6 –$9.7 –$9.7 –$9.8 –$9.9 

Equipment manufacturers –$27.1 –$27.3 –$27.4 –$27.6 –$27.8 –$27.9 –$28.1 –$28.3 

Small SI –$26.0 –$26.3 –$26.6 –$27.0 –$27.3 –$27.7 –$28.0 –$28.4 

Engine manufacturers –$5.9 –$6.0 –$6.1 –$6.2 –$6.2 –$6.3 –$6.4 –$6.5 

Equipment manufacturers –$20.0 –$20.3 –$20.6 –$20.8 –$21.1 –$21.4 –$21.6 –$21.9 

Fuel Savings $273.0 $277.6 $281.9 $285.8 $289.6 $293.3 $296.7 $300.1 

Consumer savings $331.7 $337.3 $342.5 $347.3 $351.9 $356.3 $360.5 $364.6 

Fuel $273.0 $277.6 $281.9 $285.8 $289.6 $293.3 $296.7 $300.1 

Tax $58.7 $59.7 $60.6 $61.5 $62.3 $63.1 $63.8 $64.5 

Government revenue –$58.7 –$59.7 –$60.6 –$61.5 –$62.3 –$63.1 –$63.8 –$64.5 

Total Surplus Change –$185.5 –$185.9 –$186.7 –$187.7 –$188.9 –$190.3 –$191.8 –$193.5 

a Figures are in 2005 dollars. 
Economic Impact Analysis 

Appendix 9D: Overview of Model Equations and Calculation 

To develop the economic impact model, we use set of nonlinear supply and demand 

equations for the affected markets and transform them into a set of linear supply and demand 

equations. These resulting equations describe stakeholder production and consumption responses 

to policy-induced cost and price changes in each market. They also are used to specify the 

conditions for a new with-policy equilibrium. We describe these equations in more detail below. 

9D.1 Economic Model Equations 

Supply Equations 

First, we consider the formal definition of the elasticity of supply with respect to changes 

in own price: 

ε ≡ dQs / Qs . (9D.1) s dp / p 

Next, we can use “hat” notation to transform Eq. (C.1) to proportional changes and 

rearrange terms: 

Q

s = ε s p (9D.1a) 

where 

Q

s = percentage change in the quantity of market supply, 

gs = market elasticity of supply, and 

p = percentage change in market price. 

As Fullerton and Metcalf (2002) note, this approach takes the elasticity definition and turns it into 

a linear behavioral equation for each market. 

To introduce the direct impact of the regulatory program, we assume the direct per-unit 

compliance cost (c) leads to a proportional shift in the marginal cost of production. Under the 

assumption of competitive market (price equals marginal cost), we can approximate this shift at 

the initial equilibrium point as follows: 

^ c c

MC = = . (9D.2) MCo po 

The with-regulation supply response to price and cost changes can now be written as: 

∧

Q

s = ε s ( p − MC ) (9D.3) 

9-107 
Final Regulatory Impact Analysis 

For equipment producers, the supply response should also simultaneously accounts for 

changes in equilibrium input prices (engines). To do this, we modify Eq. (9D.2) as follows: 

^ c + α(∆ pengine ) c + α(∆ pengine ) MC = = MCo po (9D.3a) 

where )pengine is the equilibrium change in the engine price and " is the ratio of engines used per 

unit of equipment. For example, if one piece of equipment uses only one engine, then " = 1. This 

equation can accommodate other engine to equipment ratios by multiplying )peng by the 

appropriate engine-to-equipment ratio ("). 

Demand Equations 

Similar to supply, we can characterize equipment demand responses to price changes as: 

Q

d = η d p (9D.4) 

where 

Q

d = percentage change in the quantity of market demand, 

0d = market elasticity of demand, and 

p = percentage change in market price. 

In contrast to equipment demand, the demand for engines is a derived demand and is related to 

equipment supply decisions. In order to maintain a constant engine-to-equipment ratio, the 

demand for engines is specified as: 



d s Q engines = Q equipment (9D.5)

Market Equilibrium Conditions 

In response to the exogenous increase in equipment and engine production costs, 

stakeholder responses are completely characterized by represented in Eq. (9D.3)(equipment and 

engine supply), Eq. (9D.4) (equipment demand), and Eq. (9D.5)(engine demand). Next, we 

specify the relationship that must hold for markets to “clear”, that is, supply in each market equals 

demand. Given the equations specified above, the new equilibrium satisfies the condition that for 

each market, the proportional change in supply equals the proportional change in demand: 

Q

d = Qs (9D.6) 

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Economic Impact Analysis 

9D.2 Computing With-Regulation Equilibrium Conditions 

The choice of efficient model solution algorithms depends on several factors such as the 

number of markets included in the economic model, complexity of interactions between consumers 

and producers within these markets, and the software used to construct the model. To 

find the new market equilibrium prices and quantities, we used a solution algorithm that has 

proven very useful in “searching” for the equilibrium prices and quantities for partial equilibrium 

spreadsheet simulations with complicated relationships. We describe this approach in more detail 

below. 

9D.2.1 Conceptual Description of RTI’s Spreadsheet Model Solution Algorithm: 

PE_Walrasian_Auctioneer©2005 

The French economist Léon Walras proposed one early model of market price adjustment 

by using the following thought experiment. Suppose there is a hypothetical agent that facilitates 

market adjustment by playing the role of an “auctioneer.” He announces prices, collects 

information about supply and demand responses (without transactions actually taking place), and 

continues this process until market equilibrium is achieved. 

For example, consider the with-regulation supply and demand conditions at the withoutregulation equilibrium price (P) (see Figure 9D-1a). The auctioneer determines that the quantity 

demanded (A) exceeds the quantity supplied (B) at this price and calls out a new (higher) price 

(PN) based on the amount of excess demand. Consumers and producers make new consumption and 

production choices at this new price (i.e., they move along their respective demand and supply 

functions), and the auctioneer checks again to see if excess demand or supply exists. This process 

continues until P = P* (point C in Figure 9D-1a) is reached (i.e., excess demand is zero in the 

market). A similar analysis takes place when excess supply exists. The auctioneer calls out lower 

prices when the price is higher than the equilibrium price. 

Figure 9D-1a. Computing with Regulation Equilibrium 

$/Q 

P* 

Price P′ Increase 

P 

D 

Q/t 

S1 : W ith Regulation 

A B 

Unit Cost 

Increase 

S 0: W ithout 

Regulation 

C 

9-109 
Final Regulatory Impact Analysis 

The model uses a similar type of algorithm for determining with-regulation equilibria, and 

the process can be summarized by six recursive steps: 

1.	 Impose the control costs on affected supply segments, thereby affecting their supply 

decisions. 

2.	 Recalculate the market supply in each market. Excess demand currently exists. 

3.	 Determine the new prices via a price revision rule. We used a rule similar to the factor 

price revision rule described by Kimbell and Harrison (1986). Pi is the market price at 

iteration i, qd is the quantity demanded, and qs is the quantity supplied. The parameter 

z influences the magnitude of the price revision and the speed of convergence. The 

revision rule increases the price when excess demand exists, lowers the price when 

excess supply exists, and leaves the price unchanged when market demand equals 

market supply. The price adjustment is expressed as follows: 

⎛ qd ⎞ 

z 

Pi+1 = P1 • (9D.7) ⎜

⎝ ⎟ q ⎠ s 

4.	 Recalculate market supply with new prices. 

5.	 Compute market demand in each market. 

6.	 Compare supply and demand in each market. If equilibrium conditions are not 

satisfied, go to Step 3, resulting in a new set of market prices. Repeat until equilibrium 

conditions are satisfied (i.e., the ratio of supply and demand is arbitrarily close to one). 

When the ratio is appropriately close to one, the market-clearing condition of supply 

equals demand is satisfied. 

9D.2.2 Consumer and Producer Welfare Calculations 

The change in consumer surplus in the affected markets can be estimated using the 

following linear approximation method: 

)CS = – Q1 • )p + 0.5 • )Q • )p.	 (9D.8) 

As shown, higher market prices and reduced consumption lead to welfare losses for consumers. A 

geometric representation of this calculation is illustrated in Figure 9D-1b. 

For affected supply, the change in producer surplus can be estimated with the following 

equation: 

)PS = Q1 • ()p – c) – 0.5 • )Q • ()p – c). (9D.9) 

Increased regulatory costs and output declines have a negative effect on producer surplus, because 

the net price change ()p – c) is negative. However, these losses are mitigated, to some degree, as a 

result of higher market prices. A geometric representation of this calculation is illustrated in Figure 

9D-1b. 

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Economic Impact Analysis 

) consumer surplus =–[fghd + dhc] 

) producer surplus =[fghd – aehb] – bdc 

) total surplus =–[aehb + dhc + bdc] 

Figure 9D-1b. Welfare Calculations 

Q1 Q0 Output 

P1 

P0 

h 

c 

a 

$ 

g 

e 

f d

Price 

Increase 

Unit Cost Increase 

S1: With Regulation 

S0: Without Regulation 

b 

9-111 
Final Regulatory Impact Analysis 

Appendix 9E: Elasticity Parameters for Economic Impact Modeling 

The Economic Impact Model (EIM) relies on elasticity parameters to estimate the 

behavioral response of consumers and producers to the regulation and its associated social costs. 

To operationalize the market model, supply and demand elasticities are needed to represent the 

behavioral adjustments that are likely to be made by market participants. The following parameters 

are needed: 

• supply and demand elasticities for Marine SI equipment markets 

• supply and demand elasticities for Small SI equipment markets 

• supply elasticities for Marine SI engine markets 

• supply elasticities for Small SI engine markets 

Note that demand elasticities for the Marine SI and Small SI engine markets are not 

estimated because they are derived internally in the model. They are a function of changes in 

output levels in the equipment markets. 

Tables 9E-1 and 9E-2 contain the demand and supply elasticities used to estimate the 

economic impact of the rule. Two methods were used to obtain the supply and demand elasticities 

used in the EIM. First, the professional literature was surveyed to identify elasticity estimates used 

in published studies. Second, when literature estimates were not available for specific markets, 

established econometric techniques were used to estimate supply and demand elasticity parameters 

directly. Since very few studies have been identified to quantify elasticities for Small SI and 

Marine SI markets in the literature survey, the supply and demand elasticities for all of the 

equipment and engine markets were estimated econometrically. 

This appendix describes the methods used to estimate demand and supply elasticities for 

Marine SI and Small SI engines and equipment markets and presents the data sources and the 

regression results obtained from applying those methods. 

Finally, it should be noted that these elasticities reflect intermediate run behavioral 

changes. In the long run, supply and demand are expected to be more elastic since more substitutes 

may become available. 

9-112 
Economic Impact Analysis 

Table 9E-1: Summary of Market Supply Elasticities Used in the Market Model 

Markets Estimate Source	 Method Input Data Summary 

Recreational 

Marine 

All vessel types 3.8 EPA econometric 

except PWC estimate 

Table 9E-4 

PWC 5.2	 EPA econometric 

estimate 

Table 9E-5 

Small SI 

All lawn and 10.0 EPA econometric 

garden estimate 

equipment Table 9E-6 

Gensets/welders 8.8	 EPA econometric 

estimate 

Table 9E-7 

All Engines 9.5	 EPA econometric 

estimate 

Table 9E-3 

Cobb-Douglas production 

function 

Cobb-Douglas production 

function 

Cobb-Douglas production 

function 

Cobb-Douglas production 

function 

Cobb-Douglas production 

function 

Census of Manufacture, 

US Census Bureau; five 

years between 1972 and 

1997; NAICS 336612 

Census of Manufacture, 

US Census Bureau; five 

years between 1972 and 

1997; NAICS 336999 

Census of Manufacture, 

US Census Bureau; five 

years between 1972 and 

1997; NAICS 333112 

Census of Manufacture, 

US Census Bureau; five 

years between 1972 and 

1997; NAICS 335312 

Census of Manufacture, 

US Census Bureau; five 

years between 1972 and 

1997; NAICS 333618 

9-113 
Final Regulatory Impact Analysis 

Table 9E-2: Summary of Market Demand Elasticities Used in the Market Model 

Primary Input Data 

Market Estimate Source Method Summary 

Equipment 

All recreational !2.0 EPA econometric Simultaneous Bartlesman et al.(2000); 

marine (including estimate equation (3SLS) Manufacturing Industry Data 

PWC) Table 9E-8 from US Census Bureau:; 

1958–1996; SIC 3732 

Lawnmowers !0.2	 EPA econometric estimate Simultaneous 

Table 9E-9, equation (3SLS) 

Column 2 

Lawn and garden –1.0 EPA econometric estimate Simultaneous 

tractors Table 9E-9, equation (2SLS) 

Column 5 

Pumps/compressors/ –1.0a EPA econometric estimate Simultaneous 

pressure washers, Table 9E-9, equation (2SLS) 

snowblowers Column 5 

Agriculture, –1.0a EPA econometric estimate Simultaneous 

construction, general Table 9E-9, equation (2SLS) 

industrial Column 5 

Other lawn and –0.9b EPA econometric estimate Simultaneous 

garden Table 9E-9, equation (2SLS) 

Column 3 

AIR/NERA (2003); 

1973–2002 

U.S. Census Bureau, Current 

Industrial Reports, MA333A 

2000 and selected previous 

years; 1980–1997 

U.S. Census Bureau, Current 

Industrial Reports, MA333A 

2000 and selected previous 

years; 1980–1997 

U.S. Census Bureau, Current 

Industrial Reports, MA333A 

2000 and selected previous 

years; 1980–1997 

U.S. Census Bureau, Current 

Industrial Reports, MA333A 

2000 and selected previous 

years; 1980–1997 

All handheld lawn 

and garden 

equipment 

–1.9 EPA econometric estimate 

Table 9E-9, 

Column 4 

Simultaneous 

equation (2SLS) 

U.S. Census Bureau, Current 

Industrial Reports, MA333A 

2000 and selected years; 

1980–1997 

Gensets/welders 

Class 1 

–1.4 EPA econometric 

estimate 

Table 9E-10, 

Column 2 

Simultaneous 

equation (3SLS) 

U.S. Census Bureau, Current 

Industrial Reports, MA335H 

2000 and selected years; 

1980–1997 

Gensets/welders 

Class 2 

–1.1 EPA econometric 

estimate 

Table 9E-10, 

Column 3 

Simultaneous 

equation (3SLS) 

U.S. Census Bureau, Current 

Industrial Reports, MA335H 

2000 and selected years; 

1980–1997 

All Engines Derived demand NA 

a Uses econometric estimate for lawn and garden tractors. b Uses econometric estimate for commercial mowers. 

9-114 
Economic Impact Analysis 

9E.1 Supply Elasticities 

We use a two-step approach to estimate the price elasticity of supply14. In the first step, we 

estimate an industry production function by using the regression model. In the second step, we 

calculate the supply elasticity by the parameters estimated in the estimated production function. 

This section discusses the regression model used to estimate the industry production function, data 

sources used for the regression, and estimated results for supply elasticities. The economics theory 

on the relationship between the supply elasticity and the production function is discussed in 

Appendix 9F. 

In economics, the production function is defined as the relationship between inputs and 

outputs of the production process. In this case, we assume that Small SI and Marine SI 

manufacturers follow the Cobb-Douglas production function with a stochastic error term Ui t -N(0, 

F2), recognizing that we have observations on plant i at time t 

" " " Qi t = At

 (Ki t) K (Li t) L (Mi t) M ei t

U (9E.1) 

where 

Qi t = total value of shipment on plant i at time t, 

Ki t = total capital stock, including both structure and equipment, on plant i at time t, 

Li t = total plant hours on plant i at time t, and 

Mit = cost of materials on plant i at time t. 

This equation can be written in linear form by taking the natural logarithms of each side of the 

equation. The parameters of this model, "K, "L, "M, can then be estimated using linear regression 

techniques: 

ln Qi t = ln At + "K ln Ki t + "L ln Li t + "M ln Mi t + Ui t (E9.2) 

Under the assumptions of a competitive market, the elasticity of supply with respect to the 

price of the final product can be expressed in terms of the parameters of the production function:15 

Supply Elasticity = ("L + "M ) / (1 – "L – "M). (9E.3) 

Our main regressions were carried out imposing the constant returns to scale assumption 

("K+"L+"M=1). We also tested regressions that did not constrain the three " parameters, and 

obtained very similar estimates for the parameters. The estimated returns to scale, given by the 

sum of the three " parameters, ranges from 1.01 to 1.03, supporting the assumption of constant 

returns. We estimate these regressions with and without including the dummies for single-plant 

firm and large plant. Table 9E-3 to Table 9E-7 present the estimated production function 

14 Please refer to Supply Elasticity Estimation Report, Li, Chi. May 19, 2008. Memorandum to Docket 

EPA-HQ-OAR-2004-0008. 

15 Appendix 9F provides the derivation of this result. 

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Final Regulatory Impact Analysis 

coefficients for the five industries including the dummies for single-plant firm and large plant. 

9E.1.1 Data Sets 

The data used to estimate these elasticities comes from Census of Manufactures, conducted 

by the Census Bureau every five years between 1972 and 1997. We had access to the plant-level 

data at the Boston Census Research Data Center, and gathered data for all plants that were 

identified as belonging to the five industries being studied. The Census data provided us with 

information on output as measured by TVS (Plant’s Total Value of Shipments), employment as 

measured by PH (Total Plant Hours), materials as measured by CM (Cost of Materials), and 

capital stock as measured by CAP (Total Capital Stock, including both Structure and Equipment) -

the capital stock data are only available through 1997, which is why we do not include 2002 

Census of Manufactures data in our analysis. 

Based on comments from reviewers of an earlier supply elasticity analysis done for three 

other industries, we added two additional variables to the regression analysis, to control for 

possible differences across plants in their productivity levels. SINGLE is a dummy variable, 

indicating that the plant’s firm owns no other manufacturing plants (a single-plant firm). BIG is a 

dummy variable, indicating that this plant has a number of employees larger than the median value 

for all other plants in this industry (approximately 50% of the plants in an industry should have 

BIG=1). 

The data were examined in detail to identify outliers, measured in terms of unusual ratios 

between the values (e.g. unusually high or low shipments per worker hour, relative to the other 

plants in the industry) or unusual swings from one observation to the next. Those cases were then 

adjusted, based on their values in surrounding years or on the ratios between variables for other 

plants in the same industry, to avoid biasing the results while retaining all observations for the 

analysis. 

One potential complication in working with the Census of Manufactures over this time 

period is the considerable change in industry definitions in 1997, when the Census Bureau shifted 

from SIC (Standard Industry Classification) codes to NAICS (North American Industry 

Classification System) codes. For these five industries there were some definitional concerns, but 

we were able to solve them reasonably accurately using a combination of SIC and NAICS industry 

codes and detailed product codes. 

9E.1.2 Results of Supply Elasticity Estimation 

By pooling data at establishment or plant level on selected years, we applied ordinary least 

square (OLS) procedure to estimate Eq. (9E.2) with two additional dummy variables. As shown in 

Tables 9E-3 through 9E-7, supply elasticity estimates for Small SI products range from 3.76 (Boat 

Building) to 9.96 (Lawn & Garden Equipment). 

9-116 
Economic Impact Analysis 

Table 9E-3: Gasoline Engines: NAICS 333618 (SIC 3519) Internal Combustion Engines, Not 

Elsewhere Classified. 

Number of Observations = 1454 

Root Mean Square Error = 0.316 

Supply Elasticity = 9.46 

Variable Estimated Coefficients t-statistic 

intercept 1.930 22.3 

SINGLE -0.120 - 4.4 

BIG 0.059 2.1 

ln K 0.096 4.6 

ln L 0.284 13.1 

ln M 0.621 27.0 

Table 9E-4: Gasoline-Powered Boats: NAICS 336612 (SIC 3732) Boat Building and Repairing. 

Number of Observations = 10521 

Root Mean Square Error = 0.239 

Supply Elasticity = 3.76 

Variable Estimated Coefficients t-statistic 

intercept 1.201 43.7 

SINGLE -0.045 -4.0 

BIG 0.113 18.6 

ln K 0.210 14.4 

ln L 0.141 15.8 

ln M 0.650 45.3 

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Final Regulatory Impact Analysis 

Table 9E-5: PWCs, ATVs, Snowmobiles: NAICS 336999 (SIC 3799) Transportation Equipment, 

Not Elsewhere Classified. 

Number of Observations = 2326 

Total R-square = 0.237 

Supply Elasticity = 5.20 

Variable Estimated Coefficients t-statistic 

intercept 1.323 13.9 

SINGLE -0.069 -3.1 

BIG 0.072 7.0 

ln K 0.161 7.0 

ln L 0.184 9.9 

ln M 0.654 19.2 

Table 9E-6: Small Handheld/Nonhandheld: NAICS 333112 (SIC 3524) Lawn and Garden Tractors 

and Home Lawn and Garden Equipment. 

Number of Observations = 839 

Root Mean Square Error = 0.232 

Supply Elasticity = 9.96 

Variable Estimated Coefficients t-statistic 

intercept 1.162 12.3 

SINGLE -0.012 -0.5 

BIG 0.033 1.3 

ln K 0.091 4.5 

ln L 0.156 7.3 

ln M 0.753 23.4 

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Economic Impact Analysis 

Table 9E-7: Gensets and Marine Generators: NAICS 335312 (SIC 3621) Motors and Generators. 

Number of Observations = 2681 

Root Mean Square Error = 0.288 

Supply Elasticity = 8.79 

Variable Estimated Coefficients t-statistic 

intercept 1.812 30.8 

SINGLE -0.096 -5.3 

BIG -0.041 -2.3 

ln K 0.102 7.3 

ln L 0.242 15.4 

ln M 0.655 33.7 

9-119 
Final Regulatory Impact Analysis 

9E.2 Demand Elasticities 

To obtain demand elasticity parameters, we estimated a simultaneous system of demand 

and supply equations using instrumental variables methodology by either two-stage least squares 

(2SLS) or three-stage least squares (3SLS) regression. This type of partial equilibrium market 

supply/demand model is specified as a system of interdependent equations in which the price and 

output of a product are simultaneously determined by the interaction of producers and consumers 

in the market. In simultaneous equation models, where variables in one equation feed back into 

variables in another equation, the error terms are correlated with the endogenous variables (price 

and output). Use of a single-equation ordinary least squares (OLS) estimation of individual 

equations will lead to biased and inconsistent parameter estimates because it does not account for 

the correlation of the error term with the endogenous variables. In 2SLS or 3SLS, however, each 

equation is identified through the inclusion of exogenous variables as instruments that control for 

shifts in the supply and demand curves over time. 

Exogenous variables influencing the demand for gasoline-powered boats and Small SI 

equipment include measures of general economic activity (per capita household or disposable 

income, number of households or housing starts). Exogenous variables influencing the cost of 

production and supply of boats and Small SI equipment include changes in prices of key inputs 

like labor and raw materials. 

The supply/demand system for gasoline powered equipment can be defined as follows: 

Qt

d = f(Pt

,Zt) + ut (9E.4) 

Qt

s = g(Pt

,Wt) + vt (9E.5) 

Qt

d = Qts (9E.6) 

Eq. (9E.4) shows quantity demanded as a function of price, Pt; a vector of demand shifters, Zt (e.g., 

measures of economic activity); and an error term, ut. Eq. (9E.5) represents quantity supplied as a 

function of price and a vector of supply shifters, Wt (e.g., input prices), and an error term, vt, while 

Eq. (9E.6) specifies the equilibrium condition that quantity supplied equals quantity demanded, 

creating a system of three equations with three endogenous variables. The interaction of the 

specified market forces solves this system, generating equilibrium values for the variables Pt

*

 and 

Qt

*

 = Qt

d* = Qts*. 

To generate demand and supply elasticity estimates simultaneously, we used 2SLS and/or 

3SLS procedures. For the 2SLS estimates, observed price is regressed against the exogenous 

instruments (i.e., the supply and demand “shifter” variables). The fitted (or predicted) values for 

the price variable are then employed as observations of the right-hand side price variable in the 

supply and demand equations. In the second stage, the 2SLS estimators are generated by running 

OLS on these calculated instrumental variables. Also, the 2SLS estimates are used to estimate 

errors in the structural equations, which then can be used to estimate the variance-covariance 

matrix of the structural equations' errors. For the 3SLS estimates, this information is used at the 

third stage to perform a generalized least squares (GLS) estimation of a single large equation 

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Economic Impact Analysis 

composed from the individual structural equations. If this process is done with all variables 

expressed in natural logarithms, the coefficient on the price variable in the demand equation yields 

an estimate of the constant elasticity of demand. 

9E.2.1 Demand Equation Estimation 

Demand equations were estimated using a general specification where the quantity of boats 

or Small SI equipment consumed is expressed as a function of price, number of households or 

housing starts, per capita household or disposable income, and a time trend. Trends were included 

as a general way to model the effects of changes in tastes and preferences. All price and income 

variables were deflated by the implicit gross domestic product (GDP) deflator. The endogenous 

variables in the equations are unit sales and own-price. The exogenous variables include the 

household and income variables and the time trend. The list of instruments includes these 

exogenous variables and supply factors influencing the price of the product: wages and a producer 

price index for material inputs. 

9E.2.2 Data Sets 

The National Bureau of Economic Research (NBER) data discussed in the supply elasticity 

section of the analysis plan ( RTI, 2005) contain data on production quantities, price indices, and 

suitable instruments to inform a demand analysis for recreational boats (SIC 3732). In its Current 

Industrial Reports (CIR) series, the U.S. Census Bureau produces an annual summary of the 

production of motors and generators and a summary of production of several types of lawn and 

garden equipment; both of these reports include the number of units manufactured and the value of 

production (U.S. Census Bureau, 1998; 2000). For the walk-behind lawnmowers regression, we 

used several data series reported in a study by Air Improvement Resource, Inc., and National 

Economic Research Associates (AIR/NERA, 2003). The U.S. Census Bureau publishes historical 

data on household income and housing starts (U.S. Census Bureau, 2002; 2004), and we collected 

price, wage, and material cost indexes from the Bureau of Labor Statistics (BLS) (BLS, 

2004a,b,c,d,e). Lastly, we obtained an implicit GDP price deflator from the U.S. Bureau of 

Economic Analysis (BEA) (BEA, 2004). The following variables from these sources were used in 

the regression: 

C unit sales of boats (Bartlesman et al., 2000), 

C price index for boats (Bartlesman et al., 2000), 

C lawn and garden equipment units produced (U.S. Census Bureau, AIR/NERA), 

C lawn and garden equipment value of production (U.S. Census Bureau), 

C producer price index for walk-behind lawnmowers (BLS), 

C households (U.S. Census Bureau), 

C housing starts (U.S. Census Bureau), 

C per capita income and population (U.S. Census Bureau, 2002; BEA, 2004), 

C average hourly earnings for production workers (BLS; Bartlesman et al., 2000), 

C price index for plastic and other materials and engines (BLS; Bartlesman et al., 2000), 

and GDP deflator (BEA). 

Some care was needed in using the time series from the CIR data set. Occasional changes 

9-121 
Final Regulatory Impact Analysis 

in category definition and the Census Bureau’s need to suppress some data to maintain 

confidentiality created difficulties in constructing consistent data series over the 2-decade time 

period. Nonetheless, we were able to assemble the following series: commercial nonriding 

mowers, commercial riding mowers, consumer lawn mowers, tillers and two-wheel tractors, snow 

throwers, edgers and trimmers, vacuums and blowers, and lawn and garden tractors. Statistically 

significant parameter estimates were obtained for commercial nonriding mowers, tillers/two-wheel 

tractors, edgers/trimmers, and lawn and garden tractors. 

We were not able to obtain a useful elasticity estimate for consumer lawn mowers using 

CIR data, perhaps because of aggregation biases in that category of the CIR data set. Because 

consumer lawn mowers are a critical segment of the entire Small SI sector, we used an alternate 

data set for our demand elasticity estimate. The data AIR/NERA used in their recent study proved 

very useful in this regard (AIR/NERA, 2003). In that study, the authors used a single-equation 

OLS regression to obtain a demand elasticity parameter, a procedure that RTI believes to be 

inadequate because the market process simultaneously determines price and quantity in the 

demand equation. However, using the same data series cited by AIR/NERA supplemented by data 

collected by RTI, we were able to obtain a reasonable estimate using the 3SLS regression 

described above. 

9E.2.3 Results of Demand Elasticity Estimation 

In this section, we present regression results used in the EIA. Table 9E-8 shows the 

parameter estimate for the marine sector, which is –2.0. Although the methodology and data sets 

are quite different, this result is consistent with the ones obtained by Raboy (1987) in his study 

almost 20 years ago. 

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Economic Impact Analysis 

Table 9E-8: Results of Econometric Estimation of Boat Demand Equation: 1958 to 1996 

Recreational Boats—SIC 3732 

Dependent Variable—Regression	 Unit Sales per Capita 

Intercept –27.9 

(–10.3) 

Price –2.0 

(–2.04) 

Disposable income per capita	 1.83 

(5.85) 

Trend –0.19 

(–2.15) 

Adjusted R2 0.81 

Observations (years) 39 

(1958–1996) 

Notes: 1.	 Numbers in parentheses are t-ratios (coefficient estimate divided by its standard error) 

(except for the year ranges in the last row of the table). 

2. All exogenous and endogenous variables are in natural log. 

In Table 9E-9, we present demand elasticity results for Small SI equipment. Our estimate 

for walk-behind lawnmowers is –0.2 (inelastic). The value obtained for other nonhandheld 

categories such as commercial nonriding mowers and lawn and garden tractors is higher at (–0.9, 

–1.0). In contrast, the demand estimate for edgers/trimmers is elastic (–1.9), suggesting that 

consumers are more willing to forego purchases of these items at higher prices. The 

edgers/trimmers’ value was used for all handheld equipment. Results for generators, which range 

from –1.1 to –1.4, are shown in Table 9E-10. 

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Final Regulatory Impact Analysis 

Table 9E-9: Results of Econometric Estimation of Small SI Demand Equations: 

1980 to 1997 (1973–2002 for Consumer Mowers) 

Dependent 

Variable— 

Regression 

Consumer WalkBehind Mowers 

Units Sold per 

Household 

Commercial 

Mowers 

Units Produced 

Edgers and 

Trimmers 

Units Produced 

Lawn and 

Garden Tractors 

Units Produced 

Method 3SLS 2SLS 2SLS 2SLS 

Intercept –0.64 

(–2.71) 

–35.19 

(–4.41) 

–4.69 

(–0.63) 

–7.22 

(–1.46) 

Price –0.2 

(–3.73) 

–0.9 

(–2.74) 

–1.9 

(–6.05) 

–1.0 

(–2.29) 

Per capita income — 4.8 

(5.76) 

1.47 

(1.79) 

2.2 

(4.36) 

Housing starts per HH (1 

lag) 

0.23 

(4.71) 

— — — 

Trend — –0.20 

(–1.58) 

0.32 

(2.52) 

0.02 

(0.26) 

Adjusted or system 

weighted R2 

0.547 0.663 0.877 0.939 

Observations (years) 29 

(1973–2002) 

18 

(1980–97) 

18 

(1980–97) 

18 

(1980–97) 

Notes: 1.	 Numbers in parentheses are t-ratios (coefficient estimate divided by its standard error) (except for the 

year ranges in the last row of the table). 

2. All exogenous and endogenous variables are in natural log. 

3. For lawnmowers, the income variable is actually per capita disposable income. 

9-124 
Economic Impact Analysis 

Table 9E-10: Results of Econometric Estimation of Gasoline-Powered Generators 

Demand Equations: 1973 to 1998 

Units Produced 

Dependent Variable-Regression Small Generators (<5kW) Large Generators (>15kW) 

Intercept 16.4 

(2.64) 

–14.3 

(–2.48) 

Price –1.4 

(–3.64) 

–1.1 

(–8.59) 

Per capita income –0.46 

(–0.71) 

2.7 

(4.34) 

Trend –0.02 

(–0.51) 

–0.16 

(–1.53) 

Adjusted R2 0.609 0.723 

Observations (years) 26 

(1973–1998) 

26 

(1973–1998) 

Notes: 1.	 Numbers in parentheses are t-ratios (coefficient estimate divided by its standard error) (except for the 

year ranges in the last row of the table). 

2. All exogenous and endogenous variables are in natural log. 

9-125 
Final Regulatory Impact Analysis 

Appendix 9F: Derivation of Supply Elasticity 

In economics, a production function is used to describe the relationship between inputs and 

outputs of the production process. The production function in general is defined as follows 

Qs = f (L, K, M, t) 

Qs = the quantity of the outputs supplied 

L = the labor input or the number of labor hours 

K = real capital stock or real capital consumed in the production 

M = the material inputs 

t = a time trend variable to reflect technology changes 

In the competitive market, market forces constrain firms to produce at the cost minimizing 

output level. Cost minimization allows for the duality mapping of a firm’s technology 

(summarized by the firm’s production function) to the firm’s economic behavior (summarized by 

the firm’s cost function). The total cost function of an industry in the short term follows: 

TC = h( C, K, t, Qs

 ) 

where TC is the total cost of production, C is the variable cost of production (such as the cost of 

materials and labor), and the other variables have previous defined. This approach assumes that 

capital stock is fixed, or a sunk cost of production. This assumption is consistent with the goal of 

the modeling post-control market changes likely to occur. Firms facing final regulatory emission 

controls will consider embedded capital stock as a fixed or sunk cost in economic decision 

making. Differentiating the total cost function with respect to Qs derives the marginal cost 

function: 

MC = h’ ( C, K, t, Qs ) 

where MC is the marginal cost of production and all other variables have been previously defined. 

Profit maximizing competitive firms will choose to produce the quantity of output that 

equate the market price (P) to the marginal cost of the production (MC). Setting the price equal to 

the preceding marginal cost function and solving for Qs

 yields the following implied supply 

function: 

Qs

 = S (P, PL , PM,, K, t, ) 

where P is the market price of the products, PL is the price of the labor, PM is the price of 

materials, and all other variables have been previously defined. 

To illustrates how the supply elasticity used in Appendix 9E can be expressed in terms of 

the parameters of the production function (Equation 9E.3), we assume that production function is 

represented by a Cobb-Douglas function with only two inputs (capital [K] and labor [L]) with a 

9-126 
Economic Impact Analysis 

constant return to scale, 

Q = L" K1–" (9F.1) 

where Q = output, L = labor input, and K = capital input. The cost function is written as 

TC = wL + rK (9F.2) 

where w = wage rate or unit labor cost, r = interest cost or unit capital cost. From equation (9F.1), 

L can be written as,

 L = Q 1/ " K (" -1 )/ " (9F.3) 

Substituting L in the cost function with equation (9F.3), 

TC = wL + rK = w {Q 1/ " K (" -1 )/ " } + r K 

Differentiating cost function with respect to Q, the marginal cost function is 

MC = w { (1/ ") Q (1/ ") -1 K (" -1 )/ " } = (w / ") Q (1 - " ) / " K (" -1 )/ "

According to the competitive condition, P = MC, that is 

MC = (w / ") Q (1 - " ) / " K (" -1 )/ " = P 

To rearrange the above equation, Q is expressed by a function of P and K,

 Q = {(" /w) P K (1-" ) / " } " / (1–") 

We have 

Q = (" /w)" / (1–") P " / (1–") K (9F.4) 

Taking log function on both sides, 

ln Q = "/(1-") ln ( "/w)+ "/(1-") ln P + ln K (9F.5) 

The price elasticity of supply can be written as 

Supply elasticity = M ln Q/ M ln P = " /(1- " ) (9F.6) 

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Final Regulatory Impact Analysis 

Appendix 9G: Initial Market Equilibrium - Price Forecasts 

The EIM analysis begins with current market conditions: equilibrium supply and demand. 

To estimate the economic impact of a regulation, standard practice uses projected market 

equilibrium (time series of prices and quantities) as the baseline and evaluates market changes 

from this projected baseline. Consequently, it is necessary to forecast equilibrium prices and 

quantities for future years. 

Equilibrium price forecasts typically use one of two approaches (EPA 1999, p 5-25). The 

first assumes a constant (real) price of goods and services over time. The second models a specific 

time series where prices may change over time due to exogenous factors. 

In the absence of shocks to the economy or the supply of raw materials, economic theory 

suggests that the equilibrium market price for goods and services should remain constant over 

time. As shown in Figure 7G-1, demand grows over time, in the long run, capacity will also grow 

as existing firms expand or new firms enter the market and eliminate any excess profits. This 

produces a flat long run supply curve. Note that in the short to medium run time frame the supply 

curve has a positive slope due to limitations in how quickly firms can react. 

Figure 9G-1. Prices and Quantities in Long Run Market Equilibrium 

9-128 
Economic Impact Analysis 

If capacity is constrained (preventing the outward shift of the baseline supply curve) or if 

the price of production inputs increase (shifting the baseline supply curve upward over time), then 

prices may trend upward reflecting that either the growth in demand is exceeding supply or the 

commodity is becoming more expensive to produce. 

It is very difficult to develop forecasts events (such as those mentioned above) that 

influence long run prices. As a result, the approach used in this analysis is to use a constant 2005 

observed price. 

9-129 
Final Regulatory Impact Analysis 

Appendix 9H: Sensitivity Analysis 

The Economic Impact Analysis presented in this Chapter 9 is based on the Economic 

Impact Model (EIM) developed for this analysis. The EIM reflects certain assumptions about 

behavioral responses (modeled by supply and demand elasticities), and what the baseline 

equipment prices are used in the model. This appendix presents a sensitivity analysis for 

alternatives in the model. Three scenarios are examined: 

# Scenario 1: alternative market supply and demand elasticity parameters 

# Scenario 2: alternative baseline prices for lawn mower and tractor 

# Scenario 3: alternative gasoline price for social costs 

# Scenario 4: change in consumer’s behavior due this rule 

The results of these sensitivity analyses are presented below. The results from Scenario 1 

are presented for 2014 (the highest cost year) only with 2005$. The results for the Small SI and 

Marine SI engine and equipment markets do not include the fuel savings. Instead, fuel savings are 

added into the total social costs as a separate item. 

In general, varying the elasticity parameters does not significantly change the results of the 

economic impact assessment analysis presented above. The expected price increase remains 

relative stable across the scenarios in comparing with the primary case for the Small SI and Marine 

SI engine and equipment. The difference in expected price change between alternative and 

primary scenarios is less than 0.5 percent. Total social costs are about the same across all 

sensitivity analysis scenarios, $444 million. In addition, varying these model parameters does not 

significantly affect the way the social costs are borne. In all cases, the end user (households) bear 

the majority of the burden (over 76 percent), although there are differences in the way the costs are 

borne among the scenarios between the change in either demand or supply elasticity. The share of 

social costs end users (households) bear, for example, ranges from 66 to 98 percent. 

With regard to the scenario of alternative baseline prices, although the difference in prices 

is about 27%and 52% for lawn mower and tractors, respectively, the estimates on absolute price 

change and social cost for each market are approximately the same as in the base case. However, 

given that the baseline prices are different in these scenarios, there is some variation in projected 

relative price and quantity change across the scenarios. The expected changes in relative prices 

and quantity increase under the lower alternative baseline market price scenarios. 

A recent higher gasoline price will have the impacts to our analyses. A higher gasoline 

price is expected to increase the fuel savings estimated from primary analysis thus to reduce the 

net social cost of the final emission standards. In addition, we will describe qualitatively how the 

consumers would response to the fuel efficiency gains that result from applying technologies to 

achieve the evaporative emission standards being finalized in this rule in Scenario 4. 

9-130 
Economic Impact Analysis 

9H.1 Model Elasticity Parameters 

Consumer demand and producer supply responsiveness to changes in the commodity prices 

are referred to by economists as “elasticity.” The measure is typically expressed as the 

percentage change in quantity (demanded or supplied) brought about by a percent change in own 

price. A detailed discussion regarding the estimation and selection of the elasticities used in the 

EIM are discussed in Appendix 9E. This component of the sensitivity analysis examines 

the impact of changes in selected elasticity values, holding other parameters constant. The goal 

is to determine whether alternative elasticity values significantly alter conclusions in this report. 

9H.1.1 Alternative Supply and Demand Elasticity Parameters 

The choice of supply and demand elasticities for the engine and equipment market is 

important because changes in quantities in the equipment markets are the key drivers in the 

derived demand functions used to link impacts in the engine and equipment markets. In addition, 

the distribution of regulatory costs depends on the relative supply and demand elasticities used in 

the analysis. For example, consumers will bear less of the regulatory burden if they are more 

responsive to price changes than producers. 

Table 9H-1 reports the upper- and lower-bound values of the engine and equipment market 

elasticity parameters (supply and demand) used in the sensitivity analysis. The engine and 

equipment market supply elasticities are derived econometrically. Therefore, the upper and lower 

bound values were computed using the coefficient and standard error values associated with the 

econometric analysis and reflected 95 percent confidence interval. 

9-131 
Final Regulatory Impact Analysis 

Table 9H-1: Alternative Supply and Demand Elasticities Used in Sensitivity Analysisa,b 

Parameter/Market Upper Bound Primary Case Lower Bound 

Supply Elasticities 

Engines 

Marine and Small SI 5.0 9.5 13.9 

Equipment 

Marine SI 

All other vessel types 3.1 3.8 4.4 

PWC 3.5 5.2 6.9 

Small SI 

Small SI (handheld/nonhandheld) 5.1 10.0 14.8 

Gensets/welders 6.2 8.8 11.4 

Demand Elasticities 

Engines 

Marine and Small SI Derived Demand Derived Demand Derived Demand 

Equipment 

Marine SI 

All vessel types –3.9 –2.0 –0.1 

Small SI 

Handheld –2.5 –1.9 –1.3 

Lawn mowers –0.3 –0.2 –0.1 

Other lawn and garden –1.5 –0.9 –0.3 

Gensets/welders—Class I –2.2 –1.4 –0.6 

Gensets/welders—Class II –1.4 –1.1 –0.8 

All other handheld –1.9 –1.0 –0.1

 a For the demand elasticity, EPA computed upper- and lower-bound estimates using the coefficient and standard error 

values associated with its econometric analysis and reflect a 95 percent confidence interval. b

 For the supply elasticity, see Li, May 19, 2008, memorandum prepared for this Docket, “Supply Elasticity Estimation 

Report”, for the interval estimates. 

9H.1.2 Engines and Equipment Market (Supply Elasticity Parameters) 

The results of the EIM using these alternative supply elasticity values for the Small SI and 

Marine SI engine and equipment markets are reported in Tables 9H-2. As can be seen in the table, 

projected changes in market prices are stable across the upper- and lower-bound sensitivity 

scenarios. The relative change in price is around the primary case by 0.3 percent. Absolute 

9-132 
Economic Impact Analysis 

quantities vary but the percentage changes in output are negligible for the two scenarios. The 

change in total social surplus for 2014 also remains nearly unchanged across all scenarios and is 

approximately the same as for the rule ($444 million). 

However, varying the supply elasticity changes the social impacts (how the burden is 

shared across markets). Manufacturers bear a smaller share of the social costs when they are more 

responsive to price changes (supply upper bound scenario). As shown for the Small SI market, 

engine and equipment manufacturers bear approximately 1.4 and 4.7 percent, respectively, in the 

supply upper bound scenario compared to 2.0 and 6.6 percent in the base case. In contrast, they 

bear a higher share of social cost when they are less responsive to price changes relative to the 

base case (the supply lower bound scenario). For the Marine SI market, engine and equipment 

manufacturers bear approximately 4.5 and 15.4 percent, respectively, in supply upper bound 

scenario compared to 6.2 and 17.5 percent in the base case. In contrast, they bear a higher share 

when they are less responsive to price changes relative to the base case (supply lower bound 

scenario). 

9-133 
Final Regulatory Impact Analysis 

Table 9H-2: Sensitivity Analysis for Engine and Equipment Market Supply Elasticities 

for 2013 a,b 

Primary Case Supply Lower Bound Supply Upper Bound 

Scenario Absolute Relativeb Absolute Relativeb Absolute Relativeb 

Marine 

Market-Level Impacts 

Price 

Engines $266.5 2.4% $249.3 2.2% $273.5 2.5% 

Equipment $285.4 1.6% $252.1 1.4% $307.0 1.7% 

Quantity 

Engines -10,883 -2.7% -9,385 -2.3% -11,838 -2.9% 

Equipment -12,229 -3.2% -10,684 -2.8% -13,203 -3.5% 

Welfare Impacts (million $) 

Change in engine manufacturers surplus $10.5 6.2% $17.4 10.2% $7.7 4.5% 

Change in equipment manufacturers $29.7 17.5% $34.1 20.0% $26.3 15.4% 

surplus 

Change in end user (households) surplus $130.0 76.4% $119.2 69.8% $136.0 80.0% 

Small SI 

Market-Level Impacts 

Price 

Engines $13.7 8.3% $13.5 8.1% $13.8 8.3% 

Equipment $9.5 2.6% $8.9 2.4% $9.8 2.6% 

Class I $16.6 6.2% $15.7 5.9% $16.9 6.3% 

Class II $23.7 2.6% $22.1 2.4% $24.5 2.7% 

HH $0.3 0.2% $0.3 0.1% $0.4 0.2% 

Quantity 

Engines –303.992 –1.9% –279,592 –1.7% –314,636 –1.9% 

Equipment –360.310 –1.4% –326,161 –1.2% –367,250 –1.4% 

Class I –209,284 –2.1% –194,465 –2.0% –215,513 –2.2% 

Class II –101,104 –2.8% –92,979 –2.6% –104,638 –2.9% 

HH –49,992 –0.3% –38,717 –0.2% –47,100 –0.3% 

Welfare Impacts (million $) 

Change in engine manufacturers surplus $5.4 2.0% $9.31 3.4% $3.76 1.4% 

Change in equipment manufacturers $18.1 6.6% $30.4 11.1% $12.9 4.7% 

surplus 

Change in end user (households) surplus $250.2 91.4% $234.1 85.5% $256.9 93.9% 

Subtotal Social Costs (million $) $443.8 $444.4 $443.4 

Fuel Savings (million $) $115.9 $115.9 $115.9 

Total Social Costs (million $) $327.9 $328.6 $327.6 

a Figures are in 2005 dollars. b For “prices” rows the “relative” column refers to the relative change in price (with regulation) from the baseline 

price. For “Surplus” rows, the “relative” column contains the distribution of total surplus changes among 

stakeholders (consumers and producers). 

9-134 
Economic Impact Analysis 

9H.1.3 Equipment Market (Demand Elasticity Parameters) 

Sensitivity analysis was also conducted for the equipment market demand elasticities. The 

range of demand elasticity values evaluated for each market is provided in Table 9H-1. 

The demand elasticities for the engine markets are derived as part of the model, and therefore 

sensitivity analysis was not conducted on those parameters.16 In other words, the change in the 

equipment market quantities determines the demand responsiveness in the engine market. As a 

result, the demand sensitivity analysis for engine markets is indirectly shown in Table 9H-2. 

16For a discussion of the concept of derived demand, see Section 9.2.3.2 Incorporating Multimarket 

Interactions. 

9-135 
Final Regulatory Impact Analysis

9-136

Table 9H-3: Sensitivity Analysis for Equipment Market Demand Elasticities for 2013 a,b 

Primary Case Demand Lower Bound Demand Upper Bound

Scenario Absolute Relativeb Absolute Relativeb Absolute Relativeb

Marine

Market-Level Impacts

Price

Engines $266.5 2.4% $290.5 2.7% $255.7 2.3%

Equipment $285.4 1.6% $443.4 2.5% $211.2 1.2%

Quantity

Engines -10,883 -2.7% –905 –0.2% –15,198 –3.7%

Equipment -12,229 -3.2% –934 –0.2% –17,854 –4.7%

Welfare Impacts (million $)

Change in engine manufacturers surplus $10.5 6.2% $0.9 0.5% $14.7 8.7%

Change in equipment manufacturers

surplus

$29.7 17.5% $2.3 1.3% $42.8 25.4%

Change in end user (households) surplus $130.0 76.4% $170.4 98.2% $110.9 65.8%

Small SI

Market-Level Impacts

Price

Engines $13.7 8.4% $14.0 8.4% $13.5 8.2%

Equipment $9.5 2.6% $10.1 2.7% $9.0 2.5%

Class I $16.6 6.2% $17.2 6.4% $15.9 6.0%

Class II $23.7 2.6% $25.1 2.7% $22.5 2.5%

HH $0.3 0.2% $0.3 0.2% $0.3 0.2%

Quantity

Engines –303.992 –1.9% –99,098 –0.6% –486,671 –3.0%

Equipment –360.310 –1.4% –146,272 –0.6% –558,525 –2.1%

Class I –209,284 –2.1% –66,388 –0.8% –340,554 –3.3%

Class II –101,104 –2.8% –35,948 –1.9% –156,182 –3.6%

HH –49,992 –0.3% –43,939 –0.3% –61,788 –0.4%

Welfare Impacts (million $)

Change in engine manufacturers surplus $5.4 2.0% $1.8 0.7% $8.4 3.1%

Change in equipment manufacturers

surplus

$18.1 6.6% $6.2 2.3% $28.3 10.4%

Change in end user (households) surplus $250.2 91.4% $267.3 97.1% $235.4 86.5%

Subtotal Social Costs (million $) $443.8 $448.8 $440.6

Fuel Savings (million $) $115.9 $115.9 $115.9

Total Social Costs (million $) $327.9 $333.0 $324.7

a Figures are in 2005 dollars. b For “prices” rows the “relative” column refers to the relative change in price (with regulation) from the baseline

price. For “Surplus” rows, the “relative” column contains the distribution of total surplus changes among

stakeholders (consumers and producers).
Economic Impact Analysis 

As shown in Tables 9H-3, market prices are relative stable across the upper- and lowerbound sensitivity scenarios. The relative change in price is around the primary case by 0.5 

percent. Absolute quantities vary and the percentage changes in output are small for the two 

scenarios. There is also a small change in total social surplus for 2014 compared to the primary 

case ($444 million) but this is negligible in terms of the percentage change. 

In comparing Table 9H-3 with Table 9H-2 , all quantitative estimates for the market 

impacts (price and quantity changes) by the EIM model are a little more sensitive to the alternative 

demand elasticities than the alternative supply elasticities. However, theses changes remain in a 

reasonable range when compared with the rule, across both the upper and lower bound demand 

elasticity scenarios for the equipment markets. 

It should be noted, varying the demand elasticity changes the social impacts (how the 

burden is shared across markets) as in the case of changing the supply elasticity. Manufacturers 

bear a smaller share of the social costs when consumers are less responsive to price changes 

(demand lower bound scenario). As shown for the Small SI market, engine and equipment 

manufacturers bear approximately 0.7 and 2.3 percent, respectively, in the demand lower bound 

scenario compared to 2.0 and 6.6 percent in the base case. In contrast, they bear a higher share of 

social cost when consumers are more responsive to price changes relative to the base case (the 

demand upper bound scenario). For the Marine SI market, engine and equipment manufacturers 

bear approximately 0.5 and 1.3 percent, respectively, in demand lower bound scenario compared 

to 6.2 and 17.5 percent in the base case. In contrast, they bear a higher share when consumers are 

more responsive to price changes relative to the base case (demand upper bound scenario). 

9-137 
Final Regulatory Impact Analysis 

9H.2 Alternative Baseline Prices for Lawn Mower & Tractor 

As discussed in Section 9.3.2, the starting point for the economic impact analysis is initial 

market equilibrium conditions (prices and quantities) that exist prior to the implementation of new 

standards. At the pre-control market equilibrium conditions, consumers are willing to purchase the 

same amount of a product that producers are willing to produce at the market price. Since the 

lawn mower and tractor equipment are the most popular equipment in the Small SI market and 

their prices range widely, a sensitivity analysis was performed to examine how alternative baseline 

prices for lawn mower and tractor influence the EIM results. 

Table 9H-4: Market Sensitivity Analysis for Alternative Baseline for Lawnmower & Tractor 

Prices in 2014 a 

Scenario 

Average 

Baseline 

Price 

Market Results Welfare Results 

Change in 

Price 

(Absolute) 

Change 

in Price 

(%) 

Change in 

Quantity 

(Absolute) 

Change 

in 

Quantity 

(%) 

Change in 

End Users 

(Households) 

Surplus 

(Million $) 

Change in 

Equipment 

Manufacture 

r Surplus 

(Million $) 

Change 

in Total 

Surplus 

(Million 

$) 

Lawn Mowers 

(UL 125) 

Primary $218 $12.07 5.5% –76,121 –1.1% –$87.0 –$1.7 –$88.7 

scenario 

Low price $159 $12.03 7.6% –104,068 –1.4% –$86.5 –$1.7 –$88.2 

scenario 

Tractors 

(UL 250) 

Primary $1,937 $21.11 1.1% –23,690 –1.1% –$45.6 –$4.6 –$50.2 

scenario 

Low price $928 $20.98 2.3% –49,134 –2.3% –$45.1 –$4.5 –$49.6 

scenario 

a Figures are in 2005 dollars. 

We selected the lower end market prices as the alternative baseline prices for lawn mower 

and tractor in this sensitivity analysis. As shown in Table 9H-4, when these pre-control baseline 

prices are allowed to vary, the absolute change in market prices remains nearly unchanged when 

compared with the rule, although the relative price change and absolute quantity change are 

expected to be higher in the alternative baseline price case. This is because the change in absolute 

price is ultimately determined by the per unit compliance cost and market supply and demand 

elasticities. In contrast, the change in relative price is determined by the ratio between the per-unit 

compliance cost and the baseline price. The lower the initial baseline price, the higher the ratio is 

for a given per unit compliance cost. Therefore, the change in the relative price is higher. In this 

market, consumers are expected to response to the higher relative price change by purchasing less 

equipment. As a result, the expected change for quantity is higher in the lower baseline prices 

case. Also as seen in Table 9H-4, varying the baseline prices are not expected to substantially 

change the social cost estimates in these markets or alter the distribution of the social costs across 

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Economic Impact Analysis 

the stakeholders. 

9H.3 Alternative Gasoline Price for Social Costs 

As discussed in 9.2.4.2, there are fuel savings attributed to the final emission control 

programs, reflecting the use of more fuel efficient technology to meet evaporative and exhaust 

emission requirements. These fuel savings are included in the social cost analysis because they are 

savings that accrue to society. 

For the social costs analysis, EPA calculated fuel savings using the 2005 pre-tax price of 

gasoline of $1.81 per gallon and this value is held constant for each future years (see section 

9.3.5). Because of the recent trend of increasing gasoline prices, we may be understating the fuel 

savings in our cost analysis. This is reflected in recent fuel price projections from the EIA’s 2008 

Annual Energy Outlook.18 To investigate the sensitivity of the net social cost to future fuel prices, 

we used the AEO “reference case” and “high price case” scenarios, as described in section 6.7.1. 

As indicated in Table 9H-5, comparing the AEO 2008 reference case with the primary 

case, the annual net social cost of the final standards is lower because of a higher fuel savings. 

The net present value of social cost decreases from $4.2 billion to $3.9 billion using a 3 percent 

discount rate. The net present value of social costs for the period of analysis falls from $2.7 billion 

to $2.6 billion using a 7 percent discount rate. 

As shown in Table 9H-6, fuel savings are even higher in the AEO 2008 high price case. 

Based on these fuel price projections, the increased fuel savings estimates would actually be higher 

than the projected costs, once the new equipment is fully phased in. In comparison with the 

primary case, the net present value of social costs decreases from $4.2 billion to $2.0 billion using 

a 3 percent discount rate. Using a 7 percent discount rate, the net present value of social costs for 

the period of analysis falls from $2.7 billion to $1.6 billion. 

18 Energy Information Administration, “Annual Energy Outlook 2008; with Projections to 2030,” 

DOE/EIA-0383(2008), June 2008. 

9-139 
Final Regulatory Impact Analysis 

Table 9.H-5: Sensitivity of Gasoline Price to Net Social Cost -AEO 2008 Reference Case 

Year Total 

Engineering 

Costs 

Total Social 

Costs 

Fuel Savings 

AEO 2008 

Reference Case 

Projected 

Gasoline Price 

Net Social Costs 

AEO 2008 

Reference case 

Projected 

Gasoline Price 

Net Social Costs 

2005 Constant 

Gasoline Price 

(Primary Analysis) 

2008 

2009 

2010 

2011 

2012 

2013 

2014 

2015 

2016 

2017 

2018 

2019 

2020 

2021 

2022 

2023 

2024 

2025 

2026 

2027 

2028 

2029 

2030 

2031 

2032 

2033 

2034 

2035 

2036 

2037 

$54 

$127 

$271 

$329 

$442 

$445 

$450 

$412 

$409 

$398 

$403 

$408 

$413 

$418 

$423 

$428 

$433 

$438 

$443 

$449 

$454 

$459 

$464 

$469 

$474 

$479 

$484 

$489 

$494 

$499 

$54 $5 $49 $51 

$126 $11 $116 $118 

$267 $24 $243 $248 

$324 $52 $272 $280 

$435 $80 $355 $365 

$439 $105 $334 $344 

$444 $126 $318 $328 

$407 $140 $266 $273 

$404 $153 $251 $253 

$394 $168 $225 $229 

$399 $184 $215 $221 

$404 $204 $200 $213 

$409 $221 $187 $207 

$414 $228 $185 $203 

$419 $241 $178 $198 

$424 $251 $172 $194 

$429 $259 $169 $191 

$434 $269 $164 $189 

$439 $278 $160 $188 

$444 $287 $157 $187 

$449 $297 $152 $186 

$454 $306 $147 $185 

$459 $314 $144 $186 

$464 $319 $144 $186 

$469 $324 $144 $187 

$474 $329 $145 $188 

$479 $333 $146 $189 

$484 $337 $147 $190 

$489 $341 $148 $192 

$494 $345 $149 $193 

NPV at 3% 

NPV at 7% 

$7,705 

$4,559 

$7,617 $3,743 $3,873 $4,242 

$4,506 $1,956 $2,550 $2,731 

9-140 
Economic Impact Analysis 

Table 9.H-6: Sensitivity of Gasoline Price to Net Social Cost - AEO 2008 Higher Case 

Year Total Engineering 

Costs 

Total Social 

Costs 

Fuel Savings 

AEO 2008 

Higher Case 

Projected 

Gasoline Price 

Net Social Costs 

AEO 2008 

Higher Case 

Projected 

Gasoline Price 

Net Social Costs 

2005 Constant 

Gasoline Price 

(Primary Analysis) 

2008 $54 

2009 $127 

2010 $271 

2011 $329 

2012 $442 

2013 $445 

2014 $450 

2015 $412 

2016 $409 

2017 $398 

2018 $403 

2019 $408 

2020 $413 

2021 $418 

2022 $423 

2023 $428 

2024 $433 

2025 $438 

2026 $443 

2027 $449 

2028 $454 

2029 $459 

2030 $464 

2031 $469 

2032 $474 

2033 $479 

2034 $484 

2035 $489 

2036 $494 

2037 $499 

$54 

$126 

$267 

$324 

$435 

$439 

$444 

$407 

$404 

$394 

$399 

$404 

$409 

$414 

$419 

$424 

$429 

$434 

$439 

$444 

$449 

$454 

$459 

$464 

$469 

$474 

$479 

$484 

$489 

$494 

$5 

$11 

$27 

$61 

$100 

$137 

$169 

$198 

$226 

$253 

$277 

$301 

$325 

$351 

$371 

$386 

$402 

$411 

$423 

$437 

$450 

$464 

$479 

$487 

$494 

$501 

$507 

$514 

$520 

$525 

$49 $51 

$115 $118 

$240 $248 

$263 $280 

$336 $365 

$302 $344 

$274 $328 

$209 $273 

$179 $253 

$141 $229 

$122 $221 

$102 $213 

$84 $207 

$63 $203 

$47 $198 

$37 $194 

$27 $191 

$23 $189 

$16 $188 

$7 $187 

($2) $186 

($11) $185 

($20) $186 

($23) $186 

($25) $187 

($27) $188 

($29) $189 

($30) $190 

($31) $192 

($32) $193 

NPV at 3% $7,705 

NPV at 7% $4,559 

$7,617 

$4,506 

$5,585 

$2,886 

$2,032 $4,242 

$1,620 $2,731 

9-141 
Final Regulatory Impact Analysis 

9H.4 Discussion of Fuel Savings Effects on EIA Analysis 

The final evaporative and exhaust controls are expected to result in fuel savings for 

consumers due to the use of more fuel efficient technology to meet evaporative and exhaust 

emission requirements. Although these fuel savings represent a cost savings for consumers, our 

EIM model assumes that consumers do not consider these fuel savings in their purchasing 

decisions. As a result, the EIM model does not include a shift in the demand curve due to more 

fuel efficient products causing the demand curve in each small SI or marine SI equipment market 

to remain unchanged. This has been explained in Section 9.2.4.2. Although the fuel savings are 

not directly incorporated in the market model, the benefits to society are captured as an added line 

item to offset the total social costs of the program. 

Figure 9H.1- (a) summarizes the EIA primary analysis that was presented earlier. The 

market equilibrium of a representative equipment market is at point A prior to the regulation (the 

baseline case). With the regulation, compliance costs lead to an upward shift in the market supply 

curve. The new market equilibrium is at point B (the primary case). In this case, the demand curve 

for the equipment remains unchanged; the regulatory program only influences the supply side of 

the market (e.g. additional costs of the program [S0 to S1 ]); and fuel savings are added as a line 

item to the social costs. 

This section explores an alternative way to treat the fuel savings in the analysis by 

assuming consumers are fully aware of the fuel savings and realize that these improvements will 

lower the future cost of using equipment. Since many consumers may prefer more fuel efficient 

equipment, they may be willing to initially pay more for Small SI and Marine SI equipment 

because of these future operation savings. This leads to a change in demand and shifts the demand 

curve upward. 

This concept may be described using illustrations of supply and demand curves. As 

indicated in Figure 9H.1-(b), if the fuel savings (lower costs of operating equipment) are 

incorporated in the model as a demand shift (DA to DC) that ultimately raises the quantity that 

buyers wish to purchase at a higher market price. The new equilibrium that includes this demand 

shift is at point C (the alternative case). Incorporating this demand shift in the model would lead 

to the following effects:

 •	 Equipment price and quantity: Including the demand shift due to fuel savings in the 

model will increase the projected price and quantity in the equipment market 

relative to the primary case. Consumers are willing to purchase more Small SI and 

Marine SI equipment at a higher price because of fuel efficiency characteristics. 

Since the equipment has become more desirable, producers could sell these 

equipment at a higher price. In comparing with the primary case (PB and QB), the 

new market equilibrium price and quantity (PC and QC) in the alternative case are 

higher. 

•	 Fuel Savings: At a given Q, consumers are willing to pay more for the equipment 

with fuel efficiency technology. The fuel savings are measured by difference in 

9-142 
Economic Impact Analysis 

consumer’s willingness to pay as indicated in the shaded area in Figure 9.H.1-(b) 

•	 Social costs: Including the demand shift due to fuel savings will increase total 

social welfare as indicated in Figure 9.H.2. by the area GFBC. This is because 

consumers are willing to purchase more at a higher price and producers are 

charging more and selling more. Both consumer surplus and producer surplus are 

increased because the fuel efficient technology. The social cost is measured as the 

change in total social welfare and is now lower in the alternative case. 

•	 Distribution of social costs: the primary case assumes all the fuel savings benefits 

are attributed to the consumer. In the alternative case, consumers and producers 

share these benefits since the demand shift leads to high equipment prices and 

higher sells. If producers are more responsive to equipment price changes than 

consumers (e.g. their supply elasticity is higher than the consumer’s demand 

elasticity), they may receive a higher share of the fuel savings benefits in the form 

of higher profits from equipment sales. 

The likelihood of consumers considering fuel savings in their purchasing decisions is 

dependent on the magnitude of the fuel savings relative to their income. For the small handheld 

equipment and lawnmowers used for personal lawn maintenance, operation cost savings would 

likely have a small influence on equipment purchase decisions. In contrast, for operators of large 

recreational boats or lawnmowers used by lawn care businesses, the additional gasoline cost 

savings could influence purchase decisions. While the directional effects of these decisions are 

discussed above, EPA does not have the sufficient data and information to quantify these effects. 

9-143 
Final Regulatory Impact Analysis 

Figure 9.H.1: Demand Side Effect of Fuel Savings in the Equipment Market 

Figure 9.H.2: Social Welfare Change 

9-144 
Small-Business Flexibility Analysis 

CHAPTER 10: Small-Business Flexibility Analysis 

This chapter presents our Small Business Flexibility Analysis (SBFA) which evaluates 

the impacts of the rule on small businesses. Prior to issuing our proposed rule, we analyzed the 

potential impacts of our program on small businesses. As a part of this analysis, we convened a 

Small Business Advocacy Review Panel (SBAR Panel or ‘the Panel’), under the requirements of 

the Regulatory Flexibility Act (RFA), as amended by the Small Business Regulatory 

Enforcement Fairness Act (SBREFA) of 1996, 5 USC 601 et seq. Through the Panel process, 

we gathered advice and recommendations from small entity representatives (SERs) who would 

be affected by the regulation. The Panel issued a report recommending that EPA consider and 

seek comment on a wide range of regulatory alternatives to mitigate the impacts of the 

rulemaking on small businesses. The Panel report has been placed in the rulemaking record. 

In the proposal, EPA proposed provisions consistent with each of the Panel’s 

recommendations and sought comments on all of the small business provisions. We received a 

number of comments during the comment period after we issued the proposal. A summary of all 

comments pertaining to the small business provisions can be found in our Summary and 

Analysis of Comments document contained in the public docket for this rulemaking. A list of 

the small business provisions being adopted with the final rule is presented in section 10.7 

below. 

10.1 Overview of the Regulatory Flexibility Act 

In accordance with section 603 of the RFA, EPA prepared an initial regulatory flexibility 

analysis (IRFA) for the proposed rule and convened a Small Business Advocacy Review Panel 

to obtain advice and recommendations of representatives of the regulated small entities in 

accordance with section 609(b) of the RFA (see 72 FR 28098, May 18, 20007). A detailed 

discussion of the Panel's advice and recommendations is found in the Panel Report contained in 

the docket for this rulemaking. A summary of the Panel's recommendations is presented at (72 

FR 28098). 

Section 609(b) of the Regulatory Flexibility Act further directs the Panel to report on the 

comments of small entity representatives and make findings on issues related to identified 

elements of the IRFA under section 603 of the Regulatory Flexibility Act. Key elements of an 

IRFA are: 

- A description of and, where feasible, an estimate of the number of small entities to 

which the proposed rule will apply; 

- Projected reporting, record keeping, and other compliance requirements of the proposed 

rule, including an estimate of the classes of small entities which will be subject to the 

requirements and the type of professional skills necessary for preparation of the report or 

record; 

- An identification to the extent practicable, of all other relevant Federal rules which may 

10-1 
Final Regulatory Impact Analysis 

duplicate, overlap, or conflict with the proposed rule; 

- Any significant alternatives to the proposed rule which accomplish the stated objectives 

of applicable statutes and which minimize any significant economic impact of the 

proposed rule on small entities. 

The Regulatory Flexibility Act was amended by SBREFA to ensure that concerns 

regarding small entities are adequately considered during the development of new regulations 

that affect those entities. Although we are not required by the Clean Air Act to provide special 

treatment to small businesses, the Regulatory Flexibility Act requires us to carefully consider the 

economic impacts that our rules will have on small entities. The recommendations made by the 

Panel may serve to help lessen these economic impacts on small entities when consistent with 

Clean Air Act requirements. 

For purposes of assessing the impacts of this action on small entities, a small entity is 

defined as: (1) a small business as defined by the Small Business Administration's (SBA) 

regulations at 13 CFR 121.201; (2) a small governmental jurisdiction that is a government of a 

city, county, town, school district or special district with a population of smaller than 50,000; 

and (3) a small organization that is any not-for-profit enterprise which is independently owned 

and operated and is not dominant in its field. 

After considering the economic impacts of today's final rule on small entities, we believe 

that this action will not have a significant economic impact on a substantial number of small 

entities. The small entities directly regulated by this final rule cover a wide range of small 

businesses including engine manufacturers, equipment manufacturers, boat manufacturers, fuel 

tank manufacturers, and fuel hose manufacturers. No small governmental jurisdictions or small 

non-profits are impacted by this final rule. We have determined that 61 small businesses will 

experience an impact of greater than 1 percent. These 61 companies represent less than 5 

percent of the small business identified by EPA. 

Despite the determination that this rule will not have a significant economic impact on a 

substantial number of small entities, we have prepared a Small Business Flexibility Analysis that 

has all the components of a final regulatory flexibility analysis (FRFA). An FRFA examines the 

impact of the final rule on small businesses along with regulatory alternatives that could reduce 

that impact. The Small Business Flexibility Analysis is presented in this chapter. 

10.2 Need for and Objective of the Rulemaking 

A detailed discussion on the need for and objectives of this final rule are located in the 

preamble to the final rule. As presented in Chapter 8, controlling exhaust and evaporative 

emissions from Small SI engines and equipment and Marine SI engines and vessel has important 

public health and welfare benefits. 

Section 213(a) of the CAA directs EPA to: (1) conduct a study of emissions from 

nonroad engines and vehicles; (2) determine whether emissions of CO, NOx, and VOCs from 

nonroad engines and vehicles are significant contributors to ozone or CO in more than one area 

10-2 
Small-Business Flexibility Analysis 

which has failed to attain the National Ambient Air Quality Standard (NAAQS) for ozone or 

CO; and (3) if nonroad emissions are determined to be significant, regulate those categories or 

classes of new nonroad engines and vehicles that cause or contribute to such air pollution. 

Section 213(a)(3) states that the emission standards “shall achieve the greatest degree of 

emission reduction achievable through the application of technology” giving appropriate 

consideration to cost, noise, energy, safety, and lead time. 

The Nonroad Engine and Vehicle Emission Study required by section 213(a)(1) was 

completed in November 1991. The determination of the significance of emissions from nonroad 

engines and vehicles in more than one NAAQS nonattainment area was published on June 17, 

1994. At the same time, the first set of regulations for new land-based nonroad compressionignition (CI) engines at or above 37 kW was promulgated. EPA has also issued proposed or 

final rules for most other categories of nonroad engines, including engines used in lawn and 

garden equipment, recreational marine vessels, forklifts, recreational vehicles, locomotives, and 

ships. In addition, EPA has revised the emission standards for many of these categories of 

nonroad engines one or more times to achieve further emission reductions. 

In addition to the general authority to regulate nonroad engines under the CAA, section 

428 of the Omnibus Appropriations Bill for 2004 requires EPA to propose and finalize new 

regulations for nonroad spark-ignition engines less than 50 horsepower (hp). The Bill directs 

EPA to propose regulations by December 1, 2004 and finalize them by December 31, 2005. 

EPA’s assessment of new standards is to be carried out under section 213 of the CAA. 

Finally, section 205 of Public Law 109-54 included an additional requirement that EPA 

complete a technical study, to look at safety issues related to the potential standards called for 

under the Omnibus Appropriations Bill for 2004. The law directed EPA to complete the study 

prior to issuing the proposal called for in the Omnibus Appropriations Bill for 2004. In response 

to this requirement, EPA prepared a technical study on safety in coordination with the Consumer 

Product Safety Commission (CPSC). The study analyzes the incremental risk of fire and burn to 

consumers that could result from the new standards. EPA published the study in March 2006. 

In response to these requirements, today’s action adopts controls on exhaust and 

evaporative emissions from Small SI engines and equipment and Marine SI engines and vessels. 

10.3 Summary of Significant Public Comments 

In the proposal, EPA proposed provisions consistent with each of the Panel's 

recommendations and sought comments on all of the small business provisions (see 72 FR 

28245, May 18, 2007). As noted earlier, we received a number of comments during the 

comment period after we issued the proposal. A summary of all comments pertaining to the 

small business provisions can be found in our Summary and Analysis of Comments document 

contained in the public docket for this rulemaking. A few changes have been made to some of 

the proposed flexibilities in response to the comments as well as other changes made in the 

rulemaking. Those changes are noted in section 10.7.1 below. 

10-3 
Final Regulatory Impact Analysis 

10.4 Definition and Description of Small Entities 

Small entities include small businesses, small organizations, and small governmental 

jurisdictions. As noted earlier, for the purposes of assessing the impacts of a rule on small 

entities, a small entity is defined as: (1) a small business that meets the definition for business 

based on the Small Business Administration’s (SBA) size standards (see Table 10.4-1); (2) a 

small governmental jurisdiction that is a government of a city, county, town, school district or 

special district with a population of less than 50,000; and (3) a small organization that is any notfor-profit enterprise which is independently owned and operated and is not dominant in its field. 

Table 10.4-1 provides an overview of the primary SBA small business categories that will be 

affected by this regulation. 

Table 10.4-1: Small Business Definitions for Entities Affected by this Rule 

Industry NAICS Codesa Defined as small entity by 

SBA if less than or equal to:b 

Nonroad SI Engine Manufacturers 333618 1,000 employees 

Equipment Manufacturers:

 Farm Machinery 

Lawn and Garden

 Construction

 Sawmill and Woodworking

 Pumps

 Air and Gas Compressors

 Generators 

333111 

333112 

333120 

333210 

333911 

333912 

335312 

500 employees 

500 employees 

750 employees 

500 employees 

500 employees 

500 employees 

1,000 employees 

Boat Builders 336612 500 employees 

Fuel Tank Manufacturers:

 Other Plastic Products

 Metal Stamping 

Metal Tank (Heavy Gauge) 

326199 

332116 

332420 

500 employees 

500 employees 

500 employees 

Fuel Hose Manufacturers:

 Rubber and Plastics Hoses 326220 500 employees 

a

 North American Industry Classification System 

b

 As defined in SBA’s regulations at 13 CFR part 121. 

10.4.1 Small SI Engines and Equipment 

For Small SI engines and equipment, the SBA small business size standards are 1,000 

employees for engine manufacturers, 1,000 employees for generator manufacturers, 750 

employees for construction equipment manufacturers, and 500 employees for manufacturers of 

other types of equipment. To identify companies that meet these criteria, we compiled a list of 

engine manufacturers and equipment manufacturers using information from a database prepared 

by Power Systems Research (PSR) that contains data on Small SI engines and equipment sold in 

the United States. EPA augmented this information with the list of engine manufacturers 

10-4 
Small-Business Flexibility Analysis 

currently certifying with EPA under the Small SI engine regulations. We then found 

employment data for each company (or parent company if an individual company is part of a 

larger group) using databases such as the Thomas Register and Dunn and Bradstreet. 

The SBA small business size standard for manufacturers that produce fuel tanks or fuel 

hose is 500 employees. To identify companies that meet this criterion, we compiled a list of 

manufacturers that produce fuel tanks and fuel hoses for the Small SI equipment market. The list 

was based on information from the California Air Resources Board, who has recently adopted 

requirements for Small SI engine fuel tank and fuel hose manufacturers, and additional 

information from Small SI equipment manufacturers and the Association of Rotational Molders 

International. We then found employment data for each of the companies (or parent company if 

an individual company is part of a larger group) using databases such as Thomas Register and 

onesourceexpress.com and discussions with some of the manufacturers. 

10.4.2 Marine SI Engines and Vessels 

For Marine SI engines and vessels, the SBA small business size standards are 1,000 

employees for engine manufacturers and 500 employees for boat builders. To identify 

companies that meet these criteria, we used a number of different sources. For engine 

manufacturers, we compiled a list based on the engine manufacturers currently certifying with 

EPA and the California Air Resources Board (CARB) under the existing Marine SI engine 

regulations and augmented the list with additional information on SD/I manufacturers, who do 

not currently have to certify with EPA. We gathered additional information from boat shows, 

the Internet, trade magazines, the National Marine Manufacturers Association (NMMA), and 

discussions with individual manufacturers. For vessel manufacturers, we used information from 

a database of boat builders maintained by the U.S. Coast Guard. 

The SBA small business size standard for manufacturers that produce fuel tanks or fuel 

hose is 500 employees. For fuel tank and fuel hose manufacturers, we compiled a list based on 

information gathered from the NMMA, trade shows, the Internet and discussions with 

manufacturers. We then found employment data for these companies (or parent company if an 

individual company is part of a larger group) using databases such as Thomas Register and 

discussions with trade groups and individual manufacturers. 

10.5 Type and Numbers of Small Entities Affected 

As noted above, for each sector impacted by this final rule, SBA defines small entities by 

number of employees. This section gives an overview of the Small SI engine and equipment 

industries and the Marine SI engine and vessel industries, specifically related to small 

businesses. 

10.5.1 Small SI Engines and Equipment 

10-5 
Final Regulatory Impact Analysis 

Based on EPA certification records, the Small SI nonhandheld engine industry is made 

up primarily of large manufacturers including Briggs and Stratton, Tecumseh, Honda, Kohler 

and Kawasaki. The Small SI handheld engine industry is also made up primarily of large 

manufacturers including Electrolux Home Products, MTD, Homelite, Stihl and Husqvarna. EPA 

has identified 10 Small SI engine manufacturers that qualify as a small business under SBA 

definitions. Half of these small manufacturers certify gasoline engines and the other half certify 

liquefied petroleum gas (LPG) engines. 

The Small SI equipment market is dominated by a few large businesses including Toro, 

John Deere, MTD, Briggs and Stratton, and Electrolux Home Products. While the Small SI 

equipment market may be dominated by just a handful of companies, there are many small 

businesses in the market; however these small businesses account for less than 10 percent of 

equipment sales. We have identified over three hundred equipment manufacturers that qualify as 

a small business under the SBA definitions. More than 90 percent of these small companies 

manufacture less than 5,000 pieces of equipment per year. The median employment level is 65 

employees for nonhandheld equipment manufacturers and 200 employees for handheld 

equipment manufacturers. The median sales revenue is approximately $9 million for 

nonhandheld equipment manufacturers and $20 million for handheld equipment manufacturers. 

EPA has identified 25 manufacturers that produce fuel tanks for the Small SI equipment 

market that meet the SBA definition of a small business. Fuel tank manufacturers rely on three 

different processes for manufacturing plastic tanks – rotational molding, blow molding and 

injection molding. EPA has identified small business fuel tank manufacturers using the 

rotational molding and blow molding processes but has not identified any small business 

manufacturers using injection molding. In addition, EPA has identified two manufacturers that 

produce fuel hose for the Small SI equipment market that meet the SBA definition of a small 

business. The majority of fuel hose in the Small SI market is made by large manufacturers 

including Avon Automotive and Dana Corporation. 

10.5.2 Marine SI Engines and Vessels 

Based on EPA certification records, the OB/PWC market is made up primarily of large 

manufacturers including, Brunswick (Mercury), Bombardier Recreational Products, Yamaha, 

Honda, Kawasaki, Polaris, Briggs & Stratton, and Nissan. Two companies qualify as a small 

business under the SBA definitions. Tohatsu makes outboard engines. The other small business 

is Surfango which makes a small number of motorized surfboards and has certified their product 

as a PWC. 

The SD/I market is made up mostly of small businesses; however, these businesses 

account for less than 20 percent of engine sales. Two large manufacturers, Brunswick 

(Mercruiser) and Volvo Penta, dominate the market. We have identified 28 small entities 

manufacturing SD/I marine engines. The third largest company is Indmar, which qualifies as a 

small business based on the SBA threshold of 1,000 employees. Based on sales estimates, 

number of employees reported by Thomas Register, and typical engine prices, we estimate that 

10-6 
Small-Business Flexibility Analysis 

the average revenue for the larger small SD/I manufacturers is about $50-60 million per year. 

However, the vast majority of the SD/I engine manufacturers produce low production volumes 

of engines and typically have less than 50 employees. 

The two largest boat building companies are Brunswick and Genmar. Brunswick owns 

approximately 25 boat companies and Genmar owns approximately 12 boat companies. Based 

on a manufacturer list maintained by the U.S. Coast Guard, there are over 1,600 boat builders in 

the United States. We estimate that, based on manufacturer identification codes, more than 

1,000 of these companies produce boats using gasoline marine engines. According to the 

National Marine Manufacturers Association (NMMA), most of these boat builders are small 

businesses. These small businesses range from individuals building one boat per year to 

businesses near the SBA small business threshold of 500 employees. 

We have identified 14 marine fuel tank manufacturers in the United States that qualify as 

small businesses under the SBA definition. These manufacturers include five rotational molders, 

two blow molders, six aluminum fuel tank manufacturers, and one specialty fuel tank 

manufacturer. The small rotational molders average less than 50 employees while the small 

blow-molders average over 100 employees. 

We have only identified one small hose manufacturer that produces for the Marine SI 

market. Novaflex primarily distributes hoses made by other manufacturers, but does produce its 

own fill neck hose. Because we expect vessel manufacturers will design their fuel systems such 

that there will not be standing liquid fuel in the fill neck (and therefore the low permeation fuel 

hose requirements will not apply to the fill neck), we have not included this manufacturer in our 

analysis. The majority of fuel hose in the Marine SI market is made by large manufacturers 

including Goodyear and Parker-Hannifin. 

10.6 Reporting, Recordkeeping, and Compliance Requirements 

For any emission control program, EPA must have assurances that the regulated products 

will meet the standards. Historically, EPA programs for Small SI engines and Marine SI 

engines have included provisions placing engine manufacturers responsible for providing these 

assurances. The program that EPA is adopting for manufacturers subject to this final rule will 

include testing, reporting, and record keeping requirements for manufacturers of engines, 

equipment, and vessels, and will also include fuel system component manufacturers if they 

choose to certify their fuel tank, fuel hose, and fuel cap products. 

For Small SI engine manufacturers and OB/PWC engine manufacturers, EPA is generally 

continuing the same reporting, record keeping, and compliance requirements prescribed in the 

current regulations. For SD/I engine manufacturers, which are not currently subject to EPA 

regulation, EPA is planning to apply similar reporting, record keeping, and compliance 

requirements to those for OB/PWC engine manufacturers. Testing requirements for engine 

manufacturers will include certification emission (including deterioration factor) testing and 

production line testing. Reporting requirements will include emission test data and technical 

data on the engines. Manufacturers will also need to keep records of this information. 

10-7 
Final Regulatory Impact Analysis 

Because of the new evaporative emission requirements, there will be new reporting, 

record keeping and compliance requirements for Small SI equipment manufacturers. Small SI 

equipment manufacturers participating in the transition program will also be subject to reporting, 

record keeping and compliance requirements. Depending on who chooses to certify fuel system 

components, there may also be new reporting, record keeping and compliance requirements for 

fuel tank manufacturers, fuel hose manufacturers, fuel cap manufacturers, and marine vessel 

manufacturers. Testing requirements for these manufacturers will include certification emission 

testing. Reporting requirements will include emission test data and technical data on the designs. 

Manufacturers will also need to keep records of this information. 

10.7 Steps Taken to Minimize the Impact on Small Entities 

The Panel developed a wide range of regulatory alternatives to mitigate the impacts of 

the rulemaking on small businesses, and recommended that we propose and seek comment on 

the flexibilities. The Panel’s findings and discussions were based on the information that was 

available during the term of the Panel and issues that were raised by the SERs during the 

outreach meetings and in their written comments. It was agreed that EPA should consider the 

issues raised by the SERs (and issues raised in the course of the Panel) and that EPA should 

consider the comments on flexibility alternatives that would help to mitigate any negative 

impacts on small businesses. Alternatives discussed throughout the Panel process included those 

offered in the development of the upcoming rule. Though some of the recommended flexibilities 

may be appropriate to apply to all entities affected by the rulemaking, the Panel’s discussions 

and recommendations were focused mainly on the impacts, and ways to mitigate adverse 

impacts, on small businesses. A summary of the Panel’s recommendations can be found in the 

SBREFA Final Panel Report.1 

A list of the small business provisions being adopted with the final rule are presented in 

the following section. 

10.7.1 Small SI Exhaust Emission Standards 

Described below are the regulatory alternatives being adopted with the final rule related 

to the Small SI nonhandheld engine exhaust emission standards. 

10.7.1.1 Regulatory Flexibility Options for Nonhandheld Engine Manufacturers 

The following section contains a discussion of the provisions in the final rule for small 

business nonhandheld engine manufacturers. 

Additional Lead Time for Nonhandheld Engine Manufacturers - Small-volume engine 

manufacturers can delay implementation of the Phase 3 exhaust emission standards for two years 

(see §1045.145). Small-volume engine manufacturers will be required to comply with the Phase 

3 exhaust emission standards beginning in model year 2014 for Class I engines and model year 

2013 for Class II engines. Under this approach, small-volume engine manufacturers can apply 

this delay to all their nonhandheld engines or to just a portion of their production. They could 

10-8 
Small-Business Flexibility Analysis 

therefore sell engines that meet the Phase 3 standards on some product lines while delaying 

introduction of emission control technology on more challenging product lines. This option 

provides more time for small-volume engine manufacturers to redesign their products. They 

would also be able to learn from some of the hurdles overcome by larger manufacturers. 

Assigned Deterioration Factors - Small-volume engine manufacturers will be able to 

rely on an assigned deterioration factor to demonstrate compliance with the standards rather than 

doing service accumulation and additional testing to measure deteriorated emission levels at the 

end of the regulatory useful life (see §1054.240). EPA is not adopting actual levels for the 

assigned deterioration factors with this final rule. EPA intends to analyze emissions 

deterioration information that becomes available over the next few years to determine what 

deterioration factors would be appropriate for nonhandheld engines. This data is likely to 

include deterioration data for engines certified to comply with CARB’s Tier 3 standards and 

engines certified early to EPA’s Phase 3 standards. Prior to the implementation date for the 

Phase 3 standards, EPA expects to provide guidance to engine manufacturers specifying the 

levels of the assigned deterioration factors for small-volume engine manufacturers. 

Production Line Testing Exemption - Small-volume engine manufacturers will be 

exempt from the production-line testing requirements for all of their nonhandheld engine 

families (see §1054.301). 

Broader Definition of Engine Family - Small-volume engine manufacturers may use a 

broader definition of engine family than generally applies for certification purposes. Under the 

existing engine family criteria specified in the regulations, manufacturers group their various 

engine lines into engine families that have similar design characteristics including the 

combustion cycle, cooling system, cylinder configuration, number of cylinders, engine class, 

valve location, fuel type, aftertreatment design, and useful life category. With this final rule, we 

are allowing small-volume engine manufacturers to group all of their nonhandheld engines into a 

single engine family for certification by engine class and useful life category, subject to good 

engineering judgment (see §1054.230). 

Eligibility for the Small Business Flexibilities - We are retaining the current criteria 

(i.e., 10,000 units per year of nonhandheld engines) for determining who is a small-volume 

engine manufacturer and, as a result, eligible for the Phase 3 flexibilities described above (see 

§1054.801). Based on confidential sales data provided to EPA by engine manufacturers, the 

10,000 unit cut-off for engine manufacturers would include all of the small business engine 

manufacturers using SBA’s employee-based definition. However to ensure all small businesses 

that meet SBA’s employee-based definition have access to the flexibilities described above, EPA 

is also allowing engine manufacturers which exceed the production cut-off level of 10,000 units 

but have fewer than 1,000 employees, to request treatment as a small volume engine 

manufacturer (see §1054.635). In such a case, the manufacturer would need to provide 

information to EPA demonstrating that the manufacturer has fewer employees than the 1,000 

cut-off level established by SBA. 

10-9 
Final Regulatory Impact Analysis 

10.7.1.2 Regulatory Flexibility Options for Nonhandheld Equipment Manufacturers 

The following section contains a discussion of the provisions in the final rule for small 

business nonhandheld equipment manufacturers. 

Additional Lead Time for Small SI Equipment Manufacturers - Small-volume 

equipment manufacturers will have two extra years beyond the implementation dates for the 

Phase 3 standards to continue using Phase 2 engines in their Class II equipment. Alternatively, 

the manufacturer can use Phase 3 engines without the catalysts, provided the engine 

manufacturer submitted data at the time of certification showing that the engine without the 

catalyst complied with EPA’s Phase 2 standards. As described in Section V.E.3 of the preamble, 

EPA is adopting a flexibility program for all equipment manufacturers that produce Class II 

equipment. Under that program, equipment manufacturers can install Phase 2 engines in limited 

numbers of Class II equipment over the first four years the Phase 3 standards apply (i.e., 2011 

through 2015). The number of equipment that can use Phase 2 engines is based on 30 percent of 

an average annual production level of Class II equipment. In an effort to provide additional 

flexibility to small-volume equipment manufacturers within the context of the flexibility 

program, EPA is adopting provision that allow small-volume equipment manufacturers to use 

Phase 2 engines at a level of 200 percent of an average annual production level of Class II 

equipment over the four year period (see §1054.625). Therefore, a small-volume equipment 

manufacturer can potentially use Phase 2 engines on all their Class II equipment for two years 

(consistent with the SBAR Panel’s recommendation) or they may, for example, sell half their 

Class II equipment with Phase 2 engines for four years. 

Simplified Engine Certification for Equipment Manufacturers - We are adopting a 

simplified engine certification procedure for small-volume equipment manufacturers. (As 

discussed in Section V.E.4 of the preamble, we are also adopting this provision for other 

manufacturers, regardless of the company’s size.) Generally, it has been engine manufacturers 

who certify with EPA for the exhaust emission standards because the standards are engine-based 

standards. However, because the Phase 3 standards under consideration are expected to result in 

the use of catalysts, a number of equipment manufacturers, especially those that make lowvolume models, believe it may be necessary to certify their own unique engine/muffler designs 

with EPA, but using the same catalyst substrate already used in a muffler certified by the engine 

manufacturer. In order to allow the possibility of an equipment manufacturer certifying an 

engine/muffler design with EPA, we are adopting a simplified engine certification process for 

small-volume equipment manufacturers (see §1054.612). Under such a simplified certification 

process, the equipment manufacturer will need to demonstrate that it is using the same catalyst 

substrate as the approved engine manufacturer’s family, provide information on the differences 

between their engine/exhaust system and the engine/exhaust system certified by the engine 

manufacturer, and explain why the emissions deterioration data generated by the engine 

manufacturer is representative for the equipment manufacturer’s configuration. 

Eligibility for the Small Business Flexibilities - EPA is retaining the current criteria (i.e., 

5,000 units per year of nonhandheld equipment) for determining who is a small-volume 

equipment manufacturer and, as a result, eligible for the Phase 3 flexibilities described above 

10-10 
Small-Business Flexibility Analysis 

(see §1054.801). Based on sales data, the 5,000 unit cut-off for equipment manufacturers would 

include the vast majority of the small business equipment manufacturers using SBA’s employeebased definition. However to ensure all small businesses that meet SBA’s employee-based 

definition have access to the flexibilities described above, EPA will also allow equipment 

manufacturers which exceed the production cut-off level noted above but have fewer employees 

than the SBA definition of small business (i.e., 500 employees for manufacturers of most types 

of equipment), to request treatment as a small-volume equipment manufacturer (see §1054.635). 

In such a case, the manufacturer will need to provide information to EPA demonstrating that the 

manufacturer has fewer employees than the applicable employee cut-off level established by 

SBA. 

10.7.2 Marine SI Exhaust Emission Standards—Regulatory Flexibility Options for SD/I 

Engine Manufacturers 

Described below are the regulatory alternatives being adopted with the final rule related 

to the SD/I engine exhaust emission standards. 

Additional Lead Time for SD/I Engine Manufacturers - We are adopting an 

implementation date of 2011 for #373 kW SD/I engines produced by small business marine 

engine manufacturers and a date of 2013 for small business manufacturers of high-performance 

(>373 kW) marine engines (see §1045.145). These dates provide 1 year of additional leadtime 

for small businesses producing #373 kW SD/I engines and 3 years of additional leadtime for 

small businesse producing >373 kW SD/I engines compared the implementation dates for large 

manufacturers. 

Exhaust Emission ABT - We are adopting an averaging, banking, and trading (ABT) 

credit program for exhaust emissions from #373 kW SD/I marine engines (see part 1045, subpart 

H). Under the proposal, the ABT program would have applied to >373 kW SD/I engines as well. 

However, as described in section 3.4 of the Summary and Analysis of Comments document for 

the Final Rule, we are adopting different standards for high performance SD/I engines than 

originally proposed. High performance (>373 kW) SD/I engines are required to meet the new 

standards without the use of an ABT program. 

Early Credit Generation for ABT - We are adopting an early banking program in which 

bonus credits can be earned for certifying early (see §1045.145). This program, combined with 

the additional lead time for small businesses noted above, give small-volume manufacturers of 

SD/I engines #373 kW ample opportunity to bank emission credits prior to the implementation 

date of the standards and provide greater incentive for more small business engine manufacturers 

to introduce advanced technology earlier than would otherwise occur. Because the ABT 

program being adopted with the final rule only applies to SD/I engines #373 kW, the early credit 

provisions will not apply to high-performance (>373 kW) SD/I engines. 

Assigned Emission Rates for High Performance (>373 kW) SD/I Engines - In the 

proposal, we noted that in the case where an engine manufacturer is using emission credits to 

comply with the standard, the manufacturer will still need to test engines to calculate how many 

10-11 
Final Regulatory Impact Analysis 

emission credits are needed. In order to minimize this testing burden, we proposed to allow 

manufacturers to use assigned baseline emission rates for certification based on previously 

generated emission data. As discussed in section 3.4 of the Summary and Analysis of Comments 

document for the Final Rule, we are adopting less stringent standards for high-performance 

(>373 kW) SD/I engines that do not allow for the use of the ABT program for demonstrating 

compliance with the standards. Therefore, we are not adopting baseline HC+NOx and CO 

emission rates for high-performance SD/I engines since the proposed levels were higher than the 

standards being adopted and therefore, are of no use without an ABT program. 

Alternative Standards for High Performance (>373 kW) SD/I Engines - In the 

proposal, EPA cited concerns raised by small businesses that catalysts had not been 

demonstrated on high-performance engines and that they may not be practicable for this 

application and therefore requested comments on the need for and level of alternative standards 

for high-performance marine engines. As described in section 3.4 of the Summary and Analysis 

of Comments document for the Final Rule, we are adopting a less stringent set of exhaust 

emission standards for high performance (>373 kW) SD/I engines than originally proposed. 

These standards are not expected to result in the use of catalysts on high performance (>373 kW) 

SD/I engines. 

Furthermore, we are not adopting NTE standards for high-performance SD/I engines (See 

§1045.105). This is consistent with the SBAR Panel recommendation that NTE standards not 

apply to any high-performance SD/I engines. 

Broad Engine Families for High Performance (>373 kW) SD/I Engines - Typically in 

EPA engine and equipment programs, manufacturers are able to group their engine lines into 

engine families for certification to the standards. Engines in a given family must have many 

similar characteristics including the combustion cycle, cooling system, fuel system, air 

aspiration, fuel type, aftertreatment design, number of cylinders and cylinder bore sizes. A 

manufacturer would then only perform emission tests on the engine in that family that would be 

most likely to exceed an emission standard. We are adopting provisions that allow small 

businesses to group all of their high performance (>373 kW) SD/I engines into a single engine 

family for certification, subject to good engineering judgment (see §1045.230). A manufacturer 

will need to perform emission tests only on the engine design that will be most likely to exceed 

the emission standard. 

Simplified Test Procedures for High Performance (>373 kW) SD/I Engines - Existing 

testing requirements include detailed specifications for the calibration and maintenance of testing 

equipment and tolerances for performing the actual tests. For high performance (>373 kW) SD/I 

engines, it may be difficult to hold the engine at idle or high power within the tolerances 

currently specified by EPA in the test procedures. Therefore, we are adopting less restrictive 

specifications and tolerances, for small businesses testing high performance (>373 kW) SD/I 

engines, which would allow the use of portable emission measurement equipment (see 

§1065.901(b)). This will facilitate less expensive testing for these small businesses without 

having a negative effect on the environment. 

10-12 
Small-Business Flexibility Analysis 

Reduced Testing Requirements for SD/I Engine Manufacturers - We are adopting 

provisions to allow small-volume engine manufacturers to use an assigned deterioration factor to 

demonstrate compliance with the standards for the purposes of certification rather than doing 

service accumulation and additional testing to measure deteriorated emission levels at the end of 

the regulatory useful life (see §1045.240). EPA is not specifying actual levels for the assigned 

deterioration factors in this final rule. EPA intends to analyze available emission deterioration 

information to determine appropriate deterioration factors for SD/I engines. The data will likely 

include durability information from engines certified to California ARB's standards and may also 

include engines certified early to EPA's standards. Prior to the implementation date for the SD/I 

standards, EPA will provide guidance to engine manufacturers specifying the levels of the 

assigned deterioration factors for small-volume engine manufacturers. 

We proposed to exempt small-volume manufacturers of SD/I engines from the 

production -line testing requirements. As noted in section 3.10 of the Summary and Analysis of 

Comments document for the Final Rule, we are dropping the production-line testing 

requirements for all engine manufacturers including large manufacturers. Therefore, no 

production-line testing will be required of any SD/I engine manufacturer (see §1045.301). 

Eligibility for the Small Business Flexibilities - For purposes of determining which 

engine manufacturers are eligible for the small business flexibilities described above for SD/I 

engine manufacturers, we are adopting criteria based on the number of employees. SD/I engine 

manufacturers that have no more than 250 employees will be considered a small business for the 

purposes of the flexibilities being adopted with the final rule. We originally proposed criteria 

based on a production cut-off of 5,000 SD/I engines per year. However, engine manufacturers 

commented that it was more appropriate to use an employee level than a production level for 

defining which companies are small businesses. We believe a 250 employee limit should be 

roughly consistent with the production level we targeted in our proposal, although some 

manufacturers would likely be able to produce more than 5,000 units. Under the small-volume 

engine manufacturer definition being adopted for the final rule, there will be no option to 

consider the production volume instead of the 250 employee count. 

10.7.3 Small SI and Marine SI Evaporative Emission Standards— Flexibility Alternatives 

for Equipment, Vessel, and Fuel Tank Manufacturers 

Described below are the regulatory alternatives being adopted with the final rule related 

to the evaporative emission standards for Small SI engines and equipment and Marine SI engines 

and vessels. The provisions discussed below applied to Small SI equipment and to SD/I marine 

vessels, except where noted. Because the majority of fuel tanks produced for the Small SI 

equipment and the SD/I marine vessel market are made by small businesses, the flexibility 

provisions being adopted for fuel tank manufacturers apply regardless of whether the 

manufacturer was a small business or not. 

Consideration of Appropriate Lead Time - We are adopting an implementation schedule 

that we believe provides sufficient lead time for blow-molded and marine rotational molded fuel 

tanks. For Small SI equipment, we are establishing tank permeation implementation dates of 

10-13 
Final Regulatory Impact Analysis 

2011 for Class II equipment and 2012 for Class I equipment. For marine fuel tanks, we are 

implementing the tank permeation standards in 2011 with an additional year (2012) for installed 

fuel tanks which are typically rotational-molded marine fuel tanks (see §1054.110 and 

§1045.107). 

With regard to the diurnal requirements for marine vessels, we are providing an 

additional year of lead time, compared to the proposal. This means that the diurnal standard 

willll apply beginning with the 2011 model year. In addition, we are adopting an interim 

allowance program that will give additional time for a limited number of boats. Under this 

program, each boat builder will be allowed to sell these boats without the diurnal emission 

controls that would otherwise be required. Specifically, each boat builder will have a total of 

1,200 allowances that may be used, at the manufacturer's discretion, for boats produced before 

December 31, 2012. These allowances are intended to help boat builders engage in an orderly 

transition to the new standards and will only be available for boats produced in 2011 and 2012. 

This allowance program applies only to boats with installed fuel tanks that are expected to use 

carbon canisters to meet the diurnal emission standards. Therefore, it does not apply to portable 

fuel tanks or personal watercraft. This provision will apply to both small and large businesses 

because we believe that even large businesses may have specific, small-volume models where 

additional lead time may be especially helpful due to atypical design constraints. For very small 

companies, we expect that this allowance program will result in an additional year, or even two, 

of lead time for them to address potential installation issues related to carbon canisters. 

Fuel Tank ABT and Early Incentive Program - We are adopting an ABT program for 

fuel tank permeation and an early-allowance program for fuel tank permeation. In the proposal, 

we requested comment on including service tanks in the ABT program. (Service tanks are fuel 

tanks sold as replacement parts for in-use equipment.) Based on comments received, we do not 

believe it is appropriate to include such tanks in the ABT program. Equipment manufacturers 

will be required to demonstrate that their equipment models meet the evaporative emission 

standards. If the certified equipment uses a fuel tank included in the ABT program, the credits 

generated were based on a useful life of five years. Therefore, if the tank being replaced is less 

than five years old, the replacement tank would result in double counting of some of the credits. 

While manufacturers could potentially gather information to account for the age of the fuel tank 

being replaced, we do not want to complicate the provisions of the ABT program and therefore 

we are not including replacement tanks in the fuel tank ABT program. 

Broad Definition of Evaporative Emission Family for Fuel Tanks - We are adopting 

provisions that allow fuel tank emission families to be based on type of material (including 

additives such as pigments, plasticizers, and UV inhibitors), emission control strategy, and 

production methods. This would allow fuel tanks of different sizes, shapes, and wall thicknesses 

can be grouped into the same emission family (see §1045.230 and §1054.230). In addition, 

Small SI and Marine SI fuel tanks could be allowed in the same emission family if the tanks 

meet these criteria. Manufacturers therefore will be able to broadly group similar fuel tanks into 

the same emission family and then only test the configuration most likely to exceed the emission 

standard. 

10-14 
Small-Business Flexibility Analysis 

Compliance Progress Review for Marine Fuel Tanks - We believe the 2012 fuel 

permeation standards are technologically feasible for rotationally-molded marine fuel tanks. 

This conclusion is supported by data presented in the Regulatory Impact Analysis. In addition, 

several rotationally-molded tank manufacturers support EPA's proposed standards and 

implementation dates and have provided information to support their positions. However, 

several other rotationally-molded tank manufacturers are not as far along in their technological 

progress toward meeting the standards and are not certain about their ability meet the EPA 

requirements in 2012. To address this situation, these manufactures requested that EPA perform 

a technical review in 2010 to determine whether the compliance dates should be adjusted. 

However, for the reasons discussed above, we believe that the tank permeation standards have 

been demonstrated to be technologically feasible in the 2012 time frame and do not look 

favorably upon the request for a technology review of the permeation standard. 

Nevertheless, we are concerned about the potential long-term impacts on the small 

businesses that have not yet developed technology that meets the requirements. During the next 

few years, EPA intends to hold periodic progress reviews with small businesses that rotationally 

mold fuel tanks. The purpose of these progress reviews will be to monitor the progress of 

individual companies towards compliance with the tank permeation standards and to provide 

feedback as needed. Rather than conducting a broad program with the entire industry, we will 

conduct separate, voluntary reviews with each interested company. These sessions will be 

instrumental to EPA in following the progress for these companies and assessing their efforts 

and potential problems. 

To help address small business concerns, we expect we would rely on the small volume 

manufacturer hardship relief provisions contained in 40 CFR 1068.250, and described in the 

following section. In the event that a small business is unsuccessful in the 2012 model year and 

seeks hardship relief, the progress reviews described above would provide an important 

foundation in determining whether a manufacturer has taken all steps to comply with the 

permeation standards in a timely and orderly manner. 

Design-Based Certification - We are adopting design-based certification for carbon 

canisters for boats. For the carbon canisters, the design requirement call for a ratio of carbon 

volume (liters) to fuel tank capacity (gallons) of 0.04 liter/gallon for boats less than 26 feet in 

length, and 0.016 liter/gallon for larger boats. We are also adopting design-based certification 

for certain fuel tanks. For fuel tanks, we will allow design-based certification for metal tanks as 

well as plastic fuel tanks with a continuous EVOH barrier. 

The National Marine Manufacturers Association (NMMA) the American Boat and Yacht 

Council (ABYC) and the Society of Automotive Engineers (SAE) have industry recommended 

practices for boat designs that must be met as a condition of NMMA membership. We will 

allow this data to be used as part of EPA certification as long as it is collected consistent with the 

test procedures and other requirements described in this final rule. 

Additional Lead Time for Small SI Fuel Hose Requirement - We proposed an 

implementation date of 2008 for Small SI hose permeation standards for non-handheld 

10-15 
Final Regulatory Impact Analysis 

equipment (see §90.127). Given that we are not adopting the final rule until mid-2008, we have 

delayed the implementation of the low permeation fuel line requirement until 2009 for 

nonhandheld equipment. However, we are keeping the 2009 implementation date for 

low-permeation fuel line for small businesses producing Small SI nonhandheld equipment. We 

believe the 2009 date is feasible for all equipment manufacturers, given that fuel line meeting the 

low permeation standards is already widely available and manufacturers selling most types of 

nonhandheld equipment in California were required to use such hose starting in 2007 or 2008. 

10.7.4 Hardship Provisions—Regulatory Flexibility Options for Engine, Equipment, 

Vessel, and Fuel System Component Manufacturers 

The following section summarizes the hardship provisions we are adopting which would 

be available to engine manufacturers, equipment manufacturers, vessel manufacturers, and fuel 

system component manufacturers (i.e., fuel tank, fuel hose, and fuel cap manufacturers). 

Unusual Circumstances Hardship - Under the unusual circumstances hardship 

provision, manufacturers can apply for hardship relief if circumstances outside their control 

cause the failure to comply and if failure to sell the subject engines or equipment will jeopardize 

the company’s solvency (see §1068.245). The terms and time frame of the relief will depend on 

the specific circumstances of the company and the situation involved. As part of its application 

for hardship, a company will be required to provide a compliance plan detailing when and how it 

will achieve compliance with the standards. This hardship provision will be available to all 

business engine manufacturers, equipment manufacturers, vessel manufacturers, and fuel system 

component manufacturers, regardless of size. 

Economic Hardship - Under the economic hardship provision, small business 

manufacturers can petition EPA for limited additional lead time to comply with the standards 

(see §1068.250). A manufacturer will have to make the case that it has taken all possible 

business, technical, and economic steps to comply, but the burden of compliance costs will have 

a significant impact on the company’s solvency. Hardship relief may include requirements for 

interim emission reductions and/or purchase and use of emission credits. The length of the 

hardship relief will be established during the initial review and will likely need to be reviewed 

annually thereafter. As part of its application for hardship, a company will be required to 

provide a compliance plan detailing when and how it will achieve compliance with the 

standards. This hardship provision will be available only to engine manufacturers, equipment 

manufacturers, vessel manufacturers, and fuel system component manufacturers that are small 

businesses. 

10.8 Projected Economic Effects of the Rulemaking 

The following section summarizes the economic impact on small businesses of the new 

exhaust and evaporative emission standards for both Small SI engines and equipment and Marine 

SI engines and vessels. As noted earlier, the types of companies that will be affected by the new 

Marine SI standards include OB/PWC engine manufacturers, SD/I engine manufacturers, boat 

builders, and marine fuel system component manufacturers (e.g., fuel tank and fuel hose 

10-16 
Small-Business Flexibility Analysis 

manufacturers). Similarly, the types of companies that will be affected by the Small SI standards 

include nonhandheld engine manufacturers, equipment manufacturers, and Small SI fuel system 

component manufacturers (e.g., fuel tank and fuel hose manufacturers). For the purposes of this 

analysis, it is assumed that engine manufacturers will bear the cost of complying with the 

exhaust emission standards, whereas equipment manufacturers and vessel manufacturers will 

bear the cost of complying with the evaporative emission standards. 

To gauge the impact of the new standards on small businesses, EPA employed a cost-tosales ratio test to estimate the number of small businesses that would be impacted by less than 

one percent, between one and three percent, and above three percent. The costs used in this 

analysis are based on the cost estimates developed in Chapter 6 of this Final RIA with the 

exception of the costs used for Small SI engine and equipment manufacturers. A description of 

the inputs used for each affected industry sector (except small SI engine and equipment 

manufacturers) and the methodology used to develop the estimated impact on small businesses in 

each industry sector is presented in the docket for this rulemaking.2 

For small SI engine and equipment manufacturers, we relied on the costs from the 

proposal instead of the final rule. The basic cost inputs for the final rule (e.g., the cost of the 

various technologies, the number of engine and equipment models, etc.) have not changed from 

the proposal. However, recent certification data suggests that a number of Class II engines may 

be able to comply with the standards without the use of a catalyst. Our cost analysis for the final 

rule reflects this change and results in significantly lower costs for Class II. Because we project 

that more than half of the engines in Class II will use catalysts, but we do not know which 

engines small business equipment manufacturers will purchase for their equipment, we believe it 

is appropriate to continue using the higher costs associated with the proposal rather than the final 

rule cost numbers in gauging the potential costs of the new standards on small manufacturers. 

We believe this approach will result in an overestimation of the impacts (i.e., a conservative 

estimate) of the new standards on small SI engine and equipment manufacturers. 

For OB/PWC engine manufacturers, EPA identified two small businesses. One of the 

small businesses identified by EPA manufactures personal watercraft today using four-stroke 

engines with certified emission levels below the new standards, so we project negligible 

incremental costs resulting from our rule. The other small business manufactures outboard 

engines. Several of their currently certified engines already comply with the new standards, 

while the remaining engines would need to be recalibrated, which we project would cost on the 

order of less than $10 per engine. Given the cost of personal watercraft and outboard engines, 

we therefore believe the impact of the rule is well below one percent of revenues for both of 

these OB/PWC engine manufacturers. 

For <373 kW SD/I engine manufacturers, EPA identified nine small businesses. Of these 

companies, eight produce conventional SD/I engines and the remaining one company produces 

SD/I engines for airboats. Of the conventional SD/I small business engine manufacturers, five of 

the small businesses may incur compliance costs between one and three percent of their annual 

revenues. Three of the small businesses that produce <373 kW SD/I engines as part of a much 

broader line of work (such as engine rebuilding or selling land-based engines) will be impacted 

10-17 
Final Regulatory Impact Analysis 

by less than one percent of annual revenues. 

Using available information for the airboat engine manufacturer, we project that the 

manufacturer will have compliance costs between one and three percent of annual revenues. 

Some of this company’s engines are >373 kW, so their estimated compliance burden reflects a 

combination of costs for conventional SD/I engines and for high-performance >373 kW engines. 

(They are included in the conventional SD/I category for this impact analysis.) This company is 

unique in that it manufacturers many of its engines for sale to other airboat manufacturers, 

resulting in a concentrated cost impact relative to their revenues. 

We also identified a number of other airboat manufacturers. These small businesses 

making engines for airboats are less reliant on selling engines to other boat builders, instead 

making engines for the boats they build themselves. Most of these businesses are very small, 

with little ability to marshal the technical resources needed to comply with emission standards. 

If these companies would take on the effort to design and certify compliant engines, they would 

likely experience compliance costs exceeding three percent of their revenues. However, given 

their place in the market and the fact that they are primarily boat builders with the 

resourcefulness to make their own engines, we believe the most likely approach for these 

companies is to buy a certified engine from manufacturers of conventional SD/I engines. As 

such, these companies would be treated with other boat builders, in which case their main 

compliance cost is related to evaporative emissions (as described below). We therefore do not 

consider any of these companies as engine manufacturers for the purposes of analyzing the 

impact of the new standards on engine manufacturers. 

For >373 kW SD/I engine manufacturers, EPA identified 19 small businesses. Of the 

>373 kW SD/I small business engine manufacturers, all of the small businesses are projected to 

be impacted by less than one percent of annual revenues. 

For boat builders, EPA believes there are over 1,000 small business manufacturers. 

Many of these companies make small numbers of vessels for certain segments of the marine 

market. Given the high cost of most boats, EPA believes the cost impact will be below one 

percent for all small business boat builders, including those that manufacture SD/I vessels, and 

OB/PWC boat manufacturers as well. 

While boat builders have the primary responsibility under the new regulations for 

complying with evaporative emission standards, fuel hose and fuel tank manufacturers will have 

to certify their product with EPA. EPA has identified one small business that manufactures fuel 

hose for marine applications and 14 small businesses that manufacturer fuel tanks for marine 

applications. The company producing fuel hose primarily distributes hoses made by other 

manufacturers but does produce its own fill neck hose. Because we expect vessel manufacturers 

will design their fuel systems such that there will not be standing liquid fuel in the fill neck (and 

therefore the new low permeation fuel hose requirements will not apply to the fill neck), we have 

not included this manufacturer in our analysis. Of the 14 fuel tank manufacturers, EPA has 

estimated that all of them will incur costs below one percent of annual revenues. 

10-18 
Small-Business Flexibility Analysis 

For Small SI engine and equipment manufacturers, EPA has identified 370 small 

businesses.3 Ten of the small businesses are engine manufacturers and the remaining companies 

are equipment manufacturers. Based on an analysis of sales revenues by company, EPA projects 

that 314 of the small businesses are estimated to incur compliance costs representing less than 1 

percent of their annual revenues. EPA projects that 38 companies will incur compliance costs 

between 1 and 3 percent of their annual revenues, and 18 companies will incur compliance costs 

representing more than 3 percent of their annual revenues. 

Similar to the requirements noted above for boat manufacturers under the Marine SI 

evaporative emission regulations, equipment manufacturers will have the primary responsibility 

under the regulations for complying with the Small SI evaporative emission standards. 

However, fuel hose and fuel tank manufacturers will have to certify their product with EPA. 

EPA has identified two small businesses that manufactures fuel hose for Small SI applications 

and 25 small businesses that manufacturer fuel tanks for Small SI applications. Of these 

companies, EPA has estimated that all of these companies will incur costs below one percent of 

annual revenues. 

Table 10.8-1 summarizes the impacts of the new regulations on small businesses 

impacted by the exhaust and evaporative emission standards for Small SI engines and equipment 

and Marine SI engines and vessels. 

Table 10.8-1: Summary of Impacts on Small Businesses 

Market Sector 0-1 percent 1 - 3 

percent 

> 3 percent 

Manufacturers of Marine OB/PWC engines 2 0 0 

Manufacturers of Marine SD/I engines < 373 kW 4 5 0 

Manufacturers of Marine SD/I engines > 373 kW 

(high-performance) 

19 0 0 

Boat Builders >1,000 0 0 

Manufacturers of Fuel Hose and Fuel Tanks for 

Marine SI Vessels 

14 0 0 

Small SI engines and equipment 314 38 18 

Manufacturers of Fuel Hose and Fuel Tanks for 

Small SI Applications 

27 0 0 

Total 380 plus 

>1,000 boat 

builders 

43 18 

After considering the economic impacts of today's final rule on small entities, we believe 

10-19 
Final Regulatory Impact Analysis 

this action will not have a significant economic impact on a substantial number of small entities. 

The small entities directly regulated by this final rule cover a wide range of small businesses 

including engine manufacturers, equipment manufacturers, boat manufacturers, fuel tank 

manufacturers, and fuel hose manufacturers. Small governmental jurisdictions and small 

organizations as described above will not be impacted. We have determined that the estimated 

effect of the rule is to impact 43 companies with costs between one and three percent of 

revenues, and 18 additional companies with costs over three percent of revenues. These 61 

companies represent less than 5 percent of the total number of small businesses impacted by the 

new regulations. All remaining companies (over 1,000 of them) would be impacted with costs 

by less than one percent of revenues. It should be noted that this estimate is based on the highest 

level of estimated cost in the first years of the program. We estimate substantially lower 

long-term costs as manufacturers learn to produce compliant products at a lower cost over time. 

For a complete discussion of the economic impacts of the final rulemaking, see Chapter 

9, the Economic Impact Analysis chapter, of this Final Regulatory Impact Analysis. 

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Small-Business Flexibility Analysis 

Chapter 10 References 

1. Final Panel Report of the Small Business Advocacy Review Panel on EPA's Planned Proposed Rule—Control of 

Emissions from Nonroad Spark-Ignition Engines and Equipment, October 17, 2006. (A copy has been placed in 

docket EPA-HQ-OAR-2004-0008.) 

2. “Small Business Impact Memo, Control of Emissions from Nonroad Spark-Ignition Engines and Equipment -

Determination of No SISNOSE,” EPA memorandum from Phil Carlson to Alex Cristofaro, March 13, 2008. 

(Docket Identification EPA-HQ-OAR-2004-0008-____.) 

3. “Small Entity Analysis of Small Spark Ignition Nonroad Engine and Equipment Manufacturers,” memorandum 

from Alex Rogozhin and Brooks Depro, RTI Interational, to Phil Carlson, U.S. EPA, December 15, 2006. (Docket 

Identification EPA-HQ-OAR-2004-0008-0541.) 

10-21 

Regulatory Alternatives 

CHAPTER 11: Regulatory Alternatives 

Our program represents a blend of exhaust and evaporative emission standards for small 

nonroad spark-ignition (SI) engines used in land-based or auxiliary marine applications, and also 

recreational Marine SI engines. We believe that the combination of emission standards and their 

associated timing are superior to the alternative program options we considered given their 

feasibility, cost, and environmental impact. In this chapter we present and discuss the options 

that we evaluated in order to make this determination. 

Section 11.1 presents each element of our requirements and discusses a variety of 

specific alternatives that are either less and more stringent. After this initial assessment, options 

that merit a more rigorous examination are identified for analysis in subsequent sections. 

Section 11.2 describes the cost of the selected options for each affected engine or system. 

Section 11.3 presents the emissions inventory impacts associated with each option. Section 11.4 

describes the cost effectiveness ($/ton of emission reduced) of the selected options. Finally, we 

present our assessment of the rationale, feasibility, and issues associated with each alternative in 

Section 11.5. 

The costs, emission reductions, and cost effectiveness of the options analyzed in Sections 

11.2 through 11.5 are incremental to the base case (i.e., current requirements) ignoring this rule, 

unless otherwise specified. For example, the more stringent recreational marine exhaust 

standards for OB/PWC are evaluated as follow-on requirements to the new requirements and 

would begin in a later year. Therefore, the analysis for that option reflects only the more 

stringent subsequent standards. 

For the more stringent options, it is important to note that the analyses depend on data 

supporting them. Generally, a scenario was picked for analysis because there was evidence to 

suggest that controls such as those identified in the write-ups could be technically feasible at 

some point in the future. However, there is some uncertainty with regard to the technical 

feasibility of implementing the standards or requirements across all products, the level of the 

potential standards selected for analysis (if applicable), the timing for potential introduction, and 

the costs of control. However, while these standards were ultimately not selected as the basis for 

this rule, it appears that in some cases they could form the basis for potential future rulemaking 

actions. 

11.1 Identification of Alternative Program Options 

This section provides our description of potential options for each element of our rule. 

Options that do not merit further consideration are eliminated and those that warrant additional 

analysis in subsequent sections are identified. 

11-1 
Final Regulatory Impact Analysis 

11.1.1 Alternative Exhaust Emission Requirements 

11.1.1.1 Small SI Engine HC+NOx Standards 

11.1.1.1.1 Class I 

We considered, but rejected, a less stringent HC+NOx emission standard for Class I 

spark-ignition engines. The standard of 10 g/kW-hr is readily achievable with reasonably priced 

emission control technology. Furthermore, the lead time for implementing the standard in 2012 

is adequate for applying the catalyst-based technology that will be used on many of these 

engines. A less stringent emission standard would not be consistent with the requirements of 

section 213 of the Clean Air Act. 

A more stringent standard was also considered. Under this option an 8 g/kW-hr 

HC+NOx standard would be implemented. For purposes of this analysis we elected to begin the 

requirement in the 2015 model year. Due to the technical design relationship between the engine 

and running loss control requirement we modeled running loss controls to start in 2015 as well. 

This standard represents about a 50 reduction from the existing Phase 2 standard, rather than the 

approximately 38 percent reduction associated with the final standards. As analyzed this option 

also provides 3 more years of lead time. We believe that manufacturers of side-valve (SV) 

engines would choose to convert these families to overhead-valve (OHV) designs. The 

emissions from OHV engine are typically lower and deteriorate less than SV engines and thereby 

result in the need for only a slightly more active catalyst and improved cooling relative to the 

technology changes needed for the final standards. Cooling for the slightly more active OHV 

catalyst would be supplied by the engine improvements anticipated for this rule, such as include 

optimized head design for cooling and fan design for cooling air generation. The slightly more 

active catalyst can be achieved with either a larger volume and/or a more active mix of precious 

metals in the catalyst substrate. It may be possible for SV engines to meet the more stringent 

emission standards using catalysts. For SV engines the catalysts would likely need to be larger 

and more active. This would result in higher costs and greater catalyst heat generation which 

may or may not be able to be handled by the engine’s cooling system. 

11.1.1.1.2 Class II 

For Class II spark-ignition engines, we considered an alternative program option that was 

less stringent than the final standards. However, for the same reasons previously stated for Class 

I engines, we rejected this alternative from further consideration; the standards are readily 

achievable at a reasonable cost within the lead time provided. A less stringent standard, such as 

one at a level not depending on catalyst technology, would not have been consistent with section 

213 of the Clean Air Act. 

An alternative for a more stringent exhaust HC+NOx emission standard would be 4.0 

g/kW-hr along with a delay in the corresponding running loss requirement such that engine 

changes are made at one time. For analytical purposes we started this requirement in 2015, four 

years beyond that for the new standard. Such an exhaust emission standard represents a 67 

11-2 
Regulatory Alternatives 

percent reduction relative to the existing Phase 2 standard, rather than the 34 percent reduction 

associated with the new standards. It also provides four more years of lead time; a phase-in 

could be needed since implementation would require the equipment manufacturers involvement 

for non-integrated products. In order to achieve the 4.0 g/kW-hr HC+NOx emission standard, 

we expect manufacturers would need to make widespread use of closed loop control EFI and 

three-way catalysts. The EFI systems would keep engine air-to-fuel mixture closer to 

stoichiometry and provide an optimum environment for the maximum reduction in HC+NOx by 

a three way catalyst. Changes to the catalyst would likely involve a more active mix of precious 

metals in the catalyst substrate. In addition, engine upgrades would be required in some of the 

Class II engines commonly used in residential lawn care equipment. 

11.1.1.2 Marine Auxiliary Engine CO Standard 

The standards for marine auxiliary engines include a CO standard that would require the 

use of highly efficient catalytic control. This standard would require the use of technology to 

meet emission levels demanded by the market. Manufacturers of gasoline marine generators are 

equipping their engines with catalysts for the primary purpose of reducing ambient CO 

concentrations around boats. Therefore, we do not believe that it would be useful to consider a 

less stringent standard which could enable market penetration of new engine offerings which 

potentially endanger public health. At the same time, the standard is very stringent and 

manufacturers are already designing for reductions which are more than 95 percent below the 

current CO emission standard. A more stringent standard would do little more to push 

technology. Thus, we do not believe that it would be useful to analyze a more stringent standard. 

11.1.1.3 Outboard/Personal Watercraft (OB/PWC) Engine HC+NOx and CO 

Emission Standards 

The standards for OB/PWC are based on technology that manufacturers are already 

certifying and selling nationwide. To meet the new requirements, manufacturers would continue 

to sell this technology and discontinue their sale of high-emitting old technology carbureted twostroke engines. Because the standards can be met with existing technology, we do not believe 

that there is an alternative between the new standards and the current standards which would be 

consistent with the CAA section 213 requirement. Therefore, we did not analyze a less stringent 

alternative. 

For a more stringent alternative, we considered an addition tier of standards beginning in 

2012. For OB/PWC engines greater than 40 kW these would be at a level of 10 g/kW-hr. For 

engines less than 40 kW, we use an equation of 28 - 0.45 × rated power(kW) to maintain a 

continuous curve function. This alternative also considers a lower CO standard of 200 g/kW-hr 

for engines greater than 40 kW with an adjusted standard of 500 - 7.5 × rated power(kW) for 

engines less than 40 kW to maintain a continuous standard function. Such standards would be 

consistent with currently certified emission levels from some four-stroke outboard engines. 

Although many four-stroke engines may be able to meet a 10 g/kW-hr standard with improved 

engine calibration, it is not clear that all engines could meet this standard without applying yet 

unproven catalyst technology in this application. To model this scenario, we evaluated the costs 

11-3 
Final Regulatory Impact Analysis 

and emission reductions that could be achieved through the combined use of calibrated fourstroke engines and four-stroke engines with catalytic control. This analysis applied catalytic 

control to larger OB/PWC engines, which already use or are expected to use electronic fuel 

injection. 

11.1.1.4 Sterndrive/Inboard (SD/I) Engine HC+NOx and CO Standards 

For the purposes of this analysis, we subdivided the SD/I category into traditional and 

high-performance engine categories. Based on our definitions, high-performance engines have 

a rated power greater than or equal to 373 kW (500 hp). 

11.1.1.4.1 SD/I <373 kW 

In developing regulatory alternatives for SD/I engines, we considered both what was 

achievable without catalysts and what could be achievable with larger, more efficient catalysts 

than those we evaluated in our test programs. 

With regard to a less stringent option, we considered non-catalyst based standards to be 

implemented in the 2010 model year. Chapter 4 presents data on SD/I engines equipped with 

exhaust gas recirculation (EGR). HC+NOx emission levels below 10 g/kW-hr were achieved for 

each of the engines. CO emissions ranged from 25 to 185 g/kW-hr. For this less stringent 

alternative, we consider standards of 10 g/kW-hr HC+NOx and 150 g/kW-hr CO. The current 

California HC+NOx standard for these engines is 160 g/kW-hr. 

For a more stringent option, we considered more stringent catalyst-based standards. 

Many of the SD/I marine engines with catalysts described in Chapter 4 had HC+NOx emission 

rates appreciably below 5 g/kW-hr, even with deteriorated catalysts. In the development testing 

for this rulemaking, we did not investigate larger catalysts for SD/I applications. The goal of the 

development testing was to demonstrate catalysts that would work within the packaging 

constraints associated with water jacketing the exhaust and fitting the engines into engine 

compartments on boats. However, we did perform testing on engines equipped with both 

catalysts and EGR. These engines showed emission results in the 2-3 g/kW-hr range. We 

expect that these same reductions could be achieved more simply through the use of larger 

catalysts or catalysts with higher precious metal loading. As a more stringent regulatory 

alternative, we considered a standard of 2.5 g/kW-hr HC+NOx, with no change in the CO 

standard, based on the use of larger catalysts. To account for additional development work that 

would need to be performed by manufacturers to achieve a lower standard than the existing 

California standard, we consider a later implementation date of 2012 for this more stringent 

alternative with no standard before that time. 

11.1.1.4.2 SD/I $373 kW 

For high-performance SD/I marine engines, we originally proposed a standard based on 

the use of catalysts and then considered a less stringent alternative based on engine fuel system 

upgrades, calibration, or other minor changes such as an air injection pump rather than catalytic 

control. However, manufacturers commented that catalysts are not be practical for these engines 

11-4 
Regulatory Alternatives 

due to the high exhaust flow rates, high emission rates, and low useful life period between 

rebuild. In the final rule, we are establishing standards that can be met through the use of engine 

controls, similar to the alternative standard that was analyzed in the proposal. Because we do not 

consider catalyst-based standards to be feasible for high-performance engines at this time, we are 

not modeling a more stringent alternative. 

11.1.2 Alternative Evaporative Emission Requirements 

11.1.2.1 Small SI Engines 

For Small SI engines, we are finalizing both permeation and venting emission standards. 

The permeation standards are for fuel tanks and fuel lines. We believe that the standards are 

reflective of available technology and represent a step change in emissions performance. Venting 

emissions include diurnal breathing losses, diffusion, and running loss emissions. For nonhandheld Small SI engines (i.e., Classes I and II), we are finalizing standards for running loss1 

but not for diurnal emissions. We are not finalizing any type of venting emissions control for 

handheld equipment. 

For a less stringent alternative, we considered not requiring running loss emission control 

for non-handheld Small SI engines. These requirements would be deleted from the rule and thus 

modeled as being deleted in the years otherwise required. 

For a more stringent alternative, we considered applying running loss and diurnal 

standards to handheld equipment and setting a diurnal standard for non-handheld (Classes I and 

II). In these alternatives, we consider an implementation date of 2012 for handheld and Class I 

equipment, and a date of 2011 for Class II equipment. 

11.1.2.2 Marine 

Similar to the analysis described above for Small SI equipment, we base the less stringent 

and more stringent regulatory alternatives on changes in the venting emission standards. For 

marine vessels, we are adopting diurnal emission standards for all vessel types. For portable fuel 

tanks and PWC fuel tanks, the control technology of a sealed system with pressure relief is fairly 

straightforward and commonly used today. However, we anticipate that the diurnal emissions 

standards for vessels with installed fuel tanks would be based on the use of passively purged 

carbon canisters. For a less stringent alternative, we consider not setting a diurnal emission 

standard for marine vessels.2

 For a more stringent scenario, we consider a diurnal requirement 

wherein boat builders would be required to employ active purge of carbon canister with installed 

tanks. This means that, when the engine is operating, it would draw air through the canister to 

purge the stored hydrocarbons. These purged gasoline vapors would be used in the engine as 

1

 We anticipate that running loss control measures will also reduce diffusion emissions. 

2

Note that PWC already meet the standard and would not be affected differently for the less 

stringent standard. PWC use sealed systems with pressure relief to prevent fuel spillage during operation. 

11-5 
Final Regulatory Impact Analysis 

fuel. 

11.1.3 Summary of Alternative Standards 

Table 11.1-1 and Table 11.1-2 show the alternative program options that were selected 

above for further consideration. 

Table 11.1-1: Exhaust Alternative Program Options for Quantitative Analysis 

Source Alt Target Standard less/ 

more 

Alternative Description 

Exhaust 1 Class I C 10 g/kW-hr HC+NOx 

C Begins 2012 

more C 8 g/kW-hr HC+NOx 

C Begins 2015 in lieu of standard 

2 Class II C 8 g/kW-hr HC+NOx 

C Begins 2011 

more C 3.5 g/kW-hr HC+NOx 

C Begins 2015 in lieu of standard 

3 OB/PWC C Decreases with power 

output (P) 

C 2008 California 

HC+NOx equation 

C CO g/kW-hr equation 

is 500-5Pfor <40 kW 

C 300 g/kW-hr CO for 

>40kW 

C Begins 2010 

more < 40kW 

C power output (P) 

C HC+NOx g/kW-hr equation is 28-0.45P 

C COg/kW-hr equation is 500-7.5P

 > 40 kW 

C 10 g/kW-hr HC+NOx 

C 200 g/kW-hr CO 

CBoth begin 2012 in addition to 2010 

standards 

4 SD/I 

<373 kW 

C 5 g/kW-hr HC+NOx 

C 75 g/kW-hr CO 

C Begins 2010a 

less C 10 g/kW-hr HC+NOx 

C 150 g/kW-hr CO 

C Same effective dates as standard 

5 more C 2.5 g/kW-hr HC+NOx 

C 75 g/kW-hr CO 

C Begins 2012 in lieu of standardsa 

a

 2011 for certain engine blocks. Does not include small business flexibilities that will delay the effective date of the 

requirements for some companies. 
Regulatory Alternatives 

Table 11.1-2: Evaporative Alternative Program Options for Quantitative Analysis 

Source Alt Target Standard less/ 

more 

Alternative Description 

Evap 6 HH 

diurnal/ 

running 

loss 

C None more C Begins 2012 

7 Class I 

& Class 

II 

running 

loss 

C Running loss is a 

“zero emission” design 

standard 

C Class I begins 2012 

and Class II begins 

2011 

less C No running loss 

8 Class I C None more C Requirement would begin in 2012 for Class 

& Class I and 2011 for Class II 

II diurnal 

9 Installed C 0.4g/gal/day HC less C No diurnal for 2010 

marine trailerable boat 

fuel tank 

diurnal 

C 0.16 g/gal/day HC 

non-trailerable boat 

C Begins 2011 

10 more C More stringent test procedure. If charcoal 

canister is used, active purge required. 

C Would begin 2011 

11 Portable 

marine 

fuel tank 

diurnal 

C Diurnal is a “zero 

emission” design 

standard 

C Begins 2010 

less C No diurnal 

11.2 Cost per Engine 

This section describes the estimated cost of complying with the alternative program 

options. We developed the costs for individual technologies using estimates from ICF 

Incorporated,1,2,3 conversations with manufacturers, other information including the published 

literature, and our best technical judgment. Also, the cost estimates for the alternatives rely 

heavily on the methodology and in some cases the actual cost data, used to characterize the 

standards. For ease of presentation, we have not repeated the methodology or those detailed 

cost data here. Instead, we focus on presenting information regarding the requirements or 

changes that we expect will be needed to comply with the alternative options. The reader is 

encouraged to refer to Chapter 6 for more information. Finally, we did not specifically analyze 

the incremental costs of setting standards which would not result in technology which would 

allow certification in all 50 states (a harmonized program). 

The costs of complying with the alternative program options are presented as 

incremental to the base case (current requirements) without considering the final standard. The 

only exception to this is the second phase of OB/PWC standards where costs are incremental to 

the final standard. The alternatives and the requisite technology are described in Section 11.1. 

Further, results are provided as the average cost per affected engine and the total net present 

value (NPV) for a 30-year period beginning in 2008. The NPV estimates are based on a seven 

11-7 
Final Regulatory Impact Analysis 

percent discount rate. All costs are in 2005 dollars. 

11.2.1 Costs for Exhaust Emission Standards 

11.2.1.1 More Stringent Small SI Engine HC+NOx Standards 

11.2.1.1.1 Class I 

Meeting more stringent standards would require OHV engines to use a slightly larger or 

more active catalyst than for the final standards. For current SV engines they would need to 

utilize larger and more active catalysts than considered in the analysis for the final standards, or 

convert to OHV design and use a slightly larger catalyst or more active catalyst than for the 

final standards.

 The cost for the SV sized catalyst is outlined in Chapter 6. The cost for the conversion 

from SV to OHV design is drawn from ICF International’s 2006 report “Small SI Engine 

Technologies and Costs4,” and is listed as $9.42 in variable costs per engine, $2,010,147 in 

tooling changes and design and development, as well as $15 million in facility upgrades per 

Class I SV engine family. The 2005 EPA certification database lists five SV engine families 

certified to Phase 2 of which two engines have OHV engine designs in the same power range 

and one engine family is listed as a small volume engine family. The remaining two engine 

families have sales estimates in the millions of engines. As a result, fixed costs are applied two 

engine families and variable costs are applied to all SV engines. 

The cost for improvements in OHV current engine designs includes improved cylinder 

head design for improved engine cooling, redesign of the engine flywheel to provide optimum 

cooling for the catalyst muffler as well as carburetor improvements. Research and development 

and tooling for these changes are estimated at $456,450 per engine family as shown in Chapter 

6. 

Upgrades in catalysts for OHV engines include additional precious metal for more 

active catalysts. The catalyst estimates for the SV engine families, that are replaced by OHV 

engine families, are also replaced with the OHV catalyst costs. These costs for improved OHV 

engines, upgraded catalysts for OHV engines are included in Table 11.2-1 together with those 

for SV engines. 

11.2.1.1.2 Class II 

Technologies for the more stringent option include improved engine design (redesign of 

cooling fins, fan design, combustion chamber design), closed loop control electronic fuel 

injection (EFI), catalysts and pressurized oil lube system for engines intended for residential 

use. The fixed costs for improved engine design are $456,000 per engine family and include 

R&D and tooling costs, as listed in Chapter 6. The same Chapter lists EFI variable costs at $79 

per engine when it includes the credit for the removal of the carburetor. The fixed costs for 

closed loop fuel injection design is estimated at $103,000 per engine family. Increased catalyst 

11-8 
Regulatory Alternatives 

efficiency is achieved through use of a larger catalyst and increased precious metal loading at 

an estimated increased catalyst cost of $4 (1000 hr engine) - $16 (250 hr engine) per engine. A 

pressurized lube oil system is listed by ICF5

 to be $15.48 in variable costs and $210,000 in fixed 

costs per engine family for the residential engines which often do not use it in today’s design. 

Overall, fuel savings would be increased due to the application of electronic fuel injection to all 

Class II engines. 

Table 11.2-1: Small SI Per-Engine Cost Estimates (Without Fuel Savings) 

Sales Weighted Averages 

Short Term (years 1-5) Long Term (years 6-10) 

Standard 

Class I 

Class II 

$10-$26 

$17-$60 

$10-$12 

$12-$30 

More Stringent

 Class I

 Class II 

$17-$23 

$110-$149 

$12-$18 

$76-$89 

11.2.1.2 Outboard/Personal Watercraft (OB/PWC) Engine HC+NOx and CO 

Emission Standards 

We believe that, to meet the more stringent alternative considered here, manufacturers 

would need to convert their product lines primarily to a mix of calibrated four-stroke engines 

and engines equipped with catalysts. To model this approach, we looked at a technology mix 

that would achieve the 10 g/kW-hr HC+NOx limit, with appropriate considerations given to 

emissions deterioration rates and compliance margins. This technology mix was developed by 

assuming that all carbureted two-stroke engines would be removed from the fleet and replaced 

with four-stroke engines. All engines over 75 kW (100 hp) were modeled as using catalytic 

control. Detailed costs for converting engines from two-stroke to four-stroke and for equipping 

OB/PWC engines with catalysts are presented in Chapter 6. Table 11.2-2 compares the average 

per-engine equipment costs for the primary and the more stringent alternatives for OB/PWC 

engines. 

11-9 
Final Regulatory Impact Analysis 

Table 11.2-2: OB/PWC Per-Engine Cost Estimates (Without Fuel Savings) 

Sales Weighted Averages 

Short Term (years 1-5) Long Term (years 6-10) 

Standard OB

 PWC 

$291 

$359 

$224 

$272 

More Stringent OB

 PWC 

$388 

$528 

$275 

$392 

Incremental Costa OB

 PWC 

$102 

$169 

$51 

$120 

a Incremental cost is presented here because the more stringent alternative for OB/PWC includes the primary 

standard in 2010 plus a second, more stringent, standard in 2012. 

We did not model differences in fuel savings between the primary and more stringent 

alternatives. The fuel savings for all three alternatives primarily come from the replacement of 

carbureted two-stroke engines with cleaner engine designs. In both the primary and more 

stringent scenarios, we model the discontinuation of sales of carbureted two-stroke engines. 

11.2.1.3 Sterndrive/Inboard (SD/I) Engine HC+NOx and CO Emission Standards 

With regard to the less stringent alternative, Chapter 4 presents costs for using exhaust 

gas recirculation (EGR) on SD/I engines. To estimate the costs for the less stringent alternative, 

all SD/I engines less than 373 kW were modeled to be equipped with electronic closed loop 

control fuel injection and EGR. 

For the more stringent case, we consider a larger catalyst size with a higher precious 

metal loading for engines. Specifically, for engines less than 373 kW, we model a 25 percent 

larger catalyst and an additional 25 percent precious metal loading. We do not model a 

difference in fuel consumption for any of these scenarios because, in each case, all engines are 

anticipated to use electronic fuel injection. Table 11.2-3 compares the per-engine cost estimates 

for the primary, less stringent, and more stringent alternatives. As discussed above, we do not 

including high-performance engines in this analysis. 

Table 11.2-3: SD/I <373 kW Per-Engine Cost Estimates (Without Fuel Savings) 

Sales Weighted Averages 

Short Term (years 1-5) Long Term (years 6-10) 

Standard $355 $266 

Less Stringent $200 $149 

More Stringent $431 $333 

11-10 
Regulatory Alternatives 

11.2.2 Costs for Evaporative Emission Standards 

11.2.2.1 Small SI Engine 

For the less stringent case, we simply subtract the costs of running loss controls for nonhandheld equipment. For the more stringent case, we add the incremental costs of diurnal 

emission control for all nonhandheld engines and diurnal emission and running loss control for 

handheld engines. These technology costs are presented in Chapter 6. Table 11.2-4 compares 

the per-equipment cost estimates for the primary, less stringent, and more stringent alternatives. 

Table 11.2-4: Evaporative Small SI Per-Equipment Cost Estimates (Without Fuel Savings) 

Sales Weighted Averages 

Short Term (years 1-5) Long Term (years 6-10) 

Standard Aggregate

 Handheld

 Class I

 Class II 

$3.27 

$0.82a 

$3.05 

$6.73 

$2.46 

$0.69a 

$2.20 

$5.16 

Less Stringent 

Aggregate

 Handheld

 Class I

 Class II 

$1.86 

$0.82a 

$1.13 

$4.50 

$1.34 

$0.69a 

$0.67 

$3.38 

More Stringent Aggregate

 Handheld

 Class I

 Class II 

$6.76 

$4.40 

$6.01 

$11.08 

$5.25 

$3.55 

$4.57 

$8.64 

a

 Values reflect the final permeation standards. These costs are used in the alternative analysis 

only to develop aggregate values for comparison purposes. 

11-11 
Final Regulatory Impact Analysis 

Table 11.2-5 presents the fuel savings for the three alternatives, based on the 

evaporative emission reductions for each of the scenarios. Because evaporative emissions are 

basically gasoline vapor lost to the atmosphere, these hydrocarbon reductions can be directly 

translated to gasoline savings using a gasoline cost of $1.81 per gallon. Cost savings are 

presented both with a 3 percent and a 7 percent discount factor over the life of the equipment. 

Table 11.2-5: Projected Evaporative Fuel Savings for Small SI Equipment 

Sales Weighted Averages 

Lifetime Gallons Saved Discounted Cost Savings 

3 percent 7 percent 

Standard Aggregate

 Handheld

 Class I

 Class II 

1.4 

0.2 

0.8 

4.7 

$2.36 

$0.33 

$1.41 

$6.53 

$2.17 

$0.31 

$1.31 

$5.96 

Less Stringent 

Aggregate

 Handheld

 Class I

 Class II 

0.9 

0.2a 

0.5 

3.0 

$1.53

 $0.33a 

$0.92 

$4.16 

$1.41

 $0.31a 

$0.85 

$3.80 

More Stringent Aggregate

 Handheld

 Class I

 Class II 

1.5 

0.3 

0.9 

5.3 

$2.63 

$0.49 

$1.53 

$7.32 

$2.41 

$0.46 

$1.41 

$6.69 

a Values reflect the final permeation standards. These costs are used in the alternative analysis only to develop 

aggregate values for comparison purposes. 

11-12 
Regulatory Alternatives 

11.2.2.2 Marine 

For the less stringent case, we simply subtract the costs of diurnal emission controls 

from marine vessels with installed and portable fuel tanks. For the more stringent case, we add 

the incremental costs of actively purged diurnal emission control for vessels with installed fuel 

tanks. These technology costs are presented in Chapter 6. Table 11.2-6 compares the perequipment cost estimates for the primary, less stringent, and more stringent alternatives. Cost 

savings are presented both with a 3 percent and a 7 percent discount factor over the life of the 

vessel. 

Table 11.2-6: Per-Vessel Cost Estimates (Without Fuel Savings) 

Sales Weighted Averages 

Short Term (years 1-5) Long Term (years 6-10) 

Standard Aggregate

 portable

 PWC

 installed 

$55 

$12 

$17 

$74 

$45 

$8 

$11 

$62 

Less Stringent Aggregate

 portable

 PWC

 installed 

$33 

$11 

$17a 

$42 

$27 

$7 

$11a 

$36 

More Stringent Aggregate

 portable

 PWC

 installed 

$69 

$12a 

$17a 

$94 

$56 

$8a 

$11a 

$77 

a Values reflect the final permeation and diurnal standards. These costs used in the alternative analysis only to 

develop aggregate values for comparison purposes. 

11-13 
Final Regulatory Impact Analysis 

Table 11.2-7 presents the fuel savings for the three alternatives. These fuel savings are 

based on the evaporative emission reductions for each of the scenarios. Because evaporative 

emissions are basically gasoline vapor lost to the atmosphere, preventing these hydrocarbon 

emissions can be directly translated to gasoline savings using a gasoline cost of $1.81 per 

gallon. 

Table 11.2-7: Projected Evaporative Fuel Savings for Marine Vessels 

Sales Weighted Averages 

Lifetime Gallons Saved Discounted Cost Savings 

3 percent 7 percent 

Standard Aggregate

 portable

 PWC

 installed 

28 

13 

9 

38 

$42 

$20 

$14 

$54 

$33 

$17 

$12 

$42 

Less Stringent 

Aggregate

 portable

 PWC

 installed 

20 

11 

9a 

26 

$30 

$17

 $14a 

$37 

$24 

$14

 $12a 

$29 

More Stringent Aggregate

 portable

 PWC

 installed 

30 

13a 

9a 

39 

$44

 $20a

 $14a 

$57 

$34

 $17a

 $12a 

$44 

a Values reflect the final permeation and diurnal standards. These costs used in the alternative analysis only to 

develop aggregate values for comparison purposes. 

11-14 
Regulatory Alternatives 

11.2.3 Cost Summary of Regulatory Alternatives 

Table 11.2-8 summarizes the average cost per engine for the various alternative program 

options described above. The costs presented are for the short term and do not include fuel 

savings. 

Table 11.2-8: Engine Cost Summary Range for Alternative Program Options ($/Engine) 

Sales Weighted Averages of Short-Term Costs without Fuel Savings, 2005$ 

Source Alt Target Standard Scenario Alternative 

Exhaust 1 Class I $10-$26 more $17-$23 

2 Class II $17-$60 more $110-$149 

3a OB/PWC $- more $70 

4 SD/I <373 kW $360 less $216 

5 more $435 

Evap 6b HH $- more $3.58 

7 Class I & Class II $4.32 less $2.30 

8b Class I & Class II $- more $3.45 

9 Installed marine fuel 

tank 

$74 less $42 

10 more $94 

11 Portable marine fuel tank $12 less $11 

a Costs are presented incremental to the standards for OB/PWC because, for this alternative, a second stage of 

standards is considered in 2012 beyond the final standards. b Only considers standards for venting emission control which are not in the final standards. The venting emission 

standards considered here are diurnal for Class I and Class II and diurnal/running loss for handheld. 

Table 11.2-9 summarizes the 30-year net present value for costs for the standards and 

the various alternative program options described in Table 11.2-1. Cost results are provided as 

the total net present value (NPV) for a 30-year period. The NPV estimates are based on a 7 

percent discount rate. These costs do not include fuel savings. Table 11.2-10 presents the same 

information with a 3 percent discount rate. 

11-15 
Final Regulatory Impact Analysis 

Table 11.2-9: 30-Year Net Present Value Cost Summary for Alternative 

Program Options with a 7 Percent Discount Rate (Million 2005$) 

Source Alt Target Standard Scenario Alternative 

Exhaust 1 Class I $1,228 more $1,558 

2 Class II $1,146 more $4,040 

3a OB/PWC $- more $347 

4 SD/I <373 kW $343 less $194 

5 more $388 

Evap 6b HH $- more $318 

7 Class I & Class II $718 less $394 

8b Class I & Class II $- more $570 

9 Installed marine fuel 

tank 

$250 less $144 

10 more $310 

11 Portable marine fuel tank $8 less $7 

a Costs are presented incremental to the final standards for OB/PWC because, for this alternative, a second stage of 

standards is considered in 2012 beyond the final standards. b Only considers standards for venting emission control which are not in the final standards. The venting emission 

standards considered here are diurnal for Class I and Class II and diurnal/running loss for handheld. 

Table 11.2-10: 30-Year Net Present Value Cost Summary for Alternative 

Program Options with a 3 Percent Discount Rate (Million 2005$) 

Source Alt Target Standards Scenario Alternative 

Exhaust 1 Class I $2100 more $2,944 

2 Class II $1831 more $7,366 

3a OB/PWC $- more $556 

4 SD/I <373 kW $541 less $304 

5 more $626 

Evap 6b HH $- more $544 

7 Class I & Class II $1,180 less $630 

8b Class I & Class II $- more $962 

9 Installed marine fuel 

tank 

$413 less $239 

10 more $512 

11 Portable marine fuel tank $12 less $11 

a Costs are presented incremental to the standards for OB/PWC because, for this alternative, a second stage of 

standards is considered in 2012 beyond the final standards. b Only considers standards for venting emission control which are not in the final standards. The venting emission 

standards considered here are diurnal for Class I and Class II and diurnal/running loss for handheld. 

11.3 Emission Reduction 

11-16 
Regulatory Alternatives 

This section describes the estimated emission reductions associated with each of the 

alternative program options. We developed these estimates using the NONROAD emissions 

inventory model and methodology described in Chapter 3. The modeling inputs for alternative 

options are provided in Appendix 11A and Appendix 11B. 

The incremental emission reductions of complying with the alternative program options 

are presented as incremental to the base case without the final standards. The only exception to 

this is the second phase of OB/PWC standards. The alternatives and the requisite technology 

are described in Section 11.1. Further, emission inventory results are provided as the total net 

present value (NPV) for a 30-year period. The NPV estimates are calculated based on both a 7 

percent and a 3 percent discount rate. Small SI and Marine SI emission reductions are 

presented separately in Tables 11.3-1 and 11.3-2. 

Table 11.3-1: 30-Year Net Present Value 

Emission Reduction Summary for Alternative 

Program Options with a 7 Percent Discount Rate (Million Tons) 

Source Alt Target Standard Scenario Alternative 

Exhaust 1 Class I 0.73 more 0.63 

2 Class II 1.05 more 1.27 

3a OB/PWC 0 more 0.26 

4 SD/I <373 kW 0.33 less 0.22 

5 more 0.32 

Evap 6b HH 0 more 0.04 

7 Class I & Class II 1.04 less 0.63 

8b Class I & Class II 0 more 0.12 

9 Installed marine fuel 

tank 

0.36 less 0.26 

10 more 0.38 

11 Portable marine fuel tank 0.07 less 0.06 a Tons reduced are presented incremental to the standards for OB/PWC because, for this alternative, a second stage 

of standards is considered in 2012 beyond the final standards. b Only considers standards for venting emission control which are not in the final standards. The venting emission 

standards considered here are diurnal for Class I and Class II and diurnal/running loss for handheld. 

11-17 
Final Regulatory Impact Analysis 

Table 11.3-2: 30-Year Net Present Value 

Emission Reduction Summary for Alternative 

Program Options with a 3 Percent Discount Rate (Million Tons) 

Source Alt Target Standard Scenario Alternative 

Exhaust 1 Class I 1.33 more 1.22 

2 Class II 1.90 more 2.52 

3a OB/PWC 0 more 0.50 

4 SD/I <373 kW 0.64 less 0.42 

5 more 0.65 

Evap 6b HH 0 more 0.07 

7 Class I & Class II 1.83 less 1.09 

8b Class I & Class II 0 more 0.21 

9 Installed marine fuel 

tank 

0.70 less 0.50 

10 more 0.73 

11 Portable marine fuel tank 0.13 less 0.11 a Tons reduced are presented incremental to the standards for OB/PWC because, for this alternative, a second stage 

of standards is considered in 2012 beyond the final standards. b Only considers standards for venting emission control which are not in the final standards. The venting emission 

standards considered here are diurnal for Class I and Class II and diurnal/running loss for handheld. 

11-18 
Regulatory Alternatives 

11.4 Cost Effectiveness 

This section describes the cost effectiveness associated with each of the alternative 

program options. The costs are expressed as millions of dollars and the emission reductions are 

in terms of short tons. All results are presented as incremental to the base case without the final 

standards. The only exception to this is the second phase of OB/PWC standards where the 

values are calculated based on costs and emission reductions incremental to the final standards. 

Tables 11.4-1 and 11.4-2 present cost per ton estimates, using both a 7 percent and a 3 percent 

discount rate, for Small SI engines/equipment and Marine SI engines/vessels as outlined in 

Table 11.2-1. 

Table 11.4-1: Comparison of Cost Effectiveness for Final Standards and Alternatives 

Without Fuel Savings, 7 Percent Discount Rate ($/ton) 2005$ 

Source Alt Target Standard Scenario Alternative 

Exhaust 1 Class I $1,680 more $2,540 

2 Class II $1,086 more $3,170 

3a OB/PWC $790 more $1,340 

4 SD/I <373 kW $1,030 less $880 

5 more $1,210 

Evap 6b HH NA more $8,150 

7 Class I & Class II $690 less $630 

8b Class I & Class II NA more $4,900 

9 Installed marine fuel 

tank 

$690 less $550 

10 more $820 

11 Portable marine fuel tank $115 less $120 

a Cost effectiveness of more stringent alternative is presented incremental to the standards for OB/PWC because, 

for this alternative, a second stage of standards is considered in 2012 beyond the final standards. b Only considers standards for venting emission control which are not in the final standards. The venting emission 

standards considered here are diurnal for Class I and Class II and diurnal/running loss for handheld. 

11-19 
Final Regulatory Impact Analysis 

Table 11.4-2: Comparison of Cost Effectiveness for Final Standards and Alternatives 

Without Fuel Savings, 3 Percent Discount Rate ($/ton) 2005$ 

Source Alt Target Standard Scenario Alternative 

Exhaust 1 Class I $1,580 more $2,410 

2 Class II $965 more $2,930 

3a OB/PWC $670 more $1100 

4 SD/I <373 kW $840 less $720 

5 more $970 

Evap 6b HH NA more $7,620 

7 Class I & Class II $640 less $580 

8b Class I & Class II NA more $4560 

9 Installed marine fuel 

tank 

$590 less $500 

10 more $700 

11 Portable marine fuel tank $100 less $100 

a Cost effectiveness of more stringent alternative is presented incremental to the standards for OB/PWC because, 

for this alternative, a second stage of standards is considered in 2012 beyond the final standards. b Only considers standards for venting emission control which are not in the final standards. The venting emission 

standards considered here are diurnal for Class I and Class II and diurnal/running loss for handheld. 

Ideally, this analysis would include an assessment of the monetized benefits which 

would potentially accompany each alternative as was provided in Chapter 8. This would 

provide further information for decision making and comparison to the final program. 

Unfortunately, the emissions data needed to conduct such an analysis, such as the potential PM 

benefits for the more stringent exhaust emission scenarios, is not available for this NPRM. This 

limits the utility of any comparisons which could be made since monetized benefits are partially 

dependent on PM health benefits. 

11.5 Summary and Analysis of Alternative Program Options 

This section presents a comparative summary of the important aspects related to the 

various alternative program options and our rationale for not pursuing an option relative to the 

final standards. 

11.5.1 Exhaust Emission Standards 

11.5.1.1 Small SI Engine HC+NOx Standards 

11.5.1.1.1 Class I 

This alternative considers a more stringent standard of 50 percent HC+NOx emission 

reduction beginning in 2015 for Phase 3 Class I engines instead of a reduction of 38 percent 

11-20 
Regulatory Alternatives 

beginning in 2012 . While these emission standards may be feasible, it is clearly in the in the 

longer term relative to the timing of the final standards. For analytical purposes the time line to 

begin implementation of the new standards was set at the 2015 model year. This is three model 

years past the implementation year for the final standards. For the analytical period we 

considered, the final standards provide more emission reductions than the alternative by 

202,600 tons between 2012 and 2020. Postponing the exhaust emission standards to 2015 could 

likely also lead to postponing controls on running loss emissions with an additional loss of 

47,000 tons of control. States with air quality problems would benefit from emission reductions 

in an earlier time frame. Thus, while both approaches are cost effective, we elected to go with 

the 38 percent reduction in 2012. In the context of section 213(a)(3) of the Clean Air Act, it 

represents the most stringent standards feasible within the lead time considered. 

11.5.1.1.2 Class II 

This alternative considers a more stringent standard of 4 g/kW-hr HC+NOx , a reduction 

of about 67 percent for Class II engines over phase 2. These standards assume the use of closed 

loop electronic fuel injection and catalysts on all Class II engines. We are expecting engine 

manufacturers to meet the final standards by applying closed loop EFI on a portion of their Vtwin engines and for the engine manufacturers or equipment manufacturers to use catalytic 

mufflers on the remaining engines. While these emission standards may be feasible it is clearly 

in the in the longer term relative to the timing of the final standards. For analytical purposes the 

time line to begin implementation of the new standards was set at the 2015 model year. This is 

four model years past the implementation year for the final standards. For the 30 year analytical 

period we considered, the final rule provides fewer overall emission reductions than the 

alternative, but between 2011 and 2020 the final rule gives 150,300 tons more reduction than 

the alternative assuming that running loss control is also postponed to begin in the 2015 model 

year. States with air quality problems would benefit from emission reductions in an earlier time 

frame. Thus, while both approaches are cost effective, we elected to go with the 34 percent 

reduction in 2011. In the context of section 213(a)(3) of the Clean Air Act, it represents the 

most stringent standards feasible within the lead time considered. 

11.5.1.2 Outboard/Personal Watercraft (OB/PWC) Engine HC+NOx and CO 

Emission Standards 

We analyzed the costs and emission reductions associated with more stringent standards 

for OB/PWC engines. We have concerns with this second tier of OB/PWC standards at this 

time. While some four-stroke engines may be able to meet a 10 g/kW-hr standard with 

improved calibrations, it is not clear that all engines could meet this standard without applying 

catalyst technology. Direct injection two-strokes engines would face additional challenges. At 

this time, we believe it is not appropriate to base standards in this rule on the use of catalysts for 

OB/PWC engines. Although this technology may be attractive in the longer term, little 

development work has been performed on the application of 3-way catalysts to OB/PWC 

engines. For this alternative, our modeling assumes all OB/PWC engines which need to can 

successfully apply aftertreatment technology. 

11-21 
Final Regulatory Impact Analysis 

11.5.1.3 Sterndrive/Inboard (SD/I) Engine HC+NOx and CO Emission Standards 

With regard to less stringent standards, we believe that EGR would be a technologically 

feasible and cost-effective approach to reducing emissions from SD/I marine engines. 

However, we believe that greater reductions could be achieved through the use of catalysts. We 

considered basing an interim standard on EGR, but were concerned that this would divert 

manufacturers' resources away from catalyst development and could have the effect of delaying 

emission reductions from this sector. Setting a less stringent standard would likely be 

inconsistent with the requirements of section 213 of the Clean Air Act because at least one SD/I 

engine manufacturer offers a compliant product for sale in the US. In the NPRM we do ask for 

comment on a short-phase-in to deal with a change in the engine a supplier’s product lines. 

With regard to more stringent requirements, we do not believe that they would 

necessarily lead to any further significant emission reductions in HC+NOx. Because this is the 

first generation of emission standards for this category of recreational marine engines, we 

believe that most manufacturers will strive to achieve emission levels below the final standards 

to give them certainty that they will pass the standards in-use, especially as catalysts on SD/I 

engines are a new technology. Therefore, we do not believe that it is necessary at this time to 

consider a lower standard for these engines. 

11.5.2 Evaporative Emission Standards 

11.5.2.1 Small SI Engine 

We analyzed requiring diurnal and running loss control from handheld equipment in 

2012. Even though it would be feasible from a strict technical perspective it is not a attractive 

option at this time. Fuel tanks from this equipment are very small, most less than one liter, and, 

with the exception of commercial equipment, their use is less than 15 hours per year. Adding 

hardware to control diurnal and running loss emissions would add weight which could be 

problematic on handheld equipment. In addition, it could create the potential for fuel leaks in 

equipment which can be used in rotated and inverted positions in the field. In addition, this 

option does not appear cost effective. For these reasons we elected not to pursue it. 

With regard to controlling running loss emissions control from non-handheld equipment 

we believe it is feasible at a relatively low cost. Running loss emissions can be controlled by 

sealing the fuel cap and routing vapors from the fuel tank to the engine intake. This emission 

control approach is relatively straight-forward and inexpensive and do not have the weight and 

in-use position issues such as mentioned above for handheld equipment. Deleting the 

requirement does not meaningfully improve the cost effectiveness. Not finalizing these 

requirements would be inconsistent with the section 213 of the Clean Air Act. 

California requires control diurnal fuel tank emissions from Class I and Class II 

equipment as part of its overall fuel evaporative certification requirements. California requires 

an active purge of the control system. We evaluated the alternative of adding a diurnal 

requirement like that in California. Even though it would be feasible from a strict technical 

11-22 
Regulatory Alternatives 

perspective it is not a attractive option at this time. While workable, there are some important 

issues would need to be resolved for diurnal emission control, such as cost, packaging, and 

vibration. Also, California requires an active purge, but we believe that a substantial reduction 

on the order of 50 percent could be achieved with a less complicated and less expensive passive 

purge approach. Finally, the cost and cost effectiveness of this program sub-element are of 

concern given the relatively low emissions levels (on a per-equipment basis) from such small 

fuel tanks. Overall, we do not consider this to be an attractive option at this time for Small SI 

engines as a group. 

11.5.2.2 Marine 

Although we considered the alternative of not requiring diurnal emission control for 

installed fuel tanks, we believe that carbon canisters are feasible for boats at relatively low cost. 

Carbon canisters have been installed on fourteen boats by industry in a pilot program intended 

to demonstrate the feasibility of this technology. The final standards are achievable through 

engineering design-based certification with canisters that are much smaller than the fuel tanks. 

In addition, sealed systems, with pressure control strategies would be accepted under the 

engineering design-based certification provisions. Eliminating these requirements would not 

meaningfully affect the cost effectiveness of the marine evaporative program. Not finalizing 

these controls would be inconsistent with the requirements of section 213 of the Clean Air Act. 

We also considered the feasibility of requiring the use of carbon canisters with active 

purging to control diurnal emissions. However, we are concerned that active purging would 

occur infrequently due to the low hours of operation per year seen by many boats. In addition, 

active purge adds complexity into the system in that the engine must be integrated into the 

control strategy. This could end up involving engine, tank, and vessel manufacturers in 

certification processes. Although we did not model it, this approach would undoubtedly require 

more lead time to implement because it is more complex and involves more entities. Based on 

data presented in Chapter 5, carbon canisters can be used to reduce emissions by more than 50 

percent with passive purging. This passive purging occurs during the normal tank breathing 

process caused by ambient temperature changes without creating any significant pressure in the 

fuel tank. The small additional benefit of an actively purged diurnal control system would 

likely not justify the cost and complexity of implementing such a system, even though it 

appears to be cost effective. 

Portable marine fuel tanks are used in vessels with outboard motors. Many of these 

tanks employ self-sealing vents which close the tank to the atmosphere when it is not in-use. 

This is quite straightforward, and it can be applied to all such tanks in the future for a 

reasonable cost. Not finalizing these controls would be inconsistent with the requirements of 

section 213 of the Clean Air Act. 

11-23 
Final Regulatory Impact Analysis 

APPENDIX 11A: Emission Factors for the Less Stringent Alternative 

11A.1 Exhaust Emission Factors and Deterioration Rates 

11A.1.1 Small SI Exhaust 

No less stringent exhaust emission standards were quantitatively analyzed for either 

Class I or Class II Small SI engines. 

11A.1.2 Marine SI Exhaust 

In the less stringent alternative, the same standards are considered for OB/PWC engines 

as for the primary scenario. However, for SD/I engines, we consider less stringent standards. 

As discussed above, these standards are based on the use of EGR for SD/I engines less than 373 

kW and engine calibration for larger engines. For engines less than 373 kW we considered less 

stringent alternative standards of 10 g/kW-hr HC+NOx and 150 g/kW-hr CO for SD/I engines 

less than 373 kW. For high-performance engines, we did not model alternative scenarios, as 

discussed above. Because these emission factors are based on engine-out emissions, we use the 

same deterioration factors (DF) as for the baseline case. Table A-1 presents the zero-hour SD/I 

emission factors and the accompanying deterioration factors used to model the less stringent 

alternative. 

Table 11A-1: Less Stringent Alternative EFs [g/kW-hr] and DFs for SD/I 

Engine Category 

HC NOx CO 

BSFC

EF DF EF DF EF DF 

<373 kW SD/I 4.05 1.26 4.00 1.03 96.3 1.35 345 

11A.2 Evaporative Emission Factors 

As discussed above, no changes in the hose and tank permeation standards were 

considered in the less stringent alternative. The less stringent scenario was modeled for Small 

SI equipment by using the baseline running loss and diffusion rates for Class I and Class II 

equipment. For marine, the less stringent alternative was modeled by using the baseline diurnal 

emission rates for vessels with installed fuel tanks. 

11-24 
Regulatory Alternatives 

APPENDIX 11B: Emission Factors for the More Stringent Alternative 

11B.1 Exhaust Emission Factors and Deterioration Rates 

11B.1.1 Small SI Exhaust 

For analytical purposes, we identified a more stringent program option of 8 g/kW-hr 

HC+NOx standard for Class I engines that would be implemented beginning in 2015. This 

standard represents about a 50 reduction from the existing Phase 2 standard, rather than the 

approximately 38 percent reduction associated with the final rule. The option also provides 3 

more years of lead time. For Class II engines, we identified an alternative for a more stringent 

exhaust HC+NOx emission standard of 4.0 g/kW-hr beginning in 2015. (This option also 

includes an associated delay in the corresponding running loss requirement such that engine 

changes are made simultaneously.) Such an exhaust emission standard represents a 67 percent 

reduction relative to the existing Phase 2 standard, rather than the 34 percent reduction 

associated with the final rule. 

In modeling this more stringent option, we assumed the same phase-in schedule that 

reflects a number of flexibilities for engine and equipment manufacturers, and allows them to 

sell some Phase 2 compliant engines in the early years of the program. We also assumed that 

Class I side-valve technology would be completely replaced with overhead valve designs, and 

that all of the Class II engines would require closed loop control electronic fuel injection (EFI). 

Since EFI equipped engines enjoy a 10 percent fuel consumption advantage over their 

carbureted counterparts, we also revised the brake-specific fuel consumption (BSFC) for Class 

II engines. The new BSFC value is 0.666 lb/hp-hr. 

 All the modeling inputs were developed using a methodology consistent with that 

described in Chapter 3 of this draft RIA. The alternative emission standards and phase-in 

assumptions are shown in Table B-1. The emission factors are shown in Table B-2. 

Table 11B-1: More Stringent Phase 3 Emission Standards and Implementation Schedule 

for Class I and II Small SI Engines (g/kW-hr or Percent) 

Engine 

Class Requirement 2015 2016 2017 2018 2019+ 

Class I HC+NOx 8 8 8 8 8 

Required Sales 

Percentage 95 95 100 100 100 

Class II HC+NOx 4 4 4 4 4 

Required Sales 

Percentage 83 83 93 93 100 

11-25 
Final Regulatory Impact Analysis 

Table 11B-2: More Stringent Phase 3 Modeling Emission Factors 

for Small SI Engines (g/KW-hr) 

Class/ 

Technology 

HC 

ZML HC "A" NOx 

ZML NOx "A" CO ZML CO "A"

 Class I - SV 4.48 1.011 1.12 0.470 319.76 0.070

 Class I - 4.07 1.011 1.53 0.470 325.06 0.070

 Class II 2.13 1.011 0.67 0.470 391.13 0.080 

11B.1.2 Marine SI Exhaust 

For OB/PWC engines, the more stringent alternative considers exhaust emissions 

standards that are about 40 percent lower for HC+NOx and about 30 percent lower for CO than 

the final standard. The more stringent alternative emission standards are modeled as a second 

phase of standards, beyond the primary, beginning in 2012. In determining the combined 

HC+NOx emission factor, we used the final emission standards with a 10 percent compliance 

margin (with deterioration factor applied). To determine the NOx emission factors, we used 

certification data and other emissions data presented in Chapter 4, to determine the sales 

weighted average NOx for low emission technologies in each power bin. HC was then 

determined as the difference between the HC+NOx and the NOx emission factors. Because we 

are finalizing the same standards for OB and PWC and because they use similar engines, we use 

the same HC+NOx emission factors and deterioration factors for both engine types. Because 

the final CO standard primarily acts as a cap on CO for many of the engines, the CO emission 

factors differ somewhat for CO based on data in the certification database for low CO engines. 

We use the same deterioration rates as in the primary case. Table B-3 presents the zero-hour 

OB/PWC emission factors used in analyzing the more stringent alternative. 

Table B-3: More Stringent Alternative Emission Factors for OB/PWC [g/kW-hr] 

Power Bin HC NOx CO

 OB PWC 

BSFC 

0-2.2 kW 

2.3-4.5 kW 

4.6-8.2 kW 

8.3-11.9 kW 

12.0-18.6 kW 

18.7-29.8 kW 

29.9-37.3 kW 

37.4-55.9 kW 

55.9-74.6 kW 

74.7-130.5 kW 

130.6+ kW 

11.7 

10.9 

10.5 

9.0 

9.5 

7.5 

5.7 

5.2 

5.2 

5.4 

6.3 

3.02 

2.25 

3.50 

4.22 

2.69 

3.55 

3.70 

3.38 

3.38 

3.13 

2.30 

362 

238 

195 

165 

137 

120 

114 

115 

115 

101 

93 

426 

359 

162 

154 

145 

137 

137 

137 

137 

135 

119 

563 

560 

555 

552 

543 

528 

507 

471 

471 

415 

387 

11-26 
Regulatory Alternatives 

For SD/I engines greater than 373 kW, we did not model the use of catalysts for reasons 

discussed above. However, for SD/I engines less than 373 kW, we considered a more stringent 

HC+NOx standard of 2.5 g/kW-hr. To model this standard, we used zero-hour emission factors 

of 0.90 g/kW-hr HC and 0.80 g/kW-hr NOx. No changes were made in other emission factors 

for this more stringent alternative. In addition, the same deterioration factors were used here as 

in the primary alternative. 

11B.2 Evaporative Emission Factors 

As discussed above, no changes in the hose and tank permeation standards were 

considered in the more stringent alternative. The more stringent scenario modeled for Small SI 

equipment by considering diurnal standards beginning in 2011 for Class II and 2012 for 

handheld and Class I equipment. This diurnal emission standards was modeled using a 60 

percent reduction from baseline. Also, the more aggressive option for Class II exhaust 

standards was modeled as also including a corresponding delay in the running loss requirement 

such that engine changes are made simultaneously. 

For marine, the more stringent alternative was a standard requiring active purging of 

canisters for vessels with installed fuel tanks. This was modeled by using a 70 percent 

reduction in diurnal emissions compared to the baseline. 

11-27 
Final Regulatory Impact Analysis 

Chapter 11 References 

1. “Small SI Engine Technologies and Costs, Final Report,” ICF International, August 2006. 

2. “Marine Outboard and Personal Watercraft SI Engine Technologies and Costs,” ICF Consulting, prepared for the 

U.S. Environmental Protection Agency, July 2006, Docket Identification EPA-HQ-OAR-2004-0008-0452. 

3. “Sterndrive and Inboard Marine SI Engine Technologies and Costs,” ICF Consulting, prepared for the U.S. 

Environmental Protection Agency, July 2006, Docket Identification EPA-HQ-OAR-2004-0008-0453. 

4. “Small SI Engine Technologies and Costs, Final Report,” ICF International, August 2006. 

5. “Small SI Engine Technologies and Costs, Final Report,” ICF International, August 2006. 

11-28