Control of Emissions from Marine SI 

and Small SI Engines, Vessels, and 

Equipment 

Draft Regulatory Impact Analysis 
Control of Emissions from Marine SI


and Small SI Engines, Vessels, and 


Equipment


Draft Regulatory Impact Analysis


Assessment and Standards Division 

Office of Transportation and Air Quality 

U.S. Environmental Protection Agency 

NOTICE 

This technical report does not necessarily represent final EPA decisions or 

positions. It is intended to present technical analysis of issues using data 

that are currently available. The purpose in the release of such reports is to 

facilitate the exchange of technical information and to inform the public of 

technical developments which may form the basis for a final EPA decision, 

position, or regulatory action. 

EPA420-D-07-004 

April 2007 
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 .................................................... 2-17 
 
 

2.3 Gaseous Air Toxics ................................................... 2-37 
 
 

2.4 Carbon Monoxide .................................................... 2-40 
 
 

2.5 Acute Exposure to Air Pollutants ........................................ 2-43 
 
 

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 ........................................................ 3-27 
 
 

3.5 Projected Emissions Reductions from the Proposed Rule ..................... 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 .................................. 4-23 
 
 

4.4 Feasibility of Outboard/Personal Watercraft Marine Engine Standards .......... 4-41 
 
 

4.5 Feasibility of Sterndrive/Inboard Marine Engine Standards ................... 4-47 
 
 

4.6 Feasibility of Standard for Marine Generator Sets ........................... 4-58 
 
 

4.7 Test Procedures ...................................................... 4-59 
 
 

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

APPENDIX 4A: Normalized Modal Emissions for a 7.4 L MPI SD/I ............... 4-80 
 
 

CHAPTER 5: Feasibility of Evaporative Emission Control 

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

5.2 Running Loss Emissions ............................................... 5-25 
 
 

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

5.4 Fuel/Vapor Hose Permeation ........................................... 5-67 
 
 

5.5 Other Evaporative Emissions ........................................... 5-86 
 
 

5.6 Evaporative Emission Test Procedures .................................... 5-88 
 
 
5.7 Impacts on Noise, Energy, and Safety ................................... 5-106 
 
 

APPENDIX 5A: Diurnal Temperature Traces ................................ 5-109 
 
 

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

Venting on Diffusion ................................................. 5-112 
 
 

APPENDIX 5C: Diurnal Emission Results: Canister and Passive-Purge ............ 5-117 
 
 

APPENDIX 5D: Material Properties of Common Fuel System Materials ........... 5-118 
 
 

APPENDIX 5E: Diurnal Test Temperature Traces ............................. 5-122 
 
 

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 . . . 6-43
 
 

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 ................... 6-78 
 
 

6.7 Cost Sensitivity Analysis .............................................. 6-91 
 
 

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 ................................................... 8-8 
 
 

8.3 PM-Related Health Benefits Estimation - Methods and Inputs ................. 8-10 
 
 

8.4 Benefits Analysis Results for the Proposed Standards ........................ 8-17 
 
 

8.5 Unquantified Health and Welfare Effects .................................. 8-20 
 
 

8.6 Methods for Describing Uncertainty ..................................... 8-23 
 
 

8.7 Health-Based Cost Effectiveness Analysis ................................. 8-35 
 
 

8.8 Comparison of Costs and Benefits ....................................... 8-36 
 
 

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 ..................................... 9-36 
 
 

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

Appendix 9A: Impacts on Small SI Markets ................................... 9-72 
 
 

Appendix 9B: Impacts on Marine SI Markets .................................. 9-90 
 
 

Appendix 9C: Time Series of Social Cost .................................... 9-102 
 
 

Appendix 9D: Overview of Model Equations and Calculation .................... 9-106 
 
 

Appendix 9E: Elasticity Parameters for Economic Impact Modeling ............... 9-111 
 
 

Appendix 9F: Derivation of Supply Elasticity ................................ 9-124 
 
 

Appendix 9G: Initial Market Equilibrium - Price Forecasts ...................... 9-126 
 
 

Appendix 9H: Sensitivity Analysis ......................................... 9-128 
 
 

CHAPTER 10: Small-Business Flexibility Analysis 

10.1 Overview of the Regulatory Flexibility Act .............................. 10-1 
 
 

10.2 Need for the Rulemaking and Rulemaking Objectives ...................... 10-2 
 
 
Draft Regulatory Impact Analysis 

10.3 Definition and Description of Small Entities .............................. 10-3 
 
 

10.4 Summary of Small Entities to Which the Rulemaking Will Apply ............. 10-5 
 
 

10.5 Related Federal Rules ............................................... 10-6 
 
 

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

10.7 Regulatory Alternatives .............................................. 10-8 
 
 

10.8 Projected Economic Effects of the Proposed Rulemaking .................. 10-20 
 
 

CHAPTER 11: Regulatory Alternatives 

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

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

11.3 Emission Reduction ................................................ 11-18 
 
 

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

11.5 Summary and Analysis of Alternative Program Options .................... 11-21 
 
 

APPENDIX 11A: Emission Factors for the Less Stringent Alternative ............. 11-26 
 
 

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


 
 

Executive Summary 

Executive Summary 

The Environmental Protection Agency (EPA) is proposing 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 

proposed 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 Proposed 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), 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, eutrophication, and regional haze. 

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

public health and welfare. As of October 2006 approximately 157 million people live in the 116 

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 proposed rule will be useful to states in attaining and maintaining the ozone, CO, 

and PM NAAQS. 

In 2001, emissions from land-based nonroad Small SI engines and Marine SI 

engines were estimated to be about 28 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 assures 

NONROAD inventories from rules to date are maintained or continue to decrease. 

ES-1 
Draft Regulatory Impact Analysis 

Figure 1: Small SI VOC+NOx NONROAD Inventories for Baseline and 

Phase 3 Control (Exhaust plus Evaporative) 

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

2000 2010 2020 2030 2040

Ye ar

Tons

Baseline

Control

Figure 2: Marine SI VOC+NOx NONROAD Inventories for Baseline 

and Phase 3 Control (Exhaust plus Evaporative) 

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

2000 2010 2020 2030 2040

Ye ar

Tons

Baseline

Control

ES-2 
Executive Summary 

Proposed Exhaust and Evaporative Emission Standards 

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

proposed to apply. For Small SI engines, the standards are expected to require the use of 

aftertreatment systems with 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 proposed rule 

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

Table 1: Small SI Engine HC+NOx Exhaust Emission Standards and Schedule 

Engine Class Model Year 

HC+NOx 

[g/kW-hr] 

COa 

[g/kW-hr] 

Class I (80cc-225cc) 2012 10.0 610 

Class I (<80cc) 2012 Handheld standards Handheld 

standards 

Class II 2011 8.0 610 

a

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

Table 2: Small SI Equipment Evaporative Emission Standards and Schedule 

Fuel Line 

Permeation 

Tank 

Permeation 

Diffusion Running 

Loss 

General Evaporative 

Requirements 

Standard Level 15 

g/m2

/day 

1.5 

g/m2/day 

0.80 g/day Design 

Standard 

Design standards and 

good engineering 

judgment 

Handheld 2012a 2009-2013b,c NA NA 2010 

Class I 2008 2012 2012 2012 2012 

Class II 2008 2011 2011 2011 2011 

a

 2013 for small-volume families; cold weather applications are excluded.
 
 b

 2.5 g/m2/day for structurally integrated nylon fuel tanks.
 
 c

 2009 for families certified in California, 2013 for small-volume families, 2010 for remaining families.
 
 

ES-3 
Draft Regulatory Impact Analysis 

Table 3: Marine SI Engine HC+NOx Exhaust Standards and Schedule 

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

[g/kW-hr] 

OB/PWCac < 40 kW 2009 28-0.3 x Pb 500-5.0 x Pb 

> 40 kW 2009 16 300 

SD/Iac all 2009 5 75 

a Seeking comment on modest phase-in for these new standards.
 
 b

 P = maximum engine power in kilowatts (kW).
 
 c SD/I and OB/PWC also have NTE requirements; seeking comment on alternative standards for high-performance
 
 

engines (>373kW).
 
 

Table 4: Marine SI Engine Evaporative Emissions Standards and Schedule 

Fuel Line 

Permeation 

Tank 

Permeation 

Diurnal General Evaporative 

Requirements 

Standard Level 15 

g/m2

/day 

1.5 g/m2

/day 0.40 

g/gal/day 

Design standards and good 

engineering judgment 

Portable Tanks 2009 2011 2009a 2009 

PWC 2009 2011 2009 2009 

Other Installed Tanks 2009 2012 2010b 2010 

a

 Design standard.
 
 b

 Fuel tanks installed in non-trailerable boats (> 26 ft. in length) may meet a standard of 0.16 g/gal/day over an
 
 

alternative test cycle.
 
 

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 Proposed 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 proposed 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 proposing new, more stringent exhaust HC+NOx standards for Class I and II Small 

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

ES-4 
Executive Summary 

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 2005 model year, manufacturers certified over 500 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, several engine families in both classes are currently certified at levels that 

would comply with the proposed 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 proposed 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 

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 proposed 

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 

ES-5 
Draft Regulatory Impact Analysis 

appear sufficient to meet the standard. Nonetheless, some applications may require the use of 

both technologies. 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 proposed 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 Proposed Marine SI Exhaust Emission Standards 

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

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. 

ES-6 
Executive Summary 

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

and many two-stroke direct injection outboard engines can meet the proposed 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 can also meet the 

proposed 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 proposed standards. In addition, the majority of 

four-stroke engines would meet the proposed CO standards as well. 

We therefore believe the proposed 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 current certification data to the proposed 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 

exhaust stream prior to 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, demonstration programs have 

shown that emissions may be reduced by 70 to 80 percent for HC+NOx and 30 to 50 percent for 

CO over the various modes of the proposed 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. In addition, we are currently engaged in testing that 

includes accumulating hours on catalyst equipped SD/I engines in boats operating in saltwater. 

Earlier this year, one SD/I engine manufacturer began selling engines equipped with catalysts. 

ES-7 
Draft Regulatory Impact Analysis 

They have certified their engines to the California ARB standards, and are selling their 

catalyst-equipped engines nationwide. This manufacturer indicated that they have successfully 

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

Feasibility of Meeting the Proposed Evaporative Emission Standards 

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

proposed evaporative emission standards. We have collected and will continue to collect 

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 proposed 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). 

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 proposed 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 or polybutylene terephthalate (PBT). 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 proposed 

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 proposed permeation standards 

ES-8 
Executive Summary 

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 proposed 

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. 

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

losses from Small SI equipment by more than 90 percent. Other approaches would be to move 

the fuel tank away from heat sources or to use heat protection such as a shield or directed air 

flow. 

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

gasoline from fuel tanks. In fact, the proposed diffusion emission standard for Small SI 

equipment is based to a large degree on the diffusion control capabilities of these fuel caps. As 

discussed in Chapter 5, venting a fuel tank through a tube (rather than through an open orifice) 

also greatly reduces diffusion. We have conducted additional testing with short, 

narrow-diameter vent lines which shows that these lines provide enough resistance to diffusion 

to meet the proposed emission standards. 

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

ES-9 
Draft Regulatory Impact Analysis 

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. The annualized cost for Small SI emission regulations are 

$265 million without fuel savings and $203 million with fuel savings for exhaust only. For 

evaporative and exhaust combined, the annualized cost for Small SI emission regulation are 

$332 million without fuel savings and $218 with fuel savings. 

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 

$11 to $23 

$9 to $15 

$39 to $85 

$22 to $47 

$0.30 

$0.00 

Evaporative Near Term 

Long Term 

$3.16 

$2.29 

$6.90 

$5.30 

$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 proposed exhaust and evaporative 

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$) 

ES-10 
Executive Summary 

Annualized Cost to Manufacturers 

(millions/yr) 

Annualized fuel savings 

(millions/yr) 

Exhaust $267 $63 

Evaporative $67 $52 

Aggregate $334 $115 

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 Aggregate Discounted Aggregate Discounted 

NOx+HC Lifetime Cost per ton Lifetime Cost per ton 

Without Fuel Savings With Fuel Savings 

7% $1450 $950 

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 
Draft 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 

(Installed) 

SD/I 

(Installed) 

Exhaust 

Near Term 

Long Term 

$284 

$219 

$359 

$272 

$362 

$274 

Evaporative 

Near Term 

Long Term 

$12 

$8 

$17 

$11 

$74 

$62 

Total (without fuel savings) 

Near Term 

Long Term 

$296 

$227 

$376 

$283 

$436 

$336 

Total (with fuel savings) 

Near Term 

Long Term 

$201 

$132 

$221 

$128 

$285 

$185 

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. 

Chapter 6 presents aggregate costs of compliance for the proposed 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 $141 $67 

Evaporative $26 $25 

Aggregate $167 $92 

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 $350 

Economic Impact Analysis 

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

impacts of the proposed 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 ($195) as a result of the proposed standards, and the average price of a Marine SI vessel 

is projected to increase by between 0.5 percent and 2.1 percent ($160 to $496), depending on the 

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

9.1 percent ($17), and the average price of Small SI nonhandheld equipment is projected to 

increase by between 0.3 percent and 5.6 percent ($10 to $25), depending on equipment class. 

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

are PWC (4.2 percent) and Class II equipment (2.8 percent). 

The total social costs of the program in 2030 are estimated to be $241 million. This includes 

$569 million of direct compliance costs and $327 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: 66 percent of the 

Marine SI program social costs in 2030, and 79 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 62 percent. 

Benefits 

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

public health and welfare and the environment, as described in Chapter 8. EPA typically 

quantifies PM- and ozone-related benefits in its regulatory impact analyses (RIAs) when 

possible. In the analysis of past air quality regulations, ozone-related benefits have included 

morbidity endpoints and welfare effects such as damage to commercial crops. EPA has not 

recently included a separate and additive mortality effect for ozone, independent of the effect 

associated with fine particulate matter. For a number of reasons, including 1) advice from the 

Science Advisory Board (SAB) Health and Ecological Effects Subcommittee (HEES) that EPA 

consider the plausibility and viability of including an estimate of premature mortality associated 

with short-term ozone exposure in its benefits analyses and 2) conclusions regarding the 

scientific support for such relationships in EPA's 2006 Air Quality Criteria for Ozone and 

ES-13 
Draft Regulatory Impact Analysis 

Related Photochemical Oxidants (the CD), EPA is in the process of determining how to 

appropriately characterize ozone-related mortality benefits within the context of benefits 

analyses for air quality regulations. As part of this process, we are seeking advice from the 

National Academy of Sciences (NAS) regarding how the ozone-mortality literature should be 

used to quantify the reduction in premature mortality due to diminished exposure to ozone, the 

amount of life expectancy to be added and the monetary value of this increased life expectancy 

in the context of health benefits analyses associated with regulatory assessments. In addition, the 

Agency has sought advice on characterizing and communicating the uncertainty associated with 

each of these aspects in health benefit analyses. 

Since the NAS effort is not expected to conclude until 2008, the agency is currently 

deliberating how best to characterize ozone-related mortality benefits in its rulemaking analyses 

in the interim. For the analysis of the proposed locomotive and marine standards, we do not 

quantify an ozone mortality benefit. So that we do not provide an incomplete picture of all of the 

benefits associated with reductions in emissions of ozone precursors, we have chosen not to 

include an estimate of total ozone benefits in the proposed RIA. By omitting ozone benefits in 

this proposal, we acknowledge that this analysis underestimates the benefits associated with the 

proposed standards. Our analysis, however, indicates that the rule's monetized PM2.5 benefits 

alone substantially exceed our estimate of the costs. 

The PM2.5 benefits are scaled based on relative changes in direct PM emissions between this 

rule and the proposed Clean Air Nonroad Diesel (CAND) rule. As explained in Section 8.2.1, 

the PM2.5 benefits scaling approach is limited to those studies, health impacts, and assumptions 

that were used in the proposed CAND analysis. As a result, PM-related premature mortality is 

based on the updated analysis of the American Cancer Society cohort (ACS; Pope et al., 2002). 

However, it is important to note that since the CAND rule, EPA's Office of Air and Radiation 

(OAR) has adopted a different format for its benefits analysis in which characterization of the 

uncertainty in the concentration-response function is integrated into the main benefits analysis. 

Within this context, additional data sources are available, including a recent expert elicitation 

and updated analysis of the Six-Cities Study cohort (Laden et al., 2006). Please see the PM 

NAAQS RIA for an indication of the sensitivity of our results to use of alternative 

concentration-response functions. 

The analysis presented here assumes a PM threshold of 3 :g/m3, equivalent to background. 

Through the RIA for the Clean Air Interstate Rule (CAIR), EPA's consistent approach had been 

to model premature mortality associated with PM exposure as a nonthreshold effect; that is, with 

harmful effects to exposed populations modeled regardless of the absolute level of ambient PM 

concentrations. This approach had been supported by advice from EPA's technical peer review 

panel, the Science Advisory Board's Health Effects Subcommittee (SAB-HES). However, EPA's 

most recent PM2.5 Criteria Document concludes that "the available evidence does not either 

support or refute the existence of thresholds for the effects of PM on mortality across the range 

of concentrations in the studies," (p. 9-44). Furthermore, in the RIA for the PM NAAQS we 

used a threshold of 10 :g/m3 based on recommendations by the Clean Air Scientific Advisory 

Committee (CASAC) for the Staff Paper analysis. We consider the impact of a potential, 

assumed threshold in the PM-mortality concentration response function in Section 8.6.2. The 

ES-14 
Executive Summary 

monetized benefits associated with the proposed program are presented in Table 11. These 

estimates are in year 2005 dollars. 

We estimate that in 2030, the annual PM-related emission reductions associated with the 

proposed standards would annually prevent 450 premature deaths (based on the ACS cohort 

study), 52,000 work days lost, 500 hospital admissions, and 310,000 minor restricted-activity 

days. 

Table 11: Estimated Monetized PM-Related Health Benefits of the Proposed Standards 

Total Benefitsa, b, c (billions 2005$) 

2020 2030 

Using a 3% discount rate $2.1 + B $3.4 + B 

Using a 7% discount rate $1.9 + B $3.1 + B 

a

 Benefits include avoided cases of mortality, chronic illness, and other morbidity health endpoints. PM-related 

mortality benefits estimated using an assumed PM threshold at background levels (3 :g/m3). There is uncertainty 

about which threshold to use and this may impact the magnitude of the total benefits estimate. For a more detailed 

discussion of this issue, please refer to Section 8.6. 

b

 For notational purposes, unquantified benefits are indicated with a "B" to represent the sum of additional monetary 

benefits and disbenefits. A detailed listing of unquantified health and welfare effects is provided in Table 8.1-2 of 

the RIA. 

c

 Results reflect the use of two different discount rates: 3 and 7 percent, which are 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. 

Impact on Small Businesses 

Chapter 10 discusses our Initial Regulatory Flexibility Analysis, which evaluates the 

potential impacts of the proposed 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 proposed 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 proposed standards on small entities, and 

recommended that we propose and seek comment on the flexibilities. Chapter 10 discusses the 

flexibilities recommended by the Panel, the regulatory alternatives we considered in developing 

the proposal, and the flexibilities we are proposing. We have proposed several provisions that 

give affected small entities several compliance options aimed specifically at reducing their 

ES-15 
Draft Regulatory Impact Analysis 

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 proposed 

provisions include extra lead time for the proposed standards, reduced testing requirements for 

demonstrating compliance with the standards, and hardship provisions to address significant 

economic impacts and unusual circumstances related to the standards. These proposed 

provisions are intended to reduce the burden on small entities that will be required to meet the 

new emission standards when they are implemented. 

Alternative Program Options 

In developing the proposed 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 proposed emission standards are feasible in the 

context of 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 

standards we are proposing 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 propose 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 are proposing for the program. 

We believe it would be more effective to implement the Phase 3 standards we are proposing 

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 

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

ES-16 
Executive Summary 

greater than 40 kW with an equivalent percent reduction below the proposed 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 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 proposed 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 proposed 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 and 

diffusion 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. Other approaches would be to move the fuel tank 

away from heat sources or to use heat protection such as a shield or directed air flow. Diffusion 

can be controlled by simply using a tortuous tank vent path, which is often used today on Small 

SI equipment to prevent fuel splashing or spilling. These emission control technologies are 

relatively straight-forward, inexpensive, and achievable in the near term. 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 some important issues would need to be 

resolved for diurnal emission control, such as cost, packaging, and vibration. The cost 

sensitivity is especially noteworthy given the relatively low emissions levels (on a 

ES-17 
Draft Regulatory Impact Analysis 

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 

program. The results demonstrated the feasibility of this technology. The proposed 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 proposed 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. 

ES-18 
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 information on the businesses that would be affected by the proposed 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. 

This profile 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]). This 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 
Draft 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 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 demand subsection of that section. 

Figure 1-1: The Small Nonroad 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 r s 

Im p o rt s 

• E n g i n e s 

• E q u i pm e n t 

I n t e g ra t e 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 t i v e 

E n g i n e 

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

M e r c h a n t 

E n g i n e 

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

S m a l l S I E n g i n e M a r k e t s 

• C l a s s 

• S i z e 

C o m m e r c i a l Us 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 r a t o r s an d W e ld e r s 

• C o m p r e s s o r s 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 ts 

• Sn o w Bl o 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 
Draft 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 

M anufacturer 

Integrated 

Equipm ent 

Manufacturer 

Captive 

Engine 

M arinizer 

Merchant 

Engine 

Marinizer 

Autom otive Engine 

Market 

Merchant 

Engine 

M anufacturer 

M arinized Engine 

Market 

1-5 
Draft Regulatory Impact Analysis 

1.3 Fuel System Components 

The primary fuel system components that would be affected by the proposed 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 which is well 

below the permeation levels 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 
Draft Regulatory Impact Analysis 

Chapter 1 References 

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

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

1-8 
Air Quality, Health, and Welfare Concerns 

CHAPTER 2: Air Quality, Health, and Welfare Concerns 

The proposed standards would reduce emissions of hydrocarbons (HC), oxides of 

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

subject to this proposal. 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 can also impact health through personal exposure and contribute to adverse 

environmental effects including visibility impairment both in mandatory class I federal areas and 

in areas where people live, work and recreate. 

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, a 

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 proposing 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 

proposed 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 our citizens continue to 

be affected by these emissions. Figure 2-1 illustrates the widespread nature of these problems. 

Shown in this figure are counties designated as nonattainment for either or both of the 8-hour 

ozone or PM2.5 NAAQS, also depicted are the mandatory class I federal areas. The emission 

standards proposed in this rule would help reduce HC, NOx, air toxic and CO emissions and 

their associated health and environmental effects. 

2-1 
Draft Regulatory Impact Analysis 

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. We also describe the 

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

country continue to be exposed to high levels of ambient ozone and will continue to be into the 

future. Emissions of volatile organic compounds (VOCs) and NOx from the engines, vessels 

and equipment subject to this proposed 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. 

2.1.1 Science of Ozone Formation 

Ground-level ozone pollution is formed by the reaction of VOCs, of which HC are the 

major subset, 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 and nonroad motor vehicles (including those subject to this proposed rule), power 

plants, chemical plants, refineries, makers of consumer and commercial products, industrial 

facilities, and smaller area sources. 

2-2 
Air Quality, Health, and Welfare Concerns 

The science of ozone formation, transport, and accumulation is complex.1 Ground-level 

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 also 

can be transported into an area from pollution sources found hundreds of miles upwind, 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 man-made VOC emissions are 

relatively low can be NOx-limited. 

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 VOC-limited 

urban areas, NOx reductions are not expected to increase ozone levels if the NOx reductions are 

sufficiently large. 

Rural areas are almost always 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. 

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. 

2.1.2 Health Effects of Ozone Pollution 

Exposure to ambient ozone contributes to a wide range of adverse health effects.1 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. 

1

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 

delivered to the lung is not only influenced by the ambient concentration but also by the individuals breathing route 

and rate. 

2-3 
Draft Regulatory Impact Analysis 

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

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

medication usage, inflammation of the lungs, and a variety of other respiratory effects. There is 

also evidence that ozone may contribute to cardiovascular health effects. People who are more 

susceptible to effects associated with exposure to ozone include children, asthmatics and the 

elderly. There is also suggestive evidence that certain people may have greater genetic 

susceptibility. Those with greater exposures to ozone, for instance due to time spent outdoors 

(e.g., 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.4, 5, 6, 7, 8, 9 Repeated 

exposure to ozone can increase susceptibility to respiratory infection and lung inflammation and 

can aggravate preexisting respiratory diseases, such as asthma.

10, 11, 12, 13, 14 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 

lead to premature aging of the lungs and/or chronic respiratory illnesses, such as emphysema and 

chronic bronchitis.15, 16, 17, 18 

Children and adults who are outdoors and active during the summer months, such as 

construction workers and other outdoor workers, are among those most at risk of elevated ozone 

exposures.19 Children and outdoor workers tend to have higher ozone exposures 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.20 For example, summer camp studies in the 

Eastern United States and Southeastern Canada have reported significant reductions in lung 

function in children who are active outdoors.21, 22, 23, 24, 25, 26, 27, 28 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 ozone 

levels during prolonged periods of moderate exertion.29, 30, 31, 32 

EPA typically quantifies ozone-related health impacts in its regulatory impact analyses 

(RIAs) when possible. In the analysis of past air quality regulations, ozone-related benefits have 

included morbidity endpoints and welfare effects such as damage to commercial crops. EPA has 

not recently included a separate and additive mortality effect for ozone, independent of the effect 

associated with fine particulate matter. For a number of reasons, including 1) advice from the 

Science Advisory Board (SAB) Health and Ecological Effects Subcommittee (HEES) that EPA 

consider the plausibility and viability of including an estimate of premature mortality associated 

with short-term ozone exposure in its benefits analyses and 2) conclusions regarding the 

scientific support for such relationships in EPA's 2006 Air Quality Criteria for Ozone and 

Related Photochemical Oxidants (the CD), EPA is in the process of determining how to 

appropriately characterize ozone-related mortality benefits within the context of benefits 

2-4 
Air Quality, Health, and Welfare Concerns 

analyses for air quality regulations. As part of this process, we are seeking advice from the 

National Academy of Sciences (NAS) regarding how the ozone-mortality literature should be 

used to quantify the reduction in premature mortality due to diminished exposure to ozone, the 

amount of life expectancy to be added and the monetary value of this increased life expectancy 

in the context of health benefits analyses associated with regulatory assessments. 

Since the NAS effort is not expected to conclude until 2008, the agency is currently 

deliberating how best to characterize ozone-related mortality benefits in its rulemaking analyses 

in the interim. For the analysis of the proposed small engine standards, we do not quantify an 

ozone mortality benefit. So that we do not provide an incomplete picture of all of the benefits 

associated with reductions in emissions of ozone precursors, we have chosen not to include an 

estimate of total ozone benefits in the proposed RIA. By omitting ozone benefits in this 

proposal, we acknowledge that this analysis underestimates the benefits associated with the 

proposed standards. For more information regarding the quantified benefits included in this 

analysis, please refer to Chapter 8. 

2.1.3 Current and Projected Ozone Levels 

The Clean Air Act (CAA) requires EPA to set NAAQS for wide-spread pollutants from 

diverse sources considered harmful to public health and the environment. The CAA established 

two types of NAAQS: primary standards to protect public health, secondary standards to protect 

public welfare. The primary and secondary ozone NAAQS are identical. The 8-hour ozone 

standard is met when the 3-year average of the annual 4th highest daily maximum 8-hour ozone 

concentration is less than 0.08 ppm (62 FR 38855, July 18, 1997). 

The proposed emission reductions from this rule would assist 8-hour ozone 

nonattainment and maintenance areas in reaching the standard by each area’s respective 

attainment date, and maintaining the 8-hour ozone standard in the future. The emission 

reductions would also help continue to lower ambient ozone levels and resulting health impacts 

into the future. In this section we present information on current and projected future 8-hour 

ozone levels. 

2.1.3.1 Current 8-Hour 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 8-hour ozone NAAQS in June 2004. The final rule on Air Quality Designations and 

Classifications for the 8-hour Ozone NAAQS (69 FR 23858, April 30, 2004) lays out the factors 

that EPA considered in making the 8-hour ozone nonattainment designations, including 2001­

2003 measured data, air quality in adjacent areas, and other factors.2 

2

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 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 

2-5 
Draft Regulatory Impact Analysis 

As of October 2006, approximately 157 million people live in the 116 areas that are 

designated as nonattainment for either failing to meet the 8-hour ozone NAAQS or for 

contributing to poor air quality in a nearby area.3

 There are 461 full or partial counties that make 

up the 116 8-hour ozone nonattainment areas, as shown in Figure 2-1. 

Counties designated as ozone nonattainment were categorized, on the basis of their onehour ozone design value, as Subpart 1 or Subpart 2. Areas categorized as Subpart 2 were then 

further classified, on the basis of their 8-hour ozone design value, as marginal, moderate, serious, 

severe or extreme. The maximum attainment date assigned to an ozone nonattainment area is 

based on the area’s classification. 

States with 8-hour ozone nonattainment areas are required to take action to bring those 

areas into compliance prior to the ozone season in the attainment year. Based on the final rule 

designating and classifying 8-hour ozone nonattainment areas, most 8-hour ozone nonattainment 

areas will be required to attain the 8-hour ozone NAAQS in the 2007 to 2014 time frame and 

then be required to maintain the 8-hour ozone NAAQS thereafter.4 The emission standards 

being proposed in this action would become effective between 2008 and 2013. Thus, the 

expected ozone precursor emission inventory reductions from the standards proposed in this 

action would be useful to states in attaining and/or maintaining the 8-hour ozone NAAQS. 

EPA’s review of the ozone NAAQS is currently underway and a proposed decision in 

this review is scheduled for June 2007 with a final rule scheduled for March 2008. If the ozone 

NAAQS is revised then new nonattainment areas could be designated. While EPA is not relying 

on it for purposes of justifying this rule, the emission reductions from this proposal would also 

be helpful to states if there is an ozone NAAQS revision. 

2.1.3.2 Projected 8-Hour Ozone Levels 

Air quality modeling analyses completed for this proposed rule included assessing 

ambient ozone concentrations with and without the proposed emission controls. The air quality 

modeling predicts that without additional local, regional or national controls there will continue 

(including accounting for missing values and other complexities) are given in Appendices H and I of 40 CFR Part 

50. Due to the precision with which the standards are expressed (0.08 parts per million (ppm) for the 8-hour), a 

violation of the 8-hour standard is defined as a design value greater than or equal to 0.085 ppm or 85 parts per billion 

(ppb). 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. Therefore, our analysis may 

underestimate the number of counties with design values above the level of NAAQS. 

3

The 8-hour ozone nonattainment areas are listed in a Memo to the Docket titled “Nonattainment Areas and 

Mandatory Class I Federal Areas” and contained in Docket EPA-HQ-OAR-2004-0008. 

4

 The Los Angeles Southcoast Air Basin 8-hour ozone nonattainment area will have to attain before June 

15, 2021. 

2-6 
Air Quality, Health, and Welfare Concerns 

to be a need for reductions in 8-hour ozone concentrations in some areas in the future. 

We performed a series of ozone air quality modeling simulations for the Eastern United 

States using the Comprehensive Air Quality Model with Extension (CAMx). The air quality 

modeling performed for this proposed rule was based upon the same modeling system as was 

used in the Clean Air Interstate rule (CAIR) and Clean Air Nonroad Diesel (CAND) legislation. 

The model simulations were performed for five emission scenarios: a 2001 baseline projection, a 

2020 baseline projection and a 2020 projection with controls, a 2030 baseline projection and a 

2030 projection with controls. 

The impacts of the proposed emission standards were determined by comparing the 

model results in the future year control runs against the baseline simulations of the same year. 

This modeling supports the conclusion that the proposed controls would help reduce ambient 

ozone concentrations across the country. 

2.1.3.2.1 Ozone Modeling Methodology 

CAMx was utilized to estimate base and future-year ozone concentrations over the 

Eastern United States for various emission scenarios. CAMx simulates the numerous physical 

and chemical processes involved in the formation, transport, and destruction of ozone. CAMx is 

a photochemical grid model that numerically simulates the effects of emissions, advection, 

diffusion, chemistry, and surface removal processes on pollutant concentrations within a 

three-dimensional grid. This model is commonly used in developing attainment demonstration 

State Implementation Plans (SIPs) as well as estimating the ozone reductions expected to occur 

from a reduction in emitted pollutants. The following sections provide an overview of the ozone 

modeling completed as part of this rulemaking. More detailed information is included in the air 

quality modeling technical support document (TSD), which is located in the docket for this rule. 

The modeling domain used for this analysis and in the recent CAIR includes 37 states in 

the Eastern U.S., see Figure 2.1-2. The Eastern modeling domain encompasses the area from the 

East coast to mid-Texas and consists of two grids with differing resolutions. The model 

resolution was 36 km over the outer portions of the domain and 12 km in the inner portion of the 

grids. The vertical height of the eastern modeling domain is 4,000 meters above ground level 

with 9 vertical layers. 

2-7 
Draft Regulatory Impact Analysis 

Figure 2.1-2: Map of CAIR Modeling Domain 

Note: The inner area represents fine grid modeling at 12 km resolution. The outer area 

represents the coarse grid modeling at 36 km resolution. 

The simulation periods modeled by CAMx included several multi-day periods when 

ambient measurements were representative of ozone episodes over the Eastern U.S. A 

simulation period, or episode, consists of meteorological data characterized over a block of days 

that are used as inputs to the air quality model. Three multi-day meteorological scenarios during 

the summer of 1995 were used in the model simulations over the Eastern U.S.: June 12-24, July 

5-15, and August 7-21. In general, these episodes do not represent extreme ozone events but, 

instead, are generally representative of ozone levels near local design values. Each of the 

emission scenarios were simulated for the selected episodes. 

The meteorological data required for input into CAMx (wind, temperature, vertical 

mixing, etc.) was developed by a separate meteorological model. For the Eastern U.S., the 

gridded meteorological data for the three historical 1995 episodes were developed using the 

Regional Atmospheric Modeling System (RAMS), version 3b. This model provided needed data 

at every grid cell on an hourly basis. The meteorological modeling results were evaluated 

against observed weather conditions before being input into CAMx and it was concluded that the 

model fields were adequate representations of the historical meteorology. A more detailed 

description of the settings and assorted input files employed in these applications is provided in 

the air quality modeling TSD, which is located in the docket for this rule. 

The modeling assumed background pollutant levels at the top and along the periphery of 

the domain as in CAIR. Additionally, initial conditions were assumed to be relatively clean as 

well. Given the ramp-up days and the expansive domains, it is expected that these assumptions 

will not affect the modeling results, except in areas near the boundary (e.g., Dallas-Fort Worth 

TX). The other non-emission CAMx inputs (land use, photolysis rates, etc.) were developed 

using procedures employed in the highway light duty Tier 2/OTAG regional modeling. The 

development of model inputs is discussed in greater detail in the air quality modeling TSD. 

2-8 
Air Quality, Health, and Welfare Concerns 

Future-year estimates of 8-hour ozone design values were calculated based on relative 

reduction factors (RRF) between the future simulations, the 2001 base year simulation and 2001­

2003 8-hour ozone design values. The procedures for determining the RRFs are similar to those 

in EPA’s guidance for modeling for an 8-hour ozone standard.33 Hourly model predictions were 

processed to determine daily maximum 8-hour concentrations for each grid cell for each day 

modeled. The RRF for a monitoring site was determined by first calculating the multi-day mean 

of the 8-hour daily maximum predictions in the nine grid cells surrounding the site using only 

those predictions greater than or equal to 70 ppb, as recommended in the guidance. This 

calculation was performed for the base year scenario and each of the future-year baselines. The 

RRF for a site is the ratio of the mean prediction in the future-year scenario to the mean 

prediction in the base year scenario. RRFs were calculated on a site-by-site basis. The futureyear design value projections were then calculated by county, based on the highest resultant 

design values for a site within that county from the RRF application. For more information see 

the air quality modeling TSD. 

The inventories that underlie the ozone modeling conducted for this rulemaking included 

emission reductions from all current or committed federal, State, and local controls including the 

recent CAIR and, for the control case, including this proposed rulemaking. 

Finally, it should be noted that the emission control scenarios used as input for the air 

quality and benefits modeling are slightly different than the emission control program being 

proposed. The proposed levels of the standards have changed, in response to new information on 

the emission control technologies under consideration and other factors, since we performed the 

air quality modeling for this proposed rule. Additional detail is provided in Section 3.6. 

2.1.3.2.2 Areas at Risk of Future 8-Hour Ozone Violations 

This section summarizes the results of recent ozone air quality modeling from the CAIR 

analysis. Specifically, it provides information on our calculations of the number of people 

estimated to live in counties in which ozone monitors are predicted to exceed the 8-hour ozone 

NAAQS or to be within 10 percent of the 8-hour ozone NAAQS 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 this 

level will persist into the future. Those interested in greater detail should review the CAIR air 

quality modeling TSD. 

Based upon our CAIR air quality modeling, we anticipate that without emission 

reductions beyond those that were already required under promulgated regulation and approved 

SIPs, ozone nonattainment will likely persist into the future. With reductions from programs 

already in place (but excluding the emission reductions from this rule), the number of Eastern 

counties with projected 8-hour ozone design values at or above 85 ppb in 2010 is expected to be 

37 counties where 24 million people are projected to live, see Table 2.1-1. In addition, in 2010, 

148 Eastern counties where 61 million people are projected to live, will be within 10 percent of 

2-9 
Draft Regulatory Impact Analysis 

violating the 8-hour ozone NAAQS. 

Table 2.1.3.2.2-1. Eastern Counties with 2010 projected 
 

8-hour Ozone Concentrations Above and Within 10% of the 8-hour Ozone Standard
 

State County 

Arkansas Crittenden Co 

Connecticut Fairfield Co 

Connecticut Hartford Co 

Connecticut Middlesex Co 

Connecticut New Haven Co 

Connecticut New London Co 

Connecticut Tolland Co 

D.C. Washington Co 

Delaware Kent Co 

Delaware New Castle Co 

Delaware Sussex Co 

Georgia Bibb Co 

Georgia Cobb Co 

Georgia Coweta Co 

Georgia De Kalb Co 

Georgia Douglas Co 

Georgia Fayette Co 

Georgia Fulton Co 

Georgia Henry Co 

Georgia Rockdale Co 

Illinois Cook Co 

Illinois Jersey Co 

Illinois Lake Co 

Illinois McHenry Co 

Indiana Boone Co 

Indiana Clark Co 

Indiana Hamilton Co 

Indiana Hancock Co 

Indiana La Porte Co 

Indiana Lake Co 

Indiana Madison Co 

Indiana Marion Co 

Indiana Porter Co 

Indiana Shelby Co 

Indiana St Joseph Co 

Kentucky Campbell Co 

Louisiana Bossier Parish 

Louisiana East Baton Rouge Parish 

Louisiana Iberville Parish 

Louisiana Jefferson Parish 

Louisiana Livingston Parish 

Louisiana West Baton Rouge Parish 

Maine Hancock Co 

Maine York Co 

Maryland Anne Arundel Co 

Maryland Baltimore Co 

Maryland Carroll Co 

Maryland Cecil Co 

Maryland Charles Co 

2010 Projected 8-hour Ozone 

Concentration (ppb)a 

80.8 

92.2 

80.1 

90.6 

91.3 

83.4 

82.7 

85 

78.7 

84.7 

80.3 

80 

79.4 

76.6 

81.9 

78.7 

76.7 

85.1 

80.3 

80.4 

81.8 

77 

76.8 

76.6 

78.1 

78.4 

81.7 

80.4 

81.8 

82.8 

78.6 

79.6 

81.1 

81.6 

77.8 

81.5 

77 

80.6 

79.4 

78.6 

77.8 

78.8 

80.5 

80.2 

88.6 

83.7 

80 

89.5 

78.7 

2000 popb 2010 popc 

50,866 52,889 

882,567 891,694 

857,183 859,080 

155,071 164,202 

824,008 829,181 

259,088 267,199 

136,364 142,988 

572,058 554,474 

126,697 139,376 

500,264 534,631 

156,638 181,962 

153,887 158,291 

607,750 744,488 

89,215 111,522 

665,864 698,335 

92,174 114,380 

91,263 117,580 

816,005 855,826 

119,341 153,957 

70,111 87,977 

5,376,739 5,363,464 

21,668 22,905 

644,356 731,690 

260,077 307,400 

46,107 54,035 

96,472 107,096 

182,740 230,565 

55,391 65,282 

110,106 111,566 

484,563 489,220 

133,358 137,710 

860,453 879,932 

146,798 165,350 

43,445 46,565 

265,559 275,031 

88,616 92,109 

98,310 110,838 

412,852 465,411 

33,320 33,089 

455,466 493,359 

91,814 124,895 

21,601 22,672 

51,791 53,886 

186,742 201,082 

489,656 543,785 

754,292 792,284 

150,897 179,918 

85,951 96,574 

120,546 145,763 

2-10 
Air Quality, Health, and Welfare Concerns 

Maryland Frederick Co 78.1 195,277 234,304
 

Maryland Harford Co 92.8 218,590 268,207
 

Maryland Kent Co 85.8 19,197 20,233
 

Maryland Montgomery Co 79.3 873,341 940,126
 

Maryland Prince Georges Co 84.2 801,515 842,221
 

Massachusetts Barnstable Co 83.6 222,230 249,495
 

Massachusetts Bristol Co 83 534,678 558,460
 

Massachusetts Essex Co 81.7 723,419 747,556
 

Massachusetts Hampden Co 80.2 456,228 452,718
 

Massachusetts Hampshire Co 78 152,251 158,130
 

Massachusetts Middlesex Co 79.1 1,465,396 1,486,428
 

Massachusetts Suffolk Co 78.1 689,807 674,179
 

Michigan Allegan Co 82.1 105,665 121,415 

Michigan Benzie Co 77.9 15,998 17,849 

Michigan Berrien Co 78.1 162,453 164,727 

Michigan Cass Co 78.2 51,104 53,544 

Michigan Genesee Co 76.7 436,141 441,196 

Michigan Macomb Co 85.4 788,149 838,353 

Michigan Mason Co 78.9 28,274 30,667 

Michigan Muskegon Co 82 170,200 175,901 

Michigan Oakland Co 80.7 1,194,155 1,299,592 

Michigan Ottawa Co 76.6 238,314 277,400 

Michigan St Clair Co 80.6 164,235 178,391 

Michigan Washtenaw Co 81 322,895 344,398 

Michigan Wayne Co 84.7 2,061,161 1,964,209 

Missouri Clay Co 76.5 184,006 213,643 

Missouri Jefferson Co 76.7 198,099 230,539 

Missouri St Charles Co 80.5 283,883 341,686 

Missouri St Louis City 79.4 348,188 324,156 

Missouri St Louis Co 80.5 1,016,315 1,024,964 

New Hampshire Hillsborough Co 76.6 380,841 412,071 

New Jersey Atlantic Co 80.4 252,552 269,754 

New Jersey Bergen Co 86 884,118 898,450 

New Jersey Camden Co 91.6 508,932 509,912 

New Jersey Cumberland Co 84.4 146,438 149,595 

New Jersey Gloucester Co 91.3 254,673 278,612 

New Jersey Hudson Co 84.3 608,975 607,256 

New Jersey Hunterdon Co 88.6 121,989 139,641 

New Jersey Mercer Co 95.2 350,761 359,912 

New Jersey Middlesex Co 92.1 750,162 805,537 

New Jersey Monmouth Co 86.4 615,301 670,971 

New Jersey Morris Co 85.5 470,212 500,033 

New Jersey Ocean Co 100.3 510,916 572,364 

New Jersey Passaic Co 79.7 489,049 495,610 

New York Bronx Co 79.7 1,332,649 1,298,206 

New York Chautauqua Co 81.8 139,750 139,909 

New York Dutchess Co 81 280,150 291,098 

New York Erie Co 86.9 950,265 953,085 

New York Essex Co 77.6 38,851 39,545 

New York Jefferson Co 80.5 111,738 113,075 

New York Monroe Co 76.9 735,343 745,350 

New York Niagara Co 82.3 219,846 220,407 

New York Orange Co 77.1 341,367 371,434 

New York Putnam Co 82.3 95,745 107,967 

New York Queens Co 78.3 2,229,379 2,239,026 

New York Richmond Co 87.1 443,728 488,728 

New York Suffolk Co 90.8 1,419,369 1,472,127 

New York Westchester Co 84.7 923,459 944,535 

2-11 
Draft Regulatory Impact Analysis 

North Carolina Mecklenburg Co 

North Carolina Rowan Co 

North Carolina Wake Co 

Ohio Allen Co 

Ohio Ashtabula Co 

Ohio Butler Co 

Ohio Clermont Co 

Ohio Clinton Co 

Ohio Cuyahoga Co 

Ohio Delaware Co 

Ohio Franklin Co 

Ohio Geauga Co 

Ohio Hamilton Co 

Ohio Knox Co 

Ohio Lake Co 

Ohio Lorain Co 

Ohio Lucas Co 

Ohio Medina Co 

Ohio Portage Co 

Ohio Summit Co 

Ohio Trumbull Co 

Ohio Warren Co 

Ohio Wood Co 

Oklahoma Tulsa Co 

Pennsylvania Allegheny Co 

Pennsylvania Armstrong Co 

Pennsylvania Beaver Co 

Pennsylvania Berks Co 

Pennsylvania Bucks Co 

Pennsylvania Cambria Co 

Pennsylvania Chester Co 

Pennsylvania Dauphin Co 

Pennsylvania Delaware Co 

Pennsylvania Erie Co 

Pennsylvania Franklin Co 

Pennsylvania Lancaster Co 

Pennsylvania Lehigh Co 

Pennsylvania Mercer Co 

Pennsylvania Montgomery Co 

Pennsylvania Northampton Co 

Pennsylvania Philadelphia Co 

Pennsylvania Washington Co 

Pennsylvania Westmoreland Co 

Pennsylvania York Co 

Rhode Island Kent Co 

Rhode Island Providence Co 

Rhode Island Washington Co 

South Carolina Richland Co 

Tennessee Sevier Co 

Tennessee Shelby Co 

Texas Brazoria Co 

Texas Collin Co 

Texas Dallas Co 

Texas Denton Co 

Texas Galveston Co 

Texas Gregg Co 

Texas Harris Co 

Texas Jefferson Co 

81.4 

80.1 

77.2 

76.8 

83.5 

78 

78 

81.4 

77.3 

77.3 

81.9 

86.6 

78.6 

76.5 

82.2 

78.5 

80 

76.5 

79.8 

82.4 

79.7 

80 

77.4 

79.2 

81.9 

79.7 

79.6 

81.7 

94.3 

76.9 

85.4 

80.8 

84 

79.1 

80.2 

83.6 

82.1 

78.1 

87.6 

81.8 

89.9 

77.3 

76.7 

79.4 

86.2 

81.2 

84.2 

76.9 

76.5 

76.7 

84.1 

82.5 

82.2 

86.8 

84.6 

79.1 

97.4 

85 

695,453 814,088 

130,340 143,729 

627,846 787,707 

108,473 106,900 

102,728 104,850 

332,806 384,410 

177,977 205,365 

40,543 47,137 

1,393,977 1,348,313 

109,989 136,125 

1,068,977 1,142,894 

90,895 102,083 

845,302 843,226 

54,500 59,435 

227,511 237,161 

284,664 292,040 

455,053 447,302 

151,095 173,985 

152,061 162,685 

542,898 552,567 

225,116 226,157 

158,383 186,219 

121,065 129,124 

563,299 610,536 

1,281,665 1,259,040 

72,392 72,829 

181,412 183,693 

373,637 388,194 

597,635 648,796 

152,598 146,811 

433,501 478,460 

251,798 265,019 

550,863 543,169 

280,843 284,835 

129,313 135,088 

470,657 513,684 

312,090 323,215 

120,293 122,546 

750,097 772,849 

267,066 279,797 

1,517,549 1,420,803 

202,897 205,153 

369,993 372,941 

381,750 404,807 

167,090 174,126 

621,602 621,355 

123,546 137,756 

320,677 349,826 

71,170 96,097 

897,471 958,501 

241,767 281,960 

491,675 677,868 2,218,899 2,382,657 

432,976 554,033 

250,158 283,963 

111,379 121,241 

3,400,577 3,770,129 

252,051 260,847 

2-12 
Air Quality, Health, and Welfare Concerns 

Texas Johnson Co 78.2 126,811 157,545 

Texas Montgomery Co 81.2 293,768 413,048 

Texas Tarrant Co 87.2 1,446,219 1,710,920 

Virginia Alexandria City 80.9 128,283 130,422 

Virginia Arlington Co 86 189,453 193,370 

Virginia Charles City Co 77.7 6,926 7,382 

Virginia Fairfax Co 85.4 969,749 1,085,483 

Virginia Hampton City 78.7 146,437 153,246 

Virginia Hanover Co 80.9 86,320 98,586 

Virginia Henrico Co 78.2 262,300 294,174 

Virginia Loudoun Co 78.6 169,599 214,469 

Virginia Suffolk City 77.5 63,677 69,003 

Wisconsin Door Co 82.1 27,961 30,508 

Wisconsin Kenosha Co 91 149,577 166,359 

Wisconsin Kewaunee Co 79.9 20,187 20,538 

Wisconsin Manitowoc Co 80 82,887 83,516 

Wisconsin Milwaukee Co 82.1 940,164 922,943 

Wisconsin Ozaukee Co 85.8 82,317 95,549 

Wisconsin Racine Co 83.9 188,831 199,178 

Wisconsin Sheboygan Co 87.7 112,646 118,866 

Number of Violating Counties 37 

Population of Violating Counties 22,724,010 24,264,574 

Number of Counties within 10% 148 

Population of Counties within 10% 58,453,962 61,409,062 

a) Bolded concentrations indicate levels above the 8-hour ozone standard.
 

b) Populations are based on 2000 census data.
 

c) Populations are based on 2000 census projections.
 

The CAMx model also contains a source apportionment tool which can be used to 

estimate how emissions from individual source areas and regions impact modeled ozone 

concentrations. Small SI and Marine SI sector contributions were calculated for the areas which 

the CAIR modeling projected to have design values at or above 85 ppb in 2020. In those areas, 

Small SI and Marine SI emissions were estimated to be responsible for between one and seven 

percent of the ozone concentrations above 85 ppb. Additional information on the source 

apportionment tool and analysis can be found in the air quality modeling TSD for this proposal. 

We have described the current nonattainment with the 8-hour ozone NAAQS and that 

absent additional controls, modeling predicts that there will continue to be people living in 

counties with 8-hour ozone levels above the NAAQS in the future. In addition, we have 

described how in the future, in areas which are projected to have ozone levels greater than 85 

ppb, Small SI engines and equipment and Marine SI engines and vessels are projected to 

contribute to these ozone concentrations. 

These analyses demonstrate the need for reductions in emissions from this proposed rule. 

As shown earlier in Figure 2-1, unhealthy ozone concentrations occur over wide geographic 

areas and the engines, vessels and equipment covered in this proposed rule contribute to the 

ozone precursors in and near these areas. Thus, reductions in ozone precursors from Small SI 

engines and equipment and Marine SI engines and vessels are needed to assist States in attaining 

and maintaining the 8-hour ozone NAAQS and reducing ozone exposures. 

2-13 
Draft Regulatory Impact Analysis 

2.1.3.2.3 Modeling Projections of ozone with the proposed controls 

This section summarizes the results of our modeling of ozone air quality impacts in the 

future due to the reductions in Small SI engine and equipment and Marine SI engine and vessel 

emissions proposed in this action. Specifically, we compare baseline scenarios to scenarios with 

the proposed controls. Our modeling indicates that the reductions from this proposed rule would 

contribute to reducing ambient ozone concentrations and potential exposures in future years. 

On a population-weighted basis, the average change in future year design values for the 

eastern U.S. would be a decrease of 0.7 ppb in 2020 and 0.8 ppb in 2030. In areas with larger 

design values, greater than 85 ppb, the population-weighted average decrease would be 

somewhat higher, 0.8 ppb in 2020 and 1.0 ppb in 2030. 

Table 2.1-2 shows the average change in future year eight-hour ozone design values. 

Average changes are shown 1) for all counties with 2001-2003 8-hour ozone design values, 2) 

for counties with design values that did not meet the standard in 2001-2003 (“violating” 

counties), and 3) for counties that met the standard, but were within 10 percent of it in 2001­

2003. This last category is intended to reflect counties that meet the standard, but will likely 

benefit from help in maintaining that status in the face of growth. The average and populationweighted average over all counties in Table 2.1-2 demonstrates a broad improvement in ozone 

air quality. The average across violating counties shows that the proposed rule would help bring 

these counties into attainment. Since some of the VOC and NOx emission reductions expected 

from this proposed rule would go into effect during the period when areas will need to attain the 

8-hour ozone NAAQS, the projected reductions in emissions are expected to assist States and 

local agencies in their effort to attain and maintain the 8-hour ozone standard. The average over 

counties within ten percent of the standard shows that the proposed rule would also help those 

counties to maintain the standard. All of these metrics show a decrease in 2020 and a larger 

decrease in 2030, indicating in four different ways the overall improvement in ozone air quality. 

2-14 
Air Quality, Health, and Welfare Concerns 

Table 2.1-2: Average Change in Projected Future Year 8-hour Ozone Design Value 

Averagea 

Number of Eastern 

Counties 

change in 2020 design 

valueb

 (ppb) 

change in 2030 design 

valueb 

(ppb) 

All 525 -0.5 -0.7 

All, population-weighted 525 -0.7 -0.8 

Violating countiesc 270 -0.6 -0.8 

Violating countiesc

, populationweighted 270 -0.8 -1.0 

Counties within 10 percent of the 

standardd 

185 -0.4 -0.5 

Counties within 10 percent of the 

standardd 

, 

population-weighted 

185 -0.5 -0.7 

a

 averages are over counties with 2001 modeled design values b

 assuming the nominal modeled control scenario c

 counties whose 2001 design values exceeded the 8-hour ozone standard (>= 85 ppb) 

d

 counties whose 2001 design values were less than but within 10 percent of the 8-hour ozone standard (between 77 

and 85 ppb) 

The impact of the proposed reductions has also been analyzed with respect to those areas 

that have the highest projected design values. We project that there will be 13 Eastern counties 

with design values at or above 85 ppb in 2030. After implementation of this proposed action, we 

project that 7 of these 13 counties would be at least 40% closer to a design value of less than 85 

ppb, and on average all 13 counties would be 35% closer to a design value of less than 85 ppb. 

2.1.4 Environmental Effects of Ozone Pollution 

There are a number of public welfare effects associated with the presence of ozone in the 

ambient air.34 In this section we discuss the impact of ozone on plants, including trees, 

agronomic crops and urban ornamentals. 

 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”.35 Like carbon dioxide (CO2) and other 

gaseous substances, ozone enters plant tissues primarily through apertures (stomata) in leaves in 

a process called “uptake”. To a lesser extent, ozone can also diffuse directly through surface 

layers to the plant's interior.36 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.37, 38 This 

damage is commonly manifested as visible foliar injury such as chlorotic or necrotic spots, 

2-15 
Draft Regulatory Impact Analysis 

increased leaf senescence (accelerated leaf aging) and/or as reduced photosynthesis. All these 

effects reduce a plant’s capacity to form carbohydrates, which are the primary form of energy 

used by plants.39 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 some 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.40 

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).41, 42, 43 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.44 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 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.45, 46 

In terms of forest productivity and ecosystem diversity, ozone may be the pollutant with the 

greatest potential for regional-scale forest impacts.47 Studies have demonstrated repeatedly that 

ozone concentrations commonly observed in polluted areas can have substantial impacts on plant 

function.48,49 

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.50 In most instances, responses to chronic or 

recurrent exposure in forest exosystems are subtle and not observable for many years. These 

injuries can cause stand-level forest decline in sensitive ecosystems.51, 52, 53 It is not yet possible 

to predict ecosystem responses to ozone with much certainty; however, considerable knowledge 

2-16 
Air Quality, Health, and Welfare Concerns 

of potential ecosystem responses has been acquired through long-term 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.”54 In addition, economic studies have shown reduced 

economic benefits as a result of predicted reductions in crop yields associated with observed 

ozone levels.55, 56, 57 

Urban ornamentals represent an additional vegetation category likely to experience some 

degree of negative effects associated with exposure to ambient ozone levels and likely to impact 

large economic sectors. 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.58 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. Methods are not available to 

allow for plausible estimates of the percentage of these expenditures that may be related to 

impacts associated with ozone exposure. 

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 HCs and NOx from the 

engines, vessels and equipment subject to this proposed rule contribute to these PM 

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

monitored PM concentrations, air quality modeling done for recent EPA rulemakings 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. PM is further described by 

breaking it down into size fractions. PM10 refers to particles generally less than or equal to 10 

micrometers (μm) in diameter. PM2.5 refers to fine particles, those particles generally less than 

or equal to 2.5 μm in diameter. Inhalable (or "thoracic") coarse particles refer to those particles 

generally greater than 2.5 μm but less than or equal to 10 μm in diameter. Ultrafine PM refers to 

particles with diameters generally less than 100 nanometers (0.1 μm). Larger particles (>10 μm) 

tend to be removed by the respiratory clearance mechanisms, whereas smaller particles are 

deposited deeper in the lungs. 

2-17 
Draft Regulatory Impact Analysis 

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. 

The engines, vessels and equipment that would be covered by the proposed standards 

contribute to ambient PM levels through primary (direct) and secondary (indirect) PM. Primary 

PM is directly emitted into the air, and secondary PM forms in the atmosphere from gases 

emitted by fuel combustion and other sources. Along with primary PM, the engines, vessels and 

equipment controlled in this action emit HC and NOx, which react in the atmosphere to form 

secondary PM2.5. Both types of directly and indirectly formed particles from Small SI engines 

and equipment and Marine SI engines and vessels are found principally in the fine fraction. 

EPA has recently amended the PM NAAQS (71 FR 61144, October 17, 2006). The final 

rule, signed on September 21, 2006 and published on October 17, 2006, addressed revisions to 

the primary and secondary NAAQS for PM to provide increased protection of public health and 

welfare, respectively. The primary PM2.5 NAAQS include 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 15 μg/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 shall be within 10 percent of the spatially averaged annual mean, and (2) the daily 

values for each monitoring site pair shall yield a correlation coefficient of at least 0.9 for each 

calendar quarter. With regard to the primary PM10 standards, the 24-hour PM10 NAAQS was 

retained at a level of 150 μg/m3

 not to be exceeded more than once per year on average over a 

three-year period. Given that the available evidence does not suggest an association between 

long-term exposure to coarse particles at current ambient levels and health effects, EPA has 

revoked the annual PM10 standard. 

With regard to the secondary PM standards, 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, retained the annual PM2.5 and 24-hour PM10 secondary standards, and revoked 

the annual PM10 secondary standards. This suite of secondary PM 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. 

2-18 
Air Quality, Health, and Welfare Concerns 

2.2.2 Health Effects of PM 

As stated in the EPA Particulate Matter Air Quality Criteria Document (PM AQCD), 

available scientific findings “demonstrate well that human health outcomes are associated with 

ambient PM.”5 We are relying primarily 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.59,60 We also present additional 

recent studies published after the cut-off date for the PM AQCD.6, 61 Taken together this 

information supports the conclusion that PM-related emissions from Small SI engines and 

equipment and Marine SI engines and vessels are associated with adverse health effects. 

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 studies 

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 established a specific influence of mobile source-related PM2.5 on daily 

mortality62 and a concentration-response function for mobile source-associated PM2.5 and daily 

mortality.63 Another recent study in 14 U.S. cities examined the effect of PM10 exposures on 

daily hospital admissions for cardiovascular disease. They 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 

5

 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. 

6

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. 

2-19 
Draft Regulatory Impact Analysis 

PM10 when compared with other sources.64 These studies provide evidence that PM-related 

emissions, specifically from mobile sources, are associated with adverse health effects. 

2.2.2.2 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 proposal, the PM AQCD also notes 

that the PM components of gasoline and diesel engine exhaust represent 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).65,66,67 These studies indicate that there are significant 

associations for all-cause, cardiopulmonary, and lung cancer mortality with long-term exposure 

to PM2.5. A variety of studies have been published since the completion of the PM AQCD. One 

such study, an 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.68 EPA is assessing the significance of this study within the context 

of the broader literature. 

As discussed in the PM AQCD, the morbidity studies that combine the features of crosssectional 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). One such study, which was summarized in the 2006 Provisional Assessment, 

reported the results of a cross-sectional study of outdoor PM2.5 and measures of atherosclerosis in 

the Los Angeles basin.69 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. EPA is assessing the significance of this study 

within the context of the broader literature. 

2.2.2.3 Roadway-Related Exposure and Health Studies 

A recent body of studies reinforces the findings of these PM morbidity and mortality 

effects by looking at traffic-related exposures, PM measured along roadways, or time spent in 

traffic and adverse health effects. While many of these studies did not measure PM specifically, 

they include potential exhaust exposures which include mobile source PM because they employ 

indices such as roadway proximity or traffic volumes. One study with specific relevance to 

2-20 
Air Quality, Health, and Welfare Concerns 

PM2.5 health effects is a study that 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.70 A number of 

studies of traffic-related pollution have shown associations between fine particles and adverse 

respiratory outcomes in children who live near major roadways. 71,72,73 Additional information 

on near-roadway health effects is included in the recent Mobile Source Air Toxics rule (72 FR 

8428, February 26, 2007). 

2.2.3 Current and Projected PM Levels 

The proposed emission reductions from this rule would 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. The emission reductions would also help continue 

to lower ambient PM levels and resulting health impacts into the future. In this section we 

present information on current and future attainment of the PM standards. 

2.2.3.1 Current PM2.5 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 (using 2001-2003 or 2002-2004 measurements) and a number of other factors.7(70 FR 

943, January 5, 2005; 70 FR 19844, April 14, 2005) These areas are comprised of 208 full or 

partial counties with a total population exceeding 88 million.8 As mentioned in Section 2.2.1, 

the 1997 PM2.5 NAAQS were recently revised and the 2006 PM2.5 NAAQS became effective on 

December 18, 2006. Nonattainment areas will be designated with respect to the new 2006 PM 

NAAQS in early 2010. Table 2.2-1 presents the number of counties in areas currently 

designated as nonattainment for the 1997 PM2.5 NAAQS as well as the number of additional 

counties which have monitored data that is violating the 2006 PM2.5 NAAQS. 

7

 The full details involved in calculating a PM2.5 design value are given in Appendix N of 40 CFR Part 50. 

8

The PM2.5 nonattainment areas are listed in a Memo to the Docket titled “Nonattainment Areas and 

Mandatory Class I Federal Areas” and contained in Docket EPA-HQ-OAR-2004-0008. 

2-21 
Draft Regulatory Impact Analysis 

Table 2.2-1. Fine Particle Standards: Current 

Nonattainment Areas and Other Violating Counties 

Number of 

Counties 

Population1 

1997 PM2.5 Standards: 39 areas currently designated 208 88,394,000 

2006 PM2.5 Standards: Counties with violating monitors2 49 18,198,676 

Total 257 106,592,676 1

 Population numbers are from 2000 census data. 
 2

 This table provides an estimate of the counties violating the 2006 PM2.5 NAAQS based on 2003-05 air quality data. 
 

The areas designated as nonattainment for the 2006 PM2.5 NAAQS will be based on 3 years of air quality data from
 

later years. Also, the county numbers in the summary table includes only the counties with monitors violating the
 

2006 PM2.5 NAAQS. The monitored county violations may be an underestimate of the number of counties and
 

populations that will eventually be included in areas with multiple counties designated nonattainment.
 

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.9 The attainment dates associated with the potential nonattainment areas 

based on the 2006 PM2.5 NAAQS would likely be in the 2015 to 2020 timeframe. The emission 

standards being proposed in this action would become effective between 2008 and 2013. The 

expected PM2.5 inventory reductions from the standards proposed in this action would be useful 

to states in attaining or maintaining the PM2.5 NAAQS. 

2.2.3.2 Current PM10 Levels 

EPA designated PM10 nonattainment areas in 1990.10 As of October 2006, approximately 

28 million people live in the 46 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.11 

9

The EPA finalized PM2.5 attainment and nonattainment areas in April 2005. The EPA finalized the PM 

Implementation rule in March 2007. 

10A 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. 

11The PM10 nonattainment areas are listed in a Memo to the Docket titled “Nonattainment Areas and 

Mandatory Class I Federal Areas” and contained in Docket EPA-HQ-OAR-2004-0008. 

2-22 
Air Quality, Health, and Welfare Concerns 

2.2.3.3 Projected PM2.5 Levels 

Recent air quality modeling predicts that without additional controls there will continue 

to be a need for reductions in PM concentrations in the future. In the following sections we 

describe the recent PM air quality modeling and results of the modeling. 

2.2.3.3.1 PM Modeling Methodology 

Recently PM air quality analyses were performed for the PM NAAQS final rule, which 

was promulgated by EPA in 2006. The Community Multiscale Air Quality (CMAQ) model was 

used as the tool for simulating base and future year concentrations of PM, visibility and 

deposition in support of the PM NAAQS air quality assessments. The PM NAAQS analysis 

included all federal rules up to and including the Clean Air Interstate Rule (CAIR) and all final 

mobile source rule controls as of October 2006. Details on the PM air quality modeling are 

provided in the RIA for the final PM NAAQS rule, included in the docket for this proposed rule. 

2.2.3.3.2 Areas at Risk of Future PM2.5 Violations 

Air quality modeling performed for the final PM NAAQS indicates that in the absence of 

additional local, regional or national controls, there will likely continue to be counties that will 

not attain some combination of the annual 2006 PM2.5 standard (15 μg/m3) and the daily 2006 

PM2.5 standard (35 μg/m3). The PM NAAQS analysis provides estimates of future PM2.5 levels 

across the country. For example, in 2015 based on emission controls currently adopted or 

expected to be in place12, we project that 53 million people will live in 52 counties with projected 

PM2.5 design values at and above the 2006 standard, see Table 2.2-2.13 The proposed rule would 

provide emission reductions that will help areas to attain the PM2.5 NAAQS. Table 2.2-2 also 

lists the 54 counties, where 27 million people are projected to live, with 2015 projected design 

values that do not violate the PM2.5 NAAQS but are within ten percent of it. The proposed rule 

may help ensure that these counties continue to maintain their attainment status. 

Table 2.2-2 Counties with 2015 Projected PM2.5 Design Values 
 

Above and within 10% of the 2006 PM2.5 Standard
 

State County 2015 Projected 

Annual PM2.5 Design 

Value (μg/m3

)

a 

2015 Projected Daily 

PM2.5 Design Value 

(μg/m3

)

a 

2015 Populationb 

Alabama Jefferson Co 15.9 36.9 669,850 

California Alameda Co 13.3 59.4 1,628,698 

California Butte Co 13.4 50.7 242,166 

12Counties forecast to remain in nonattainment may need to adopt additional local or regional controls to 

attain the standards by dates set pursuant to the Clean Air Act. The emissions reductions associated with this 

proposed rule would help these areas attain the PM standards by their statutory date. 

13Note that this analysis identifies only counties projected to have a violating monitor; the number of 

counties to be designated and the associated population would likely exceed these estimates. 

2-23 
California 

Colusa Co 

California Contra Costa Co 

California Fresno Co 

California Imperial Co 

California Inyo Co 

California Kern Co 

California Kings Co 

California Los Angeles Co 

California Merced Co 

California Orange Co 

California Placer Co 

California Riverside Co 

California Sacramento Co 

California San Bernardino Co 

California San Diego Co 

California San Francisco Co 

California San Joaquin Co 

California San Luis Obispo Co 

California San Mateo Co 

California Santa Clara Co 

California Solano Co 

California Sonoma Co 

California Stanislaus Co 

California Sutter Co 

California Tulare Co 

California Ventura Co 

California Yolo Co 

Connecticut Fairfield Co 

Georgia Bibb Co 

Georgia Clayton Co 

Georgia DeKalb Co 

Georgia Floyd Co 

Georgia Fulton Co 

Georgia Muscogee Co 

Georgia Wilkinson Co 

Idaho Ada Co 

Idaho Bannock Co 

Idaho Canyon Co 

Idaho Power Co 

Idaho Shoshone Co 

Illinois Cook Co 

Illinois Madison Co 

Illinois St. Clair Co 

Illinois Will Co 

Indiana Clark Co 

Indiana Lake Co 

Indiana Marion Co 

Kentucky Jefferson Co 

Maryland Anne Arundel Co 

Maryland Baltimore city 

Maryland Baltimore Co 

Massachusetts Hampden Co 

Michigan Kalamazoo Co 

Michigan Kent Co 

9.5 

12.6 

20.1 

14.8 

6.1 

21.3 

17.2 

23.7 

15.8 

20.0 

11.4 

27.8 

12.2 

24.6 

15.8 

11.3 

15.4 

9.4 

10.5 

10.7 

11.7 

10.0 

16.6 

11.2 

21.2 

14.1 

10.2 

11.0 

13.7 

13.9 

13.6 

14.0 

15.5 

13.4 

13.6 

8.9 

9.1 

9.2 

10.5 

12.4 

15.5 

15.2 

14.6 

13.2 

13.6 

13.4 

13.5 

13.8 

11.1 

13.0 

11.3 

11.6 

12.8 

12.0 

33.5 23,066 

61.3 1,155,323 

73.0 960,934 

45.7 173,482 

38.1 19,349 

81.4 804,940 

70.6 161,607 

62.2 9,910,805 

54.4 250,152 

41.1 3,467,120 

38.1 403,624 

73.5 2,015,955 

49.8 1,488,456 

65.7 2,157,926 

40.7 3,489,368 

52.5 765,846 

51.1 675,362 

35.8 304,079 

41.9 785,949 

48.5 1,899,727 

57.7 529,784 

38.9 569,486 

61.9 547,041 

39.3 99,716 

77.2 441,185 

38.8 923,205 

33.0 206,388 

31.6 893,629 

27.0 160,468 

28.7 280,476 

31.5 715,947 

30.9 97,674 

32.2 877,365 

34.2 197,634 

29.3 11,259 

32.2 397,456 

40.2 88,033 

32.6 154,137 

36.6 8,932 

36.2 15,646 

37.1 5,362,931 

35.5 271,854 

30.4 251,612 

32.0 634,068 

31.1 112,523 

40.8 490,795 

33.1 889,645 

33.4 710,231 

33.2 574,322 

35.5 596,076 

32.6 810,172 

32.9 452,055 

32.7 257,817 

31.9 654,449 
Michigan Oakland Co 13.0 33.2 1,355,670 

Michigan St. Clair Co 12.5 32.5 185,970 

Michigan Wayne Co 17.4 39.0 1,921,253 

Montana Lincoln Co 15.0 42.4 19,875 

Montana Missoula Co 10.6 32.1 118,303 

New Jersey Camden Co 11.1 32.1 512,135 

New Jersey Hudson Co 12.0 32.8 604,036 

New Jersey Union Co 12.2 32.8 525,096 

New York Bronx Co 12.8 33.2 1,283,316 

New York New York Co 14.0 33.2 1,551,641 

Ohio Cuyahoga Co 15.4 40.0 1,325,507 

Ohio Franklin Co 13.7 33.5 1,181,578 

Ohio Hamilton Co 14.3 34.2 841,858 

Ohio Jefferson Co 14.2 34.2 68,909 

Ohio Lucas Co 12.5 32.2 443,230 

Ohio Scioto Co 15.6 34.3 81,013 

Ohio Trumbull Co 12.1 34.2 227,546 

Oregon Jackson Co 10.9 37.6 250,169 

Oregon Klamath Co 10.1 39.1 69,423 

Oregon Lane Co 12.9 53.6 387,237 

Oregon Washington Co 9.0 32.0 639,839 

Pennsylvania Allegheny Co 16.5 53.4 1,245,917 

Pennsylvania Beaver Co 12.1 33.2 184,648 

Pennsylvania Berks Co 12.0 35.5 396,410 

Pennsylvania Dauphin Co 11.0 33.3 272,748 

Pennsylvania Lancaster Co 12.2 33.7 535,622 

Pennsylvania Lehigh Co 10.5 34.7 328,523 

Pennsylvania Mercer Co 11.0 31.6 123,577 

Pennsylvania Northampton Co 10.9 35.0 286,838 

Pennsylvania Philadelphia Co 13.3 35.2 1,372,037 

Pennsylvania York Co 12.3 35.9 417,408 

Tennessee Knox Co 13.6 29.6 448,931 

Utah Box Elder Co 8.6 39.0 49,878 

Utah Cache Co 12.5 51.9 114,729 

Utah Salt Lake Co 12.6 49.3 1,133,410 

Utah Utah Co 9.3 36.7 508,106 

Utah Weber Co 9.1 36.2 229,807 

Washington Clark Co 9.2 34.3 479,002 

Washington King Co 10.8 34.0 2,013,808 

Washington Pierce Co 11.1 43.0 879,363 

Washington Snohomish Co 11.3 40.1 782,319 

Washington Thurston Co 8.9 34.9 264,364 

Washington Yakima Co 9.6 34.9 261,452 

West Virginia Berkeley Co 12.0 32.7 99,349 

West Virginia Hancock Co 13.4 32.7 30,857 

West Virginia Kanawha Co 13.9 28.9 196,498 

Wisconsin Milwaukee Co 12.1 32.1 908,336 

Wisconsin Waukesha Co 11.8 32.4 441,482 

Wyoming Sheridan Co 10.5 31.8 28,623 

Number of Violating Counties 52 

Population of Violating Counties 53,468,515 

Number of Counties within 10% 54 

Population of Counties within 10% 26,896,926 

a

 Bolded concentrations indicate levels above the annual PM2.5 standard. b

 Populations are based on 2000 census projections. 
Draft 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, acid deposition, eutrophication, nitrification and 

fertilization, materials damage, and deposition of PM. 

2.2.4.1 Visibility Impairment 

Visibility can be defined as the degree to which the atmosphere is transparent to visible 

light.74 Visibility impairment manifests in two principal ways: as local visibility impairment 

and as regional haze.75 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 from 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 areas 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 directly affects people’s enjoyment of daily activities in 

all parts of the country. Individuals value good visibility for the well-being it provides them 

directly, both in 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. For 

more information on visibility see the 2004 PM AQCD as well as the 2005 PM Staff Paper.76,77 

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 set secondary PM2.5 standards which would 

act in conjunction with the establishment of a regional haze program. In setting this secondary 

standard, EPA concluded that PM2.5 causes adverse effects on visibility in various locations, 

depending on PM concentrations and factors such as chemical composition and average relative 

humidity. The secondary (welfare-based) PM2.5 NAAQS was established as equal to the suite of 

primary (health-based) NAAQS. Furthermore, section 169 of the Act provides additional 

authority to remedy existing visibility impairment and prevent future visibility impairment in the 

156 national parks, forests and wilderness areas labeled as mandatory class I federal areas (62 

FR 38680-81, July 18, 1997).1415 In July 1999 the regional haze rule (64 FR 35714) was put in 

place to protect the visibility in mandatory class I federal areas. Visibility can be said to be 

14 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. 

15The mandatory class I federal areas are listed in a Memo to the Docket titled “Nonattainment Areas and 

Mandatory Class I Federal Areas” and contained in Docket EPA-HQ-OAR-2004-0008. 

2-26 
Air Quality, Health, and Welfare Concerns 

impaired in both PM2.5 nonattainment areas and mandatory class I federal areas. 

EPA has determined that emissions from nonroad engines significantly contribute to air 

pollution that may be reasonably anticipated to endanger public health and welfare for visibility 

effects in particular (67 FR 68242, November 8, 2002). The hydrocarbon emissions from the 

Small SI engines and equipment subject to this proposed rule are PM-precursors and contribute 

to these visibility effects. This is evident in the PM and visibility modeling recently completed 

for the PM NAAQS and the CAIR. Small SI engines and equipment and Marine SI engines and 

vessels were included in the PM NAAQS and CAIR PM and visibility modeling which projected 

visibility problems persisting in the future.78,79 In this section we present current information and 

projected estimates about both 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 projected emission reductions from this 

proposed action would help improve visibility conditions across the country and in mandatory 

class I federal areas. 

2.2.4.1.1 Current Visibility Impairment 

The need for reductions in the levels of PM2.5 is widespread. Currently, high ambient 

PM2.5 levels are measured throughout the country. Fine particles may remain suspended for days 

or weeks and travel hundreds to thousands of kilometers, and thus fine particles emitted or 

created in one county may contribute to ambient concentrations in a neighboring region.80 

As mentioned above, the secondary PM2.5 standards were set as equal to the suite of 

primary PM2.5 standards. Recently designated PM2.5 nonattainment areas indicate that, as of 

October 2006, almost 90 million people live in 208 counties that are in nonattainment for the 

PM2.5 NAAQS. Thus, at least these populations (plus others who travel to these areas) would 

likely be experiencing visibility impairment. Emissions of PM precursors, such as 

hydrocarbons, from Small SI engines and equipment and Marine SI engines and vessels 

contribute to this 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.81,82 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.83 

The regional haze rule requires states to establish goals for each affected mandatory class 

I federal area to improve visibility on the haziest days (20% most impaired days) and ensure no 

degradation occurs on the cleanest days (20% least impaired days). Although there have been 

general trends toward improved visibility, progress is still needed on the haziest days. 

2-27 
Draft Regulatory Impact Analysis 

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.84 

2.2.4.1.3 Future Visibility Impairment 

Recent modeling for the final PM NAAQS rule was used to project PM2.5 levels in the 

U.S. in 2015. The results suggest that PM2.5 levels above the 2006 NAAQS will persist in the 

future. We predicted that in 2015, there will be 52 counties with a population of 53 million 

where PM2.5 levels will exceed the 2006 PM2.5 NAAQS. Thus, in the future, a percentage of the 

population may continue to experience visibility impairment in areas where they live, work and 

recreate. 

The emissions from Small SI engines and equipment and Marine SI engines and vessels 

contribute to visibility impairment. These emissions occur in and around areas with PM2.5 levels 

above the PM2.5 NAAQS. Thus, the emissions from these sources contribute to the current and 

anticipated visibility impairment and the proposed emission reductions would help improve 

future visibility impairment. 

2.2.4.1.4 Future Visibility Impairment at Mandatory Class I Federal Areas 

Achieving the PM2.5 NAAQS will help improve visibility across the country, but it will 

not be sufficient to meet the statutory goal of no manmade impairment in the mandatory class I 

federal areas (64 FR 35722, July 1, 1999 and 62 FR 38680, July 18, 1997). In setting the 

NAAQS, EPA discussed how the NAAQS in combination with the regional haze program, is 

deemed to improve visibility consistent with the goals of the Act.85 In the East, there are and 

will continue to be areas with PM2.5 concentrations above the PM2.5 NAAQS and where light 

extinction is significantly above natural background. Thus, large areas of the Eastern United 

States have air pollution that is causing and will continue to cause visibility problems. In the 

West, scenic vistas are especially important to public welfare. Although the PM2.5 NAAQS is 

met in most areas outside of California, virtually the entire West is in close proximity to a scenic 

mandatory class I federal area protected by 169A and 169B of the CAA. 

Recent modeling for the CAIR was used to project visibility conditions in mandatory 

class I federal areas across the country in 2015. The results for the mandatory class I federal 

areas suggest that these areas are predicted to continue to have visibility impairment above 

background on the 20% worst days in the future. 

The overall goal of the regional haze program is to prevent future visibility impairment 

and remedy existing visibility impairment in mandatory class I federal areas. As shown by the 

future visibility estimates in Table 2.2-3, it is projected that there will continue to be mandatory 

class I federal areas with visibility levels above background in 2015. Additional emission 

reductions will be needed from the broad set of sources that contribute, including the engines, 

vessels and equipment subject to this proposed rule.86 The reductions proposed in this action are 

2-28 
Air Quality, Health, and Welfare Concerns 

a part of the overall strategy to achieve the visibility goals of the Act and the regional haze 

program. 

Table 2.2-3: Current (1998-2002) Visibility, Projected (2015) Visibility, and Natural
 

Background Levels for the 20% Worst Days at 116 IMPROVE Sites
 

Class I Area Namea State 1998-2002 Baseline 

Visibility (deciviews)b 

2015 CAIR Control Case 

Visibilityc

 (deciviews) 

Natural Background 

(deciviews) 

Acadia ME 22.7 21.0 11.5 

Agua Tibia CA 23.2 23.2 7.2 

Alpine Lakes WA 18.0 17.4 7.9 

Anaconda - Pintler MT 12.3 12.2 7.3 

Arches UT 12.0 12.1 7.0 

Badlands SD 17.3 16.8 7.3 

Bandelier NM 13.2 13.2 7.0 

Big Bend TX 18.4 18.3 6.9 

Black Canyon of the Gunnison CO 11.6 11.4 7.1 

Bob Marshall MT 14.2 14.0 7.4 

Boundary Waters Canoe Area MN 20.0 19.0 11.2 

Bridger WY 11.5 11.3 7.1 

Brigantine NJ 27.6 25.4 11.3 

Bryce Canyon UT 12.0 11.9 7.0 

Cabinet Mountains MT 13.8 13.4 7.4 

Caney Creek AR 25.9 24.1 11.3 

Canyonlands UT 12.0 12.0 7.0 

Cape Romain SC 25.9 23.9 11.4 

Caribou CA 14.8 14.6 7.3 

Carlsbad Caverns NM 17.6 17.9 7.0 

Chassahowitzka FL 25.7 23.0 11.5 

Chiricahua NM AZ 13.9 13.9 6.9 

Chiricahua W AZ 13.9 13.9 6.9 

Craters of the Moon ID 14.7 14.7 7.1 

Desolation CA 12.9 12.8 7.1 

Dolly Sods WV 27.6 23.9 11.3 

Dome Land CA 20.3 19.9 7.1 

Eagle Cap OR 19.6 19.0 7.3 

Eagles Nest CO 11.3 11.4 7.1 

Emigrant CA 17.6 17.4 7.1 

Everglades FL 20.3 19.2 11.2 

Fitzpatrick WY 11.5 11.3 7.1 

Flat Tops CO 11.3 11.4 7.1 

Galiuro AZ 13.9 14.1 6.9 

Gates of the Mountains MT 11.2 10.8 7.2 

Gila NM 13.5 13.5 7.0 

Glacier MT 19.5 19.1 7.6 

Glacier Peak WA 14.0 13.8 7.8 

Grand Teton WY 12.1 12.0 7.1 

Great Gulf NH 23.2 21.2 11.3 

Great Sand Dunes CO 13.1 13.0 7.1 

Great Smoky Mountains TN 29.5 26.1 11.4 

Guadalupe Mountains TX 17.6 17.5 7.0 

Hells Canyon OR 18.1 18.0 7.3 

Isle Royale MI 21.1 20.1 11.2 

James River Face VA 28.5 25.1 11.2 

2-29 
Draft Regulatory Impact Analysis 

Jarbidge NV 12.6 12.8 7.1 

Joshua Tree CA 19.5 20.3 7.1 

Joyce Kilmer - Slickrock NC 29.5 26.1 11.5 

Kalmiopsis OR 14.8 14.4 7.7 

Kings Canyon CA 23.5 24.1 7.1 

La Garita CO 11.6 11.5 7.1 

Lassen Volcanic CA 14.8 14.6 7.3 

Lava Beds CA 16.6 16.5 7.5 

Linville Gorge NC 27.9 24.6 11.4 

Lostwood ND 19.6 18.7 7.3 

Lye Brook VT 23.9 21.1 11.3 

Mammoth Cave KY 30.2 27.0 11.5 

Marble Mountain CA 17.1 16.8 7.7 

Maroon Bells - Snowmass CO 11.3 11.3 7.1 

Mazatzal AZ 13.1 13.5 6.9 

Medicine Lake MT 17.7 17.1 7.3 

Mesa Verde CO 12.8 12.8 7.1 

Mingo MO 27.5 25.9 11.3 

Mission Mountains MT 14.2 14.0 7.4 

Mokelumne CA 12.9 12.8 7.1 

Moosehorn ME 21.4 20.3 11.4 

Mount Hood OR 14.0 13.7 7.8 

Mount Jefferson OR 15.7 15.2 7.8 

Mount Rainier WA 18.9 19.4 7.9 

Mount Washington OR 15.7 15.2 7.9 

Mount Zirkel CO 11.7 11.8 7.1 

North Cascades WA 14.0 14.0 7.8 

Okefenokee GA 26.4 24.7 11.5 

Otter Creek WV 27.6 24.0 11.3 

Pasayten WA 14.7 14.5 7.8 

Petrified Forest AZ 13.5 13.8 7.0 

Pine Mountain AZ 13.1 13.4 6.9 

Presidential Range - Dry NH 23.2 20.9 11.3 

Rawah CO 11.7 11.7 7.1 

Red Rock Lakes WY 12.1 12.1 7.1 

Redwood CA 16.5 16.5 7.8 

Rocky Mountain CO 14.1 14.1 7.1 

Roosevelt Campobello ME 21.4 20.1 11.4 

Salt Creek NM 17.7 17.3 7.0 

San Gorgonio CA 21.5 22.1 7.1 

San Jacinto CA 21.5 21.4 7.1 

San Pedro Parks NM 11.4 11.4 7.0 

Sawtooth ID 13.6 13.5 7.2 

Scapegoat MT 14.2 14.1 7.3 

Selway - Bitterroot MT 12.3 12.1 7.3 

Seney MI 23.8 22.6 11.4 

Sequoia CA 23.5 24.1 7.1 

Shenandoah VA 27.6 23.4 11.3 

Sierra Ancha AZ 13.4 13.7 6.9 

Sipsey AL 28.7 26.1 11.4 

South Warner CA 16.6 16.5 7.3 

Strawberry Mountain OR 19.6 19.2 7.5 

Superstition AZ 14.7 15.0 6.9 

Swanquarter NC 24.6 21.9 11.2 

2-30 
Air Quality, Health, and Welfare Concerns 

Sycamore Canyon AZ 16.1 16.6 7.0 

Teton WY 12.1 12.1 7.1 

Theodore Roosevelt ND 17.6 16.8 7.3 

Thousand Lakes CA 14.8 14.6 7.3 

Three Sisters OR 15.7 15.2 7.9 

UL Bend MT 14.7 14.1 7.2 

Upper Buffalo AR 25.5 24.3 11.3 

Voyageurs MN 18.4 17.6 11.1 

Weminuche CO 11.6 11.4 7.1 

West Elk CO 11.3 11.3 7.1 

Wind Cave SD 16.0 15.4 7.2 

Wolf Island GA 26.4 24.9 11.4 

Yellowstone WY 12.1 12.1 7.1 

Yolla Bolly - Middle Eel CA 17.1 16.9 7.4 

Yosemite CA 17.6 17.4 7.1 

Zion UT 13.5 13.3 7.0 

a

 116 IMPROVE sites represent 155 of the 156 Mandatory Class I Federal Areas. One isolated Mandatory Class I 

Federal Area (Bering Sea, an uninhabited and infrequently visited island 200 miles from the coast of Alaska), was 

considered to be so remote from electrical power and people that it would be impractical to collect routine aerosol 

samples.87 

b

 The deciview metric describes perceived visual changes in a linear fashion over its entire range, analogous to the 

decibel scale for sound. A deciview of 0 represents pristine conditions. The higher the deciview value, the worse the 

visibility, and an improvement in visibility is a decrease in deciview value. c

 The 2015 modeling projections are based on the Clear Air Interstate Rule analyses (EPA, 2005). 

2.2.4.2 Atmospheric Deposition 

Wet and dry deposition of ambient particulate matter delivers a complex mixture of 

metals (e.g., mercury, zinc, lead, nickel, aluminum, cadmium), organic compounds (e.g., POM, 

dioxins, furans) and inorganic compounds (e.g., nitrate, sulfate) to terrestrial and aquatic 

ecosystems. The chemical form of the compounds deposited is impacted by a variety of factors 

including ambient conditions (e.g., temperature, humidity, oxidant levels) and the sources of the 

material. Chemical and physical transformations of the particulate compounds occur in the 

atmosphere as well as the media onto which they deposit. These transformations in turn 

influence the fate, bioavailability and potential toxicity of these compounds. Atmospheric 

deposition has been identified as a key component of the environmental and human health 

hazard posed by several pollutants including mercury, dioxin and PCBs.88 

Adverse impacts on water quality can occur when atmospheric contaminants deposit to 

the water surface or when material deposited on the land enters a waterbody through runoff. 

Potential impacts of atmospheric deposition to waterbodies include those related to both nutrient 

and toxic inputs. Adverse effects to human health and welfare can occur from the addition of 

excess particulate nitrate nutrient enrichment which contributes to toxic algae blooms and zones 

of depleted oxygen, which can lead to fish kills, frequently in coastal waters. Particles 

contaminated with heavy metals or other toxins may lead to the ingestion of contaminated fish, 

ingestion of contaminated water, damage to the marine ecology, and limited recreational uses. 

Several studies have been conducted in U.S. coastal waters and in the Great Lakes Region in 8990919293 

which the role of ambient PM deposition and runoff is investigated. 

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Draft Regulatory Impact Analysis 

Adverse impacts on soil chemistry and plant life have been observed for areas heavily 

impacted by atmospheric deposition of nutrients, metals and acid species, resulting in species 

shifts, loss of biodiversity, forest decline and damage to forest productivity. Potential impacts 

also include adverse effects to human health through ingestion of contaminated vegetation or 

livestock (as in the case for dioxin deposition), reduction in crop yield, and limited use of land 

due to contamination. 

2.2.4.2.1 Acid Deposition 

Acid deposition, or acid rain as it is commonly known, occurs when NOx and SO2 react 

in the atmosphere with water, oxygen, and oxidants to form various acidic compounds that later 

fall to earth in the form of precipitation or dry deposition of acidic particles.94 It contributes to 

damage of trees at high elevations and in extreme cases may cause lakes and streams to become 

so acidic that they cannot support aquatic life. In addition, acid deposition accelerates the decay 

of building materials and paints, including irreplaceable buildings, statues, and sculptures that 

are part of our nation's cultural heritage. 

Acid deposition primarily affects bodies of water that rest atop soil with a limited ability 

to neutralize acidic compounds. The National Surface Water Survey (NSWS) investigated the 

effects of acidic deposition in over 1,000 lakes larger than 10 acres and in thousands of miles of 

streams. It found that acid deposition was the primary cause of acidity in 75 percent of the 

acidic lakes and about 50 percent of the acidic streams, and that the areas most sensitive to acid 

rain were the Adirondacks, the mid-Appalachian highlands, the upper Midwest and the high 

elevation West. The NSWS found that approximately 580 streams in the Mid-Atlantic Coastal 

Plain are acidic primarily due to acidic deposition. Hundreds of the lakes in the Adirondacks 

surveyed in the NSWS have acidity levels incompatible with the survival of sensitive fish 

species. Many of the over 1,350 acidic streams in the Mid-Atlantic Highlands (mid-Appalachia) 

region have already experienced trout losses due to increased stream acidity. Emissions from 

U.S. sources contribute to acidic deposition in Eastern Canada, where the Canadian government 

has estimated that 14,000 lakes are acidic. Acid deposition also has been implicated in 

contributing to degradation of high-elevation spruce forests that populate the ridges of the 

Appalachian Mountains from Maine to Georgia. This area includes national parks such as the 

Shenandoah and Great Smoky Mountain National Parks. 

A study of emission trends and acidity of water bodies in the Eastern United States by the 

General Accounting Office (GAO) found that from 1992 to 1999 sulfates declined in 92 percent 

of a representative sample of lakes, and nitrate levels increased in 48 percent of the lakes 

sampled.95 The decrease in sulfates is consistent with emission trends, but the increase in 

nitrates is inconsistent with the stable levels of nitrogen emissions and deposition. The study 

suggests that the vegetation and land surrounding these lakes have lost some of their previous 

capacity to use nitrogen, thus allowing more of the nitrogen to flow into the lakes and increase 

their acidity. Recovery of acidified lakes is expected to take a number of years, even where soil 

and vegetation have not been “nitrogen saturated,” as EPA called the phenomenon in a 1995 

study.96 This situation places a premium on reductions of NOx from all sources, including Small 

SI and Marine SI engines, vessels and equipment in order to reduce the extent and severity of 

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Air Quality, Health, and Welfare Concerns 

nitrogen saturation and acidification of lakes in the Adirondacks and throughout the United 

States. 

The NOx reductions from this rule would help reduce acid rain and acid deposition, 

thereby helping to reduce acidity levels in lakes and streams throughout the country and helping 

accelerate the recovery of acidified lakes and streams and the revival of ecosystems adversely 

affected by acid deposition. Reduced acid deposition levels will also help reduce stress on 

forests, thereby accelerating reforestation efforts and improving timber production. 

Deterioration of our historic buildings and monuments, and of buildings, vehicles, and other 

structures exposed to acid rain and dry acid deposition also will be reduced, and the costs borne 

to prevent acid-related damage may also decline. While the reduction in nitrogen acid 

deposition will be roughly proportional to the reduction in NOx emissions, respectively, the 

precise impact of this proposed rule will differ across different areas. 

2.2.4.2.2 Eutrophication, Nitrification and Fertilization 

In recent decades, human activities have greatly accelerated nutrient impacts, such as 

nitrogen deposition in both aquatic and terrestrial systems. Nitrogen deposition in aquatic 

systems can cause excessive growth of algae and lead to degraded water quality and associated 

impairment of fresh water and estuarine resources for human uses.97 Nitrogen deposition on 

terrestrial systems can cause fertilization and lead to ecosystem stress and species shift. 

Eutrophication is the accelerated production of organic matter, particularly algae, in a 

water body. This increased growth can cause numerous adverse ecological effects and economic 

impacts, including nuisance algal blooms, dieback of underwater plants due to reduced light 

penetration, and toxic plankton blooms. Algal and plankton blooms can also reduce the level of 

dissolved oxygen, which can adversely affect fish and shellfish populations. 

Deposition of nitrogen contributes to elevated nitrogen levels in waterbodies. The NOx 

reductions from today’s promulgated standards will help reduce the airborne nitrogen deposition 

that contributes to eutrophication of watersheds, particularly in aquatic systems where 

atmospheric deposition of nitrogen represents a significant portion of total nitrogen loadings. 

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 the 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.98 

In its Third Report to Congress on the Great Waters, EPA reported that atmospheric 

deposition contributes from 2 to 38 percent of the nitrogen load to certain coastal waters.99 A 

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Draft Regulatory Impact Analysis 

review of peer reviewed literature in 1995 on the subject of air deposition suggests a typical 

contribution of 20 percent or higher.100 Human-caused nitrogen loading to the Long Island 

Sound from the atmosphere was estimated at 14 percent by a collaboration of federal and state 

air and water agencies in 1997.101 The National Exposure Research Laboratory, U.S. EPA, 

estimated based on prior studies that 20 to 35 percent of the nitrogen loading to the Chesapeake 

Bay is attributable to atmospheric deposition.102 The mobile source portion of atmospheric NOx 

contribution to the Chesapeake Bay was modeled at about 30 percent of total air deposition.103 

In U.S. terrestrial systems, the nutrient whose supply most often sets the limit of possible 

plant based productivity at a given site is nitrogen. By increasing available nitrogen, overall 

ecosystem productivity may be expected to increase for a time, and then decline as nitrogen 

saturation is reached. However, because not all vegetation, organisms, or ecosystems react in the 

same manner to increased nitrogen fertilization, those plants or organisms that are predisposed to 

capitalize on any increases in nitrogen availability gain an advantage over those that are not as 

responsive to added nutrients, leading to a change in plant community composition and diversity. 

Changes to plant community composition and structure within an ecosystem are of concern 

because plants in large part determine the food supply and habitat types available for use by 

other organisms. Further, in terrestrial systems, plants serve as the integrators between aboveground and below-ground environments and influence nutrient, energy and water cycles. 

Because of these linkages, chronic excess nutrient nitrogen additions can lead to complex, 

dramatic, and severe ecosystem level responses such as changes in habitat suitability, genetic 

diversity, community dynamics and composition, nutrient status, energy and nutrient cycling, 

and frequency and intensity of natural disturbance regimes such as fire. 

These types of effects have been observed both experimentally and in the field. For 

example, experimental additions of nitrogen to a Minnesota grassland dominated by native 

warm-season grasses produced a shift to low-diversity mixtures dominated by coolseason 

grasses over a 12 year period at all but the lowest rate of nitrogen addition.104 Similarly, the 

coastal sage scrub (CSS) community in California has been declining in land area and in drought 

deciduous shrub density over the past 60 years, and is being replaced in many areas by the more 

nitrogen responsive Mediterranean annual grasses. Some 25 plant species are already extinct in 

California, most of them annual and perennial forbs that occurred in sites now experiencing 

conversion to annual grassland. As CSS converts more extensively to annual grassland 

dominated by invasive species, loss of additional rare species may be inevitable. Though 

invasive species are often identified as the main threat to rare species, it is more likely that 

invasive species combine with other factors, such as excess N deposition, to promote increased 

productivity of invasive species and resulting species shifts. 

Deposition of nitrogen from the engines covered in this proposal contributes to elevated 

nitrogen levels in bodies of water and on land. The NOx reductions proposed in this action will 

reduce the airborne nitrogen deposition that contributes to eutrophication of watersheds and 

nitrogen saturation on land. 

2.2.4.2.3 Heavy Metals 

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Air Quality, Health, and Welfare Concerns 

Heavy metals, including cadmium, copper, lead, chromium, mercury, nickel and zinc, 

have the greatest potential for influencing forest growth (PM AQCD, p. 4-87).105 Investigation 

of trace metals near roadways and industrial facilities indicate that a substantial burden 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).106 Contamination of 

plant leaves by heavy metals can lead to elevated soil levels. Some trace metals absorbed into 

the plant and can bind to the leaf tissue (PM AQCD, p. 4-75). When these leaves fall and 

decompose, the heavy metals are transferred into the soil.107,108 

The environmental sources and cycling of mercury are currently of particular concern 

due to the bioaccumulation and biomagnification of this metal in aquatic 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 a portion of emitted mercury to travel 

far from the primary source before being deposited and accumulating in the aquatic ecosystem. 

Localized or regional impacts are also observed for mercury emitted from combustion sources. 

The major source of mercury in the Great Lakes is from atmospheric deposition, accounting for 

approximately eighty percent of the mercury in Lake Michigan.109,110 Over fifty percent of the 

mercury in the Chesapeake Bay has been attributed to atmospheric deposition.111 Overall, the 

National Science and Technology Council (NSTC, 1999) identifies atmospheric deposition as 

the primary source of mercury to aquatic systems. 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.112,113 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.114 Plant uptake of platinum has been observed at these 

locations. 

2.2.4.2.4 Polycyclic Organic Matter 

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Draft Regulatory Impact Analysis 

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.115 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 :m 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.116 

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.117,118 Analyses of PAH deposition to Chesapeake and 

Galveston Bay indicate that dry deposition and gas exchange from the atmosphere to the surface 

water predominate.119,120 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.121 PAHs that enter a waterbody 

through gas exchange likely partition into organic rich particles and be biologically recycled, 

while dry deposition of aerosols containing PAHs tends to be more resistant to biological 

recycling.122 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, 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.123 Van Metre et al. (2000) noted PAH 

concentrations in urban reservoir sediments have increased by 200-300% over the last forty 

years and correlates with increases in automobile use.124 

Cousins et al. (1999) estimates that greater than ninety percent of semi-volatile organic 

compound (SVOC) emissions in the United Kingdom deposit on soil.125 An analysis of 

polycyclic aromatic hydrocarbon (PAH) concentrations near a Czechoslovakian roadway 

indicated that concentrations were thirty times greater than background.126 

2.2.4.2.5 Materials Damage and Soiling 

The deposition of airborne particles can also reduce the aesthetic appeal of buildings and 

culturally important articles through soiling, and can contribute directly (or in conjunction with 

other pollutants) to structural damage by means of corrosion or erosion.127 Particles affect 

materials principally by promoting and accelerating the corrosion of metals, by degrading paints, 

and by deteriorating building materials such as concrete and limestone. Particles contribute to 

these effects because of their electrolytic, hygroscopic, and acidic properties, and their ability to 

absorb corrosive gases (principally sulfur dioxide). The rate of metal corrosion depends on a 

number of factors, including the deposition rate and nature of the pollutant; the influence of the 

2-36 
Air Quality, Health, and Welfare Concerns 

metal protective corrosion film; the amount of moisture present; variability in the 

electrochemical reactions; the presence and concentration of other surface electrolytes; and the 

orientation of the metal surface. 

2.3 Gaseous Air Toxics 

Small SI and Marine SI emissions contribute to ambient levels of gaseous air toxics 

known or suspected as human or animal carcinogens, or that have non-cancer health effects. 

These compounds include benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein, 

polycyclic organic matter (POM), and naphthalene. All of 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. 

The reductions in Small SI and Marine SI emissions proposed in this rulemaking would help 

reduce exposure to these harmful substances. 

Air toxics can cause a variety of cancer and noncancer health effects. A number of the 

mobile source air toxic pollutants described in this section are known or likely to pose a cancer 

hazard in humans. Many of these compounds also cause adverse noncancer health effects 

resulting from chronic,16 subchronic,17 or acute18 inhalation exposures. These include 

neurological, cardiovascular, liver, kidney, and respiratory effects as well as effects on the 

immune and reproductive systems. 

Benzene: The EPA’s IRIS database lists benzene as a known human carcinogen (causing 

leukemia) by all routes of exposure, and 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.128, 129, 130 EPA states in its IRIS database that data indicate a causal 

relationship between benzene exposure and acute lymphocytic leukemia and suggests a 

relationship between benzene exposure and chronic non-lymphocytic leukemia and chronic 

lymphocytic leukemia. 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.131, 132 The most sensitive noncancer effect observed in humans, based on current data, 

is the depression of the absolute lymphocyte count in blood.133, 134 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. 

135, 136, 137, 138 EPA’s IRIS program has not yet evaluated these new data. 

16Chronic 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). 

17Defined in the IRIS database as exposure to a substance spanning approximately 10 of the lifetime of an 

organism. 

18Defined in the IRIS database as exposure by the oral, dermal, or inhalation route for 24 hours or less. 

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Draft Regulatory Impact Analysis 

1,3-Butadiene: EPA has characterized 1,3-butadiene as carcinogenic to humans by 

inhalation.139, 140 The specific mechanisms of 1,3-butadiene-induced carcinogenesis are 

unknown. However, it is virtually certain that the carcinogenic effects are mediated by 

genotoxic metabolites of 1,3-butadiene. Animal data suggest that females may be more sensitive 

than males for cancer effects; while 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.141 

Formaldehyde: Since 1987, EPA has classified formaldehyde as a probable human 

carcinogen based on evidence in humans and in rats, mice, hamsters, and monkeys.142 EPA’s 

current IRIS summary provides an upper bound cancer unit risk estimate of 1.3x10-5 per μg/m3. 

In other words, there is an estimated risk of about thirteen excess cancer cases in one million 

people exposed to 1 μg/m3

 of formaldehyde over a lifetime. 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.143, 144 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 workers exposed to formaldehyde.145 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. The agency is currently 

conducting a reassessment of the human hazard and dose-response associated with 

formaldehyde. 

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.146, 147, 148 CIIT’s risk assessment of 

formaldehyde incorporated mechanistic and dosimetric information on formaldehyde. The risk 

assessment analyzed carcinogenic risk from inhaled formaldehyde using approaches that are 

consistent with EPA’s draft guidelines for carcinogenic risk assessment. In 2001, Environment 

Canada relied on this cancer dose-response assessment in their assessment of formaldehyde.149 

Extended follow-up of a cohort of British chemical workers did not find evidence of an increase 

in nasopharyngeal or lymphohematopoetic cancers, but a continuing statistically significant 

excess in lung cancers was reported.150 

Based on the developments of the last decade, in 2004, EPA also relied on this cancer 

unit risk estimate during the development of the plywood and composite wood products national 

emissions standards for hazardous air pollutants (NESHAPs).151 In these rules, EPA concluded 

that the CIIT work represented the best available application of the available mechanistic and 

dosimetric science on the dose-response for portal of entry cancers due to formaldehyde 

exposures. 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 

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Air Quality, Health, and Welfare Concerns 

of the human hazard and dose-response associated with formaldehyde. 

Formaldehyde exposure also causes a range of noncancer health effects, including 

irritation of the eyes (tearing of the eyes and increased blinking) and mucous membranes. 

Acetaldehyde: Acetaldehyde is classified in EPA’s IRIS database as a probable human 

carcinogen, based on nasal tumors in rats, and is considered moderately toxic by the inhalation, 

oral, and intravenous routes.152 The primary acute effect of exposure to acetaldehyde vapors is 

irritation of the eyes, skin, and respiratory tract.153 The agency is currently conducting a 

reassessment of the health hazards from inhalation exposure to acetaldehyde. 

Acrolein: Acrolein is intensely irritating to humans when inhaled, with acute exposure 

resulting in upper respiratory tract irritation and congestion. EPA determined in 2003 using the 

1999 draft cancer guidelines that the human carcinogenic potential of acrolein could not be 

determined because the available data was inadequate. No information was available on the 

carcinogenic effects of acrolein in humans, and the animal data provided inadequate evidence of 

carcinogenicity.154 

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. One of these compounds, naphthalene, is discussed separately below. Polycyclic 

aromatic hydrocarbons (PAH) are a class 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 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.155156 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 and evaporative emissions from mobile sources. 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.157 The draft reassessment recently completed 

external peer review.158 California EPA has also released a new risk assessment for naphthalene, 

and the IARC has reevaluated naphthalene and re-classified it as Group 2B: possibly 

carcinogenic to humans.159 Naphthalene also causes a number of chronic non-cancer effects in 

animals, including abnormal cell changes and growth in respiratory and nasal tissues.160 

In addition to reducing VOC, NOx, CO and PM2.5 emissions from Small SI engines and 

equipment and Marine SI engines and vessels the standards being proposed today would also 

reduce air toxics emitted from these engines, vessels and equipment thereby helping to mitigate 

some of the adverse health effects associated with operation of these engines, vessels and 

equipment. 

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Draft Regulatory Impact Analysis 

2.4 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. 

2.4.1 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) regarding the health effects associated with CO exposure.161 

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.162, 

163 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.164 The subsequent hypoxia in brain tissue then produces behavioral 

effects, including decrements in continuous performance and reaction time.165 

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.166 Persons 

with heart disease are especially sensitive to carbon monoxide poisoning and may experience 

chest pain if they breathe the gas while exercising.167 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.168 

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 

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Air Quality, Health, and Welfare Concerns 

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.169 

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 2.5. 

2.4.2 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 spark-ignition 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. Spark-ignition 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.19 

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 October 26, 2006, there are approximately 15 million 

people living in 6 areas (which include 10 counties) that are designated as nonattainment for CO, 

see Table 2.4-1. The emission reductions proposed in this action would help areas to attain and 

maintain the CO NAAQS. 

Table 2.4-1: Classified Carbon Monoxide Nonattainment Areas as of October 2006a 

Area Classification Population (1000s) 

Las Vegas, NV serious 479 

Los Angeles South Coast Air Basin serious 14,594 

El Paso, TX moderate <= 12.7 ppm 62 

Missoula, MT moderate <= 12.7 ppm 52 

Reno, NV moderate <= 12.7 ppm 179 

Total 15,365 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, 

19 The full details involved in calculating a CO design value are given in 40 CFR Part 50.8. 

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Draft Regulatory Impact Analysis 

areas like Birmingham, AL and Calexico, CA have not been designated as nonattainment 

although monitors in these areas have recorded multiple exceedances since 1995.170 

There are also over 54 million people living in CO maintenance areas, see Table 2.4-2.20 

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 2.4-2: Carbon Monoxide Maintenance Areas as of October 2006 

Number of Areas Number of Counties Population (1000s) 

Serious 5 11 5,902 

Moderate > 12.7ppm 4 19 17,576 

Moderate <= 12.7ppm 30 61 23,319 

Unclassified 33 41 7,544 

Total 72 132 54,341 

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 inversions. Areas like Alaska are 

prone to winter inversions due to their topographic and meteorologic 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.171 

The reductions in CO emissions from this proposed rule could 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 would 

help states in their strategy to attain the CO NAAQS. Maintenance of the CO NAAQS is also 

challenging and many areas would be able to use the emissions reductions from this proposed 

rule to assist in maintaining the CO NAAQS into the future. 

2.5 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 CO 

and PM. As mentioned in Section II.B.4 of the preamble for this proposal, elevated exposures to 

20The CO nonattainment and maintenance areas are listed in a Memo to the Docket titled “Nonattainment 

Areas and Mandatory Class I Federal Areas” and contained in Docket EPA-HQ-OAR-2004-0008. 

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Air Quality, Health, and Welfare Concerns 

CO from Marine SI engines and vessels have been well documented. As mentioned in Sections 

II.B.2 and II.B.4 of the preamble, elevated exposures to CO and PM can occur as a result of 

operating Small SI engines and equipment. The standards being proposed in this action can help 

reduce acute exposures to CO and PM from Marine SI engines and vessels and Small SI engines 

and equipment. 

2.5.1 Exposure to CO from Marine SI Engines and Vessels 

In recent years, a substantial number of carbon monoxide (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.172 Between 

1984 and 2004, 113 CO-related deaths and 458 non-fatal 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.173 

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).174 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 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. 

2.5.2 Exposure to CO and PM from Small SI Engines and Equipment 

A large segment of the population uses small, gasoline-powered spark-ignition (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.175,176 Studies investigating air pollutant exposures during 

small engine use did report elevated personal exposure measurements related to lawn and garden 

2-43 
Draft Regulatory Impact Analysis 

equipment use.177,178 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, short-term 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 μg/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 result in exposures to certain pollutants at levels of concern 

for adverse health effects. The potential for elevated exposure to CO and PM2.5 for operators of 

Small SI engines and equipment would be reduced by this proposed rule. 

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Air Quality, Health, and Welfare Concerns 

Chapter 2 References 

1. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

2. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

3. U.S. EPA (2007) Review of National Ambient Air Quality Standards for Ozone, Assessment of Scientific and 

Technical Information, OAQPS Staff Paper, EPA-452/R-07-003. This document is available in Docket 

EPA-HQ-OAR-2004-0008. 

4.Bates, D.V.; Baker-Anderson, M.; Sizto, R. (1990) Asthma attack periodicity: a study of hospital emergency visits 

in Vancouver. Environ. Res. 51: 51-70. 

5.Thurston, G.D.; Ito, K.; Kinney, P.L.; Lippmann, M. (1992) A multi-year study of air pollution and respiratory 

hospital admissions in three New York State metropolitan areas: results for 1988 and 1989 summers. J. Exposure 

Anal. Environ. Epidemiol. 2:429-450. 

6.Thurston, G.D.; Ito, K.; Hayes, C.G.; Bates, D.V.; Lippmann, M. (1994) Respiratory hospital admissions and 

summertime haze air pollution in Toronto, Ontario: consideration of the role of acid aerosols. Environ. Res. 65: 271­

290. 

7.Lipfert, F.W.; Hammerstrom, T. (1992) Temporal patterns in air pollution and hospital admissions. Environ. Res. 

59: 374-399. 

8.Burnett, R.T.; Dales, R.E.; Raizenne, M.E.; Krewski, D.; Summers, P.W.; Roberts, G.R.; Raad-Young, M.; 

Dann,T.; Brook, J. (1994) Effects of low ambient levels of ozone and sulfates on the frequency of respiratory 

admissions to Ontario hospitals. Environ. Res. 65: 172-194. 

9. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

10. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

11.Devlin, R. B.; McDonnell, W. F.; Mann, R.; Becker, S.; House, D. E.; Schreinemachers, D.; Koren, H. S. (1991) 

Exposure of humans to ambient levels of ozone for 6.6 hours causes cellullar and biochemical changes in the lung. 

Am. J. Respir. Cell Mol. Biol. 4: 72-81. 

12.Koren, H. S.; Devlin, R. B.; Becker, S.; Perez, R.; McDonnell, W. F. (1991) Time-dependent changes of markers 

associated with inflammation in the lungs of humans exposed to ambient levels of ozone. Toxicol. Pathol. 19: 406­

411. 

13.Koren, H. S.; Devlin, R. B.; Graham, D. E.; Mann, R.; McGee, M. P.; Horstman, D. H.; Kozumbo, W. J.; Becker, 

S.; House, D. E.; McDonnell, W. F.; Bromberg, P. A. (1989a) Ozone-induced inflammation in the lower airways of 

human subjects. Am. Rev. Respir. Dis. 139: 407-415. 

2-45 
Draft Regulatory Impact Analysis 

14.Schelegle, E.S.; Siefkin, A.D.; McDonald, R.J. (1991) Time course of ozone-induced neutrophilia in normal 

humans. Am. Rev. Respir. Dis. 143:1353-1358. 

15.U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

16.Hodgkin, J.E.; Abbey, D.E.; Euler, G.L.; Magie, A.R. (1984) COPD prevalence in nonsmokers in high and low 

photochemical air pollution areas. Chest 86: 830-838. 

17.Euler, G.L.; Abbey, D.E.; Hodgkin, J.E.; Magie, A.R. (1988) Chronic obstructive pulmonary disease symptom 

effects of long-term cumulative exposure to ambient levels of total oxidants and nitrogen dioxide in California 

Seventh-day Adventist residents. Arch. Environ. Health 43: 279-285. 

18.Abbey, D.E.; Petersen, F.; Mills, P.K.; Beeson, W.L. (1993) Long-term ambient concentrations of total 

suspended particulates, ozone, and sulfur dioxide and respiratory symptoms in a nonsmoking population. Arch. 

Environ. Health 48: 33-46. 

19.U.S. EPA. (1996). Review of National Ambient Air Quality Standards for Ozone, Assessment of Scientific and 

Technical Information, OAQPS Staff Paper, EPA452-R-96-007. Docket No. A-99-06. Document Identification IIA-22. 

20.U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

21. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, 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. Avol, E. L.; Trim, S. C.; Little, D. E.; Spier, C. E.; Smith, M. N.; Peng, R.-C.; Linn, W. S.; Hackney, J. D.; 

Gross, K. B.; D'Arcy, J. B.; Gibbons, D.; Higgins, I. T. T. (1990) Ozone exposure and lung function in children 

attending a southern California summer camp. Presented at: 83rd annual meeting and exhibition of the Air & Waste 

Management Association; June; Pittsburgh, PA. Pittsburgh, PA: Air & Waste Management Association; paper no. 

90-150.3. 

23. Higgins, I. T. T.; D'Arcy, J. B.; Gibbons, D. I.; Avol, E. L.; Gross, K. B. (1990) Effect of exposures to ambient 

ozone on ventilatory lung function in children. Am. Rev. Respir. Dis. 141: 1136-1146. 

24. Raizenne, M. E.; Burnett, R. T.; Stern, B.; Franklin, C. A.; Spengler, J. D. (1989) Acute lung function responses 

to ambient acid aerosol exposures in children. Environ. Health Perspect. 79: 179-185. 

25. Raizenne, M.; Stern, B.; Burnett, R.; Spengler, J. (1987) Acute respiratory function and transported air 

pollutants: observational studies. Presented at: 80th annual meeting of the Air Pollution Control Association; June; 

New York, NY. Pittsburgh, PA: Air Pollution Control Association; paper no. 87-32.6. 

26. Spektor, D. M.; Lippmann, M. (1991) Health effects of ambient ozone on healthy children at a summer camp. 

In: Berglund, R. L.; Lawson, D. R.; McKee, D. J., eds. Tropospheric ozone and the environment: papers from an 

international conference; March 1990; Los Angeles, CA. Pittsburgh, PA: Air & Waste Management Association; pp. 

83-89. (A&WMA transaction series no. TR-19). 

27. Spektor, D. M.; Thurston, G. D.; Mao, J.; He, D.; Hayes, C.; Lippmann, M. (1991) Effects of single- and 

multiday ozone exposures on respiratory function in active normal children. Environ. Res. 55: 107-122. 

2-46 
Air Quality, Health, and Welfare Concerns 

28.Spektor, D. M.; Lippman, M.; Lioy, P. J.; Thurston, G. D.;s Citak, K.; James, D. J.; Bock, N.; Speizer, F. E.; 

Hayes, C. (1988a) Effects of ambient ozone on respiratory function in active, normal children. Am. Rev. Respir. Dis. 

137: 313-320. 

29.U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

30.Hazucha, M. J.; Folinsbee, L. J.; Seal, E., Jr. (1992) Effects of steady-state and variable ozone concentration 

profiles on pulmonary function. Am. Rev. Respir. Dis. 146: 1487-1493. 

31.Horstman, D.H.; Ball, B.A.; Folinsbee, L.J.; Brown, J.; Gerrity, T. (1995) Comparison of pulmonary responses of 

asthmatic and nonasthmatic subjects performing light exercise while exposed to a low level of ozone. Toxicol. Ind. 

Health. 

32.Horstman, D.H.; Folinsbee, L.J.; Ives, P.J.; Abdul-Salaam, S.; McDonnell, W.F. (1990) Ozone concentration and 

pulmonary response relationships for 6.6-hour exposures with five hours of moderate exercise to 0.08, 0.10, and 0.12 

ppm. Am. Rev. Respir. Dis. 142: 1158-1163. 

33. U.S. EPA (2005). Guidance on the Use of Models and Other Analyses in Attainment Demonstrations for the 8­

Hour Ozone NAAQS, Office of Air Quality Planning and Standards, Research Triangle Park, NC. EPA document # 

EPA-454/R-05-002. This document is contained in Docket Identification EPA-HQ-OAR-2004-0008-0464. 

34. U.S. Environmental Protection Agency, 1999. The Benefits and Costs of the Clean Air Act, 1990-2010. 

Prepared for U.S. Congress by U.S. EPA, Office of Air and Radiation, Office of Policy Analysis and Review, 

Washington, DC, November; EPA report no. EPA410-R-99-001. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0485. 

35. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

36. Winner, W.E., and C.J. Atkinson. 1986. Absorption of air pollution by plants, and consequences for growth. 

Trends in Ecology and Evolution 1:15-18. 

37. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

38. Tingey, D.T., and Taylor, G.E. 1982. Variation in plant response to ozone: a conceptual model of physiological 

events. In: Effects of Gaseous Air Pollution in Agriculture and Horticulture (Unsworth, M.H., Omrod, D.P., eds.) 

London, UK: Butterworth Scientific, pp. 113-138. 

39. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

40. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

41. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

2-47 
Draft Regulatory Impact Analysis 

42. Ollinger, S.V., J.D. Aber and P.B. Reich. 1997. Simulating ozone effects on forest productivity: interactions 

between leaf canopy and stand level processes. Ecological Applications 7:1237-1251. 

43. Winner, W.E., 1994. Mechanistic analysis of plant responses to air pollution. Ecological Applications, 

4(4):651-661. 

44. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

45. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

46. Fox, S., and R. A. Mickler, eds.. 1996. Impact of Air Pollutants on Southern Pine Forests. Springer-Verlag, NY, 

Ecol. Studies, Vol. 118, 513 pp. 

47. National Acid Precipitation Assessment Program (NAPAP), 1991. National Acid Precipitation Assessment 

Program. 1990 Integrated Assessment Report. National Acid Precipitation Program. Office of the Director, 

Washington DC. This document is contained in Docket Identification EPA-HQ-OAR-2004-0008-0489. 

48. De Steiguer, J., J. Pye, C. Love. 1990. Air pollution Damage to U.S. forests. Journal of Forestry, Vol 88(8) pp. 

17-22. 

49. Pye, J.M. Impact of ozone on the growth and yield of trees: A review. Journal of Environmental Quality 17 

pp.347-360., 1988. 

50. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

51. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

52. McBride, J.R., P.R. Miller, and R.D. Laven. 1985. Effects of oxidant air pollutants on forest succession in the 

mixed conifer forest type of southern California. In: Air Pollutants Effects On Forest Ecosystems, Symposium 

Proceedings, St. P, 1985, p. 157-167. 

53. Miller, P.R., O.C. Taylor, R.G. Wilhour. 1982. Oxidant air pollution effects on a western coniferous forest 

ecosystem. Corvallis, OR: U.S. Environmental Protection Agency, Environmental Research Laboratory (EPA600-D82-276). 

54. U.S. EPA. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document is contained in Docket 

Identification EPA-HQ-OAR-2004-0008-0455 to 0457. 

55. Kopp, R. J.; Vaughn, W. J.; Hazilla, M.; Carson, R. 1985. Implications of environmental policy for U.S. 

agriculture: the case of ambient ozone standards. J. Environ. Manage. 20:321-331. 

56. Adams, R. M.; Hamilton, S. A.; McCarl, B. A. 1986. The benefits of pollution control: the case of ozone and 

U.S. agriculture. Am. J. Agric. Econ. 34: 3-19. 

2-48 
Air Quality, Health, and Welfare Concerns 

57. Adams, R. M.; Glyer, J. D.; Johnson, S. L.; McCarl, B. A. 1989. A reassessment of the economic effects of 

ozone on U.S. agriculture. JAPCA 39:960-968. 

58. Abt Associates, Inc. 1995. Urban ornamental plants: sensitivity to ozone and potential economic losses. U.S. 

EPA, Office of Air Quality Planning and Standards, Research Triangle Park. Under contract to RADIAN 

Corporation, contract no. 68-D3-0033, WA no. 6. pp. 9-10. 

59. U.S. EPA (2004) Air Quality Criteria for Particulate Matter. Document Nos. EPA/600/P-99/002aF and 

EPA/600/P-99/002bF. This document is available in Docket EPA-HQ-OAR-2004-0008-0042 and EPA-HQ-OAR2004-0008-0043. 

60. 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-2004-0008-0454. 

61.U.S. EPA 2006. Provisional Assessment of Recent Studies on Health Effects of Particulate Matter Exposure. 

EPA/600/R-06/063. This document is available in Docket EPA-HQ-OAR-2004-0008-0461. 

62. Laden F; Neas LM; Dockery DW; et al. (2000). Association of fine particulate matter from different sources 

with daily mortality in six U.S. cities. Environ Health Perspectives 108(10):941-947. 

63. Schwartz J; Laden F; Zanobetti A. (2002). The concentration-response relation between PM(2.5) and daily 

deaths. Environ Health Perspect 110(10): 1025-1029. 

64. Janssen NA; Schwartz J; Zanobetti A.; et al. (2002). Air conditioning and source-specific particles as modifiers 

of the effect of PM10 on hospital admissions for heart and lung disease. Environ Health Perspect 110(1):43-49. 

65. Dockery, DW; Pope, CA, III; Xu, X; et al. (1993). An association between air pollution and mortality in six U.S. 

cities. N Engl J Med 329:1753-1759. 

66. Pope, CA, III; Burnett, RT; Thun, MJ; Calle, EE; et al. (2002) Lung cancer, cardiopulmonary mortality, and 

long-term exposure to fine particulate air pollution. J Am Med Assoc 287: 1132-1141. 

67. Krewski, D; Burnett, RT; Goldberg, M S; et al. (2000) Reanalysis of the Harvard Six Cities study and the 

American Cancer Society study of particulate air pollution and mortality. A special report of the institute's Particle 

Epidemiology Reanalysis Project. Cambridge, MA: Health Effects Institute. 

68.Jerrett, M; Burnett, RT; Ma, R; et al. 2005. "Spatial Analysis of Air Pollution and Mortality in Los Angeles." 

Epidemiology. 16(6):727-736. 

69. Künzli, N.; Jerrett, M.; Mack, W.J.; et al.(2004) Ambient air pollution and atherosclerosis in 

Los Angeles. Environ Health Perspect doi:10.1289/ehp.7523 [Available at http://dx.doi.org/]. 

70.Riediker, M.; Cascio, W.E.; Griggs, T.R.; et al. 2004. "Particulate matter exposure in cars is associated with 

cardiovascular effects in healthy young men." Am J Respir Crit Care Med 169: 934-940. 

71.Van Vliet, P.; Knape, M.; de Hartog, J.; Janssen, N.; Harssema, H.; Brunekreef, B. (1997). Motor vehicle 

exhaust and chronic respiratory symptoms in children living near freeways. Env. Research 74: 122-132. 

72.Brunekreef, B., Janssen, N.A.H.; de Hartog, J.; Harssema, H.; Knape, M.; van Vliet, P. (1997). Air pollution 

from truck traffic and lung function in children living near roadways. Epidemiology 8:298-303. 

2-49 
Draft Regulatory Impact Analysis 

73.Kim, J.J.; Smorodinsky, S.; Lipsett, M.; Singer, B.C.; Hodgson, A.T.; Ostro, B (2004). Traffic-related air 

pollution near busy roads: The East Bay children's respiratory health study. Am. J. Respir. Crit. Care Med. 170: 

520-526. 

74.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 document is available in Docket EPA-HQ-OAR-2004-0008-0488. This book can be viewed 

on the National Academy Press Website at http://www.nap.edu/books/0309048443/html/ 

75.See discussion in U.S. EPA , National Ambient Air Quality Standards for Particulate Matter; Proposed Rule; 

January 17, 2006, Vol71 p 2676. This document is available in Docket EPA-HQ-OAR-2004-0008-0466. This 

information is available electronically at http://epa.gov/fedrgstr/EPA-AIR/2006/January/Day-17/a177.pdf 

76. U.S. EPA (2004) Air Quality Criteria for Particulate Matter. Document Nos. EPA/600/P-99/002aF and 

EPA/600/P-99/002bF. This document is available in Docket EPA-HQ-OAR-2004-0008-0042 and EPA-HQ-OAR2004-0008-0043. 

77. 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-2004-0008-0454. 

78. U.S. EPA (2005). Technical Support Document for the Final Clean Air Interstate Rule - Air Quality Modeling. 

This document is available in Docket EPA-HQ-OAR-2004-0008-0484. 

79.U.S. EPA. 2006. Regulatory Impact Analysis for the final PM NAAQS. This document is available in Docket 

EPA-HQ-OAR-2004-0008. 

80. 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-2004-0008-0454. 

81. 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. This document is available in Docket EPA-HQ-OAR-2004-0008-0483. 

82.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. 

83. National Park Service. Air Quality in the National Parks, Second edition. NPS, Air Resources Division. D 

2266. September 2002. This document is available in Docket EPA-HQ-OAR-2004-0008-0481. 

84.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. 

85. 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. This document is available in Docket EPA-HQ-OAR-2004-0008-0483. 

86. U.S. EPA (2005). Technical Support Document for the Final Clean Air Interstate Rule - Air Quality Modeling. 

This document is available in Docket EPA-HQ-OAR-2004-0008-0484. 

87. U.S. EPA (2003) Guidance for Tracking Progress Under the Regional Haze Rule. EPA-454/B-03-004. This 

document is available in Docket EPA-HQ-OAR-2004-0008-0487. 

88.U.S. EPA (2000) Deposition of Air Pollutants to the Great Waters: Third Report to Congress. Office of Air 

Quality Planning and Standards. EPA-453/R-00-0005. 

2-50 
Air Quality, Health, and Welfare Concerns 

89.U.S. EPA (2004) National Coastal Condition Report II. Office of Research and Development/ Office of Water. 

EPA-620/R-03/002. 

90.Gao, Y., E.D. Nelson, M.P. Field, et al. 2002. Characterization of atmospheric trace elements on PM2.5 

particulate matter over the New York-New Jersey harbor estuary. Atmos. Environ. 36: 1077-1086. 

91.Kim, G., N. Hussain, J.R. Scudlark, and T.M. Church. 2000. Factors influencing the atmospheric depositional 

fluxes of stable Pb, 210Pb, and 7Be into Chesapeake Bay. J. Atmos. Chem. 36: 65-79. 

92.Lu, R., R.P. Turco, K. Stolzenbach, et al. 2003. Dry deposition of airborne trace metals on the Los Angeles Basin 

and adjacent coastal waters. J. Geophys. Res. 108(D2, 4074): AAC 11-1 to 11-24. 

93.Marvin, C.H., M.N. Charlton, E.J. Reiner, et al. 2002. Surficial sediment contamination in Lakes Erie and 

Ontario: A comparative analysis. J. Great Lakes Res. 28(3): 437-450. 

94. Much of the information in this subsection was excerpted from the EPA document, Human Health Benefits from 

Sulfate Reduction, written under Title IV of the 1990 Clean Air Act Amendments, U.S. EPA, Office of Air and 

Radiation, Acid Rain Division, Washington, DC 20460, November 1995. 

95.Acid Rain: Emissions Trends and Effects in the Eastern United States, U.S. General Accounting Office, March, 

2000 (GOA/RCED-00-47). 

96. Acid Deposition Standard Feasibility Study: Report to Congress, EPA430-R-95-001a, October, 1995. 

97.Deposition of Air Pollutants to the Great Waters, Third Report to Congress, June 2000, EPA-453/R-00-005. 

This document can be found in Docket No. OAR-2002-0030, Document No. OAR-2002-0030-0025. It is also 

available at www.epa.gov/oar/oaqps/gr8water/3rdrpt/obtain.html. 

98. 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. 

99. Deposition of Air Pollutants to the Great Waters, Third Report to Congress, June, 2000. 

100. Valigura, Richard, et al., Airsheds and Watersheds II: A Shared Resources Workshop, Air Subcommittee of the 

Chesapeake Bay Program, March, 1997. 

101. The Impact of Atmospheric Nitrogen Deposition on Long Island Sound, The Long Island Sound Study, 

September, 1997. 

102. Dennis, Robin L., Using the Regional Acid Deposition Model to Determine the Nitrogen Deposition Airshed of 

the Chesapeake Bay Watershed, SETAC Technical Publications Series, 1997. 

103. Dennis, Robin L., Using the Regional Acid Deposition Model to Determine the Nitrogen Deposition Airshed of 

the Chesapeake Bay Watershed, SETAC Technical Publications Series, 1997. 

104.Wedin, D.A. and D. Tilman. 1996. Influence of nitrogen loading and species composition on the carbon balance 

of grasslands. Science 274:1720-1723. 

105.Smith, W.H. 1991. Air pollution and forest damage." Chemical Engineering News, 69(45): 30-43. 

106.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. 

2-51 
Draft Regulatory Impact Analysis 

107.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. 

108.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. 

109.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") 

110.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. 

111.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. 

112.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. 

113.Rice, K.C. 1999. Trace element concentrations in streambed sediment across the conterminous United States. 

Environmental Science & Technology, 33: 2499-2504. 

114.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. 

115.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. This 

document is available in Docket EPA-HQ-OAR-2004-0008. 

116.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. This 

document is available in Docket EPA-HQ-OAR-2004-0008. 

117.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. 

118.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. 

119.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. 

120.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. 

121.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. 

122.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. 

2-52 
Air Quality, Health, and Welfare Concerns 

123.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. 

124.Van Metre, P.C.; Mahler, B.J.; and Furlong, E.T. 2000. Urban sprawl leaves its PAH signature." Environmental 

Science & Technology, 34: 4064-4070. 

125.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. 

126.Tuhackova, J., Cajthaml, T.; Novak, K.; et al. 2001. Hydrocarbon deposition and soil microflora as affected by 

highway traffic. Environmental Pollution, 113: 255-262. 

127.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-2004-0008-0454. 

128.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 

129.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. 

130.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 colony-stimulating factor 

in vitro, Proc. Natl. Acad. Sci. 89:3691-3695. 

131.Aksoy, M. (1989). Hematotoxicity and carcinogenicity of benzene. Environ. Health Perspect. 82: 193-197. 

132.Goldstein, B.D. (1988). Benzene toxicity. Occupational medicine. State of the Art Reviews. 3: 541-554. 

133.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. 

134.EPA 2005 “Full IRIS Summary for Benzene (CASRN 71-43-2)” Environmental Protection Agency, Integrated 

Risk Information System (IRIS), Office of Health and Environmental Assessment, Environmental Criteria and 

Assessment Office, Cincinnati, OH http://www.epa.gov/iris/subst/0276.htm. 

135.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. 

136.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. 

137.Lan, Qing, Zhang, L., Li, G., Vermeulen, R., et al. (2004). Hematotoxically in Workers Exposed to Low Levels 

of Benzene. Science 306: 1774-1776. 

138.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. 

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Draft Regulatory Impact Analysis 

139.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. 

140.U.S. EPA (1998). A Science Advisory Board Report: Review of the Health Risk Assessment of 1,3-Butadiene. 

EPA-SAB-EHC-98. 

141.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. 

142.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. 

143.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. 

144.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. 

145.Pinkerton, L. E. 2004. Mortality among a cohort of garment workers exposed to formaldehyde: an update. 

Occup. Environ. Med. 61: 193-200. 

146.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. 

147.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. 

148.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. 

149.Health Canada (2001) Priority Substances List Assessment Report. Formaldehyde. Environment Canada, Health 

Canada, February 2001. The document may be accessed at 

http://www.hc-sc.gc.ca/ewh-semt/pubs/contaminants/psl2-lsp2/formaldehyde/index_e.html . 

150.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. 

151.U.S. EPA (2004) National Emission Standards for Hazardous Air Pollutants for Plywood and Composite Wood 

Products Manufacture: Final Rule. (69 FR 45943, 7/30/04) 

152.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. 

153.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. 

154.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 

155.Perera, F. P.; Rauh, V.; Tsai, W. Y. et al. (2003). Effects of transplacental exposure to environmental pollutants 

on birth outcomes in a multiethnic population. Environ. Health Perspect. 111(2): 201-205. 

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Air Quality, Health, and Welfare Concerns 

156. 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. 

157.U. S. EPA. (2004). External Review Draft, IRIS Reassessment of the Inhalation Carcinogenicity of 

Naphthalene. http://www.epa.gov/iris 

158.Oak Ridge Institute for Science and Education. (2004). External Peer Review for the IRIS Reassessment of the 

Inhalation Carcinogenicity of Naphthalene. August 2004. 

http://cfpub2.epa.gov/ncea/cfm/recordisplay.cfm?deid=86019 

159.International Agency for Research on Cancer (IARC). (2002). Monographs on the Evaluation of the 

Carcinogenic Risk of Chemicals for Humans. Vol. 82. Lyon, France. 

160.U. S. EPA. (1998). Integrated Risk Information System File of Naphthalene. This information is available 

electronically at http://www.epa/gov/iris 

161. 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. 

162. 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. 

163. Coburn, R.F. (1979) Mechanisms of carbon monoxide toxicity. Prev. Med. 8:310-322. 

164. 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. 

165. Benignus, V.A. (1994) Behavioral effects of carbon monoxide: meta analyses and extrapolations. J. Appl. 

Physiol. 76:1310-1316. 

166. 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. 

167. 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. 

168. 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. 

169. 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. 

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170. 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. 

171. 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. 

172.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 

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. 

173.U.S. Department of Interior. (2004) Carbon monoxide dangers from generators and propulsion engines. Onboard 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. 

174.Letter dated April 5, 2001 to Mr. John Stenseth, Fun Country Marine Industries, Inc., from Ronald M. Hall, 

NIOSH. 

175. Gabele, P. (1997) Exhaust emissions from four-stroke lawn mower engines. Air Waste Manage Assoc. 47: 

945-952. 

176. Priest, M.W.; Williams, D.J.; and Bridgman, H.A. (2000) Emissions from in-use lawn-mowers in Australia. 

Atmos Environ. 34:657-664. 

177. 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. 

178. 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. 

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Emission Inventory 

CHAPTER 3: Emission Inventory 

This chapter presents our analysis of the emission impact of the proposed rule for spark 

ignition (SI) small nonroad engines (#25 horsepower (hp) or #19 kilowatts (kW) used in landbased 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 III-V), 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 proposed 

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 proposed 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 more refined final baseline and control scenarios reflected in the actual 

proposal. 

In Sections 3.2, 3.4 and 3.5, the estimates of baseline, controlled, and emission reduction 

inventories, respectively, for criteria pollutants from small nonroad and Marine SI engines are 

reported for the 50-state geographic area (including the District of Columbia). These inventories 

reflect the emissions from the engines subject to the proposed Phase 3 standards. 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 is prevented from regulating nonroad engines with less than 

175 horsepower that are used in farm and construction equipment. Therefore, those engines are 

subject to federal regulation and included in our 50-state inventories. By contrast, we do not 

include the emissions from California marine engines in our inventories. California has also 

been granted a waiver under the Clean Air Act to regulate exhaust emissions form all Marine SI 

engines and evaporative emissions from outboard and personal watercraft SI engines. That State 

also has indicted its intent to adopt the proposed Phase III standards for evaporative emissions 

from stern drive engines. Therefore, are excluded in our 50-state inventories. 

In Section 3.3, 50-state inventories are used to compare the nationwide importance of 

these sources to other source categories, i.e., stationary, area, and other mobile sources. Finally, 

3-1 
Draft Regulatory Impact Analysis 

Section 3.6 presents inventories for 37 of the most eastern states in the nation that were included 

in the air quality modeling domain for this proposal. Unlike the 50-state inventories in the other 

sections, these inventories include all small nonroad SI and marine engines. The 37-state 

control scenarios assume federal standards apply only to those engines that are not subject to 

California emission regulations as described earlier. 

Inventories are generally presented for the following pollutants: exhaust and evaporative 

total hydrocarbons (THC), oxides of nitrogen (NOx), particulate matter (PM2.5 and PM10), and 

carbon monoxide (CO). The PM inventories include directly emitted PM only, although 

secondary sulfates are taken into account in the air quality modeling as noted below. The 

proposed requirements would also 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). 

The hydrocarbon inventories in Sections 3.3 and 3.5 for the nationwide comparison and 

air quality modeling, respectively, are presented as volatile organic compounds (VOC) rather 

than THC. This is a broader class of hydrocarbon compounds that is important for air quality 

modeling purposes. The additional compounds that comprise VOC are reactive oxygenated 

species represented by aldehydes (RCHO) and alcohols (RCOH), and less reactive species 

represented by methane (CH4) and ethane (CH3CH3). 

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 proposal 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 baseline emission inventories were modeled for the small 

nonroad and Marine SI engines affected by the proposed rule. Section 3.1 focuses on exhaust 

and evaporative hydrocarbons, and exhaust NOx, PM, and CO. 

The primary emission inventories associated with the small nonroad and Marine SI 

engine proposed rule, which are summarized in Sections 3.2 through 3.5, 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 proposal.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 NONROAD2005c. A 

3-2 
Emission Inventory 

copy of the model and most of the accompanying documentation are available in the docket.2,3,4 

The documentation for evaporative emission changes is in Chapter 5. The modifications we 

made to NONROAD2005a to reflect the baseline and control scenarios related to the proposed 

rule are fully described in Sections 3.2 and 3.4, respectively. 

The nonroad model estimates emission inventories of important air emissions 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 proposal, 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 future or past emissions between 1970 and 2050. 

The chemical species NOx, PM, and CO are exhaust emissions, i.e., pollutants emitted 

directly as exhaust from combustion of gasoline fuel 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 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. 

3-3 
Draft Regulatory Impact Analysis 

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 

gasoline or gasoline blends, i.e., ethanol and gasoline. 

The control scenario analyzed in Section 3.4 reflects the proposed standards for exhaust 

hydrocarbons, CO, and NOx from small nonhandheld nonroad and Marine SI engines.1 New 

standards to control evaporative emissions from hose permeation and tank permeation from these 

engine classes and handheld equipment are also included. Further, the proposal also would 

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 proposed 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 proposed standards. For small nonroad SI equipment, California’s Air 

Resources Board (ARB) has promulgated standards that are roughly equivalent in stringency 

overall to our proposed national 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 proposal 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. 

For Marine SI engines, ARB also has its own exhaust emission standards that are 

roughly equivalent overall to our proposed national standards. In addition, ARB has stated its 

intend to develop evaporative emissions standards for boats in California. Therefore, exhaust 

and evaporative inventory estimates contained in this proposal are modeled for 49 states 

(excluding California) for Marine SI engines. 

3.2.1 Baseline Exhaust and Evaporative Emissions Estimates for THC, 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 

1

 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 2005. 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 NONROAD2005c. The modifications to the base model are described below. 

3.2.1.1 Changes from NONROAD2005a to NONROAD2005c 

As already mentioned, a number of improvements to the most publically available 

nonroad emissions inventory model were made to develop the NONROAD2005c, which is used 

in this proposed rulemaking. These revisions were based on recent testing programs, other 

information, and model enhancements. The changes are summarized below for Small SI 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 proposal are summarized below: 

1.	 Revised fuel tank and hose permeation emission factors; 

2.	 Explicitly separated fuel tank diffusion losses to diurnal emission estimates; 

3.	 Updated 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; and 

5.	 Added the ability to specifically model the effects of ethanol blends on fuel tank 

and hose permeation. 

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 proposal 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 fuel tank 

and hose permeation. 

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 NONROAD2005a inventory 

model to reflect new information and our better understanding of the in-use emissions of these 

3-5 
Draft Regulatory Impact Analysis 

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.5 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 

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 proposal, 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 

3-6 
Emission Inventory 

Table 3.2-1: Phase 2 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 10.30 1.753 2.57 0.000 386.53 0.070 0.35 1.753

 Class I - OHV 8.73 1.753 3.28 0.000 392.93 0.070 0.05 1.753

 Class II 5.58 1.095 3.71 0.000 472.80 0.080 0.08 1.095 

* The nonroad model calculates PM2.5 as 92 percent of PM10. 

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. 

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 

3-7 
Draft Regulatory Impact Analysis 

The NONROAD2005a model included a number of recent updates to the emission rates 

and technology mix of Marine SI engines.6

 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.7

 However, NONROAD2005a does 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 recently commented that approximately 1,500 high-performance 

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 

3.2.1.3 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.8 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. 

3.2.1.3.1 Fuel Ethanol Content 

Currently, about 30 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 

3-8 
Emission Inventory 

significance of the use of ethanol in fuel, for the inventory calculations, is that ethanol in fuel can 

affect the evaporative emissions from nonroad equipment. 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 reach 9.6 billion 

gallons per year by then. Based on these figures and projected gasoline sales from the Energy 

Information Administration,10,11,12 we estimate that about two-thirds of gasoline sold in 2012 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. 

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 

139.6 

139.9 

141.3 

143.0 

145.4 

148.1 

150.9 

153.3 

155.6 

1.6 

1.8 

2.1 

2.8 

3.4 

3.8 

4.1 

5.2 

6.0 

6.9 

7.9 

8.8 

9.6 

13.5% 

14.5% 

17.0% 

22.2% 

26.3% 

29.7% 

31.6% 

39.2% 

44.9% 

50.4% 

56.4% 

62.2% 

67.1% 

* ethanol fraction projected to be constant after last year of Energy Policy Act phase-in (2012) 

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 SI applications vary greatly in construction depending on the 

3-9 
Draft Regulatory Impact Analysis 

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.13 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 SI 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. 

Chapter 5 also presents permeation data on nine samples of fuel lines used in handheld 

equipment tested using E10 fuel. The permeation rates for these samples ranged from 165 to 455 

g/m2/day at 23/C with an average of 255 g/m2/day. All of the hose samples, except one were 

made of NBR rubber, with the exception being a NBR/PVC blend. 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).14,15 

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 proposed 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 

3-10 
Emission Inventory 

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 

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 proposed 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 proposed 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.16 Recently, we 

received comment from a boatbuilder using outboard motors that the hose lengths in our 

calculations were too short.17 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. 

3-11 
Draft Regulatory Impact Analysis 

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 

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 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. 

3-12 
Emission Inventory 

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.18 

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 
Draft Regulatory Impact Analysis 

Hose and Tank Permeation for 0 - 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
 

meter

2

 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
 

Note that all ethanol blends currently modeled with NONROAD or NMIM are less than 

or equal to E10, so no parts of this curve above E10 are used. Also note that 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, 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 
Draft 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 NOx PM2.5 PM10 CO 

2001 1,099,402 101,928 23,163 25,177 16,108,103 

2002 1,074,137 101,261 23,382 25,416 15,560,774 

2003 1,039,522 99,649 23,480 25,522 14,941,296 

2004 978,760 97,929 23,483 25,525 14,382,759 

2005 905,814 95,779 23,417 25,453 13,784,367 

2006 849,619 94,550 23,498 25,541 13,369,719 

2007 794,827 92,988 23,804 25,874 12,919,586 

2008 748,034 90,638 24,335 26,451 12,285,206 

2009 715,943 89,272 24,882 27,045 11,775,265 

2010 700,482 88,968 25,402 27,611 11,492,162 

2011 698,481 89,543 25,888 28,139 11,426,366 

2012 700,981 90,440 26,364 28,657 11,438,836 

2013 706,486 91,607 26,832 29,165 11,517,029 

2014 714,968 92,973 27,291 29,664 11,645,064 

2015 724,695 94,432 27,747 30,160 11,797,078 

2016 735,292 95,959 28,202 30,654 11,965,466 

2017 746,447 97,519 28,655 31,146 12,143,564 

2018 758,021 99,101 29,107 31,638 12,328,523 

2019 769,929 100,700 29,558 32,128 12,519,136 

2020 781,985 102,310 30,009 32,618 12,712,775 

2021 794,072 103,922 30,460 33,109 12,907,487 

2022 806,192 105,533 30,911 33,599 13,102,999 

2023 818,336 107,145 31,362 34,089 13,299,184 

2024 830,496 108,759 31,813 34,579 13,495,942 

2025 842,686 110,379 32,265 35,070 13,693,641 

2026 855,022 112,019 32,718 35,563 13,893,823 

2027 867,389 113,666 33,173 36,057 14,094,990 

2028 879,769 115,314 33,627 36,551 14,296,561 

2029 892,157 116,964 34,081 37,045 14,498,417 

2030 904,553 118,615 34,535 37,538 14,700,521 

2031 916,953 120,267 34,990 38,032 14,902,797 

2032 929,357 121,919 35,444 38,526 15,105,180 

2033 941,764 123,571 35,898 39,020 15,307,643 

2034 954,175 125,223 36,353 39,514 15,510,182 

2035 966,587 126,875 36,807 40,008 15,712,789 

2036 979,003 128,527 37,261 40,502 15,915,457 

2037 991,420 130,179 37,716 40,995 16,118,191 

2038 1,003,840 131,832 38,170 41,489 16,320,977 

2039 1,016,261 133,484 38,625 41,983 16,523,816 

2040 1,028,684 135,136 39,079 42,477 16,726,708 

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 NOx PM2.5 PM10 CO 

2001 935,494 41,514 15,625 16,984 2,584,786 

2002 909,607 43,401 15,092 16,404 2,552,368 

2003 877,441 45,661 14,417 15,670 2,510,927 

2004 841,151 48,164 13,679 14,869 2,469,934 

2005 801,985 50,675 12,886 14,007 2,423,497 

2006 762,092 53,207 12,090 13,142 2,375,768 

2007 724,443 55,750 11,311 12,295 2,328,182 

2008 687,350 58,296 10,553 11,470 2,280,928 

2009 651,744 60,797 9,824 10,678 2,235,187 

2010 618,843 63,228 9,149 9,945 2,191,484 

2011 588,283 65,613 8,525 9,266 2,149,407 

2012 561,699 67,843 7,983 8,678 2,112,511 

2013 538,510 69,883 7,534 8,189 2,081,945 

2014 518,615 71,789 7,144 7,766 2,054,769 

2015 502,307 73,583 6,823 7,416 2,031,684 

2016 488,502 75,245 6,549 7,118 2,011,569 

2017 477,287 76,781 6,324 6,874 1,995,319 

2018 469,041 78,169 6,156 6,691 1,983,611 

2019 462,146 79,469 6,012 6,535 1,974,297 

2020 457,338 80,655 5,908 6,422 1,968,663 

2021 453,687 81,768 5,826 6,333 1,965,024 

2022 451,360 82,796 5,768 6,270 1,963,888 

2023 449,882 83,756 5,726 6,224 1,964,657 

2024 449,089 84,663 5,696 6,191 1,967,014 

2025 449,054 85,517 5,680 6,174 1,971,025 

2026 449,611 86,327 5,675 6,168 1,976,557 

2027 450,640 87,096 5,678 6,172 1,983,392 

2028 451,987 87,828 5,687 6,182 1,991,331 

2029 453,610 88,537 5,701 6,197 1,999,984 

2030 455,480 89,225 5,719 6,217 2,009,248 

2031 457,536 89,896 5,741 6,240 2,019,028 

2032 459,725 90,554 5,765 6,266 2,029,227 

2033 462,071 91,197 5,792 6,296 2,039,870 

2034 464,529 91,828 5,821 6,327 2,050,883 

2035 467,079 92,448 5,851 6,360 2,062,245 

2036 469,685 93,060 5,883 6,394 2,073,873 

2037 472,348 93,664 5,915 6,429 2,085,737 

2038 475,055 94,261 5,948 6,465 2,097,797 

2039 477,796 94,853 5,982 6,502 2,110,011 

2040 480,560 95,440 6,016 6,539 2,122,336 

3-17 
Draft 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.2 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)19 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 Section 2.3. Many of these compounds are also part of 

the THC 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 are based on 

the work performed for EPA’s mobile source air toxic (MSAT) final rulemaking.20 The 

hazardous air pollutant inventories for all nonroad equipment except aircraft, locomotives, and 

commercial marine vessels in MSAT were developed using EPA’s National Mobile Inventory 

Model (NMIM). This model is an analytical framework that links a county-level database to our 

highway and nonroad models 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. 

The modeling results reflect the future use of renewable fuels as specified in the Energy 

Policy Act of 2005. Emissions were modeled for each county in the continental U.S. for 1999, 

2010, 2015, 2020, and 2030. For this proposal, a special NMIM simulation was also performed 

using the MSAT methodology for 2001 (our base year). The analysis for this additional year is 

also included in the MSAT documentation for completeness. 

To estimate the baseline air toxics inventories for this proposal, we started with the 

MSAT baseline case (no air toxics control) results for the Source Category Codes (SCCs) that 

contain the affected small nonroad and Marine SI engines.3 Those inventories were produced by 

the NMIM model using NONROAD2005a (the latest public release), so they do not reflect the 

emission modeling improvements we made for the proposed rule. Therefore, we corrected the 

MSAT air toxics inventories to mirror the results from our improved NONROAD2005c model. 

2

 The 15 POMs summarized in this chapter are acenaphthene, acenapthylene, anthracene, 

benz(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(g,h,i)perylkene, beno(k)fluoranthene, chrysene, 

dibenzo(a,h)anthracene,fluoranthene, fluorene, ideno(1,2,3,c,c)-pyrene, phenanthrene, and pyrene. 

3

 MSAT controls only affect the benzene content of nonroad gasoline fuel. Therefore, if the MSAT control 

case was used, only the benzene inventory for the nonroad engines affected by this proposal would be significantly 

affected. 

3-18 
Emission Inventory 

This adjustment was done to avoid the need to run the NMIM/MSAT model, which is quite 

resource intensive, using the new NONROAD2005c model. 

The hazardous air pollutant inventory for each exhaust and evaporative gaseous 

hydrocarbon species is estimated in NMIM as a fraction of VOC emissions, except for POMs, 

which are found in both the gas and particle phase. For each POM hydrocarbon species, the 

toxics inventory is estimated as a ratio to PM. Therefore, in order to correct the MSAT results to 

mirror the improved model results, we multiplied each MSAT hazardous air pollutant inventory 

for the applicable nonroad SCCs by the ratio of the VOC or PM emission results, as appropriate, 

from the new NONROAD2005c model to the respective NMIM NONROAD2005a model 

results. 

Tables 3.2-10 presents the 50-state baseline inventories, respectively, for toxic air 

emissions from small nonroad SI engines. Tables 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 Napthalene POM 

2001 33,534 5,165 8,035 2,826 462 418 93 

2020 22,923 3,169 5,182 2,429 270 409 107 

2030 26,502 3,663 5,991 2,805 312 475 123 

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 Napthalene POM 

2001 21,590 1,790 1,846 1,354 179 32 30 

2020 9,144 694 606 666 47 32 15 

2030 9,073 670 583 649 45 34 15 

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 proposed 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 

3-19 
Draft Regulatory Impact Analysis 

inventories includes both exhaust and evaporative hydrocarbon emissions. 

3.3.1 National Emission Inventory Development 

The national inventories are presented for 2001, 2015, and 2020 for the contiguous 48­

states of the U.S. and the District of Columbia.21 The stationary, area, motorcycle, aircraft, 

locomotive, commercial marine inventories were taken directly from EPA’s most recent air 

quality modeling for the PM NAAQS. The gaseous emission inventories for highway diesel 

vehicles and the 2001 calendar year PM emission estimates for highway diesel vehicles were 

also taken directly from that work. The emission inventories for on highway gasoline vehicles 

were taken from work performed for our Mobile Source Air Toxics (MSAT) rulemaking 

analysis. These inventories account for the future use of renewable fuels as required by the 

Energy Policy Act of 2005. Finally, the nonroad engine baseline inventories were estimated 

using the modified version of NONROAD2005a that was developed for this proposal, as 

discussed further in Section 3.2.1. 

3.3.1.1 VOC Emissions Contribution 

Table 3.3-1 provides the contribution of small nonroad SI engines, Marine SI engines 

and other source categories to total VOC emissions. The emissions from nonroad Small SI 

(<19kW) and Marine SI engines are 28 percent of the mobile source inventory and 13 percent of 

the total manmade VOC emissions in 2001. These percentages decrease slightly to 27 percent 

and 10 percent, respectively, by 2020. 

3.3.1.2 NOx Emissions Contribution 

Table 3.3-2 provides the contribution of nonroad small nonroad SI engines, Marine SI 

engines and other source categories to total NOx emissions. The emissions from small nonroad 

and Marine SI engines are 1 percent of the mobile source inventory and 1 percent of the total 

manmade NOx emissions in 2001. These percentages increase to 4 percent and 2 percent, 

respectively, by 2020. 

3.3.1.3 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 total PM2.5 and PM10 emissions, respectively. Both 

particle size categories from small nonroad and Marine SI engines are about 9 percent of the 

mobile source inventory and approximately 2 percent of the total manmade PM2.5 emissions in 

2001. These percentages stay about the same at about 10 percent and 2 percent, respectively, by 

2020. 

3.3.1.4 CO Emissions Contribution 

Table 3.3-5 provides the contribution of small nonroad SI engines, Marine SI engines 

and other source categories to total CO emissions. The emissions from small nonroad and 

3-20 
Emission Inventory 

Marine SI engines are 24 percent of the mobile source inventory and 22 percent of the total 

manmade CO emissions in 2001. These percentages decrease to 22 percent and increase to 27 

percent, respectively, by 2020. 

3-21 
Table 3.3-1: 50-State Annual VOC Baseline Emission Levels for

 Mobile and Other Source Categories

Category 

2OO1 

short tons 

% of 

mobile 

source % of total 

2015 

short tons 

% of 

mobile 

source % of total 

2020 

short tons 

 Small Handheld Nonroad SI 503,772 6.3% 2.9% 204,425 3.9% 1.5% 221 Small Nonhandheld Nonroad SI 699,516 8.8% 4.0% 582,107 11.1% 4.2% 627 Marine SI 1,035,768 13.0% 5.9% 552,888 10.5% 4.0% 502 SI Recreational Vehicles 497,207 6.3% 2.8% 593,624 11.3% 4.3% 443 Large Nonroad SI (>25hp) 132,820 1.7% 0.75% 20,012 0.4% 0.15% 12 Portable Fuel Containers* 244,545 3.1% 1.39% 238,055 4.5% 1.73% 254 Land-Based Nonroad Diesel 188,884 2.4% 1.07% 95,934 1.8% 0.70% 76 Marine Diesel 1,472 0.02% 0.01% 1,636 0.03% 0.01% 1 Com

mercial Marine 33,577 0.42% 0.19% 39,956 0.76% 0.29% 43

 Locomotive 39,279 0.49% 0.22% 35,423 0.67% 0.26% 34 Aircraft 22,084 0.28% 0.13% 25,426 0.48% 0.18% 27 Total Off Highway 3,398,924 42.8% 19.3% 2,389,485 45.5% 17.3% 2,245 Total Highway 4,540,133 57.2% 25.8% 2,865,967 54.5% 20.8% 2,769 Total Mobile Sources 7,939,058 100.0% 45.0% 5,255,453 100.0% 38.2% 5,015

 Stationary Point and Area Sources 9,692,344 - 55.0% 8,519,026 - 61.8% 8,475 Total Man-Made Sources 17,631,402 - 100.0% 13,774,479 - 100.0% 13,490
Table 3.3-2: 50-State Annual NOx Baseline Emission Levels

 for Mobile and Other Source Categories 

Category 

2001 

short tons 

% of 

mobile 

source % of total 

2015 

short tons 

% of 

mobile 

source % of total 

2020 

short ton

 Small Handheld Nonroad SI 2,678 0.0% 0.0% 3,647 0.1% 0.0% 3 Small Nonhandheld Nonroad SI 111,641 0.9% 0.5% 102,382 1.8% 0.9% 110 Marine SI 44,732 0.4% 0.2% 79,288 1.4% 0.7% 86 SI Recreational Vehicles 5,948 0.0% 0.0% 15,287 0.3% 0.1% 18 Large Nonroad SI (>25hp) 325,636 2.7% 1.51% 63,747 1.1% 0.54% 46 Land-Based Nonroad Diesel 1,548,236 12.7% 7.18% 969,065 16.7% 8.15% 678 Marine Diesel 39,301 0.32% 0.18% 47,282 0.82% 0.40% 48 Com

mercial Marine 930,886 7.63% 4.32% 953,398 16.47% 8.02% 989

 Locomotive 999,455 8.19% 4.64% 646,647 11.17% 5.44% 627 Aircraft 83,764 0.69% 0.39% 95,330 1.65% 0.80% 105 Total Off Highway 4,092,277 33.5% 19.0% 2,976,071 51.4% 25.0% 2,716 Total Highway 8,105,316 66.5% 37.6% 2,811,495 48.6% 23.6% 2,008 Total Mobile Sources 12,197,593 100.0% 56.6% 5,787,566 100.0% 48.7% 4,724

 Stationary Point and Area Sources 9,355,659 - 43.4% 6,107,354 - 51.3% 6,11 Total Man-Made Sources 21,553,252 - 100.0% 11,894,919 - 100.0% 10,836
Table 3.3-3: 50-State Annual PM2.5 Baseline Emission Levels

 for Mobile and Other Source Categories 

Category 

2001 

short tons 

% of 

mobile 

source % of total 

2015 

short tons 

% of 

mobile 

source % of total 

2020 

short to

 Small Handheld Nonroad SI 20,587 4.6% 0.9% 24,015 8.8% 1.2% 25 Small Nonhandheld Nonroad SI 4,879 1.1% 0.2% 6,403 2.4% 0.3% 6 Marine SI 16,837 3.7% 0.7% 7,352 2.7% 0.4% 6 SI Recreational Vehicles 12,301 2.7% 0.5% 15,864 5.8% 0.8% 1 Large Nonroad SI (>25hp) 1,610 0.4% 0.07% 2,207 0.8% 0.11% 2 Land-Based Nonroad Diesel 164,180 36.4% 6.80% 75,788 27.9% 3.68% 46 Marine Diesel 1,066 0.24% 0.04% 774 0.28% 0.04%  Commercial Marine 39,829 8.82% 1.65% 46,567 17.12% 2.26% 52 Locomotive 24,418 5.41% 1.01% 16,967 6.24% 0.82% 16 Aircraft 5,664 1.25% 0.23% 6,544 2.41% 0.32% 7 Total Off Highway 291,371 64.5% 12.1% 202,483 74.4% 9.8% 175 Total Highway 160,229 35.5% 6.6% 69,551 25.6% 3.4% 63 Total Mobile Sources 451,600 100.0% 18.7% 272,034 100.0% 13.2% 239 Stationary Point and Area Sources 1,963,264 - 81.3% 1,786,151 - 86.8% 1,817 Total Man-Made Sources 2,414,864 - 100.0% 2,058,185 - 100.0% 2,056
Table 3.3-4: 50-State Annual PM10 Baseline Emission Levels

 for Mobile and Other Source Categories 

Category 

2001 

short tons 

% of 

mobile 

source % of total 

2015 

short tons 

% of mobile 

source % of total 

2020 

short tons 

 Small Handheld Nonroad SI 22,378 4.3% 0.8% 26,104 7.6% 1.0% 28,2 Small Nonhandheld Nonroad SI 5,303 1.0% 0.2% 6,960 2.0% 0.3% 7,5 Marine SI 18,301 3.5% 0.6% 7,991 2.3% 0.3% 6,9 SI Recreational Vehicles 13,370 2.6% 0.5% 17,244 5.0% 0.7% 12,7 Large Nonroad SI (>25hp) 1,630 0.3% 0.06% 2,228 0.6% 0.09% 2,4 Land-Based Nonroad Diesel 169,258 32.5% 5.76% 78,132 22.7% 3.03% 47,5 Marine Diesel 1,099 0.21% 0.04% 798 0.23% 0.03% 7 Commercial Marine 41,409 7.96% 1.41% 48,448 14.07% 1.88% 54,6 Locomotive 25,173 4.84% 0.86% 17,521 5.09% 0.68% 16,5 Aircraft 6,490 1.25% 0.22% 7,539 2.19% 0.29% 8,1 Total Off Highway 304,412 58.5% 10.4% 212,964 61.8% 8.3% 185,5 Total Highway 216,032 41.5% 7.3% 131,415 38.2% 5.1% 128,6 Total Mobile Sources 520,444 100.0% 17.7% 344,379 100.0% 13.3% 314,1 Stationary Point and Area Sources 2,418,848 - 82.3% 2,236,080 - 86.7% 2,269,8 Total Man-Made Sources 2,939,292 - 100.0% 2,580,459 - 100.0% 2,583,9
Table 3.3-5: 50-State Annual CO Baseline Emission Levels 

for Mobile and Other Source Categories 

Category 

2001 

short tons 

% of 

mobile 

source % of total 

2015 

short tons 

% of mobile 

source 

% of 

total 

2020 

short ton

 Small Handheld Nonroad SI 1,101,646 1.3% 1.1% 948,479 1.8% 1.6% 1,024 Small Nonhandheld Nonroad SI 16,980,598 19.4% 17.6% 12,274,519 23.7% 20.3% 13,227 Marine SI 2,785,192 3.2% 2.9% 2,189,207 4.2% 3.6% 2,121 SI Recreational Vehicles 1,220,580 1.4% 1.3% 1,982,847 3.8% 3.3% 1,903 Large Nonroad SI (>25hp) 1,787,054 2.0% 1.85% 455,196 0.9% 0.75% 302 Land-Based Nonroad Diesel 893,320 1.0% 0.93% 483,358 0.9% 0.80% 310 Marine Diesel 6,293 0.01% 0.01% 8,705 0.02% 0.01% 9 Com

mercial Marine 123,806 0.14% 0.13% 147,449 0.28% 0.24% 158

 Locomotive 99,292 0.11% 0.10% 112,747 0.22% 0.19% 117 Aircraft 263,232 0.30% 0.27% 305,998 0.59% 0.51% 327 Total Off Highway 25,261,013 28.9% 26.2% 18,908,505 36.5% 31.2% 19,503 Total Highway 62,083,222 71.1% 64.4% 32,912,028 63.5% 54.4% 32,752 Total Mobile Sources 87,344,234 100.0% 90.6% 51,820,533 100.0% 85.6% 52,255

 Stationary Point and Area Sources 9,014,249 - 9.4% 8,734,963 - 14.4% 8,641 Total Man-Made Sources 96,358,483 - 100.0% 60,555,496 - 100.0% 60,897
Emission Inventory 

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 proposal. 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 proposed 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 

proposed 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, NOx, PM2.5, 

PM10, and CO 

The controlled exhaust and evaporative emission inventories for small nonroad and 

Marine SI engines include the effects of the proposed requirements and all existing applicable 

federal emission standards. We generated these inventories by modifying NONROAD2005c to 

account for the engine and equipment controls associated with the proposed standards. (See the 

baseline emission inventory discussion in Section 3.2 for the changes we made to the publically 

available NONROAD2005a model to develop NONROAD2005c.) 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 proposed Phase 3 emission standards and implementation schedule are shown in 

Table 3.4-1. While the standards are proposed to take effect in 2011 for Class II engines and 

2012 for Class I engines, we proposing a number of flexibilities for engine and equipment 

manufacturers that will allow the continued production and use of 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 the flexibilities 

being proposed. 

3-27 
Draft Regulatory Impact Analysis 

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

 sets only) 5 5 5 5 5 

Estimated Sales 

Percentage 83 83 93 93 100 

a Reflects maximum use of proposed compliance flexibilities by engine and equipment manufacturers. Used for 

modeling purposes only. 

The modeled emission factors corresponding to the proposed 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 0.302 391.13 0.080 0.08 1.095 

* The nonroad model calculates PM2.5 as 92 percent of PM10. 

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 0.727 pounds per 

3-28 
Emission Inventory 

horsepower-hour (lb/hp-hr). 

3.4.1.1.2 Marine SI Exhaust Emission Calculations 

For the control case, we developed new technology classifications for engines meeting 

the proposed 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 proposed 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 proposing 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 proposed 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 

18.8 

17.4 

16.7 

14.4 

15.3 

11.9 

9.1 

8.3 

8.3 

8.7 

10.0 

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 

180 

171 

173 

173 

152 

139 

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. MS4A applies to SD/I engines meeting the proposed standard 

through the use of aftertreatment. HC and NOx emission factors are based on test data presented 

3-29 
Draft Regulatory Impact Analysis 

in Chapter 4 for SD/I engines equipped with catalysts. CO emission factors are based on 

meeting the proposed 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 zero-hour 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 

All (MS4A) 1.80 1.64 1.60 1.15 55.0 1.36 345 

3.4.1.2 Controlled Evaporative Emission Rates 

Below, we present the effect of the proposed 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 proposed 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 7.5 g/m2/day on E10 and 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. 

Fill neck and vent hose containing vapor rather than liquid fuel are not subject to the 

proposed standards. Neither is hose on handheld equipment with winter use applications (e.g. 

handheld Class V chainsaws). No emission reductions are modeled for these hose types. 

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 

to meet the proposed 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 1.5 g/m2/day on fuel E10 and 0.75 g/gal/day at 29°C, regardless of fuel used. 

3-30 
Emission Inventory 

Two exceptions to the above discussion are nylon tanks used on handheld equipment and 

metal tanks. For these fuel tanks, we do not include any emissions reductions from baseline. 

3.4.1.2.3 Diurnal 

We are not proposing a diurnal emission requirement for Small SI equipment. Therefore, 

we do not model direct reductions in diurnal emissions. However, we are proposing a limit on 

diffusion emissions. As a result, we set the diffusion multiplier to 1.0 for all non-handheld 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, 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 proposed 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 proposed 

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, NOx, 

PM2.5, PM10, CO and SO2 

Tables 3.4-5 presents the 50-state controlled emission inventories, respectively, for small 

nonroad SI engines. Tables 3.4-6 provides the same information for Marine SI engines. 

3-31 
Draft Regulatory Impact Analysis 

Table 3.4-5: Controlled 50-State Annual Exhaust and Evaporative Emissions for 

Small Nonroad Spark-Ignition Engines (short tons) 

Year THC NOx PM2.5 PM10 CO 

2001 1,099,402 101,928 23,163 25,177 16,108,103 

2002 1,074,137 101,261 23,382 25,416 15,560,774 

2003 1,039,522 99,649 23,480 25,522 14,941,296 

2004 978,760 97,929 23,483 25,525 14,382,759 

2005 905,814 95,779 23,417 25,453 13,784,367 

2006 849,619 94,550 23,498 25,541 13,369,719 

2007 794,827 92,988 23,804 25,874 12,919,586 

2008 743,099 90,638 24,335 26,451 12,285,206 

2009 705,099 89,272 24,882 27,045 11,775,265 

2010 683,397 88,968 25,402 27,611 11,492,162 

2011 653,532 80,103 25,888 28,139 11,091,811 

2012 605,062 72,135 26,037 28,301 10,733,334 

2013 562,800 65,271 26,172 28,447 10,467,631 

2014 535,060 61,428 26,344 28,635 10,363,567 

2015 519,198 58,117 26,647 28,965 10,317,051 

2016 509,608 56,053 26,985 29,332 10,334,605 

2017 506,270 55,149 27,353 29,732 10,408,287 

2018 507,491 54,869 27,751 30,164 10,515,612 

2019 511,030 54,946 28,159 30,607 10,642,994 

2020 515,956 55,241 28,574 31,058 10,782,258 

2021 522,022 55,772 28,993 31,515 10,932,278 

2022 528,733 56,409 29,416 31,974 11,087,748 

2023 535,947 57,121 29,842 32,437 11,247,239 

2024 543,403 57,866 30,270 32,902 11,408,690 

2025 550,981 58,643 30,699 33,368 11,572,096 

2026 558,690 59,447 31,128 33,835 11,738,240 

2027 566,466 60,268 31,559 34,303 11,905,720 

2028 574,280 61,097 31,989 34,770 12,073,845 

2029 582,125 61,934 32,419 35,238 12,242,505 

2030 590,000 62,778 32,849 35,706 12,411,661 

2031 597,896 63,627 33,280 36,173 12,581,170 

2032 605,803 64,479 33,710 36,641 12,750,877 

2033 613,723 65,333 34,140 37,109 12,920,739 

2034 621,652 66,188 34,571 37,577 13,090,731 

2035 629,588 67,045 35,001 38,044 13,260,842 

2036 637,536 67,905 35,431 38,512 13,431,126 

2037 645,494 68,767 35,862 38,980 13,601,583 

2038 653,458 69,631 36,292 39,448 13,772,142 

2039 661,426 70,496 36,722 39,915 13,942,788 

2040 669,399 71,361 37,153 40,383 14,113,517 

3-32 
Emission Inventory 

Table 3.4-6: Controlled 50-State Annual Exhaust and Evaporative Emissions for 

Marine Spark-Ignition Engines (short tons) 

Year THC NOx PM2.5 PM10 CO 

2001 935,494 41,514 15,625 16,984 2,584,786 

2002 909,607 43,401 15,092 16,404 2,552,368 

2003 877,441 45,661 14,417 15,670 2,510,927 

2004 841,151 48,164 13,679 14,869 2,469,934 

2005 801,985 50,675 12,886 14,007 2,423,497 

2006 762,092 53,207 12,090 13,142 2,375,768 

2007 724,443 55,750 11,311 12,295 2,328,182 

2008 687,350 58,296 10,553 11,470 2,280,928 

2009 634,175 58,835 9,508 10,335 2,214,580 

2010 582,548 59,308 8,520 9,261 2,150,304 

2011 532,769 59,541 7,584 8,243 2,086,638 

2012 485,231 59,635 6,733 7,319 2,028,270 

2013 441,421 59,547 5,978 6,497 1,976,179 

2014 401,152 59,336 5,286 5,746 1,927,610 

2015 364,619 59,024 4,666 5,072 1,883,241 

2016 330,888 58,595 4,099 4,455 1,842,019 

2017 300,138 58,051 3,588 3,900 1,804,951 

2018 272,927 57,378 3,143 3,416 1,772,827 

2019 249,343 56,577 2,767 3,007 1,743,893 

2020 228,847 55,656 2,448 2,661 1,718,956 

2021 210,304 54,638 2,164 2,352 1,696,117 

2022 194,021 53,570 1,920 2,087 1,676,245 

2023 180,805 52,527 1,729 1,880 1,659,281 

2024 169,904 51,497 1,577 1,714 1,644,771 

2025 160,668 50,466 1,452 1,578 1,632,439 

2026 152,898 49,451 1,348 1,465 1,622,175 

2027 146,673 48,468 1,267 1,377 1,614,086 

2028 141,435 47,561 1,200 1,304 1,608,064 

2029 137,294 47,142 1,148 1,248 1,606,899 

2030 134,028 46,859 1,107 1,203 1,607,678 

2031 131,342 46,691 1,073 1,166 1,610,007 

2032 129,305 46,590 1,046 1,137 1,613,454 

2033 127,751 46,531 1,025 1,114 1,617,823 

2034 126,621 46,503 1,010 1,097 1,622,954 

2035 125,891 46,508 999 1,086 1,628,820 

2036 125,434 46,536 992 1,079 1,635,236 

2037 125,187 46,587 988 1,074 1,642,153 

2038 125,113 46,659 986 1,071 1,649,518 

2039 125,179 46,755 985 1,070 1,657,283 

2040 125,343 46,874 985 1,071 1,665,392 

3-33 
Draft Regulatory Impact Analysis 

3.4.2 Controlled Hazardous Air Pollutant Estimates 

The proposed 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 used the same methodology that was used for the baseline inventories along with the results 

of the controlled emission inventories for VOC or PM, as appropriate. The methodology is 

described in Section 3.2. 

Controlled inventories were calculated for the seven major types of air toxic emissions: 

benzene, formaldeyde, acetaldehyde, 1,3-butadiene, acrolein, napthalene, and 15 other 

compounds grouped together as polycyclic organic matter (POM) for this analysis.4 Table 3.4-7 

presents the 50-state controlled inventories, respectively, small nonroad SI engines. Table 3.4-8 

provide 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 Naptha-lene POM 

2001 33,534 5,165 8,035 2,826 462 418 93 

2020 16,018 2,214 3,621 1,697 189 286 102 

2030 18,341 2,535 4,146 1,941 216 329 118 

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 Naptha-lene POM 

2001 21,590 1,790 1,846 1,354 179 32 30 

2020 4,890 371 324 356 25 17 7 

2030 3,117 230 200 223 15 12 4 

3.5 Projected Emissions Reductions from the Proposed Rule 

This section presents the projected total emission reductions associated with the proposed 

rule. We calculated the reductions by subtracting the baseline inventories from Section 3.2 by 

the controlled inventories from Section 3.4. 

4

 The 15 POMs summarized in this chapter are acenaphthene, acenapthylene, anthracene, 

benz(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(g,h,i)perylkene, beno(k)fluoranthene, chrysene, 

dibenzo(a,h)anthracene,fluoranthene, fluorene, ideno(1,2,3,c,c)-pyrene, phenanthrene, and pyrene. 

3-34 
Emission Inventory 

3.5.1 Results for THC, 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 proposal. The earliest proposed Phase 3 standards for small nonroad SI engines begin in 

2008. Similar proposed 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 3.5-6 show the combined baseline, controlled, and by 

contrast the reduction emission inventories over time for small nonroad and Marine SI engines. 

3-35 
Table 3.5-1: Total 50-State Annual Exhaust and Evaporative Emission Reductions 

for Small SI Spark-Ignition Engines (short tons) 

Year 

THC NOx PM2.5 PM10 CO 

Tons % Tons % Tons % Tons % Tons 

2008 4,935 1 0 0 0 0 0 0 0 2009 10,844 2 0 0 0 0 0 0 0 2010 17,085 2 0 0 0 0 0 0 0 2011 44,949 6 9,440 11 0 0 0 0 334,555 2012 95,920 14 18,305 20 327 1 356 1 705,503 2013 143,686 20 26,336 29 661 2 718 2 1,049,398 2014 179,908 25 31,545 34 947 3 1,029 3 1,281,497 2015 205,497 28 36,315 38 1,100 4 1,195 4 1,480,027 2016 225,684 31 39,906 42 1,216 4 1,322 4 1,630,861 2017 240,176 32 42,370 43 1,301 5 1,414 5 1,735,277 2018 250,529 33 44,232 45 1,356 5 1,474 5 1,812,911 2019 258,899 34 45,754 45 1,399 5 1,521 5 1,876,142 2020 266,030 34 47,069 46 1,435 5 1,560 5 1,930,518 2021 272,051 34 48,150 46 1,466 5 1,594 5 1,975,208 2022 277,458 34 49,124 47 1,495 5 1,624 5 2,015,250 2023 282,389 35 50,024 47 1,520 5 1,652 5 2,051,946 2024 287,093 35 50,893 47 1,543 5 1,677 5 2,087,252 2025 291,705 35 51,737 47 1,566 5 1,702 5 2,121,545 2026 296,331 35 52,572 47 1,590 5 1,728 5 2,155,582 2027 300,923 35 53,398 47 1,614 5 1,754 5 2,189,270 2028 305,489 35 54,217 47 1,638 5 1,780 5 2,222,715 2029 310,032 35 55,030 47 1,662 5 1,807 5 2,255,912 2030 314,553 35 55,837 47 1,686 5 1,833 5 2,288,860 2031 319,057 35 56,640 47 1,710 5 1,859 5 2,321,627 2032 323,554 35 57,440 47 1,734 5 1,885 5 2,354,303 2033 328,042 35 58,238 47 1,758 5 1,911 5 2,386,904 2034 332,523 35 59,035 47 1,782 5 1,937 5 2,419,451 2035 336,999 35 59,830 47 1,806 5 1,963 5 2,451,948 2036 341,467 35 60,623 47 1,830 5 1,989 5 2,484,331 2037 345,926 35 61,412 47 1,854 5 2,015 5 2,516,608 2038 350,382 35 62,201 47 1,878 5 2,042 5 2,548,836 2039 354,835 35 62,988 47 1,902 5 2,068 5 2,581,029 2040 359,285 35 63,775 47 1,926 5 2,094 5 2,613,191 
Table 3.5-2: Total 50-State Annual Exhaust and Evaporative Emission Reductions 

for Marine SI Spark-Ignition Engines (short tons) 

Year 

THC NOx PM2.5 PM10 CO 

Tons % Tons % Tons % Tons % Tons 

2009 17,569 3 1,962 3 315 3 343 3 20,607 2010 36,295 6 3,920 6 629 7 683 7 41,179 2011 55,514 9 6,072 9 941 11 1,023 11 62,769 2012 76,468 14 8,208 12 1,250 16 1,359 16 84,241 2013 97,088 18 10,336 15 1,556 21 1,692 21 105,767 2014 117,463 23 12,453 17 1,858 26 2,019 26 127,160 2015 137,688 27 14,558 20 2,157 32 2,344 32 148,443 2016 157,614 32 16,650 22 2,450 37 2,663 37 169,550 2017 177,149 37 18,730 24 2,737 43 2,975 43 190,368 2018 196,113 42 20,792 27 3,013 49 3,275 49 210,784 2019 212,803 46 22,892 29 3,246 54 3,528 54 230,404 2020 228,491 50 24,999 31 3,461 59 3,762 59 249,707 2021 243,383 54 27,131 33 3,662 63 3,981 63 268,906 2022 257,338 57 29,226 35 3,849 67 4,183 67 287,643 2023 269,076 60 31,228 37 3,997 70 4,344 70 305,376 2024 279,185 62 33,166 39 4,119 72 4,477 72 322,243 2025 288,385 64 35,051 41 4,228 74 4,596 74 338,585 2026 296,713 66 36,877 43 4,327 76 4,703 76 354,383 2027 303,966 67 38,628 44 4,411 78 4,795 78 369,306 2028 310,552 69 40,267 46 4,487 79 4,877 79 383,267 2029 316,315 70 41,395 47 4,553 80 4,949 80 393,085 2030 321,452 71 42,366 47 4,613 81 5,014 81 401,570 2031 326,194 71 43,206 48 4,668 81 5,074 81 409,021 2032 330,420 72 43,964 49 4,719 82 5,130 82 415,773 2033 334,319 72 44,666 49 4,767 82 5,181 82 422,048 2034 337,908 73 45,325 49 4,811 83 5,230 83 427,929 2035 341,188 73 45,940 50 4,852 83 5,274 83 433,425 2036 344,251 73 46,524 50 4,890 83 5,315 83 438,637 2037 347,161 73 47,077 50 4,927 83 5,355 83 443,584 2038 349,942 74 47,602 51 4,962 83 5,394 83 448,279 2039 352,617 74 48,098 51 4,997 84 5,431 84 452,729 2040 355,217 74 48,567 51 5,031 84 5,468 84 456,943 
Table 3.5-3: Total 50-State Annual Exhaust and Evaporative Emission Reductions 

for Small Nonroad and Marine SI Spark-Ignition Engines (short tons) 

Year THC NOx PM2.5 PM10 CO 

Tons % Tons % Tons % Tons % Tons 

2008 4,935 0 0 0 0 0 0 0 0 2009 28,413 2 1,962 1 315 1 343 1 20,607 2010 53,380 4 3,920 3 629 2 683 2 41,179 2011 100,463 8 15,512 10 941 3 1,023 3 397,324 2012 172,387 14 26,513 17 1,578 5 1,715 5 789,744 2013 240,774 19 36,672 23 2,217 6 2,410 6 1,155,165 2014 297,371 24 43,998 27 2,805 8 3,049 8 1,408,656 2015 343,185 28 50,874 30 3,256 9 3,539 9 1,628,471 2016 383,298 31 56,556 33 3,666 11 3,985 11 1,800,412 2017 417,325 34 61,099 35 4,038 12 4,389 12 1,925,645 2018 446,643 36 65,024 37 4,369 12 4,749 12 2,023,696 2019 471,702 38 68,646 38 4,645 13 5,049 13 2,106,545 2020 494,520 40 72,069 39 4,896 14 5,322 14 2,180,225 2021 515,434 41 75,281 41 5,129 14 5,575 14 2,244,115 2022 534,797 43 78,350 42 5,343 15 5,808 15 2,302,893 2023 551,465 43 81,252 43 5,516 15 5,996 15 2,357,322 2024 566,279 44 84,059 43 5,662 15 6,154 15 2,409,495 2025 580,091 45 86,788 44 5,794 15 6,298 15 2,460,130 2026 593,044 45 89,448 45 5,917 15 6,431 15 2,509,965 2027 604,889 46 92,025 46 6,025 16 6,549 16 2,558,576 2028 616,041 46 94,484 47 6,125 16 6,658 16 2,605,982 2029 626,348 47 96,425 47 6,215 16 6,755 16 2,648,997 2030 636,005 47 98,203 47 6,299 16 6,847 16 2,690,429 2031 645,251 47 99,845 48 6,379 16 6,933 16 2,730,649 2032 653,974 47 101,403 48 6,454 16 7,015 16 2,770,076 2033 662,361 47 102,904 48 6,525 16 7,092 16 2,808,952 2034 670,431 47 104,360 48 6,593 16 7,167 16 2,847,380 2035 678,187 47 105,770 48 6,658 16 7,237 16 2,885,372 2036 685,717 47 107,146 48 6,720 16 7,305 16 2,922,968 2037 693,087 47 108,489 48 6,781 16 7,371 16 2,960,192 2038 700,324 47 109,803 49 6,841 16 7,436 16 2,997,115 2039 707,452 47 111,087 49 6,899 15 7,499 15 3,033,757 2040 714,503 47 112,342 49 6,957 15 7,562 15 3,070,134 

Note: annualized tons (2008-2038) for HC and NOx are 374,500 and 55,800 at a 7% discount and 431,800 and 64,800 at a 3% 
Emission Inventory 

Figure 3.5-1: 50-State Annual THC Exhaust and Evaporative Emissions for 

Small SI and Marine SI 

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 NOx Exhaust Emissions for Small SI and Marine SI 

0

50,000

100,000

150,000

200,000

250,000

2000 2005 2010 2015 2020 2025 2030 2035 2040

Year 

Tons /Year 

Baseline

Controlled

3-39
 
Draft Regulatory Impact Analysis 

Figure 3.5-3: 50-State Annual PM2.5 Exhaust Emissions for Small SI 

and Marine SI 

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

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

3-40
 
Emission Inventory 

Figure 3.4-5: 50-State Annual CO Emissions from 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

Tons 

Baseline

Controlled

2000 2005 2010 2015 2020 2025 2030 2035 2040

Year 

3.5.2 Results for Hazardous Air Pollutants

 Tables 3.5-4 presents the 50-state exhaust and evaporative air toxics emission inventory 

and percent reductions, respectively, for small nonroad SI engines that are expected to 

accompany the proposed standards. Table 3.5-5 provides the same information for Marine SI 

engines. Tables 3.5-6 summarizes the combined hazardous air pollutant reductions for the 

proposal. These results are displayed for 2020 and 2030, when most or all of the engines subject 

to the proposed 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 Napthale

Tons % Tons % Tons % Tons % Tons % Tons 

2020 6,906 30 955 30 1,561 30 732 30 81 30 123 2030 8,160 31 1,128 31 1,845 31 864 31 96 31 146 

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 Napthale

Tons % Tons % Tons % Tons % Tons % Tons 

2020 4,254 47 323 47 282 47 310 47 22 47 15 2030 5,955 66 440 66 382 66 426 66 30 66 23 

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 Napthale

Tons % Tons % Tons % Tons % Tons % Tons 

2020 11,160 35 1,278 33 1,843 32 1,041 34 103 33 138 2030 14,116 40 1,567 36 2,227 34 1,290 37 126 35 169 
Emission Inventory 

3.6 Emission Inventories Used for Air Quality Modeling 

This section describes the methodology we used to develop the emission inventories for 

the air quality modeling. The inventories represent emissions for the summer ozone season (i.e., 

June, July, and August) in calendar years 2001, 2015, 2020, and 2030. Emissions were 

estimated are for 37 of the most eastern states, which is the geographic area of the air quality 

modeling domain. 

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 process. Given that lead time requirement, air quality modeling is often based 

analytical methods that may be superceded or on a control scenario that does not specifically 

match the final set of emission standards. Indeed, for this proposed rulemaking both instances 

have occurred. Therefore, this section also describes the changes to our emission inventory 

models, modeling inputs, and resulting emission inventories between the preliminary baseline 

and control scenarios used for the air quality modeling, and the updated final baseline and 

control scenarios for the proposed rule. 

3.6.1 Methodology for Air Quality Modeling 

The air quality modeling for the proposal is in large part taken from the work performed 

for EPA’s Clean Air Interstate Rule (CAIR) for stationary sources.22 This approach was adopted 

to be consistent with, what was then, EPA’s most recent ozone-related rulemaking and to 

conserve resources by taking advantage of the existing inventory preparation (i.e., input files) 

and results. The CAIR modeling domain consists of 37 states in the eastern U.S. and the District 

of Columbia. Emission inventories were developed for the following pollutants: VOC, NOx, 

PM2.5, PM10, CO, SOx, and NH3. Air quality results were generated for the summer ozone 

season (i.e., June, July, and August) and the CAIR calendar years 2001, 2015, and 2020. We 

also modeled calendar year 2030 specifically for this proposal as described below. 

The special 2030 calendar year model simulation was performed by preparing CAIR-like 

emission inventories for all source categories. For non-mobile sources, we simply carried 

forward the inventories from 2020. For mobile sources, we prepared highway and off- highway 

inventories for 2030 using the same methodology that was used to prepare the CAIR inventories 

for the previous calendar years. 

The emissions inventory methodology and results for the nonroad sources and the results 

for small nonroad and Marine SI engines are in the docket for this proposed rule. 23,24,25,26 

3.6.2 Baseline Scenario Emission Inventories 

Our preliminary baseline emission inventories without the proposed controls for small 

nonroad and Marine SI engines were the same as the CAIR rule’s “control” scenario. A special 

version of the draft NONROAD2004 model was used to generate the nonroad engine inventories 

3-43 
Draft Regulatory Impact Analysis 

for that rule. That version of the model is referred to as NONROAD2004n. It is identical to the 

draft NONROAD2004 model, which was the most recent publically available nonroad model at 

the time, except for a modification to allow a separate diesel fuel sulfur value for marine 

equipment (an unremarkable feature relative to the proposed rule). NONROAD2004n was 

executed within the framework of EPA’s National Mobile Source Inventory Model (NMIM) that 

links a county-level database to model and collates the output into a single database table. The 

resulting estimates for nonroad and Marine SI engines account for local differences in fuel 

characteristics and temperatures. NONROAD2004n is discussed in more detail later in this 

section. 

Table 3.6-1 presents the preliminary 37-state baseline inventories for VOC, NOx, PM2.5, 

PM10, and CO during the 3-month summer ozone season that were used in the air quality 

modeling for small nonroad and Marine SI engines.5 These values are an aggregation of the 

county-level NMIM results. 

Table 3.6-1 37-State Preliminary Baseline Scenario Emissions for
 

Air Quality Modeling
 

Application Year VOC PM10 PM2.5 NOx CO 

Small Nonroad SI 

Subject to the 

Proposal 

2001 264,951 6,738 6,199 37,466 4,795,058 

2020 156,401 7,968 7,330 31,477 6,660,408 

2030 179,717 9,114 8,385 36,084 7,691,956

 Marine SI 2001 264,951 18,397 16,925 18,576 927,890 

2020 162,488 13,930 12,815 33,061 904,964 

2030 157,380 14,534 13,371 36,332 949,504 

The final baseline inventories for the proposal were estimated with a special version of 

the NONROAD2005a model, which is the newest public release of our nonroad model. This 

special version is named NONROAD2005c. Generally, we revised the model to incorporate new 

test results for nonhandheld Small SI engines that comply with the existing Phase 2 standards. 

Also, the model was modified to acknowledge the continued use of side-valve engine designs in 

Class I nonhandheld engines meeting those standards. In the Phase 2 rulemaking for small 

nonroad SI engines, 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 revisions we made to develop this new version is also 

described in Section 3.2. 

Table 3.6-2 compares the preliminary and final 37-state baseline scenario inventories for 

5

 Inventories for SOx and NH4 are not important for the purposes of this discussion and can be found in the 

docket along with information on the other pollutants presented here. See reference 26. 

3-44 
Emission Inventory 

small nonroad and Marine SI engines. This information is presented primarily for information 

purposes, since it is the percentage difference between a model’s baseline and control scenario 

that is used for comparing the inventories from the final proposal to those used in the air quality 

modeling as discussed further in Section 3.6.3. As shown, the difference in the baseline 

scenarios between the two models ranges from about -2 percent for VOC in 2020 to about 50 

percent for PM2.5 in 2020 for the combined Small SI engine and Marine SI engine categories. 

3-45 
Table 3.6-2: Comparison of 37-State Baseline Scenario Emissions for

Preliminary Air Quality Modeling and Final Proposal

Applications Year 

VOC [short tons] NOx [short tons] PM2.5 

Final Preliminary Difference Final Preliminary Difference Final Preli

Small Nonroad SI Subject to the Proposal 

2020 219,404 156,401 63,003 26,947 31,477 (4,530) 7,946 7,2030 253,162 179,717 73,445 31,101 36,084 (4,983) 9,141 8,

 Marine SI 2020 230,222 162,488 67,734 40,949 33,061 7,888 3,108 12

2030 228,081 157,380 70,701 44,949 36,332 8,617 3,008 13

Total 2020 449,626 318,889 (4,731) 67,896 64,538 (12,418) 11,054 20

2030 481,243 337,096 2,744 76,050 72,415 (13,600) 12,149 21
Emission Inventory 

Table 3.6-2 (Cont’d)
 

Comparison of 37-State Baseline Scenario Emissions for
 

Preliminary Air Quality Modeling and Final Proposal 
 

Applications Year 

PM10 [short tons] CO [short tons] 

Final Preliminary Difference Final Preliminary Difference 

Small Nonroad 

SI Subject to the 

Proposal 

2020 8,637 7,968 669 3,832,891 6,660,408 (2,827,517) 

2030 9,936 9,114 822 4,414,165 7,691,956 (3,277,791)

 Marine SI 2020 3,378 13,930 (10,552) 1,040,807 904,964 135,843 

2030 3,270 14,534 (11,264) 1,061,971 949,504 112,467 

Total 2020 12,015 21,898 (9,883) 4,873,698 7,565,372 (2,691,674) 

2030 13,206 23,648 (10,442) 5,476,136 8,641,460 (3,165,324) 

These baseline inventory differences are obviously due to the differences in 

NONROAD2004n and the special version of the model that we developed for the final proposal, 

i.e., NONROAD2005c, as well as the inputs to the models. As already mentioned, 

NONROAD2004n is equivalent to publically available draft NONROAD model with a revision 

that is insignificant for the purposes of the proposal as described above. The most substantial 

changes between the two models occurred between publically available NONROAD2004 and 

the publically available NONROAD2005a. The principle revisions that are relevant to this 

proposal generally include: 

1) All new evaporative emission categories for fuel tank permeation, hose 

permeation, hot soak, and running losses; 

2) Added capability to model emissions using daily values for temperature and 

gasoline volatility at the national and state level; 

3) Revised methodology for calculating diurnal evaporative emissions; 

4) Added the effect of evaporative emission standards for recreational vehicles and 

large spark-ignition engines; and 

5) Updated geographic allocation factors to distribute national equipment 

populations to state and local jurisdictions; and 

The additional changes we made from NONROAD2005a to develop NONR2005c for the 

proposal are important, but less significant. These revisions are described in detail in 

Section 3.2. 

3.6.3 Control Scenario Emission Inventories 

At the time we were ready to develop the control scenario for the air quality analysis, our 

modeling techniques and emission inputs significantly improved beyond NONROAD2004a 

3-47 
Draft Regulatory Impact Analysis 

model, which was used to generate the CAIR-related base case. So we created a special version 

of NONROAD2004a to better estimate the exhaust and evaporative refueling emissions for small 

nonroad and Marine SI engines. The special version of the model was designated as 

NONROAD2004n2. We also created special spreadsheet models to expand and improve our 

estimates of the other evaporative emissions from these engines, i.e., diurnal (including 

effusion), running loss, hot soak, and hose and tank permeation. 

The principle changes that were incorporated into NONROAD2004n2 for exhaust and 

refueling emissions are: 

1.	 Updated the estimated sales fractions by engine class and technology to account 

for the continued sales of Class I Small SI engines using side-valve technology 

(we assumed these engines would be replaced with overhead-valve technology in 

the Phase 2 standard rulemaking); 

2.	 Revised emission factors and deterioration rates for Class I Small SI engines 

subject to Phase 2 standards based on preliminary testing; 

3.	 Updated Marine SI engine population distributions by horsepower category; and 

4.	 Updated Marine SI engine emission factors for hydrocarbons, CO, and NOx. 

The principle changes that were incorporated into the spreadsheet models for the other 

evaporative emissions are: 

1.	 Added all new evaporative emission categories for fuel tank and hose permeation; 

and 

2.	 Updated the methodology for diurnal evaporative emissions. 

These new tools were utilized to derive the preliminary control inventories for the air 

quality modeling. More specifically, we constructed alternative baseline and control scenarios 

for small nonroad and Marine SI engines with the NONROAD2004n2 model for exhaust and 

evaporative refueling emissions, and the new spreadsheet models for the other evaporative 

emissions. The percent change in emissions from the alternative baseline to the alternative 

control inventory for each pollutant was then applied to the respective CAIR-related preliminary 

baseline inventories to generate the preliminary control scenario inventories for the proposed 

rule. This approach was taken to preserve the existing air quality modeling input files, while still 

reflecting the full scope of the emission reductions from the proposed rule. This methodology 

has been documented in detail and a copy of the NONROAD2004n2 model and evaporative 

emission spreadsheets have been placed in the docket for this proposal. 

For this proposal, the specific emission standards and associated control requirements 

were not fully identified when the air quality modeling was performed. As a result, we modeled 

a variety of preliminary control scenarios with the improved inventory tools described above to 

accommodate a range of possible regulatory outcomes. The air quality modeling outcomes for 

the preliminary scenario that most closely matches the percent change in emissions associated 

with the final control scenario will be used in Chapter 8 to estimate the health and welfare 

benefits of the proposal. Using the percentage reduction in emissions to select the appropriate 

3-48 
Emission Inventory 

preliminary control scenario matches the methodology that was originally used to develop the 

preliminary air quality control scenario itself, as described in the preceding paragraph. 

Before selecting the preliminary air quality control scenario for our benefits assessment 

in Chapter 8, we would like to reiterate that the final control scenario inventories for the proposal 

were estimated with a special version of the NONROAD2005a model, just as we used for the 

final baseline scenario inventories. It should be noted that NONROAD2005a incorporates and 

expands upon the modeling improvements described above for NONROADn2 and the 

evaporative spreadsheet models, which were used to generate the percentage reduction factors 

associated with the alternative baseline and control scenarios. Of course, the special version 

reflects further modeling improvements for the proposal. Section 3.6.2 generally describes the 

changes we made to the NONROAD2005a base model. A more detailed discussion of the 

special version of the model is also contained in Section 3.2.

 Table 3.6-3 compares the percentage emission reductions that are associated with the 

final control scenario and preliminary air quality control scenario that most closely matches the 

final scenario for the 37-state modeling domain. The inventories are not shown for 2001 or 2015 

because the proposed requirements either have no effect on the inventories, i.e., 2001, or have 

not yet significantly “rolled over” into the fleet of equipment, i.e., 2015. Also, results are 

presented only for the two most important pollutants relative to this rule for selection purposes, 

i.e., VOC and NOx. As shown, the emission reductions are, on average, very close to the final 

control scenario based on the selection criteria. Therefore, this case is selected as the most 

representative preliminary control scenario relative to the air quality results associated with the 

proposal. 

Table 3.6-4 directly compares the emission inventories (i.e., tons) for the selected 

preliminary control scenario to the final control scenario. As previously described, this 

information is presented primarily for information purposes, since it is the percentage difference 

between a model’s baseline and control scenario that is used for comparing the inventories from 

the final proposal to those used in the air quality modeling. As shown, the difference in the 

control scenarios for the two models ranges from about -27 percent for CO in 2030 to about 50 

percent for VOC in 2030 for the combined Small SI engine and Marine SI engine categories. 

As with the baseline scenarios, the differences in the preliminary and final control 

scenarios inventories are due to the differences in models and inputs used in the analysis. Unlike 

the baseline scenario discussion, however, the comparison of these differences is substantially 

complicated by the use of not just two, but three different modeling platforms, i.e., 

NONROAD2004n (used for the CAIR-related base case), NONROADn2 and the spreadsheet 

models (used for the percent reduction factors), and the special version of NONROAD2005a 

(used for the final control scenario). Generally, the greatest differences result from using the 

NONROAD2004n model for the preliminary baseline scenario (from which the preliminary 

control scenario inventories were directly calculated) and the special version of 

NONROAD2005a model. The differences between these two models is described in 

Section 3.6.2. We expect that any new air quality modeling that may be needed for the final rule 

would be based on a single, consistent modeling platform. 

3-49 
Table 3.6-3: Comparison of 37-State Emission Reductions for Small Nonroad and Marine SI 

 for Emission Benefit Analysis Purposes (Tons or Percent Reduction/Year) 

Pollutant Year 

Preliminary Proposal 

(Air Quality Modeling) Final Proposal 

Base 

(tons) 

Control 

(tons) 

Reduction 

(tons) 

Percent 

Reduction 

(%) 

Base 

(tons) 

Control 

(tons) 

Redu

(ton

VOC 2020 318,889 168,589 150,300 47 446,626 252,287 197,

2030 337,096 147,664 189,432 56 481,243 223,834 257,

NOx 2020 64,538 41,331 23,207 36 67,586 42,802 24,7

2030 72,415 40,341 32,074 44 76,049 40,503 35,5
Table 3.6-4: Comparison of 37-State Control Scenario Emissions for

Preliminary Air Quality Modeling Scenario and Final Proposal (Tons/Year)

Applications Year 

VOC [short tons] NOx [short tons] 

Final Preliminary Difference Final Preliminary Difference Final 

Small Nonroad SI Subject to the Proposal 

2020 138,406 92,605 45,801 14,416 15,240 (824) 7,507 

2030 157,626 105,348 52,278 16,306 17,107 (801) 8,627 

 Marine SI 2020 113,881 75,984 37,897 28,386 26,091 2,295 1,287 

2030 66,208 42,316 23,892 24,197 17,107 7,090 582 

Total 2020 252,287 168,589 83,698 42,802 41,331 1,471 8,794 

2030 223,834 147,664 76,170 40,503 34,214 6,289 9,209 
Draft Regulatory Impact Analysis 

Table 3.6-4 (Cont’d)
 

Comparison of 37-State Control Scenario Emissions for
 

Preliminary (Nominal) Air Quality Modeling and Final Proposal 
 

Applications Year 

PM10 [short tons] CO [short tons] 

Final Preliminary Difference Final Preliminary Difference 

Small Nonroad 

SI Subject to the 

Proposal 

2020 8,160 7,967 193 3,231,266 4,868,575 (1,637,309) 

2030 9,377 9,113 264 3,703,736 5,593,529 (2,316,989)

 Marine SI 2020 1,399 3,709 (2,310) 908,162 726,853 181,309 

2030 633 821 (188) 848,425 675,398 173,027 

Total 2020 9,559 11,676 (2,117) 4,139,428 5,595,428 (1,456,000) 

2030 10,010 9,934 76 4,552,161 6,268,927 (1,716,766) 

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. “NONROAD2005c Emissions 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-2004-0008-0517.1. 

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, March 8, 2007, U.S. Environmental Protection Agency, Office of 

Transportation and Air Quality, Ann Arbor, Michigan, December 2005. Docket Identification EPA-HQ-OAR-2004­

0008-0546. 

5. “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. 

6. “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. 

7. “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. 

8. “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. 

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 U.S. Petroleum Supply and Demand: Base Case,” Energy Information Administration\Short-Term 

Energy Outlook -- September 2006, Table A5, http://www.eia.doe.gov/emeu/steo/pub/a5tab.html, Docket 

Identification EPA-HQ-OAR-2004-0008-0472 

11. “Annual Energy Outlook 2006; With Projections to 2030,” Energy Information Administration, 

DOE/EIA-0383(2006), December 2005, http://www.eia.doe.gov/oiaf/aeo/excel/figure91_data.xls (gasoline), Docket 

Identification EPA-HQ-OAR-2004-0008-0471. 

3-53 
Draft Regulatory Impact Analysis 

12. “Annual Energy Outlook 2006; With Projections to 2030,” Energy Information Administration,
 

DOE/EIA-0383(2006), December 2005, http://www.eia.doe.gov/oiaf/aeo/excel/figure95_data.xls (ethanol), Docket
 

Identification EPA-HQ-OAR-2004-0008-0470.
 

13. “Fuel and Oil Hoses,” Recommended Practice J30, Society of Automotive Engineers, June 1998. Docket
 

Identification EPA-HQ-OAR-2004-0008-0176.
 

14. “Personal Watercraft Fuel Systems,” Recommended Practice J2046, Society of Automotive Engineers, January,
 

19, 2001. Docket Identification EPA-HQ-OAR-2004-0008-0179.
 

15. “Marine Fuel Hoses,” Recommended Practice J1527, Society of Automotive Engineers, Revised February 1993.
 

Docket Identification EPA-HQ-OAR-2004-0008-0177.
 

16. “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.
 

17. 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.
 

18. "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.
 

19. U. S. Environmental Protection Agency. 2006. National-Scale Air Toxics Assessment for 1999.
 

Http://www.epa.gov/ttn/ate/nata1999.
 

20. “Hazardous Air Pollutant Emission Inventories for the Small Nonroad and Marine Engine Proposed
 

Rulemaking,” Memorandum and attachments from Richard Wilcox, U.S. Environmental Protection Agency, Office
 

of Transportation and Air Quality, Ann Arbor, Michigan, February 7, 2007. Docket Identification EPA-HQ-OAR­
 

2004-0008-0516.
 

21. “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-HQ­
 

OAR-2004-0008-0540.
 

22. “Technical Support Document for the Proposed Small Spark Ignition (SI) and Marine SI Emissions Standards: 
 

Ozone Air Quality Modeling,” U.S. Environmental Protection Agency,
 

Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina, EPA-454/R-07-006,
 

November 2006. Docket Identification EPA-HQ-OAR-2004-0008.
 

23. “Air Quality Modeling Exhaust Emission Inputs for the Spark-Ignition Small Nonroad and Marine Engine
 

Proposed Rulemaking,” 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 13, 2007. Docket
 

Identification EPA-HQ-OAR-2004-0008-0559.
 

24. “Air Quality Modeling Evaporative Emission Inputs for the Spark-Ignition Small Engine and Marine Engine
 

Proposed Rulemaking” Memorandum from Michael Samulski to Docket EPA-HQ-OAR-2004-0008, U.S.
 

Environmental Protection Agency, Office of Transportation and Air Quality, Ann Arbor, Michigan, March 8, 2007.
 

Docket Identification EPA-HQ-OAR-2004-0008-0529.
 

3-54 
Emission Inventory 

25. “Development of Air Quality Modeling Emission Inventories for the Small Nonroad and Marine Spark-Ignition 

Engine Proposed Rulemaking,” Memorandum from Harvey Michaels to Docket EPA-HQ-OAR-2004-0008, U.S. 

Environmental Protection Agency, Office of Transportation and Air Quality, Ann Arbor, Michigan, December 11, 

2006. Docket Identification EPA-HQ-OAR-2004-0008-0518. 

26. “Electronic Media Supporting Development of Air Quality Modeling Emissions Inventories for the Small 

Nonroad and Marine Spark-Ignition Engine Proposed Rulemaking,” Memorandum and attachments from Harvey 

Michaels, U.S. Environmental Protection Agency, Office of Transportation and Air Quality, Ann Arbor, Michigan, 

December 11, 2006. Docket Identification EPA-HQ-OAR-2004-0008-0515. 

3-55 

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 

proposed exhaust emission standards are technically achievable accounting for all the above 

factors. 

The proposed 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 new proposed 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 
Draft Regulatory Impact Analysis 

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 

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 it’s 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 highway 

motorcycles, automobiles, trucks and most buses are powered by four-stroke SI engines. Fourstroke 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 it’s 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, 

4-2 
Feasibility of Exhaust Emission Control 

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. 

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 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 

4-3 
Draft Regulatory Impact Analysis 

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 

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 

intentional, such as EGR, or unintentional, such as poor 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 

4-4 
Feasibility of Exhaust Emission Control 

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 

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 

4-5 
Draft Regulatory Impact Analysis 

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 

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 liter 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. 

4-6 
Feasibility of Exhaust Emission Control 

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. 

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 

provides 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. 

4-7 
Draft Regulatory Impact Analysis 

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 

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 cam rails 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 

4-8 
Feasibility of Exhaust Emission Control 

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 

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 

4-9 
Draft Regulatory Impact Analysis 

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 

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 

4-10 
Feasibility of Exhaust Emission Control 

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. 

4.2.4 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 

4-11 
Draft Regulatory Impact Analysis 

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. 

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, 

4-12 
Feasibility of Exhaust Emission Control 

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 

(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 proposal. 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 does 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 a 

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 

4-13 
Draft Regulatory Impact Analysis 

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 

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 

4-14 
Feasibility of Exhaust Emission Control 

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. 

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 

4-15 
Draft Regulatory Impact Analysis 

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 

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. 

4-16 
Feasibility of Exhaust Emission Control 

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 

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. 

4-17 
Draft Regulatory Impact Analysis 

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 

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 

catalyst 

exhaust 

water 

4-18 
Feasibility of Exhaust Emission Control 

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. 

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. 

4-19 
Draft Regulatory Impact Analysis 

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 

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. 

4-20 
Feasibility of Exhaust Emission Control 

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. 

4.2.7 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 

4-21 
Draft Regulatory Impact Analysis 

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 

(or traps). Each of these technologies, which are discussed below, offer 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. 

4-22 
Feasibility of Exhaust Emission Control 

4.3 Feasibility of Small SI Engine Standards 

We are proposing new, more stringent HC+NOx standards for Small SI engines (<19kW) 

used in nonhandheld, terrestrial applications (we are also proposing 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 

have a total displacement of $225cc. We are also proposing 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 present Phase 2 exhaust emission standards for Class I and II small 

spark ignition engines as well as the proposed Phase 3 standards. The proposed standards 

represent a nominal 35-40 percent reduction from current standards. 

Table 4.3-1: Comparison of Phase 2 and Proposed 
 

Phase 3 Standards for Small Spark-Ignition Engines
 

Engine Class 

Current Phase 2 

Standards 

(HC+NOx g/kW-hr) 

Proposed Phase 

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 proposed 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 

proposed standards and conclude with a more in depth assessment of the technical feasibility of 

the proposed requirements for Class I gasoline-fueled engines, Class II single-cylinder gasolinefueled engines, Class II multi-cylinder gasoline-fueled engines, and both classes of gaseousfueled (e.g., liquid propane gas) engines. 

4.3.1 Current Technology and 2005 Certification Test Data 

In the 2005 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 
Draft Regulatory Impact Analysis 

Table 4.3-2: 2005 Engine Sales by Technology Market Mix 

Engine Technology Class I Class II 

Side Valve 60% 2% 

Overhead Valve 40% 98% 

With Catalyst 0.04% 0.2% 

With Other (Electronic Fuel 

Injection and/or water cooled) 

0 2% 

Looking at the industry from an engine family rather than a sales perspective, shows that 

75 and 136 engine families were emission certified in Class I and II, respectively for 2005. The 

range of technology types is shown in Table 4.3-3. The most of engine families in Class I are 

overhead-valve, carbureted engines, with only six families using side-valve, carbureted designs 

(the side-valve engines still account for the bulk of Class I sales). Four families utilized catalytic 

exhaust aftertreatment. 

Table 4.3-2: 2005 Small Spark-Ignition 
 

Engine Technology Types and Number of Engine Families
 

Engine 

Class 

Side-Valve Overhead Valve 

SingleCylinder 

Carburet 

or 

SingleCylinder 

Carburet 

or w. 

Catalyst 

SingleCylinder 

Carburet 

or 

SingleCylinder 

Carburet 

or w. 

Catalyst 

MultiCylinder 

Carburet 

or 

MultiCylinder 

Fuel 

Injection 

MultiCylinder 

Fuel 

Injection 

w. 

Catalyst 

Class I yes (5) yes (1) yes (66) yes (3) no no no 

Class II yes (4) yes (1) yes (67) no yes (58) yes (2) yes (4) 

In Class II, about half of the engine families are overhead-valve, carbureted, 

single-cylinder designs. Based on Table 4.3-2, these families dominate the sales in this class. 

None of these carbureted families used a catalyst. There are several single-cylinder engine 

families using the older, less sophisticated side-valve technology. One of these uses a catalyst. 

Also, about half of this class is comprised of engine families that use multi-cylinder 

(predominately v-twins) designs incorporating overhead-valve technology. Most of these 

multi-cylinder families utilized carburetors, with a few using fuel injection and electronic engine 

controls. Several of these engine families use catalytic aftertreatment. 

Figures 4.3-1 and 4.3-2 present the 2005 certification results at full life for Class I and 2 

4-24 
Feasibility of Exhaust Emission Control 

engine families, respectively, by technology type. In both cases, several engine families were 

certified at levels necessary to comply with the proposed Phase 3 standards. 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 proposed 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 proposed standards. 

4-25 
Draft Regulatory Impact Analysis 

Figure 4.3-1: Class I HC+NOx Full Life Certification Results 

Class I HC+NOx CLs 2005 MY 

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

20 

HC+NOx [g/kW-hr]

SV carb 

OHV carb 

OHV catalyst 

Phase 2 

Phase 3 

100 110 120 130 140 150 160 170 180 190 200
 

Displacement [cc] 

Figure 4.3-2: Class II HC+NOx Full Life Certification Results 

Class II HC+NOx CLs 2005 MY 

0 

5 

10 

15 

20 

25 

0 200 400 600 800 1000 1200 1400 

Displacement [cc] 

H

C

+

NOx [g/kW-hr] 

SV carb 

SV catalyst 

OHV carb 

OHV fuel inj. 

OHV catalyst 

Phase 2 

Phase 3 

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 proposed Phase 3 standards. However, many engine families 

clearly will have to do more to improve emission performance. Generally, we believe the 

proposed 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 

proposed 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 

4-27 
Draft Regulatory Impact Analysis 

more exhaustive 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.1 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 proposed 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-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 1.097 to 1.302 g/kW-hr HC+NOx. 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. 

1

 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. 

4-28 
Table 4.3-4: Class I Test Engine and Control Technology Description 

Engi 

ne 

ID 

Displace 

ment

 (L) 

Valve 

Train 

Fuel 

Meteri 

ng 

Passive 

(Ventu 

ri) 

Second 

ary 

Air? 

Catalyst Type Catalyst 

Volume 

Catalyst 

Cell 

Density 

PGM Loading 

(mass/catalyst 

volume, 

Pt:Pd:Rh ratio) 

236 0.20 Side Carbur 

etor 

Yes Metal monolith 44 cc 200 

cpsi 

30 g/ft3

, 4:0:1 

246 0.20 Side Carbur 

etor 

Yes Metal monolith 44 cc 200 

cpsi 

30 g/ft3

, 4:0:1 

248 0.20 Side Carbur 

etor 

Yes Metal monolith 44 cc 200 

cpsi 

30 g/ft3 

, 

0.33:3.66:1 

249 0.20 Side Carbur 

etor 

Wire-mesh 60 cc N/A proprietary, 

0:0:1 

6820 0.19 Side Carbur 

etor 

Yes Cordierite 

Ceramic 

Monolith 

40 cc 400 

cpsi 

30 g/ft3

, 5:0:1 

258 0.19 Side Carbur 

etor 

Yes Cordierite 

Ceramic 

Monolith 

40 cc 400 

cpsi 

30 g/ft3

, 5:0:1 

241 0.19 Overh 

ead 

Carbur 

etor 

Yes Cordierite 

Ceramic 

Monolith 

40 cc 400 

cpsi 

30 g/ft3

, 5:0:1 

255 0.19 Overh 

ead 

Carbur 

etor 

Yes Coated tube 

pre-catalyst, 

Metal monolith 

main-body 

catalyst 

20 mm dia. 

X 73 mm 

long exhaust 

tubing, 22 cc 

metal 

monolith 

Tube: 2 

channel 

s 

(annular 

shape), 

Main 

body: 

200 

cpsi 

Tube: 

Proprietary 

Main body: 30 

g/ft3

, 3:1:1 

2982 0.19 Overh 

ead 

Carbur 

etor 

Yes Metal monolith 34 cc 100 

cpsi 

50 g/ft3

, 5:0:1 

243 0.16 Overh 

ead 

Carbur 

etor 

Yes Cordierite 

Ceramic 

Monolith 

30 cc 400 

cpsi 

30 g/ft3

, 5:0:1 

244 0.16 Overh 

ead 

Carbur 

etor 

Yes Metal monolith 44 cc 200 

cpsi 

30 g/ft3

, 1:3:1 

245 0.16 Overh 

ead 

Carbur 

etor 

Yes Metal monolith 44 cc 200 

cpsi 

30 g/ft3

, 3:1:1 
Draft 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.2 Our approach also did not explicitly 

account for the fact that manufacturer's 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-time 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 necessary improvement 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 proposed 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; 

2

 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 
Draft Regulatory Impact Analysis 

4. Improving design and manufacturing processes for carburetors to reduce the 

production variability in air-fuel mixtures; and 

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 2005, only 

5 out of 78 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 proposed 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 proposed 

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 proposed 

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 

Displace 

ment 

(L) 

Valve 

Train 

Fuel 

Metering 

Catalyst 

Type 

Catalyst 

Volume 

Catalyst 

Cell 

Density 

Catalyst Loading 

142 0.40 Overhead Carburetor Cordierite 

Ceramic 

Monolith 

250 cc 400 cpsi 40 g/ft3

, 5:0:11 

231 0.50 Overhead Electronic 

Fuel 

Injection 

Metal 

monolith 

280 cc 200 cpsi 70 g/ft3

, 0:5:1 

251 0.50 Overhead Carburetor Cordierite 

Ceramic 

Monolith 

250 cc 400 cpsi 40 g/ft3

, 5:0:1 

253 0.50 Overhead Carburetor Cordierite 

Ceramic 

Monolith 

250 cc 400 cpsi 40 g/ft3

, 5:0:1 

232 0.49 Overhead Electronic 

Fuel 

Injection 

Metal 

monolith 

250 cc 200 cpsi 40 g/ft3

, 5:0:1 

1

 Metal loading expressed as a ratio of platinum:paladium:rodium. 

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. As shown, each of the engines achieved the requisite emission limit of 8 

g/kW-hr HC+NOx. 

4-33 
Draft 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 10-40 1.8 ± 0.42 

Projected High 2.2 

232 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 

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
 

2004 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 proposed 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 proposed 

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 proposed 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 

proposed 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 

4-34 
Feasibility of Exhaust Emission Control 

designs, 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 proposed 8 g/kW-hr HC+NOx standard 

for single-cylinder 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 2005 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 single-cylinder engines, compliance with the proposed 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 

proposed standard and will most likely require only additional fuel-air mixture and injection 

timing calibration changes for compliance. 

4-35 
Draft 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 

Cataly 

st 

Volu 

me 

Cataly 

st Cell 

Densit 

y 

Catalys 

t 

Loadin 

g 

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 60 

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:paladium:rodium.
 

Finally, the combination of electronic fuel injection and catalytic exhaust aftertreatment 

clearly has the potential to reduce emission well below the proposed 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 proposed 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 

4-36 
Feasibility of Exhaust Emission Control 

management system. 

We expect some engine families will use electronic fuel injection to meet the proposed 

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 proposed 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 

proposed 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 smalldisplacement motorcycles. The sensors for the system were minimized to included 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 with 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.4546 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 2005 Certification Database lists 8 multi-cylinder engine families in the Class II 500 useful 

life category as having catalysts. Due to this fact, it is assumed that gaseous engines do not have 

4-37 
Draft Regulatory Impact Analysis 

the same concerns with multi-cylinder engines and catalysts as gasoline engines. 

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 proposing 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 2004 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 proposed 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, twostroke direct injection engines and four-stroke engines easily meet the 2006 standard. 

4-38 
Feasibility of Exhaust Emission Control 

Figure 4.4-1: 2006 MY Outboard HC+NOx Certification Levels 

0 

50 

100 

150 

200 

250 

300 

350 

400 

0 50 100 150 200 

Rated Power [kW] 

HC+NO

x [g/kW-hr] 

2s Carb 

2s DI 

4s Carb 

4s EFI 

Baseline 

EPA 2006 

Proposed 

Figure 4.4-2: 2006 MY New Technology Outboard HC+NOx Certification Levels 

0 

5 

10 

15 

20 

25 

30 

35 

40 

45 

50 

0 50 100 150 200 

Rated Power [kW] 

HC

+

N

O

x [

g/kW-hr] 

2s Carb 

2s DI 

4s Carb 

4s EFI 

Baseline 

EPA 2006 

Proposed 

4-39 
Draft Regulatory Impact Analysis 

Figures 4.4-3 and 4.4-4 present similar data for personal watercraft engines. These 

engines 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 proposed 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] 

H

C+N

O

x [

g/kW-hr] 

2s Carb 

2s DI 

2s Catalyst 

4s EFI 

Baseline 

EPA 2006 

Proposed 

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+NO

x [g/kW-hr] 

2s Carb 

2s DI 

2s Catalyst 

4s EFI 

Baseline 

EPA 2006 

Proposed 

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 

700 

800 

0 50 100 150 200 

Rated Power [kW] 

C

O [

g/kW-hr]

2s Carb 

2s DI 

4s Carb 

4s EFI 

proposed 

Figure 4.4-6: Reported CO Emission Levels for 2006 MY PWC Engines 

0 

100 

200 

300 

400 

500 

600 

0 50 100 150 200 

Rated Power [kW] 

C

O [

g/kW-hr]

2s Carb 

2s DI 

2s Catalyst 

4s EFI 

Proposed 

4-41 
Draft 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/kW-hr 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). We are not 

aware of any efforts to develop a three-way 

catalyst system for PWC engines. 

We are also not aware of any development 

efforts to package a catalyst into the exhaust system of an outboard marine engine. 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 

4-43 
Draft Regulatory Impact Analysis 

We are proposing exhaust emission standards for spark-ignition sterndrive and inboard 

(SD/I) engines. These proposed emission standards are supported by data collected on SD/I 

engines 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, throttlebody 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 on five highperformance engines.55,56,57 

4-45 
Draft Regulatory Impact Analysis
 

Table 4.5-2: Baseline High Performance SD/I Exhaust Emission Data [g/kW-hr]
 

Engine # Power 

[kW] 

Fuel Delivery System HC NOx CO BSFC 

1 391 multi-port electronic fuel injection 14.7 3.8 243 354 

2 550 carburetor 13.2* 8.4 253 376 

3 634 multi-port electronic fuel injection, 

supercharger 

16.9 9.1 135 348 

4 778 throttle-body fuel-injection, supercharger, 

intercooler 

7.6 4.9 349 448 

5 802 multi-port electronic fuel injection, 

supercharger 

16.1 9.4 102 299 

* may be higher, HC concentration at idle was out of measurement range 

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).58,59,60 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 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.61 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 
Draft 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 combined 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 an 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. 

4-49 
Draft Regulatory Impact Analysis 

To that end, ARB, industry and the U.S. Coast Guard recently performed a cooperative 

in-boat demonstration program designed to demonstrate the feasibility of using catalysts in SD/I 

applications.62,63 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.64 No significant deterioration was observed on any of the catalysts. In fact, all of the 5.7 

L engines were below the proposed 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 

proposed HC+NOx standard, the final emissions for the 4.3 L engine were 15 percent above the 

proposed 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.65 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 

4-51 
Draft Regulatory Impact Analysis 

above the dew 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. 

4-52 
Feasibility of Exhaust Emission Control 

These manifolds were rebuilt with guidance from experts in the marine industry and additional 

hours were 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 

To date, one manufacturer is selling inboard Marine SI engines equipped with catalysts. 

These engines are certified in California and 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.66 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 

Other marine engine manufacturers have indicated that they will produce catalystequipped SD/I engines, certified to the California emission standards, by the end of this year. 

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 

4-53 
Draft Regulatory Impact Analysis 

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 engine 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 proposed 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 proposed 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 speeds67 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 mode 1 for these engines. Although mode 1 is only weighted as 6 percent of 

the proposed 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. 

4-54 
Feasibility of Exhaust Emission Control 

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 

C

O [

g/k

W-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 

liquid-cooled 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.68 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.69,70 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 

marine generator product lines over to low CO engines.71,72 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 

4-55 
Draft Regulatory Impact Analysis 

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.

73 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 proposing 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 are proposing to include SD/I 

engines in these test procedures. In addition we are proposing 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 proposing to use the same certification duty cycle and test procedures for all 

Marine SI engines, including sterndrives and inboards. Table 4.5-6 presents the proposed 

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.74 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.75 Although some Marine SI 

engines may be used for commercial activities, these engines would not likely be made or used 

differently than those used for pleasure. 

4-56 
Feasibility of Exhaust Emission Control 

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 Power* 

at MES 

Weighting 

Factor 

1 

2 

3 

4 

5 

100 

80 

60 

40 

idle 

100 

71.6 

46.5 

25.0 

0 

100 

57.2 

27.9 

10.1 

0 

0.06 

0.14 

0.15 

0.25 

0.40 

*% power = (% speed) × (% torque). 

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 are proposing requirements that extend to typical in-use 

operation. We are proposing 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-to-exceed 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 

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 

4-57 
Draft Regulatory Impact Analysis 

of operation and should not require additional technology beyond what is used to meet the 

proposed 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 steadystate 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 proposed 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 proposed 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.76 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.77 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 proposed 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 brakespecific 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. 

4-58 
Feasibility of Exhaust Emission Control 

Figure 4.7-1: Proposed NTE Zone and Marine Engine Operation Data 

1.2 

Torque MAP 

1 

100% Speed 0.8 

1.5 x Speed - 0.16 Outboard 

0.6 PWC 

Inboard 

Sterndrive 

0.4 SAE 901596 

E4 Setpoints 

40% Speed Prop Curve 

Speed^1.5 - 0.08 Torque Curve 

0.2 

25.3% Torque Draft NTE 

Zone 

Atypical Points 

0 

0% 20% 40% 60% 80% 100% 120% 

Normalized Speed 

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 proposed 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 proposed NTE zone would be steady-state. 

When bringing a boat to plane, marine engine operation would be transient and would likely be 

above the proposed 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 

4.7.2.2 Emissions Limits for the NTE Zone 

We are proposing emission caps for the NTE zone 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 

N

ormalized Torque 

4-59 
Draft Regulatory Impact Analysis 

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 proposed 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,78,79,80 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.81,82,83,84 Our analysis focuses only on engines using technology that could be used to 

meet the proposed 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 an emissions performance, data is presented separately for carbureted 4-stroke, fuelinjected 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 

1 

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 

2 3 4 

Normalized Speed, Torque [% of rated] 

N

ormalized H

C

+

N

Ox [

M

o

dal/

E4] 

40%, 25% 60%, 47% 80%, 72% 100%, 100% 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

2 3 4 

Normalized Speed, Torque [% of rated] 

N

ormali

zed CO [M

o

dal/E

4] 

40%, 25% 60%, 47% 80%, 72% 100%, 100% 

Figure 4.7-3: Normalized Modal CO for Carbureted 4-Stroke OB/PWC 

4-61
 
Draft 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 

Norm

aliz

e

d HC+NOx [M

o

d

al/E

4] 

40%1, 25% 2 3 

Normalized Speed, Torque [% of rated] 

 60%, 47% 80%, 72% 100%, 4100% 

Figure 4.7-5: Normalized Modal CO for EFI 4-Stroke OB/PWC 

2.5 

2.0 

1.5 

N

ormalized C

O [

M

o

d

al/E

4] 1.0 

0.5 

0.0 

40%1, 25% 2 3 

Normalized Speed, Torque [% of rated] 

 60%, 47% 80%, 72% 100%4, 100% 

4-62 
1 

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 mid-speed 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 

2 3 4 

Normalized Speed, Torque [% of rated] 

Norm

aliz

e

d HC+NOx [M

o

d

al/E

4] 

40%, 25% 60%, 47% 80%, 72% 100%, 100% 

4-63 
1 

1 

Draft Regulatory Impact Analysis 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

2 3 4 

Normalized Speed, Torque [% of rated] 

N

ormalized CO [M

o

dal/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 

2 3 4 

Normalized Speed, Torque [% of rated] 

Norm

aliz

e

d HC+NOx [M

o

d

al/E

4] 

40%, 25% 60%, 47% 80%, 72% 100%, 100% 

4-64
 
1 

Feasibility of Exhaust Emission Control 

Figure 4.7-9: Normalized Modal CO for Type 2 DI 2-Stroke OB/PWC 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

2 3 4 

Normalized Speed, Torque [% of rated] 

N

ormalized CO [M

o

dal/E4] 

40%, 25% 60%, 47% 80%, 72% 100%, 100% 

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 proposed NTE zone.85 This engine was tested in 

its baseline configuration (open-loop 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 

proposed 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 

1 

Draft Regulatory Impact Analysis 

Figure 4.7-10: Normalized Modal HC+NOx for SD/I with Catalysts 

0.0 

0.2 

0.4 

0.6 

0.8 

1.0 

1.2 

1.4 

1.6 

2 3 4 5 6 7 

Normalized Speed, Torque [% of rated] 

N

orm

aliz

e

d H

C

+

N

O

x [

Modal/E

4] 

40%, 25% 50%, 35% 60%, 47% 70%, 59% 80%, 72% 90%, 85% 100%, 100% 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

2 3 4 5 6 7 

Normalized Speed, Torque [% of rated] 

N

ormalized CO [M

o

dal/E4] 

40%, 25% 50%, 35% 60%, 47% 70%, 59% 80%, 72% 90%, 85% 100%, 100% 

Figure 4.7-11: Normalized Modal CO for SD/I with Catalysts 

4-66
 
Feasibility of Exhaust Emission Control 

Based on the above data, we believe that a single NTE limit is not appropriate for the 

entire NTE zone. For this reason, we are proposing to divide the NTE zone into four subzones. 

These subzones are numbered to correspond with the E4 mode that they contain. For instance, 

subzone 1 includes full-power operation which is mode 1 in the E4 duty cycle. Subzone one is 

all operation at or above 90 percent maximum test speed and/or 100 percent torque at maximum 

test speed. Mode 2 is (operation below subzone 1) at or above 70 percent maximum test speed 

and/or 80 percent torque at maximum test speed. Subzone 4 includes operation in the proposed 

NTE zone at or below 50 percent speed. Subzone 3 includes the remaining section of the 

proposed NTE zone. Figure 4.7-12 presents the proposed NTE zone and subzones. 

Figure 4.7-12: Proposed NTE Zone and Subzones 

0% 

20% 

40% 

60% 

80% 

100% 

120% 

0% 20% 40% 60% 80% 100% 120% 

Normalized Speed 

N

ormalized T

orq

ue 

2 

1.5 x Speed - 0.16 

Speed^1.5 - 0.08 

Torque MAP 

100% Speed 

40% Speed 

25.3% Torque 

90% Speed 

70% Speed 

Speed^1.5 (theoretical propeller curve) 

3 

1 

E4 Modes 

4 

50% Speed 

The data presented above suggests that separate NTE limits may be necessary for 

HC+NOx and for CO. Also this data suggests that different NTE limits by be appropriate for 

different engine types (especially catalyzed SD/I versus OB/PWC). We are proposing separate 

NTE limits for SD/I and OB/PWC. These limits are presented in Table 4.7-2. In addition, due 

to the wide variability of modal emission rates for the two types of direct-injected two-stroke 

engines, we are proposing two alternative sets of NTE limits than manufacturers would have the 

option of choosing for their OB/PWC engines. These alternative limits are based on the data 

presented above and give more room in some subzones while imposing tighter caps in other 

4-67 
Draft Regulatory Impact Analysis 

subzones to give a net stringency roughly equivalent to the primary option. To offset these 

relaxed standards in subzones 1 and 4, we are proposing more stringent limits in subzones 2 and 

3 for this alternative approach. 

Table 4.7-2: Proposed NTE Limits by Subzone 

Application Pollutant Subzone 4 Subzone 3 Subzone 2 Subzone 1 

SD/I HC+NOx 

CO 

1.5 

1.0 

1.0 

1.0 

1.0 

1.0 

1.5 

3.5 

OB/PWC 

(primary) 

HC+NOx 

CO 

1.6 

1.5 

1.2 

1.5 

1.2 

1.5 

1.2 

1.5 

OB/PWC 

(alternative 1) 

HC+NOx 

CO 

2.0 

1.0 

0.8 

1.0 

0.8 

1.5 

2.0 

3.0 

OB/PWC 

(alternative 2) 

HC+NOx 

CO 

3.0 

2.0 

1.0 

1.0 

1.0 

1.0 

1.0 

1.5 

We used the modal data presented above and the data on additional operation points 

presented in Appendix 4A to develop these NTE limits. The proposed 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 proposed NTE limits, we believe that these 

engines can be calibrated to meet these proposed limits. In addition, the limits are based on the 

Family Emission Limits 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 proposed NTE limits. 

4.7.2.3 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 are proposing to apply 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.86 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 

4-68 
Feasibility of Exhaust Emission Control 

directly from the outdoor ambient. 

For NTE testing in which the air temperature or humidity is outside the proposed range, 

we propose 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 proposing that the NTE testing include a range of ambient water 

temperatures from 5 to 27°C (41 to 80°F). The proposed 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 proposed emission 

standards for nonroad spark-ignition engines under 50 horsepower. As further detailed in the 

following sections, we expect that the proposed 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 proposing new exhaust standards.87 These areas 

are: 

- New catalyst-based HC+NOx exhaust emission standards for Class I and II 

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. 

4-69 
Draft Regulatory Impact Analysis 

4.8.1.1 Exhaust Emission Standards for Small Spark-Ignition Engines 

The technology approaches that we assessed for achieving the proposed 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 

proposed 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;
 

- 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. 

4-70 
Feasibility of Exhaust Emission Control 

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).88 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 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 

4-71 
Draft Regulatory Impact Analysis 

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 steadystate 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. 

4-72 
Feasibility of Exhaust Emission Control 

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. 

4-73 
Draft Regulatory Impact Analysis 

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. 

4-74 
Feasibility of Exhaust Emission Control 

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. Peak Surface Temperature (°C) Peak Surface Temperature (°C) k Surface Temperature (°C)

400

380

360

340

320

300

280

260

240

220

200

180

160

140

120

100

80

60

40

20

0

253 w/Catalyst

251 w/OEM Muffler

254 w/Catalyst

256 w/OEM Muffler

2 -

minutes

0:001:002:003:004:005:006:007:008:00

Time (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 proposed 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 in-use. Based on the applicability of Coast Guard and ABYC 

4-75 
Draft Regulatory Impact Analysis 

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 proposed 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 proposed standard. 

The conversion of some carbureted Small SI engines to fuel injection technologies is also 

expected to improve fuel economy. We estimate approximately 18 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 56 million gallons 

of gasoline in 2030 when all of the Class II engines used in the U.S. will comply with the 

proposed 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. 

4-76 
Feasibility of Exhaust Emission Control 

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% 

N

orm

aliz

e

d T

orq

ue 

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% 

N

orm

alized Torque 

4-77 
Draft Regulatory Impact Analysis 

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 

N

orm

aliz

e

d T

orq

ue 

Figure 4A-4: CO Ratios for 7.4L MPI Engine, Riser Catalysts 

140% 

N

orm

aliz

e

d T

orq

ue 

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 

4-78 
Feasibility of Exhaust Emission Control 

Figure 4A-5: HC+NOx Ratios for 7.4L MPI Engine, Elbow Catalysts 

N

orm

aliz

e

d T

orq

ue 

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 

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 

4-79 

N

orm

aliz

e

d T

orq

ue 
Draft Regulatory Impact Analysis 

Figure 4A-7: HC+NOx Ratios for 7.4L MPI Engine, External Catalysts 

N

orm

aliz

e

d T

orq

ue 

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 

N

orm

aliz

e

d T

orq

ue 

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 

4-80 
Feasibility of Exhaust Emission Control 

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. 

4-81 
Draft Regulatory Impact Analysis 

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. 

4-82 
Feasibility of Exhaust Emission Control 

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. 

4-83 
Draft Regulatory Impact Analysis 

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. “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. 

59. “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. 

60. “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. 

61. “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. 

62. “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. 

63. “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. 

4-84 
Feasibility of Exhaust Emission Control 

64. “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. 

65. “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. 

66. 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. 

67. 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. 

68. 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. 

69. “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. 

70. “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. 

71. “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. 

72. “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. 

73. 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. 

74. “Duty Cycle for Recreational Marine Engines,” Morgan, E., Lincoln, R., SAE Paper 901596, 1990, Docket 

Identification EPA-HQ-OAR-2004-0008-0216. 

75. “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. 

76. Morgan, E., Lincoln, R., “Duty Cycle for Recreational Marine Engines,” SAE Paper 901596, 1990, Docket 

Identification EPA-HQ-OAR-2004-0008-0216. 

77. 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. 

78. 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. 

4-85 
Draft Regulatory Impact Analysis 

79. 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. 

80. Klak, Joe, “Marine NTE Zones,” Bombardier Recreational Products, October 26, 2006, Docket Identification 

EPA-HQ-OAR-2004-0008-0508. 

81. “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. 

82. “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. 

83. “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. 

84. “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. 

85. “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. 

86. 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. 

87. “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. 

88. “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. 

4-86 
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 

proposed evaporative emission standards are technically achievable accounting for all the above 

factors. 

The proposed 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 proposed 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 
Draft Regulatory Impact Analysis 

5.1 Diurnal Breathing Loss Evaporative 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 would be about 4.5 psi. In this example, the partial 

pressure of the air would be 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 would be 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 would be 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 would 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 proposed 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 
Draft 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 
Draft 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 largely been a permeation effect. 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 

trace of the fuel. 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 

ambient air. To investigate this effect, we tested several boats by recording the ambient air 

5-6 
Feasibility of Evaporative Emission Control 

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 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. 

Table 5.1-6 also presents an estimate of the effect on diurnal emissions using the theoretical 

5-7 
Draft Regulatory Impact Analysis 

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 Δ C

Flux = = D × 

area × time Δ 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 
Draft 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 
Draft 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 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 
Draft 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 
Draft 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 some open sites 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 has initiated a test program has to 

demonstrate the durability of carbon canisters in marine applications. This test program includes 

installing carbon canisters on a total of fourteen boats made by four boat builders.24 These boat 

types include 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 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 good performance.25 These canisters will be evaluated further, including destructive 

testing. 

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. 

Recently, the California Air Resources Board (ARB) performed similar testing on a 

commercial mower and a generator with 6 gallon fuel tanks and 0.65 liter canisters.27 Their 

5-17 
Draft Regulatory Impact Analysis 

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.28 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.29 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. 

5.1.5 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 

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. 

5-18 
Feasibility of Evaporative Emission Control 

Yacht Council makes the additional recommendation that the vent line should have a minimum 

inner diameter of 7/16 inch.30 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 proposed 

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 

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 

5-19 
Draft Regulatory Impact Analysis 

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 5.1-1, there was a fairly linear relationship between the pressure 

setting of the valve and the emissions measured over the proposed 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. 

Figure 5.1-1: Effect of Pressure Cap on Diurnal Emissions 

H

C [

g/g

al/da

y] 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 

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.31 

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 

5-20 
Feasibility of Evaporative Emission Control 

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. 

5.1.5.2 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 

5-21 
Draft Regulatory Impact Analysis 

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, 

then the operator would not need to operate the sealing mechanism. It would always control 

diurnal (and other breathing loss) 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.32 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.33 One of these uses is to act as a vapor processor to prevent hydrocarbon 

vapor from escaping from retail gasoline stations in California.34 Another membrane used for 

similar applications allows hydrocarbons to permeate but blocks smaller gases. This membrane 

is used in hydrocarbon recovery applications.35 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 

5-22 
Feasibility of Evaporative Emission Control 

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 proposed 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. 

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.36 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 

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. 

5-23 
Draft Regulatory Impact Analysis 

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. 

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.37 

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.38 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. 

5-24 
Feasibility of Evaporative Emission Control 

5.1.10 Liquid Vapor Trap 

One company has developed a Figure 5.1-2: Liquid Vapor Trap 

liquid vapor trap that it refers to as a 

fuel vapor containment system (VCS).39 

The VCS behaves similar to a liquid 

trap used in sink drains in that trapped 

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 5.1-2 

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.40 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.41 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. 

fuel tank A B 

vent 

VCS 

5-25 
Draft Regulatory Impact Analysis 

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. 

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.42 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.43 

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. 

5-26 
Feasibility of Evaporative Emission Control 

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.44 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 

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. 

5-27 
Draft Regulatory Impact Analysis 

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 

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. 

5-28 
Feasibility of Evaporative Emission Control 

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 

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. 

5-29 
Draft Regulatory Impact Analysis 

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 

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.45 

5-30 
Feasibility of Evaporative Emission Control 

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.46 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’ relationship47 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 

included in our docket.48,49,50,51,52 Table 5.3-3 presents a summary of this data which was 

collected using the ARB Test Method 513.53 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. 

5-31 
Draft Regulatory Impact Analysis 

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 
Draft 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 proposed 

standards using their current materials. In the cases where the permeation rates were higher than 

the proposed 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 5.3-4 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 5.3-4: 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 

(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 

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.54,55 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 513.56 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. 

5-34 
Feasibility of Evaporative Emission Control 

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.57 

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. 

5-35 
Draft Regulatory Impact Analysis 

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 untreated 11.5 17.1 92% 

B 11.4 16.6 86% 

C 11.2 17.0 97% 

D sulfonated 2.48 4.10 127% 

E 2.73 3.98 85% 

F 2.24 3.42 100% 

H fluorinated 0.56 0.75 60% 

I 0.62 0.68 17% 

J 0.22 0.31 80% 

Published data collected on HDPE samples at four temperatures58,59 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 

Data on HDPE samples 

80% increase in permeation per 

10 C increase in temperature 

0 10 20 30 40 50 60 70 

degrees Celsius 

Another study was performed on the permeation from complete automotive fuel 

systems.60 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). 

5-36 
Feasibility of Evaporative Emission Control 

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 

5-37 
Draft Regulatory Impact Analysis 

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] 

insi

d

e surface area [

m2] 

0.00 

0.05 

0.10 

0.15 

0.20 

0.0 0.5 1.0 

volume [gallons] 

insi

d

e 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.61,62,63,64 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

5-38 
Feasibility of Evaporative Emission Control 

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.65 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.66 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 

5-39 
Draft Regulatory Impact Analysis 

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.67 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.68 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 

5-40 
Feasibility of Evaporative Emission Control 

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 

5-41 
Draft Regulatory Impact Analysis 

percent from new tanks.69 

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 proposed 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. 

5-42 
Feasibility of Evaporative Emission Control 

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 proposed 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 proposed durability testing requirements. 

The California Air Resources Board (ARB) collected test data on permeation rates from 

sulfonated portable fuel containers using California certification fuel.70 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. 

5-43 
Draft Regulatory Impact Analysis 

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 

5-44 
Feasibility of Evaporative Emission Control 

largely resolved.71 

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.72,73 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.74 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°C75 which was less than half of what the CARB testing showed on their constant temperature 

test at 40°C.76 A list of resins and additives that are compatible with the sulfonation process is 

included in the docket.77,78 

5-45 
Draft Regulatory Impact Analysis 

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. 

5-46 
Feasibility of Evaporative Emission Control 

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.79 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 

5-47 
Draft Regulatory Impact Analysis 

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.80 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. 

5-48 
Feasibility of Evaporative Emission Control 

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 proposed 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 proposed durability testing requirements. 

The California Air Resources Board (ARB) collected test data on permeation rates from 

fluorinated fuel containers using California certification fuel.81,82 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.83 

The ARB data is presented in Table 5.3-18. 

5-49 
Draft Regulatory Impact Analysis 

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.84 

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.85,86 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 

5-50 
Feasibility of Evaporative Emission Control 

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 5.3-19 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 5.3-19: 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 5.3-20 presents this comparison. 

5-51 
Draft Regulatory Impact Analysis 

Table 5.3-20: 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 

Temperat 

ure 

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 proposed standard. 

Table 5.3-21: 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% 

Another study also looked at the effect of alcohol in the fuel on permeation rates from 

fluorinated fuel tanks.87 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 

5-52 
Feasibility of Evaporative Emission Control 

manufacturers with low emission products. As of August, 2006, ARB has issued 5 executive 

orders for low permeation fuel tanks.88 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 

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.89 

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.90 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 proposed Federal test procedure.91 

Under this testing, E10 fuel was used. Weight loss tests were performed before and after the 

durability tests in 40 CFR 1501.515.92 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 proposed fuel tank 

permeation standard on E10 after the durability testing. 

5-53 
Draft Regulatory Impact Analysis
 

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 

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 

5-54 
Feasibility of Evaporative Emission Control 

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 proposed 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 

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 proposed permeation standard. 

5-55 
Draft Regulatory Impact Analysis 

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 

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. 

5-56 
Feasibility of Evaporative Emission Control 

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.93 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®. 

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% 

5-57 
Draft Regulatory Impact Analysis 

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 proposed 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.94 

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 

E10 than on gasoline for these fuel tanks. Note these fuel tanks are capable of meeting the 

proposed 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 O-rings, which were not made of low permeation materials. Emissions could likely 

be reduced significantly from these tanks with improved seal designs. Table 5.3-28 presents the 

results of this testing. 

5-58 
Feasibility of Evaporative Emission Control 

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.95 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 

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.96 

5-59 
Draft Regulatory Impact Analysis 

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.97 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.98 

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 

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 

5-60 
Feasibility of Evaporative Emission Control 

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.99 

Another study looks at the permeation rates, using ARB test procedures, through multilayer fuel tanks.100 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% 

The California Air Resources Board tested two sets of three 5-gallon portable fuel 

containers.101 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 

4 Chemically modified montmorillonite for nanocomposite formulation 

5-61 
Draft Regulatory Impact Analysis 

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 

Another approach has recently been developed in which a multi-layer fuel tank can be 

blow-molded with only two layers.102 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. 

5.3.2.5.2 Rotational Molded Dual-layer Construction 

As discussed above, an inner layer can be molded into the inside of a rotationally molded 

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. 

5-62 
Feasibility of Evaporative Emission Control 

One manufacturer is working with a nylon known as Rilsan® polyamide 11 (PA 11) in 

constructing low permeation multi-layer rotational-molded fuel tanks.103 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.104 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 5.3-31. The 

manufacturer reported that this tank design passed testing on the Coast Guard burn, pressure, 

shock, and impulse test requirements.105,106,107,108 In addition, a tank of this construction was 

tested and passed the tank durability tests for snowmobiles specified in SAE J288.109 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. 

Table 5.3-31: 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.110 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 5.3-32 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. 

5-63 
Draft Regulatory Impact Analysis 

Table 5.3-32: 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.111 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.112 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.113 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. 

5.3.2.5.4 Thermoformed Multi-Layer Construction 

As an alternative, multiple layers can be created through thermoforming.114 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 

5-64 
Feasibility of Evaporative Emission Control 

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 5.3-33 presents the test 

results for each of the three tests. 

Table 5.3-33: 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 

5-65 
Draft Regulatory Impact Analysis 

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 5.3-34, show that this technology can be used to reduce 

permeation emissions by more than 90 percent. 

Table 5.3-34: 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.115 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 5.3-35 presents the test results after a 9 

week fuel soak at 40°C. 

5-66 
Feasibility of Evaporative Emission Control 

Table 5.3-35: 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 

minutes). With the intumescent coating, the fuel tank passed the flame test and survived more 

than 5 minutes.116 

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 J1527.117 Fuel hose for boats with 

gasoline engines (excluding outboards) must meet the Class 1, Type A requirements which 

5-67 
Draft Regulatory Impact Analysis 

specify a maximum permeation rate of 100 g/m2/day at 23°C on ASTM Reference Fuel C118 (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 

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.119 

We collected test data on marine hose permeation through contracts with outside 

laboratories.120,121,122,123,124 Data was also available on a fuel feed hose testing funded by the 

marine industry.125 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. 

5-68 
Feasibility of Evaporative Emission Control 

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 J2046.126 Under this practice, the 

permeation requirement is 300 g/m2/day with testing performed in accordance with SAE J1527. 

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.127 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. 

5-69 
Draft Regulatory Impact Analysis
 

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°C128 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.129 

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. 

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 

5-70 
Feasibility of Evaporative Emission Control 

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.130 In this modified procedure, E10 fuel was used and the testing followed a 30 day 

fuel soak intended to stabilize the permeation rate. Table 5.4-4 presents the test results. 

Table 5.4-4: Handheld Product Fuel Line Permeation Test Data [E10 fuel at 23/C] 

Hose Identification Construction Material g/m2/day 

90014 

90015 

90016 

S3 

S4 

H1 

H2 

extruded NBR 

NBR 

NBR 

NBR 

NBR 

NBR 

NBR 

198 

192 

168 

165 

171 

360 

455 

S1 

S2 

injection-molded NBR 

NBR/PVC 

198 

386 

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.131 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. 

5-71 
Draft Regulatory Impact Analysis
 

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.132 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. 

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 

5-72 
Feasibility of Evaporative Emission Control 

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.133,134 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 

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.135 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 

5-73 
Draft Regulatory Impact Analysis 

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 

5.4.1.6 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.136 

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 

5-74 
Feasibility of Evaporative Emission Control 

the hose.137 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. 

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.138 All of the testing was performed 

on 3 foot sections of 1.5" I.D. marine fill neck 

hose. Testing was performed in each of the 

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 

tests, the hose was soaked with liquid fuel for 

Liquid 

Vertical 

Horizontal 

5-75 
Draft Regulatory Impact Analysis 

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 

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.139 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 

5-76 
Feasibility of Evaporative Emission Control 

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 

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.140 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.141 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.142 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.143,144 

5-77 
Draft Regulatory Impact Analysis 

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. 

We are proposing 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 hose145 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.146 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). 

5 THV = tetrafluoroethylene hexafluoropropylene, ECO = epichlorohydrin/ethylene oxide 

5-78 
Feasibility of Evaporative Emission Control 

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 

proposed hose permeation standard on E10 fuel. Although hose using THV 800 is available, it is 

produced for automobiles that will need to meet the tighter evaporative emission requirements in 

the upcoming Tier 2 standards. Hose produced in mass quantities today uses THV 500. This 

hose is less expensive and could be used to meet the proposed 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.147 In addition, this data shows that permeation rates 

more than double when tested on CE10 versus Fuel C. 

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.148,149,150,151,152,153 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.154 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. 

5-79 
Draft Regulatory Impact Analysis
 

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.155 

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 

5-80 
Feasibility of Evaporative Emission Control 

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 was available 

prior to our initial 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.156,157,158,159,160,161 

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.162 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.163 

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 proposed 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 

5-81 
Draft Regulatory Impact Analysis 

After the initial 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.164 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).165 This particular fuel line construction also uses 

Teflon® as a barrier layer. Table 5.4-19 presents permeation test data on this hose.166 

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 

proposed fuel line permeation standard. Alternatively, primer bulbs could be manufactured to 

5-82 
Feasibility of Evaporative Emission Control 

meet the proposed standards by molding a fluoroelastomer inner liner with a nitrile shell to 

reduce costs. Other materials may be applicable as well (see tables of material properties in 

Appendix 5D). 

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.167 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. 

5-83 
Draft Regulatory Impact Analysis 

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.168 Examples of such equipment are ice augers and chainsaws. 

5-84 
Feasibility of Evaporative Emission Control 

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.169,170 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.171,172 For 

instance, low temperature o-rings are common in automotive applications.173,174,175 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.176 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.177 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.178 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 proposed 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 

5-85 
Draft Regulatory Impact Analysis 

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.179,180 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.181 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 

5-86 
Feasibility of Evaporative Emission Control 

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.182 

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.183 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 

5-87 
Draft Regulatory Impact Analysis 

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 would be 

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 would give 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.184 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.185 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.186 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 Hose Permeation Testing 

We propose for hose permeation to be measured at a temperature of 23 ± 2°C using the 

weight loss method specified in SAE J30.187 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 any air 

bubbles have been removed from the hose, 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. 

5-88 
Feasibility of Evaporative Emission Control 

We are proposing 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 C188 (50 percent toluene, 50 percent iso-octane) blended with 10 percent ethanol. 

This fuel is known as CE10 and is commonly used in industry standards and test procedures such 

as in SAE recommended practices. 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 

proposing a soak period of 4 weeks at 23 ± 5°C. If a longer time period is necessary to achieve a 

stabilized permeation rate for a given hose design, we would expect the manufacturer to use a 

longer soak period (and/or higher temperature) consistent with good engineering judgement. For 

instance, thick-walled marine fuel hose may take longer to reach a stable permeation rate than 

thinner-walled hose used in Small SI applications. 

Alternatively, for purposes of submission of data at certification, permeation could be 

measured using alternative equipment and procedures that provide equivalent results. To use 

these alternative methods, manufacturers would have to apply to us and demonstrate 

equivalence. Examples of alternative approaches that we anticipate manufacturers may use are 

the recirculation technique described in SAE J1737,189 enclosure-type testing such as in 40 CFR 

part 86, or weight loss testing such as described in SAE J1527.190 

Coast Guard standards for marine fuel hoses (33 CFR part 183) cite SAE recommended 

practice J1527191 which, among other things, includes test procedures for measuring permeation 

from marine fuel hoses. In this test procedure, a short section of hose is attached to a 

nonpermeable container (i.e. metal fuel can) and plugged. Fuel is added to the container and the 

mass of the entire unit is measured every 24 hours for 15 days and the peak fuel loss is 

determined. This testing is performed at 23 ± 2°C on both reference fuel “C” for the version of 

the SAE standard referenced in 33 CFR part 183. However, SAE J1527 was revised in 1993 to 

include permeation standards for hoses tested on a fuel blend with 15 percent methanol. This 

test procedure is simple; however, it is sufficient for marine hoses because they have high 

permeation rates ranging from 100 to 600 g/m2

/day depending on the hose class and the fuel 

used. 

Recommended practice for automotive fuel tubing is defined in SAE J2260.192 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 

5-89 
Draft Regulatory Impact Analysis 

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 J1737.193 

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 

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 proposing to apply a 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 proposed 

differences in the test procedure compared to recreational vehicles are minor and are intended to 

simplify the testing. For instance, the durability testing would be 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 

compared to the recreational vehicle test which includes the calculation of a deterioration factor. 

5-90 
Feasibility of Evaporative Emission Control 

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 

5-91 
Draft Regulatory Impact Analysis 

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) would 

be 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 proposed slosh test, would be acceptable. 

To determine a permeation emission deterioration factor, we are proposing 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 pressurevacuum 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.194 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. For example, a fuel tank that is only used in vehicles where an outer shell prevents the 

tank from being exposed to sunlight may not benefit from UV testing. 

5-92 
Feasibility of Evaporative Emission Control 

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 would be 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 30 percent of fuel sold in the U.S. contains ethanol and 

this percentage is expected to increase to about 45-50 percent in 2012 and later. We are 

proposing the use of 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 are proposing that ASTM Fuel C blended with 10 percent ethanol (Fuel CE10) 

may be used. 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.195 

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 196,197,198,199 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. 

5-93 
Draft Regulatory Impact Analysis 

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 90* 69* -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 ** 7.5 

8.5 

minimal 

*ASTM Fuel C was used as gasoline (50% toluene, 50% isooctane). Units are per mm of 

thickness 

** 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 proposing E10 as a test fuel to ensure that the 

proposed permeation standard will be met on in-use fuels. 

A recent study found that permeation from automotive fuel systems increased 

significantly when gasoline containing ethanol was used compared to gasoline without 

ethanol.200 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. The highest effect of ethanol in gasoline on permeation probably occurs when 10­

30 percent ethanol is blended into the gasoline. We are just beginning a contract for testing to 

study permeation rates at various ethanol fuel blends as part of our on-highway inventory 

modeling efforts. 

5-94 
Feasibility of Evaporative Emission Control 

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 

proposed 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. 

5-95 
Draft Regulatory Impact Analysis 

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 

W

eight L

o

ss [gra

m

s] 

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 were 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. 

5-96 
Feasibility of Evaporative Emission Control 

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 are proposing to 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 

5-97 
Draft Regulatory Impact Analysis 

soaking them for 12 weeks with the new test fuel. Note that all of the test tanks had been 

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 proposed standard when tested on fuel CE10. The fuel tank 

with a continuous EVOH barrier was well below the proposed 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 

5-98 
Feasibility of Evaporative Emission Control 

buoyancy refers to the effect on air density on the perceived weight of an object. As air density 

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.201 

One testing laboratory presented data to EPA on their experience with variability in 

weight loss measurements when performing permeation testing on portable fuel tanks.202 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.203 

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 would be 

tested without fuel in it and used as a reference fuel tank. Dry sand would be added to this tank 

to make up the difference in mass associated with the test tank being full of fuel. The reference 

tank would then be sealed so that the buoyancy effect on the reference tank would be the same as 

the test tank. The measured weight loss of the test tank could then be corrected by any measured 

changes in weight in the reference tank. The California Air Resources Board has proposed this 

approach for measuring portable fuel tank emissions, and they refer to the reference tank as a 

“trip blank.”204 

5.6.2.4 Engineering Design-Based Certification 

Fuel does not permeate through metal and automotive style EVOH barrier tanks have 

very low permeation through the walls of the tank. We are proposing to allow design-based 

certification for metal tanks and co-extruded high-density polyethylene fuel tanks with a 

continuous ethylene vinyl alcohol barrier layer. The EVOH barrier layer would be required to be 

at least 2 percent of the wall thickness of the fuel tank. 

To address the permeability of the fuel cap, seals, and gaskets used on metal and 

co-extruded tanks, we are proposing that the design criteria include a specification that seals and 

gaskets that are not made of low-permeation materials must have a total exposed surface area 

less than 1000 mm2

. A low-permeation material would have 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 J2659.205 A 

metal or co-extruded fuel tank with seals that meet this design criterion would reliably pass the 

standard. 

5.6.3 Diurnal Emission Testing 

The proposed test procedure for diurnal emissions is to place the fuel tank in a SHED6

, 

vary the temperature over a prescribed profile, and measure the hydrocarbons escaping from the 

fuel tank. The final result would be reported in grams per gallon where the grams are the mass 

6

 Sealed Housing for Emission Determination 

5-99 
Draft Regulatory Impact Analysis 

of hydrocarbons escaping from the fuel tank over 24 hours and the gallons are the nominal fuel 

tank capacity. The proposed test procedure is based on the automotive evaporative emission test 

described in 40 CFR part 86, subpart B, with modifications specific to marine applications. If 

we were proposing diurnal emissions standards for Small SI applications, the test procedures 

would be similar and would be based on a 72-96°F temperature profile. 

5.6.3.1 Temperature Profile 

We are proposing that portable marine fuel tanks would be tested over the same 72-96°F 

(22.2-35.6°C) temperature profile used for automotive applications. This temperature profile 

represents a hot summer day when ground level ozone emissions (formed from hydrocarbons 

and oxides of nitrogen) would be highest. This temperature profile would be for the air 

temperature in the SHED. 

For installed marine fuel tanks, we believe that the fuel temperature profile observed in 

the tank would have 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 would see 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 are 

proposing to consider a boat below 26 feet (7.9 m) 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 are proposing a 

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. For larger boats, we are proposing a test temperature profile of 81.6­

86.4/F (27.6-30.2/C). These test temperature profiles would be 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. 

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Feasibility of Evaporative Emission Control 

Figure 5.6-3: Proposed Diurnal Temperature Profiles 

70 

75 

80 

85 

90 

95 

100 

0 4 8 12 16 20 24 

Elapsed Time [hours] 

Te

m

p

erature [°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 are proposing 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 proposing a different 

approach. Prior to the first day of testing, the canister would be loaded to full working capacity, 

then run over the diurnal test temperature cycle to allow one day of passive purging. The test 

result would then be 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 would be necessary. Prior to the first day of testing, the fuel would 

be stabilized at the initial test temperature. Following this stabilization, the SHED would be 

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 are proposing a one-day test for the following technologies: sealed system without 

pressure relief, sealed system with a pressure relief valve, sealed bladder fuel tanks, sealed fuel 

tanks with a volume compensating air bag. 

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Draft Regulatory Impact Analysis 

5.6.3.2 Test Fuel 

Consistent with the automotive test procedures, we are proposing that the test take place 

using certification gasoline with a vapor pressure of 9.0 RVP. We are not proposing to 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, we 

are proposing that the fill level at the start of the test be 40 percent of the nominal capacity of the 

fuel tank. Nominal capacity of the fuel tank would be 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,” would not be considered in the 

nominal capacity of the fuel tank. 

5.6.3.3 Tank Configuration 

Personal watercraft and other 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, for open vent marine fuel tanks 

that are designed with a connection for a vent line, we propose that the 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 proposed standards would be 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 would be appropriate to correct for permeation. In such a case, we propose 

that the permeation rate could be measured from the fuel tank and subtracted from the final 

diurnal test result. The fuel tank permeation rate would have 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 would have to be 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 would need 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 would 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 would not be 

removed after the diurnal test, and the second permeation test would begin within 8 hours of the 

end of the diurnal test. 

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Feasibility of Evaporative Emission Control 

5.6.3.4 Carbon Canister Engineering Design 

We are proposing to allow design-based certification 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 proposed standards. The following 

discussion outlines the requirements that would be 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.206 

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 would be 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 proposed 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. 

We are proposing that the BWC of the carbon be at least 9 g/dL based on the test procedures 

specified in ASTM D5228-92.207 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, we are proposing to use the ASTM procedure because it 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 proposing 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 boats less than 26 feet in length. For larger boats, the fuel temperature 

may be less affected by diurnal temperature swings for two reasons. First, these fuel tanks 

would be in larger vessels which are more likely to be stored in the water and therefore, subject 

to smaller temperature fluctuations. Second, these fuel tanks would likely be larger and have 

larger thermal inertia in the fuel which may lead to lower temperature fluctuation. Therefore, for 

fuel tanks installed on boats greater than or equal to 25 feet, we are proposing a design minimum 

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Draft Regulatory Impact Analysis 

volume of 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 proposed 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.208

 We proposing design-based certification requirements for humidity resistance 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.209 

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 

proposing to include 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. We 

are proposing a pellet strength of at least 85 percent. The proposed test procedure is ASTM 

D3802-79210 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 would use 

twenty 1⁄2" steel balls and ten 3⁄4" steel balls rather than fifteen of each as specified in ASTM 

D3802-79. These proposed 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.211 

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Feasibility of Evaporative Emission Control 

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). 

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.212 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. 

5.6.3.4.5 Integration with Fuel System 

5-105 
Draft Regulatory Impact Analysis 

It would be important that a carbon canister system be appropriately integrated into the 

fuel system. For instance, the canister would need to be positioned in the vent line, and 

potentially a liquid separation valve added, to ensure that liquid fuel would not reach the canister 

during refueling. We would 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, would not be 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 would 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 proposed 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 would be about 1.2 gallons for an average piece of Small SI 

equipment and 31 gallons for an average boat. This translates to a fuel savings of about 44 

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. would be expected to have evaporative 

emission control. 

5.7.3 Safety 

As part of the development of this proposed rule, EPA performed a technical study on the 

safety of emission control technology for Small SI equipment and Marine SI vessels.213 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 

and in storage. That reduction, coupled with some expected equipment redesign, is expected to 

5-106 
Feasibility of Evaporative Emission Control 

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.214 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 would 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 being proposed 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 would need to pass these standards and every indication is that they would 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 would 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 proposed evaporative emissions standards would not 

lead to an increase in incremental risk of fires or burns, and in many cases may incrementally 

5-107 
Draft Regulatory Impact Analysis 

decrease safety risks in certain situations.. 

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Feasibility of Evaporative Emission Control 

APPENDIX 5A: Diurnal Temperature Traces 

Figure 5A-1: Temperature Trace for Personal Watercraft on Trailer 

fuel temp 

85.00 ambient 

80.00 

75.00 

70.00 

65.00 

60.00 

55.00 

50.00 

45.00 

9/9/02 9/11/02 9/13/02 9/15/02 9/17/02 9/19/02 9/21/02 9/23/02 9/25/02 9/27/02 

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] 

105 

100 

95 

90 

85

Temperature [deg F]

80 

75 

70 

Fuel Temp 

65 Ambient Temp 

60 

55 

7/10/01 7/12/01 7/14/01 7/16/01 7/18/01 7/20/01 7/22/01 7/24/01 

12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 

Figure 5A-2: Temperature Trace for Jet Boat on Trailer 

95.00 

90.00 

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Draft Regulatory Impact Analysis 

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 

10/12/01 

12:00 AM 

10/12/01 

12:00 PM 

10/13/01 

12:00 AM 

10/13/01 

12:00 PM 

10/14/01 

12:00 AM 

10/14/01 

12:00 PM 

10/15/01 

12:00 AM 

10/15/01 

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 

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 

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 

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Temperature [deg F] Temperature [deg F] 

Feasibility of Evaporative Emission Control 

Figure 5A-5: Temperature Trace for Runabout in Water 

85 

80 

75 

70 

65 

60 

55 

50 

Fuel Temp 45 

Ambient Temp 

40 Water Temp 

35 

9/12/01 9/15/01 9/18/01 9/21/01 9/24/01 9/27/01 9/30/01 10/3/01 

12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 

Figure 5A-6: Temperature Trace of Deckboat in Water 

95 

90 

85 

80 

75 

70 

65 

Fuel Temp 60 

Ambient Temp
 

55
 Water Temp 

50 

45 

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 

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 

5-111 
Draft Regulatory Impact Analysis 

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 C ap Vent, Lab 1 

Stock C ap 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 

HC [

gra

ms] 

0 3 6 9 12 15 18 21 24 

Te st Hours 

T

e

m

perature [

d

eg 

C] 

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Feasibility of Evaporative Emission Control 

Figure 5B.1-2: Diurnal/Diffusion Test Results for BP Plastic Fuel Tank 

0.0 

1.0 

2.0 

3.0 

4.0 

5.0 

6.0 

7.0 

8.0 

0 3 6 9 12 15 18 21 24 

Te st Hours 

HC [

gra

m

s]

Temperature 

Modified Cap Vent 

Stock Cap Vent 

Hose Vent 

5.0 

0.0 

20.0 

25.0 

35.0 

40.0 

T

e

m

perat

ure [

deg C] 

10.0 

30.0 

15.0 

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 [gra

m

s] 

Temperature 

Stock Cap Vent 

Hose Vent 

8.0 

0.0 

24.0 

32.0 

40.0 

48.0 

T

e

m

perat

ure [

deg C] 

16.0 

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Draft Regulatory Impact Analysis 

Figure 5B.1-4: Diurnal/Diffusion Test Results for TP Plastic Fuel Tank 

5-114
 

0.0 

0.2 

0.4 

0.6 

0.8 

1.0 

1.2 

1.4 

1.6 

HC [

gra

m

s] 

5.0 

0.0 

10.0 

20.0 

25.0 

35.0 

40.0 

T

e

m

perat

ure [

deg C] 

15.0 

30.0 

Temperature 

Stock Cap Vent 

Hose Vent 

0 3 6 9 12 15 18 21 24
 

Test Hours 
Feasibility of Evaporative Emission Control 

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 

0 3 6 9 12 15 18 21 24 

Test Hours 

HC [

gra

m

s]

Temp (cap) 

Temp (hose) 

Stock Cap Vent 

Hose Vent 

5.0 

0.0 

10.0 

20.0 

25.0 

35.0 

T

e

m

perat

ure [

deg C] 

15.0 

30.0 

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 

T

e

m

perat

ure [

deg C] 

HC [

gra

m

s] 4.00 20.0 

3.00 15.0 

2.00 10.0 

5-115 
Draft Regulatory Impact Analysis 

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 [

gra

m

s] 

5.0 

0.0 

10.0 

20.0 

25.0 

35.0 

T

e

m

perat

ure [

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 

0 3 6 9 12 15 18 21 24 

Test Hours 

HC [

gra

m

s]

Temp (cap) 

Temp (hose) 

Stock Cap Vent 

Hose Vent 

5.0 

0.0 

10.0 

20.0 

25.0 

35.0 

T

e

m

perat

ure [

deg C] 

15.0 

30.0 

5-116
 
Feasibility of Evaporative Emission Control 

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
 

E

vap

orati

v

e H

C [gra

m

s/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 

5-117 

30 
Draft Regulatory Impact Analysis 

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 

5-118 
Feasibility of Evaporative Emission Control 

Table 5D-2: Fuel System Material Permeation Rates at 23°C by Fuel Type 215,216,217,218,219,220 

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. 

5-119 
Draft Regulatory Impact Analysis 

Table 5D-3: Fuel System Material Permeation Rates at 40°C by Fuel Type 221,222 

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 223 

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 

– 

– 

– 

– 

– 

– 

– 

5-120 
Feasibility of Evaporative Emission Control 

Table 5D-5: Fuel System Material Permeation Rates at 60°C by Fuel Type 224,225,226,227 

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 

5-121 
Draft Regulatory Impact Analysis 

APPENDIX 5E: Diurnal Test Temperature Traces 

Table 5E-1: Temperature vs. Time Sequence for Proposed Diurnal Testing 

Test 

Time* 

[minutes] 

Portable Fuel Tanks 

SHED Air Temperature 

Installed Fuel Tanks 

Boat < 26 feet (7.9m) 

Fuel Temperature 

Installed Fuel Tanks 

Boat $26 feet (7.9m) 

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 

5-122 
Feasibility of Evaporative Emission Control 

Chapter 5 References 

1. Reddy, S., “Prediction of Fuel Vapor Generation From a Vehicle Fuel Tank as a Function of Fuel RVP and 

Temperature,” SAE Paper 892089, 1989, Docket Identification EPA-HQ-OAR-2004-0008-0169. 

2. Cushing, T., “Fuel Tank Hydrocarbon Emission Testing,” prepared by Sterling Performance for the U.S. EPA, 

Report #040107, September 30, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0137. 

3. Cushing, T., “Fuel Tank Hydrocarbon Emission Testing,” prepared by Sterling Performance for the U.S. EPA, 

Report #040137, November 3, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0138. 

4. “Evaporative Emissions from Offroad Equipment,” California Air Resources Board, June 22, 2001, Docket 

Identification EPA-HQ-OAR-2004-0008-0051. 

5. “Docket No. A-2000-02; Notice or Proposed Rulemaking for the Control of Emissions from Spark-Ignition 

Marine Vessels and Highway Motorcycles; 40 C.F.R. Parts 86, 90, 1045, 1051, and 1068,” Comments from the 

National Marine Manufacturers Association, Docket Identification EPA-HQ-OAR-2004-0008-0211. 

6. “Before the United States Environmental Protection Agency, Comments by Brunswick Corporation, Notice of 

Proposed Rulemaking, Part 1045 Control of Emissions from Spark-Ignition Marine Vessels,” Comments from 

Brunswick Corporation, Docket Identification EPA-HQ-OAR-2004-0008-0192. 

7. “Diurnal Emissions Testing of Walk-Behind Mowers Configured with Fuel Tank Pressure Relief Valves 

(September 2002),” California Air Resources Board, September 17, 2002, Docket Identification EPA-HQ-OAR2004-0008-0052. 

8. “Aboveground Storage Tanks (AST); Enhanced Vapor Recovery Regulation,” California Air Resources Board, 

August 16, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0413. 

9. Email from Pamela Gupta, California Air Resources Board, to Mike Samulski, U.S. EPA, “Aboveground Storage 

Tanks (ASTs) Field Study Presentation,” September 6, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0420. 

10. Samulski, M., “Characterization and Control of Evaporative Emissions from Fuel Tanks in Nonroad 

Equipment,” SAE Paper 2006-32-0094, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0424. 

11. Beverley, K., Clint, J., Fletcher, P., “Evaporation Rates of Pure Liquids Measured Using a Gravimetric 

Technique,” Phys. Chem. Chem. Phys., 1999, 1, 149-153, Received July 9, 1998, Accepted October 13, 1998, 

Docket Identification EPA-HQ-OAR-2004-0008-0103. 

12. Batterman, S., Yu, Y., Jia, C., Godwin, C., “Non-methane Hydrocarbon Emissions from Vehicle Fuel Caps,” 

Atmospheric Environment 39 (2005), Received May 27, 2004, Accepted December 1, 2004, Docket Identification 

EPA-HQ-OAR-2004-0008-0102. 

13. Sterling Performance, “USEPA Fuel Tank Hydrocarbon Emission Testing,” prepared for the U.S. EPA, Report 

Number 040195, January 26, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0139. 

14. “24 hr EPA Diurnal MicroSHED of Lawn Mower Gas Tanks,” Testing Services Group, Reports L504835-1.1, 

Prepared for U.S. EPA, April 20, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0140. 

15. “24 hr EPA Diurnal MicroSHED of Lawn Mower Gas Tanks,” Testing Services Group, Reports L504835-1.2, 

Prepared for U.S. EPA, April 20, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0141. 

5-123 
Draft Regulatory Impact Analysis 

16. “24 hr EPA Diurnal MicroSHED of Lawn Mower Gas Tanks,” Testing Services Group, Reports L504835-1.3, 

Prepared for U.S. EPA, April 20, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0142. 

17. “24 hr EPA Isothermal MicroSHED of Lawn Mower Gas Tanks,” Testing Services Group, Reports L504835­

2.1, Prepared for U.S. EPA, April 20, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0143. 

18. “24 hr EPA Isothermal MicroSHED of Lawn Mower Gas Tanks,” Testing Services Group, Reports L504835­

2.2, Prepared for U.S. EPA, April 20, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0144. 

19. “24 hr EPA Isothermal MicroSHED of Lawn Mower Gas Tanks,” Testing Services Group, Reports L504835­

2.3, Prepared for U.S. EPA, April 20, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0145. 

20. Haskew, H., Cadman, W., “Evaporative Emissions Under Real Time Conditions,” SAE Paper 891121, 1989, 

Docket Identification EPA-HQ-OAR-2004-0008-0168. 

21. Haskew, H., Cadman, W., Liberty, T., “The Development of a Real-Time Evaporative Emissions Test,” SAE 

Paper 901110, 1990, Docket Identification EPA-HQ-OAR-2004-0008-0170. 

22. 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. 

23. 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. 

24. “A Picture Book Concerning the NMMA 2005 Summer Test Program: Carbon Canisters for Marine Diurnal 

Control,” Harold Haskew & Associates, Inc., July 12, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0127. 

25. Dr. Michael Tschantz, “Summer Test Program Carbon Analysis,” presented by Meadwestvaco Corporation at 

the 2005 International Boatbuilders Exhibition and Conference, October 20, 2005, Docket Identification EPA-HQOAR-2004-0008-0290. 

26. Andreatta, D., Heydinger, G., Bixel, R., Park, J., Jorgensen, S., “Evaluation of the Ignition Hazard Posed by 

Onboard Refueling Vapor Recovery Canisters,” SAE Paper 2001-01-0731, 2001, Docket Identification EPA-HQOAR-2004-0008-0494. 

27. “Diurnal Testing of Off-Road Equipment Retrofitted with Carbon Canister Evaporative Emission Control 

Systems (March 2003),” California Air Resources Board, March 25, 2003, Docket Identification EPA-HQ-OAR2004-0008-0053. 

28. Haskew, H., Cadman, W., Liberty, T., “The Development of a Real-Time Evaporative Emissions Test,” SAE 

Paper 901110, 1990, Docket Identification EPA-HQ-OAR-2004-0008-0170. 

29. Email from Reid Clontz, MeadWestvaco, to Mike Samulski, U.S. EPA, “Temperature and Ethanol Questions,” 

July 7, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0423. 

30. American Boat and Yacht Council, “H-24 Gasoline Fuel Systems,” 2005, Docket Identification EPA-HQ-OAR2004-0008-0429. 

31. “Diurnal Emissions Testing of Walk-Behind Mowers Configured with Fuel Tank Pressure Relief Valves 

(September 2002),” California Air Resources Board, September 17, 2002, Docket Identification EPA-HQ-OAR2004-0008-0052. 

5-124 
Feasibility of Evaporative Emission Control 

32. Letter from Bill Scott, Country Industries Technologies, to Mike Samulski U.S. EPA, regarding a gas tank vent 

design, July 20, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0287. 

33. Compact Membrane Systems, Inc., www.compactmembrane.com, Docket Identification EPA-HQ-OAR-2004­

0008-0100. 

34. Koch, W., “Developing Technology for Enhanced Vapor Recovery: Part 1 - Vent Processors,” Petroleum 

Equipment & Technology, February/March 2001, Docket Identification EPA-HQ-OAR-2004-0008-0099. 

35. Membrane Technology & Research, Inc., www.mtrinc.com, Docket Identification EPA-HQ-OAR-2004-0008­

0101. 

36. “New Evaporative Control System for Gasoline Tanks,” Memorandum from Chuck Moulis, EPA to Glenn 

Passavant, Nonroad Center Director, EPA, March 1, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0261. 

37. Letter from Kevin Madison, Top Dog Systems, to Mike Samulski, U.S. EPA, regarding the Top Dog vaporless 

fuel system, April 23, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0258. 

38. 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. 

39. Emails from Steve Vaitses, Seacurefill to Mike Samulski, U.S. EPA, “VCS diagrams 1-4 attachments,” and 

“VCS attachments 5-7,” April 27, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0395. 

40. Testing Services Group, “Marine Fuel Tank Vapor Trap Diurnal Emissions Testing; 48 hr EPA (custom) 

Diurnal,” TSG Report No. L605816-1.2, July 14, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0445. 

41. Fox, J., “Fuel Temperature Measurements on Small Equipment," Fox Automotive, August 2004, Docket 

Identification EPA-HQ-OAR-2004-0008-0181. 

42. Cushing, T., “Fuel Tank Hydrocarbon Emission Testing,” prepared by Sterling Performance for the U.S. EPA, 

Report #040107, September 30, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0137. 

43. Cushing, T., “Fuel Tank Hydrocarbon Emission Testing,” prepared by Sterling Performance for the U.S. EPA, 

Report #040137, November 3, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0138. 

44. Wong, W., “Addition of Evaporative Emissions for Small Off-Road Engines,” California Air Resources Board 

OFFROAD Model Change Technical Memo, Revised April 21, 2003, Docket OAR-2004-0008, Document OAR2004-0008-0006. 

45. Tuckner, P., Baker, J., “Fuel Permeation Testing using Gravimetric Methods,” SAE Paper 2000-01-1096, 2000, 

Docket Identification EPA-HQ-OAR-2004-0008-0160. 

46. Allen, S.J., “Fuel Tank Permeability Test Procedure Development; Final Report,” U.S. Coast Guard, December 

1986, Docket Identification EPA-HQ-OAR-2004-0008-0231. 

47. 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. 

48. “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. 

5-125 
Draft Regulatory Impact Analysis 

49. “Permeation Rates of Small Off Road Engine High-Density Polyethylene Fuel Tanks (February 2001 Testing), 

June 8, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0147. 

50. “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 

51. “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. 

52. “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. 

53. “Test Method 513; Determination of Permeation for Spill-Proof Systems,” California Air Resources Board, 

Adopted July 6, 2000, Docket Identification EPA-HQ-OAR-2004-0008-0150. 

54. 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. 

55. 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. 

56. “Test Method 513; Determination of Permeation for Spill-Proof Systems,” California Air Resources Board, 

Adopted July 6, 2000, Docket Identification EPA-HQ-OAR-2004-0008-0150. 

57. Lockhart, M., Nulman, M., Rossi, G., “Estimating Real Time Diurnal Permeation from Constant Temperature 

Measurements,” SAE Paper 2001-01-0730, 2001, Docket Identification EPA-HQ-OAR-2004-0008-0161. 

58. 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. 

59. 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. 

60. 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. 

61. Tuckner, P., Baker, J., “Fuel Permeation Testing using Gravimetric Methods,” SAE Paper 2000-01-1096, 2000, 

Docket Identification EPA-HQ-OAR-2004-0008-0160. 

62. 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. 

63. Stevens, M., Demorest, R., “Fuel Permeation Analysis Method Correction,” SAE Paper 1999-01-0376, 1999, 

Docket Identification EPA-HQ-OAR-2004-0008-0157. 

64. Lockhart, M., Nulman, M., Rossi, G., “Estimating Real Time Diurnal Permeation from Constant Temperature 

Measurements,” SAE Paper 2001-01-0730, Docket Identification EPA-HQ-OAR-2004-0008-0161. 

65. Testimony of and Presentation, H. Haskew, President, Harold Haskew & Associates, MI, October 7, 2002, 

Docket Identification EPA-HQ-OAR-2004-0008-0202. 

5-126 
Feasibility of Evaporative Emission Control 

66. 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. 

67. Email from Jim Watson, California Air Resources Board, to Mike Samulski, U.S. EPA, “Vapor Loss for 

Variable Volume Containers.xls,” October 26, 2005, Docket Identification EPA-HQ-OAR-2004-0008-0291. 

68. Email from Harold Haskew, Harold Haskew & Associates, to Mike Samulski, U.S. EPA, “High-low permeation 

data,” April 9, 2002, Docket Identification EPA-HQ-OAR-2004-0008-0238. 

69. 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, 

Docket Identification EPA-HQ-OAR-2004-0008-0172. 

70. www.arb.ca.gov/msprog/spillcon/reg.htm, Updated March 26, 2001, Copy of linked data reports available in the 

Docket, Docket Identification EPA-HQ-OAR-2004-0008-0186. 

71. 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. 

72. “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. 

73. “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. 

74. Conversation between Mike Samulski, U.S. EPA and Tom Schmoyer, Sulfo Technologies, June 17, 2002. 

75. “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. 

76. “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. 

77. “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. 

78. 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. 

79. 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. 

80. 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. 

81. 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. 

82. “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. 

5-127 
Draft Regulatory Impact Analysis 

83. 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. 

84. 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. 

85. “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. 

86. “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. 

87. 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. 

88. “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. 

89. “Fluorination Information,” e-mail from Doug McGregor, BMW, to Mike Samulski, US EPA, August 8, 2003, 

Docket Identification EPA-HQ-OAR-2004-0008-0259. 

90. “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. 

91. “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. 

92. “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. 

93. “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. 

94. 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. 

95. 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. 

96. 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. 

97. 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. 

98. 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. 

5-128 
Feasibility of Evaporative Emission Control 

99. “Fluorination Information,” e-mail from Doug McGregor, BMW, to Mike Samulski, US EPA, August 8, 2003, 

Docket Identification EPA-HQ-OAR-2004-0008-0259. 

100. 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. 

101. 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. 

102. 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. 

103. 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. 

104. 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. 

105. 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. 

106. “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. 

107. “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. 

108. “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. 

109. “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. 

110. “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. 

111. Faler, Gary, “Cyclics CBT® Resin for Dual Layer Applications in Rotomolding,” Cyclics Corporation, August 

2006, Docket Identification EPA-HQ-OAR-2004-0008-0415. 

112. 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. 

113.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. 

114. Fish, D., “Advanced Polymer Concepts,” Presentation at the 2004 International Boatbuilders Exposition, 

October 25, 2004, Docket Identification EPA-HQ-OAR-2004-0008-0039. 

115. 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. 

5-129 
Draft Regulatory Impact Analysis 

116. 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. 

117. 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. 

118. 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. 

119. “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. 

120. “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. 

121. 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. 

122. 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. 

123. “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. 

124. “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. 

125. 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. 

126. 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. 

127. 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. 

128. SAE Recommended Practice J30, “Fuel and Oil Hoses,”June 1998, Docket Identification EPA-HQ-OAR2004-0008-0176. 

129. 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. 

130. “OPEI Fuel Line Permeation Results,” Walbro Engine Management, April 12, 2006, Docket Identification 

EPA-HQ-OAR-2004-0008-0440. 

131. 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. 

5-130 
Feasibility of Evaporative Emission Control 

132. 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. 

133. 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. 

134. 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. 

135. 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. 

136. 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. 

137. 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. 

138. “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. 

139. 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. 

140. 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. 

141. 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. 

142. SAE Recommended Practice J2260, “Nonmetallic Fuel System Tubing with One or More Layers,”1996, 

Docket Identification EPA-HQ-OAR-2004-0008-0180. 

143. 33 CFR 183.558 

144. 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. 

145. “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. 

146. “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. 

147. “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. 

5-131 
Draft Regulatory Impact Analysis 

148. 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. 

149. 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. 

150. 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. 

151. 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. 

152. 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. 

153. 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. 

154. 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. 

155. 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. 

156. “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. 

157. “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. 

158. “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. 

159. 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. 

160. 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 

161. 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. 

162. 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. 

163. 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. 

164. 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. 

5-132 
Feasibility of Evaporative Emission Control 

165. “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. 

166. “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. 

167. “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. 

168. 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. 

169. 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. 

170. 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. 

171. “Alpha List of OEM Approvals,” http://www.precixinc.com/oemlist.html, downloaded August 15, 2006, 

Docket Identification EPA-HQ-OAR-2004-0008-0411. 

172. “Viton: Volume Swell of Viton® Fluoroelastomers in Fuel C / Ethanol Blends,” DuPont Performance 

Elastomers, 2006, Docket Identification EPA-HQ-OAR-2004-0008-0510. 

173. “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. 

174. 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. 

175. 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. 

176. “Technical Information; Dyneon Fluorelastomer LTFE 6400X,” 3M, Issued February, 2003, Docket 

Identification EPA-HQ-OAR-2004-0008-0521. 

177. “Relative Permeation of Elastomers,” Precix, downloaded from www.precixinc.com on February 14, 2007, 

Docket Identification EPA-HQ-OAR-2004-0008-0525. 

178. 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. 

179. 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. 

180. Letter from Van DePiero, City of Pittsburg, California to Steve Burkholder, Enviro Fill, April 19, 2006, Docket 

Identification EPA-HQ-OAR-2004-0008-0384. 

181. American Boat and Yacht Council, “H-24 Gasoline Fuel Systems,” 2005, Docket Identification EPA-HQOAR-2004-0008-0429. 

5-133 
Draft Regulatory Impact Analysis 

182. 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. 

183. 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. 

184. Letter from Steve Burkholder, Enviro-Fill, to Mike Samulski, U.S. EPA, March 1, 2006, Docket Identification 

EPA-HQ-OAR-2004-0008-0430. 

185. Letter from Steve Burkholder, Enviro-Fill, to Mike Samulski, U.S. EPA, January 13, 2006, Docket 

Identification EPA-HQ-OAR-2004-0008-0446. 

186. 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. 

187. SAE Recommended Practice J30, “Fuel and Oil Hoses,” June 1998, Docket Identification EPA-HQ-OAR2004-0008-0176. 

188. 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. 

189. 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. 

190. 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. 

191. 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. 

192. 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. 

193. 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. 

194. 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. 

195. 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. 

196. “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. 

197. “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 

198. “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. 

5-134 
Feasibility of Evaporative Emission Control 

199. “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. 

200. 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. 

201. 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. 

202. 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. 

203. 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. 

204. 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. 

205. “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. 

206. 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. 

207. “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. 

208. 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. 

209. "Carbon Specs," email from M. Tschantz , MeadWestvaco to M. Samulski, U.S. EPA, November 18, 2005, 

Docket Identification EPA-HQ-OAR-2004-0008-0421. 

210. “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. 

211. “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. 

212. 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. 

213. “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. 

214. “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. 

5-135 
Draft Regulatory Impact Analysis 

215. 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. 

216. 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. 

217. “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. 

218. Goldsberry, D., “Fuel Hose Permeation of Fluoropolymers,” SAE Paper 930992, 1993, Docket Identification 

EPA-HQ-OAR-2004-0008-0173. 

219. Tuckner, P., Baker, J., “Fuel Permeation Testing Using Gravimetric Methods,” SAE Paper 20001-01-1096, 

2000, Docket Identification EPA-HQ-OAR-2004-0008-0160. 

220. 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. 

221. 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. 

222. 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. 

223. 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. 

224. 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. 

225. “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. 

226. 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. 

227. 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. 

5-136 
Costs of Control 

CHAPTER 6: Costs of Control 

This chapter describes our approach to estimating the cost of complying with the 

proposed 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 reflect 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 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 
Draft 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 proposed standards. 

Many of the engine technologies available to marine 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 proposed exhaust emission 

standards for Small land-based spark-ignition (Small SI) engines. 

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 

overhead valve design. Certification data from 2005 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 2005 technology market mix is presented in Table 6.2-1. 

For the proposed Phase 3 standards, Class I engines are estimated to use catalysts and 

engine design improvements required to use catalysts safely. For Class II engines, different 

technologies were assigned depending on whether the engine was a one cylinder or a multiple 

cylinder engine. All one cylinder engines were estimated to use catalysts. For two or more 

cylinders, the largest engine family per engine manufacturer 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. 

6-2 
Costs of Control 

Table 6.2-1: 2005 Technology Market Mix 

Class I Class II 

SV 65% 2% 

OHV 35% 98% 

w/ Catalyst 0.04% 0.2% 

w/ Other (EFI and/or watercooled) 0 2% 

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 65% 2% 

OHV 35% 98% 

w/ Catalyst 100% 72% 

w/ Other (EFI and/or watercooled) 0 28%

 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. 

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 

6-3 
Draft Regulatory Impact Analysis 

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 proposed 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 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 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. Engine families using 

credits to certify to the emission standard with ABT were not included. 

6-4 
Costs of Control 

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 

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. 

6-5 
Draft Regulatory Impact Analysis 

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 

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. 

6-6 
Costs of Control 

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 

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 

6-7 
Draft Regulatory Impact Analysis 

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 estimatess 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 Proposed 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 
Draft 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 Proposed 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 
Draft Regulatory Impact Analysis 

Table 6.2-10: Class I Estimated Total Costs Per Engine (Variable) and 

Per Engine Family (Fixed) to Achieve Proposed 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 proposed 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 he 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 13-20 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 15-45 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 proposed 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 
Draft 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 estimatedd 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 
Draft 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 
Draft 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 
Draft 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 
Draft 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 
Draft 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 proposed 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 

6-24 
Costs of Control 

updated 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 proposed 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 
Draft 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 2005 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. Several 

families were also removed from 250 useful life Class II for they sufficiently met the proposed 

Class II standard. Table 6.2-26 lists 3 engine families in Class I and 37 engine families in Class 

II for certification. 

Table 6.2-26: Number of 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 

125 1 1 1 250 11 11 7* 

250 2 2 1 500 19 6** 17*** 

500 -- -- -- 1000 7 7 7 

* Two engine families were sufficiently below the Phase 3 standard
 

** For Phase 3, companies with small volume production (<10,000) can use an assigned df.
 

***Eight engine families had catalysts however only one sufficiently met the Phase 3 standard and
 

therefore the remaining seven engine families will need new catalyst designs to reduce HC+NOx.
 

6-26 
Costs of Control 

Table 6.2-27 lists the certification costs as incurred. 

Table 6.2-27: Certification Costs As Incurred - LPG 

Class I Class II

 Year 2012 2011

 Baseline Emission Testing $12,072 $148,888

 Dynamometer Aging $26,994 $900,974

 End of Life Emission Test $8,048 $96,576

 Total $47,114 $1,146,438 

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 2005 

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 eight of the V-twin LPG engines are already certified with catalysts. Costs for 

catalyst system redesign for seven of the eight 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 (3 in Class I and 37 in Class II). 

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. 

6-27 
Draft Regulatory Impact Analysis 

Table 6.2-29: Total Fixed Costs for LPG 

Engine Families, as Incurred, 2005$ 

Class I Class II 

2012 2011 

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 
Draft 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$ 

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% 1 200 0* 0 

250 905,005 1.34% 1 4,500 0 0 

500 623,431 0.95% 1 5,398 0 0 

Class II 

250 3,334,488 0.67% 1 14,500 $1.64 $23,780 

2 10,469 -$3.65 -$38,306 

500 724,231 12.07% 1 12,918 $10.70 $138,172 

2 90,630 $4.90 $ 441,661 

1000 821,463 1.92% 2 18,700 $15.37 $ 287,377 

2012 Total Increase $852,673 

* Using same cost as Class I gasoline engine. 

Table 6.2-31 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 
Draft 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. Every engine in Class I is 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 

6 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 2005 EPA Certification Database 

were utilized to determine the percentage of technologies per useful life. A portion of the 

engines, one large multi-cylinder engine family per engine manufacturer, are assigned the use of 

electronic fuel injection and the remainder catalysts. Some engines would not to require any 

costs. Long term costs (learning) are 6 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 0.40% 13.50% 4.50% 81.70% 

500 1.90% 7.80% 0.20% 90.10% 

1000 8.10% 44.50% 30.70% 16.70% 

6-32 
Costs of Control 

Table 6.2-33: Variable Costs Per Engine for Meeting
 

Proposed 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 10.56 9.72 -- --

125 - OHV 8.67 8.04 -- --

250 12.24 11.39 32.21 27.05 

500 16.05 14.92 25.32 21.38 

1000 -- -- 57.94 46.18 

*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 2005 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 55% ---

125 - OHV 30% ---

250 9% 68% 

500 6% 15% 

1000 --- 17% 

6-33 
Draft Regulatory Impact Analysis 

Table 6.2-35: Class I and Class II Projected Sales 

per Useful Life Category (snowblowers excluded) 

CLASS I CLASS II 

125 125 250 500 250 500 1000 

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 

5,127,510 

5,219,801 

5,311,789 

5,407,460 

5,498,863 

5,594,305 

5,687,801 

5,780,726 

5,872,307 

5,966,857 

6,060,404 

6,155,080 

6,249,153 

6,342,877 

6,435,905 

6,529,799 

6,623,557 

6,717,690 

6,812,592 

6,907,322 

7,001,813 

7,096,586 

7,191,371 

7,286,256 

7,381,095 

7,475,836 

7,570,510 

7,665,267 

7,760,044 

7,854,864 

2,753,967 

2,803,536 

2,852,943 

2,904,327 

2,953,419 

3,004,681 

3,054,897 

3,104,807 

3,153,994 

3,204,777 

3,255,021 

3,305,871 

3,356,397 

3,406,736 

3,456,701 

3,507,131 

3,557,488 

3,608,047 

3,659,018 

3,709,897 

3,760,648 

3,811,550 

3,862,459 

3,913,421 

3,964,359 

4,015,244 

4,066,093 

4,116,987 

4,167,891 

4,218,818 

843,888 

859,077 

874,217 

889,962 

905,005 

920,714 

936,101 

951,395 

966,467 

982,028 

997,424 

1,013,006 

1,028,489 

1,043,914 

1,059,224 

1,074,677 

1,090,108 

1,105,601 

1,121,220 

1,136,810 

1,152,362 

1,167,960 

1,183,559 

1,199,176 

1,214,784 

1,230,377 

1,245,958 

1,261,553 

1,277,152 

1,292,757 

581,329 

591,793 

602,222 

613,068 

623,431 

634,252 

644,852 

655,387 

665,770 

676,490 

687,096 

697,830 

708,495 

719,121 

729,668 

740,313 

750,943 

761,615 

772,375 

783,115 

793,828 

804,572 

815,319 

826,076 

836,829 

847,570 

858,303 

869,046 

879,792 

890,542 

3,107,434 

3,163,391 

3,219,633 

3,278,156 

3,334,488 

3,393,240 

3,450,280 

3,506,937 

3,563,590 

3,621,088 

3,678,416 

3,736,330 

3,793,793 

3,851,245 

3,908,253 

3,965,663 

4,023,108 

4,080,946 

4,138,843 

4,196,572 

4,254,228 

4,312,046 

4,369,880 

4,427,794 

4,485,625 

4,543,399 

4,601,154 

4,658,962 

4,716,772 

4,774,603 

674,916 

687,070 

699,285 

711,996 

724,231 

736,992 

749,380 

761,686 

773,991 

786,479 

798,930 

811,509 

823,989 

836,468 

848,850 

861,319 

873,795 

886,357 

898,932 

911,471 

923,993 

936,551 

949,112 

961,691 

974,251 

986,799 

999,343 

1,011,899 

1,024,455 

1,037,016 

765,527 

779,312 

793,168 

807,585 

821,463 

835,937 

849,989 

863,946 

877,903 

892,068 

906,191 

920,458 

934,614 

948,768 

962,812 

976,955 

991,107 

1,005,355 

1,019,618 

1,033,840 

1,048,044 

1,062,288 

1,076,535 

1,090,802 

1,105,049 

1,119,282 

1,133,510 

1,147,751 

1,161,993 

1,176,240 

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 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 

-

-

-

-

83,668,785 

85,121,010 

86,543,605 

87,957,519 

89,350,983 

83,764,367 

85,077,605 

86,406,692 

87,727,306 

89,043,033 

90,348,981 

91,667,093 

92,983,300 

94,304,760 

95,637,018 

96,966,870 

98,293,351 

99,623,807 

100,954,421 

102,286,451 

103,617,823 

104,947,825 

106,276,880 

107,607,109 

108,937,613 

110,268,714 

-

-

-

-

11,079,868 

11,272,180 

11,460,567 

11,647,805 

11,832,335 

11,189,968 

11,365,401 

11,542,952 

11,719,371 

11,895,137 

12,069,597 

12,245,682 

12,421,512 

12,598,044 

12,776,019 

12,953,672 

13,130,875 

13,308,609 

13,486,363 

13,664,307 

13,842,164 

14,019,837 

14,197,383 

14,375,087 

14,552,827 

14,730,647 

-

-

-

-

10,008,033 

10,181,740 

10,351,904 

10,521,029 

10,687,708 

10,092,486 

10,250,714 

10,410,851 

10,569,967 

10,728,495 

10,885,844 

11,044,659 

11,203,244 

11,362,463 

11,522,982 

11,683,211 

11,843,035 

12,003,337 

12,163,658 

12,324,150 

12,484,562 

12,644,810 

12,804,943 

12,965,218 

13,125,526 

13,285,906 

-

-

-

105,600,269 

107,414,910 

109,307,519 

111,144,960 

112,970,045 

96,391,317 

97,946,590 

99,497,254 

101,063,746 

102,618,074 

104,172,095 

105,714,100 

107,266,966 

108,820,807 

110,385,260 

111,951,301 

113,512,803 

115,072,341 

116,636,271 

118,200,597 

119,767,112 

121,331,392 

122,894,111 

124,456,311 

126,019,956 

127,583,669 

129,147,933 

-

-

-

18,028,276 

18,338,075 

18,661,185 

18,974,876 

19,286,458 

16,547,001 

16,813,987 

17,080,182 

17,349,093 

17,615,917 

17,882,688 

18,147,395 

18,413,968 

18,680,708 

18,949,270 

19,218,104 

19,486,159 

19,753,877 

20,022,348 

20,290,888 

20,559,804 

20,828,336 

21,096,600 

21,364,775 

21,633,197 

21,901,632 

22,170,161 

-

-

-

46,793,243 

47,597,340 

48,435,987 

49,250,188 

50,058,913 

40,539,821 

41,193,931 

41,846,102 

42,504,930 

43,158,642 

43,812,225 

44,460,754 

45,113,852 

45,767,359 

46,425,330 

47,083,968 

47,740,698 

48,396,601 

49,054,352 

49,712,269 

50,371,106 

51,029,004 

51,686,246 

52,343,268 

53,000,899 

53,658,558 

54,316,449 

6.2.5.2 Fixed Costs 

The stream of fixed costs for meeting the proposed exhaust emission standards are 

presented per useful life category per Class in Table 6.2-37. The total cost per engine family is 

determined by multiplying the costs for engine design changes (R&D, Tooling), certification, 

equipment modifications, by the number of engine families in each class per related useful life 

which is presented in Table 6.2-38. 

EPA does not know the test cell makeup within the facilities of each manufacturer and 

therefore estimates that at least two upgraded analyzers will be purchased for a total of $600,000 

per engine manufacturer. The certification database lists 16 different engine manufacturers of 

nonhandheld engines and 15 engine manufacturers of handheld engines. The 2005 certification 

6-35 
Draft Regulatory Impact Analysis 

database for nonhandheld and handheld engines 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. This analysis estimates the cost for two manufacturer upgrades. A total of 17 different 

nonhandheld engine manufacturers test facilities at 600,000 per test facility yields a total 

estimated cost of $10,200,000. This cost is spread evenly across all products for a total of 

1,700,000 for each category. These costs are fixed costs in this rulemaking. It is estimated that 

engine manufacturers will incur this cost two years prior to implementation of the standard for 

each class - 2010 for Class I and 2009 for Class II. Handheld engines must also be certified 

using the latest test procedures for small engines. The costs for upgrade of equipment totals 

$9,600,000 and is estimated to be incorporated into new certification for the 2010 model year. 

Recovered over 5 years yields $2,680,612 per year. 

Table 6.2-37: Fixed Costs for Compliance 

with 1065, 2005$ (thousands), As Incurred 

CLASS I CLASS II HANDHELD 

125 250 500 250 500 1000 

2008 9,600 

2009 1,700 1,700 1,700 

2010 1,700 1,700 1,700 

2011 

The number of engine families per Class and per useful life category were taken from 

EPA’s 2005 Certification Database. For Class I, the 2005 database lists 48 engine families from 

traditional companies and 38 newer engine families, accounting for 10 percent of engine sales, 

from companies which have been new to the marketplace since the time of the Phase 2 

rulemaking promulgation. Engine families still certified to Phase 1 (either through credits, 

small engine family flexibilities or averaging) were 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 IB 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. Costs for certifiers of LPG 

engines are covered in Section 6.2.4. 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. 

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 39 250 58 

250 17 500 20 

500 18 1000 58 

Certification costs include 1065 compliance and engine aging and emission testing for 

engine family certification compliance. The costs for 1065 compliance are determined as shown 

in Table 6.2-37. This analysis estimates test cells are upgraded two years prior to standard 

implementation. The total engine certification costs are calculated by taking the number of 

engine families from Table 6.2-38 and multiply them by the emission test and dynamometer 

aging costs from Table 6.2-23. This analysis estimates that engine certification costs are 

incurred one year prior to standard implementation as shown in Table 6.2-39. Total certification 

costs as recovered are presented in Table 6.2-40. 

Table 6.2-39: Engine Certification Costs As Incurred, (thousands) 

CLASS I CLASS II Handheld 

125 250 500 250 500 1000 

2008 9,600 

2009 $1,700 $1,700 $1,700 

2010 $1,700 $1,700 $1,700 $1,535 $854 $4,531 

2011 $686 $434 $745 

2012 

Table 6.2-40: Stream of Costs for
 

Engine Certification by Year As Recovered, (thousands)
 

CLASS I CLASS II 

125 250 500 250 500 1000 Handheld 

2010 2,681 

2011 875 698 1,657 2,681 

2012 654 588 669 875 698 1,657 2,681 

2013 654 588 669 875 698 1,657 2,681 

2014 654 588 669 875 698 1,657 2,681 

2015 654 588 669 875 698 1,657 

2016 654 588 669 

Fixed costs 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, catalyst development, 

and EFI development and application. All Class I engine families are assigned engine 

6-37 
Draft Regulatory Impact Analysis 

improvements and catalyst development costs. The number of engine families are taken from 

the 2005 EPA Certification Database. Table 6.2-41 presents the number of engine families 

estimated per technology package. Information on the number of cylinders per engine family 

and the number of manufacturers per Class was obtained from EPA’s 2005 Certification 

Database. 

Table 6.2-41: Estimates of the Number of Engine Families per Technology Package 

Technology/Useful Life 250 500 1000 

- One Cylinder Engine Improvements With Catalyst 45 13 28 

- Two or More Cylinders per Engine for Catalyst 11 4 24 

- Electronic Fuel Injection on Two or More Cylinder Engines 2 3 6 

Total Number of Engine Families 58 20 58 

Table 6.2-42: Total Fixed Costs as Incurred (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 1,888 12,838 6,419 6,796 21,301 6,653 20,102 

TOOLING 3,630 12,342 6,171 6,534 21,258 6,566 20,946 

TOTAL 5,518 25,180 12,590 13,330 42,559 13,219 41,048 

Table 6.2-43: Total Fixed Costs as Recovered (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 

2011 -- -- -- -- 11,504 3,574 11,088 

2012 1,475 6,811 3,405 3,606 11,504 3,574 11,088 

2013 1,475 6,811 3,405 3,606 11,504 3,574 11,088 

2014 1,475 6,811 3,405 3,606 11,504 3,574 11,088 

2015 1,475 6,811 3,405 3,606 11,504 3,574 11,088 

2016 1,475 6,811 3,405 3,606 -- -- – 

6-38 
Costs of Control 

Total fixed costs for Small SI exhaust emissions are shown in Table 6.2-44. 

Table 6.2-44: Certification and Technology Fixed Costs

 for Engines to Meet Proposed Exhaust Standards, As Recovered 

Class I Class II Handheld 

125 250 500 250 500 1000 

2010 2,681 

2011 12,380 4,272 12,745 2,681 

2012 8,940 3,993 4,275 12,380 4,272 12,745 2,681 

2013 8,940 3,993 4,275 12,380 4,272 12,745 2,681 

2014 8,940 3,993 4,275 12,380 4,272 12,745 2,681 

2015 8,940 3,993 4,275 12,380 4,272 12,745 

2016 8,940 3,993 4,275 

TOTAL 44,699 19,967 21,375 61,898 21,358 63,725 10,722 

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 

three unique models requiring clearly different redesign yields a number of 1239 redesigns. 

Table 6.2-22 contains equipment costs per equipment model and Table 6.2-45 contains the total 

equipment costs as incurred and recovered. 

Table 6.2-45: Total Class II Equipment Cost 

Incurred As Recovered 

2010 92,925,000 

2011 25,987,098 

2012 25,987,098 

2013 25,987,098 

2014 25,987,098 

2015 25,987,098 

TOTAL 129,935,492 

6.2.5.3 Operating Cost Savings 

The application of electronic fuel injection to an estimated additional 17.7 percent 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 6.2-46 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 

6-39 
Draft Regulatory Impact Analysis 

proposal. In calculating the fuel savings, we use a gasoline price of $1.81 per gallon without 

taxes.29 

Table 6.2-46: Fuel Savings from the Increased
 

Use of Electronic Fuel Injection on Class II Engines
 Year Gallons Fuel Savings $ 

2009 0 0 

2010 0 0 

2011 10,173,297 $18,454,361 

2012 18,376,598 $33,335,150 

2013 26,158,818 $47,452,096 

2014 31,081,817 $56,382,417 

2015 35,936,184 $65,188,238 

2016 39,616,047 $71,863,509 

2017 42,132,893 $76,429,068 

2018 44,068,991 $79,941,150 

2019 45,654,106 $82,816,549 

2020 47,024,456 $85,302,363 

2021 48,137,286 $87,321,037 

2022 49,132,949 $89,127,169 

2023 50,046,687 $90,784,690 

2024 50,928,776 $92,384,800 

2025 51,781,644 $93,931,901 

2026 52,622,410 $95,457,051 

2027 53,452,741 $96,963,273 

2028 54,275,859 $98,456,408 

2029 55,091,652 $99,936,257 

2030 55,900,128 $101,402,832 

2031 56,703,268 $102,859,728 

2032 57,503,764 $104,311,828 

2033 58,301,990 $105,759,810 

2034 59,098,563 $107,204,794 

2035 59,893,659 $108,647,097 

2036 60,685,412 $110,083,337 

2037 61,473,943 $111,513,733 

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 Compliance 

Class I Class II Handheld 

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 

0 

0 

122,084,986 

123,903,229 

125,684,375 

120,443,340 

122,188,014 

105,046,821 

106,693,720 

108,360,496 

110,016,644 

111,666,665 

113,304,422 

114,957,434 

116,608,057 

118,265,267 

119,936,019 

121,603,753 

123,267,260 

124,935,752 

126,604,442 

128,274,908 

129,944,548 

131,612,472 

133,279,206 

134,947,414 

136,615,966 

138,285,267 

0 

231,735,198 

234,740,187 

237,874,288 

240,917,033 

243,939,317 

158,329,126 

160,883,764 

163,430,833 

166,003,899 

168,556,986 

171,109,568 

173,642,413 

176,193,100 

178,745,385 

181,315,103 

183,887,430 

186,452,300 

189,013,944 

191,582,803 

194,152,312 

196,725,417 

199,294,850 

201,861,721 

204,427,738 

206,996,128 

209,564,630 

212,134,037 

2,680,612 

2,680,612 

2,680,612 

2,680,612 

2,680,612 

6-41 
Draft Regulatory Impact Analysis 

Table 6.2-48: Sales Weighted Average Per-Equipment 

Cost Estimates (Without Fuel Savings), 2005$

 Short Term Costs 

(years 1-5) per Class per 

Useful Life 

Class I Class II Handheld 

125 250 500 250 500 1000 

Variable 9.90 12.24 16.05 32.99 26.10 58.72 --

Fixed 1.10 4.41 6.86 6.42 18.17 26.51 0.30 

Total 11.00 16.66 22.91 39.41 44.27 85.23 0.30 

Long Term 9.13 11.39 14.92 27.84 22.16 47.22 0.00 

* Long term is without fixed costs and with learning, if applicable 

Table 6.2-49: Total Aggregate for 30 year Cost Analysis 

for Exhaust Emission Standard Compliance with Fuel Savings, 2005$ 

Year 

Exhaust Only 1065 Compliance 

Class I Class II Handheld

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 

$0 

$0 

$0 

$0 

$0 

$134,647,294 

$136,508,481 

$112,806,498 

$114,575,051 

$116,364,950 

$118,143,436 

$119,915,342 

$121,674,078 

$123,449,196 

$125,221,748 

$127,001,374 

$128,795,542 

$130,586,470 

$132,372,859 

$134,164,600 

$135,956,554 

$137,750,415 

$139,543,389 

$141,334,520 

$143,124,374 

$144,915,811 

$146,707,616 

$148,500,226 

0 

$213,280,837 

$201,405,037 

$190,422,192 

$184,534,617 

$178,751,079 

$86,465,617 

$84,454,696 

$83,489,683 

$83,187,350 

$83,254,623 

$83,788,531 

$84,515,244 

$85,408,410 

$86,360,585 

$87,383,202 

$88,430,379 

$89,489,027 

$90,557,536 

$91,646,546 

$92,749,480 

$93,865,690 

$94,983,022 

$96,101,911 

$97,222,944 

$98,349,031 

$99,481,294 

$100,620,305 

2,680,612 

2,680,612 

2,680,612 

2,680,612 

2,680,612 

6-42 
Costs of Control 

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 $265 million. The 

corresponding estimated annualized fuel savings due to the use of electronic fuel injection on 

Class II engines is $63 million. At a 3 percent discount rate, the estimated annualized cost to 

manufacturers for Small SI exhaust emission control, without fuel savings, is $273 million. The 

corresponding estimated annualized fuel savings due to the use of electronic fuel injection on 

Class II engines is $71 million. 

6.3 Exhaust Emission Control Costs for Outboard and Personal Watercraft 

Marine Engines 

This section presents our cost estimates for meeting the proposed exhaust emission 

standards for outboard and personal watercraft marine engines. 

Less than 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 proposed 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 those we are proposing, 

manufacturers have already started with design and testing efforts to meet our proposed 

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, since EPA’s proposed 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.30 Table 6.3-1 presents these power categories and the engine 

size we use to represent each category. 

6-43 
Draft Regulatory Impact Analysis 

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 
Draft 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 proposed 

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 
Draft 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 
Draft Regulatory Impact Analysis 

6.3.4 Catalysts 

We believe the proposed 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 proposed standards. In addition, manufacturers are likely to meet the 

proposed standards by selling more of their lower-emission engines, which are certified today. 

However, manufacturers may need to adjust engine calibrations to meet the proposed standard 

and collect further data to demonstrate compliance with the proposed 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 

6-51 
Draft Regulatory Impact Analysis 

the two-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. This cost is therefore 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 proposed standards will largely be met on average by phasing out 

old, high-emitting 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.31 

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.32 

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%) $77 $142 

6.3.7 Total OB/PWC Engine Costs 

As discussed above, we anticipate that manufacturers would meet the proposed 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.33 

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 proposed 

standards would require engine manufacturers to pay closer attention to emissions calibrations 

for their higher-emitting 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 
Draft 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 

$273 

$69 

$216 

$203 

$338 

$690 

$284 

$74 

$222 

$210 

$353 

$717 

$219 

$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 cost estimates described 

above by projected engine sales. Engine sales are based on estimates supplied by the National 

6-54 
Costs of Control 

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.34 Table 6.3-14 presents the projected 

costs of meeting the proposed exhaust emission standards over a 30-year time period, with and 

without the fuel savings. Fuel savings from the proposed 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 proposing to update 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 $108 million. The corresponding 

estimated annualized fuel savings due to more efficient engines is $57 million. At a 3 percent 

discount rate, the estimated annualized cost to manufacturers for OB/PWC exhaust emission 

control is $103 million. The corresponding estimated annualized fuel savings due to more 

efficient engines is $64 million. 

6-55 
Draft 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 

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 

2038

 $84,242,873 

$84,850,618 

$85,473,947 

$86,097,276 

$86,720,605 

$67,170,271 

$67,649,631 

$68,122,998 

$68,596,366 

$69,069,734 

$69,543,101 

$70,016,469 

$70,489,837 

$70,963,204 

$71,436,572 

$71,909,940 

$72,383,307 

$72,859,671 

$73,336,035 

$73,812,398 

$74,288,762 

$74,765,126 

$75,241,489 

$75,717,853 

$76,194,217 

$76,670,580 

$77,146,944 

$77,623,308 

$78,099,671 

$78,576,035 

$28,070,735 

$28,273,243 

$28,480,943 

$28,688,644 

$28,896,344 

$22,049,479 

$22,206,835 

$22,362,224 

$22,517,613 

$22,673,001 

$22,828,390 

$22,983,779 

$23,139,168 

$23,294,557 

$23,449,946 

$23,605,334 

$23,760,723 

$23,917,096 

$24,073,468 

$24,229,840 

$24,386,213 

$24,542,585 

$24,698,957 

$24,855,329 

$25,011,702 

$25,168,074 

$25,324,446 

$25,480,819 

$25,637,191 

$25,793,563 

$80,280,824 

$76,945,029 

$73,647,593 

$70,386,332 

$67,153,841 

$43,776,465 

$40,438,909 

$37,127,048 

$33,855,111 

$30,639,110 

$27,488,204 

$24,419,419 

$21,461,639 

$18,701,687 

$16,563,074 

$14,854,769 

$13,335,677 

$11,975,643 

$10,861,355 

$9,875,510 

$9,063,546 

$8,383,095 

$7,792,111 

$7,318,336 

$6,919,063 

$6,603,636 

$6,371,857 

$6,192,965 

$6,049,717 

$5,935,965 

$25,794,193 

$23,741,117 

$21,688,747 

$19,661,793 

$17,666,970 

$8,674,759 

$6,733,884 

$4,863,926 

$3,087,340 

$1,449,882 

$588,957 

$(4,321)

 $(464,863)

 $(835,954)

 $(1,140,064)

 $(1,376,955)

 $(1,557,763)

 $(1,693,743)

 $(1,784,708)

 $(1,830,521)

 $(1,842,333)

 $(1,854,144)

 $(1,865,948)

 $(1,877,773)

 $(1,889,590)

 $(1,901,401)

 $(1,913,212)

 $(1,925,031)

 $(1,936,841)

 $(1,948,650) 

6.4 Exhaust Emission Control Costs for Sterndrive/Inboard Marine 

Engines 

This section presents our cost estimates for meeting the proposed 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.35 

Because California ARB has adopted standards similar to those we are proposing, 

manufacturers have already started with design and testing efforts to meet our proposed 

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 proposed 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 proposed 

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 
Draft 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 proposed exhaust emission standards. However, in developing this proposal, 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 
Draft Regulatory Impact Analysis 

6.4.3 Catalysts 

We anticipate that manufacturers will use small three-way catalysts to meet the proposed 

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. This cost is therefore 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 proposed 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.36 We use the price of gasoline discussed earlier in this chapter. 

6-61 
Draft 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 103 

Lifetime Cost Savings $186 

Discounted Cost Savings (7%) $106 

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 proposed 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 fuel-injected 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 catalysts to all SD/I engines 

and costs for electronic fuel injection for engine models that are projected to be carbureted in 

2009. 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. Table 6.4-7 presents these 

6-62 
Costs of Control 

average per-engine cost estimates. To develop high-performance engine cost we considered that 

larger catalysts would be needed, even than the 8.1L engine, due to higher exhaust flow rates. 

Therefore, the variable costs were increased by 37 percent to account for this increase. Fixed 

costs 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 

$20

 $18 

$19 

$20 

$21 

$28 

$95 

$342

 $465 

$377 

$297 

$279 

$349 

$825 

$362

 $483 

$396 

$317 

$300 

$377

 $920 

$274

 $372 

$301 

$238 

$223 

$279 

$672 

6.4.7 SD/I Aggregate Costs 

Aggregate costs are calculated by multiplying the per-engine cost estimates described 

above by projected engine sales. 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.37 Table 6.4-8 presents the projected costs 

of the proposed 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 proposed 

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 $33 million. The corresponding estimated 

annualized fuel savings due to more efficient engine controls is $10 million. At a 3 percent 

discount rate, over 30 years, the estimated annualized cost to manufacturers for SD/I exhaust 

emission control is $31 million. The corresponding estimated annualized fuel savings due to 

more efficient engine controls is $11 million. 

6-63 
Draft Regulatory Impact Analysis 

Table 6.4-8: Projected 30-Year Aggregate Cost Stream for SD/I Engines 

Year Without Fuel Savings With Fuel Savings 

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 

2038

 $34,371,313 

$34,619,275 

$34,873,594 

$35,127,914 

$35,382,234 

$26,919,578 

$27,111,689 

$27,301,399 

$27,491,109 

$27,680,818 

$27,870,528 

$28,060,238 

$28,249,948 

$28,439,658 

$28,629,367 

$28,819,077 

$29,008,787 

$29,199,697 

$29,390,608 

$29,581,518 

$29,772,429 

$29,963,339 

$30,154,250 

$30,345,160 

$30,536,071 

$30,726,981 

$30,917,892 

$31,108,802 

$31,299,713 

$31,490,623 

$33,494,477 

$32,867,058 

$32,183,227 

$31,506,139 

$30,816,636 

$21,417,165 

$20,680,689 

$19,951,604 

$19,238,380 

$18,545,390 

$17,864,335 

$17,188,875 

$16,506,937 

$15,839,760 

$15,182,967 

$14,541,220 

$13,918,790 

$13,321,013 

$12,751,094 

$12,230,592 

$11,947,322 

$11,732,535 

$11,567,788 

$11,435,606 

$11,325,500 

$11,233,060 

$11,157,682 

$11,094,904 

$11,044,775 

$11,006,958 

6.5 Evaporative Emission Control Costs for Small SI Equipment 

This section presents our cost estimates for meeting the proposed evaporative emission 

standards for land-based equipment using small spark-ignition engines. 

In our analysis of the costs of the proposed 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 non6-64 
Costs of Control 

handheld (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 proposed 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.38,39,40 For baseline hose, we consider nitrile rubber 

hose such as that used to meet SAE J30 R7 recommendations. For handheld equipment, we 

consider the baseline hose 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 
Draft 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 

proposed 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 proposed 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 

6-66 
Costs of Control 

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 

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 fluorination41 and 

sulfonation.42 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).43 

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 $800,000.44 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 

6-67 
Draft Regulatory Impact Analysis 

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. 

6.5.2.2 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.45 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 $3,000,00046, 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 

proposed 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 

6-68 
Costs of Control 

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, 

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.47 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. 

6-69 
Draft Regulatory Impact Analysis 

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 proposed standards. Therefore, 

we 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.48,49,50 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.51 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.52 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.53 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.54,55 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 

6-70 
Costs of Control 

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 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-layer

a

: short term 

EVOH long term 

$4.13 

$2.01 

$4.08 

$1.98 

$3.80 

$1.75 

NA 

multi-layer

c

: short term 

PA11 long term 

NA NA NA $5.54 

$3.40 

multi-layer

c

: 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 
Draft 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 

proposing 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 proposed 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 proposed 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 
Draft 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 

proposed 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 proposed 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 4.9 28.6 

Lifetime Gallons Saved 0.2 0.8 4.7 

Lifetime Cost Savings $0.41 $1.46 $8.57 

Average Equipment Life [years] 4.2 5.3 5.9 

Discounted Cost Savings (7%) $0.40 $1.32 $5.98 

6.5.6 Total Small SI Equipment Costs 

We expect that Small SI manufacturers will use a variety of technologies to meet the 

proposed 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 proposed 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 
Draft 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. 

In the case where current equipment designs are such that the fuel in the tank does not 

heat up substantially during operation, equipment manufacturers would not need to add 

additional hardware for running loss control. However, we are not able to quantify what fraction 

of the equipment population this represents at this time. Therefore, we are applying the cost of 

the running loss system described above for all non-handheld equipment in our analysis. This 

cost approach presents a somewhat conservatively high cost of control for running loss. This 

running loss control system would also control diffusion from Small SI equipment. In some 

cases, manufacturers may choose to move the fuel tank further away from heat sources such as 

the engine or hydraulic system to meet the proposed running loss requirement (or insulate the 

tank). Presumably, manufacturers would not choose this option unless it were less expensive 

than the running loss control system described above. Therefore, we are not attempting to 

estimate the range of approaches that manufacturers may take to meet the proposed running loss 

requirements. 

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. 

6-76 
Costs of Control 

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

 $2.71

 $0.32 

$0.33 

$2.05 

$3.16

 $0.75 

$0.35 

$2.05 

$0.19 

$0.19 

$0 

$0

 $2.10

 $0.26 

$0.20 

$1.64 

$2.29

 $0.45 

$0.20 

$1.64 

Class II aggregate

 tank permeation

 hose permeation

 running loss 

$1.25 

$1.20 

$0.04 

$0

 $5.68

 $2.08 

$1.09 

$2.51 

$6.90

 $3.26 

$1.13 

$2.51 

$0.68 

$0.68 

$0 

$0

 $4.62

 $1.66 

$0.96 

$2.00 

$5.30

 $2.34 

$0.96 

$2.00 

6.5.7 Small SI Equipment Aggregate Costs 

Aggregate costs are calculated by multiplying the per-engine cost estimates described 

above by projected equipment sales. Fuel savings are calculated directly from the projected HC 

reductions due to the proposed evaporative emission standards. Table 6.5-8 presents the 

projected costs of the proposed 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 $67 million. The estimated 

corresponding annualized fuel savings due to control of evaporative emissions from Small SI 

equipment is $52 million. At a 3 percent discount rate, the estimated annualized cost to 

manufacturers for Small SI evaporative emission control is $70 million. The estimated 

corresponding annualized fuel savings due to control of evaporative emissions from Small SI 

equipment is $58 million. 

6-77 
Draft Regulatory Impact Analysis 

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 

2038

 $­

$5,714,115 

$5,909,315 

$6,017,988 

$7,848,826 

$7,981,700 

$6,909,877 

$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 

$9,503,051 

$3,869,095 

$3,938,646 

$4,008,024 

$4,080,278 

$34,157,324 

$32,774,886 

$33,321,924 

$33,866,041 

$34,402,748 

$26,950,398 

$27,372,435 

$27,799,282 

$28,223,637 

$28,646,477 

$29,066,350 

$29,489,883 

$29,912,857 

$30,337,439 

$30,765,267 

$31,192,359 

$31,618,433 

$32,045,711 

$32,473,046 

$32,900,804 

$33,328,357 

$33,755,498 

$34,182,354 

$34,609,570 

$35,036,864 

$35,464,338 

$35,891,721 

$6,281,721 

$6,394,682 

$6,508,249 

$39,786,661 

$40,469,354 

$39,835,064 

$40,503,217 

$41,167,585 

$33,342,748 

$33,879,410 

$34,414,535 

$34,954,723 

$35,491,162 

$36,027,436 

$36,559,874 

$37,095,737 

$37,631,938 

$38,171,542 

$38,711,628 

$39,250,255 

$39,788,258 

$40,327,667 

$40,867,213 

$41,407,443 

$41,946,957 

$42,485,978 

$43,024,838 

$43,564,162 

$44,103,498 

$44,643,012 

$45,182,425 

$­

$5,480,395 

$5,230,762 

$4,942,678 

$6,193,002 

$5,806,851 

$4,336,640 

$4,075,983 

$3,968,662 

$3,967,964 

$3,997,894 

$4,043,702 

$4,098,612 

$4,158,860 

$4,219,200 

$4,279,643 

$4,340,208 

$4,400,839 

$4,461,480 

$4,522,093 

$4,582,681 

$4,643,307 

$4,703,955 

$4,764,584 

$4,825,202 

$4,885,815 

$4,946,439 

$5,007,071 

$5,067,698 

$5,128,319 

$5,188,941 

$2,982,585 

$2,097,799 

$1,225,996 

$415,185 

$25,627,296 

$20,174,259 

$17,817,514 

$16,541,314 

$15,570,529 

$6,863,628 

$6,516,375 

$6,346,214 

$6,262,715 

$6,230,543 

$6,236,111 

$6,281,352 

$6,346,064 

$6,412,326 

$6,478,674 

$6,544,241 

$6,608,795 

$6,674,550 

$6,740,348 

$6,806,591 

$6,872,622 

$6,938,242 

$7,003,562 

$7,069,255 

$7,135,021 

$7,200,976 

$7,266,812 

$4,213,867 

$1,977,749 

$(258,757)

 $25,506,408 

$19,923,826 

$14,024,588 

$10,833,852 

$8,032,827 

$(2,641,523)

 $(4,071,321)

 $(5,142,350)

 $(5,931,671)

 $(6,542,467)

 $(6,972,441)

 $(7,317,102)

 $(7,598,592)

 $(7,856,488)

 $(8,091,169)

 $(8,313,604)

 $(8,526,931)

 $(8,733,177)

 $(8,932,174)

 $(9,125,631)

 $(9,314,633)

 $(9,502,186)

 $(9,687,202)

 $(9,869,734)

 $(10,050,377)

 $(10,228,844)

 $(10,405,188)

 $(10,580,702) 

6.6 Costs of Evaporative Emission Controls for Marine Vessels 

This section presents our cost estimates for meeting the proposed evaporative emission 

standards for marine vessels. 

To determine the cost impacts of the proposed 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 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 

6-78 
Costs of Control 

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.56 

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. 

Barrier fuel hose incremental costs estimates are based on costs of existing products used 

in marine and automotive applications.57,58,59,60,61 Because the manufacturing process is not 

fundamentally changed in adding a barrier layer, this cost is mostly the result of more expensive 

6-79 
Draft Regulatory Impact Analysis 

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 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 

about 30-50 percent of the material would be FKM which results in a material cost increase of 

about $0.90 per primer bulb. 

6-80 
Costs of Control 

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 fluorination62 and sulfonation.63 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 

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 

6-81 
Draft Regulatory Impact Analysis 

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.64 

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.65 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)66, 

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 

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 

6-82 
Costs of Control 

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.67 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.68 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.69,70 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 

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 

6-83 
Draft Regulatory Impact Analysis 

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 $2,500.71 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. 

6-84 
Costs of Control 

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 proposed 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.72 

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 

6-85 
Draft Regulatory Impact Analysis 

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 price73 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.74 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 

6-86 
Costs of Control 

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 proposed reduction in 

6-87 
Draft Regulatory Impact Analysis 

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 proposed 

evaporative emission standards. 

Table 6.6-5: Projected Evaporative Fuel Savings for Marine Vessels 

Portable PWC Installed 

Evaporative HC Reduced [lbs/life] 88 58 247 

Lifetime Gallons Saved 14 9.4 41 

Lifetime Cost Savings $26 $17 $74 

Average Equipment Life [years] 12.7 9.9 17 

Discounted Cost Savings (7%) $18 $13 $45 

6.6.6 Total Marine Vessel Costs 

We expect that marine vessel manufactures will make use of a variety of technologies to 

meet the proposed 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 proposed 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 

6-88 
Costs of Control 

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-engine cost estimates described 

above by projected vessel sales. 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.75 Fuel savings are calculated directly from the 

projected HC reductions due to the proposed evaporative emission standards. Table 6.6-7 

presents the projected costs of the proposed 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 

6-89 
Draft Regulatory Impact Analysis 

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 proposing to update 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 $26 million. The estimated 

corresponding annualized fuel savings due to control of evaporative emissions from boats is $25 

million. At a 3 percent discount rate, the estimated annualized cost to manufacturers for marine 

evaporative emission control is $26 million. The estimated corresponding annualized fuel 

savings due to control of evaporative emissions from boats is $29 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 

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 

2038

 $1,964,334 

$1,978,506 

$1,993,040 

$2,007,575 

$2,022,109 

$907,533 

$914,009 

$920,405 

$926,801 

$933,196 

$939,592 

$945,987 

$952,383 

$958,779 

$965,174 

$971,570 

$977,966 

$984,402 

$990,838 

$997,274 

$1,003,710 

$1,010,146 

$1,016,582 

$1,023,018 

$1,029,455 

$1,035,891 

$1,042,327 

$1,048,763 

$1,055,199 

$1,061,635 

$1,509,992 

$1,520,885 

$1,532,058 

$1,543,230 

$1,554,403 

$942,509 

$949,235 

$955,877 

$962,520 

$969,162 

$975,804 

$982,446 

$989,088 

$995,730 

$1,002,372 

$1,009,014 

$1,015,657 

$1,022,341 

$1,029,025 

$1,035,709 

$1,042,393 

$1,049,077 

$1,055,761 

$1,062,446 

$1,069,130 

$1,075,814 

$1,082,498 

$1,089,182 

$1,095,866 

$1,102,551 

$2,379,818 

$13,357,033 

$25,957,390 

$26,146,688 

$26,335,985 

$26,130,013 

$24,043,965 

$22,304,923 

$22,459,914 

$22,614,905 

$22,769,895 

$22,924,886 

$23,079,877 

$23,234,867 

$23,389,858 

$23,544,849 

$23,699,839 

$23,855,811 

$24,011,783 

$24,167,754 

$24,323,726 

$24,479,698 

$24,635,669 

$24,791,641 

$24,947,612 

$25,103,584 

$25,259,556 

$25,415,527 

$25,571,499 

$25,727,471 

$1,696,777 

$1,379,654 

$1,056,961 

$625,447 

$227,276 

$(1,293,196)

 $(1,691,753)

 $(2,083,707)

 $(2,472,693)

 $(2,851,048)

 $(3,222,042)

 $(3,570,455)

 $(3,889,105)

 $(4,166,588)

 $(4,376,235)

 $(4,557,295)

 $(4,719,344)

 $(4,869,408)

 $(5,003,979)

 $(5,128,330)

 $(5,241,868)

 $(5,346,193)

 $(5,435,660)

 $(5,518,237)

 $(5,591,777)

 $(5,652,081)

 $(5,706,100)

 $(5,755,039)

 $(5,802,545)

 $(5,848,308)

 $1,460,514 

$1,416,312 

$1,212,780 

$1,006,435 

$810,625 

$(4,533)

 $(197,528)

 $(384,702)

 $(566,360)

 $(739,824)

 $(887,378)

 $(1,018,989)

 $(1,095,610)

 $(1,152,037)

 $(1,197,840)

 $(1,236,005)

 $(1,268,302)

 $(1,295,056)

 $(1,316,950)

 $(1,334,722)

 $(1,348,643)

 $(1,359,565)

 $(1,368,227)

 $(1,376,889)

 $(1,385,552)

 $(1,394,215)

 $(1,402,877)

 $(1,411,539)

 $(1,420,202)

 $(1,428,864)

 $1,930,889 

$11,782,975 

$23,138,203 

$21,066,108 

$19,068,161 

$16,685,413 

$12,428,196 

$8,525,783 

$6,535,757 

$4,561,432 

$2,607,303 

$667,034 

$(1,268,679)

 $(3,182,282)

 $(5,033,988)

 $(6,730,209)

 $(8,298,019)

 $(9,680,934)

 $(10,889,215)

 $(11,989,416)

 $(12,990,968)

 $(13,836,968)

 $(14,605,420)

 $(15,226,617)

 $(15,772,673)

 $(16,251,345)

 $(16,665,147)

 $(17,031,083)

 $(17,357,227)

 $(17,650,084) 

6-90 
Costs of Control 

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 

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 

2038

 $4,022,410 

$10,590,973 

$17,386,587 

$17,513,381 

$17,640,175 

$16,093,724 

$14,852,627 

$13,701,910 

$13,797,121 

$13,892,332 

$13,987,542 

$14,082,753 

$14,177,964 

$14,273,174 

$14,368,385 

$14,463,596 

$14,558,807 

$14,654,620 

$14,750,433 

$14,846,247 

$14,942,060 

$15,037,873 

$15,133,687 

$15,229,500 

$15,325,313 

$15,421,127 

$15,516,940 

$15,612,753 

$15,708,567 

$15,804,380

 $1,509,992 

$1,520,885 

$1,532,058 

$1,543,230 

$1,554,403 

$942,509 

$949,235 

$955,877 

$962,520 

$969,162 

$975,804 

$982,446 

$989,088 

$995,730 

$1,002,372 

$1,009,014 

$1,015,657 

$1,022,341 

$1,029,025 

$1,035,709 

$1,042,393 

$1,049,077 

$1,055,761 

$1,062,446 

$1,069,130 

$1,075,814 

$1,082,498 

$1,089,182 

$1,095,866 

$1,102,551 

$321,743 

$4,744,565 

$10,563,843 

$10,640,881 

$10,717,919 

$10,943,821 

$10,105,347 

$9,523,418 

$9,589,594 

$9,655,769 

$9,721,945 

$9,788,120 

$9,854,296 

$9,920,472 

$9,986,647 

$10,052,823 

$10,118,998 

$10,185,593 

$10,252,187 

$10,318,782 

$10,385,376 

$10,451,970 

$10,518,565 

$10,585,159 

$10,651,754 

$10,718,348 

$10,784,942 

$10,851,537 

$10,918,131 

$10,984,726

 $3,335,872 

$8,658,576 

$14,085,375 

$12,010,652 

$10,037,991 

$6,406,222 

$3,082,863 

$(139,724)

 $(2,098,191)

 $(4,033,918)

 $(5,946,347)

 $(7,826,103)

 $(9,665,614)

 $(11,445,138)

 $(13,099,198)

 $(14,574,287)

 $(15,910,006)

 $(17,057,085)

 $(18,024,386)

 $(18,887,029)

 $(19,667,131)

 $(20,343,387)

 $(20,957,927)

 $(21,506,331)

 $(21,999,412)

 $(22,427,494)

 $(22,797,796)

 $(23,125,550)

 $(23,420,202)

 $(23,687,967)

 $1,460,514 

$1,416,312 

$1,212,780 

$1,006,435 

$810,625 

$(4,533)

 $(197,528)

 $(384,702)

 $(566,360)

 $(739,824)

 $(887,378)

 $(1,018,989)

 $(1,095,610)

 $(1,152,037)

 $(1,197,840)

 $(1,236,005)

 $(1,268,302)

 $(1,295,056)

 $(1,316,950)

 $(1,334,722)

 $(1,348,643)

 $(1,359,565)

 $(1,368,227)

 $(1,376,889)

 $(1,385,552)

 $(1,394,215)

 $(1,402,877)

 $(1,411,539)

 $(1,420,202)

 $(1,428,864)

 $291,795 

$4,504,054 

$10,109,789 

$9,680,903 

$9,257,446 

$8,985,995 

$7,653,579 

$6,581,800 

$6,161,255 

$5,744,302 

$5,331,609 

$4,922,682 

$4,507,829 

$4,096,269 

$3,688,976 

$3,286,783 

$2,892,643 

$2,506,743 

$2,131,192 

$1,769,284 

$1,434,296 

$1,160,226 

$916,847 

$761,478 

$634,962 

$524,068 

$426,549 

$339,427 

$260,430 

$189,575 

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 

6-91 
Draft Regulatory Impact Analysis 

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.76 Although 2004 and 

2005 gasoline prices are available in published reports, 2006 gasoline prices are not expected to 

be reported until mid 2007. However, gasoline price samples throughout the year are available 

on-line.77 Based on this information, the national average fuel price, with taxes, from January to 

October 2006 was $2.68 per gallon. 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 $2.29/gallon for 2006. 

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 2006. 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 2006 price were used, the estimated fuel savings would have been about 

27 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 $1.80 $1.41 

2005 $2.20 $1.81 

2006 (through October) $2.68 $2.29 

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Costs of Control 

6.7.2 Variation in Precious Metal Prices 

Precious metal prices for Platinum and Rhodium have increased over the past 5 years.79 

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 6.7-2. 

Table 6.7-2: 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 6.7-3 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. 

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Draft Regulatory Impact Analysis 

Table 6.7-3: 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 

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 presented for each of the engine sizes used above for the primary cost analysis, are 

near term costs without fuel savings. 

Table 6.7-4: 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 Aggregate 

Primary Analysis $483 $396 $317 $300 $377 $360 

September 2006 Precious Metal Prices 

Cost 

Increase 

% Increase 

$511 

$28 

5% 

$417 

$21 

5% 

$342 

$24 

7% 

$328 

$28 

8% 

$416 

$39 

9% 

$386 

$25 

7% 

10 Year Average Precious Metal Prices 

Cost 

Increase 

% Increase 

$479 

-$4 

-1% 

$393 

-$3 

-1% 

$314 

-$4 

-1% 

$296 

-$4 

-1% 

$371 

-$6 

-2% 

$357 

-$4 

-1% 

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Costs of Control 

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 6.7-5. 

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Draft Regulatory Impact Analysis 

Table 6.7-5: Costs for Equipment Manufacturers 

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 proposal 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 6.7-6 compares 

the estimated costs of catalysts and fuel injection. 

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Costs of Control 

Table 6.7-6: 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 

Injection 

$103,020 $103,020 $103,020 

Difference -$261,113 -$261,113 -$261,113 

The resultant change in cost/equipment for this is shown in Table 6.7-7. 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 6.7-7
 

Sales Weighted Average Cost Per Class II Equipment
 

250 500 1000 

Short Term (first year - includes fixed cost)

 Proposal $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)

 Proposal $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% 

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Draft Regulatory Impact Analysis 

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. 

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. 

6-98 
Costs of Control 

Table 6.7-8: 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 

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 6.7-9: 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% 

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Draft Regulatory Impact Analysis 

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 

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. 

6-100 
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. 

6-101 
Draft 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. 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. 

30. “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. 

31. 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. 

6-102 
Costs of Control 

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. “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. 

34. Samulski, M., “Marine SI Sales and Price Estimates,” U.S. EPA, August 30, 2004, Docket Identification EPAHQ-OAR-2004-0008-0448. 

35. “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. 

36. “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. 

37. Samulski, M., “Marine SI Sales and Price Estimates,” U.S. EPA, August 30, 2004, Docket Identification EPAHQ-OAR-2004-0008-0448. 

38. Trident Marine Hose, “Retail Price List 2001,” Docket Identification EPA-HQ-OAR-2004-0008-0226. 

39. 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. 

40. “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. 

41. “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. 

42. “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. 

43. “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. 

44. “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. 

45. “Plastic News,” Resin Pricing for November 8, 2004, www.plasticnews.com, Docket Identification EPA-HQOAR-2004-0008-0442. 

46. 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. 

47. “Plastic News,” Resin Pricing for November 8, 2004, www.plasticnews.com, Docket Identification EPA-HQOAR-2004-0008-0442. 

48. “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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Draft Regulatory Impact Analysis 

49. 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. 

50. 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. 

51. “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. 

52. “Plastic News,” Resin Pricing for November 8, 2004, www.plasticnews.com, Docket Identification EPA-HQOAR-2004-0008-0442. 

53. “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. 

54. 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. 

55. 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. 

56. “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. 

57. Trident Rubber Inc., “Trident Marine Hose, Retail Price List 2001,” Docket Identification EPA-HQOAR-2004-0008-0226. 

58. 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. 

59. “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. 

60. Lawrence Marine; NovaFlex Group, “Industrial Price List: Marine Products,” October 15, 2004, Docket 

Identification EPA-HQ-OAR-2004-0008-0439. 

61. Trident Rubber Inc., “Trident Marine Hose, Retail Price List, October 2005,” Docket Identification EPA-HQOAR-2004-0008-0444. 

62. “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. 

63. “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. 

64. “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. 

65. “Plastic News,” Resin Pricing for November 8, 2004, www.plasticnews.com, Docket Identification EPA-HQOAR-2004-0008-0442. 

6-104 
Costs of Control 

66. 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. 

67. “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. 

68. “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. 

69. 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. 

70. 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. 

71. “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. 

72. 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. 

73. Trident Marine Hose, “Retail Price List 2001,” Docket Identification EPA-HQ-OAR-2004-0008-0226. 

74. “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. 

75. Samulski, M., “Marine SI Sales and Price Estimates,” U.S. EPA, August 30, 2004, Docket Identification EPAHQ-OAR-2004-0008-0448. 

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, “Retail Gasoline Historical Prices,” downloaded from 

http://www.eia.doe.gov/oil_gas/petroleum/data_publications/wrgp/mogas_history.html, on October 25, 2006, Docket 

Identification EPA-HQ-OAR-2004-0008-0450. 

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. Johnson Matthey, “Platinum Today,” www.platinum.matthey.com, downloaded October 25, 2006, Docket 

Identification EPA-HQ-OAR-2004-0008-0422. 

6-105 

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 
Draft 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 $3,315 1,785,000 $1860 

Evaporative $829 1,074,000 $770 

Exhaust + Evap $4,144 2,860,000 $1450 

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 $2,539 1,785,000 $1420 

Evaporative $186 1,074,000 $170 

Exhaust + Evap $2,725 2,860,000 $950 

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 $1,748 2,140,000 $820 

Evaporative $324 510,000 $630 

Exhaust + Evap $2,071 2,650,000 $780 

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 $917 2,140,000 $430 

Evaporative $18 510,000 $35 

Exhaust + Evap $934 2,650,000 $350 

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 
Draft 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 $5,502 3,228,000 $1,700 

Evaporative $1,367 1,893,000 $720 

Exhaust + Evap $6,869 5,121,000 $1,340 

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 $4,109 3,228,000 $1,270 

Evaporative $234 1,893,000 $120 

Exhaust + Evap $4,342 5,121,000 $850 

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 $2,632 3,824,000 $690 

Evaporative $505 954,000 $530 

Exhaust + Evap $3,137 4,778,000 $660 

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 $1,145 3,824,000 $300 

Evaporative ($66) 954,000 ($70) 

Exhaust + Evap $1,079 4,778,000 $230 

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 

2001 NHH Engines Phase 2 

1998 Marine SI engines 

2004 Comm Marine CI 

2007 Large SI exhaust 

2006 ATV exhaust 

2006 off-highway motorcycle 

2006 recreational marine CI 

2010 snowmobile 

2006 <50cc highway motorcycle 

2010 Class 3 highway motorcycle 

840 

neg* 

1900 

200 

80 

300 

290 

700 

1430 

1860 

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 

7-5 
Draft Regulatory Impact Analysis 

SI and recreational Marine SI standards fall within the range of these other programs. Some 

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 
___________________________________________________________________________Cost-Benefit Analysis 

CHAPTER 8: Cost-Benefit Analysis 

8.1 Overview 

Mobile sources are significant contributors to air pollutant emissions across the country 

and into the future. The Agency has determined that these emissions cause or contribute to air 

pollution which may reasonably be anticipated to endanger public health or welfare, and is 

therefore establishing standards to control these emissions. The health- and environmentallyrelated effects associated with these emissions are a classic example of an externality-related 

market failure. An externality occurs when one party's actions impose uncompensated costs on 

another party. The proposed Small SI and Marine SI engine standards will help correct this 

market failure. 

EPA is required by Executive Order (E.O.) 12866 to estimate the benefits and costs of 

major new pollution control regulations. Accordingly, the analysis presented here attempts to 

answer three questions: (1) what are the physical health and welfare effects of changes in 

ambient air quality resulting from particulate matter (PM) and ozone precursor emission 

reductions (direct PM, NOx and VOC)? (2) what is the monetary value of the changes in these 

effects attributable to the proposed rule? and (3) how do the monetized benefits compare to the 

costs? It constitutes one part of EPA’s thorough examination of the relative merits of this 

regulation. 

This chapter presents our analysis of the health and environmental benefits that can be 

expected to occur as a result of the proposed standards throughout the period from initial 

implementation through 2030. Nationwide, the engines subject to the proposed emission 

standards in this rule are a significant source of mobile source air pollution. The proposed 

standards would reduce exposure to VOC, direct PM2.5, NOx and CO emissions and help avoid a 

range of adverse health effects associated with ambient ozone and PM2.5 levels. In addition, the 

proposed standards would help reduce exposure to CO, air toxics, and PM2.5 for persons who 

operate or who work with or are otherwise active in close proximity to these engines. 

The analysis presented in this chapter uses a methodology generally consistent with 

benefits analyses performed for the recent analysis of the the Clean Air Nonroad Diesel Rule 

(CAND) and the Mobile Source Air Toxics Rule (MSAT).1,2 To the extent possible, we also 

incorporate benefits analysis methods consistent with the approach used in the recent RIA for the 

PM NAAQS.3

 For this reason, the current chapter avoids repeating this information and refers to 

the appropriate sections of each RIA. The benefits analysis relies on two major components: 

1) 

2) 

Calculation of the impact of the proposed standards on the national direct PM and NOx 

emissions inventories for two future years (2020 and 2030). 

A benefits analysis to determine the changes in human health, both in terms of physical 

effects and monetary value, based on a PM benefits transfer approach that scales CAND 

results (see Section 8.2). 

8-1 
 
Draft Regulatory Impact Analysis__________________________________________________________________ 

It should be noted that since the CAND rule, EPA’s Office of Air and Radiation (OAR) has 

adopted a different format for its benefits analysis in which characterization of uncertainty is 

integrated into the main benefits analysis. The benefits scaling approach used in the analysis of 

the proposed standards limits our ability to integrate uncertainty into the main analysis. For the 

benefits analysis of the final standards, we will adopt this integrated uncertainty approach. 

Please see the PM NAAQS RIA for an indication of the uncertainty present in the base estimate 

of benefits and the sensitivity of our results to the use of alternative concentration-response 

functions. 

A wide range of human health and welfare effects are linked to the emissions of VOCs, 

direct PM and NOx and the resulting impact on ambient concentrations of ozone and PM2.5. 

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 shorterterm (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, while ozone can adversely affect 

the agricultural and forestry sectors by decreasing yields of crops and forests. 

EPA typically quantifies PM- and ozone-related benefits in its regulatory impact analyses 

(RIAs) when possible. In the analysis of past air quality regulations, ozone-related benefits have 

included morbidity endpoints and welfare effects such as damage to commercial crops. EPA has 

not recently included a separate and additive mortality effect for ozone, independent of the effect 

associated with fine particulate matter. For a number of reasons, including 1) advice from the 

Science Advisory Board (SAB) Health and Ecological Effects Subcommittee (HEES) that EPA 

consider the plausibility and viability of including an estimate of premature mortality associated 

with short-term ozone exposure in its benefits analyses and 2) conclusions regarding the 

scientific support for such relationships in EPA’s 2006 Air Quality Criteria for Ozone and 

Related Photochemical Oxidants (the CD), EPA is in the process of determining how to 

appropriately characterize ozone-related mortality benefits within the context of benefits 

analyses for air quality regulations. As part of this process, we are seeking advice from the 

National Academy of Sciences (NAS) regarding how the ozone-mortality literature should be 

used to quantify the reduction in premature mortality due to diminished exposure to ozone, the 

amount of life expectancy to be added and the monetary value of this increased life expectancy 

in the context of health benefits analyses associated with regulatory assessments. In addition, the 

Agency has sought advice on characterizing and communicating the uncertainty associated with 

each of these aspects in health benefit analyses. 

Since the NAS effort is not expected to conclude until 2008, the agency is currently 

deliberating how best to characterize ozone-related mortality benefits in its rulemaking analyses 

in the interim. For the analysis of the proposed locomotive and marine standards, we do not 

quantify an ozone mortality benefit. So that we do not provide an incomplete picture of all of the 

benefits associated with reductions in emissions of ozone precursors, we have chosen not to 

8-2 
 
___________________________________________________________________________Cost-Benefit Analysis 

include an estimate of total ozone benefits in the proposed RIA. By omitting ozone benefits in 

this proposal, we acknowledge that this analysis underestimates the benefits associated with the 

proposed standards. Our analysis, however, indicates that the rule's monetized PM2.5 benefits 

alone substantially exceed our estimate of the costs. 

Table 8.1-1 summarizes the annual monetized health and welfare benefits associated with 

the proposed standards for two years, 2020 and 2030. The PM2.5 benefits are scaled based on 

relative changes in direct PM and NOx emissions between this rule and the proposed Clean Air 

Nonroad Diesel (CAND) rule.A As explained in Section 8.2.1 of this chapter, the PM2.5 benefits 

scaling approach is limited to those studies, health impacts, and assumptions that were used in 

the proposed CAND analysis. As a result, PM-related premature mortality is based on the 

updated analysis of the American Cancer Society cohort (ACS; Pope et al., 2002). However, it is 

important to note that since the CAND rule, EPA’s Office of Air and Radiation (OAR) has 

adopted a different format for its benefits analysis in which characterization of the uncertainty in 

the concentration-response function is integrated into the main benefits analysis. Within this 

context, additional data sources are available, including a recent expert elicitation and updated 

analysis of the Six-Cities Study cohort (Laden et al., 2006). Please see the PM NAAQS RIA for 

an indication of the sensitivity of our results to use of alternative concentration-response 

functions. 

The analysis presented here assumes a PM threshold of 3 μg/m3

, equivalent to 

background. Through the RIA for CAIR, EPA’s consistent approach had been to model 

premature mortality associated with PM exposure as a nonthreshold effect; that is, with harmful 

effects to exposed populations modeled regardless of the absolute level of ambient PM 

concentrations. This approach had been supported by advice from EPA’s technical peer review 

panel, the Science Advisory Board’s Health Effects Subcommittee (SAB-HES). However, 

EPA’s most recent PM2.5 Criteria Document concludes that “the available evidence does not 

either support or refute the existence of thresholds for the effects of PM on mortality across the 

range of concentrations in the studies,” (p. 9-44).4 Furthermore, in the RIA for the PM NAAQS 

we used a threshold of 10 μg/m3

 based on recommendations by CASAC for the Staff Paper 

analysis. We consider the impact of a potential, assumed threshold in the PM-mortality 

concentration response function in Section 8.6.2.2 of the RIA. 

A Due to time and resource constraints, EPA scaled the final CAND benefits estimates from the benefits estimated 

for the CAND proposal. The scaling approach used in that analysis, and applied here, is described in the RIA for the 

final CAND rule.2 

8-3 
 
Draft Regulatory Impact Analysis__________________________________________________________________ 

Table 8.1-1. Estimated Monetized PM-Related Health Benefits of the Proposed Standards 

Total Benefitsa, b, c (billions 2003$) 

2020 2030 

Using a 3% discount rate 

Using a 7% discount rate 

$2.1 + B 

$1.9 + B 

$3.4 + B 

$3.1 + B a Benefits include avoided cases of mortality, chronic illness, and other morbidity health endpoints. PM-related 

mortality benefits estimated using an assumed PM threshold at background levels (3 μg/m3

). There is 

uncertainty about which assumed threshold to use and this may impact the magnitude of the total benefits 

estimate. For a more detailed discussion of this issue, please refer to Section 8.6.2.2 of the RIA. b For notational purposes, unquantified benefits are indicated with a “B” to represent the sum of additional 

monetary benefits and disbenefits. A detailed listing of unquantified health and welfare effects is provided in 

Table 8.1-2 of the RIA. c Results reflect the use of two different discount rates: 3 and 7 percent, which are recommended by EPA’s 

Guidelines for Preparing Economic Analyses5

 and OMB Circular A-4.

6

 Results are rounded to two significant 

digits for ease of presentation and computation. 

Table 8.1-2 lists the full complement of human health and welfare effects associated with 

PM, ozone and air toxics, and identifies those effects that are quantified for the primary estimate 

and those that remain unquantified because of current limitations in methods or available data. 

Table 8.1-2. Human Health and Welfare Effects of Pollutants Affected by the Proposed 

Standards 

Quantified and Monetized in Base 

Pollutant/Effect Estimatesa Unquantified Effects - Changes in: 

PM/Healthb Premature mortality based on cohort Premature mortality: short-term exposuresd 

study estimatesc Subchronic bronchitis cases 

Bronchitis: chronic and acute Low birth weight 

Hospital admissions: respiratory Pulmonary function 

and cardiovascular Chronic respiratory diseases other than chronic bronchitis 

Emergency room visits for asthma Nonasthma respiratory emergency room visits 

Nonfatal heart attacks (myocardial UVb exposure (+/-)e 

infarction) 

Lower and upper respiratory illness 

Minor restricted-activity days 

Work loss days 

Asthma exacerbations (asthmatic 

population) 

Respiratory symptoms (asthmatic 

population) 

Infant mortality 

8-4 
 
___________________________________________________________________________Cost-Benefit Analysis 

Pollutant/Effect 

Quantified and Monetized in Base 

Estimatesa Unquantified Effects - Changes in: 

PM/Welfare Visibility in Southeastern Class I areas 

Visibility in northeastern and Midwestern Class I areas 

Household soiling 

Visibility in western U.S. Class I areas 

Visibility in residential and non-Class I areas 

UVb exposure (+/-)e 

Ozone/Healthf Premature mortality: short-term exposuresg 

Hospital admissions: respiratory 

Emergency room visits for asthma 

Minor restricted-activity days 

School loss days 

Asthma attacks 

Cardiovascular emergency room visits 

Acute respiratory symptoms 

Chronic respiratory damage 

Premature aging of the lungs 

Nonasthma respiratory emergency room visits 

UVb exposure (+/-)e 

Ozone/Welfare Decreased outdoor worker productivity 

Yields for: 

 - Commercial forests 

 - Fruits and vegetables, and 

 - Other commercial and noncommercial crops 

Damage to urban ornamental plants 

Recreational demand from damaged forest aesthetics 

Ecosystem functions 

UVb exposure (+/-)e 

MSAT Healthh Cancer (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) 

Reproductive and developmental effects (1,3-butadiene) 

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) 

MSAT Welfareh Direct toxic effects to animals 

Bioaccumulation in the food chain 

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 proposed standards. 

8-5 
Draft Regulatory Impact Analysis__________________________________________________________________ 

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).7 

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. See Section 8.5.3. for more details. f In addition to primary economic endpoints, there are a number of biological responses that have been associated 

with ozone health including increased airway responsiveness to stimuli, inflammation in the lung, acute 

inflammation and respiratory cell damage, and increased susceptibility to respiratory infection. The public health 

impact of these biological responses may be partly represented by our quantified endpoints. g EPA sponsored a series of meta-analyses of the ozone mortality epidemiology literature, published in the July 2005 

volume of the journal Epidemiology, which found that short-term exposures to ozone may have a significant effect 

on daily mortality rates, independent of exposure to PM. EPA is currently considering how to include an estimate of 

ozone mortality in its benefits analyses. h

 The categorization of unquantified toxic health and welfare effects is not exhaustive. 

Figure 8.1-1 illustrates the major steps in the PM benefits analysis. Given the change in 

direct PM and NOx emissions modeled for the proposed standards, we use a benefits transfer 

approach to scale PM benefits estimated for the CAND analysis (see Section 8.2 for a description 

of the scaling approach). For the CAND analysis, EPA ran a sophisticated photochemical air 

quality model, the Regional Modeling System for Aerosols and Deposition (REMSAD), to 

estimate baseline and post-control ambient concentrations of PM for each future year (2020 and 

2030). The estimated changes in ambient concentrations were then combined with population 

projections to estimate population-level potential exposures to changes in ambient 

concentrations. Changes in population exposure to ambient air pollution were then input to 

impact functionsB to generate changes in the incidence of health effects. The resulting changes 

in incidence were then assigned monetary values, taking into account adjustments to values for 

growth in real income out to the year of analysis (values for health and welfare effects are in 

general positively related to real income levels). Values for individual health and welfare effects 

were summed to obtain an estimate of the total monetary value of the changes in emissions. 

Finally, we scale the CAND results to reflect the magnitude of the direct PM and NOx emissions 

changes we estimate will occur as a result of the proposed standards. 

Benefits estimates calculated for the CAND analysis, and scaled for the proposed 

B

 The term “impact function” as used here refers to the combination of a) an effect estimate obtained from the 

epidemiological literature, b) the baseline incidence estimate for the health effect of interest in the modeled 

population, c) the size of that modeled population, and d) the change in the ambient air pollution metric of interest. 

These elements are combined in the impact function to generate estimates of changes in incidence of the health 

effect. The impact function is distinct from the C-R function, which strictly refers to the estimated equation from 

the epidemiological study relating incidence of the health effect and ambient pollution. We refer to the specific 

value of the relative risk or estimated coefficients in the epidemiological study as the “effect estimate.” In 

referencing the functions used to generate changes in incidence of health effects for this RIA, we use the term 

“impact function” rather than C-R function because “impact function” includes all key input parameters used in the 

incidence calculation. 

8-6 
 
___________________________________________________________________________Cost-Benefit Analysis 

standards, were generated using the Environmental Benefits Mapping and Analysis Program 

(BenMAP). BenMAP is a computer program developed by EPA that integrates a number of the 

modeling elements used in previous RIA’s (e.g., interpolation functions, population projections, 

health impact functions, valuation functions, analysis and pooling methods) to translate modeled 

air concentration estimates into health effect incidence estimates and monetized benefit 

estimates. Interested parties may wish to consult the webpage 

http://www.epa.gov/ttn/ecas/benmodels.html for more information. 

Figure 8.1-1. Key Steps in Air Quality Modeling Based Benefits Analysis 

All of the benefit estimates for the proposed control options in this analysis are based on 

an analytical structure and sequence similar to that used in the benefits analyses for the CAND 

final rule, the CAIR rule, and, when feasible, the final PM NAAQS analysis.C By adopting the 

major design elements, models, and assumptions developed in recent RIAs, we rely on methods 

that have already received extensive review by the independent Science Advisory Board (SAB), 

C

 See: Clean Air Nonroad Diesel final rule (69 FR 38958, June 29, 2004); Clean Air Interstate final rule (70 FR 

25162, May 12, 2005); PM NAAQS (71 FR 61144, Oct. 17, 2006). 

8-7 
 
Draft Regulatory Impact Analysis__________________________________________________________________ 

by the public, and by other federal agencies. In addition, we will be working through the next 

section 812 prospective study to enhance our methods.D 

This chapter is organized as follows. In Section 8.2, we provide an overview of the air 

quality impacts modeled for the proposed standards that are used as inputs to the benefits 

analysis. In Section 8.3, we document key differences between this benefits analysis and the 

benefits analysis completed for the final CAIR and CAND rules. This section also presents and 

discusses the key inputs and methods used in the benefits analysis. In Section 8.4, we report the 

results of the analysis for human health and welfare effects. Section 8.5 qualitatively describes 

benefits categories that are omitted from this analysis, due either to inadequate methods or 

resources. Section 8.6 discusses how we incorporate uncertainty into our analysis. Section 8.7 

discusses the health-based cost-effectiveness analysis for the proposed standards. Finally, in 

Section 8.8, we present a comparison of the costs and benefits associated with the proposed 

standards. 

8.2 Air Quality Impacts 

This section summarizes the methods for and results of estimating air quality for the 2020 

and 2030 base case and proposed control scenario for the purposes of the benefits analysis. EPA 

has focused on the health, welfare, and ecological effects that have been linked to ambient 

changes in PM2.5 related to direct PM and NOx emission reductions estimated to occur due to the 

proposed standards. We do this by scaling the modeled relationship between emissions and 

ambient PM concentrations observed for the CAND analysis.8 

8.2.1 PM Air Quality Impact Estimation 

To estimate PM2.5 benefits from the proposed standards, we rely on a benefits transfer 

technique. The benefits transfer approach uses as its foundation the relationship between 

emission reductions and ambient PM2.5 concentrations modeled for the Clean Air Nonroad Diesel 

(CAND) proposal.E

 For a given future year, we first calculate the ratio between CAND PM2.5 

precursor emission reductions (direct PM and NOx) and PM2.5 precursor emission reductions 

associated with the proposed standards (proposed emission reductions/CAND emission 

reductions, displayed in Table 8.2-1). We multiply these ratios by the percent that each PM2.5 

precursor contributes towards population-weighted reductions in total PM2.5 due to the CAND 

standards (displayed in Table 8.2-2). This calculation results in a "benefits apportionment 

factor" for the relationship between direct PM emissions and ambient PM2.5 and NOx emissions 

and ambient PM2.5 (displayed in Table 8.2-3). The benefits apportionment factors are then 

applied to the BenMAP-based incidence and monetized benefits from the CAND proposal. In 

this way, we apportion the results of the proposed CAND analysis to its underlying PM2.5 

precursor emission reductions and scale the apportioned benefits to reflect differences in 

D Interested parties may want to consult the webpage: http://www.epa.gov/science1 regarding components of the 
 

812 prospective analytical blueprint. 
 E

 See 68 FR 28327, May 23, 2003. 
 

8-8 
 
___________________________________________________________________________Cost-Benefit Analysis 

emission reductions between the two rules.F This benefits transfer method is consistent with the 

approach used in other recent mobile and stationary source rules.G We refer the reader to the 

final CAND RIA for more details on this benefits transfer approach.9 

Table 8.2-1. Comparison of 48-state Emission Reductions in 2020 and 2030 Between the 

CAND Rule and Proposed Standards 

Emissions Species Reduction from Baseline (tons) Ratio of Reductions 

(Proposal/ CAND) 

CAND Modeling 

Inputsa 

Small SI/Marine SI 

Emissions 

Changes

b 

2020

 NOx 663,618 72,257 0.11 

 Direct PM2.5 98,121 4,896 0.05 

2030

 NOx 1,009,774 98,146 0.10 

 Direct PM2.5 138,208 6,299 0.05 

a

 Includes all affected nonroad sources: land-based, recreational marine, commercial 

marine, and locomotives. See the CAND RIA for more information regarding the 

CAND emission inventories. b

 Includes changes to the small spark ignition engine inventory (lawn and garden 

equipment) and recreational marine spark ignition engine inventory. 

F

 Note that while the proposed regulations also control VOCs, which contribute to PM formation, the benefits 

transfer scaling approach only scales benefits based on NOx, SO2, and direct PM emission reductions. PM benefits 

will likely be underestimated as a result, though we are unable to estimate the magnitude of the underestimation. G See: Clean Air Nonroad Diesel final rule (69 FR 38958, June 29, 2004); Nonroad Large Spark-Ignition Engines 

and Recreational Engines standards (67 FR 68241, November 8, 2002); Final Industrial Boilers and Process Heaters 

NESHAP (69 FR 55217, September 13, 2004); Final Reciprocating Internal Combustion Engines NESHAP (69 FR 

33473, June 15, 2004); Final Clean Air Visibility Rule (EPA-452/R-05-004, June 15, 2005); Ozone Implementation 

Rule (70 FR 71611, November 29, 2005). 

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Draft Regulatory Impact Analysis__________________________________________________________________ 

Table 8.2-2. Apportionment of Modeled CAND Preliminary Control Option Populationweighted Change in Ambient PM2.5 to Nitrate, Sulfate, and Primary Particles 

2020 2030 

Population-weighted 

Change (μg/m3) 

Percent of Total 

Change 

Population-weighted 

Change (μg/m3) 

Percent of Total 

Change 

Total PM2.5 0.316 -- 0.438 -- 

 Sulfate 

 Nitrate 

 Primary PM 

0.071 22.5% 

0.041 13.1% 

0.203 64.4% 

0.090 20.5% 

0.073 16.8% 

0.274 62.7% 

Source: CAND RIA, Chapter 9. 

Table 8.2-3. Calculation of PM2.5 Benefits Apportionment Factors for the Proposed 

Emission Reductions 

2020 2030 

Ratio of 

Emission 

Reductionsa 

(1) 

% of Total 

Ambient 

Change

b 

(2) 

Benefits 

Apportionment 

Factor 

(1*2) 

Ratio of 

Emission 

Reductionsa 

(3) 

% of Total 

Ambient 

Change

b 

(4) 

Benefits 

Apportionment 

Factor 

(3*4) 

NOx 

Emissions 0.11 0.131 0.014 0.10 0.168 0.016 

Direct PM 

Emissions 0.05 0.644 0.032 0.05 0.627 0.029 

a

 Calculated by dividing the small SI and marine SI engine emission reductions by CAND emission reductions. See 
 

Table 8.2-1. 
 b

 See Table 8.2-2. 
 

8.3 PM-Related Health Benefits Estimation - Methods and Inputs 

The analytical approach used in this benefits analysis is largely the same approach used 

in the Final CAND benefits analysis and the reader is referred to that RIA for details on the 

benefits methods and inputs. This analysis, however, also reflects some advances in data and 

methods in epidemiology, economics, and health impact estimation consistent with the approach 

used in the recent RIA for the PM NAAQS. Updates to the assumptions and methods used in 

estimating PM2.5-related benefits since the analysis for the CAND rule include the following: 

C Consistent with the approach used in the recent RIA for the PM NAAQS, we have 

updated our projections of mortality incidence rates to be consistent with the U.S. 

Census population projections that form the basis of our future population estimates. 

Compared to the methodology used in the CAIR analysis, this change will result in a 

reduction in mortality impacts in future years, as overall mortality rates are projected 

to decline for most age groups. A memorandum drafted by Abt Associates (Abt 

Associates, 2005) contains complete details regarding the derivation of mortality rate 

8-10 
 
___________________________________________________________________________Cost-Benefit Analysis 

adjustment factors, and estimation of future-year mortality rates used in the 

analysis.10 The scaled mortality benefits for the proposed standards have been 

updated accordingly. 

C Consistent with the approach used in the recent RIA for the PM NAAQS, we use a 

revised mortality lag assumption. In the Final CAND, we used a five-year segmented 

lag. Since that analysis, upon which the PM benefits transfer scaling approach is 

based, the SAB Health Effects Subcommittee (HES) recommended 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. 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. For 

future analyses, the specific distribution of deaths over time will need to be 

determined through research on causes of death and progression of diseases 

associated with air pollution. It is important to keep in mind that changes in the lag 

assumptions do not change the total number of estimated deaths but rather the timing 

of those deaths. This approach is different than the 5-year segmented lag used in the 

CAND analysis, and the scaled benefits analysis of the proposed standards has been 

updated accordingly. 

For the purposes of this RIA, the health impacts analysis is limited to those health effects 

that are directly linked to ambient levels of air pollution and specifically to those linked to PM. 

The specific studies from which effect estimates for the primary analysis are drawn are included 

in Table 8.3-1. The specific unit values used for economic valuation of health endpoints are 

included in Table 8.3-2. 

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Draft Regulatory Impact Analysis__________________________________________________________________

Table 8.3-1. Endpoints and Studies Used to Calculate Total Monetized Health Benefitsa

Endpoint Pollutant Study

Study 

Population

Premature Mortality 

Premature mortality 

— ACS cohort study, 

all-cause 

PM2.5 Pope et al. (2002)11 >29 years 

Premature mortality 

— all-cause 

PM2.5 Woodruff et al. (1997)

12 Infant (<1 year) 

Chronic Illness

Chronic bronchitis PM2.5 Abbey et al. (1995)13 >26 years 

Nonfatal heart attacks PM2.5 Peters et al. (2001)14 Adults 

Hospital Admissions

Respiratory 

PM2.5

Pooled estimate: 

Moolgavkar (2003)

15—ICD 490-496 (COPD) 

Ito (2003)16—ICD 490-496 (COPD) 

>64 years 

PM2.5 Moolgavkar (2000)

17—ICD 490-496 (COPD) 20–64 years 

PM2.5 Ito (2003)—ICD 480-486 (pneumonia) >64 years 

PM2.5 Sheppard (2003)18—ICD 493 (asthma) <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 

PM2.5 Norris et al. (1999)19 0–18 years 

Other Health Endpoints 

Acute bronchitis PM2.5 Dockery et al. (1996)20 8–12 years 

Upper respiratory

symptoms

PM2.5 Pope et al. (1991)21 Asthmatics, 9–

11 years 

Lower respiratory

symptoms

PM2.5 Schwartz and Neas (2000)22 7–14 years 

Asthma

exacerbations 

PM2.5 Pooled estimate: 

Ostro et al. (2001)23 (cough, wheeze and shortness of 

breath) 

Vedal et al. (1998)24 (cough)

6–18 years

b

Work loss days PM2.5 Ostro (1987)

25 18–65 years 

MRADs PM2.5 Ostro and Rothschild (1989)26 18–65 years 

a The endpoints and studies used for the primary estimate of benefits associated with the proposed rule have been 

subject to external technical guidance and review, including the Health Effects Subgroup (HES) of the EPA’s 

Science Advisory Board (SAB) and the Office of Management and Budget (OMB). b 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 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.

8-12 
Table 8.3-2. Unit Values Used for Economic Valuation of Health Endpoints (2000$)a 

Health Endpoint 

Central Estimate of Value Per Statistical Incidence 

Derivation of Estimat

1990 Income 

Level 

2020 Income 

Levelb 

2030 Income 

Levelb 

Premature Mortality (Value of a Statistical Life) 

$5,500,000 $6,600,000 $6,800,000 Point estimate is the mean of a normal distributio

confidence interval between $1 and $10 million. based on two meta-analyses of the wage-risk VSL represents the lower end of the interquartile range Taylor (2002)27 meta-analysis and $10 million re

the interquartile range from the Viscusi and Aldy 

The VSL represents the value of a small change iover the affected population. 

Chronic Bronchitis (CB) $340,000 $420,000 $430,000 Point estimate is the mean of a generated distribu

of pollution-related CB. WTP to avoid a case of derived by adjusting WTP (as described in Viscu

a severe case of CB for the difference in severity elasticity of WTP with respect to severity of CB. 

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 

$66,902 $74,676 $78,834 

$140,649 

$66,902 $65,293 $73,149 $76,871 

$132,214 

$65,293 

$66,902 $74,676 $78,834 

$140,649 

$66,902 $65,293 $73,149 $76,871 

$132,214 

$65,293 

$66,902 $74,676 $78,834 

$140,649 

$66,902 $65,293 $73,149 $76,871 

$132,214 

$65,293 

Age-specific cost-of-illness values reflect lost earcosts over a 5-year period following a nonfatal Mare based on Cropper and Krupnick (1990).30 Dion simple average of estimates from Russell et al

(1990).32 

Lost earnings: 

Cropper and Krupnick (1990). Present discounteearnings: 

age of onset: at 3% at 7% 25-44 $8,774 $7,855 45-54 $12,932 $11,578 55-65 $74,746 $66,920 Direct medical expenses: An average of: 

1. Wittels et al. (1990) ($102,658—no discountin2. Russell et al. (1998), 5-year period ($22,331 aat 7% discount rate) 
Table 8.3-2. Unit Values Used for Economic Valuation of Health Endpoints (2000$)a (conti

Health Endpoint 

Central Estimate of Value Per Statistical 

Incidence 

Derivation of Estimat

1990 Income 

Level 

2020 Income 

Levelb 

2030 Income 

Levelb 

Hospital Admissions Chronic Obstructive Pulmonary Disease (COPD) (ICD codes 490-492, 494-496) 

$12,378 $12,378 $12,378 The COI estimates (lost earnings plus direct medi

ICD-9 code-level information (e.g., average hosplength of hospital stay, and weighted share of totareported in Agency for Healthcare Research and Q

(www.ahrq.gov). 

Pneumonia (ICD codes 480-487) 

$14,693 $14,693 $14,693 The COI estimates (lost earnings plus direct medi

ICD-9 code-level information (e.g., average hosplength of hospital stay, and weighted share of totaillnesses) reported in Agency for Healthcare Rese(www.ahrq.gov). 

Asthma Admissions $6,634 $6,634 $6,634 The COI estimates (lost earnings plus direct medi

ICD-9 code-level information (e.g., average hosplength of hospital stay, and weighted share of totareported in Agency for Healthcare Research and Q(www.ahrq.gov). 

All Cardiovascular (ICD codes 390-429) 

$18,387 $18,387 $18,387 The COI estimates (lost earnings plus direct medi

ICD-9 code-level information (e.g., average hosplength of hospital stay, and weighted share of totaillnesses) reported in Agency for Healthcare Rese(www.ahrq.gov). 

Emergency Room Visits for Asthma $286 $286 $286 Simple average of two unit COI values: 

(1) $311.55, from Smith et al. (1997)34 and 

(2) $260.67, from Stanford et al. (1999).35 
Table 8.3-2. Unit Values Used for Economic Valuation of Health Endpoints (2000$)a (conti

Health Endpoint 

Central Estimate of Value Per Statistical 

Incidence 

Derivation of Estimat

1990 Income 

Level 

2020 Income 

Levelb 

2030 Income 

Levelb 

Respiratory Ailments Not Requiring Hospitalization Upper Respiratory Symptoms (URS) $25 $27 $27 Combinations of the three symptoms for which W

that closely match those listed by Pope et al. resu“symptom clusters,” each describing a “type” of Uderived for each type of URS, using mid-range es1994)36 to avoid each symptom in the cluster and WTPs. The dollar value for URS is the average oseven different types of URS. 

Lower Respiratory Symptoms (LRS) $16 $17 $17 Combinations of the four symptoms for which W

that closely match those listed by Schwartz et al. “symptom clusters,” each describing a “type” of Lderived for each type of LRS, using mid-range esto avoid each symptom in the cluster and assumindollar value for LRS is the average of the dollar vtypes of LRS. 

Asthma Exacerbations $42 $45 $45 Asthma exacerbations are valued at $42 per incid

average WTP estimates for the four severity definday,” described in Rowe and Chestnut (1986).37 

asthmatics to estimate WTP for avoidance of a “bby the subjects. For purposes of valuation, an astequivalent to a day in which asthma is moderate oRowe and Chestnut (1986) study. 

Acute Bronchitis $360 $380 $390 Assumes a 6-day episode, with daily value equal 

high values for related respiratory symptoms recoal. (1994).38 

(conti
Table 8.3-2. Unit Values Used for Economic Valuation of Health Endpoints (2000$)a (conti

Health Endpoint

Central Estimate of Value Per Statistical Incidence 

Derivation of Estimat

1990 Income 

Level

2020 Income 

Levelb

2030 Income 

Levelb

Restricted Activity and Work/School Loss DaysWork Loss Days (WLDs) Variable 

(national 

median = )

County-specific median annual wages divided bvacation) and then by 5—to get median daily waCensus, compiled by Geolytics, Inc.

Minor Restricted Activity Days(MRADs)

$51 $54 $55 Median WTP estimate to avoid one MRAD from 

a Although the unit values presented in this table are in year 2000 dollars, all monetized annual benefit estimates associated with the proposed standardreflect values in year 2005 dollars. We use the Consumer Price Indexes to adjust both WTP- and COI-based benefits estimates to 2005 dollars from 2

based estimates, we use an inflation factor of 1.13 based on the CPI-U for “all items.” For COI-based estimates, we use an inflation factor of 1.24 bascare.

b Our analysis accounts for expected growth in real income over time. Economic theory argues that WTP for most goods (such as environmental proteincomes increase. Benefits are therefore adjusted by multiplying the unadjusted benefits by the appropriate adjustment factor to account for income grcomplete discussion of how these adjustment factors were derived, we refer the reader to Chapter 9 of the CAND regulatory impact analysis (EPA, 20adjustments do not exist for cost-of-illness-based unit values. For these, we apply the same unit value regardless of the future year of analysis.
___________________________________________________________________________Cost-Benefit Analysis

8-17 

EPA typically estimates the welfare impacts of effects such as changes in recreational 

visibility (related to reductions in ambient PM) and agricultural productivity (related to 

reductions in ambient ozone) in its RIAs of air quality policy. For the analysis of the proposed 

standards, however, we are unable to quantitatively characterize these impacts because of limited 

data availability; we are not quantifying ozone benefits related to the proposed standards and the 

PM scaling approach does not provide the spatial detail necessary to attribute specific air quality 

improvements to specific areas of visual interest (Class I areas). Instead, we discuss these 

welfare effects qualitatively in Section 8.5 of this chapter. We also qualitatively describe the 

impacts of other environmental and ecological effects for which we do not have an economic 

value. 

8.4 Benefits Analysis Results for the Proposed Standards 

Applying the impact and valuation functions described previously in this chapter to the

estimated changes in PM2.5 associated with the proposed standards results in estimates of the 

changes in physical damages (e.g., premature mortalities, cases, admissions) and the associated 

monetary values for those changes. Estimates of physical health impacts are presented in Table 

8.4-1. Monetized values for those health endpoints are presented in Table 8.4-2, along with total 

aggregate monetized benefits. All of the monetary benefits are in constant-year 2005 dollars. 
Draft Regulatory Impact Analysis__________________________________________________________________

8-18 

Table 8.4-1. Estimated Reduction in Incidence of Adverse Health Effects Related to the 

Proposed Standardsa

2020 2030

Health Effect Incidence Reduction

PM-Related Endpoints

Premature Mortalityb,c

Adult, age 30+ and Infant, age <1 year 290 450 

Chronic bronchitis (adult, age 26 and over) 200 290

Nonfatal myocardial infarction (adults, age 18 and older) 490 800 

Hospital admissions—respiratory (all ages)d 160 270 

Hospital admissions—cardiovascular (adults, age >18)e 130 200 

Emergency room visits for asthma (age 18 years and younger) 210 310 

Acute bronchitis (children, age 8–12) 470 700

Lower respiratory symptoms (children, age 7–14) 5,600 8,300 

Upper respiratory symptoms (asthmatic children, age 9–18) 4,300 6,300 

Asthma exacerbation (asthmatic children, age 6–18) 7,000 10,000 

Work loss days (adults, age 18–65) 38,000 52,000

Minor restricted-activity days (adults, age 18–65) 220,000 310,000 a Incidences are rounded to two significant digits. PM estimates are nationwide. b PM premature mortality impacts for adults are based on application of the effect estimate derived from the ACS 

cohort study (Pope et al., 2002).

41 Infant premature mortality based upon studies by Woodruff, et al 1997.42

c PM-related mortality benefits estimated using an assumed PM threshold at background levels (3 μg/m3

). There

is uncertainty about which threshold to use and this may impact the magnitude of the total benefits estimate. For 

a more detailed discussion of this issue, please refer to Section 8.6.2.2 of the RIA. d Respiratory hospital admissions for PM include admissions for COPD, pneumonia, and asthma. e Cardiovascular hospital admissions for PM include total cardiovascular and subcategories for ischemic heart 

disease, dysrhythmias, and heart failure. 
___________________________________________________________________________Cost-Benefit Analysis

8-19 

Table 8.4-2. Estimated Monetary Value in Reductions in Incidence of Health and Welfare 

Effects (in millions of 2005$)a,b

2020 2030

PM-Related Health Effect Estimated Value of Reductions

Premature mortalityc,d,e

Adult, age 30+ and Infant, < 1 year

3% discount rate 

7% discount rate 

$2,000

$1,800

$3,100

$2,800

Chronic bronchitis (adults, 26 and over) $94 $140 

Non-fatal acute myocardial infarctions 

3% discount rate 

7% discount rate 

$50 

$48 

$77 

$75 

Hospital admissions for respiratory causes $2.9 $5.0 

Hospital admissions for cardiovascular causes $3.1 $4.7 

Emergency room visits for asthma $0.07 $0.11 

Acute bronchitis (children, age 8–12) $0.20 $0.30 

Lower respiratory symptoms (children, 7–14) $0.11 $0.16 

Upper respiratory symptoms (asthma, 9–11) $0.13 $0.19 

Asthma exacerbations $0.36 $0.54 

Work loss days $5.8 $7.0 

Minor restricted-activity days (MRADs) $14 $19 

Monetized Total f

 Base Estimate: 

3% discount rate 

7% discount rate 

$2,100+ B 

$1,900+ B 

$3,400+ B 

$3,100+ B a Monetary benefits are rounded to two significant digits for ease of presentation and computation. PM 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 PM-related mortality benefits estimated using an assumed PM threshold at background levels (3 μg/m3

). There

is uncertainty about which threshold to use and this may impact the magnitude of the total benefits estimate. For 

a more detailed discussion of this issue, please refer to Section 8.6.2.2 of the RIA. d Valuation assumes discounting over the SAB recommended 20-year segmented lag structure described earlier. 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).43,44

e Adult premature mortality estimates based upon the ACS cohort study (Pope et al., 2002).45 Infant premature

mortality based upon Woodruff et al 1997.46

f B represents the monetary value of health and welfare benefits and disbenefits not monetized. A detailed listing is 

provided in Table 8.1-2.

In addition to omitted benefits categories such as air toxics, ozone, and various welfare 

effects, not all known PM-related health and welfare effects could be quantified or monetized. 

Furthermore, we did not quantify reductions in secondary PM2.5 and the associated health and 

welfare effects. The monetized value of all of these unquantified effects is represented by adding 

an unknown “B” to the aggregate total. The estimate of total monetized health benefits of the 

proposed control package is thus equal to the subset of monetized PM-related health benefits 

plus B, the sum of the nonmonetized health and welfare benefits. 
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8-20 

Total monetized benefits are dominated by benefits of mortality risk reductions. The 

primary estimate projects that the proposed standards will result in 290 avoided premature deaths 

annually in 2020 and 450 avoided premature deaths annually in 2030. The increase in annual 

benefits from 2020 to 2030 reflects additional emission reductions from the proposed 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 proposed standards is $2.1 billion 

using a three percent discount rate and $1.9 billion using a seven percent discount rate. In 2030, 

the monetized benefits are estimated at $3.4 billion using a three percent discount rate and $3.1 

billion using a seven percent discount rate. The monetized benefit associated with reductions in 

the risk of premature mortality, which accounts for $2.0 billion in 2020 and $3.1 billion in 2030 

(assuming a three percent discount rate), is over 90 percent of total monetized health benefits. 

The next largest benefit is for reductions in chronic illness (CB 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 work loss days than premature mortalities, 

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).H As such, the full 

value of these effects may be higher than that reported in Table 8.4-2. 

8.5 Unquantified Health and Welfare Effects 

In considering the monetized benefits estimates, the reader should remain aware of the 

many limitations of conducting the analyses mentioned throughout this RIA. One significant 

limitation of both the health and welfare benefits analyses is the inability to quantify many of the 

effects listed in Table 8.1-2. For many health and welfare effects, such as changes in health 

effects due to reductions in air toxics exposure, changes in ecosystem functions and PM-related 

materials damage, reliable impact functions and/or valuation functions are not currently 

available. In general, if it were possible to monetize these benefit categories, the benefits 

estimates presented in this analysis would increase, although the magnitude of such an increase 

is highly uncertain. 

Other welfare effects that EPA has monetized in past RIAs, such as recreational 

visibility, are omitted from the current analysis. Due to time and resource constraints, we did not 

H See Table 12.3-2 for a description of how each particular endpoint is valued. 
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run the full-scale PM air quality modeling needed to estimate this benefit category. Instead, we 

relied on the PM scaling benefits transfer approach that provides analytical efficiency but 

sacrifices the full range of outputs typically generated when models such as the Community 

Multiscale Air Quality (CMAQ) model or the Regional Modeling System for Aerosols and 

Deposition (REMSAD) are run. 

Unquantified benefits are qualitatively discussed in the following health and welfare 

effects sections. In addition to unquantified benefits, there may also be environmental costs 

(disbenefits) that we are unable to quantify, which we qualitatively discuss as well. The net 

effect of excluding benefit and disbenefit categories from the estimate of total benefits depends 

on the relative magnitude of the effects. Although we are not currently able to estimate the 

magnitude of these unquantified and unmonetized benefits, specific categories merit further 

discussion. EPA believes, however, the unquantified benefits associated with health and nonhealth benefit categories are likely significant and that their omission lends a downward bias to 

the monetized benefits presented in this analysis. 

8.5.1 Human Health Impact Assessment 

In addition to the PM2.5 health effects discussed above, there is emerging evidence that 

human exposure to PM may be associated a number of health effects not quantified in this 

analysis (see Table 8.1-2). An improvement in ambient PM2.5 concentrations may reduce the 

number of incidences within each of these unquantified effect categories that the U.S. population 

would experience. Although these health effects are believed to be PM-induced, effect estimates 

are not available for quantifying the benefits associated with reducing these effects. 

Furthermore, the health effects associated with reductions in air toxics are not quantified in this 

analysis. 

The proposed standards will also reduce the national emissions inventory of precursors to 

ozone, such as VOCs. Exposure to ozone has been linked to a variety of respiratory effects 

including hospital admissions, emergency room visits, minor restricted activity days, worker 

productivity and illnesses resulting in school absences. Emerging evidence has also shown that 

human exposure to ozone may be associated with a number of other health effects not quantified 

in this analysis (see Table 8.1-2). Ozone can also adversely affect the agricultural and forestry 

sectors by decreasing yields of crops and forests. Although ozone benefits are typically 

quantified in regulatory impact analyses, we have chosen not to evaluate them for this analysis. 

As discussed in Chapter 2, the ozone modeling conducted for the proposed standards results in a 

net reduction in ambient concentrations of ozone in 2020 and 2030. By omitting ozone benefits 

in this proposal, we acknowledge that this analysis underestimates the benefits associated with 

the proposed standards. 

8.5.2 Welfare Impact Assessment 

For many welfare effects, such as changes in ecosystem functions and PM-related 

materials damage, reliable impact functions and/or valuation functions are not currently 
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available. In general, if it were possible to monetize these benefit categories, the benefits 

estimates presented in this analysis would increase, although the magnitude of such an increase 

is highly uncertain. 

8.5.2.1 Visibility Benefits 

Changes in the level of ambient PM2.5 caused by the proposed standards will change the 

level of visibility in much of the United States. Visibility directly affects people’s enjoyment of 

a variety of daily activities. Individuals value visibility both in the places they live and work, in 

the places they travel to for recreational purposes, and at sites of unique public value, such as the 

Great Smoky Mountains National Park. Though not quantified in this analysis, the value of 

improvements in visibility monetized for regulatory analyses such as the final CAIR are 

significant. We refer the reader to that analysis for a complete description of the methods used to 

value visibility.47

8.5.2.2 gricultural and Forestry Benefits 

The Ozone Criteria Document notes that “ozone affects vegetation throughout the United 

States, impairing crops, native vegetation, and ecosystems more than any other air pollutant” 

(EPA, 1996, page 5-11).48 Though we do not quantify the potential improvements in ambient 

ozone concentrations associated with the proposed standards, it is possible that yields will 

improve in areas of agricultural or forestry production impacted by the standards. 

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 agricultural products’ supply and demand. 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 forestry benefits estimates for the proposed 

standards. 

8.5.2.2.1 Agricultural Benefits 

Laboratory and field experiments have 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 United States.”54 In addition, economic studies have shown a relationship between 

observed ozone levels and crop yields.49

8.5.2.2.2 Forestry Benefits 

Ozone also has been shown conclusively to cause discernible injury to forest trees (EPA, 
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1996; Fox and Mickler, 1996).54,50 In our previous analysis of the Heavy-Duty Engine/Diesel 

Fuel rule, we were able to quantify the effects of changes in ozone concentrations on tree growth 

for a limited set of species. 

8.5.2.3 Benefits from Reductions in Materials Damage 

The proposed standards that we modeled are expected to produce economic benefits in 

the form of reduced materials damage. There are two important categories of these benefits. 

Household soiling refers to the accumulation of dirt, dust, and ash on exposed surfaces. PM also 

has corrosive effects on commercial/industrial buildings and structures of cultural and historical 

significance. The effects on historic buildings and outdoor works of art are of particular concern 

because of the uniqueness and irreplaceability of many of these objects. 

Previous EPA benefits analyses have been able to provide quantitative estimates of 

household soiling damage. Consistent with SAB advice, we determined that the existing data 

(based on consumer expenditures from the early 1970s) are too out of date to provide a reliable 

estimate of current household soiling damages (EPA-SAB-COUNCIL-ADV-98-003, 1998).51

EPA is unable to estimate any benefits to commercial and industrial entities from reduced 

materials damage. Nor is EPA able to estimate the benefits of reductions in PM-related damage 

to historic buildings and outdoor works of art. Existing studies of damage to this latter category 

in Sweden (Grosclaude and Soguel, 1994)52 indicate that these benefits could be an order of 

magnitude larger than household soiling benefits. 

8.5.3 UVb Exposure 

In contrast to the unquantified benefits of the proposed standards discussed above, it is 

also possible that this rule will result in disbenefits in some areas of the United States. The 

effects of ozone and PM on radiative transfer in the atmosphere can lead to effects of uncertain 

magnitude and direction on the penetration of ultraviolet light and climate. Ground level ozone 

makes up a small percentage of total atmospheric ozone (including the stratospheric layer) that 

attenuates penetration of ultraviolet - b (UVb) radiation to the ground. EPA’s past evaluation of 

the information indicates that potential disbenefits would be small, variable, and with too many 

uncertainties to attempt quantification of relatively small changes in average ozone levels over 

the course of a year.53 EPA’s most recent provisional assessment of the currently available 

information indicates that potential but unquantifiable benefits may also arise from ozone-related 

attenuation of UVb radiation.54 EPA believes that we are unable to quantify any net climaterelated disbenefit or benefit associated with the combined ozone and PM reductions in this rule. 

8.6 Methods for Describing Uncertainty 

In any complex analysis using estimated parameters and inputs from numerous models, there are 

likely to be many sources of uncertainty. This analysis is no exception. As outlined both in this 

and preceding chapters, many inputs were used to derive the benefits estimate, including 
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emission inventories, air quality models (with their associated parameters and inputs), 

epidemiological health effect estimates, estimates of values (both from WTP and COI studies), 

population estimates, income estimates, and estimates of the future state of the world (i.e., 

regulations, technology, and human behavior). Each of these inputs may be uncertain and, 

depending on its role in the benefits analysis, may have a disproportionately large impact on 

estimates of total benefits. For example, emissions estimates are used in the first stage of the 

analysis. As such, any uncertainty in emissions estimates will be propagated through the entire 

analysis. Some of the key uncertainties in the quantified benefits analysis are presented in Table 

8.6-1.

Table 8.6-1. Primary Sources of Uncertainty in the Quantified Benefits Analysis

1. Uncertainties Associated with Impact Functions

● The value of the PM effect estimate in each impact function. 

● Application of a single impact function to pollutant changes and populations in all locations. 

● Similarity of future-year impact functions to current impact functions. 

● Correct functional form of each impact function. 

● Extrapolation of effect estimates beyond the range of PM concentrations observed in the source 

epidemiological study. 

● Application of some impact functions only to those subpopulations matching the original study

population.

2. Uncertainties Associated with PM Concentrations

● Responsiveness of the models to changes in precursor emissions resulting from the control policy. 

● Projections of future levels of precursor emissions, especially organic carbonaceous particle emissions. 

● Model chemistry for the formation of ambient nitrate concentrations. 

● Lack of speciation monitors in some areas requires extrapolation of observed speciation data. 

● CMAQ model performance in the Western U.S., especially California indicates significant 

underprediction of PM2.5.

3. Uncertainties Associated with PM Mortality Risk

● Differential toxicity of specific component species within the complex mixture of PM has not been

determined. 

● The extent to which adverse health effects are associated with low-level exposures that occur many times 

in the year versus peak exposures. 

● The extent to which effects reported in the long-term exposure studies are associated with historically 

higher levels of PM rather than the levels occurring during the period of study. 

● Reliability of the limited ambient PM2.5 monitoring data in reflecting actual PM2.5 exposures.

5. Uncertainties Associated with Possible Lagged Effects

● The portion of the PM-related long-term exposure mortality effects associated with changes in annual PM 

levels that would occur in a single year is uncertain as well as the portion that might occur in subsequent

years.
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6. Uncertainties Associated with Baseline Incidence Rates

● Some baseline incidence rates are not location specific (e.g., those taken from studies) and therefore may

not accurately represent the actual location-specific rates. 

● Current baseline incidence rates may not approximate well baseline incidence rates in 2020 and 2030. 

● Projected population and demographics may not represent well future-year population and demographics.

7. Uncertainties Associated with Economic Valuation

● Unit dollar values associated with health and welfare endpoints are only estimates of mean WTP and 

therefore have uncertainty surrounding them. 

● Mean WTP (in constant dollars) for each type of risk reduction may differ from current estimates because 

of differences in income or other factors.

8. Uncertainties Associated with Aggregation of Monetized Benefits

● Health and welfare benefits estimates are limited to the available impact functions. Thus, unquantified or

unmonetized benefits are not included.

As part of EPA’s approach to characterizing uncertainties in the benefits assessment, we 

generate a probabilistic estimate of statistical uncertainty based on standard errors reported in the 

underlying studies used in the benefits modeling framework, with particular emphasis on the 

health impact functions. Using a Monte Carlo procedure, the distribution of each health endpoint 

and its unit dollar value is characterized by the reported mean and standard error derived from

the epidemiology and valuation literature. Details on the distributions used to value individual 

health endpoints are provided in Section 8.6.1, as well as in the CAIR RIA (Appendix B; EPA, 

2005).55 It should be noted that the Monte Carlo-generated distributions of benefits reflect only 

some of the uncertainties in the input parameters (described in Table 8.6-1). Uncertainties 

associated with emissions, air quality modeling, populations, and baseline health effect incidence 

rates are not represented in the distributions of benefits of attaining alternative standards. Issues 

such as correlation between input parameters and the identification of reasonable upper and 

lower bounds for input distributions characterizing uncertainty in additional model elements will 

be addressed in future versions of the uncertainty framework. 

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. Therefore, in 

characterizing the uncertainty related to the estimates of total benefits it is particularly important 

to attempt to characterize the uncertainties associated with this endpoint. As such, we 

specifically discuss the uncertainty related to PM-related premature mortality in Section 8.6.2. 

8.6.1 Analysis of Statistical Uncertainty 

For the proposed standards, we did not attempt to assign probabilities to all of the 

uncertain parameters in the model because of a lack of resources and reliable methods. At this 

time, we simply generate estimates of the distributions of dollar benefits for PM health effects 

and for total dollar benefits. For all quantified PM endpoints, we scaled the likelihood 

distributions of the benefit estimates from the CAND uncertainty analysis,I based on the same

I

 U.S. Environmental Protection Agency. May 2004. Final Regulatory Analysis: Control of Emissions from

Nonroad Diesel Engines. Prepared by: Office of Air and Radiation. Available at http://www.epa.gov/nonroaddiesel/2004fr.htm#documents. Accessed December 15, 2005. 
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benefits transfer approach we used to estimate the benefits of the standards presented in Section 

8.2. The CAND likelihood distributions were based solely on the statistical uncertainty 

surrounding the estimated C-R functions and the assumed distributions around the unit values. 

We use the benefits transfer approach to scale those distributions to reflect the predicted PM 

precursor emission reductions of the proposed standards. Though the scaling approach adds 

another element of uncertainty that we cannot characterize in the distributions, we believe the 

scaled uncertainty is a reasonable approximation of the statistical uncertainty based on standard 

errors reported in the underlying epidemiological and valuation studies. 

Our scaled estimates of the likelihood distributions for health-related PM benefits should 

be viewed as incomplete because of the wide range of sources of uncertainty that we have not 

incorporated. The 5th and 95th percentile points of our scaled estimate are based on statistical 

error, and cross-study variability provides some insight into how uncertain our estimate is with 

regard to those sources of uncertainty. However, it does not capture other sources of uncertainty 

regarding the benefits transfer scaling approach or the inputs to the CAND modeling upon which 

the scaling is based, including emissions, air quality, baseline population incidence, and 

projected exposures. It also does not account for aspects of the health science not captured in the 

studies, such as the likelihood that PM is causally related to premature mortality and other 

serious health effects. Thus, a likelihood description based on the standard error would provide a 

misleading picture about the overall uncertainty in the estimates. 

Both the uncertainty about incidence changesJ and uncertainty about unit dollar values 

can be characterized by distributions. Each Alikelihood distribution@ characterizes our beliefs 

about what the true value of an unknown variable (e.g., the true change in incidence of a given 

health effect in relation to PM exposure) is likely to be, based on the available information from

relevant studies.

K Unlike a sampling distribution (which describes the possible values that an 

estimator of an unknown variable might take on), this likelihood distribution describes our 

beliefs about what values the unknown variable itself might be. Such likelihood distributions 

can be constructed for each underlying unknown variable (such as a particular pollutant 

coefficient for a particular location) or for a function of several underlying unknown variables 

(such as the total dollar benefit of a regulation). In either case, a likelihood distribution is a 

characterization of our beliefs about what the unknown variable (or the function of unknown 

variables) is likely to be, based on all the available relevant information. A likelihood 

description based on such distributions is typically expressed as the interval from the 5th

percentile point of the likelihood distribution to the 95th percentile point. If all uncertainty had 

been included, this range would be the Acredible range@ within which we believe the true value is 

likely to lie with 90 percent probability. 

J

 Because this is a national analysis in which, for each endpoint, a single C-R function is applied everywhere, there 

are two sources of uncertainty about incidence: statistical uncertainty (due to sampling error) about the true value of

the pollutant coefficient in the location where the C-R function was estimated and uncertainty about how well any

given pollutant coefficient approximates β*. K Although such a Alikelihood distribution@ is not formally a Bayesian posterior distribution, it is very similar in

concept and function (see, for example, the discussion of the Bayesian approach in Kennedy, 1990. A Guide to

Econometrics. 2nd ed. MIT Press: Cambridge, MA., pp. 168-172). 
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8.6.1.1 Monte Carlo Approach 

The uncertainty about the total dollar benefit associated with any single endpoint 

combines the uncertainties from these two sources (the C-R relationship and the valuation) and is 

estimated with a Monte Carlo method. In each iteration of the Monte Carlo procedure, a value is 

randomly drawn from the incidence distribution, another value is randomly drawn from the unit 

dollar value distribution; the total dollar benefit for that iteration is the product of the two.L

When this is repeated for many (e.g., thousands of) iterations, the distribution of total dollar 

benefits associated with the endpoint is generated. 

Using this Monte Carlo procedure, a distribution of dollar benefits can be generated for 

each endpoint. As the number of Monte Carlo draws gets larger and larger, the Monte Carlogenerated distribution becomes a better and better approximation of a joint likelihood 

distribution (for the considered parameters) making up the total monetary benefits for the 

endpoint. 

After endpoint-specific distributions are generated, the same Monte Carlo procedure can 

then be used to combine the dollar benefits from different (nonoverlapping) endpoints to 

generate a distribution of total dollar benefits. 

The estimate of total benefits may be thought of as the end result of a sequential process 

in which, at each step, the estimate of benefits from an additional source is added. Each time an 

estimate of dollar benefits from a new source (e.g., a new health endpoint) is added to the 

previous estimate of total dollar benefits, the estimated total dollar benefits increases. However, 

our bounding or likelihood description of where the true total value lies also increases as we add 

more sources. 

As an example, consider the benefits from reductions in PM-related hospital admissions 

for cardiovascular disease. Because the actual dollar value is unknown, it may be described 

using a variable, with a distribution describing the possible values it might have. If this variable 

is denoted as X1, then the mean of the distribution, E(X1) and the variance of X1, denoted 

Var(X1), and the 5th and 95th percentile points of the distribution (related to Var(X1)), are ways 

to describe the likelihood for the true but unknown value for the benefits reduction. 

Now suppose the benefits from reductions in PM-related hospital admissions for 

respiratory diseases are added. Like the benefits from reductions in PM-related hospital 

admissions for cardiovascular disease, the likelihood distribution for where we expect the true 

value to be may be considered a variable, with a distribution. Denoting this variable as X2, the 

benefits from reductions in the incidence of both types of hospital admissions is X1 + X2. This 

variable has a distribution with mean E(X1 + X2) = E(X1) + E(X2), and a variance of Var(X1 + 

L

 This method assumes that the incidence change and the unit dollar value for an endpoint are stochastically

independent.
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X2) = Var(X1) + Var(X2) + 2Cov(X1,X2); if X1 and X2 are stochastically independent, then it 

has a variance of Var(X1 + X2) = Var(X1) + Var(X2), and the covariance term is zero. 

The benefits from reductions in all nonoverlapping PM-related health and welfare 

endpoints are (Xm+1, ..., Xn) is X = X1 + ... + Xn. The mean of the distribution of total 

benefits, X, is 

E(X) = E(X1) + E(X2) + ... + E(Xn) 

and the variance of the distribution of total benefitsCassuming that the components are 

stochastically independent of each other (i.e., no covariance between variables), is 

Var(X) = Var(X1) + Var(X2) + ... + Var(Xn) 

If all the means are positive, then each additional source of benefits increases the point estimate 

(mean) of total benefits. However, with the addition of each new source of benefits, the variance 

of the estimate of total benefits also increases. That is, 

E(X1) < E(X1 + X2) < E(X1 + X2 + X3) < ... < E(X1 + ... + Xn) = E(X) 

Var(X1) < Var(X1 + X2) < Var(X1 + X2 + X3) < ... < Var(X1 + ... + Xn) = Var(X) 

That is, the addition of each new source of benefits results in a larger mean estimate of total 

benefits (as more and more sources of benefits are included in the total) about which there is less 

certainty. This phenomenon occurs whenever estimates of benefits are added. 

Calculated with a Monte Carlo procedure, the distribution of X is composed of random 

draws from the components of X. In the first draw, a value is drawn from each of the 

distributions, X1, X2, through Xn; these values are summed; and the procedure is repeated again, 

with the number of repetitions set at a high enough value (e.g., 5,000) to reasonably trace out the 

distribution of X. The 5th percentile point of the distribution of X will be composed of points 

pulled from all points along the distributions of the individual components and not simply from

the 5th percentile. Although the sum of the 5th percentiles of the components would be 

represented in the distribution of X generated by the Monte Carlo, it is likely that this value 

would occur at a significantly lower percentile. For a similar reason, the 95th percentile of X 

will be less than the sum of the 95th percentiles of the components, and instead the 95th 

percentile of X will be composed of component values that are significantly lower than the 95th 

percentiles. 

The physical effects estimated in this analysis are assumed to occur independently. It is 

possible that, for any given pollution level, there is some correlation between the occurrence of 

physical effects, due to say avoidance behavior or common causal pathways and treatments (e.g., 

stroke, some kidney disease, and heart attack are related to treatable blood pressure). Estimating 

accurately any such correlation, however, is beyond the scope of this analysis, and instead it is 

simply assumed that the physical effects occur independently. 
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8.6.1.2 Monte Carlo Results 

Based on the Monte Carlo techniques and benefits transfer methods described above, we 

scaled the CAND likelihood distributions for the dollar value of total PM health-related benefits 

for the proposed standards. For this analysis, the likelihood descriptions for the true value of 

each of the health endpoint incidence estimates, including premature mortality, were based on 

classical statistical uncertainty measures. The measures include the mean and standard deviation 

of the C-R relationships in the epidemiological literature, and assumptions of particular 

likelihood distribution shapes for the valuation of each health endpoint value based on reported 

values in the economic literature. The distributions for the value used to represent incidence of a 

health effect in the total benefits valuation represent both the simple statistical uncertainty 

surrounding individual effect estimates and, for those health endpoints with multiple effects from

different epidemiology studies, interstudy variability. Distributions for unit dollar values are 

summarized in Table 8.3-2. 

Results of the scaled Monte Carlo simulations are presented in Table 8.6-2. The table 

provides the scaled means of the distributions and the estimated 5th and 95th percentiles of the 

distributions. The contribution of mortality to the mean benefits and to both the 5th and 95th 

percentiles of total benefits is substantial, with mortality accounting for over 90 percent of the 

mean estimate, and even the 5th percentile of mortality benefits dominating close to the 95th 

percentile of all other benefit categories. Thus, the choice of value and the shape for likelihood 

distribution for VSL should be examined closely and is key information to provide to decision 

makers for any decision involving this variable. The 95th percentile of total benefits is 

approximately twice the mean, while the 5th percentile is approximately one-fourth of the mean. 

The overall range from 5th to 95th represents about one order of magnitude. 
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Table 8.6-2. Distribution of Value of Annual PM-Related Human Health Benefits in 2030 

for the Proposed Standardsa

Endpoint Monetary Benefitsb, c (Millions 2003$, Adjusted for Income 

Growth)

5th Percentile Mean 95th Percentile

Premature mortalityc

, Long-term exposure 

Adults, 30+ yrs and Infants, <1yr

 3% Discount Rate 

 7% Discount Rate 

$750

$680

$3,100

$2,800

$6,200

$5,600

Chronic bronchitis (adults, 26 and over) $7.0 $140 $480

Nonfatal myocardial infarctions

 3% Discount Rate 

 7% Discount Rate 

$18 

$17 

$77 

$75 

$180

$180

Hospital admissions from respiratory causes $1.6 $5.0 $8.0 

Hospital admissions from cardiovascular causes $2.8 $4.7 $7.0 

Emergency room visits for asthma $0.07 $0.11 $0.16 

Acute bronchitis (children, aged 8B12) $0 $0.30 $0.70 

Lower respiratory symptoms (children, aged 7B14) $0.06 $0.16 $0.29 

Upper respiratory symptoms (asthmatic children, 

aged 9B11) $0.05 $0.19 $0.42 

Asthma exacerbations $0.01 $0.54 $1.5 

Work loss days (adults, aged 18B65) $6 $7 $8 

Minor restricted-activity days (adults, aged 18B65) $11 $19 $27 

Monetized Totald

 3% Discount Rate 

 7% Discount Rate 

$800 + B 

$720 + B 

$3,400 + B 

$3,100 + B 

$7,000 + B 

$6,300 + B 

a Monetary benefits are rounded to two significant digits. 

b Monetary benefits are adjusted to account for growth in real GDP per capita between 1990 and 2030. 

c Results show 3 percent and 7 percent discount rates consistent with EPA and OMB guidelines for preparing

economic analyses (EPA, 2000; OMB, 2003). 

d B represents the monetary value of the nonmonetized health and welfare benefits. A detailed listing of 

unquantified PM-, ozone-, and air toxics-related health effects is provided in Table 8.1-2. 
___________________________________________________________________________Cost-Benefit Analysis 

8.6.2 Additional Approaches to Characterizing Uncertainty Related to PM-Mortality 

As part of an overall program to improve the Agency’s characterization of uncertainties in 

health benefits analyses, we attempt to address uncertainties associated with the PM2.5 mortality 

health impact function relationship and valuation. Use of the ACS cohort (Pope et al., 2002) 

mortality function to support this analysis does not address uncertainty associated with: (a) 

potential of the study to incompletely capture short-term exposure-related mortality effects, (b) 

potential mis-match between study and analysis populations which introduces various forms of 

bias into the results, (c) failure to identify all key confounders and effects modifiers, which could 

result in incorrect effects estimates relating mortality to PM2.5 exposure, and (d) model 

uncertainty. EPA is researching methods to characterize all elements of uncertainty in the doseresponse function for mortality. 

As is discussed in detail in the final PM NAAQS RIA, EPA uses three methods to 

quantify uncertainties in the mortality function, including: the statistical uncertainty derived from 

the standard errors reported in the ACS cohort study, the presentation of additional estimates of 

mortality based upon the peer-reviewed literature, and the use of results of an expert elicitation 

conducted to explore a more thorough characterization of uncertainties in the mortality estimate. 

Because this analysis utilizes the PM scaling benefits transfer approach to estimate mortality 

incidence for the proposed standards, we cannot quantify the PM mortality uncertainty to the 

same extent as was done for the CAIR or PM NAAQS analyses. However, in a similar fashion 

to the analysis conducted for the Clean Air Visibility Rule (CAVR),56 we can scale the results of 

the CAND mortality uncertainty analysis to the PM precursor emission changes modeled for the 

proposed standards. 

8.6.2.1 Uncertainty Associated with the Concentration-Response Function 

In the benefit analysis of the CAND 2030 emission control standards, the statistical 

uncertainty represented by the standard error of the American Cancer Society cohort study (Pope 

et al, 2002) was one and one-half times the mean benefit estimate at the 95th percentile and less 

than one-half of the mean at the 5th percentile. The CAND analysis also derived mortality from 

the reanalysis of the Harvard Six-Cities study (Krewski et al., 2000).57 At the time of the CAND 

analysis, EPA’s Science Advisory Board provided guidance stating, “The Six-Cities estimates 

may be used in a sensitivity analysis to demonstrate that with different but also plausible 

selection criteria for C-R functions, benefits may be considerably larger than suggested by the 

ACS study.” (EPA-SAB-COUNCIL-ADV-04-002).58 In the CAND analysis, the Harvard SixCities mean benefits estimate was over twice the size of the mean estimate of mortality benefits 

derived from the ACS study. 

Recently, a new peer-reviewed extension of the Six-Cities study has been published 

(Laden et al., 2006).59 This follow-up to the Harvard Six-Cities study both confirmed the effect 

size from the first analysis and provided additional evidence that reductions in PM2.5 are likely 

associations with reductions in the risk of premature death. This additional evidence stems from 

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Draft Regulatory Impact Analysis__________________________________________________________________ 

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. In the recently finalized PM NAAQS RIA, results from this study were 

presented as an additional estimate of premature mortality benefits along with the benefits 

derived from the ACS study. The mean benefits estimate derived from the Six-Cities study was 

more than twice the size of the mean estimate of mortality benefits derived from the ACS study. 

Because this study was not available during the CAND analysis, from which the benefits of the 

proposed standards are scaled, we are unable to provide an estimate of mortality benefits based 

on the Six-Cities study for this proposed analysis. However, based on the relationship between 

the Six-Cities study and the ACS cohort study observed in the final PM NAAQS RIA, we can 

surmise that the mean estimate of PM-related mortality associated with the proposed standards 

could be approximately twice as large. For a full discussion of the epidemiological basis of 

EPA’s premature mortality estimates, we refer the reader to Chapter 5.1 of the final PM NAAQS 

RIA. 

EPA recently completed a full-scale expert elicitation that incorporated peer-review 

comments on the pilot application used in CAND, and that provides a more robust 

characterization of the uncertainty in the premature mortality function. This expert elicitation 

was designed to evaluate uncertainty in the underlying causal relationship, the form of the 

mortality impact function (e.g., threshold versus linear models) and the fit of a specific model to 

the data (e.g., confidence bounds for specific percentiles of the mortality effect estimates). 

Additional issues, such as the ability of long-term cohort studies to capture premature mortality 

resulting from short-term peak PM exposures, were also addressed in the expert elicitation. The 

recently published RIA supporting the Particulate Matter National Ambient Air Quality 

Standards (PM NAAQS) used the results of this expert elicitation to quantitatively characterize 

uncertainty. 

Due to the analytical constraints associated with the PM benefits scaling approach, we are 

unable to assess the premature mortality health impacts derived from the formally elicited expert 

judgments. Compared to the final PM NAAQS estimate of mean premature mortality derived 

from the ACS cohort study, however, expert-based mortality incidence ranged from 

approximately 50 percent of the mean ACS estimate to approximately five times the size of the 

mean ACS estimate. In total, PM-related premature mortality derived from eleven of the experts 

was greater than the ACS estimate, while one expert-based estimate fell below the ACS result. 

8.6.2.2 PM2.5-Mortality Cutpoint/Threshold Analysis 

Another source of uncertainty that has received recent attention from several scientific 

review panels is the shape of the concentration-response function for PM-related mortality, and 

specifically whether there exists a threshold below which there would be no benefit to further 

reductions in PM2.5. The consistent advice from EPA’s SABM has been to model premature 

M The advice from the 2004 SAB-HES (EPA-SAB-COUNCIL-ADV-04-002)69 is characterized by the following: 

“For the studies of long-term exposure, the HES notes that Krewski et al. (2000) have conducted the most careful 

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___________________________________________________________________________Cost-Benefit Analysis 

mortality associated with PM exposure as a nonthreshold effect, that is, with harmful effects to 

exposed populations regardless of the absolute level of ambient PM concentrations. However, 

EPA’s most recent PM2.5 Criteria Document concludes that “the available evidence does not 

either support or refute the existence of thresholds for the effects of PM on mortality across the 

range of concentrations in the studies.”60 Some researchers have hypothesized the presence of a 

threshold relationship. That is, the hypothesized relationship includes the possibility that there 

exists a PM concentration level below which further reductions no longer yield premature 

mortality reduction benefits. 

To consider the impact of a threshold in the response function for the chronic mortality 

endpoint, the final PM NAAQS RIA61 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, the PM NAAQS analysis adjusted the mortality function slopes 

accordingly.N Five cutpoints (including the base case assumption) were included in the 

sensitivity analysis: (a) 14 μg/m3 (assumes no impacts below a level being considered at the time 

for the annual PM2.5 NAAQS), (b) 12 μg/m3 (c) 10 μg/m3 (reflects comments from CASAC, 

2005), 62 (d) 7.5 μg/m3 (reflects recommendations from SAB-HES to consider estimating 

mortality benefits down to the lowest exposure levels considered in the ACS cohort study (Pope 

et al., 2002) used as the basis for modeling chronic mortality) 63 and (e) background or 3 μg/m3 

(reflects NRC recommendation to consider effects all the way to background).64 The results of 

the sensitivity analysis displayed the change in avoided mortality cases and associated monetary 

benefits associated with the alternative cutpoints (see the final PM NAAQS RIA, Chapter 5.1 

and Tables 5-28 to 5-31). 

A sensitivity analysis such as this can be difficult to interpret, because when a threshold 

above the lowest observed level of PM2.5 in the underlying ACS cohort study (Pope et al., 2002) 

is assumed, the slope of the concentration-response function above that level must be adjusted 

upwards to account for the assumed threshold.O Depending on the amount of slope adjustment 

and the proportion of the population exposed above the assumed threshold, the estimated 

mortality impact can either be lower (if most of the exposures occur below the threshold) or 

higher (if most of the exposures occur above the threshold). To demonstrate this, we present an 

example from the proposed PM NAAQS RIA. In its examination of the benefits of attaining 

alternative PM NAAQS in Chicago,P

 the analysis found that, because annual mean levels are 

generally higher in Chicago, there was a two-part pattern to the relationship between assumed 

work on this issue. They report that the associations between PM2.5 and both all-cause and cardiopulmonary 

mortality were near linear within the relevant ranges, with no apparent threshold. Graphical analyses of these 

studies (Dockery et al., 1993, Figure 3, and Krewski et al., 2000, page 162) also suggest a continuum of effects 

down to lower levels. Therefore, it is reasonable for EPA to assume a no threshold model down to, at least, the low 

end of the concentrations reported in the studies.” N Note that the PM NAAQS 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. O See NAS (2002)71 and CASAC (2005)68 for discussions of this issue. P

 See the proposed PM NAAQS RIA (2005),67 Appendix A, pp. A63-A64. 

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Draft Regulatory Impact Analysis__________________________________________________________________ 

threshold and mortality impacts. As the threshold increased from background to 7.5 μg/m3, the 

mortality impact fell (because there is no slope adjustment). However, at an assumed threshold 

of 10 μg/m3, estimated mortality impacts actually increased, because the populations exposed 

above 10 μg/m3 were assumed to have a larger response to particulate matter reductions (due to 

the increased slope above the assumed threshold). And finally, mortality impacts again fell to 

zero if a 15 μg/m3 threshold was assumed, because these impacts were measured incremental to 

attainment of the current standard. 

We are unable to do this type of sensitivity analysis for the analysis of the proposed 

standards because of the analytical limitations of the PM benefits scaling procedure. When EPA 

conducted the CAND analysis (from which the primary estimates of benefits for the proposed 

standards are based), there were no PM mortality concentration-response functions with the 

slope adjusted upwards to account for an assumed threshold. Instead, our primary PM benefits 

estimate for the proposed standards reflects a background threshold assumption of 3 μg/m3. We 

present in Table 8.6-3 the results of our scaled PM-related mortality benefits in the context of its 

relationship to other cutpoints. 

Table 8.6-3. PM-Related Mortality Benefits of the Proposed Standards: Cutpoint 
 

Sensitivity Analysisa 
 

Certainty that Benefits are 

At Least Specified Value 

Level of Assumed 

Threshold 

Discount 

Rate 

PM Mortality Benefits (Billion 2003$) 

2020 2030 

More Certain that Benefits 

Are at Least as Large 

Less Certain that Benefits 

Are at Least as Large 

14 μg/m3 c 

12 μg/m3 

10 μg/m3 d 

7.5 μg/m3 e 

3 μg/m3 f 

3% 

7% 

3% 

7% 

3% 

7% 

3% 

7% 

3% 

7% 

N/Ab 

N/A 

N/A 

N/A 

$3.3 $6.3 

$3.0 $5.7 a

 Note that this table only presents the effects of a cutpoint on PM-related mortality incidence and valuation 

estimates. b

 Not Available. We are unable to provide cutpoint analysis results for the proposed standards because of the 

analytical limitations of the PM benefits scaling procedure. c

 EPA intends to analyze a cutpoint between 12 μg/m3and 15 μg/m3 for the final RIA. d

 CASAC (2005)

68 

e

 SAB-HES (2004)69 

f

 NAS (2002)71 

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___________________________________________________________________________Cost-Benefit Analysis 

8.7 Health-Based Cost Effectiveness Analysis 

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. The Office of Management and Budget (OMB) 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, making application of CEA more difficult and less straightforward. For the CAIR 

analysis, the first to incorporate an analysis of this kind, CEA provided a useful framework for 

evaluation: nonhealth benefits were substantial, but the majority of quantified benefits came 

from health effects. EPA included in the CAIR RIA a preliminary and experimental application 

of one type of CEA—a modified quality-adjusted life-years (QALYs) approach. For CAIR, 

EPA concluded that the direct usefulness of cost-effectiveness analysis is mitigated by the lack 

of rule alternatives to compare relative effectiveness, but that comparisons could still be made to 

other benchmarks bearing in mind methodological differences. 

QALYs were developed to evaluate the effectiveness of individual medical treatments, 

and EPA is still evaluating the appropriate methods for CEA of 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 

nonhealth benefits, such as improved visibility. 

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).65 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. 

In Appendix G of the RIA for the CAIR,63 EPA conducted an extensive costeffectiveness analysis using morbidity inclusive life years (MILY). That analysis concluded that 

reductions in PM2.5 associated with CAIR were expected to be cost-saving (because the value of 

expenditures on illnesses and non-health benefits exceeded costs), and that costs of the CAIR 

could have been significantly higher and still result in cost-effective improvements in public 

8-35 
 
Draft Regulatory Impact Analysis__________________________________________________________________ 

health. Because the current analysis relies on a benefits transfer approach to estimate PM-related 

benefits, scaling PM benefits from the CAND rule, we do not have the necessary inputs to 

develop a valid cost-effectiveness measure for the proposed standards. Furthermore, the CAND 

analysis did not include a health-based CEA, the results of which might have been scaled in a 

similar fashion to the benefits. 

For the CAVR rule, EPA was able to draw inferences from the CAIR CEA by scaling the 

relative magnitude of the costs and health impacts between the two rules.66 While the CAVR 

was not expected to be cost-saving like CAIR, EPA expected that CAVR was likely to have a 

relatively low cost per MILY. For the proposed standards, however, it is difficult to draw similar 

inferences with CAIR because the geographic distribution of emission changes, the distribution 

of those changes over time, and the age distribution of the mortality and chronic disease 

reductions are all expected to differ between the two rules. For these reasons, we do not scale 

the CAIR health-based cost-effectiveness analysis for the proposed standards. 

8.8 Comparison of Costs and Benefits 

The proposed rule establishes separate standards that reduce the evaporative and exhaust 

emissions from small SI and marine SI engines. A full appreciation of the overall economic 

consequences of these provisions requires consideration of the benefits and costs expected to 

result from each standard. Due to limitations in data availability and analytical methods, 

however, we are only able to present the benefits of the entire proposed rule in the aggregate for 

both PM2.5 and ozone. There are also a number of health and environmental effects associated 

with the proposed standards that we were unable to quantify or monetize (see Table 8.1-2). 

Table 8.8-1 contains the estimates of monetized benefits of the proposed standards and 

estimated social welfare costs for each of the proposed control programs.Q The annual social 

welfare costs of all provisions of this proposed rule are described more fully in Chapter 9. The 

results in Table 8.8-1 suggest that the 2020 and 2030 monetized benefits of the proposed 

standards are much greater than the expected social welfare costs. Specifically, the annual 

benefits of the program would be approximately $2.1 + B billion annually in 2020 using a three 

percent discount rate (or $1.9 + B billion using a seven percent discount rate), compared to 

estimated social welfare costs of approximately $252 million in that same year. The net benefits 

are expected to increase to $3.4 + B billion annually in 2030 using a three percent discount rate 

(or $3.1 + B billion using a seven percent discount rate), even as the social welfare costs of that 

program fall to $241 million. 

In Table 8.8-1, we present the costs and PM-related benefits related to each of the two 

broad engine classes regulated by the proposed standards: Small SI and Marine SI engines. 

Table 8.8-1 also presents the costs and PM-related benefits related to the specific engine classes 

regulated by the proposed standards: Small SI – Class I, Class II, and Handheld (HH); Marine SI 

Q Social costs represent the welfare costs of the rule to society. These social costs do not consider transfer payments 

(such as taxes) that are simply redistributions of wealth. 

8-36 
 
___________________________________________________________________________Cost-Benefit Analysis 

– Sterndrive/Inboard (SD/I), and Outboard/Personal Water Craft (OB/PWC). Using the same 

PM scaling approach described in Section 8.2.2., we are able to split out the estimated PM 

benefits related to the different Small SI and Marine SI engine classes. One can see that in all 

cases, the PM benefits accrued by the engine classes are greater than the costs, even when fuel 

savings is not factored into the cost estimate. The benefit-to-cost ratio would be even greater if 

we estimated the ozone benefits related to the proposed standards. 

Table 8.8-1. Summary of Annual Benefits and Costs of the Proposed Standardsa 

(Millions of 2005 dollars) 

2020 2030 

Description (Millions of 2005 (Millions of 2005 

dollars) dollars) 

Estimated Social Welfare Costsb,c

 Small SI $351 $404 

Class I $145 $167 

 Class II $199 $229 

HHd $7 $8 

 Marine SI $154 $164 

SD/I $41 $44 

OB/PWC $113 $120 

Total $505 $569 

 Fuel Savings $(253) $(327) 

Total Social Welfare Costs $252 $241 

Estimated Benefitse,f 

 PM-Only Small SI Benefits 

3 percent discount rate $861 $1,280 

7 percent discount rate $782 $1,160 

Class I 

3 percent discount rate $478 $647 

7 percent discount rate $434 $587 

 Class II 

3 percent discount rate $383 $627 

7 percent discount rate $348 $570 

 PM-Only Marine SI Benefits 

3 percent discount rate $1,280 $2,110 

7 percent discount rate $1,160 $1,190 

SD/I 

3 percent discount rate $209 $487 

7 percent discount rate $190 $442 

 OB/PWC 

3 percent discount rate $1,070 $1,620 

7 percent discount rate $969 $1,470 

Total Benefitsg

 3 percent discount rate $2,140+B $3,380+B 

 7 percent discount rate $1,940+B $3,070+B 

Annual Net Benefits (Total Benefits-Total Costs)

g 

3 percent discount rate $1,890+B $3,140+B 

7 percent discount rate $1,690+B $2,830+B 

8-37 
 
Draft Regulatory Impact Analysis__________________________________________________________________ 

a All estimates are rounded to three significant digits and represent annualized benefits and costs anticipated for the years 2020 

and 2030. Columnar totals may not sum due to rounding. b Note that costs are the annual total costs of reducing all pollutants associated with each provision of the proposed control 

package, while the benefits reflect the value of reductions in PM2.5 only. c To calculate annual fixed costs, we use a 7 percent average before-tax rate of return on private capital (see Chapter 9). We do 

not present annual costs using an alternative rate of return. 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).R,S 

d

 Handheld emission reductions associated with the proposed standards, volatile organic hydrocarbons, are not accounted for in 

the PM benefits scaling approach. The PM benefit scaling approach is based upon changes in NOx and direct PM2.5 (see section 

8.2). We therefore do not estimate any PM-related benefits associated with emission reductions in the handheld engine class. e PM-related benefits in this table are nationwide. f Valuation of premature mortality based on long-term PM exposure assumes discounting over the SAB recommended 20-year 

segmented lag structure described in section 8.3. Valuation of non-fatal myocardial infarctions is based on the cost-of-illness 

over a 5-year period after the incident. The valuation of both endpoints therefore requires the use of a discount rate. We present 

the PM-related benefits results using a 3 percent and 7 percent social discount rate consistent with EPA and OMB guidelines for 

preparing economic analyses (US EPA, 2000 and OMB, 2003). g Not all possible benefits or disbenefits are quantified and monetized in this analysis. B is the sum of all unquantified benefits 

and disbenefits. Potential benefit categories that have not been quantified and monetized are listed in Table 8.1-2. 

R

U.S. Environmental Protection Agency, 2000. Guidelines for Preparing Economic Analyses. 

www.yosemite1.epa.gov/ee/epa/eed/hsf/pages/Guideline.html. S

 Office of Management and Budget, The Executive Office of the President, 2003. Circular A-4. 

http://www.whitehouse.gov/omb/circulars. 

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___________________________________________________________________________Cost-Benefit Analysis 

References for Chapter 8 

1

 U.S. Environmental Protection Agency. May 2004. Final Regulatory Analysis: Control of Emissions from 

Nonroad Diesel Engines. Prepared by: Office of Air and Radiation. Available at http://www.epa.gov/nonroaddiesel/2004fr.htm#documents. Accessed December 15, 2005. 2

 U.S. Environmental Protection Agency. February 2007. Control of Hazardous Air Pollutants from Mobile 

Sources: Regulatory Impact Analysis. Prepared by: Office of Air and Radiation. EPA420-R-07-002. Available at 

http://www.epa.gov/otaq/regs/toxics/420r07002contents.pdf. Accessed March 29, 2007. 3

 U.S. Environmental Protection Agency. October 2006. Final Regulatory Impact Analysis (RIA) for the Proposed 

National Ambient Air Quality Standards for Particulate Matter. Prepared by: Office of Air and Radiation. 

Available at http://www.epa.gov/ttn/ecas/ria.html Accessed October 18, 2006. 4

 U.S. Environmental Protection Agency. 2004. Air Quality Criteria for Particulate Matter Volume II of II. 

National Center for Environmental Assessment, Office of Research and Development. Research Triangle Park, NC. 

EPA/600/P-99/002bF. 5

 U.S. Environmental Protection Agency. September 2000. Guidelines for Preparing Economic Analyses. EPA 

240-R-00-003. 6

 U.S. Office of Management and Budget (OMB). 2003. Circular A-4 Guidance for Federal Agencies Preparing 

Regulatory Analyses, Available at: http://www/whitehouse.gov/omb/inforeg/iraguide.html. Accessed December 

15, 2005.

7

 Kunzli, N., S. Medina, R. Kaiser, P. Quenel, F. Horak Jr, and M. Studnicka. 2001. “Assessment of Deaths 

Attributable to Air Pollution: Should We Use Risk Estimates Based on Time Series or on Cohort Studies?” 

American Journal of Epidemiology 153(11):1050-55. 8

 U.S. Environmental Protection Agency. May 2004. Final Regulatory Analysis: Control of Emissions from 

Nonroad Diesel Engines. Prepared by: Office of Air and Radiation. Available at http://www.epa.gov/nonroaddiesel/2004fr.htm#documents. Accessed December 15, 2005. 9

 U.S. Environmental Protection Agency. May 2004. Final Regulatory Analysis: Control of Emissions from 

Nonroad Diesel Engines. Prepared by: Office of Air and Radiation. Available at http://www.epa.gov/nonroaddiesel/2004fr.htm#documents. Accessed December 15, 2005. 10 Abt Associates. 2005. Methodology for County-Level Mortality Rate Projections. Memorandum from Ellen 

Post and Don McCubbin (Abt Associates) to Bryan Hubbell and Zach Pekar (EPA). Sent October 25, 2005. 11 Pope, C.A., III, R.T. Burnett, M.J. Thun, E.E. Calle, D. Krewski, K. Ito, and G.D. Thurston. 2002. “Lung 

Cancer, Cardiopulmonary Mortality, and Long-term Exposure to Fine Particulate Air Pollution.” Journal of the 

American Medical Association 287:1132-1141. 12 Woodruff, T.J., J. Grillo, and K.C. Schoendorf. 1997. “The Relationship Between Selected Causes of 

Postneonatal Infant Mortality and Particulate Air Pollution in the United States.” Environmental Health 

Perspectives 105(6):608-612. 13 Abbey, D.E., B.L. Hwang, R.J. Burchette, T. Vancuren, and P.K. Mills. 1995. “Estimated Long-Term Ambient 

Concentrations of PM(10) and Development of Respiratory Symptoms in a Nonsmoking Population.” Archives of 

Environmental Health 50(2): 139-152. 14 Peters, A., D.W. Dockery, J.E. Muller, and M.A. Mittleman. 2001. “Increased Particulate Air Pollution and the 

Triggering of Myocardial Infarction.” Circulation 103:2810-2815. 15 Moolgavkar, S.H. 2003. “Air Pollution and Daily Deaths and Hospital Admissions in Los Angeles and Cook 

Counties.” In Revised Analyses of Time-Series Studies of Air Pollution and Health. Special Report. Boston, MA: 

Health Effects Institute. 16 Ito, K. 2003. “Associations of Particulate Matter Components with Daily Mortality and Morbidity in Detroit, 

Michigan.” In Revised Analyses of Time-Series Studies of Air Pollution and Health. Special Report. Health Effects 

Institute, Boston, MA. 17 Moolgavkar, S.H. 2000. “Air Pollution and Hospital Admissions for Diseases of the Circulatory System in Three 

U.S. Metropolitan Areas.” Journal of the Air and Waste Management Association 50:1199-1206. 
 18 Sheppard, L. 2003. “Ambient Air Pollution and Nonelderly Asthma Hospital Admissions in Seattle, Washington, 
 

1987-1994.” In Revised Analyses of Time-Series Studies of Air Pollution and Health. Special Report. Boston, MA: 
 

Health Effects Institute. 
 

8-39 
 
Draft Regulatory Impact Analysis__________________________________________________________________ 

19 Norris, G., S.N. YoungPong, J.Q. Koenig, T.V. Larson, L. Sheppard, and J.W. Stout. 1999. “An Association 
 

between Fine Particles and Asthma Emergency Department Visits for Children in Seattle.” Environmental Health
 

Perspectives 107(6):489-493. 
 20 Dockery, D.W., J. Cunningham, A.I. Damokosh, L.M. Neas, J.D. Spengler, P. Koutrakis, J.H. Ware, M. Raizenne,
 

and F.E. Speizer. 1996. “Health Effects of Acid Aerosols On North American Children-Respiratory Symptoms.” 
 

Environmental Health Perspectives 104(5):500-505. 
 21 Pope, C.A., III, D.W. Dockery, J.D. Spengler, and M.E. Raizenne. 1991. “Respiratory Health and PM10
 

Pollution: A Daily Time Series Analysis.” American Review of Respiratory Diseases 144:668-674. 
 22 Schwartz, J., and L.M. Neas. 2000. “Fine Particles are More Strongly Associated than Coarse Particles with 
 

Acute Respiratory Health Effects in Schoolchildren.” Epidemiology 11:6-10. 
 23 Ostro, B., M. Lipsett, J. Mann, H. Braxton-Owens, and M. White. 2001. “Air Pollution and Exacerbation of 
 

Asthma in African-American Children in Los Angeles.” Epidemiology 12(2):200-208. 
 24 Vedal, S., J. Petkau, R. White, and J. Blair. 1998. “Acute Effects of Ambient Inhalable Particles in Asthmatic 
 

and Nonasthmatic Children.” American Journal of Respiratory and Critical Care Medicine 157(4):1034-1043. 
 25 Ostro, B.D. 1987. “Air Pollution and Morbidity Revisited: A Specification Test.” Journal of Environmental
 

Economics Management 14:87-98. 
 26 Ostro, B.D. and S. Rothschild. 1989. “Air Pollution and Acute Respiratory Morbidity: An Observational Study 
 

of Multiple Pollutants.” Environmental Research 50:238-247.
 27 Mrozek, J.R., and L.O. Taylor. 2002. “What Determines the Value of Life? A Meta-Analysis.” Journal of
 

Policy Analysis and Management 21(2):253-270. 
 28 Viscusi, V.K., and J.E. Aldy. 2003. “The Value of a Statistical Life: A Critical Review of Market Estimates 
 

Throughout the World.” Journal of Risk and Uncertainty 27(1):5-76. 
 29 Viscusi, W.K., W.A. Magat, and J. Huber. 1991. “Pricing Environmental Health Risks: Survey Assessments of
 

Risk-Risk and Risk-Dollar Trade-Offs for Chronic Bronchitis.” Journal of Environmental Economics and 
 

Management 21:32-51. 
 30 Cropper, M.L., and A.J. Krupnick. 1990. “The Social Costs of Chronic Heart and Lung Disease.” Resources for 
 

the Future. Washington, DC. Discussion Paper QE 89-16-REV. 
 31 Russell, M.W., D.M. Huse, S. Drowns, E.C. Hamel, and S.C. Hartz. 1998. “Direct Medical Costs of Coronary 
 

Artery Disease in the United States.” American Journal of Cardiology 81(9):1110-1115. 
 32 Wittels, E.H., J.W. Hay, and A.M. Gotto, Jr. 1990. “Medical Costs of Coronary Artery Disease in the United 
 

States.” American Journal of Cardiology 65(7):432-440. 
 33 Agency for Healthcare Research and Quality (AHRQ). 2000. HCUPnet, Healthcare Cost and Utilization Project. 
 

Rockville, MD. http://www.ahrq.gov/HCUPnet/. 
 34 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. 
 35 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. 
 36 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. 
 37 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. 
 38 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. 
 39 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. 
 40 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. 
 

8-40 
 
___________________________________________________________________________Cost-Benefit Analysis 

41 Pope, C.A., III, R.T. Burnett, M.J. Thun, E.E. Calle, D. Krewski, K. Ito, and G.D. Thurston. 2002. “Lung 

Cancer, Cardiopulmonary Mortality, and Long-term Exposure to Fine Particulate Air Pollution.” Journal of the 

American Medical Association 287:1132-1141. 42 Woodruff, T.J., J. Grillo, and K.C. Schoendorf. 1997. “The Relationship Between Selected Causes of 

Postneonatal Infant Mortality and Particulate Air Pollution in the United States.” Environmental Health 

Perspectives 105(6):608-612. 43 Pope, C.A., III, R.T. Burnett, M.J. Thun, E.E. Calle, D. Krewski, K. Ito, and G.D. Thurston. 2002. “Lung 

Cancer, Cardiopulmonary Mortality, and Long-term Exposure to Fine Particulate Air Pollution.” Journal of the 

American Medical Association 287:1132-1141. 44 Woodruff, T.J., J. Grillo, and K.C. Schoendorf. 1997. “The Relationship Between Selected Causes of 

Postneonatal Infant Mortality and Particulate Air Pollution in the United States.” Environmental Health 

Perspectives 105(6):608-612. 45 U.S. Office of Management and Budget (OMB). 2003. Circular A-4 Guidance for Federal Agencies Preparing 

Regulatory Analyses, Available at: http://www/whitehouse.gov/omb/inforeg/iraguide.html. Accessed December 

15, 2005.

46 U.S. Office of Management and Budget (OMB). 2003. Circular A-4 Guidance for Federal Agencies Preparing 

Regulatory Analyses, Available at: http://www/whitehouse.gov/omb/inforeg/iraguide.html. Accessed December 

15, 2005.

47 U.S. Environmental Protection Agency. March 2005. Regulatory Impact Analysis for the Final Clean Air 

Interstate Rule. Prepared by: Office of Air and Radiation. Available at http://www.epa.gov/cair. Accessed 

December 15, 2005. 48 U.S. Environmental Protection Agency (EPA). 1996. Review of the National Ambient Air Quality Standards for 

Ozone: Assessment of Scientific and Technical Information. Office of Air Quality Planning and Standards, Research 

Triangle Park, NC, EPA report no. EPA/4521R-96-007. 

49 Garcia, P., B. Dixon, and J. Mjelde. 1986. “Measuring the Benefits of Environmental Change Using a Duality 

Approach: The Case of Ozone and Illinois Cash Grain Farms.” Journal of Environmental Economics and 

Management 13:69-80. 50 Fox, S., and R.A. Mickler. 1996. “Impact of Air Pollutants on Southern Pine Forests.” Ecological Studies 118. 

New York: Springer Verlag. 51 EPA-SAB-COUNCIL-ADV-98-003. 1998. “Advisory Council on Clean Air Compliance Analysis Advisory on 

the Clean Air Act Amendments (CAAA) of 1990 Section 812 Prospective Study: Overview of Air Quality and 

Emissions Estimates: Modeling, Health and Ecological Valuation Issues Initial Studies.” 52 Grosclaude, P., and N.C. Soguel. 1994. “Valuing Damage to Historic Buildings Using a Contingent Market: A 

Case Study of Road Traffic Externalities.” Journal of Environmental Planning and Management 37: 279-287. 53 U.S. Environmental Protection Agency. 2005. Air Quality Criteria for Ozone and Related Photochemical 

Oxidants (First External Review Draft). January. http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=114523 54 EPA, 2005. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Second External Review Draft). 

August. http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=137307 55 U.S. Environmental Protection Agency. March 2005. Regulatory Impact Analysis for the Final Clean Air 

Interstate Rule. Prepared by: Office of Air and Radiation. Available at http://www.epa.gov/cair. Accessed 

December 15, 2005. 56 U.S. Environmental Protection Agency. June 2005. Regulatory Impact Analysis for the Final Clean Air Visibility 

Rule or the Guidelines for Best Available Retrofit Technology (BART) Determinations Under the Regional Haze 

Regulations. Prepared by: Office of Air and Radiation. Available at 

http://www.epa.gov/visibility/pdfs/bart_ria_2005_6_15.pdf. Accessed December 15, 2005. 57 Krewski D., R.T. Burnett, M.S. Goldbert, K. Hoover, J. Siemiatycki, M. Jerrett, M. Abrahamowicz, and W.H. 

White. July 2000. Reanalysis of the Harvard Six Cities Study and the American Cancer Society Study of 

Particulate Air Pollution and Mortality. Special Report to the Health Effects Institute, Cambridge MA. 58 EPA-SAB-COUNCIL_ADV_04-002. March 2004. Advisory on 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: 

Advisory by the Health Effects Subcommittee of the Advisory Council on Clean Air Compliance Analysis. 

8-41 
 
Draft Regulatory Impact Analysis__________________________________________________________________ 

59 Laden, F., J. Schwartz, F.E. Speizer, and D.W. Dockery. 2006. Reduction in Fine Particulate Air Pollution and
 

Mortality. American Journal of Respiratory and Critical Care Medicine. 173: 667-672.
 60 U.S. EPA. 2004. Air Quality Criteria for Particulate Matter, Volume II. Office of Research and Development. 
 

EPA/600/P-99/002bF, October. 
 61 U.S. Environmental Protection Agency. October 2006. Final Regulatory Impact Analysis (RIA) for the Proposed
 

National Ambient Air Quality Standards for Particulate Matter. Prepared by: Office of Air and Radiation. 
 

Available at http://www.epa.gov/ttn/ecas/ria.html Accessed October 18, 2006. 
 62 Clean Air Science Advisory Committee. June 2005. EPA’s Review of the National Ambient Air Quality 
 

Standards for Particulate Matter (Second Draft PM Staff Paper, January 2005). A Review by the PM Review Panel
 

of the EPA Clean Air Science Advisory Committee. EPASAB-CASAC-05-007. 
 63 EPA-SAB-COUNCIL_ADV_04-002. March 2004. Advisory on 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: 
 

Advisory by the Health Effects Subcommittee of the Advisory Council on Clean Air Compliance Analysis.
 64 National Research Council (NRC). 2002. Estimating the Public Health Benefits of Proposed Air Pollution 
 

Regulations. Washington, DC: The National Academies Press. 
 65 Miller W, Robinson LA, Lawrence RS, eds. Valuing Health: Cost Effectiveness Analysis for Regulation. 
 

Committee to Evaluate Measures of Health Benefits for Environmental, Health, and Safety Regulation (Lawrence 
 

RS, chair), Board on Health Care Services, Institute of Medicine, National Academy Press, Washington D.C., 2006. 
 66 U.S. Environmental Protection Agency. June 2005. Regulatory Impact Analysis for the Final Clean Air Visibility 
 

Rule or the Guidelines for Best Available Retrofit Technology (BART) Determinations Under the Regional Haze 
 

Regulations. Prepared by: Office of Air and Radiation. Available at
 

http://www.epa.gov/visibility/pdfs/bart_ria_2005_6_15.pdf. Accessed December 15, 2005.
 

8-42 
 
Economic Impact Analysis 

CHAPTER 9: Economic Impact Analysis 

We prepared a draft Economic Impact Analysis (EIA) to estimate the economic impacts 

of the proposed 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 proposed program to be about $241 million in 

2030.1, 2 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 $569 million in 2030. 

Consumers of Small SI and Marine products are expected to bear about 75 percent of these costs. 

Small SI engine and equipment manufacturers are expected to bear 6 percent and 19 percent, 

respectively. We estimate fuel savings of about $327 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 9.1 percent ($17 per unit). The average price increase for Marine 

SI engines is expected to be about 1.7 percent ($195 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 2.1 percent 

($178 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 

1

All estimates presented in this section are in 2005$. 

2

This analysis is based on an earlier version of the engineering costs developed for this rule. The net 

present value of the engineering costs used in this analysis (without taking the fuel savings into account, at a 3 

percent discount rate over the period of the analysis) is $10.0 billion, which is about $100 million less than the net 

present value of the final estimated engineering costs, $10.1 billion. We do not expect that a difference of this 

magnitude would change the overall results of this economic impact analysis, in terms of market impacts and how 

the costs are expected to be shared among stakeholders. 

9-1 
Draft Regulatory Impact Analysis 

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 proposed emission control program can be expected to 

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 proposed 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 proposed 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 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 demand). A price elasticity of 

9-2 
Economic Impact Analysis 

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 

andwere estimated using well-established econometric methods. It 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 6 engine 

categories, depending on engine class and useful life (Class I: UL125, UL250, and UL500; 

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 proposed 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 proposed 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 

9-3 
Draft Regulatory Impact Analysis 

supply of personal watercraft, and vice versa. Production and consumption of each of these 

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 proposed 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 ). 

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 

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). 

9-4 
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 Perfectly competitive Perfectly 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: 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 
Draft 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 the sum of fixed and 

variable costs. For the market analysis, this leads to a small increase in estimated price impacts 

for the years 2011 through 2016, the period during which fixed costs are recovered. The 

increase is small because, for many elements of the program, annual per unit fixed costs are 

smaller than annual per unit variable costs. 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 

proposed 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 2013, 2018, 

and 2030. These years were chosen because 2013 is the year of highest compliance; after 2018, 

the fixed costs are recovered and the market impacts reflect variable costs as well as growth in 

equipment population; 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 

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 

9-6 
Economic Impact Analysis 

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.3 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 2013, the high cost year, is estimated 

to be about 2.3 percent, or $257. By 2018, this average price increase is expected to decline to 

about 1.7 percent, or $196, 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 

2013 is about 2.0 percent, or 8,800 engines. This decreases to about 1.6 percent in 2018, or 

about 7,000 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 2013 is expected to be about 1.3 percent, or 

$232. By 2018, this average price increase is expected to decline to about 1 percent, or $178. 

These price increases are expected to vary across vessel categories. The category with the 

largest price increase in 2013 is expected to be personal watercraft engines, with an estimated 

price increase of about 2.8 percent in 2013; this is expected to decrease to 2.1 percent in 2018. 

3

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 
Draft Regulatory Impact Analysis 

The smallest expected change in 2013 is expected to be for sterndrive/inboards and outboard 

recreational vessels, which are expected to see price increases of about 0.7 percent. The market 

impact analysis predicts that with these increases in vessel prices the expected average decrease 

in quantity produced in 2013 is about 2.7 percent, or 11,000 vessels. This is expected to 

decrease to about 2.0 percent in 2018, or about 8,600 vessels. The personal watercraft category 

is expected to experience the largest decline in 2013, about 5.6 percent (4,800 vessels). The 

smallest percentage decrease in production is expected for sterndrive/inboards at 1.4 percent 

(1,300 vessels); the smallest absolute decrease in quantity is expected for outboard recreational 

vessels, at 113 vessels (1.5 percent). 

9.1.4.1.2 Small SI Market Analysis 

The average price increase for Small SI engines in 2013, the high cost year, is estimated 

to be about 11.7 percent, or $22. By 2018, this average price increase is expected to decline to 

about 9.1 percent, or $17, 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 

2013 is expected to be about 2.3 percent, or 371,000 engines. This is expected to decrease to 

about 1.7 percent in 2018, or about 299,000 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 2013 is expected 

to be about 3.1 percent, or $14. By 2018, this average price increase is expected to decline to 

about 2.4 percent, or $10. The average price increase and quantity decrease differs by category 

of equipment. As shown in Table XII.F-2, the price increase for Class I equipment is estimated 

to be about 6.9 percent ($19) in 2013, decreasing to 5.5 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 2013 is about 2.2 percent, or 219,400 

units. This is expected to decrease to about 1.8 percent in 2018, or about 189,700 units. For 

Class II equipment, a higher price increase is expected, about 3.9 percent ($41) in 2013, 

decreasing to 2.6 percent ($25) in 2018. The expected average decrease in the quantity of Class 

II equipment produced in 2013 is about 4.3 percent, or 157,300 units, decreasing to 2.8 percent, 

or about 114,000 units, in 2018. 

For the handheld equipment market, prices are expected to increase about 0.3 percent for 

all years, and quantities are expected to decrease about 0.6 percent. 

9-8 
Economic Impact Analysis 

Table 9.1-2: Summary of Estimated Market Impacts for 2013, 2018, 2030 (2005$) 

Market Change in Price Change in Quantity 

Absolute Percent Absolute Percent 

2013 

Marine

 Engines $257 2.3% -8,846 -2.0%

 Equipment $232 1.3% -10,847 -2.7%

 SD/I $252 0.7% -1,336 -1.4%

 OB Recreational $638 0.7% -113 -1.5%

 OB Luxury $206 1.1% -4,579 -2.1%

 PWC $237 2.8% -4,819 -5.6% 

Small SI

 Engines $22 11.7% -371,097 -2.3%

 Equipment $14 3.1% -482,942 -1.9%

 Class I $19 6.9% -219,400 -2.2%

 Class II $41 3.9% -157,306 -4.3%

 HH $0.3 0.3% -106,236 -0.6% 

2018 

Marine

 Engines $196 1.7% -7,002 -1.6%

 Equipment $178 1.0% -8,563 -2.0%

 SD/I $195 0.5% -1,072 -1.1%

 OB Recreational $496 0.6% -91 -1.1%

 OB Luxury $160 0.8% -3,634 -1.6%

 PWC $178 2.1% -3,766 -4.2% 

Small SI

 Engines $17 9.1% -298,988 -1.7%

 Equipment $10 2.4% -401,025 -1.4%

 Class I $15 5.5% -189,771 -1.8%

 Class II $25 2.6% -113,999 -2.8%

 HH $0.2 0.3% -97,255 -0.5% 

2030 

Marine

 Engines $195 1.7% -7,728 -1.6%

 Equipment $179 1.0% -9,333 -2.0%

 SD/I $195 0.5% -1,161 -1.1%

 OB Recreational $496 0.6% -98 -1.1%

 OB Luxury $160 0.8% -3,998 -1.7%

 PWC $178 2.1% -4,076 -4.2% 

Small SI

 Engines $17 9.1% -354,915 -1.7%

 Equipment $10 2.4% -475,825 -1.4%

 Class I $15 5.6% -225,168 -1.8%

 Class II $25 2.6% -135,400 -2.8%

 HH $0.2 0.3% -115,257 -0.5% 

9-9 
Draft Regulatory Impact Analysis 

9.1.4.2 Economic Welfare Results 

In the economic welfare analysis we look at the costs to society of the proposed 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 2038 

(2005$, $million) 

Year 

Total 

Engineering 

Costs 

Total Social 

Costs Fuel Savings 

Net Engineering 

Costs 

(including fuel 

savings) 

Net Social 

Costs 

(including fuel 

savings) 

2008 $9.5 $9.5 $3.1 $6.4 $6.4 

2009 $171.7 $168.8 $13.7 $157.9 $155.1 

2010 $191.1 $188.0 $25.4 $165.7 $162.6 

2011 $470.5 $463.4 $64.9 $405.7 $398.5 

2012 $647.3 $638.2 $103.5 $543.8 $534.7 

2013 $652.5 $643.4 $136.5 $516.0 $506.9 

2014 $621.1 $613.1 $161.2 $459.9 $451.9 

2015 $627.0 $619.0 $182.3 $444.7 $436.7 

2016 $520.9 $515.2 $200.9 $320.0 $314.2 

2017 $492.6 $487.5 $216.2 $276.4 $271.3 

2018 $497.2 $492.0 $229.9 $267.3 $262.1 

2019 $503.6 $498.4 $242.1 $261.5 $256.2 

2020 $510.0 $504.7 $253.1 $256.9 $251.6 

2021 $516.4 $511.0 $263.3 $253.1 $247.8 

2022 $522.7 $517.3 $272.9 $249.8 $244.4 

2023 $529.1 $523.7 $281.4 $247.7 $242.3 

2024 $535.8 $530.3 $289.3 $246.5 $241.0 

2025 $542.3 $536.7 $296.6 $245.6 $240.0 

2026 $548.7 $543.1 $303.6 $245.1 $239.5 

2027 $555.2 $549.4 $310.1 $245.1 $239.3 

2028 $561.6 $555.8 $316.3 $245.3 $239.5 

2029 $568.0 $562.2 $322.0 $246.1 $240.2 

2030 $574.5 $568.6 $327.3 $247.2 $241.3 

2031 $580.9 $575.0 $332.3 $248.6 $242.6 

2032 $587.4 $581.3 $337.1 $250.3 $244.2 

2033 $593.8 $587.7 $341.7 $252.1 $246.0 

2034 $600.3 $594.1 $346.1 $254.2 $248.0 

2035 $606.7 $600.5 $350.4 $256.3 $250.1 

2036 $613.1 $606.9 $354.5 $258.6 $252.3 

2037 $619.6 $613.2 $358.5 $261.1 $254.7 

2038 $626.0 $619.6 $362.5 $263.6 $257.1 

NPV at 3%a $9,996.2 $9,882.2 $4,356.2 $5,640.1 $5,562.0 

NPV at 7%a $5.863.6 $5,794.1 $2,291.5 $3,572.1 $3,502.6 a EPA 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 
Draft Regulatory Impact Analysis 

Figure 9.1-1: Estimated Engineering, Total Social, Net Social Costs and Fuel Savings 

$0.0 

$100.0 

$200.0 

$300.0 

$400.0 

$500.0 

$600.0 

$700.0 

20082010201220142016 

201820202022202420262028 2030

2032203420362038 

$, million 

Total Engineering Costs Total Social Costs 

Fuel Savings Net Social Costs 

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 66 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 22 percent of that 

program, and engine manufacturers the remaining 11 percent. In the Small SI market, 

consumers are expected to bear 79 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 17 percent of 

that program, and engine manufacturers the remaining 4 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 2013, 2018, 2030 (2005$, $million) 

Market 

Absolute Change 

in Surplus 

Percent Change in 

Surplus 

Fuel 

Savings 

Total Change in 

Surplus 

2013 

Marine SI

 Engine Manufacturers -$21.54 11% -$21.54

 Equipment Manufacturers -$42.23 22% -$42.23

 End User (Households) -$125.14 66% $42.27 -$82.87 

Subtotal -$188.91 -$146.64 

Small SI

 Engine Manufacturers -$18.36 4% -$18.36

 Equipment Manufacturers -$80.16 18% -$80.16

 End User (Households) -$355.95 78% $94.26 -$261.69 

Subtotal -$454.47 -$360.21 

TOTAL -$643.38 $136.53 -$506.85 

2018 

Marine SI

 Engine Manufacturers -$17.29 11% -$17.29

 Equipment Manufacturers -$34.02 22% -$34.02

 End User (Households) -$100.19 66% $87.12 -$13.07 

Subtotal -$151.50 -$64.38 

Small SI

 Engine Manufacturers -$13.89 4% -$13.89

 Equipment Manufacturers -$57.65 17% -$57.65

 End User (Households) -$268.95 79% $142.78 -$126.17 

Subtotal -$340.49 -$197.71 

TOTAL -$491.99 $229.90 -$262.09 

2030 

Marine SI

 Engine Manufacturers -$18.81 11% -$18.81

 Equipment Manufacturers -$36.97 23% -$36.97

 End User (Households) -$108.52 66% $149.36 $40.84 

Subtotal -$164.30 -$14.94 

Small SI

 Engine Manufacturers -$16.49 4% -$16.49

 Equipment Manufacturers -$68.45 17% -$68.45

 End User (Households) -$319.31 79% $177.89 -$141.42 

Subtotal -$404.25 -$226.36 

TOTAL -$568.55 $327.25 -$241.30 

Table 9.1-5 contains more detailed information on the sources of the social costs for 

2013. This table shows that vessel and equipment manufacturers are expected to bear more of 

the burden of the program than engine manufacturers. On the marine side, the loss of producer 

surplus for the 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. Vessel manufacturers would not 

be able to pass along a greater share of the engine and vessel compliance costs to end consumers 

due to the elastic price elasticity of demand for consumers of these vessels. On the Small SI 

side, equipment manufacturers can pass on more of the compliance costs to end consumers 

9-13 
Draft Regulatory Impact Analysis 

because the price elasticity of demand in these markets is less elastic. 

Table 9.1-5: Estimated Surplus Changes by Market and Stakeholder for 2013 

(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 

Marine SI 

$133.2 -$21.5 

$59.1 -$42.2 

-$18.7 

-$23.6 

-$125.1 

-$91.8 

-$33.3 

$192.2 -$63.8 -$125.1 

-$21.5 

-$42.2 

-$125.1 

-$188.9 

$42.3 

$42.3 

-$21.5 

-$42.2 

-$82.8 

-$146.6 

Engine Manufacturers 

 Equipment Manufacturers 

Engine Price Changes 

Equipment Cost Changes 

End User (Households) 

Engine Price Changes 

Equipment Cost Changes 

Subtotal 

Small SI 

$371.9 -$18.4 

$88.4 -$80.2 

-$59.0 

-$21.1 

-$355.9 

-$289.8 

-$66.1 

$460.3 -$98.5 -$355.9 

-$18.4 

-$80.2 

-$355.9 

-$454.5 

$94.3 

$94.3 

-$18.4 

-$80.2 

-$261.7 

-$360.2 

TOTAL $652.5 -$162.3 -$481.1 -$643.4 $136.6 -$506.8 

The present value of net social costs of the proposed standards through 2038 at a 3 

percent discount rate, shown in Table XII.F-6, is estimated to be $5.5 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 2038 is estimated to be 

$3.5 billion, including the fuel savings. 

9-14 
Economic Impact Analysis 

Table 9.1-6. Estimated Net Social Costs Through 2038 by Stakeholder (2005$, $million) 

Market 

Total Change in 

Surplus 

Percentage Change 

in Total Surplus Fuel Savings 

Net Change in 

Surplus 

Marine SI

 Engine Manufacturers 

 Equipment Manufacturers 

End User (Households) 

Subtotal 

Small SI

 Engine Manufacturers 

 Equipment Manufacturers 

End User (Households) 

Subtotal 

TOTAL 

Net Present Value 3% 

-$354.4 11% 

-$688.8 22% 

-$2,058.8 66% 

-$3,102.0 

-$275.0 4% 

-$1,171.8 17% 

-$5,333.4 79% 

-$6,780.2 

-$9,882.2 

$1,831.3 

$1,831.3 

$2,524.8 

$2,524.8 

$4,356.1 

-$354.4 

-$688.8 

-$227.5 

-$1,270.7 

-$275.0 

-$1,171.8 

-$2,808.6 

-$4,255.4 

-$5,526.1 

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% 

-$216.4 11% 

-$417.6 22% 

-$1,259.9 66% 

-$1,893.8 

-$157.8 4% 

-$680.4 17% 

-$3,062.1 79% 

-$3,900.3 

-$5,794.2 

$937.1 

$937.1 

$1,354.4 

$1,354.4 

$2,291.5 

-$216.4 

-$471.6 

-$322.8 

-$956.8 

-$157.8 

-$680.4 

-$1,707.7 

-$2,545.9 

-$3,502.6 

9-15 
Draft 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 illustrate how the costs 

9-16 
Economic Impact Analysis 

flow 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 
Draft Regulatory Impact Analysis 

This analysis uses a partial equilibrium approach in that it models only those markets that 

are directly affected by the proposed 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 proposed 

controls in the agricultural and construction sectors. This is appropriate because the vast 

majority of engines and equipment that would be subject to the proposed 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 proposed 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 Perfect Competition Model 

For all markets that are modeled, the analyst must characterize the degree of competition 

within each market. The discussion generally focuses on perfect competition (price-taking 

9-18 
Economic Impact Analysis 

behavior) versus imperfect competition (the lack of price-taking behavior). This EIM is abased 

on an assumption of perfect competition. This means that consumers and firms are price takers 

and do not have the ability to influence market prices. 

In a perfectly competitive market at equilibrium the market price equals the value society 

(consumers) places on the marginal product, as well as the marginal cost to society (producers). 

Producers are price takers, in that they respond to the value that consumers put on the product. It 

should be noted that the perfect competition assumption is not primarily about the number of 

firms in a market. It is about how the market operates: whether or not individual firms have 

sufficient market power to influence the market price. Indicators that allow us to assume perfect 

competition include absence of barriers to entry, absence of strategic behavior among firms in 

the market, and product differentiation.4

 Finally, 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 contrast, imperfect competition implies firms 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 proposed 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). 

Perfect competition is a widely accepted economic practice for this type of analysis and 

only in rare cases are other approaches used (EPA 2000, p. 126). For the markets under 

consideration in this EIA, we assume the perfectly competitive market structure. This is because 

these markets 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. 

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 
Draft Regulatory Impact Analysis 

As described in the industry profiles for this proposed 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 perfect competition is justified. Among the mitigating 

factors are the presence of substantial import competition, relative ease of entry, existing excess 

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 perfect 

competition 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 

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 

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). 

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. 

9-21 
Draft Regulatory Impact Analysis 

Figure 9.2-1: Short Run: All Costs Born by Producers 

Price 

Q

S 

P 

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 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 perfectly 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. 

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 

Figure 9.2-2: Long Run: Full-Cost Pass-Through 

$ d 

c b S1

: With Regulation 

}Unit Cost Increase 

a P0
 S0

: Without Regulation 

D 

Q Output 1 Q0 

Increase 


 }P1 Price 

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. 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. 

9-23 
Draft Regulatory Impact Analysis 

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 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. 

9-24 
Economic Impact Analysis 

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. 

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 

9-25 
Draft Regulatory Impact Analysis 

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 proposed 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. 

As indicated in Figure 9.2-4, when the proposed 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 proposed 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 proposed 

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. 

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 

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 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

Draft Regulatory Impact Analysis 

Figure 9.2-5: Derived Demand for Engines 

Price 

Equipment 

($/Q) 

ΔPE 

Q – Equipment ΔQE 

DE 

N

SE 

SE 

Price 

Engines 

($/Q) 

ΔPeng 

Seng 

Q – Engines 

Derived 

Demand 

ΔQ 

} Unit Cost Increase 

SN

eng 

eng 

ΔQE = ΔQeng 

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 
Draft 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 

Q2 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 
Draft Regulatory Impact Analysis 

Figure 9.2-7: Modeling Fixed Costs 

$/q 

PmN

Pm 

MCN

ATAC 

ATACN

MC 

TVCC 

q 

TCC 

q 

C2 = 

C1 = 

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 and variable compliance costs. 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 

proposed 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 by the full amount of the 

compliance costs (both fixed and variable) to attempt to recover those 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. To reflect these 

conditions, the supply shift in this EIM is based on both fixed and variable costs, even though 

the model assumes perfect competition. A sensitivity analysis was performed to investigate the 

impacts under the alternative scenario of shifting the supply curve by the variable costs only. 

The results of that analysis can be found in Appendix 9H. 

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 proposed 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 proposed 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 directioninjection 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 to 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. 

9-33 
Draft Regulatory Impact Analysis 

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 

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 proposed 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. 

9-34 
Economic Impact Analysis 

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 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 proposed 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 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 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 price increase 

if it is the only entity affected by that price increase. In such a case, retailers would clearly have 

an incentive to purchase comparable engines or equipment that were not affected by the price 

increase, placing the affected firm at a competitive disadvantage and reducing its market share. 

However, in this case all engine manufacturers will face increased 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 

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, 

9-35 
Draft Regulatory Impact Analysis 

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 proposed 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, 

compressors, and construction, agricultural, and small industrial equipment, as well as some 

recreational and utility vehicles and snowblowers. 

9-36 
Economic Impact Analysis 

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 

engines. These assumptions are reasonable given the nature of this equipment and because 

9-37 
Draft Regulatory Impact Analysis 

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 proposed standards for HH 

consist only of evaporative emission controls and tThe 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 two-market 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 proposed program. The 

proposed 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 combination 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 proposed 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 proposed 

9-39 
Draft Regulatory Impact Analysis 

standards, so the proposed standards will codify what is already happening in the industry and 

force new entrants 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 proposed 

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 23,000 out of a total of 378,500 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 15 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 

PWC XXX XXX XXX 

SD/I Recreation XXX XXX XXX 

SD/I Luxury XXX XXX 

OB Recreational XXX XXX XXX XXX XXX 

OB Luxury XXX 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) 

9-41 
Draft Regulatory Impact Analysis 

• OB luxury (yacht, cruiser, express fish) 

• 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 

9-42 
Economic Impact Analysis 

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 

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 
Draft 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 

5,895,682 

NA 

647,256 

271,391 

579,773 

7,675 

8,748 

631,264 

NA 

NA 

29,058 

62,078 

5,287 

6,026 

434,859 

NA 

NA 

20,017 

42,763 

71,380 

173,846 

NA 

1,701,351 

127,915 

605,169 

253,971 

15,503 

37,758 

NA 

369,523 

27,782 

131,439 

55,161 

17,585 

42,827 

NA 

419,134 

31,512 

149,086 

62,576 

189,112 

350,908 

6,961,805 

2,490,008 

834,465 

1,206,160 

1,056,322 

Snowblowers 551,506 59,051 40,679 475,353 103,244 117,105 1,346,938 

Total 8,098,993 797,874 549,631 3,408,985 740,410 839,816 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 

$87 

9-44 
Economic Impact Analysis 

Table 9.3-10: Small SI Nonhandheld Engine and 

Equipment Equilibrium (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 20,825 57,257 3,767 81,849 

SD/I Recreational 15,069 35,668 25,975 76,712 

SD/I Luxury 9,565 12,960 22,525 

OB Recreational 38,529 52,858 79,083 46,229 42,680 259,380 

OB Luxury 9,043 9,043 18,087 

OB loose engines 32,667 32,667 

Total 71,196 52,858 99,909 127,599 100,724 38,935 491,220 

9-45 
Draft 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 20,825 57,257 3,767 81,849 

SD/I Recreational 15,069 34,894 25,645 75,608 

SD/I Luxury 7,630 8,542 16,172 

OB Recreational 30,823 42,287 61,182 35,765 33,019 203,076 

OB Luxury 3,617 3,617 7,235 

Total 30,823 42,287 82,007 111,708 82,928 34,186 383,940 

9.3.2.2.2 Marine SI Engine and Vessel InitialEquilibrium 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 proposed 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. 

The fixed cost portion of the engineering costs incorporate a 7 percent cost of capital 

recovered over the first five years of the exhaust standards even though the costs actually occur 

prior to the beginning of the program. The period of recovery is 2011 through 2015 for Class I 

Small SI engines and 2012 through 2016 for Class II Small SI engines. Marine engine fixed 

costs are recovered over the period 2009 through 2013 for engines and 2011 through 2016 for 

vessels, PWC, and outboards <25 hp. The other marine vessels have a small amount of fixed 

costs associated with the evaporative controls. 

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 nine sets of engine compliance costs for NHH engines, one for each engine market. 

These costs begin in 2009 for HH and 2008 for 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 proposed 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 all Class II equipment was applied in 

this analysis to each of the equipment categories. 

9-47 
Draft Regulatory Impact Analysis
 

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 $0.00 $0.81 $0.81 $0.81 $0.81 $0.81 $0.69 $0.69 $0.69 

Fixed $0.00 $0.00 $0.01 $0.01 $0.01 $0.01 $0.01 $0.00 $0.00 $0.00 

Total $0.00 $0.00 $0.82 $0.82 $0.82 $0.82 $0.82 $0.69 $0.69 $0.69 

Nonhandheld 

1 125 Variable $0.33 $0.33 $0.33 $0.33 $13.30 $13.17 $13.19 $13.19 $13.19 $11.95 

Fixed $0.02 $0.02 $0.02 $0.02 $1.53 $1.49 $1.47 $1.46 $1.44 $0.19 

Total $0.35 $0.35 $0.35 $0.35 $14.83 $14.66 $14.66 $14.64 $14.63 $12.14 

1 250 Variable $0.33 $0.33 $0.33 $0.33 $15.64 $15.51 $15.53 $15.53 $15.53 $14.21 

Fixed $0.02 $0.02 $0.02 $0.02 $4.91 $4.81 $4.74 $4.67 $4.60 $0.19 

Total $0.35 $0.35 $0.35 $0.35 $20.55 $20.32 $20.26 $20.19 $20.13 $14.40 

1 500 Variable $0.33 $0.33 $0.33 $0.33 $19.46 $19.33 $19.35 $19.35 $19.35 $17.73 

Fixed $0.02 $0.02 $0.02 $0.02 $7.03 $6.89 $6.79 $6.68 $6.59 $0.19 

Total $0.35 $0.35 $0.35 $0.35 $26.49 $26.22 $26.13 $26.03 $25.93 $17.92 

1 125 

Snowblower 

Variable $0.33 $0.33 $0.33 $0.33 $2.69 $2.56 $2.58 $2.58 $2.58 $2.10 

Fixed $0.02 $0.02 $0.02 $0.02 $0.47 $0.45 $0.45 $0.45 $0.45 $0.19 

Total $0.35 $0.35 $0.35 $0.35 $3.16 $3.01 $3.03 $3.03 $3.03 $2.29 

1 250 

Snowblower 

Variable $0.33 $0.33 $0.33 $0.33 $2.69 $2.56 $2.58 $2.58 $2.58 $2.10 

Fixed $0.02 $0.02 $0.02 $0.02 $0.47 $0.45 $0.45 $0.45 $0.45 $0.19 

Total $0.35 $0.35 $0.35 $0.35 $3.16 $3.01 $3.03 $3.03 $3.03 $2.29 

1 500 

Snowblower 

Variable $0.33 $0.33 $0.33 $0.33 $2.69 $2.56 $2.58 $2.58 $2.58 $2.10 

Fixed $0.02 $0.02 $0.02 $0.02 $0.47 $0.45 $0.45 $0.45 $0.45 $0.19 

Total $0.35 $0.35 $0.35 $0.35 $3.16 $3.01 $3.03 $3.03 $3.03 $2.29 

2 250 Variable $0.00 $0.00 $0.00 $32.74 $32.74 $32.74 $32.74 $32.74 $27.06 $27.06 

Fixed $0.00 $0.00 $0.00 $3.63 $3.56 $3.50 $3.44 $3.39 $0.00 $0.00 

Total $0.00 $0.00 $0.00 $36.37 $36.30 $36.24 $36.18 $36.13 $27.06 $27.06 

2 500 Variable $0.00 $0.00 $0.00 $25.87 $25.87 $25.87 $25.87 $25.87 $21.63 $21.63 

Fixed $0.00 $0.00 $0.00 $6.13 $6.02 $5.92 $5.82 $5.73 $0.00 $0.00 

Total $0.00 $0.00 $0.00 $32.00 $31.89 $31.79 $31.69 $31.60 $21.63 $21.63 

2 1,000 Variable $0.00 $0.00 $0.00 $58.53 $58.53 $58.53 $58.53 $58.53 $45.00 $45.00 

Fixed $0.00 $0.00 $0.00 $16.00 $15.73 $15.46 $15.20 $14.96 $0.00 $0.00 

Total $0.00 $0.00 $0.00 $74.53 $73.99 $73.73 $73.73 $73.49 $45.00 $45.00 
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 

No equipment costs for HH; all costs are allocated to engine manufacturer Fixed 

Total 

Nonhandheld 

1 125 Variable 

Fixed No equipment costs for NHH Class I; all costs are allocated to engine manufacturer 

Total 

2 250 Variable $1.09 $1.09 $1.09 $6.44 $6.44 $6.31 $6.31 $6.31 $5.40 $5.40 

Fixed $0.04 $0.04 $0.04 $5.11 $5.05 $4.94 $4.87 $4.81 $0.68 $0.68 

Total $1.13 $1.13 $1.13 $11.55 $11.48 $11.24 $11.18 $11.12 $6.08 $6.08 

2 500 Variable $1.09 $1.09 $1.09 $6.44 $6.44 $6.31 $6.31 $6.31 $5.40 $5.40 

Fixed $0.04 $0.04 $0.04 $19.03 $18.73 $18.38 $18.10 $17.83 $0.68 $0.68 

Total $1.13 $1.13 $1.13 $25.47 $25.16 $24.69 $24.41 $24.13 $6.08 $6.08 

2 1000 Variable $1.09 $1.09 $1.09 $6.44 $6.44 $6.31 $6.31 $6.31 $5.40 $5.40 

Fixed $0.04 $0.04 $0.04 $16.93 $16.66 $16.35 $16.10 $15.86 $0.68 $0.68 

Total $1.13 $1.13 $1.13 $23.36 $23.10 $22.66 $22.41 $22.16 $6.08 $6.08 

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 2009 and decrease in 2014 when 

the fixed costs are fully amortized. 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 2014 and 

later years. The equipment costs are more complicated due to the phase in of the different 

standards. They begin in 2009, increase until about 2012, and then decrease in 2018. Equipment 

compliance costs remain the same for 2018 and later years. 

9-49 
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 20

PWC 50-100 Variable $870 $870 $870 $870 $870 $696 $696 $696 

Fixed $29 $29 $29 $29 $29 --- --- --- Total $899 $899 $899 $899 $899 $696 $696 $696 

PWC 100-175 Variable $85 $85 $85 $85 $85 $68 $68 $68 

Fixed $13 $13 $13 $13 $13 --- --- --- Total $98 $98 $98 $98 $98 $68 $68 $68 

PWC 175-300 Variable $1,290 $1,290 $1,290 $1,290 $1,290 $1,032 $1,032 $1,032 

Fixed $45 $45 $45 $45 $45 --- --- --- Total $1,335 $1,335 $1,335 $1,335 $1,335 $1,032 $1,032 $1,032 

SD/I Recreational 100-175 Variable $421 $421 $421 $421 $421 $337 $337 $337 

Fixed $19 $19 $19 $19 $19 --- --- --- Total $440 $440 $440 $440 $440 $337 $337 $337 

SD/I Recreational 175-300 Variable $292 $292 $292 $292 $292 $234 $234 $234 

Fixed $20 $20 $20 $20 $20 --- --- --- Total $312 $312 $312 $312 $312 $234 $234 $234 

SD/I Recreational 300 + Variable $349 $349 $349 $349 $349 $279 $279 $279 

Fixed $28 $28 $28 $28 $28 --- --- --- Total $377 $377 $377 $377 $377 $279 $279 $279 

SD/I Luxury 175-300 Variable $292 $292 $292 $292 $292 $234 $234 $234 

Fixed $20 $20 $20 $20 $20 --- --- --- Total $312 $312 $312 $312 $312 $234 $234 $234 

SD/I Luxury 300 + Variable $349 $349 $349 $349 $349 $279 $279 $279 

Fixed $28 $28 $28 $28 $28 --- --- --- Total $377 $377 $377 $377 $377 $279 $279 $279 

OB Recreational < 25 Variable $69 $69 $69 $69 $69 $55 $55 $55 
Application 

Category 

HP Category 

Cost Type 

2008 2009 2010 2011 2012 2013 2014 2015 2016 20

Fixed $5 $5 $5 $5 $5 --­ --­ --­ Total $74 $74 $74 $74 $74 $55 $55 $55 

OB Recreational 25-50 Variable $216 $216 $216 $216 $216 $173 $173 $173 

Fixed $6 $6 $6 $6 $6 --­ --­ --­ Total $222 $222 $222 $222 $222 $173 $173 $173 

OB Recreational 50-100 Variable $203 $203 $203 $203 $203 $162 $162 $162 

Fixed $8 $8 $8 $8 $8 --­ --­ --­ Total $211 $211 $211 $211 $211 $162 $162 $162 

OB Recreational 100-175 Variable $338 $338 $338 $338 $338 $270 $270 $270 

Fixed $15 $15 $15 $15 $15 -­­ -­­ -­­ Total $353 $353 $353 $353 $353 $270 $270 $270 

OB Recreational 175-300 Variable $690 $690 $690 $690 $690 $552 $552 $552 

Fixed $27 $27 $27 $27 $27 -­­ -­­ -­­ Total $717 $717 $717 $717 $717 $552 $552 $552 

OB Luxury 100-175 Variable $338 $338 $338 $338 $338 $270 $270 $270 

Fixed $15 $15 $15 $15 $15 -­­ -­­ -­­ Total $353 $353 $353 $353 $353 $270 $270 $270 

OB Luxury 175-300 Variable $690 $690 $690 $690 $690 $552 $552 $552 

Fixed $27 $27 $27 $27 $27 Total $717 $717 $717 $717 $717 $552 $552 $552 

OB Loose Engines < 25 Variable $69 $69 $69 $69 $69 $55 $55 $55 

Fixed $5 $5 $5 $5 $5 Total $74 $74 $74 $74 $74 $55 $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 20

PWC 50-100 Variable $1.6 $1.6 $3.8 $3.8 $3.8 $3.8 $3.8 $3.8 

Fixed $0.4 $0.4 $12.1 $12.1 $12.1 $12.1 $12.1 $12.1 Total $1.9 $1.9 $15.9 $15.9 $15.9 $15.9 $15.9 $15.9 

PWC 100-175 Variable $1.9 $1.9 $4.7 $4.7 $4.7 $4.7 $4.7 $4.7 

Fixed $0.4 $0.4 $13.3 $13.3 $13.3 $13.3 $13.3 $13.3 Total $2.3 $2.3 $18.0 $18.0 $18.0 $18.0 $18.0 $18.0 

PWC 175-300 Variable $1.9 $1.9 $4.7 $4.7 $4.7 $4.7 $4.7 $4.7 

Fixed $0.4 $0.4 $13.3 $13.3 $13.3 $13.3 $13.3 $13.3 Total $2.3 $2.3 $18.0 $18.0 $18.0 $18.0 $18.0 $18.0 

SD/I Recreational 

100-175 Variable $3.8 $31.4 $31.4 $67.2 $67.2 $67.2 $67.2 $61.7 

Fixed $0.5 $0.5 $0.5 $0.6 $0.6 $0.6 $0.6 $0.1 Total $4.4 $31.9 $31.9 $67.8 $67.8 $67.8 $67.8 $61.8 

SD/I Recreational 

175-300 Variable $4.5 $42.8 $42.8 $92.3 $92.3 $92.3 $92.3 $84.7 

Fixed $0.5 $0.5 $0.5 $0.6 $0.6 $0.6 $0.1 $0.1 Total $5.0 $43.3 $43.3 $93.0 $93.0 $93.0 $92.4 $84.8 

SD/I Recreational 

300 + 

Variable $5.2 $70.7 $70.7 $155.6 $155.6 $155.6 $155.6 $142.5 

Fixed $0.5 $0.5 $0.5 $0.6 $0.6 $0.6 $0.1 $0.1 Total $5.7 $71.2 $71.2 $156.3 $156.3 $156.3 $155.7 $142.6 

SD/I Luxury 

175-300 Variable $9.0 $85.5 $85.5 $184.7 $184.7 $184.7 $184.7 $169.4 

Fixed $0.5 $0.5 $0.5 $0.8 $0.8 $0.8 $0.2 $0.2 Total $9.6 $86.0 $86.0 $185.4 $185.4 $185.4 $184.9 $169.6 

SD/I Luxury 

300 + 

Variable $10.3 $141.4 $141.4 $311.2 $311.2 $311.2 $311.2 $285.0 

Fixed $0.5 $0.5 $0.5 $0.8 $0.8 $0.8 $0.2 $0.2 Total $10.9 $141.9 $141.9 $312.0 $312.0 $312.0 $311.5 $285.3 
Application 

Category 

HP Category Cost Type 2008 2009 2010 2011 2012 2013 2014 2015 2016 20

OB Recreational 

< 25 Variable $3.1 $4.4 $5.4 $5.4 $5.4 $5.4 $5.4 $5.1 

Fixed $0.2 $0.2 $6.7 $6.7 $6.7 $6.7 $6.7 $3.2 Total $3.3 $4.6 $12.0 $12.0 $12.0 $12.0 $12.0 $8.3 

OB Recreational 

25-50 Variable $4.4 $17.3 $17.3 $30.9 $30.9 $30.9 $30.9 $28.3 

Fixed $0.5 $0.5 $0.5 $0.6 $0.6 $0.6 $0.6 $0.1 Total $5.0 $17.8 $17.8 $31.6 $31.6 $31.6 $31.6 $28.5 

OB Recreational 

50-100 Variable $6.5 $26.7 $26.7 $47.7 $47.7 $47.7 $47.7 $43.6 

Fixed $0.5 $0.5 $0.5 $0.6 $0.6 $0.6 $0.6 $0.1 Total $7.0 $27.3 $27.3 $48.3 $48.3 $48.3 $48.3 $43.7 

OB Recreational 

100-175 Variable $7.7 $40.6 $40.6 $73.8 $73.8 $73.8 $73.8 $67.3 

Fixed $0.5 $0.5 $0.5 $0.6 $0.6 $0.6 $0.6 $0.1 Total $8.3 $41.1 $41.1 $74.5 $74.5 $74.5 $74.5 $67.4 

OB Recreational 

175-300 Variable $9.0 $57.9 $57.9 $107.0 $107.0 $107.0 $107.0 $97.2 

Fixed $0.5 $0.5 $0.5 $0.6 $0.6 $0.6 $0.6 $0.1 Total $9.6 $58.4 $85.4 $107.6 $107.6 $107.6 $107.6 $97.3 

OB Luxury 

100-175 Variable $15.5 $81.1 $81.1 $147.6 $147.6 $147.6 $147.6 $134.5 

Fixed $0.5 $0.5 $0.5 $0.8 $0.8 $0.8 $0.8 $0.2 Total $16.0 $81.6 $81.6 $148.4 $148.4 $148.4 $148.4 $134.7 

OB Luxury 

175-300 Variable $18.1 $115.8 $115.8 $213.9 $213.9 $213.9 $213.9 $14.4 

Fixed $0.5 $0.5 $0.5 $0.8 $0.8 $0.8 $0.8 $0.2 Total $18.6 $116.4 $116.4 $214.7 $214.7 $214.7 $214.7 $194.6 

OB Loose Engines 

< 25 Variable $3.0 $4.0 $5.0 $5.0 $5.0 $5.0 $5.0 $5.0 

Fixed $6.0 $0.0 $7.0 $7.0 $7.0 $7.0 $6.0 $6.0 Total $3.0 $5.0 $12.0 $12.0 $12.0 $12.0 $12.0 $12.0 
Draft Regulatory 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 proposed emission 

control program, reflecting the reduction in evaporative emissions and the use of more 

fuel-efficient engine technology to meet the proposed 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. 

9-54 
Economic Impact Analysis 

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 2009 until 2016 the estimated consumer savings associated with reduced gasoline 

consumption from the gas can controls increases sharply, from $16.7 million to $244 million. 

After 2016 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 $3 

million in 2009 to $43 million in 2016. 

9-55 
Draft Regulatory Impact Analysis
 

Table 13.3-20: Estimated Fuel Savings and Tax Revenue Impacts (2005$)
 

Year Small SI 

Gallons 

Marine SI 

Gallons 

Total Gallons Consumer 

Fuel Savings 

(Million$) 

Tax Revenue 

Impacts 

(Million$) 

Net Fuel 

Savings 

(Millions$) 

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 

2038 

1,710,034 

3,430,377 

5,447,927 

22,646,301 

38,820,204 

51,968,776 

60,526,996 

67,159,572 

72,453,313 

75,973,455 

78,721,263 

81,051,936 

83,107,200 

84,875,051 

86,484,675 

87,990,954 

89,466,431 

90,924,555 

92,374,877 

93,815,016 

95,245,161 

96,666,097 

98,077,275 

99,481,730 

100,883,561 

102,282,368 

103,678,793 

105,073,460 

106,463,214 

107,848,254 

109,231,748 

0 

4,143,348 

8,561,114 

13,117,609 

18,222,489 

23,304,500 

28,367,111 

33,371,341 

38,326,645 

43,218,105 

48,034,529 

52,441,003 

56,436,144 

60,288,468 

63,989,930 

67,173,629 

70,031,410 

72,627,522 

74,999,472 

77,157,506 

79,117,289 

80,838,412 

82,349,823 

83,737,102 

84,965,626 

86,094,905 

87,140,798 

88,101,996 

88,990,652 

89,818,189 

90,613,170 

1,710,034 

7,573,726 

14,009,041 

35,763,910 

57,042,693 

75,273,275 

88,894,107 

100,530,913 

110,779,958 

119,191,560 

126,755,792 

133,492,939 

139,543,344 

145,163,518 

150,474,605 

155,164,583 

159,497,841 

163,552,076 

167,374,349 

170,972,522 

174,362,449 

177,504,508 

180,427,098 

183,218,832 

185,849,187 

188,377,272 

190,819,590 

193,175,456 

195,453,866 

197,666,443 

199,844,918 

$3.8 

$16.7 

$30.9 

$78.8 

$125.7 

$165.9 

$195.9 

$221.5 

$244.1 

$262.6 

$279.3 

$294.2 

$307.5 

$319.9 

$331.6 

$341.9 

$351.5 

$360.4 

$368.8 

$376.7 

$384.2 

$391.1 

$397.6 

$403.7 

$409.5 

$415.1 

$420.5 

$425.7 

$430.7 

$435.6 

$440.4 

$0.7 

$3.0 

$5.5 

$13.9 

$22.2 

$29.3 

$34.7 

$39.2 

$43.2 

$46.5 

$49.4 

$52.0 

$54.4 

$56.6 

$58.7 

$60.5 

$62.2 

$63.8 

$65.2 

$66.6 

$68.0 

$69.2 

$70.3 

$71.4 

$72.4 

$73.4 

$74.4 

$75.3 

$76.2 

$77.1 

$77.9 

$3.1 

$13.7 

$25.4 

$64.9 

$103.5 

$136.5 

$161.2 

$182.3 

$200.9 

$216.2 

$229.9 

$242.1 

$253.1 

$263.3 

$272.9 

$281.4 

$289.3 

$296.6 

$303.6 

$310.1 

$316.3 

$321.9 

$327.3 

$332.3 

$337.1 

$341.7 

$346.1 

$350.4 

$354.5 

$358.5 

$362.5 

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 

9-56 
Economic Impact Analysis 

econometric practice. 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. 

The estimated supply and demand elasticities were based on best data we could find. For 

supply elasticities, we used the industry-level data published by the National Bureau of 

Economic Research (NBER)-Center for Economic Studies (Bartlesman, Becker, and Gray, 

2000). For demand elasticities, in addition to data from the NBER, we 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 It should be noted that the aggregate 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. 

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 proposed rule. 

The estimated supply elasticities for all of the equipment and engine markets are elastic, 

ranging from 2.3 for all recreational marine except PWC, to 3.3 for generators, 3.4 for PWCs and 

all Small SI applications except generators, and 3.8 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 3.3 percent change in quantity of generators produced). 

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. 

13All values are expressed in 1987$. Note the GDP deflators have been updated since the original 

estimation of supply elasticities for the Clean Air Nonroad Diesel rule. As a result, the elasticity estimation method 

is the same; however, the coefficients may vary slightly. 

9-57 
Draft Regulatory Impact Analysis 

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. 

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. 

9-58 
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 

3.8 EPA econometric 

estimate 

Cobb-Douglas 

production function 

Bartlesman et al 

(2000); 1958-1996; 

SIC 3519 

Marine Equipment Markets

 PWC 3.4 

All other vessel types 2.3 

EPA econometric 

estimate 

EPA econometric 

estimate 

Cobb-Douglas 

production function 

Cobb-Douglas 

production function 

Bartlesman et al 

(2000); 1958-1996; 

SIC 3799 

Bartlesman et al 

(2000); 1958-1996; 

SIC 3732 

Small SI Equipment Markets

 Gensets/welders 3.3 

 All other Small SI

 equipment (handheld

 and nonhandheld) 

3.4 

EPA econometric 

estimate 

EPA econometric 

estimate 

Cobb-Douglas 

production function 

Cobb-Douglas 

production function 

Bartlesman et al 

(2000); 1958-1996; 

SIC 3621 

Bartlesman et al 

(2000); 1958-1996; 

SIC 3524 

9-59 
Draft 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); 

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 

9-60 
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 

9-61 
Draft Regulatory Impact Analysis 

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 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. 

9-62 
Economic Impact Analysis 

9.4 Methods for Describing Uncertainty 

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 proposed 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 proposed 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 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 intends to investigate 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 will use the cross-sectional data 

model at either the firm-level or plant level from the U.S. Census Bureau to estimate these 

elasticities. We plan to use the results of this research provided the results are robust and that 

they are available in time for the analysis for the final rule. 

9-63 
Draft Regulatory Impact Analysis 

Table 9 .4-1 Primary Sources of Uncertainty in the Economic 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 proposed 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 

9-64 
Economic Impact Analysis 

Market shock In the EIM, the market is shocked by the full 

compliance costs, including variable and fixed 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 proposed standards 

would require manufacturers to devote new funds and 

resources to product redesign. A sensitivity analysis 

performed that excludes fixed costs in supply shift. 

Results may overstate 

distribution of social costs to 

some producers, understate 

market impacts; magnitude of 

impact is uncertain 

Sensitivity analysis performed 

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 

Sensitivity analysis performed 

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 

9-65 
Draft Regulatory Impact Analysis 

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), alternative methods to shock to the market equilibrium 

(using variable costs only) and alternative baseline equilibrium prices for lawnmowers 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 

2013 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 1.4 percent of burden of compliance 

costs from producers to consumers in Marine SI market; shift of 

about 2.0 percent of burden of compliance costs from producers to 

consumers in Small SI market) 

2013 Less Elastic 

(lower bound of 

95 percent 

confidence 

interval for each 

elasticity 

estimate) 

Negligible impact on expected price increase and quantity 

decrease (less than 0.1 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 1.3 percent of burden of compliance costs from 

consumers to producers in Marine SI market; shift of about 1.9 

percent of burden of compliance costs from consumers to 

producers in Small SI market) 

Price 

Elasticity of 

Demand 

2013 More Elastic 

(upper bound of 

95 percent 

confidence 

interval for each 

elasticity 

estimate) 

Negligible impact on expected price increase and quantity 

decrease (less than 1.0 percent additional increase in price 

increase compared to primary analysis; less than 1.5 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 10 percent of burden of compliance costs 

from consumers to producers in Small SI market) 

9-66 
Economic Impact Analysis 

2013 Less Elastic 

(lower bound of 

95 percent 

confidence 

interval for each 

elasticity 

estimate) 

Negligible impact on expected price increase and quantity 

decrease (less than 2.0 percent additional increase in price 

increase compared to primary analysis; less than 2.5 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 30.5 percent of burden of compliance 

costs from producers to consumers in Marine SI market; shift of 

about 14.5 percent of burden of compliance costs from producers 

to consumers in Small SI market) 

Market 

Supply Shift 

2013 Include only 

variable costs 

Smaller projected price increases and quantity decreases (less than 

1.5 percent additional increase in price compared to primary 

analysis; less than 1.0 percent additional increase in quantity 

decrease, compared to primary analysis) 

Engine and equipment manufacturers expected to bear larger share 

of total compliance costs (shift of about 3.1 percent of burden of 

compliance costs from consumers to producers in Marine SI 

market; shift of about 16.2 percent of burden of compliance costs 

from consumers to producers in Small SI market) 

Alternative 

Baseline 

Equilibrium 

Price -

Lawnmowers 

and Tractors 

2013 Lower baseline 

equilibrium price 

Larger percent increase in price and percent decrease in quantity, 

although absolute changes are smaller (about 2 percent additional 

price increase for both sectors compared to primary analysis; 

about 0.4 percent additional quantity decrease for lawn mowers 

and about 1.9 percent additional quantity decrease for tractors 

compared to primary analysis) 

Social welfare impacts unchanged. 

9-67 
Draft Regulatory Impact Analysis 

Chapter 9 References 

Air Improvement Resource, Inc. and National Economic Research Associates, Inc. (AIR/NERA). 2003. “CostEffectiveness Analyses of Alternative California Air Resources Board Tier 3 Non-Handheld Exhaust Emission 

Proposals.” Prepared for Engine Manufacturers Association and Outdoor Power Equipment Institute. Docket 

Identification EPA-HQ-OAR-2004-0008-0458 

Allen, R.G.D. 1938. Mathematical Analysis for Economists. New York: St. Martin’s Press. 

Baumol, William. "Contestable Markets: An Uprising in the theory of Industry Structure," 

American Economic Review, 72, March 1982:1-15. 

Baumol, William, John Panzer, and Robert Willig. 1982. Contestable Markets and the Theory of 

Industry Structure, San Diego, CA: Harcourt, Brace, Jovanovich. 

Berck, P., and S. Hoffmann. 2002. “Assessing the Employment Impacts.” Environmental and 

Resource Economics 22:133-156. 

Bingham, T.H., and T.J. Fox. 1999. “Model Complexity and Scope for Policy Analysis.” 

Public Administration Quarterly 23(3). 

Caffrey, C, and Cle Jackson, Zuimdie Guerra. September 2006. Memorandum to Docket EPA-HQ-OAR-2004-0008 

Re: Small SI Engine Sales and Price Estimates. A copy of this document is available in Docket EPA-HQ-OAR2004-0008. Docket Identification EPA-HQ-OAR-2004-0008-0491. 

Fullerton, D., and G. Metcalf. 2002. “Tax Incidence.” In A. Auerbach and M. Feldstein, eds., Handbook of Public 

Economics, Vol.4, Amsterdam: Elsevier. 

Harberger, Arnold C. 1974. Taxation and Welfare. Chicago: University of Chicago Press. 

Hicks, J.R., 1961. Marshall’s Third Rule: A Further Comment. Oxford Economic Papers 

13:262-65. Docket Identification EPA-HQ-OAR-2004-0008-0459 

Hicks, J.R., 1966. The Theory of Wages. 2nd Ed. New York: St. Martins Press, pp. 233-247. 

Docket Identification EPA-HQ-OAR-2004-0008-0460 

Kimbell, L.J., and G.W. Harrison. 1986. “On the Solution of General Equilibrium Models.” 

Economic Modeling 3:197-212. 

Li, Chi. March 16, 2007. Memorandum to Docket EPA-HQ-OAR-2004-0008 Detailed Results From Economic 

Impact Model. 

NBER-CES. National Bureau of Economic Research and U.S. Census Bureau, Center for 

Economic Research. 2002. NBER-CES Manufacturing Industry Database, 1958 - 1996. 

http://www.nber.org/nberces/nbprod96.htm 

Nicholson, W. 1998. Microeconomic Theory: Basic Principles and Extensions. Fort Worth: Dryden Press. 

Office Management and Budget (OMB). 1996. Executive Analysis of Federal Regulations 

Under Executive Order 12866. Executive Office of the President, Office Management and 

Budget. January 11, 1996. A copy of this document is available at 

http://www.whitehouse.gov/omb/inforeg/print/riaguide.html. 

9-68 
Economic Impact Analysis 

Outdoor Power Equipment & Engine Service Association. OPE-IN-THE-KNOW, Volume LXXIV, December 30, 

2004. “The Business of Outdoor Power Equipment”. Docket Identification 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 EPA-HQ-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-HQ-OAR-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), (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. 

U.S. Bureau of Labor Statistics. 2004b. Average Hourly Earnings of Production Workers (Boat Building: Series ID 

CEU3133661206; Farm Machinery and Equipment: Series ID EEU31352306). Obtained May 18, 2004. Docket 

Identification EPA-HQ-OAR-2004-0008-0474. 

U.S. Census Bureau. 1998 and selected other previous years. Current Industrial Reports. Motors and Generators. 

MA335H (MA36H prior to 1998). Washington, DC: U.S. Government Printing Office. Docket Identification EPAHQ-OAR-2004-0008-0475. 

U.S. Census Bureau. 2000 and selected other previous years. Current Industrial Reports. Farm 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. 

U.S. Census Bureau. 2005. Survey of Plant Capacity: 2004. Current Industrial Reports MQ-C1(04). Table 1. A 

copy of this document can be found at <http://www.census.gov/prod/2005pubs/mqc1-04.pdf>. Table 1a. 

U.S. Department of Energy, Energy Information Administration. 2006. “Petroleum Marketing Annual 2005.” A 

copy of this document can be found at 

http://www.eia.doe.gov/oil_gas/petroleum/data_publications/petroleum_marketing_annual/pma.html. Table 31. 

U.S. Environmental Protection Agency. 1999. OAQPS Economic Analysis Resource Document. 

9-69 
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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. 

U.S. Environmental Protection Agency. 2000. Guidelines for Preparing Economic Analyses. 

EPA-240-R-00-003, September 2000. 

U.S. Environmental Protection Agency. 2004. Final Regulatory Analysis: Control of Emissions from Nonroad 

Diesel Engines. EPA-420-R-04-007. Research Triangle Park, NC: EPA. 

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Economic Impact Analysis 

Appendix 9A: Impacts on Small SI Markets 

This appendix provides the time series of impacts from 2008 through 2038 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, 2007). 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 

• 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. 

9-71 
Draft Regulatory Impact Analysis 

Table 9A-1: Impact on Small SI Engine Market 

Class I (Average Price per Engine = $130)a 

Small SI Engine (Class I) 

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 $0 $0 0.3% 0.0% $0.0 –$0.2 

2009 $0 $0 0.3% 0.0% $3.6 –$0.2 

2010 $0 $0 0.3% 0.0% $3.7 –$0.2 

2011 $0 $0 0.3% 0.0% $3.7 –$0.2 

2012 $15 $14 10.9% –2.0% $161.9 –$7.3 

2013 $15 $14 10.7% –2.0% $162.8 –$7.4 

2014 $15 $14 10.7% –2.0% $165.4 –$7.5 

2015 $15 $14 10.7% –2.0% $167.8 –$7.6 

2016 $15 $14 10.7% –2.0% $170.2 –$7.7 

2017 $12 $11 8.6% –1.6% $139.0 –$6.3 

2018 $12 $11 8.6% –1.6% $141.2 –$6.4 

2019 $12 $11 8.6% –1.6% $143.4 –$6.5 

2020 $12 $11 8.6% –1.6% $145.6 –$6.6 

2021 $12 $11 8.6% –1.6% $147.7 –$6.7 

2022 $12 $11 8.6% –1.6% $149.9 –$6.8 

2023 $12 $11 8.6% –1.6% $152.1 –$6.9 

2024 $12 $11 8.6% –1.6% $154.3 –$7.0 

2025 $12 $11 8.6% –1.6% $156.5 –$7.1 

2026 $12 $11 8.6% –1.6% $158.7 –$7.2 

2027 $12 $11 8.6% –1.6% $160.9 –$7.3 

2028 $12 $11 8.6% –1.6% $163.1 –$7.4 

2029 $12 $11 8.6% –1.6% $165.3 –$7.5 

2030 $12 $11 8.6% –1.6% $167.5 –$7.6 

2031 $12 $11 8.6% –1.6% $169.7 –$7.7 

2032 $12 $11 8.6% –1.6% $171.9 –$7.8 

2033 $12 $11 8.6% –1.6% $174.1 –$7.9 

2034 $12 $11 8.6% –1.6% $176.3 –$7.9 

2035 $12 $11 8.6% –1.6% $178.5 –$8.1 

2036 $12 $11 8.6% –1.6% $180.7 –$8.2 

2037 $12 $11 8.6% –1.6% $182.9 –$8.3 

2038 $12 $11 8.6% –1.6% $185.2 –$8.4 

NPV (3%) $2,630.8 –$119.5 

NPV (7%) $1,466.2 –$66.7 

a Figures are in 2005 dollars. 

9-72 
Economic Impact Analysis 

Table 9A-2. Impact on Small SI Engine Market 

Class II (Average Price per Engine = $290)a 

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 $0 $0 0.0% –0.1% $0.0 –$0.2 

2009 $0 $0 0.0% –0.1% $0.0 –$0.2 

2010 $0 $0 0.0% –0.1% $0.0 –$0.2 

2011 $42 $40 14.0% –3.1% $202.2 –$10.8 

2012 $42 $40 13.9% –3.1% $205.2 –$10.9 

2013 $42 $40 13.9% –3.1% $208.3 –$11.0 

2014 $42 $40 13.9% –3.0% $211.3 –$11.2 

2015 $42 $40 13.8% –3.0% $214.3 –$11.3 

2016 $29 $28 10.1% –2.0% $152.7 –$7.3 

2017 $29 $28 10.1% –2.0% $155.1 –$7.4 

2018 $29 $28 10.1% –2.0% $157.6 –$7.5 

2019 $29 $28 10.1% –2.0% $160.1 –$7.6 

2020 $29 $28 10.1% –2.0% $162.5 –$7.8 

2021 $29 $28 10.1% –2.0% $165.0 –$7.9 

2022 $29 $28 10.1% –2.0% $167.4 –$8.0 

2023 $29 $28 10.1% –2.0% $169.9 –$8.1 

2024 $29 $28 10.1% –2.0% $172.4 –$8.2 

2025 $29 $28 10.1% –2.0% $174.8 –$8.3 

2026 $29 $28 10.1% –2.0% $177.3 –$8.5 

2027 $29 $28 10.1% –2.0% $179.8 –$8.6 

2028 $29 $28 10.1% –2.0% $182.3 –$8.7 

2029 $29 $28 10.1% –2.0% $184.7 –$8.8 

2030 $29 $28 10.1% –2.0% $187.2 –$8.9 

2031 $29 $28 10.1% –2.0% $189.7 –$9.1 

2032 $29 $28 10.1% –2.0% $192.2 –$9.2 

2033 $29 $28 10.1% –2.0% $194.7 –$9.3 

2034 $29 $28 10.1% –2.0% $197.1 –$9.4 

2035 $29 $28 10.1% –2.0% $199.6 –$9.5 

2036 $29 $28 10.1% –2.0% $202.1 –$9.7 

2037 $29 $28 10.1% –2.0% $204.6 –$9.8 

2038 $29 $28 10.1% –2.0% $207.0 –$9.9 

NPV (3%) $3,164.8 –$156.3 

NPV (7%) $1,828.9 –$91.5 

a Figures are in 2005 dollars. 

9-73 
Draft Regulatory Impact Analysis 

Table 9A-3: Impact on Small SI Equipment Market 

Handheld (Average Price per Equipment = $87)a,b 

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 0.0% 0.0% $0.0 $0.0 

2009 $0 $0 0.0% 0.0% $0.0 $0.0 

2010 $1 $1 0.6% –1.1% $7.3 –$2.6 

2011 $1 $1 0.6% –1.1% $7.4 –$2.6 

2012 $1 $1 0.6% –1.1% $7.5 –$2.7 

2013 $1 $1 0.6% –1.1% $7.7 –$2.7 

2014 $1 $1 0.6% –1.1% $7.8 –$2.8 

2015 $1 $0 0.5% –1.0% $6.7 –$2.4 

2016 $1 $0 0.5% –1.0% $6.8 –$2.4 

2017 $1 $0 0.5% –1.0% $6.9 –$2.5 

2018 $1 $0 0.5% –1.0% $7.0 –$2.5 

2019 $1 $0 0.5% –1.0% $7.1 –$2.6 

2020 $1 $0 0.5% –1.0% $7.2 –$2.6 

2021 $1 $0 0.5% –1.0% $7.4 –$2.6 

2022 $1 $0 0.5% –1.0% $7.5 –$2.7 

2023 $1 $0 0.5% –1.0% $7.6 –$2.7 

2024 $1 $0 0.5% –1.0% $7.7 –$2.7 

2025 $1 $0 0.5% –1.0% $7.8 –$2.8 

2026 $1 $0 0.5% –1.0% $7.9 –$2.8 

2027 $1 $0 0.5% –1.0% $8.0 –$2.9 

2028 $1 $0 0.5% –1.0% $8.1 –$2.9 

2029 $1 $0 0.5% –1.0% $8.2 –$2.9 

2030 $1 $0 0.5% –1.0% $8.3 –$3.0 

2031 $1 $0 0.5% –1.0% $8.4 –$3.0 

2032 $1 $0 0.5% –1.0% $8.5 –$3.1 

2033 $1 $0 0.5% –1.0% $8.7 –$3.1 

2034 $1 $0 0.5% –1.0% $8.8 –$3.1 

2035 $1 $0 0.5% –1.0% $8.9 –$3.2 

2036 $1 $0 0.5% –1.0% $9.0 –$3.2 

2037 $1 $0 0.5% –1.0% $9.1 –$3.2 

2038 $1 $0 0.5% –1.0% $9.2 –$3.3 

NPV (3%) $139.9 –$49.9 

NPV (7%) $81.3 –$29.0 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-74 
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,b 

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 $0 0.0% 0.0% $0.0 $0.0 

2009 $0 $0 0.0% 0.0% $0.0 $0.0 

2010 $0 $0 0.0% 0.0% $0.0 $0.0 

2011 $0 $0 0.0% 0.0% $0.0 $0.0 

2012 $0 $12 1.1% –1.1% $0.0 –$0.3 

2013 $0 $12 1.1% –1.1% $0.0 –$0.3 

2014 $0 $12 1.1% –1.1% $0.0 –$0.3 

2015 $0 $12 1.1% –1.1% $0.0 –$0.3 

2016 $0 $12 1.1% –1.1% $0.0 –$0.3 

2017 $0 $9 0.8% –0.8% $0.0 –$0.2 

2018 $0 $9 0.8% –0.8% $0.0 –$0.3 

2019 $0 $9 0.8% –0.8% $0.0 –$0.3 

2020 $0 $9 0.8% –0.8% $0.0 –$0.3 

2021 $0 $9 0.8% –0.8% $0.0 –$0.3 

2022 $0 $9 0.8% –0.8% $0.0 –$0.3 

2023 $0 $9 0.8% –0.8% $0.0 –$0.3 

2024 $0 $9 0.8% –0.8% $0.0 –$0.3 

2025 $0 $9 0.8% –0.8% $0.0 –$0.3 

2026 $0 $9 0.8% –0.8% $0.0 –$0.3 

2027 $0 $9 0.8% –0.8% $0.0 –$0.3 

2028 $0 $9 0.8% –0.8% $0.0 –$0.3 

2029 $0 $9 0.8% –0.8% $0.0 –$0.3 

2030 $0 $9 0.8% –0.8% $0.0 –$0.3 

2031 $0 $9 0.8% –0.8% $0.0 –$0.3 

2032 $0 $9 0.8% –0.8% $0.0 –$0.3 

2033 $0 $9 0.8% –0.8% $0.0 –$0.3 

2034 $0 $9 0.8% –0.8% $0.0 –$0.3 

2035 $0 $9 0.8% –0.8% $0.0 –$0.3 

2036 $0 $9 0.8% –0.8% $0.0 –$0.3 

2037 $0 $9 0.8% –0.8% $0.0 –$0.3 

2038 $0 $9 0.8% –0.8% $0.0 –$0.3 

NPV (3%) $0.0 –$4.8 

NPV (7%) $0.0 –$2.7 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-75 
Draft 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,b
 

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 $0 0.0% 0.0% $0.0 $0.0 

2009 $0 $0 0.0% 0.0% $0.0 $0.0 

2010 $0 $0 0.0% 0.0% $0.0 $0.0 

2011 $0 $0 0.0% 0.0% $0.0 $0.0 

2012 $0 $12 2.1% –2.1% $0.0 –$0.3 

2013 $0 $12 2.0% –2.0% $0.0 –$0.3 

2014 $0 $12 2.0% –2.0% $0.0 –$0.3 

2015 $0 $12 2.0% –2.0% $0.0 –$0.3 

2016 $0 $12 2.0% –2.0% $0.0 –$0.3 

2017 $0 $9 1.6% –1.6% $0.0 –$0.3 

2018 $0 $9 1.6% –1.6% $0.0 –$0.3 

2019 $0 $9 1.6% –1.6% $0.0 –$0.3 

2020 $0 $9 1.6% –1.6% $0.0 –$0.3 

2021 $0 $9 1.6% –1.6% $0.0 –$0.3 

2022 $0 $9 1.6% –1.6% $0.0 –$0.3 

2023 $0 $9 1.6% –1.6% $0.0 –$0.3 

2024 $0 $9 1.6% –1.6% $0.0 –$0.3 

2025 $0 $9 1.6% –1.6% $0.0 –$0.3 

2026 $0 $9 1.6% –1.6% $0.0 –$0.3 

2027 $0 $9 1.6% –1.6% $0.0 –$0.3 

2028 $0 $9 1.6% –1.6% $0.0 –$0.3 

2029 $0 $9 1.6% –1.6% $0.0 –$0.3 

2030 $0 $9 1.6% –1.6% $0.0 –$0.3 

2031 $0 $9 1.6% –1.6% $0.0 –$0.3 

2032 $0 $9 1.6% –1.6% $0.0 –$0.3 

2033 $0 $9 1.6% –1.6% $0.0 –$0.3 

2034 $0 $9 1.6% –1.6% $0.0 –$0.4 

2035 $0 $9 1.6% –1.6% $0.0 –$0.4 

2036 $0 $9 1.6% –1.6% $0.0 –$0.4 

2037 $0 $9 1.6% –1.6% $0.0 –$0.4 

2038 $0 $9 1.6% –1.6% $0.0 –$0.4 

NPV (3%) $0.0 –$5.1 

NPV (7%) $0.0 –$2.8 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-76 
Economic Impact Analysis 

Table 9A-6: Impact on Small SI Equipment Market: Class I Lawn Mowers UL 125 (Average 

Price per Equipment = $218)a,b 

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 $0 0.1% 0.0% $0.0 –$0.1 

2009 $0 $0 0.1% 0.0% $0.0 –$0.1 

2010 $0 $0 0.1% 0.0% $0.0 –$0.1 

2011 $0 $0 0.1% 0.0% $0.0 –$0.1 

2012 $0 $14 6.6% –1.3% $0.0 –$5.4 

2013 $0 $14 6.6% –1.2% $0.0 –$5.4 

2014 $0 $14 6.6% –1.2% $0.0 –$5.5 

2015 $0 $14 6.6% –1.2% $0.0 –$5.6 

2016 $0 $14 6.5% –1.2% $0.0 –$5.7 

2017 $0 $11 5.2% –1.0% $0.0 –$4.6 

2018 $0 $11 5.2% –1.0% $0.0 –$4.7 

2019 $0 $11 5.2% –1.0% $0.0 –$4.8 

2020 $0 $11 5.2% –1.0% $0.0 –$4.8 

2021 $0 $11 5.2% –1.0% $0.0 –$4.9 

2022 $0 $11 5.2% –1.0% $0.0 –$5.0 

2023 $0 $11 5.2% –1.0% $0.0 –$5.1 

2024 $0 $11 5.2% –1.0% $0.0 –$5.1 

2025 $0 $11 5.2% –1.0% $0.0 –$5.2 

2026 $0 $11 5.2% –1.0% $0.0 –$5.3 

2027 $0 $11 5.2% –1.0% $0.0 –$5.4 

2028 $0 $11 5.2% –1.0% $0.0 –$5.4 

2029 $0 $11 5.2% –1.0% $0.0 –$5.5 

2030 $0 $11 5.2% –1.0% $0.0 –$5.6 

2031 $0 $11 5.2% –1.0% $0.0 –$5.6 

2032 $0 $11 5.2% –1.0% $0.0 –$5.7 

2033 $0 $11 5.2% –1.0% $0.0 –$5.8 

2034 $0 $11 5.2% –1.0% $0.0 –$5.9 

2035 $0 $11 5.2% –1.0% $0.0 –$5.9 

2036 $0 $11 5.2% –1.0% $0.0 –$6.0 

2037 $0 $11 5.2% –1.0% $0.0 –$6.1 

2038 $0 $11 5.2% –1.0% $0.0 –$6.2 

NPV (3%) $0.0 –$87.6 

NPV (7%) $0.0 –$48.8 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-77 
Draft 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,b 

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 $0 0.1% –0.1% $0.0 –$0.1 

2009 $0 $0 0.1% –0.1% $0.0 –$0.1 

2010 $0 $0 0.1% –0.1% $0.0 –$0.1 

2011 $0 $0 0.1% –0.1% $0.0 –$0.1 

2012 $0 $12 4.9% –4.4% $0.0 –$2.3 

2013 $0 $12 4.9% –4.4% $0.0 –$2.3 

2014 $0 $12 4.9% –4.4% $0.0 –$2.4 

2015 $0 $12 4.9% –4.4% $0.0 –$2.4 

2016 $0 $12 4.9% –4.4% $0.0 –$2.4 

2017 $0 $10 3.9% –3.5% $0.0 –$2.0 

2018 $0 $10 3.9% –3.5% $0.0 –$2.0 

2019 $0 $10 3.9% –3.5% $0.0 –$2.0 

2020 $0 $10 3.9% –3.5% $0.0 –$2.1 

2021 $0 $10 3.9% –3.5% $0.0 –$2.1 

2022 $0 $10 3.9% –3.5% $0.0 –$2.1 

2023 $0 $10 3.9% –3.5% $0.0 –$2.2 

2024 $0 $10 3.9% –3.5% $0.0 –$2.2 

2025 $0 $10 3.9% –3.5% $0.0 –$2.2 

2026 $0 $10 3.9% –3.5% $0.0 –$2.3 

2027 $0 $10 3.9% –3.5% $0.0 –$2.3 

2028 $0 $10 3.9% –3.5% $0.0 –$2.3 

2029 $0 $10 3.9% –3.5% $0.0 –$2.4 

2030 $0 $10 3.9% –3.5% $0.0 –$2.4 

2031 $0 $10 3.9% –3.5% $0.0 –$2.4 

2032 $0 $10 3.9% –3.5% $0.0 –$2.5 

2033 $0 $10 3.9% –3.5% $0.0 –$2.5 

2034 $0 $10 3.9% –3.5% $0.0 –$2.5 

2035 $0 $10 3.9% –3.5% $0.0 –$2.5 

2036 $0 $10 3.9% –3.5% $0.0 –$2.6 

2037 $0 $10 3.9% –3.5% $0.0 –$2.6 

2038 $0 $10 3.9% –3.5% $0.0 –$2.6 

NPV (3%) $0.0 –$37.7 

NPV (7%) $0.0 –$21.1 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-78 
Economic Impact Analysis 

Table 9A-8: Impact on Small SI Equipment Market: Class I Gensets/Welders UL 125 (Average 

Price per Equipment = $999)a,b 

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 $0 0.0% 0.0% $0.0 $0.0 

2009 $0 $0 0.0% 0.0% $0.0 $0.0 

2010 $0 $0 0.0% 0.0% $0.0 $0.0 

2011 $0 $0 0.0% 0.0% $0.0 $0.0 

2012 $0 $11 1.1% –1.5% $0.0 –$1.4 

2013 $0 $11 1.1% –1.5% $0.0 –$1.4 

2014 $0 $11 1.1% –1.5% $0.0 –$1.4 

2015 $0 $11 1.1% –1.5% $0.0 –$1.4 

2016 $0 $11 1.1% –1.5% $0.0 –$1.4 

2017 $0 $9 0.9% –1.2% $0.0 –$1.2 

2018 $0 $9 0.9% –1.2% $0.0 –$1.2 

2019 $0 $9 0.9% –1.2% $0.0 –$1.2 

2020 $0 $9 0.9% –1.2% $0.0 –$1.2 

2021 $0 $9 0.9% –1.2% $0.0 –$1.2 

2022 $0 $9 0.9% –1.2% $0.0 –$1.3 

2023 $0 $9 0.9% –1.2% $0.0 –$1.3 

2024 $0 $9 0.9% –1.2% $0.0 –$1.3 

2025 $0 $9 0.9% –1.2% $0.0 –$1.3 

2026 $0 $9 0.9% –1.2% $0.0 –$1.3 

2027 $0 $9 0.9% –1.2% $0.0 –$1.4 

2028 $0 $9 0.9% –1.2% $0.0 –$1.4 

2029 $0 $9 0.9% –1.2% $0.0 –$1.4 

2030 $0 $9 0.9% –1.2% $0.0 –$1.4 

2031 $0 $9 0.9% –1.2% $0.0 –$1.4 

2032 $0 $9 0.9% –1.2% $0.0 –$1.5 

2033 $0 $9 0.9% –1.2% $0.0 –$1.5 

2034 $0 $9 0.9% –1.2% $0.0 –$1.5 

2035 $0 $9 0.9% –1.2% $0.0 –$1.5 

2036 $0 $9 0.9% –1.2% $0.0 –$1.5 

2037 $0 $9 0.9% –1.2% $0.0 –$1.5 

2038 $0 $9 0.9% –1.2% $0.0 –$1.6 

NPV (3%) $0.0 –$22.1 

NPV (7%) $0.0 –$12.3 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-79 
Draft 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,b 

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 $0 0.3% –0.3% $0.0 –$0.1 

2009 $0 $0 0.3% –0.3% $0.0 –$0.1 

2010 $0 $0 0.3% –0.3% $0.0 –$0.1 

2011 $0 $0 0.3% –0.3% $0.0 –$0.1 

2012 $0 $12 12.3% –12.3% $0.0 –$2.2 

2013 $0 $12 12.2% –12.2% $0.0 –$2.2 

2014 $0 $12 12.2% –12.2% $0.0 –$2.2 

2015 $0 $12 12.1% –12.1% $0.0 –$2.2 

2016 $0 $12 12.1% –12.1% $0.0 –$2.3 

2017 $0 $9 9.7% –9.7% $0.0 –$1.9 

2018 $0 $9 9.7% –9.7% $0.0 –$1.9 

2019 $0 $9 9.7% –9.7% $0.0 –$1.9 

2020 $0 $9 9.7% –9.7% $0.0 –$2.0 

2021 $0 $9 9.7% –9.7% $0.0 –$2.0 

2022 $0 $9 9.7% –9.7% $0.0 –$2.0 

2023 $0 $9 9.7% –9.7% $0.0 –$2.0 

2024 $0 $9 9.7% –9.7% $0.0 –$2.1 

2025 $0 $9 9.7% –9.7% $0.0 –$2.1 

2026 $0 $9 9.7% –9.7% $0.0 –$2.1 

2027 $0 $9 9.7% –9.7% $0.0 –$2.2 

2028 $0 $9 9.7% –9.7% $0.0 –$2.2 

2029 $0 $9 9.7% –9.7% $0.0 –$2.2 

2030 $0 $9 9.7% –9.7% $0.0 –$2.3 

2031 $0 $9 9.7% –9.7% $0.0 –$2.3 

2032 $0 $9 9.7% –9.7% $0.0 –$2.3 

2033 $0 $9 9.7% –9.7% $0.0 –$2.3 

2034 $0 $9 9.7% –9.7% $0.0 –$2.4 

2035 $0 $9 9.7% –9.7% $0.0 –$2.4 

2036 $0 $9 9.7% –9.7% $0.0 –$2.4 

2037 $0 $9 9.7% –9.7% $0.0 –$2.5 

2038 $0 $9 9.7% –9.7% $0.0 –$2.5 

NPV (3%) $0.0 –$35.6 

NPV (7%) $0.0 –$19.9 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-80 
Economic Impact Analysis 

Table 9A-10: Impact on Small SI Equipment Market: Class I Snowblowers UL 125 (Average 

Price per Equipment = $324)a,b 

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 $0 0.1% –0.1% $0.0 –$0.1 

2011 $0 $0 0.1% –0.1% $0.0 –$0.1 

2012 $0 $2 0.7% –0.7% $0.0 –$0.4 

2013 $0 $2 0.7% –0.7% $0.0 –$0.4 

2014 $0 $2 0.7% –0.7% $0.0 –$0.4 

2015 $0 $2 0.7% –0.7% $0.0 –$0.4 

2016 $0 $2 0.7% –0.7% $0.0 –$0.4 

2017 $0 $2 0.5% –0.5% $0.0 –$0.3 

2018 $0 $2 0.5% –0.5% $0.0 –$0.3 

2019 $0 $2 0.5% –0.5% $0.0 –$0.3 

2020 $0 $2 0.5% –0.5% $0.0 –$0.3 

2021 $0 $2 0.5% –0.5% $0.0 –$0.4 

2022 $0 $2 0.5% –0.5% $0.0 –$0.4 

2023 $0 $2 0.5% –0.5% $0.0 –$0.4 

2024 $0 $2 0.5% –0.5% $0.0 –$0.4 

2025 $0 $2 0.5% –0.5% $0.0 –$0.4 

2026 $0 $2 0.5% –0.5% $0.0 –$0.4 

2027 $0 $2 0.5% –0.5% $0.0 –$0.4 

2028 $0 $2 0.5% –0.5% $0.0 –$0.4 

2029 $0 $2 0.5% –0.5% $0.0 –$0.4 

2030 $0 $2 0.5% –0.5% $0.0 –$0.4 

2031 $0 $2 0.5% –0.5% $0.0 –$0.4 

2032 $0 $2 0.5% –0.5% $0.0 –$0.4 

2033 $0 $2 0.5% –0.5% $0.0 –$0.4 

2034 $0 $2 0.5% –0.5% $0.0 –$0.4 

2035 $0 $2 0.5% –0.5% $0.0 –$0.4 

2036 $0 $2 0.5% –0.5% $0.0 –$0.4 

2037 $0 $2 0.5% –0.5% $0.0 –$0.4 

2038 $0 $2 0.5% –0.5% $0.0 –$0.4 

NPV (3%) $0.0 –$6.4 

NPV (7%) $0.0 –$3.6 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-81 
Draft 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,b
 

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 $0 $1 0.0% 0.0% $0.0 $0.0 

2009 $1 $1 0.0% 0.0% $0.1 $0.0 

2010 $1 $1 0.0% 0.0% $0.1 $0.0 

2011 $12 $35 1.9% –1.9% $0.9 –$0.8 

2012 $11 $35 1.9% –1.9% $0.9 –$0.8 

2013 $11 $35 1.9% –1.9% $0.9 –$0.9 

2014 $11 $35 1.9% –1.9% $0.9 –$0.9 

2015 $11 $35 1.9% –1.9% $0.9 –$0.9 

2016 $6 $25 1.3% –1.3% $0.5 –$0.6 

2017 $6 $25 1.3% –1.3% $0.5 –$0.6 

2018 $6 $25 1.3% –1.3% $0.5 –$0.6 

2019 $6 $25 1.3% –1.3% $0.6 –$0.7 

2020 $6 $25 1.3% –1.3% $0.6 –$0.7 

2021 $6 $25 1.3% –1.3% $0.6 –$0.7 

2022 $6 $25 1.3% –1.3% $0.6 –$0.7 

2023 $6 $25 1.3% –1.3% $0.6 –$0.7 

2024 $6 $25 1.3% –1.3% $0.6 –$0.7 

2025 $6 $25 1.3% –1.3% $0.6 –$0.7 

2026 $6 $25 1.3% –1.3% $0.6 –$0.7 

2027 $6 $25 1.3% –1.3% $0.6 –$0.7 

2028 $6 $25 1.3% –1.3% $0.6 –$0.7 

2029 $6 $25 1.3% –1.3% $0.6 –$0.8 

2030 $6 $25 1.3% –1.3% $0.6 –$0.8 

2031 $6 $25 1.3% –1.3% $0.7 –$0.8 

2032 $6 $25 1.3% –1.3% $0.7 –$0.8 

2033 $6 $25 1.3% –1.3% $0.7 –$0.8 

2034 $6 $25 1.3% –1.3% $0.7 –$0.8 

2035 $6 $25 1.3% –1.3% $0.7 –$0.8 

2036 $6 $25 1.3% –1.3% $0.7 –$0.8 

2037 $6 $25 1.3% –1.3% $0.7 –$0.8 

2038 $6 $25 1.3% –1.3% $0.7 –$0.8 

NPV (3%) $11.9 –$12.9 

NPV (7%) $7.1 –$7.6 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-82 
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,b 

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 $0 $1 0.0% 0.0% $0.0 –$0.1 

2009 $1 $1 0.0% 0.0% $0.2 –$0.1 

2010 $1 $1 0.0% 0.0% $0.2 –$0.1 

2011 $12 $35 1.2% –1.2% $2.2 –$2.0 

2012 $11 $35 1.2% –1.2% $2.3 –$2.0 

2013 $11 $35 1.2% –1.2% $2.3 –$2.1 

2014 $11 $35 1.2% –1.2% $2.3 –$2.1 

2015 $11 $35 1.2% –1.2% $2.3 –$2.1 

2016 $6 $25 0.8% –0.8% $1.3 –$1.5 

2017 $6 $25 0.8% –0.8% $1.3 –$1.5 

2018 $6 $25 0.8% –0.8% $1.3 –$1.6 

2019 $6 $25 0.8% –0.8% $1.3 –$1.6 

2020 $6 $25 0.8% –0.8% $1.4 –$1.6 

2021 $6 $25 0.8% –0.8% $1.4 –$1.6 

2022 $6 $25 0.8% –0.8% $1.4 –$1.7 

2023 $6 $25 0.8% –0.8% $1.4 –$1.7 

2024 $6 $25 0.8% –0.8% $1.5 –$1.7 

2025 $6 $25 0.8% –0.8% $1.5 –$1.7 

2026 $6 $25 0.8% –0.8% $1.5 –$1.8 

2027 $6 $25 0.8% –0.8% $1.5 –$1.8 

2028 $6 $25 0.8% –0.8% $1.5 –$1.8 

2029 $6 $25 0.8% –0.8% $1.6 –$1.8 

2030 $6 $25 0.8% –0.8% $1.6 –$1.9 

2031 $6 $25 0.8% –0.8% $1.6 –$1.9 

2032 $6 $25 0.8% –0.8% $1.6 –$1.9 

2033 $6 $25 0.8% –0.8% $1.6 –$1.9 

2034 $6 $25 0.8% –0.8% $1.7 –$2.0 

2035 $6 $25 0.8% –0.8% $1.7 –$2.0 

2036 $6 $25 0.8% –0.8% $1.7 –$2.0 

2037 $6 $25 0.8% –0.8% $1.7 –$2.0 

2038 $6 $25 0.8% –0.8% $1.7 –$2.1 

NPV (3%) $29.2 –$31.7 

NPV (7%) $17.5 –$18.4 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-83 
Draft Regulatory Impact Analysis 

Table 9A-13: Impact on Small SI Equipment Market: Class II Tractors UL 250 (Average Price 

per Equipment = $1,937)a,b 

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 $0 $1 0.0% 0.0% $0.0 –$0.4 

2009 $1 $1 0.0% 0.0% $2.1 –$0.5 

2010 $1 $1 0.0% 0.0% $2.1 –$0.5 

2011 $12 $35 1.8% –1.8% $22.0 –$19.7 

2012 $11 $35 1.8% –1.8% $22.2 –$19.9 

2013 $11 $35 1.8% –1.8% $22.1 –$20.2 

2014 $11 $35 1.8% –1.8% $22.4 –$20.5 

2015 $11 $35 1.8% –1.8% $22.6 –$20.7 

2016 $6 $25 1.3% –1.3% $12.6 –$14.8 

2017 $6 $25 1.3% –1.3% $12.8 –$15.1 

2018 $6 $25 1.3% –1.3% $13.0 –$15.3 

2019 $6 $25 1.3% –1.3% $13.2 –$15.5 

2020 $6 $25 1.3% –1.3% $13.4 –$15.8 

2021 $6 $25 1.3% –1.3% $13.6 –$16.0 

2022 $6 $25 1.3% –1.3% $13.8 –$16.3 

2023 $6 $25 1.3% –1.3% $14.0 –$16.5 

2024 $6 $25 1.3% –1.3% $14.2 –$16.7 

2025 $6 $25 1.3% –1.3% $14.4 –$17.0 

2026 $6 $25 1.3% –1.3% $14.6 –$17.2 

2027 $6 $25 1.3% –1.3% $14.8 –$17.5 

2028 $6 $25 1.3% –1.3% $15.0 –$17.7 

2029 $6 $25 1.3% –1.3% $15.2 –$17.9 

2030 $6 $25 1.3% –1.3% $15.4 –$18.2 

2031 $6 $25 1.3% –1.3% $15.6 –$18.4 

2032 $6 $25 1.3% –1.3% $15.8 –$18.7 

2033 $6 $25 1.3% –1.3% $16.0 –$18.9 

2034 $6 $25 1.3% –1.3% $16.2 –$19.1 

2035 $6 $25 1.3% –1.3% $16.4 –$19.4 

2036 $6 $25 1.3% –1.3% $16.6 –$19.6 

2037 $6 $25 1.3% –1.3% $16.8 –$19.9 

2038 $6 $25 1.3% –1.3% $17.0 –$20.1 

NPV (3%) $285.9 –$308.5 

NPV (7%) $171.3 –$178.8 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-84 
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,b 

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 $0 $1 0.3% –0.2% $0.0 $0.0 

2009 $1 $1 0.3% –0.2% $0.2 $0.0 

2010 $1 $1 0.3% –0.2% $0.2 $0.0 

2011 $12 $36 11.6% –10.5% $1.7 –$1.3 

2012 $11 $36 11.6% –10.4% $1.7 –$1.3 

2013 $11 $36 11.5% –10.4% $1.7 –$1.3 

2014 $11 $36 11.5% –10.3% $1.7 –$1.4 

2015 $11 $36 11.5% –10.3% $1.7 –$1.4 

2016 $6 $25 8.0% –7.2% $0.9 –$1.0 

2017 $6 $25 8.0% –7.2% $1.0 –$1.0 

2018 $6 $25 8.0% –7.2% $1.0 –$1.0 

2019 $6 $25 8.0% –7.2% $1.0 –$1.0 

2020 $6 $25 8.0% –7.2% $1.0 –$1.1 

2021 $6 $25 8.0% –7.2% $1.0 –$1.1 

2022 $6 $25 8.0% –7.2% $1.0 –$1.1 

2023 $6 $25 8.0% –7.2% $1.1 –$1.1 

2024 $6 $25 8.0% –7.2% $1.1 –$1.1 

2025 $6 $25 8.0% –7.2% $1.1 –$1.1 

2026 $6 $25 8.0% –7.2% $1.1 –$1.2 

2027 $6 $25 8.0% –7.2% $1.1 –$1.2 

2028 $6 $25 8.0% –7.2% $1.1 –$1.2 

2029 $6 $25 8.0% –7.2% $1.1 –$1.2 

2030 $6 $25 8.0% –7.2% $1.2 –$1.2 

2031 $6 $25 8.0% –7.2% $1.2 –$1.2 

2032 $6 $25 8.0% –7.2% $1.2 –$1.3 

2033 $6 $25 8.0% –7.2% $1.2 –$1.3 

2034 $6 $25 8.0% –7.2% $1.2 –$1.3 

2035 $6 $25 8.0% –7.2% $1.2 –$1.3 

2036 $6 $25 8.0% –7.2% $1.3 –$1.3 

2037 $6 $25 8.0% –7.2% $1.3 –$1.3 

2038 $6 $25 8.0% –7.2% $1.3 –$1.4 

NPV (3%) $21.7 –$20.6 

NPV (7%) $13.1 –$11.9 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-85 
Draft Regulatory Impact Analysis 

Table 9A-15: Impact on Small SI Equipment Market: Class II Gensets/Welders UL 250 

(Average Price per Equipment = $666)a,b 

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 $0 $1 0.1% –0.1% $0.0 –$0.2 

2009 $1 $1 0.1% –0.1% $0.7 –$0.2 

2010 $1 $1 0.1% –0.1% $0.8 –$0.2 

2011 $12 $34 5.2% –5.7% $7.8 –$7.5 

2012 $11 $34 5.2% –5.7% $7.9 –$7.7 

2013 $11 $34 5.1% –5.6% $7.9 –$7.7 

2014 $11 $34 5.1% –5.6% $8.0 –$7.9 

2015 $11 $34 5.1% –5.6% $8.0 –$8.0 

2016 $6 $24 3.6% –3.9% $4.5 –$5.7 

2017 $6 $24 3.6% –3.9% $4.5 –$5.8 

2018 $6 $24 3.6% –3.9% $4.6 –$5.9 

2019 $6 $24 3.6% –3.9% $4.7 –$6.0 

2020 $6 $24 3.6% –3.9% $4.8 –$6.1 

2021 $6 $24 3.6% –3.9% $4.8 –$6.2 

2022 $6 $24 3.6% –3.9% $4.9 –$6.3 

2023 $6 $24 3.6% –3.9% $5.0 –$6.4 

2024 $6 $24 3.6% –3.9% $5.0 –$6.5 

2025 $6 $24 3.6% –3.9% $5.1 –$6.6 

2026 $6 $24 3.6% –3.9% $5.2 –$6.6 

2027 $6 $24 3.6% –3.9% $5.3 –$6.7 

2028 $6 $24 3.6% –3.9% $5.3 –$6.8 

2029 $6 $24 3.6% –3.9% $5.4 –$6.9 

2030 $6 $24 3.6% –3.9% $5.5 –$7.0 

2031 $6 $24 3.6% –3.9% $5.6 –$7.1 

2032 $6 $24 3.6% –3.9% $5.6 –$7.2 

2033 $6 $24 3.6% –3.9% $5.7 –$7.3 

2034 $6 $24 3.6% –3.9% $5.8 –$7.4 

2035 $6 $24 3.6% –3.9% $5.8 –$7.5 

2036 $6 $24 3.6% –3.9% $5.9 –$7.6 

2037 $6 $24 3.6% –3.9% $6.0 –$7.7 

2038 $6 $24 3.6% –3.9% $6.1 –$7.8 

NPV (3%) $101.7 –$119.0 

NPV (7%) $60.9 –$68.9 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-86 
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,b 

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 $0 $1 0.2% –0.2% $0.0 –$0.1 

2009 $1 $1 0.2% –0.2% $0.3 –$0.1 

2010 $1 $1 0.2% –0.2% $0.3 –$0.1 

2011 $12 $35 10.2% –10.2% $3.3 –$2.8 

2012 $11 $35 10.1% –10.1% $3.3 –$2.9 

2013 $11 $35 10.1% –10.1% $3.3 –$2.9 

2014 $11 $35 10.0% –10.0% $3.3 –$2.9 

2015 $11 $35 10.0% –10.0% $3.4 –$3.0 

2016 $6 $25 7.0% –7.0% $1.9 –$2.2 

2017 $6 $25 7.0% –7.0% $1.9 –$2.2 

2018 $6 $25 7.0% –7.0% $1.9 –$2.2 

2019 $6 $25 7.0% –7.0% $2.0 –$2.3 

2020 $6 $25 7.0% –7.0% $2.0 –$2.3 

2021 $6 $25 7.0% –7.0% $2.0 –$2.3 

2022 $6 $25 7.0% –7.0% $2.1 –$2.4 

2023 $6 $25 7.0% –7.0% $2.1 –$2.4 

2024 $6 $25 7.0% –7.0% $2.1 –$2.4 

2025 $6 $25 7.0% –7.0% $2.1 –$2.5 

2026 $6 $25 7.0% –7.0% $2.2 –$2.5 

2027 $6 $25 7.0% –7.0% $2.2 –$2.5 

2028 $6 $25 7.0% –7.0% $2.2 –$2.6 

2029 $6 $25 7.0% –7.0% $2.3 –$2.6 

2030 $6 $25 7.0% –7.0% $2.3 –$2.6 

2031 $6 $25 7.0% –7.0% $2.3 –$2.7 

2032 $6 $25 7.0% –7.0% $2.4 –$2.7 

2033 $6 $25 7.0% –7.0% $2.4 –$2.7 

2034 $6 $25 7.0% –7.0% $2.4 –$2.8 

2035 $6 $25 7.0% –7.0% $2.5 –$2.8 

2036 $6 $25 7.0% –7.0% $2.5 –$2.8 

2037 $6 $25 7.0% –7.0% $2.5 –$2.9 

2038 $6 $25 7.0% –7.0% $2.5 –$2.9 

NPV (3%) $42.6 –$44.8 

NPV (7%) $25.5 –$26.0 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-87 
Draft Regulatory Impact Analysis 

Table 9A-17: Impact on Small SI Equipment Market: Class II Snowblowers UL 250 (Average
 

Price per Equipment = $665)a,b
 

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 $0 $1 0.1% –0.1% $0.0 –$0.1 

2009 $1 $1 0.1% –0.1% $0.6 –$0.1 

2010 $1 $1 0.1% –0.1% $0.6 –$0.1 

2011 $7 $5 0.8% –0.8% $3.7 –$0.8 

2012 $7 $5 0.8% –0.8% $3.7 –$0.8 

2013 $7 $5 0.8% –0.8% $3.7 –$0.8 

2014 $7 $5 0.8% –0.8% $3.7 –$0.9 

2015 $7 $5 0.8% –0.8% $3.8 –$0.9 

2016 $5 $4 0.6% –0.6% $3.0 –$0.7 

2017 $5 $4 0.6% –0.6% $3.1 –$0.7 

2018 $5 $4 0.6% –0.6% $3.1 –$0.7 

2019 $5 $4 0.6% –0.6% $3.2 –$0.7 

2020 $5 $4 0.6% –0.6% $3.2 –$0.7 

2021 $5 $4 0.6% –0.6% $3.3 –$0.7 

2022 $5 $4 0.6% –0.6% $3.3 –$0.8 

2023 $5 $4 0.6% –0.6% $3.4 –$0.8 

2024 $5 $4 0.6% –0.6% $3.4 –$0.8 

2025 $5 $4 0.6% –0.6% $3.5 –$0.8 

2026 $5 $4 0.6% –0.6% $3.5 –$0.8 

2027 $5 $4 0.6% –0.6% $3.6 –$0.8 

2028 $5 $4 0.6% –0.6% $3.6 –$0.8 

2029 $5 $4 0.6% –0.6% $3.7 –$0.8 

2030 $5 $4 0.6% –0.6% $3.7 –$0.8 

2031 $5 $4 0.6% –0.6% $3.8 –$0.9 

2032 $5 $4 0.6% –0.6% $3.8 –$0.9 

2033 $5 $4 0.6% –0.6% $3.9 –$0.9 

2034 $5 $4 0.6% –0.6% $3.9 –$0.9 

2035 $5 $4 0.6% –0.6% $4.0 –$0.9 

2036 $5 $4 0.6% –0.6% $4.0 –$0.9 

2037 $5 $4 0.6% –0.6% $4.0 –$0.9 

2038 $5 $4 0.6% –0.6% $4.1 –$0.9 

NPV (3%) $62.2 –$14.1 

NPV (7%) $35.9 –$8.2 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-88 
Economic Impact Analysis 

Appendix 9B: Impacts on Marine SI Markets 

This appendix provides the time series of impacts from 2008 through 2038 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, 2007). 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 9A-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. 

9-89 
Draft Regulatory Impact Analysis 

Table 9B-1: Impact on Marine SI Engine Market: 

<25hp (Average Price per Engine = $2,500)a 

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 $0 $0 0.0% 0.0% $0.0 $0.0 

2009 $74 $50 2.0% –3.6% $5.4 –$1.7 

2010 $74 $49 1.9% –3.6% $5.4 –$1.8 

2011 $74 $47 1.9% –3.9% $5.5 –$1.9 

2012 $74 $47 1.9% –3.9% $5.5 –$1.9 

2013 $74 $47 1.9% –3.9% $5.6 –$2.0 

2014 $55 $35 1.4% –3.1% $4.2 –$1.5 

2015 $55 $35 1.4% –3.1% $4.2 –$1.5 

2016 $55 $35 1.4% –3.0% $4.3 –$1.6 

2017 $55 $36 1.4% –2.9% $4.3 –$1.5 

2018 $55 $36 1.4% –2.9% $4.3 –$1.5 

2019 $55 $36 1.4% –2.9% $4.3 –$1.5 

2020 $55 $36 1.4% –2.9% $4.4 –$1.5 

2021 $55 $36 1.4% –2.9% $4.4 –$1.5 

2022 $55 $36 1.4% –2.9% $4.4 –$1.5 

2023 $55 $36 1.4% –2.9% $4.5 –$1.6 

2024 $55 $34 1.4% –3.1% $4.5 –$1.7 

2025 $55 $34 1.4% –3.1% $4.5 –$1.7 

2026 $55 $34 1.4% –3.1% $4.6 –$1.7 

2027 $55 $34 1.4% –3.1% $4.6 –$1.7 

2028 $55 $34 1.4% –3.1% $4.6 –$1.7 

2029 $55 $34 1.4% –3.1% $4.6 –$1.7 

2030 $55 $34 1.4% –3.1% $4.7 –$1.7 

2031 $55 $34 1.4% –3.1% $4.7 –$1.7 

2032 $55 $34 1.4% –3.1% $4.7 –$1.8 

2033 $55 $34 1.4% –3.1% $4.8 –$1.8 

2034 $55 $34 1.4% –3.1% $4.8 –$1.8 

2035 $55 $34 1.4% –3.1% $4.8 –$1.8 

2036 $55 $34 1.4% –3.1% $4.8 –$1.8 

2037 $55 $34 1.4% –3.1% $4.9 –$1.8 

2038 $55 $34 1.4% –3.1% $4.9 –$1.8 

NPV (3%) $90.1 –$32.0 

NPV (7%) $55.6 –$19.6 

a Figures are in 2005 dollars. 

9-90 
Economic Impact Analysis 

Table 9B-2: Impact on Marine SI Engine Market: 

26–50hp (Average Price per Engine = $5,700)a 

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 $0 $0 0.0% 0.0% $0.0 $0.0 

2009 $222 $187 3.3% –2.3% $12.1 –$1.9 

2010 $222 $185 3.3% –2.4% $12.2 –$2.0 

2011 $222 $185 3.3% –2.4% $12.2 –$2.0 

2012 $222 $183 3.2% –2.6% $12.3 –$2.1 

2013 $222 $183 3.2% –2.6% $12.4 –$2.1 

2014 $173 $142 2.5% –2.1% $9.8 –$1.7 

2015 $173 $142 2.5% –2.0% $9.8 –$1.7 

2016 $173 $142 2.5% –2.0% $9.9 –$1.7 

2017 $173 $142 2.5% –2.0% $10.0 –$1.7 

2018 $173 $143 2.5% –2.0% $10.0 –$1.7 

2019 $173 $143 2.5% –2.0% $10.1 –$1.7 

2020 $173 $143 2.5% –2.0% $10.2 –$1.7 

2021 $173 $143 2.5% –2.0% $10.2 –$1.8 

2022 $173 $143 2.5% –2.0% $10.3 –$1.8 

2023 $173 $143 2.5% –2.0% $10.4 –$1.8 

2024 $173 $143 2.5% –2.0% $10.4 –$1.8 

2025 $173 $143 2.5% –2.0% $10.5 –$1.8 

2026 $173 $143 2.5% –2.0% $10.6 –$1.8 

2027 $173 $143 2.5% –2.0% $10.6 –$1.8 

2028 $173 $143 2.5% –2.0% $10.7 –$1.8 

2029 $173 $143 2.5% –2.0% $10.8 –$1.8 

2030 $173 $143 2.5% –2.0% $10.9 –$1.9 

2031 $173 $143 2.5% –2.0% $10.9 –$1.9 

2032 $173 $143 2.5% –2.0% $11.0 –$1.9 

2033 $173 $143 2.5% –2.0% $11.1 –$1.9 

2034 $173 $143 2.5% –2.0% $11.1 –$1.9 

2035 $173 $143 2.5% –2.0% $11.2 –$1.9 

2036 $173 $143 2.5% –2.0% $11.3 –$1.9 

2037 $173 $143 2.5% –2.0% $11.3 –$1.9 

2038 $173 $143 2.5% –2.0% $11.4 –$2.0 

NPV (3%) $207.2 –$35.1 

NPV (7%) $127.2 –$21.5 

a Figures are in 2005 dollars. 

9-91 
Draft Regulatory Impact Analysis 

Table 9B-3: Impact on Marine SI Engine Market: 

51–100hp (Average Price per Engine = $9,100)a 

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 $0 $0 0.0% 0.0% $0.0 $0.0 

2009 $211 $182 2.0% –1.2% $17.2 –$2.3 

2010 $211 $180 2.0% –1.3% $17.3 –$2.5 

2011 $211 $180 2.0% –1.3% $17.4 –$2.5 

2012 $211 $178 1.9% –1.4% $17.5 –$2.7 

2013 $211 $178 1.9% –1.4% $17.7 –$2.8 

2014 $162 $136 1.5% –1.1% $13.7 –$2.2 

2015 $162 $136 1.5% –1.1% $13.8 –$2.3 

2016 $162 $136 1.5% –1.1% $13.9 –$2.2 

2017 $162 $136 1.5% –1.1% $14.0 –$2.2 

2018 $162 $137 1.5% –1.1% $14.1 –$2.2 

2019 $162 $137 1.5% –1.1% $14.2 –$2.2 

2020 $162 $137 1.5% –1.1% $14.3 –$2.2 

2021 $162 $137 1.5% –1.1% $14.4 –$2.3 

2022 $162 $137 1.5% –1.1% $14.5 –$2.3 

2023 $162 $137 1.5% –1.1% $14.6 –$2.3 

2024 $162 $137 1.5% –1.1% $14.7 –$2.3 

2025 $162 $137 1.5% –1.1% $14.8 –$2.3 

2026 $162 $137 1.5% –1.1% $14.9 –$2.3 

2027 $162 $137 1.5% –1.1% $15.0 –$2.4 

2028 $162 $137 1.5% –1.1% $15.1 –$2.4 

2029 $162 $137 1.5% –1.1% $15.2 –$2.4 

2030 $162 $137 1.5% –1.1% $15.3 –$2.4 

2031 $162 $137 1.5% –1.1% $15.4 –$2.4 

2032 $162 $137 1.5% –1.1% $15.5 –$2.4 

2033 $162 $137 1.5% –1.1% $15.6 –$2.4 

2034 $162 $137 1.5% –1.1% $15.7 –$2.5 

2035 $162 $137 1.5% –1.1% $15.7 –$2.5 

2036 $162 $137 1.5% –1.1% $15.8 –$2.5 

2037 $162 $137 1.5% –1.1% $15.9 –$2.5 

2038 $162 $137 1.5% –1.1% $16.0 –$2.5 

NPV (3%) $292.3 –$46.4 

NPV (7%) $179.7 –$29.5 

a Figures are in 2005 dollars. 

9-92 
Economic Impact Analysis 

Table 9B-4: Impact on Marine SI Engine Market: 

101–175hp (Average Price per Engine =$11,800)a 

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 $0 $0 0.0% 0.0% $0.0 $0.0 

2009 $371 $319 2.7% –1.6% $27.0 –$3.7 

2010 $371 $315 2.7% –1.7% $27.2 –$4.0 

2011 $371 $315 2.7% –1.7% $27.4 –$4.1 

2012 $371 $312 2.7% –1.8% $27.6 –$4.4 

2013 $371 $312 2.7% –1.8% $27.8 –$4.4 

2014 $284 $237 2.0% –1.4% $21.4 –$3.5 

2015 $284 $237 2.0% –1.4% $21.6 –$3.6 

2016 $284 $238 2.0% –1.4% $21.7 –$3.5 

2017 $284 $238 2.0% –1.4% $21.9 –$3.6 

2018 $284 $238 2.0% –1.4% $22.0 –$3.5 

2019 $284 $238 2.0% –1.4% $22.2 –$3.6 

2020 $284 $238 2.0% –1.4% $22.3 –$3.6 

2021 $284 $238 2.0% –1.4% $22.5 –$3.6 

2022 $284 $238 2.0% –1.4% $22.6 –$3.6 

2023 $284 $238 2.0% –1.4% $22.8 –$3.7 

2024 $284 $238 2.0% –1.4% $22.9 –$3.7 

2025 $284 $238 2.0% –1.4% $23.1 –$3.7 

2026 $284 $238 2.0% –1.4% $23.2 –$3.7 

2027 $284 $238 2.0% –1.4% $23.4 –$3.8 

2028 $284 $238 2.0% –1.4% $23.5 –$3.8 

2029 $284 $238 2.0% –1.4% $23.7 –$3.8 

2030 $284 $238 2.0% –1.4% $23.8 –$3.8 

2031 $284 $238 2.0% –1.4% $24.0 –$3.8 

2032 $284 $238 2.0% –1.4% $24.2 –$3.9 

2033 $284 $238 2.0% –1.4% $24.3 –$3.9 

2034 $284 $238 2.0% –1.4% $24.5 –$3.9 

2035 $284 $238 2.0% –1.4% $24.6 –$3.9 

2036 $284 $238 2.0% –1.4% $24.8 –$4.0 

2037 $284 $238 2.0% –1.4% $24.9 –$4.0 

2038 $284 $238 2.0% –1.4% $25.1 –$4.0 

NPV (3%) $457.3 –$72.3 

NPV (7%) $281.4 –$44.2 

a Figures are in 2005 dollars. 

9-93 
Draft Regulatory Impact Analysis 

Table 9B-5: Impact on Marine SI Engine Market: 

176–300hp (Average Price per Engine =$19,000)a 

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 $0 $0 0.0% 0.0% $0.0 $0.0 

2009 $527 $456 2.4% –1.3% $52.7 –$7.1 

2010 $527 $451 2.4% –1.4% $53.0 –$7.6 

2011 $527 $451 2.4% –1.4% $53.4 –$7.7 

2012 $527 $445 2.4% –1.5% $53.8 –$8.3 

2013 $527 $445 2.4% –1.5% $54.2 –$8.3 

2014 $402 $337 1.8% –1.2% $41.7 –$6.7 

2015 $402 $338 1.8% –1.2% $42.0 –$6.8 

2016 $402 $339 1.8% –1.2% $42.3 –$6.7 

2017 $402 $339 1.8% –1.2% $42.6 –$6.7 

2018 $402 $339 1.8% –1.2% $42.9 –$6.7 

2019 $402 $339 1.8% –1.2% $43.2 –$6.8 

2020 $402 $339 1.8% –1.2% $43.5 –$6.8 

2021 $402 $339 1.8% –1.2% $43.8 –$6.9 

2022 $402 $339 1.8% –1.2% $44.1 –$6.9 

2023 $402 $339 1.8% –1.2% $44.3 –$6.9 

2024 $402 $339 1.8% –1.2% $44.6 –$7.0 

2025 $402 $339 1.8% –1.2% $44.9 –$7.0 

2026 $402 $339 1.8% –1.2% $45.2 –$7.1 

2027 $402 $339 1.8% –1.2% $45.5 –$7.1 

2028 $402 $339 1.8% –1.2% $45.8 –$7.2 

2029 $402 $339 1.8% –1.2% $46.1 –$7.2 

2030 $402 $339 1.8% –1.2% $46.4 –$7.3 

2031 $402 $339 1.8% –1.2% $46.7 –$7.3 

2032 $402 $339 1.8% –1.2% $47.0 –$7.4 

2033 $402 $339 1.8% –1.2% $47.3 –$7.4 

2034 $402 $339 1.8% –1.2% $47.6 –$7.4 

2035 $402 $339 1.8% –1.2% $47.9 –$7.5 

2036 $402 $339 1.8% –1.2% $48.2 –$7.6 

2037 $402 $339 1.8% –1.2% $48.5 –$7.6 

2038 $402 $339 1.8% –1.2% $48.8 –$7.6 

NPV (3%) $890.6 –$137.3 

NPV (7%) $548.1 –$83.8 

a Figures are in 2005 dollars. 

9-94 
Economic Impact Analysis 

Table 9B-6: Impact on Marine SI Engine Market: 

300+ hp (Average Price per Engine = $18,000)a 

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 $0 $0 0.0% 0.0% $0.0 $0.0 

2009 $377 $343 1.6% –0.6% $11.9 –$1.4 

2010 $377 $337 1.5% –0.7% $12.0 –$1.6 

2011 $377 $337 1.5% –0.7% $12.1 –$1.7 

2012 $377 $328 1.5% –0.9% $12.2 –$2.0 

2013 $377 $328 1.5% –0.9% $12.3 –$2.0 

2014 $279 $239 1.1% –0.7% $9.2 –$1.7 

2015 $279 $239 1.1% –0.7% $9.3 –$1.7 

2016 $279 $241 1.1% –0.7% $9.3 –$1.6 

2017 $279 $241 1.1% –0.7% $9.4 –$1.6 

2018 $279 $241 1.1% –0.7% $9.5 –$1.6 

2019 $279 $241 1.1% –0.7% $9.5 –$1.6 

2020 $279 $241 1.1% –0.7% $9.6 –$1.6 

2021 $279 $241 1.1% –0.7% $9.7 –$1.6 

2022 $279 $241 1.1% –0.7% $9.7 –$1.7 

2023 $279 $241 1.1% –0.7% $9.8 –$1.7 

2024 $279 $241 1.1% –0.7% $9.9 –$1.7 

2025 $279 $241 1.1% –0.7% $9.9 –$1.7 

2026 $279 $241 1.1% –0.7% $10.0 –$1.7 

2027 $279 $241 1.1% –0.7% $10.1 –$1.7 

2028 $279 $241 1.1% –0.7% $10.1 –$1.7 

2029 $279 $241 1.1% –0.7% $10.2 –$1.7 

2030 $279 $241 1.1% –0.7% $10.3 –$1.8 

2031 $279 $241 1.1% –0.7% $10.3 –$1.8 

2032 $279 $241 1.1% –0.7% $10.4 –$1.8 

2033 $279 $241 1.1% –0.7% $10.4 –$1.8 

2034 $279 $241 1.1% –0.7% $10.5 –$1.8 

2035 $279 $241 1.1% –0.7% $10.6 –$1.8 

2036 $279 $241 1.1% –0.7% $10.6 –$1.8 

2037 $279 $241 1.1% –0.7% $10.7 –$1.8 

2038 $279 $241 1.1% –0.7% $10.8 –$1.8 

NPV (3%) $198.0 –$32.5 

NPV (7%) $122.2 –$19.7 

a Figures are in 2005 dollars. 

9-95 
Draft Regulatory Impact Analysis 

Table 9B-7: Impact on Marine Vessels Market: 

SD/I Recreational 175–300 hp (Average Price per Equipment = $32,367)a,b 

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 $0 $0 0.0% 0.0% $0.0 $0.0 

2009 $5 $156 0.5% –1.0% $0.2 –$4.9 

2010 $43 $174 0.5% –1.1% $1.6 –$5.5 

2011 $43 $174 0.5% –1.1% $1.6 –$5.5 

2012 $93 $198 0.6% –1.2% $3.4 –$6.3 

2013 $93 $198 0.6% –1.2% $3.4 –$6.3 

2014 $93 $160 0.5% –1.0% $3.5 –$5.1 

2015 $92 $159 0.5% –1.0% $3.5 –$5.2 

2016 $85 $156 0.5% –1.0% $3.2 –$5.1 

2017 $85 $156 0.5% –1.0% $3.2 –$5.1 

2018 $79 $153 0.5% –0.9% $3.0 –$5.1 

2019 $79 $153 0.5% –0.9% $3.0 –$5.1 

2020 $79 $153 0.5% –0.9% $3.1 –$5.1 

2021 $79 $153 0.5% –0.9% $3.1 –$5.2 

2022 $79 $153 0.5% –0.9% $3.1 –$5.2 

2023 $79 $153 0.5% –0.9% $3.1 –$5.2 

2024 $79 $153 0.5% –0.9% $3.1 –$5.3 

2025 $79 $153 0.5% –0.9% $3.2 –$5.3 

2026 $79 $153 0.5% –0.9% $3.2 –$5.3 

2027 $79 $153 0.5% –0.9% $3.2 –$5.4 

2028 $79 $153 0.5% –0.9% $3.2 –$5.4 

2029 $79 $153 0.5% –0.9% $3.3 –$5.5 

2030 $79 $153 0.5% –0.9% $3.3 –$5.5 

2031 $79 $153 0.5% –0.9% $3.3 –$5.5 

2032 $79 $153 0.5% –0.9% $3.3 –$5.6 

2033 $79 $153 0.5% –0.9% $3.3 –$5.6 

2034 $79 $153 0.5% –0.9% $3.4 –$5.6 

2035 $79 $153 0.5% –0.9% $3.4 –$5.7 

2036 $79 $153 0.5% –0.9% $3.4 –$5.7 

2037 $79 $153 0.5% –0.9% $3.4 –$5.7 

2038 $79 $153 0.5% –0.9% $3.4 –$5.8 

NPV (3%) $56.1 –$102.9 

NPV (7%) $32.5 –$62.6 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-96 
Economic Impact Analysis 

Table 9B-8: Impact on Marine Vessels Market: 

SD/I Luxury 300+ hp (Average Price per Equipment = $205,729)a,b 

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 $0 $0 0.0% 0.0% $0.0 $0.0 

2009 $11 $292 0.1% –0.3% $0.1 –$2.2 

2010 $142 $358 0.2% –0.3% $1.3 –$2.8 

2011 $142 $358 0.2% –0.3% $1.3 –$2.8 

2012 $312 $443 0.2% –0.4% $2.8 –$3.5 

2013 $312 $443 0.2% –0.4% $2.8 –$3.5 

2014 $312 $369 0.2% –0.4% $2.8 –$2.9 

2015 $311 $369 0.2% –0.4% $2.9 –$2.9 

2016 $285 $356 0.2% –0.3% $2.6 –$2.9 

2017 $285 $356 0.2% –0.3% $2.7 –$2.9 

2018 $271 $349 0.2% –0.3% $2.5 –$2.8 

2019 $271 $349 0.2% –0.3% $2.6 –$2.9 

2020 $271 $349 0.2% –0.3% $2.6 –$2.9 

2021 $271 $349 0.2% –0.3% $2.6 –$2.9 

2022 $271 $349 0.2% –0.3% $2.6 –$2.9 

2023 $271 $349 0.2% –0.3% $2.6 –$2.9 

2024 $271 $349 0.2% –0.3% $2.6 –$3.0 

2025 $271 $349 0.2% –0.3% $2.7 –$3.0 

2026 $271 $349 0.2% –0.3% $2.7 –$3.0 

2027 $271 $349 0.2% –0.3% $2.7 –$3.0 

2028 $271 $349 0.2% –0.3% $2.7 –$3.0 

2029 $271 $349 0.2% –0.3% $2.7 –$3.1 

2030 $271 $349 0.2% –0.3% $2.8 –$3.1 

2031 $271 $349 0.2% –0.3% $2.8 –$3.1 

2032 $271 $349 0.2% –0.3% $2.8 –$3.1 

2033 $271 $349 0.2% –0.3% $2.8 –$3.1 

2034 $271 $349 0.2% –0.3% $2.8 –$3.2 

2035 $271 $349 0.2% –0.3% $2.8 –$3.2 

2036 $271 $349 0.2% –0.3% $2.9 –$3.2 

2037 $271 $349 0.2% –0.3% $2.9 –$3.2 

2038 $271 $349 0.2% –0.3% $2.9 –$3.2 

NPV (3%) $46.7 –$56.7 

NPV (7%) $27.0 –$34.2 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-97 
Draft Regulatory Impact Analysis 

Table 9B-9: Impact on Marine Vessels Market: 

OB Recreational 50–100 hp (Average Price per Equipment = $21,569)a,b 

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 $0 $0 0.0% 0.0% $0.0 $0.0 

2009 $7 $130 0.6% –1.2% $0.4 –$0.2 

2010 $27 $139 0.6% –1.3% $1.7 –$0.8 

2011 $27 $139 0.6% –1.3% $1.7 –$0.8 

2012 $48 $149 0.7% –1.4% $3.1 –$1.4 

2013 $48 $149 0.7% –1.4% $3.1 –$1.5 

2014 $48 $120 0.6% –1.1% $3.2 –$1.5 

2015 $48 $119 0.6% –1.1% $3.1 –$1.5 

2016 $44 $118 0.5% –1.1% $2.9 –$1.3 

2017 $44 $118 0.5% –1.1% $2.9 –$1.4 

2018 $39 $115 0.5% –1.1% $2.6 –$1.2 

2019 $39 $115 0.5% –1.1% $2.6 –$1.2 

2020 $39 $115 0.5% –1.1% $2.6 –$1.2 

2021 $39 $115 0.5% –1.1% $2.6 –$1.2 

2022 $39 $115 0.5% –1.1% $2.7 –$1.2 

2023 $39 $115 0.5% –1.1% $2.7 –$1.2 

2024 $39 $115 0.5% –1.1% $2.7 –$1.3 

2025 $39 $115 0.5% –1.1% $2.7 –$1.3 

2026 $39 $115 0.5% –1.1% $2.7 –$1.3 

2027 $39 $115 0.5% –1.1% $2.8 –$1.3 

2028 $39 $115 0.5% –1.1% $2.8 –$1.3 

2029 $39 $115 0.5% –1.1% $2.8 –$1.3 

2030 $39 $115 0.5% –1.1% $2.8 –$1.3 

2031 $39 $115 0.5% –1.1% $2.8 –$1.3 

2032 $39 $115 0.5% –1.1% $2.8 –$1.3 

2033 $39 $115 0.5% –1.1% $2.9 –$1.3 

2034 $39 $115 0.5% –1.1% $2.9 –$1.3 

2035 $39 $115 0.5% –1.1% $2.9 –$1.3 

2036 $39 $115 0.5% –1.1% $2.9 –$1.4 

2037 $39 $115 0.5% –1.1% $2.9 –$1.4 

2038 $39 $115 0.5% –1.1% $2.9 –$1.4 

NPV (3%) $49.7 –$23.2 

NPV (7%) $29.2 –$13.6 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-98 
Economic Impact Analysis 

Table 9B-10: Impact on Marine Vessels Market: 

OB Luxury 175–300 hp (Average Price per Equipment = $104,598)a,b 

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 $0 $0 0.0% 0.0% $0.0 $0.0 

2009 $19 $763 0.7% –1.5% $0.1 –$2.5 

2010 $116 $804 0.8% –1.5% $0.4 –$2.6 

2011 $116 $804 0.8% –1.5% $0.4 –$2.6 

2012 $215 $845 0.8% –1.6% $0.8 –$2.8 

2013 $215 $845 0.8% –1.6% $0.8 –$2.8 

2014 $215 $672 0.6% –1.3% $0.8 –$2.2 

2015 $214 $672 0.6% –1.3% $0.8 –$2.3 

2016 $195 $663 0.6% –1.3% $0.8 –$2.2 

2017 $195 $663 0.6% –1.3% $0.8 –$2.3 

2018 $182 $658 0.6% –1.3% $0.7 –$2.3 

2019 $182 $658 0.6% –1.3% $0.7 –$2.3 

2020 $182 $658 0.6% –1.3% $0.7 –$2.3 

2021 $182 $658 0.6% –1.3% $0.7 –$2.3 

2022 $182 $658 0.6% –1.3% $0.7 –$2.3 

2023 $182 $658 0.6% –1.3% $0.7 –$2.3 

2024 $182 $658 0.6% –1.3% $0.8 –$2.4 

2025 $182 $658 0.6% –1.3% $0.8 –$2.4 

2026 $182 $658 0.6% –1.3% $0.8 –$2.4 

2027 $182 $658 0.6% –1.3% $0.8 –$2.4 

2028 $182 $658 0.6% –1.3% $0.8 –$2.4 

2029 $182 $658 0.6% –1.3% $0.8 –$2.4 

2030 $182 $658 0.6% –1.3% $0.8 –$2.4 

2031 $182 $658 0.6% –1.3% $0.8 –$2.5 

2032 $182 $658 0.6% –1.3% $0.8 –$2.5 

2033 $182 $658 0.6% –1.3% $0.8 –$2.5 

2034 $182 $658 0.6% –1.3% $0.8 –$2.5 

2035 $182 $658 0.6% –1.3% $0.8 –$2.5 

2036 $182 $658 0.6% –1.3% $0.8 –$2.5 

2037 $182 $658 0.6% –1.3% $0.8 –$2.6 

2038 $182 $658 0.6% –1.3% $0.8 –$2.6 

NPV (3%) $13.4 –$46.4 

NPV (7%) $7.8 –$28.4 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-99 
Draft Regulatory Impact Analysis 

Table 9B-11: Impact on Marine Vessels Market: 

PWC 100–175 hp (Average Price per Equipment = $9,986)a,b 

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 $0 $0 0.0% 0.0% $0.0 $0.0 

2009 $98 $63 0.6% –1.3% $5.8 –$2.2 

2010 $98 $63 0.6% –1.3% $5.8 –$2.2 

2011 $98 $73 0.7% –1.5% $5.9 –$2.6 

2012 $98 $73 0.7% –1.5% $5.9 –$2.6 

2013 $98 $73 0.7% –1.5% $6.0 –$2.6 

2014 $68 $54 0.5% –1.1% $4.2 –$1.9 

2015 $68 $54 0.5% –1.1% $4.2 –$1.9 

2016 $68 $54 0.5% –1.1% $4.2 –$2.0 

2017 $68 $50 0.5% –1.0% $4.2 –$1.8 

2018 $68 $50 0.5% –1.0% $4.3 –$1.8 

2019 $68 $50 0.5% –1.0% $4.3 –$1.9 

2020 $68 $50 0.5% –1.0% $4.3 –$1.9 

2021 $68 $50 0.5% –1.0% $4.4 –$1.9 

2022 $68 $50 0.5% –1.0% $4.4 –$1.9 

2023 $68 $50 0.5% –1.0% $4.4 –$1.9 

2024 $68 $50 0.5% –1.0% $4.4 –$1.9 

2025 $68 $50 0.5% –1.0% $4.5 –$1.9 

2026 $68 $50 0.5% –1.0% $4.5 –$1.9 

2027 $68 $50 0.5% –1.0% $4.5 –$2.0 

2028 $68 $50 0.5% –1.0% $4.6 –$2.0 

2029 $68 $50 0.5% –1.0% $4.6 –$2.0 

2030 $68 $50 0.5% –1.0% $4.6 –$2.0 

2031 $68 $50 0.5% –1.0% $4.7 –$2.0 

2032 $68 $50 0.5% –1.0% $4.7 –$2.0 

2033 $68 $50 0.5% –1.0% $4.7 –$2.0 

2034 $68 $50 0.5% –1.0% $4.7 –$2.0 

2035 $68 $50 0.5% –1.0% $4.8 –$2.1 

2036 $68 $50 0.5% –1.0% $4.8 –$2.1 

2037 $68 $50 0.5% –1.0% $4.8 –$2.1 

2038 $68 $50 0.5% –1.0% $4.9 –$2.1 

NPV (3%) $91.2 –$39.2 

NPV (7%) $56.8 –$24.3 

a Figures are in 2005 dollars. b Average price per equipment for the market is a weighted average of the price of equipment by hp. 

9-100 
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 2038. 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 discount rate determines the 

present value of the total social costs of the program. 

9-101 
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 –$7.5 –$118.2 –$128.5 –$331.6 –$477.2 –$481.1 –$460.7 –$465.4 –$38

Marine SI 

End users (households) $0.0 –$110.6 –$116.1 –$117.8 –$124.2 –$125.1 –$99.6 –$100.3 –$10

Small SI 

End users (households) –$7.5 –$7.6 –$12.4 –$213.7 –$353.0 –$356.0 –$361.0 –$365.1 –$28

Producer Surplus Change, Total –$2.0 –$50.6 –$59.5 –$131.8 –$160.9 –$162.3 –$152.5 –$153.6 –$12

Marine SI $0.0 –$48.5 –$54.8 –$56.0 –$63.3 –$63.8 –$52.6 –$52.9 –$52

Engine manufacturers $0.0 –$18.1 –$19.5 –$19.8 –$21.4 –$21.5 –$17.4 –$17.5 –$17Equipment manufacturers $0.0 –$30.4 –$35.3 –$36.2 –$41.9 –$42.2 –$35.2 –$35.4 –$34

Small SI –$2.0 –$2.1 –$4.7 –$75.8 –$97.6 –$98.5 –$99.9 –$100.8 –$73

Engine manufacturers –$0.4 –$0.4 –$0.4 –$10.9 –$18.2 –$18.4 –$18.6 –$18.9 –$15Equipment manufacturers –$1.7 –$1.7 –$4.3 –$64.8 –$79.4 –$80.2 –$81.3 –$81.9 –$58

Fuel Savings $3.1 $13.7 $25.4 $64.9 $103.5 $136.5 $161.2 $182.3 $200

Consumer savings $3.8 $16.7 $30.9 $78.8 $125.7 $165.9 $195.9 $221.5 $244Fuel $3.1 $13.7 $25.4 $64.9 $103.5 $136.5 $161.2 $182.3 $200Tax $0.7 $3.0 $5.5 $13.9 $22.2 $29.3 $34.7 $39.2 $43Government revenue –$0.7 –$3.0 –$5.5 –$13.9 –$22.2 –$29.3 –$34.7 –$39.2 –$43

Total Surplus Change –$6.4 –$155.1 –$162.6 –$398.5 –$534.7 –$506.9 –$451.9 –$436.7 –$31
Table 9C: Time Series Projection of Social Costs (Million $) (continued) 

2019 2020 2021 2022 2023 2024 2025 2026 20

Consumer Surplus Change, Total –$374.1 –$378.9 –$383.8 –$388.6 –$393.5 –$398.4 –$403.3 –$408.2 –$4

Marine SI 

End users (households) –$100.9 –$101.6 –$102.3 –$102.9 –$103.6 –$104.4 –$105.1 –$105.8 –$1

Small SI 

End users (households) –$273.2 –$277.4 –$281.5 –$285.7 –$289.9 –$294.1 –$298.3 –$302.5 –$3

Producer Surplus Change, Total –$124.3 –$125.8 –$127.3 –$128.7 –$130.2 –$131.9 –$133.3 –$134.8 –$1

Marine SI –$51.7 –$52.0 –$52.4 –$52.7 –$53.1 –$53.7 –$54.0 –$54.4 –$

Engine manufacturers –$17.4 –$17.5 –$17.6 –$17.8 –$17.9 –$18.1 –$18.2 –$18.3 –$Equipment manufacturers –$34.3 –$34.5 –$34.7 –$35.0 –$35.2 –$35.6 –$35.8 –$36.0 –$

Small SI –$72.7 –$73.8 –$74.9 –$76.0 –$77.1 –$78.2 –$79.3 –$80.5 –$

Engine manufacturers –$14.1 –$14.3 –$14.5 –$14.8 –$15.0 –$15.2 –$15.4 –$15.6 –$Equipment manufacturers –$58.6 –$59.5 –$60.4 –$61.2 –$62.1 –$63.0 –$63.9 –$64.8 –$

Fuel Savings $242.1 $253.1 $263.3 $272.9 $281.4 $289.3 $296.6 $303.6 $3

Consumer savings $294.2 $307.5 $319.9 $331.6 $341.9 $351.5 $360.4 $368.8 $3Fuel $242.1 $253.1 $263.3 $272.9 $281.4 $289.3 $296.6 $303.6 $3Tax $52.0 $54.4 $56.6 $58.7 $60.5 $62.2 $63.8 $65.2 $Government revenue –$52.0 –$54.4 –$56.6 –$58.7 –$60.5 –$62.2 –$63.8 –$65.2 –$

Total Surplus Change –$256.2 –$251.6 –$247.7 –$244.4 –$242.2 –$241.0 –$240.0 –$239.5 –$2
Table 9C: Time Series Projection of Social Costs (million $) (continued) 

2030 2031 2032 2033 2034 2035 2036 2037 2038 

Consumer Surplus Change, Total –$427.8 –$432.7 –$437.6 –$442.6 –$447.5 –$452.4 –$457.3 –$462.2 –$467.

Marine SI 

End users (households) –$108.5 –$109.2 –$109.9 –$110.6 –$111.3 –$112.0 –$112.7 –$113.4 –$114.

Small SI 

End users (households) –$319.3 –$323.5 –$327.7 –$332.0 –$336.2 –$340.4 –$344.6 –$348.8 –$353.0 

Producer Surplus Change, Total –$140.7 –$142.2 –$143.7 –$145.2 –$146.6 –$148.1 –$149.6 –$151.1 –$152.5 

Marine SI –$55.8 –$56.1 –$56.5 –$56.9 –$57.2 –$57.6 –$57.9 –$58.3 –$58.6 

Engine manufacturers –$18.8 –$18.9 –$19.1 –$19.2 –$19.3 –$19.4 –$19.5 –$19.7 –$19.8 Equipment manufacturers –$37.0 –$37.2 –$37.4 –$37.7 –$37.9 –$38.2 –$38.4 –$38.6 –$38.9 

Small SI –$84.9 –$86.1 –$87.2 –$88.3 –$89.4 –$90.6 –$91.7 –$92.8 –$93.9 

Engine manufacturers –$16.5 –$16.7 –$16.9 –$17.1 –$17.4 –$17.6 –$17.8 –$18.0 –$18.2 Equipment manufacturers –$68.5 –$69.4 –$70.3 –$71.2 –$72.1 –$73.0 –$73.9 –$74.8 –$75.7 

Fuel Savings $327.3 $332.3 $337.1 $341.7 $346.1 $350.4 $354.5 $358.5 $362.5 

Consumer savings $397.6 $403.7 $409.5 $415.1 $420.5 $425.7 $430.7 $435.6 $440.4 Fuel $327.3 $332.3 $337.1 $341.7 $346.1 $350.4 $354.5 $358.5 $362.5 Tax $70.3 $71.4 $72.4 $73.4 $74.4 $75.3 $76.2 $77.1 $77.9 Government revenue –$70.3 –$71.4 –$72.4 –$73.4 –$74.4 –$75.3 –$76.2 –$77.1 –$77.9 

Total Surplus Change –$241.3 –$242.6 –$244.2 –$246.0 –$248.0 –$250.1 –$252.3 –$254.7 –$257.

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 Metcalfe (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 perfect competition (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: 

9-105 
Draft Regulatory Impact Analysis 

∧ 

Q$

s = ε s ( p$ − MC ) (9D.3) 

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(Δ pengine ) c + α(Δ 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: 

Q $ $ engines = Q equipment (9D.5) d s 

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 = Q$s (9D.6) 

9-106 
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* 

P rice P ′ In c rease 

P 

D 

Q /t 

S1 : W ith R eg u la tio n 

A B 

U n it Co s t 

In c rease 

S 0: W ith o ut 

R egula tion 

C 

9-107 
Draft 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: 

Pi+1 = P1 •
 

⎛

⎜

qd ⎞

⎟


 

z 

(9D.7)
 

⎝
 qs ⎠
 

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. 

9-108 
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 

9-109 
Draft 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. 

9-110 
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 2.3 EPA econometric 

except PWC estimate 

Table 9E-4 

PWC 3.4	 EPA econometric 

estimate 

Table 9E-5 

Small SI 

All lawn and 3.4 EPA econometric 

garden estimate 

equipment Table 9E-6 

Generators 3.3	 EPA econometric 

estimate 

Table 9E-7 

All Engines 3.8 EPA econometric 

Categories estimate 

Table 9E-3 

Cobb-Douglas production 

function 

Cobb-Douglas production 

function 

Cobb-Douglas production 

function 

Cobb-Douglas production 

function 

Cobb-Douglas production 

function 

Bartlesman et al. 

(2000); 1958–1996; 

SIC 3732 

Bartlesman et al. 

(2000); 1958–1996; 

SIC 3799 

Bartlesman et al. 

(2000); 1958–1996; 

SIC 3524 

Bartlesman et al. 

(2000); 1966–1996; 

SIC 3621 

Bartlesman et al. 

(2000); 1958–1996; 

SIC 3519 

9-111 
Draft 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) 1958–1996; SIC 3732 

PWC) Table 9E-8 

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, Table 9E-9, equation (2SLS) 

general 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. 

9-112 
Economic Impact Analysis 

9E.1 Supply Elasticities 

We use a two-steps approach to estimate the price elasticity of supply. 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 industry 

follows the Cobb-Douglas production function, and is specified as 

" " " Qt

 = A (Kt) K (Lt) L (Mt) M t8 (9E.1) 

where 

Qt = output in year t, 

Kt = real capital consumed in production in year t, 

Lt = quantity of labor used in year t, 

Mt = material inputs in year t, and 

t = a time trend variable to reflect technology changes. 

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 Qt = ln A + "K ln Kt + "L ln Lt + "M ln Mt + 8 ln t (E9.2) 

Under the assumptions of a competitive market and perfect competition, 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:14 

Supply Elasticity = ("L + "M ) / (1 – "L – "M). (9E.3) 

To maintain the desired properties of the Cobb-Douglas production function, the analyst 

must place restrictions on the estimated coefficients. For example, if "L + "M = 1, then the supply 

elasticity will be undefined. Alternatively, if "L + "M > 1, this yields a negative supply elasticity. 

Thus, a common assumption is that "K + "L + "M = 1. This implies constant returns to scale, 

which is consistent with most empirical studies. 

14 Appendix 9F provides the derivation of this result. 

9-113 
Draft Regulatory Impact Analysis 

9E.1.1 Data Sets 

The National Bureau of Economic Research-Center for Economic Studies (Bartlesman, 

Becker, and Gray, 2000) publishes industry-level data used for the analysis. 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).15 The following 

variables were used: 

C value of shipments (NBER-CES), 

C price index of value shipments (NBER-CES), 

C production worker wages (NBER-CES), 

C GDP deflator (BEA) 

C cost of materials (NBER-CES), 

C price index for materials (NBER-CES), and 

C value added (NBER-CES). 

To provide a measure of capital consumed, a capital variable was calculated as follows: 

Capital = (Value added – Production worker wages)/GDP deflator 

9E.1.2 Results of Supply Elasticity Estimation 

We used an autoregressive error model to estimate Eq. (9E.2). SAS procedure PROC 

AUTOREG computes a linear regression corrected for serial correlation. We assume the error 

term is AR(2). This approach is identical to the one used successfully for the Nonroad CI 

Engines and Equipment EIA completed in 2003 (EPA, 2004), with some of the data series 

updated with the most recent data. Using this model, reasonable estimates were obtained for 

Small SI products. Durbin-Watson statistics were calculated to check for autocorrelation and 

Goldfeld-Quandt tests to check for heteroskedasticity. As shown in Tables 9E-3 through 9E-7, 

supply elasticity estimates for Small SI products range from 2.3 (Boat Building) to 3.8 

(Engines). 

15 All values are expressed in $1987. Note the GDP deflators have been updated since RTI’s estimation of 

supply elasticities for the nonroad rule. As a result, the elasticity estimation method is the same; however, the 

coefficient estimates may vary slightly. 

9-114 
Economic Impact Analysis 

Table 9E-3: Gasoline Engines: SIC 3519 Internal Combustion Engines, Not Elsewhere 

Classified: 1958 to 1996 

Number of Observations = 39 

Total R-square = 0.9978 

Durbin-Watson = 1.80 (1% critical values = 1.085, 1.517) 

Goldfeld-Quandt F = 3.10 (p-value = 0.018); DF=14 

Supply Elasticity = 3.8 

Variable Estimated Coefficients t-statistic p value 

intercept 0.962 24.21 <0.0001 

ln K 0.207 4.73 <0.0001 

ln L 0.207 5.60 <0.0001 

ln M 0.587 13.04 <0.0001 

ln t 0.022 2.37 0.0238 

Table 9E-4: Gasoline-Powered Boats: SIC 3732 Boat Building and Repairing: 1958 to 1996 

Number of Observations = 39 

Total R-square = 0.9976 

Durbin-Watson = 1.89 (1% critical values = 1.085, 1.517) 

Goldfeld-Quandt F = 1.76 (p-value = 0.141); DF=14 

Supply Elasticity = 2.3 

Variable Estimated Coefficients t-statistic p-value 

intercept 1.144 25.42 <0.0001 

ln K 0.303 5.73 <0.0001 

ln L 0.328 7.28 <0.0001 

ln M 0.369 7.34 <0.0001 

ln t 0.022 1.56 0.1295 

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Table 9E-5: PWCs, ATVs, Snowmobiles: SIC 3799 Transportation Equipment, Not Elsewhere 

Classified: 1958 to 1996 

Number of Observations = 39 

Total R-square = 0.9978 

Durbin-Watson = 1.758 (1% critical values = 1.085, 1.517) 

Goldfeld-Quandt F = 2.99 (p-value = 0.025); DF=14 

Supply Elasticity = 3.4 

Variable Estimated Coefficients t-statistic p value 

intercept 0.786 19.4 <0.0001 

ln K 0.229 10.4 <0.0001 

ln L 0.127 4.57 <0.0001 

ln M 0.644 20.2 <0.0001 

ln t 0.028 2.90 0.0065 

Table 9E-6: Small Handheld/Nonhandheld: SIC 3524 Lawn and Garden Tractors and Home 

Lawn and Garden Equipment: 1958 to 1996 

Number of Observations = 39 

Total R-square = 0.9964 

Durbin-Watson = 1.71 (1% critical values = 1.085, 1.517) 

Goldfeld-Quandt F = 2.08 (p-value = 0.084); DF=14 

Supply Elasticity = 3.4 

Variable Estimated Coefficients t-statistic p value 

intercept 0.662 13.03 <0.0001 

ln K 0.225 3.69 0.0008 

ln L 0.068 1.79 0.0822 

ln M 0.707 11.09 <0.0001 

ln t 0.042 2.77 0.0091 

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Table 9E-7: Gensets and Marine Generators: SIC 3621 Motors and Generators: 1966 to 1996 

Number of Observations = 31 

Total R-square = 0.9930 

Durbin-Watson = 1.749 (1% critical values = 0.960,1.510 ) 

Goldfeld-Quandt F = 0.89 (p-value = 0.576); DF=11 

Supply Elasticity = 3.3 

Variable Estimated Coefficients t-statistic p value 

intercept 1.0119 19.6 <0.0001 

ln K 0.2346 4.62 <0.0001 

ln L 0.1574 3.15 0.0042 

ln M 0.6081 11.64 <0.0001 

ln t –0.0127 –0.51 0.6176 

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 

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Draft Regulatory Impact Analysis 

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 

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 

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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 

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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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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Economic 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. 

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Draft Regulatory 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. 

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Economic 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 proposed 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 

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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 

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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Economic 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 

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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. 

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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), how costs are treated by 

producers, what the baseline equipment prices are used in the model. This appendix presents a 

sensitivity analysis for several alternatives in the model. Three scenarios are examined: 

# Scenario 1: alternative market supply and demand elasticity parameters 

# Scenario 2: alternative ways to treat engineering compliance costs 

# Scenario 3: alternative baseline prices for lawn mower and tractor 

The results of these sensitivity analyses are presented below. The results from Scenario 1 

to 3 are presented for 2013 (the highest cost year) only with 2005$. These 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 around 0.5 percent. Total social costs are about the same across all 

sensitivity analysis scenarios, $507 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 70 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 70 to 90 percent. 

In the alternative engineering compliance cost scenario, there are differences in the way 

the social costs are shared among producers and consumers in the market, although total social 

costs are about the same. The share of the social costs borne by either engine manufacturer or 

equipment manufacturer increases under this scenario because engines and equipment 

manufactures can not recover the fixed cost required in this rule. Especially for the Small SI 

market, the difference in the share of social cost borne by engine and equipment manufacturer is 

more than 16 percent. 

With regard to the scenario of alternative baseline prices, although the difference in 

prices is about 25.5% and 53.0% 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. 

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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 reflect a 95 percent confidence interval (see Appendix 9E). 

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Economic Impact Analysis 

Table 9H-1: Alternative Supply and Demand Elasticities Used in Sensitivity Analysisa 

Parameter/Market Upper Bound Primary Case Lower Bound 

Supply Elasticities 

Engines 

Marine and Small SI 4.2 3.8 3.5 

Equipment 

Marine SI 

All other vessel types 2.5 2.3 2.1 

PWC 3.5 3.4 3.2 

Small SI 

Small SI (handheld/nonhandheld) 3.9 3.4 3.0 

Gensets/welders 3.6 3.3 2.9 

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 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 (Appendix 9E). 

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 0.1 percent. Absolute 

quantities vary but the percentage changes in output are negligible for the two scenarios. The 

change in total social surplus for 2013 also remains nearly unchanged across all scenarios and is 

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Draft Regulatory Impact Analysis 

approximately the same as for the rule ($507 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 3.8 and 16.0 percent, 

respectively, in the supply upper bound scenario compared to 4.0 and 17.6 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 10.8 and 21.6 percent, respectively, in 

supply upper bound scenario compared to 11.4 and 22.4 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). 

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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 $256.8 2.3% $255.1 2.3% $259.3 2.3% 

Equipment $231.7 1.3% $222.0 1.3% $240.8 1.4% 

Quantity 

Engines –8,846 –2.0% –8,406 –1.9% –9,297 –2.1% 

Equipment –10,847 –2.7% –10,443 –2.6% –11,196 –2.8% 

Welfare Impacts (million $) 

Change in engine manufacturers $21.5 11.4% $22.3 11.8% $20.4 10.8% 

surplus 

Change in equipment manufacturers $42.2 22.4% $44.1 23.3% $40.8 21.6% 

surplus 

Change in end user (households) $125.1 66.2% $122.7 64.9% $127.6 67.6% 

surplus 

Small SI 

Market-Level Impacts 

Price 

Engines $22.3 11.7% $22.2 11.7% $22.3 11.8% 

Equipment $13.8 3.1% $13.5 3.1% $14.2 3.2% 

Class I $18.6 6.9% $18.3 6.9% $18.9 7.0% 

Class II $40.5 3.9% $39.1 3.8% $41.6 4.0% 

HH $0.3 0.3% $0.3 0.3% $0.3 0.4% 

Quantity 

Engines –371,097 –2.35 –361,097 –2.3% –380,910 –2.4% 

Equipment –482,942 –1.9% –467,931 –1.8% –498,041 –1.9% 

Class I –219,400 –2.2% –214,334 –2.2% –224,691 –2.3% 

Class II –157,306 –4.3% –152,207 –4.1% –161,996 –4.4% 

HH –106,236 –0.6% –101,390 –0.6% –111,354 –0.7% 

Welfare Impacts (million $) 

Change in engine manufacturers $18.4 4.0% $19.4 4.3% $17.1 3.8% 

surplus 

Change in equipment manufacturers $80.2 17.6% $88.1 19.4% $72.6 16.0% 

surplus 

Change in end user (households) $356.0 78.3% $347.1 76.4% $364.6 80.3% 

surplus 

Subtotal Social Costs (million $) $643.4 $643.7 $643.1 

Fuel Savings (million $) $136.5 $136.5 $136.5 

Total Social Costs (million $) $506.9 $507.1 $506.6 

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). 

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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 are 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. 

9-132 
Economic Impact Analysis 

Demand Lower Bound 

Absolute Relativeb 

$301.6 2.8% 

$448.4 2.5% 

–972 –0.2%

–1,016 –0.2%

$2.3 1.2% 

$4.0 2.1% 

$185.7 96.7%

$23.0 12.1%

$16.4 3.5% 

$20.4 7.6% 

$46.4 4.4% 

$0.3 0.4% 

–136,358 –0.9%

–219,030 –0.8% 

–78,053 –1.0% 

–59,011 –3.0% 

–81,967 –0.5% 

$7.0 1.5% 

$26.1 5.7% 

$424.9 92.8%

$650.0

$136.5 

$513.5

Table 9H-3: Sensitivity Analysis for Equipment Market Demand Elasticities for 2013 a,b 

Primary Case Demand Upper Bound 

Scenario Absolute Relativeb Absolute Relativeb 

Marine 

Market-Level Impacts 

Price 

Engines $256.8 2.3% $242.5 2.1% 

Equipment $231.7 1.3% $157.4 0.9% 

Quantity 

Engines –8,846 –2.0% –11,205 –2.6% 

Equipment –10,847 –2.7% –14,646 –3.6% 

Welfare Impacts (million $) 

Change in engine manufacturers surplus $21.5 11.4% $27.6 14.7% 

Change in equipment manufacturers $42.2 22.4% $56.2 30.0% 

surplus 

Change in end user (households) surplus $125.1 66.2% $103.8 55.3% 

Small SI 

Market-Level Impacts 

Price 

Engines $22.3 11.7% $21.7 11.5% 

Equipment $13.8 3.1% $12.1 2.8% 

Class I $18.6 6.9% $17.1 6.4% 

Class II $40.5 3.9% $36.3 3.6% 

HH $0.3 0.3% $0.3 0.3% 

Quantity 

Engines –371,097 –2.35 –542,349 –3.4% 

Equipment –482,942 –1.9% –676,766 –2.6% 

Class I –219,400 –2.2% –328,416 –3.3% 

Class II –157,306 –4.3% –222,780 –5.2% 

HH –106,236 –0.6% –125,569 –0.8% 

Welfare Impacts (million $) 

Change in engine manufacturers surplus $18.4 4.0% $26.3 5.8% 

Change in equipment manufacturers $80.2 17.6% $116.1 25.7% 

surplus 

Change in end user (households) surplus $356.0 78.3% $309.6 68.5% 

Subtotal Social Costs (million $) $643.4 $639.6

Fuel Savings (million $) $136.5 $136.5

Total Social Costs (million $) $506.9 $503.1 

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). 

9-133
 
Draft Regulatory 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 2013 compared to the primary 

case ($507 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 1.5 and 5.7 percent, respectively, in the demand lower bound 

scenario compared to 4.0 and 17.6 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 1.2 and 2.1 percent, respectively, in demand lower bound scenario compared 

to 11.4 and 22.4 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). 

9-134
 
Economic Impact Analysis 

9H.2 Engine and Equipment Variable Cost Shift Scenario 

As discussed in Section 9.2, the total costs (fixed plus variable cost) are used to shift the 

supply curve in the engines and equipment markets. This is because Small SI and Marine SI 

engine and equipment manufacturers produce a product that changes very little over time. These 

manufacturers do not engage in research and development to improve their products on a 

continuous basis (as opposed to highway vehicles or nonroad engines and equipment). The 

product changes that would be required to comply with the proposed standards will require these 

manufacturers to devote new funds and resources to product redesign and facilities changes. 

Therefore, Small SI and Marine SI engine and equipment manufacturers are expected to increase 

their prices by the full amount of the compliance costs to recover those 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. The sensitivity 

analysis was performed to investigate the impacts under the alternative scenario of shifting the 

supply curve by the variable costs only. The results of that analysis are shown at Table 9H-4. 

In this scenario, engine and equipment manufacturers are able to pass along the variable 

compliance costs only rather than full costs including the fixed compliance costs. As expected, 

this scenario leads to a lower projected price increases for the engine and equipment markets 

(from 11.7 and 3.1 percent in the baseline case to 10.3 and 2.7 percent for Small SI engine and 

equipment markets; from 2.3 and 1.3 percent in the baseline case to 2.2 and 1.2 percent for 

Marine SI engine and equipment markets). The share of the social costs borne by Small SI 

engine and equipment manufacturers are increased by 10.4 and 5.9 percent, respectively. The 

share of the social costs borne by Marine SI engine and equipment manufacturers are also 

increased by 2.7 and 0.4 percent, respectively. However, the total social costs of the regulation 

are not expected to change measurably as the lower prices lead to almost no change in the 

demand for equipment and engines. 

9-135
 
Draft Regulatory Impact Analysis 

Table 9H-4: Variable Costs only to Shift Supply Curve in Engine and Equipment Markets 

for 2013 a,b 

Fixed and Variable Cost 

Supply Shift Scenario 

Scenario Absolute Relativeb 

Marine 

Market-Level Impacts 

Price 

Engines $256.8 2.3% 

Equipment $231.7 1.3% 

Quantity 

Engines –8,846 –2.0% 

Equipment –10,847 –2.7% 

Welfare Impacts (million $) 

Change in engine manufacturers surplus $21.5 11.4% 

Change in equipment manufacturers surplus $42.2 22.4% 

Change in end user (households) surplus $125.1 66.2% 

Variable Cost Only Supply
 

Shift Scenario
 

Absolute Relativeb 

$245.0 

$219.9 

2.2% 

1.2% 

–8,264 

–10,136 

–1.9% 

–2.5% 

$26.7 

$43.0 

$119.3 

14.1% 

22.8% 

63.1% 

Small SI 

Market-Level Impacts 

Price 

Engines $22.3 11.7% $19.3 10.3% 

Equipment $13.8 3.1% $11.0 2.7% 

Class I $18.6 6.9% $16.1 6.0% 

Class II $40.5 3.9% $30.1 3.1% 

HH $0.3 0.3% $0.3 0.3% 

Quantity 

Engines –371,097 –2.35 –309,280 –1.9% 

Equipment –482,942 –1.9% –419,339 –1.6% 

Class I –219,400 –2.2% –189,939 –1.9% 

Class II –157,306 –4.3% –125,945 –3.3% 

HH –106,236 –0.6% –105,454 –0.6% 

Welfare Impacts (million $) 

Change in engine manufacturers surplus $18.4 4.0% $65.8 14.4% 

Change in equipment manufacturers surplus $80.2 17.6% $107.1 23.5% 

Change in end user (households) surplus $356.0 78.3% $283.6 62.1% 

Subtotal Social Costs (million $) $643.4 $645.5 

Fuel Savings (million $) $136.5 $136.5 

Total Social Costs (million $) $506.9 $509.0 

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). 

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Economic Impact Analysis 

9H.3 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-5: Market Sensitivity Analysis for Alternative Baseline for Lawnmower &
 

Tractor Prices in 2013 a,b
 

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 

(Household 

s) Surplus 

(Million $) 

Change in 

Equipment 

Manufacture 

r Surplus 

(Million $) 

Change in 

Total 

Surplus 

(Million $) 

Lawn Mowers 

Primary 

scenario 

Low price 

scenario 

Tractors 

Primary 

scenario 

Low price 

scenario 

$243 

$181 

$1,937 

$928 

$14.38 

$14.29 

$35.15 

$34.69 

5.9% –90,263 

7.9% –120,912 

1.8% –35,706 

3.7% –73,559 

–1.1% 

–1.5% 

–1.8% 

–3.7% 

–$115 –$6 –$121 

–$114 –$6 –$120 

–$69 –$20 –$89 

–$67 –$20 –$87 

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-5, 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-5, 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 the stakeholders. 

9-137
 

Small-Business Flexibility Analysis 

CHAPTER 10: Small-Business Flexibility Analysis 

This chapter discusses our Initial Regulatory Flexibility Analysis (IRFA) which evaluates 

the potential impacts of the proposed standards on small entities. The Regulatory Flexibility 

Act, as amended by the Small Business Regulatory Enforcement Fairness Act of 1996 

(SBREFA), generally requires an agency to prepare a regulatory flexibility analysis of any rule 

subject to notice and comment rulemaking requirements under the Administrative Procedure Act 

or any other statute unless the agency certifies that the rule will not have a significant economic 

impact on a substantial number of small entities. Pursuant to this requirement, we have prepared 

an IRFA for the proposed rule. Throughout the process of developing the IRFA, we conducted 

outreach and held meetings with representatives from the various small entities that could be 

affected by the rulemaking to gain feedback, including recommendations, on how to reduce the 

impact of the rule on these entities. The small business recommendations stated here reflect the 

comments of the small entity representatives (SERs) and members of the Small Business 

Advocacy Review Panel (SBAR Panel, or ‘the Panel’). 

10.1 Overview of the Regulatory Flexibility Act 

In accordance with section 609(b) of the Regulatory Flexibility Act, we convened an 

SBAR Panel before conducting the IRFA. A summary of the Panel’s recommendations is 

presented in the preamble of this proposed rulemaking. Further, a detailed discussion of the 

Panel’s advice and recommendations is found in the Final Panel Report contained in the docket 

for this proposed rulemaking. 

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 

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 

10-1 
Draft Regulatory Impact Analysis 

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. 

10.2 Need for the Rulemaking and Rulemaking Objectives 

A detailed discussion on the need for and objectives of this proposed rule are located in 

the preamble to the proposed 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 

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 

10-2 
Small-Business Flexibility Analysis 

consumers that could result from the new standards. EPA published the study in March 2006. 

In response to these requirements, today’s action proposes controls on exhaust and 

evaporative emissions from Small SI engines and equipment and Marine SI engines and vessels. 

10.3 Definition and Description of Small Entities 

Small entities include small businesses, small organizations, and small governmental 

jurisdictions. For the purposes of assessing the impacts of the proposed 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 10.3-1); (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 not-forprofit enterprise which is independently owned and operated and is not dominant in its field. 

Table 10.3-1 provides an overview of the primary SBA small business categories potentially 

affected by this regulation. 

Table 10.3-1: 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. 

10.3.1 Small SI Engines and Equipment 

10-3 
Draft Regulatory Impact Analysis 

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 

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. 

10.3.2 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. 

10.4 Summary of Small Entities to Which the Rulemaking Will Apply 

As noted above, for each sector impacted by this proposal, SBA defines small entities by 

10-4 
Small-Business Flexibility Analysis 

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. 

10.4.1 Small SI Engines and Equipment 

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. 

10.4.2 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, Nissan, and Tohatsu. One company that qualifies 

as a small business under the SBA definitions has certified their product as a PWC. This 

company is Surfango who makes a small number of motorized surfboards. 

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 

10-5 
Draft Regulatory Impact Analysis 

(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 

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 15 marine fuel tank manufacturers in the United States that qualify as 

small businesses under the SBA definition. These manufacturers include five rotational molders, 

three 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. Moeller qualifies as a large business because they 

are owned by Moore; however, their rotational molding business is a small part of the company 

and operates similar to the smaller businesses. Other blow-molders are in the same situation 

such as Attwood which is owned by Brunswick. 

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 proposed 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. 

10.5 Related Federal Rules 

For Small SI engines and equipment, the primary federal rules that are related to the rule 

under consideration are EPA Phase 1 rule for Small SI engines (60 FR 34582, July 3, 1995), 

EPA Phase 2 rule for Small SI nonhandheld engines (64 FR 15208, March 30, 2004), and EPA 

Phase 2 rule for Small SI handheld engines (65 FR 24268, April 25, 2000). For Marine SI 

engines and vessels, the primary federal rule that is related to the rule under consideration is 

EPA October 1996 final rule (61 FR 52088, October 4, 1996). 

Three other federal agencies have regulations that relate to the equipment and vessels 

under consideration. These agencies are the Consumer Product Safety Commission (CPSC), 

10-6 
Small-Business Flexibility Analysis 

United States Department of Agriculture (USDA), and the United States Coast Guard (USCG). 

CPSC has safety requirements that apply to walk-behind lawnmowers to protect operators of 

such equipment. USDA has design requirements intended to reduce the potential fire threat of 

Small SI equipment. The USCG has safety regulations for marine engine and fuel system 

designs. The USCG safety regulations include standards for exhaust system temperature, fuel 

tank durability, and hose designs, including specific requirements related to system survivability 

in a fire. Manufacturers will need to consider both EPA and other federal standards when 

certifying their products. 

10.6 Projected Reporting, Recordkeeping, and Other 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 considering for manufacturers subject to this proposal may 

include testing, reporting, and record keeping requirements for manufacturers of engines, 

equipment, and vessels, and may 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 

proposing to continue 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 proposing to apply similar reporting, record keeping, and 

compliance requirements to those for OB/PWC engine manufacturers. Testing requirements for 

engine manufacturers would include certification emission (including deterioration factor) 

testing and production line testing. Reporting requirements would include emission test data and 

technical data on the engines. Manufacturers would also need to keep records of this 

information. 

Because of the proposed evaporative emission requirements, there would be new 

reporting, record keeping and compliance requirements for Small SI equipment manufacturers. 

Small SI equipment manufacturers participating in the proposed transition program would 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 

could include certification emission testing. Reporting requirements could include emission test 

data and technical data on the designs. Manufacturers would also need to keep records of this 

information. 

10.7 Regulatory Alternatives 

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Draft Regulatory Impact Analysis 

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 are 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 include 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 are focused mainly on the impacts, and ways to mitigate adverse impacts, 

on small businesses. A summary of the Panel’s recommendations, along with those provisions 

that we are actually proposing in this action, are detailed below. A full discussion of the 

regulatory alternatives and hardship provisions discussed and recommended by the Panel, all 

written comments received from SERs, and summaries of the two outreach meetings that were 

held with the SERs can be found in the SBREFA Final Panel Report.1 In addition, all of the 

flexibilities that are being proposed in the rulemaking for small businesses, as well as those for 

all entities that may be affected by the rulemaking, are described in the preamble to the proposed 

rule. 

10.7.1 Small SI Exhaust Emission Standards 

Described below are the flexibility options recommended by the Panel and our proposed 

regulatory alternatives related to the Small SI nonhandheld engine exhaust emission standards. 

10.7.1.1 Regulatory Flexibility Options for Nonhandheld Engine Manufacturers 

10.7.1.1.1 SBAR Panel Recommendations 

Additional Lead Time for Nonhandheld Engine Manufacturers - The Panel 

recommended that EPA propose two additional years of lead time before the Phase 3 standards 

take effect for small business engine manufacturers. For Class I engines, the effective date for 

small business engine manufacturers would be 2014. For Class II engines, the effective date for 

small business engine manufacturers would be 2013. 

Assigned Deterioration Factors - The Panel recommended EPA propose that small 

business engine manufacturers be allowed the option to use EPA-developed assigned 

deterioration factors in demonstrating compliance with the Phase 3 exhaust emission standards. 

Production Line Testing Exemption - The Panel recommended EPA propose that small 

business engine manufacturers be exempted from the production line testing requirements for the 

Phase 3 exhaust emission standards. 

Broader Definition of Engine Family - The Panel recommended that EPA propose 

allowing small business engine manufacturers to group all of their Small SI engines into a single 

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Small-Business Flexibility Analysis 

engine family for certification by engine class and useful life category, subject to good 

engineering judgment. 

Eligibility for the Small Business Flexibilities - For purposes of determining which 

engine manufacturers are eligible for the small business flexibilities described above, EPA is 

proposing criteria based on a production cut-off of 10,000 nonhandheld engines per year for 

engine manufacturers. The Panel recommended that EPA propose to allow engine 

manufacturers which exceed the production cut-off levels noted above but meet the SBA 

definitions for a small business (i.e., fewer than 1,000 employees for engine manufacturers), to 

request treatment as a small business. 

10.7.1.1.2 EPA’s Proposed Regulatory Flexibility Options 

In general, we have chosen to propose the Panel’s recommended regulatory flexibility 

provisions. The following is a discussion of the proposed provisions. 

Additional Lead Time for Nonhandheld Engine Manufacturers - We are proposing that 

small-volume engine manufacturers could delay implementation of the Phase 3 exhaust emission 

standards for two years (see §1045.145). Small-volume engine manufacturers would 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, we propose that 

manufacturers would be able to apply this delay to all their nonhandheld engines or to just a 

portion of their production. They could 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 - We are proposing that small-volume engine 

manufacturers may 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 proposing 

actual levels for the assigned deterioration factors with this proposal. 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 would provide guidance to engine manufacturers specifying the levels of 

the assigned deterioration factors for small-volume engine manufacturers. 

Production Line Testing Exemption - We are proposing that small-volume engine 

manufacturers would be exempt from the production-line testing requirements (see §1054.301). 

While we are proposing to exempt small volume engine manufacturers from production line 

testing, we believe requiring limited production-line testing could be beneficial to remind 

manufacturers they have an ongoing obligation to assure production engines are complying with 

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Draft Regulatory Impact Analysis 

the standards. Therefore, we request comment on the alternative of applying limited productionline testing to small volume engine manufacturers with a requirement to test one production 

engine per year. 

Broader Definition of Engine Family - We are proposing that small-volume engine 

manufacturers may use a broader definition of engine family 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. We are proposing to 

allow small-volume engine manufacturers to group all of their Small SI 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 proposing to retain the current 

criteria (i.e., 10,000 units per year of nonhandheld engines) for determining who is a smallvolume 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 below, EPA 

is also proposing to allow engine manufacturers which exceed the production cut-off level noted 

above 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. 

10.7.1.2 Regulatory Flexibility Options for Nonhandheld Equipment Manufacturers 

10.7.1.2.1 SBAR Panel Recommendations 

Additional Lead Time for Small SI Equipment Manufacturers - The Panel 

recommended that EPA propose a transition program that would allow small business equipment 

manufacturers to continue using Phase 2 engine designs (i.e., engines meeting the Phase 2 

exhaust emission standards) during the first two years that the Phase 3 standards take effect. 

(For equipment using Class I engines, the provision would apply in 2012 and 2013. For 

equipment using Class II engines, the provision would apply in 2011 and 2012.) The Panel also 

recommended that EPA propose to allow small business equipment manufacturers to use Phase 3 

engines without the catalyst during this initial two year period, provided the engine manufacturer 

has demonstrated that the engine without the catalyst would comply with the Phase 2 exhaust 

emission standards and labels it appropriately. 

Simplified Engine Certification for Equipment Manufacturers - Generally, it has been 

engine manufacturers who certify with EPA for the exhaust emission standards, where the 

standards are engine standards. However, a number of equipment manufacturers, especially 

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Small-Business Flexibility Analysis 

those that make low-volume models, believe it may be necessary for equipment manufacturers 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. The Panel recommended that 

EPA propose a simplified engine certification process for small business equipment 

manufacturers in such situations. Under such a simplified certification process, the equipment 

manufacturer would 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 deterioration data generated by the engine manufacturer would be representative 

for the equipment manufacturer’s configuration. 

Eligibility for the Small Business Flexibilities - For purposes of determining which 

equipment manufacturers are eligible for the small business flexibilities described above, EPA is 

proposing criteria based on a production cut-off of 5,000 pieces of nonhandheld equipment per 

year for equipment manufacturers. The Panel recommended that EPA propose to allow 

equipment manufacturers which exceed the production cut-off levels noted above but meet the 

SBA definitions for a small business (i.e., fewer than 500 employees for most types of equipment 

manufacturers), to request treatment as a small business. 

10.7.1.2.2 EPA’s Proposed Regulatory Flexibility Options 

In general, we have chosen to propose the Panel’s recommended regulatory flexibility 

provisions. The following is a discussion of the proposed provisions. 

Additional Lead Time for Small SI Equipment Manufacturers - We are proposing that 

small-volume equipment manufacturers would 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 could 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 proposing 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 proposing that small-volume manufacturers may 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 could 

potentially use Phase 2 engines on all their Class II equipment for two years (consistent with the 

SBAR Panel’s recommendation) or they might, for example, sell half their Class II equipment 

with Phase 2 engines for four years. 

Simplified Engine Certification for Equipment Manufacturers - We are proposing a 

simplified engine certification procedure for small-volume equipment manufacturers. (As 

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Draft Regulatory Impact Analysis 

discussed in Section V.E.4 of the preamble, we are also proposing 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 proposing a simplified engine certification process for 

small-volume equipment manufacturers (see §1054.612). Under such a simplified certification 

process, the equipment manufacturer would 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 would be representative for the equipment manufacturer’s configuration. 

Eligibility for the Small Business Flexibilities - EPA is proposing to retain the current 

criteria (i.e., 5,000 units per year of nonhandheld equipment) for determining who is a smallvolume equipment manufacturer and, as a result, eligible for the Phase 3 flexibilities described 

above (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 

employee-based definition. However to ensure all small businesses that meet SBA’s employeebased definition have access to the flexibilities described below, EPA is also proposing to 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 would 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 flexibility options recommended by the Panel and our proposed 

regulatory alternatives related to the exhaust emission standards for marine SD/I engine 

manufacturers. 

10.7.2.1 SBAR Panel Recommendations 

Additional Lead Time for SD/I Engine Manufacturers - The Panel recommended that 

EPA propose an implementation date of 2011 for #373 kW SD/I engines produced by small 

business marine engine manufacturers and an implementation date of 2013 for small business 

manufacturers of high performance (>373 kW) SD/I marine engines. Based on the proposed 

2009 implementation date for the remaining SD/I engine manufacturers (i.e., the large 

businesses), these dates would provide small business SD/I engine manufacturers with 2 years 

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Small-Business Flexibility Analysis 

additional lead time for #373 kW SD/I engines and 4 years additional lead time for >373 kW 

SD/I engines. 

Exhaust Emission ABT - EPA is proposing an averaging, banking and trading (ABT) 

program for the SD/I engine standards. Because EPA is proposing an ABT program for SD/I 

engines, the Panel recommended that EPA request comment on the desirability of credit trading 

between high performance and other SD/I marine engines and the impact it could have on small 

business. 

Early Credit Generation for ABT - EPA is proposing an early banking program for SD/I 

marine engines. Under the early banking provisions, manufacturers can generate “bonus” credits 

for the early introduction of engines meeting the proposed emission standards. The Panel 

supports EPA proposing an early banking program and believes that bonus credits will provide 

greater incentive for more small business engine manufacturers to introduce advanced 

technology earlier than would otherwise occur. 

Assigned Emission Rates for High Performance (>373 kW) SD/I Engines - The Panel 

recommended that EPA propose to allow the use of default emission rates that could be used by 

small business high performance SD/I engine manufacturers as part of their certification. Based 

on currently available test data, the proposed default baseline emission levels for high 

performance engines are 30 g/kW-hr HC+NOx and 350 g/kW-hr CO. 

Alternative Standards for High Performance (>373 kW) SD/I Engines - SERs 

expressed concern that that catalysts have not been demonstrated on high performance engines 

and that they may not be practicable for this application. While EPA is proposing a standard 

based on the use of catalysts, EPA is requesting comment on a standard for high performance 

SD/I marine engines that could be met without the use of a catalyst. (Based on available data, 

levels of 16 g/kW-hr HC+NOx and 350 g/kW-hr CO were discussed with the SERs). The Panel 

recommended EPA request comment on a non-catalyst based standard for high performance 

marine engines. 

EPA is proposing to not apply the not-to-exceed (NTE) standards to high performance 

SD/I engines. The Panel supports excluding high performance SD/I engines from NTE 

requirements. 

Broad Engine Families for High Performance (>373 kW) SD/I Engines - The Panel 

recommended that EPA propose allowing small businesses to group all of their high performance 

SD/I engines into a single engine family for certification, subject to good engineering judgment. 

Simplified Test Procedures for High Performance (>373 kW) SD/I Engines - For high 

performance SD/I engines, it may be difficult to hold the engine at idle or high power within the 

tolerances currently specified in existing EPA test procedures. The Panel recommended that 

EPA propose less restrictive specifications and tolerances for small businesses testing high 

performance SD/I engines, which would allow the use of portable emission measurement 

equipment. 

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Draft Regulatory Impact Analysis 

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, EPA is proposing criteria based on a production cut-off of 5,000 SD/I 

engines per year. The Panel recommended EPA propose to allow engine manufacturers that 

exceed the production cut-off level noted above but meet the SBA definitions for a small 

business (i.e., fewer than 1,000 employees for engine manufacturers), to request treatment as a 

small business. 

10.7.2.2 EPA’s Proposed Regulatory Flexibility Options 

In general, we have chosen to propose the Panel’s recommended regulatory flexibility 

provisions. The following is a discussion of the proposed provisions. 

Additional Lead Time for SD/I Engine Manufacturers - One small business marine 

engine manufacturer is already using catalytic converters on some of its #373 kW production 

SD/I marine engines. These engines have been certified to meet standards adopted by CARB 

that are roughly equivalent to the proposed standards. However, other small businesses 

producing SD/I engines have stated that they are not as far along in their catalyst development 

efforts. These manufacturers support the concept of receiving additional time for compliance, 

beyond the implementation date for large manufacturers. For these reasons, EPA is proposing 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). 

Exhaust Emission ABT - We are proposing an averaging, banking, and trading (ABT) 

credit program for exhaust emissions from SD/I marine engines (see part 1045, subpart H). 

Small businesses expressed some concern that ABT could give a competitive advantage to large 

businesses. Specifically, there was an equity concern that if credits generated by traditional 

(#373 kW) SD/I engines could be used for high-performance SD/I engines, that one large 

manufacturer could use these credits to meet the high-performance SD/I engine standards 

without making any changes to their engines. In response, EPA is requesting comment on the 

desirability of credit trading between high-performance and other SD/I marine engines and the 

impact it could have on small business. 

Early Credit Generation for ABT - We are proposing 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, would give small-volume SD/I engine 

manufacturers ample opportunity to bank emission credits prior to the proposed implementation 

date of the standards and provide greater incentive for more small business engine manufacturers 

to introduce advanced technology earlier than would otherwise occur. 

Assigned Emission Rates for High Performance (>373 kW) SD/I Engines - We are 

proposing assigned baseline HC+NOx and CO emission rates for all high-performance SD/I 

engines. These assigned emission rates are based on test data presented in Chapter 4 of the draft 

RIA. We are also proposing assigned deterioration factors for small-volume high-performance 

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Small-Business Flexibility Analysis 

SD/I manufacturers. (See §1045.240.) 

Alternative Standards for High Performance (>373 kW) SD/I Engines - Small 

businesses expressed concern that that catalysts have not been demonstrated on highperformance engines and that they may not be practicable for this application. In addition, the 

concern was expressed that emission credits may not be available at a reasonable price. In 

response, we are requesting comment on the need for and level of alternative standards for highperformance marine engines. Also, we are not proposing to apply NTE standards to highperformance SD/I engines (See §1045.105). 

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 proposing to allow small businesses to 

group all of their high performance SD/I engines into a single engine family for certification, 

subject to good engineering judgment (see §1045.230). 

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 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 proposing less restrictive specifications and 

tolerances, for small businesses testing high performance SD/I engines, which would allow the 

use of portable emission measurement equipment (see §1065.901(b)). This would facilitate less 

expensive testing for these small businesses without having a negative effect on the environment. 

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 proposing criteria based on a production cut-off of 5,000 SD/I 

engines per year. Under this approach, we would allow engine manufacturers that exceed the 

production cut-off level noted above to request treatment as a small business if they have fewer 

than the number of employees specified above under the SBA definition of small business. In 

such a case, the manufacturer would need to provide information to EPA demonstrating that the 

manufacturer has fewer employees than the applicable employee cut-off level established by 

SBA. 

10.7.3 Small SI and Marine SI Evaporative Emission Standards— Flexibility Alternatives 

for Equipment, Vessel, and Fuel Tank Manufacturers 

Described below are the flexibility options recommended by the Panel and our proposed 

regulatory alternatives related to the evaporative emission standards for Small SI engines and 

equipment and Marine SI engines and vessels. SERs raised many of the same issues regarding 

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Draft Regulatory Impact Analysis 

evaporative emission standards for both Small SI and marine applications. In fact, many of the 

SERs supply fuel system components to both industries. For these reasons, the Panel’s 

recommendations on regulatory flexibility discussed below would apply 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 details of the evaporative emissions 

program under consideration and the flexibility provisions shared by EPA with the SERs were 

noted as being available to all fuel tank manufacturers. Therefore, EPA is proposing the Panel 

recommendations on regulatory flexibility discussed below for small business fuel tank 

manufacturers for all fuel tank manufacturers. 

10.7.3.1 SBAR Panel Recommendations 

Consideration of Appropriate Lead Time - The Panel recommended that EPA propose to 

implement the fuel tank permeation standards in 2011 with an additional year (2012) for 

rotationally-molded marine fuel tanks. The extra year for rotational-molded marine tanks would 

give manufacturers time to address issues that are specific to the marine industry. 

With regard to diurnal emissions control, SERs commented that they would like 

additional time to install carbon canisters in their vessels because of deck and hull changes that 

might be needed to accommodate the carbon canisters. SERs commented that they would 

consider asking EPA to allow the use of low permeation fuel hose prior to 2009 as a method of 

creating an emission neutral flexibility option for providing extra time for canisters. The Panel 

recommended that EPA continue discussions with the marine industry and request comment on 

environmentally neutral approaches to provide more flexibility in meeting the potential diurnal 

emission standards. 

Fuel Tank ABT and Early Incentive Program - The Panel recommended that EPA 

propose an ABT program for fuel tank permeation. The Panel also recommended that EPA 

request comment on including service tanks (i.e., replacement tanks) in the ABT program. 

Finally, the Panel recommended that EPA request comment and on an early incentive program 

for tank permeation. 

Broad Definition of Evaporative Emission Family for Fuel Tanks - The Panel 

recommended that EPA propose a broad emission family definition for Small SI fuel tanks and 

for marine fuel tanks similar to that in the regulations for recreational vehicles. Under the 

recreation vehicle evaporative emission regulations, EPA specifies that fuel tank permeation 

emission families be based on type of material (including additives such as pigments, 

plasticizers, and ultraviolet (UV) inhibitors), emission-control strategy, and production methods. 

Fuel tanks of different sizes, shapes, and wall thicknesses may be grouped into the same 

emission family. 

Compliance Progress Review for Marine Fuel Tanks - While there is clearly a 

difference of opinion among the SERs involved in tank manufacturing, some SERs expressed 

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Small-Business Flexibility Analysis 

concern that there is not an established low permeation technology available for rotationallymolded marine fuel tanks. These SERs stated that they are working on developing such 

technology, but do not have in-use experience to demonstrate the durability of low-permeation 

rotationally molded fuel tanks. The Panel recommended that if a rule is implemented, EPA 

undertake a “compliance progress review” assessment with the manufacturers. In this effort, 

EPA should continue to engage on a technical level with rotationally-molded marine fuel tank 

manufacturers and material suppliers to assess the progress of low permeation fuel tank 

development and compliance. 

Design-Based Certification - The Panel recommended that EPA propose a design-based 

certification for carbon canisters and fuel tanks. For the carbon canisters, the design requirement 

would 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. The different canister 

sizes are intended to account for the difference between boats normally trailered to the water for 

use versus boats normally stored in the water between uses. For fuel tanks, the Panel 

recommended that EPA propose to allow design-based certification for metal tanks and plastic 

fuel tanks with a continuous EVOH barrier. 

SERs commented that 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 membership in the National Marine Manufacturers Association 

(NMMA). NMMA is working to update these recommended practices to include carbon canister 

installation specifications and a low-permeation hose designation. The Panel recommended that 

EPA propose to accept data used for meeting the voluntary requirements as part of the EPA 

certification. 

Additional Lead Time for Small SI Fuel Hose Requirement - EPA is proposing to apply 

the fuel hose permeation requirements beginning with the 2008 model year for Small SI 

nonhandheld equipment. Given the short lead time before 2008, small business equipment 

manufacturers may not be ready for such a requirement. The Panel recommended EPA propose 

a 2009 implementation date for low permeation fuel hose for small business equipment 

manufacturers producing Small SI nonhandheld equipment. 

10.7.3.2 EPA’s Proposed Regulatory Flexibility Options 

In general, we have chosen to propose the Panel’s recommended regulatory flexibility 

provisions. The following is a discussion of the proposed provisions. 

Consideration of Appropriate Lead Time - Consistent with the Panel recommendations, 

we are proposing to implement the tank permeation standards in 2011 with an additional year 

(2012) for rotational-molded marine fuel tanks (see §1054.110 and §1045.107). With regard to 

the proposed diurnal emission control requirements, we are requesting comment on 

environmentally neutral approaches to provide more flexibility in meeting the potential diurnal 

emission standards. 

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Draft Regulatory Impact Analysis 

Fuel Tank ABT and Early Incentive Program - Consistent with the Panel 

recommendations, we are proposing an ABT program for fuel tank permeation and an earlyallowance program for fuel tank permeation. We are requesting comment on including service 

tanks in the ABT program. Service tanks are fuel tanks sold as replacement parts for in-use 

equipment. 

Broad Definition of Evaporative Emission Family for Fuel Tanks - We are proposing 

that permeation emission families be based on type of material (including additives such as 

pigments, plasticizers, and UV inhibitors), emission-control strategy, and production methods. 

Fuel tanks of different sizes, shapes, and wall thicknesses could be grouped into the same 

emission family (see §1045.230 and §1054.230). Manufacturers therefore would 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. Although Small SI and Marine SI 

fuel tanks would not be allowed in the same emission family, it would be possible to carry-across 

certification test data from one category to another. 

Compliance Progress Review for Marine Fuel Tanks - Some major manufacturers of 

rotational-molded marine fuel tanks have expressed concern that they do not have significant inuse experience to demonstrate the durability of low-permeation rotational-molded fuel tanks in 

boats. However, one manufacturer of rotational-molded fuel tanks has stated that they are 

already selling low permeation tanks into the Small SI market and they have plans to sell them 

into marine applications. To address this uncertainty, EPA notes in the preamble for the rule that 

it intends to continue to engage on a technical level with rotational-molded marine fuel tank 

manufacturers and material suppliers to assess the progress of low permeation fuel tank 

development and compliance. If systematic problems are identified across the industry, this 

would give EPA the opportunity to address the problem. If problems were identified only for 

individual businesses, this would give EPA early notice of the issues that may need to be 

addressed through the proposed hardship relief provisions. 

Design-Based Certification - We are proposing design-based certification for carbon 

canisters for boats. For the carbon canisters, the design requirement would 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 proposing design-based 

certification for certain fuel tanks. For fuel tanks, we are proposing to allow design-based 

certification for metal tanks as well as plastic fuel tanks with a continuous EVOH barrier. With 

regard to the Panel recommendation that EPA accept data for its certification program that is 

used for meeting industry recommended practices (such as those recommended by NMMA, 

ABYC and SAE), we are proposing that this data could be used as part of EPA certification as 

long as it is collected consistent with the test procedures and other requirements proposed today. 

Additional Lead Time for Small SI Fuel Hose Requirement - We are proposing an 

implementation date of 2008 for Small SI hose permeation standards for non-handheld 

equipment (see §90.127). Consistent with the Panel recommendations, we are proposing a 2009 

implementation date for low permeation fuel hose for small businesses producing Small SI nonhandheld equipment. 

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Small-Business Flexibility Analysis 

10.7.4 Hardship Provisions—Regulatory Flexibility Options for Engine, Equipment, 

Vessel, and Fuel System Component Manufacturers 

The Panel recommended that EPA propose two hardship programs for manufacturers. 

EPA has adopted similar hardship provisions in a number of previous rules. The following 

section summarizes the hardship provisions recommended by the Panel 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). 

10.7.4.1 SBAR Panel Recommendations 

Unusual Circumstances Hardship - The Panel recommended that EPA propose a 

provision allowing for hardship relief under unusual circumstances for manufacturers affected by 

this rule. Manufacturers would be able to apply for hardship relief if circumstances outside their 

control cause the failure to comply and if failure to sell the subject engines or equipment would 

jeopardize the company’s solvency. An example of an unusual circumstance outside a 

manufacturer’s control may be an “Act of God,” a fire at the manufacturing plant, or the 

unforeseen shut down of a supplier with no alternative available. 

Economic Hardship - The Panel recommended that EPA propose economic hardship 

provisions for small businesses affected by this rule. Small manufacturers would be able to 

petition EPA for limited additional lead time to comply with the standards. A manufacturer 

would have to make the case that it has taken all possible business, technical, and economic steps 

to comply, but the burden of compliance costs would have a significant impact on the company’s 

solvency. 

10.7.4.2 EPA’s Proposed Hardship Provisions 

We have chosen to propose the Panel’s recommended regulatory flexibility provisions. 

The following is a discussion of the proposed provisions. 

Unusual Circumstances Hardship - Under the proposed unusual circumstances hardship 

provision, manufacturers would be able to apply for hardship relief if circumstances outside their 

control cause the failure to comply and if failure to sell the subject engines or equipment would 

jeopardize the company’s solvency (see §1068.245). The terms and time frame of the relief 

would depend on the specific circumstances of the company and the situation involved. As part 

of its application for hardship, a company would be required to provide a compliance plan 

detailing when and how it would achieve compliance with the standards. This hardship 

provision would be available to all business engine manufacturers, equipment manufacturers, 

vessel manufacturers, and fuel system component manufacturers, regardless of size. 

Economic Hardship - Under the proposed economic hardship provision, small business 

manufacturers would be able to petition EPA for limited additional lead time to comply with the 

standards (see §1068.250). A manufacturer would have to make the case that it has taken all 

possible business, technical, and economic steps to comply, but the burden of compliance costs 

10-19 
Draft Regulatory Impact Analysis 

would have a significant impact on the company’s solvency. Hardship relief could include 

requirements for interim emission reductions and/or purchase and use of emission credits. The 

length of the hardship relief would be established during the initial review and would likely need 

to be reviewed annually thereafter. As part of its application for hardship, a company would be 

required to provide a compliance plan detailing when and how it would achieve compliance with 

the standards. This hardship provision would 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 Proposed Rulemaking 

The following section summarizes the economic impact on small businesses of the 

proposed 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 proposed 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 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 proposed standards on small businesses, EPA employed a 

cost-to-sales 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 Draft RIA. A description 

of the inputs used for each affected industry sector 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 OB/PWC engine manufacturers, EPA identified one small business. The one small 

business identified by EPA manufactures their personal watercraft today using four-stroke 

engines with certified emission levels below the proposed standards. As a result, the estimated 

costs for upgrading their engines would not apply. We therefore believe the impact of the rule is 

well below one percent of revenues for this OB/PWC engine manufacturer. 

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 

by less than one percent of annual revenues. 

10-20 
Small-Business Flexibility Analysis 

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 proposed 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, 17 of the small businesses are projected to 

incur compliance costs between one and three percent of their annual revenues. Two small 

businesses that produce >373 kW SD/I engines as part of a broader line of work (such as engine 

testing) will 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 proposed 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 15 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 proposed low permeation fuel hose requirements will not apply to the fill neck), we 

have not included this manufacturer in our analysis. Of the 15 fuel tank manufacturers, EPA has 

estimated that all of them will incur costs below one percent of annual revenues. 

10-21 
Draft Regulatory Impact 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 proposed regulations on small businesses 

impacted by the proposed 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 1 0 0 

Manufacturers of Marine SD/I engines < 373 kW 4 5 0 

Manufacturers of Marine SD/I engines > 373 kW 

(high-performance) 

2 17 0 

Boat Builders >1,000 0 0 

Manufacturers of Fuel Hose and Fuel Tanks for 

Marine SI Vessels 

15 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 363 

+ >1,000 

boat builders 

60 18 

10-22 
Small-Business Flexibility Analysis 

For a complete discussion of the economic impacts of the proposed rulemaking, see 

Chapter 9, the Economic Impact Analysis chapter, of this Draft Regulatory Impact Analysis. 

10-23 
Draft Regulatory Impact 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,” 

EPA memorandum from Phil Carlson to the EPA Docket, March 6, 2007. (Docket Identification EPA-HQ-OAR2004-0008-0547.) 

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.) 

10-24 
Regulatory Alternatives 

CHAPTER 11: Regulatory Alternatives 

Our proposed 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 proposed 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 

proposal, unless otherwise specified. For example, the more stringent recreational marine 

exhaust standards for OB/PWC are evaluated as follow-on requirements to the proposed 

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 proposal, 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 

proposal. Options that do not merit further consideration are eliminated and those that warrant 

additional analysis in subsequent sections are identified. 

11-1 
Draft 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, proposing a less stringent HC + NOx emission standard for 

Class I spark-ignition engines. The proposed standard of 10 g/kW-hr is readily achievable with 

reasonably priced emission control technology. Furthermore, the lead time for implementing the 

proposed 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 proposal. 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 proposal. Cooling for the slightly more active OHV catalyst would be 

supplied by the engine improvements included in the proposal, 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 proposal. However, for the same reasons previously stated for Class I 

engines, we rejected this alternative from further consideration; the proposal is 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 proposed 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 proposal. It also provides four more years of lead time; a phase-in could be 

needed since implementation would require the equipment manufacturers involvement for nonintegrated 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 threeway 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 proposed standards for marine auxiliary engines include a CO standard that would 

require the use of highly efficient catalytic control. This proposed 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 we are proposing 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 proposed standards for OB/PWC are based on technology that manufacturers are 

already certifying and selling nationwide. To meet the proposed requirements, manufacturers 

would continue to sell this technology and discontinue their sale of high-emitting old technology 

carbureted two-stroke engines. Because the proposed standards can be met with existing 

technology, we do not believe that there is an alternative between the proposed 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 a set of follow-on standards to those 

proposed. We analyzed these as 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 adjusted the proposed 

standard equation to 28 - 0.45 × rated power(kW) to maintain a continuous curve function. This 

alternative also considered 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 

11-3 
Draft Regulatory Impact Analysis 

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 and emission reductions that 

could be achieved through the combined use of calibrated four-stroke 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 proposed 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 2009 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 than 

we are proposing. Many of the SD/I marine engines with catalysts described in Chapter 4 had 

HC+NOx emission rates in the 3-4 g/kW-hr range, even with deteriorated catalysts. In the 

development testing for this proposed 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 

proposed 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 considered a less stringent alternative 

11-4 
Regulatory Alternatives 

based on engine fuel system upgrades, calibration, or other minor changes such as an air 

injection pump rather than catalytic control. These less stringent standards were modeled for the 

2009 model year. Manufacturers expressed concern that catalysts may not be practical for these 

engines due to the high exhaust flow rates, high emission rates, and low useful life period 

between rebuild. For analytical purposes, we selected an alternative standard of 22 g/kW-hr 

HC+NOx and 350 g/kW-hr CO, but lower levels in the range of 15-20g/kW-hr HC+NOx and 

300g/kW-hr CO may be achievable with the engine modifications identified above. For these 

engines, we did not consider a more stringent alternative. 

11.1.2 Alternative Evaporative Emission Requirements 

11.1.2.1 Small SI Engines 

For Small SI engines, we are proposing both permeation and venting emission standards. 

The proposed permeation standards are for fuel tanks and fuel lines. We believe that the 

proposed 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 non-handheld Small SI engines (i.e., Classes I and II), we are 

proposing standards for running loss and diffusion emissions, but not for diurnal emissions. We 

are not proposing any type of venting emissions control for handheld equipment. 

For a less stringent alternative, we considered not requiring venting emission control 

(running loss and diffusion emissions) for non-handheld Small SI engines. These requirements 

would be deleted from the proposal and thus modeled as being deleted in the years otherwise 

required in the proposal. 

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 proposed venting emission 

standards. For marine vessels, we proposed diurnal emission standards for all vessel types. For 

portable fuel tanks and PWC fuel tanks, the anticipated technology of a sealed system with 

pressure relief is fairly straightforward and commonly used today. However, we anticipate that 

the proposed 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 in 2010.1

 For a more stringent scenario, 

1

Note that PWC already meet the proposed 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 
Draft Regulatory Impact Analysis 

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 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 Proposal 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 proposed 

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 proposed 

3 OB/PWC < 40kW 

C Decreases with power 

output (P) 

C HC+NOx g/kW-hr 

equation is 28-0.3P 

C CO g/kW-hr equation 

is 500-5P

 > 40kW 

C 16 g/kW-hr HC+NOx 

C 300 g/kW-hr CO 

C Both begin 2009 

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 2009 

standards 

4 SD/I 

<373 kW 

C 5 g/kW-hr HC+NOx 

C 75 g/kW-hr CO 

C Begins 2009a 

less C 10 g/kW-hr HC+NOx 

C 150 g/kW-hr CO 

C Same effective dates as proposal 

5 more C 2.5 g/kW-hr HC+NOx 

C 75 g/kW-hr CO 

C Begins 2012 in lieu of proposed standardsa 

6 SD/I 

$373 kW 

C 5 g/kW-hr HC+NOx 

C 350 g/kW-hr CO 

C Begins 2009a 

less C 22 g/kW-hr HC+NOx 

C 350 g/kW-hr CO 

C Begins 2009 a

 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 Proposal less/ 

more 

Alternative Description 

Evap 7 HH 

diurnal/ 

running 

loss 

C None more C Begins 2012 

8 Class I 

& Class 

II 

diffusion 

& 

running 

loss 

C 0.8 g/day HC 

diffusion standard 

C Running loss is a 

“zero emission” design 

standard 

C Class I begins 2012 

and Class II begins 

2011 

less C No running loss and no diffusion 

9 Class I C None more C Requirement would begin in 2012 for Class 

& Class I and 2011 for Class II 

II diurnal 

10 Installed 

marine 

fuel tank 

diurnal 

C 0.4g/gal/day HC 

trailerable boat 

C 0.16 g/gal/day HC 

non-trailerable boat 

C Begins 2010 

less C No diurnal for 2010 

11 more C More stringent test procedure. If charcoal 

canister is used, active purge required. 

C Would begin 2010 

12 Portable C Diurnal is a “zero less C No diurnal 

marine 

fuel tank 

emission” design 

standard 

diurnal C Begins 2012 

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 

proposed 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 proposal. The only 

exception to this is the second phase of OB/PWC standards where costs are incremental to the 

proposal. 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 

11-7 
Draft Regulatory Impact Analysis 

(NPV) for a 30-year period beginning in 2008. The NPV estimates are based on a seven 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 proposed standards. For current SV engines they would need 

to utilize larger and more active catalysts than considered in the analysis for the proposed 

standards, or convert to OHV design and use a slightly larger catalyst or more active catalyst 

than for the proposed 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 

11-8 
Regulatory Alternatives 

closed loop fuel injection design is estimated at $103,000 per engine family. Increased catalyst 

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) 

Proposed 

Class I 

Class II 

$11-$23 

$39-$86 

$9-$15 

$27-$45 

More Stringent

 Class I

 Class II 

$18-$23 

$121-$153 

$16-$17 

$79-$97 

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 
Draft 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) 

Proposed OB

 PWC 

$284 

$359 

$219 

$272 

More Stringent OB

 PWC 

$369 

$518 

$256 

$389 

Incremental Costa OB

 PWC 

$85 

$159 

$37 

$117 

a

 Incremental cost is presented here because the more stringent alternative for OB/PWC 

includes the primary standard in 2009 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.

 Engines greater than 373 kW were modeled to meet the less stringent alternative 

standard through engine calibration and increased use of electronic fuel injection (from 50 

percent use to 75 percent use). This increased fuel injection use is intended to account for some 

carbureted engines that would not be able to meet the standard while acknowledging the data in 

Chapter 4 suggesting that some carbureted engines would be able to meet this alternative 

standard. using calibration changes or other engine modifications. 

For the more stringent case, we consider a larger catalyst size with a higher precious 

metal loading for engines less than 373 kW and no change from the primary catalyst alternative 

for engines greater than 373 kW. 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 the three scenarios because, in each case, all engines 

are anticipated to use electronic fuel injection. To reiterate, we did not include a more stringent 

standard for high performance SD/I engines. Table 11.2-3 compares the per-engine cost 

estimates for the primary, less stringent, and more stringent alternatives. 

11-10 
Regulatory Alternatives 

Table 11.2-3: SD/I Per-Engine Cost Estimates (Without Fuel Savings) 

Sales Weighted Averages 

Short Term (years 1-5) Long Term (years 6-10) 

Proposed <373 kW 

$373 kW 

$360 

$920 

$272 

$672 

Less Stringent <373 

kW 

$373 kW 

$216 

$284 

$160 

$155 

More Stringent <373 kW 

$373 kW 

$435 

$920a 

$337 

$672a 

a

 There is no more stringent option for these engines. Costs shown are for the proposal and are 

used later to develop aggregate values for the combination of more stringent marine options 

later in this section. 

11-11 
Draft Regulatory Impact Analysis 

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 and diffusion 

controls for non-handheld equipment. For the more stringent case, we add the incremental costs 

of diurnal emission control for all nonhandheld engines and diurnal emission control, diffusion 

control, and running losses 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) 

Proposed Aggregate

 Handheld

 Class I

 Class II 

$3.36 

$0.82a 

$3.16 

$6.90 

$2.54 

$0.69a 

$2.29 

$5.30 

Less Stringent 

Aggregate

 Handheld

 Class I

 Class II 

$1.82 

$0.82a 

$1.11 

$4.40 

$1.31 

$0.69a 

$0.65 

$3.30 

More Stringent Aggregate

 Handheld

 Class I

 Class II 

$7.24 

$4.40 

$6.12 

$11.25 

$5.64 

$3.55 

$4.66 

$8.78 

a

 Values reflect the proposed permeation standards. These costs are used in the alternative 

analysis only to develop aggregate values for comparison purposes. 

11-12 
Regulatory Alternatives 

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 

Proposed Aggregate

 Handheld

 Class I

 Class II 

1.4 

0.2a 

0.8 

4.7 

$2.34

 $0.32a 

$1.39 

$7.24 

$2.18

 $0.31a 

$1.32 

$5.98 

Less Stringent 

Aggregate

 Handheld

 Class I

 Class II 

0.9 

0.2a 

0.5 

3.0 

$1.51

 $0.32a 

$0.89 

$4.60 

$1.41

 $0.31a 

$0.85 

$3.80 

More Stringent Aggregate

 Handheld

 Class I

 Class II 

1.5 

0.3 

0.9 

5.3 

$2.61 

$0.46 

$1.50 

$8.12 

$2.42 

$0.46 

$1.43 

$6.70 

a

 Values reflect the proposed permeation standards. These costs are used in the alternative 

analysis only to develop aggregate values for comparison purposes. 

11-13 
Draft Regulatory Impact Analysis 

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) 

Proposed Aggregate

 portable

 PWC

 installed 

$55 

$12a 

$17a 

$74 

$36 

$8a 

$11a 

$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 proposed permeation and diurnal standards. These costs used in the 

alternative analysis only to develop aggregate values for comparison purposes. 

11-14 
Regulatory Alternatives 

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 

Proposed Aggregate

 portable

 PWC

 installed 

31 

15a 

9a 

41 

$45 

$22 

$15 

$59 

$36

 $19a

 $13a 

$45 

Less Stringent 

Aggregate

 portable

 PWC

 installed 

22 

12 

9a 

28 

$33 

$18 

$15 

$41 

$26 

$15

 $13a 

$32 

More Stringent Aggregate

 portable

 PWC

 installed 

32 

15a 

9a 

43 

$47 

$23 

$15 

$62 

$37

 $19a

 $13a 

$47 

a

 Values reflect the proposed permeation and diurnal standards. These costs used in the 

alternative analysis only to develop aggregate values for comparison purposes. 

11-15 
Draft Regulatory Impact Analysis 

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 Proposal Scenario Alternative 

Exhaust 1 Class I $11-$23 more $18-$23 

2 Class II $39-$86 more $121-$153 

3a OB/PWC $­ more $70 

4 SD/I <373 kW $360 less $216 

5 more $435 

6 SD/I $373 kW $920 less $284 

Evap 7b HH $­ more $3.58 

8 Class I & Class II $4.41 less $2.19 

9b Class I & Class II $­ more $3.45 

10 Installed marine fuel 

tank 

$74 less $42 

11 more $94 

12 Portable marine fuel tank $12 less $11 

a

 Costs are presented incremental to the proposal for OB/PWC because, for this alternative, a 

second stage of standards is considered in 2012 beyond the 2009 proposal. 

b

 Only considers standards for venting emission control which are not in the proposal. The 

venting emission standards considered here are diurnal for Class I and Class II and 

diurnal/running loss/diffusion for handheld. 

Table 11.2-9 summarizes the 30-year net present value for costs for the proposal 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. 

11-16 
Regulatory Alternatives 

Table 11.2-9: 30-Year Net Present Value Cost Summary for Alternative Small SI 

Program Options with a 7 Percent Discount Rate (Million 2005$) 

Source Alt Target Proposal Scenario Alternative 

Exhaust 1 Class I $1225 more $1499 

2 Class II $2080 more $4360 

3a OB/PWC $­ more $297 

4 SD/I <373 kW $396 less $239 

5 more $391 

6 SD/I $373 kW $11 less $3 

Evap 7b HH $­ more $319 

8 Class I & Class II $829 less $382 

9b Class I & Class II $­ more $570 

10 Installed marine fuel 

tank 

$291 less $166 

11 more $361 

12 Portable marine fuel tank $17 less $16 

a

 Costs are presented incremental to the proposal for OB/PWC because, for this alternative, a 

second stage of standards is considered in 2012 beyond the 2009 proposal. 

b

 Only considers standards for venting emission control which are not in the proposal. The 

venting emission standards considered here are diurnal for Class I and Class II and 

diurnal/running loss/diffusion for handheld. 

Table 11.2-10: 30-Year Net Present Value Cost Summary for Alternative Small SI 

Program Options with a 3 Percent Discount Rate (Million 2005$) 

Source Alt Target Proposal Scenario Alternative 

Exhaust 1 Class I $2,105 more $2,770 

2 Class II $3,387 more $7,910 

3a OB/PWC $­ more $465 

4 SD/I <373 kW $596 less $359 

5 more $638 

6 SD/I $373 kW $16 less $4 

Evap 7b HH $­ more $544 

8 Class I & Class II $1,367 less $617 

9b Class I & Class II $­ more $963 

10 Installed marine fuel 

tank 

$458 less $265 

11 more $567 

12 Portable marine fuel tank $24 less $22 

a

 Costs are presented incremental to the proposal for OB/PWC because, for this alternative, a 

second stage of standards is considered in 2012 beyond the 2009 proposal. 

b

 Only considers standards for venting emission control which are not in the proposal. The 

venting emission standards considered here are diurnal for Class I and Class II and 

11-17 
Draft Regulatory Impact Analysis 

diurnal/running loss/diffusion for handheld. 

11.3 Emission Reduction 

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 proposal. 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 Small SI
 

Program Options with a 7 Percent Discount Rate (Million Tons)
 

Source Alt Target Proposal Scenario Alternative 

Exhaust 1 Class I 0.78 more 0.67 

2 Class II 1.01 more 1.26 

3a OB/PWC 0 more 0.23 

4 SD/I <373 kW 0.33 less 0.21 

5 more 0.30 

6 SD/I $373 kW 0.004 less 0.002 

Evap 7b HH 0 more 0.04 

8 Class I & Class II 1.02 less 0.60 

9b Class I & Class II 0 more 0.12 

10 Installed marine fuel 

tank 

0.40 less 0.28 

11 more 0.42 

12 Portable marine fuel tank 0.08 less 0.06 a

 Tons reduced are presented incremental to the proposal for OB/PWC because, for this 

alternative, a second stage of standards is considered in 2012 beyond the 2009 proposal. 

b

 Only considers standards for venting emission control which are not in the proposal. The 

venting emission standards considered here are diurnal for Class I and Class II and 

diurnal/running loss/diffusion for handheld. 

11-18 
Regulatory Alternatives 

Table 11.3-2: 30-Year Net Present Value 
 

Emission Reduction Summary for Alternative Small SI
 

Program Options with a 3 Percent Discount Rate (Million Tons)
 

Source Alt Target Proposal Scenario Alternative 

Exhaust 1 Class I 1.41 more 1.30 

2 Class II 1.82 more 2.48 

3a OB/PWC 0 more 0.44 

4 SD/I <373 kW 0.61 less 0.38 

5 more 0.58 

6 SD/I $373 kW 0.007 less 0.003 

Evap 7b HH 0 more 0.07 

8 Class I & Class II 1.80 less 1.04 

9b Class I & Class II 0 more 0.21 

10 Installed marine fuel 

tank 

0.76 less 0.53 

11 more 0.78 

12 Portable marine fuel tank 0.14 less 0.12 a

 Tons reduced are presented incremental to the proposal for OB/PWC because, for this 

alternative, a second stage of standards is considered in 2012 beyond the 2009 proposal. 

b

 Only considers standards for venting emission control which are not in the proposal. The 

venting emission standards considered here are diurnal for Class I and Class II and 

diurnal/running loss/diffusion for handheld. 

11-19 
Draft Regulatory Impact Analysis 

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 

proposal. 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 proposal. 

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 Proposal and Alternatives 

Without Fuel Savings, 7 Percent Discount Rate ($/ton) 2005$ 

Source Alt Target Proposal Scenario Alternative 

Exhaust 1 Class I $1585 more $2240 

2 Class II $2055 more $3470 

3a OB/PWC $740 more $1280 

4 SD/I <373 kW $1200 less $1160 

5 more $1330 

6 SD/I $373 kW $2940 less $1920 

Evap 7b HH NA more $8150 

8 Class I & Class II $770 less $640 

9b Class I & Class II NA more $4910 

10 Installed marine fuel 

tank 

$720 less $600 

11 more $870 

12 Portable marine fuel tank $230 less $250 

a

 Cost effectiveness of more stringent alternative is presented incremental to the proposal for 

OB/PWC because, for this alternative, a second stage of standards is considered in 2012 beyond 

the 2009 primary alternative. 

b

 Only considers standards for venting emission control which are not in the proposal. The 

venting emission standards considered here are diurnal for Class I and Class II and 

diurnal/running loss/diffusion for handheld. 

11-20 
Regulatory Alternatives 

Table 11.4-2: Comparison of Cost Effectiveness for Proposal and Alternatives 

Without Fuel Savings, 3 Percent Discount Rate ($/ton) 2005$ 

Source Alt Target Proposal Scenario Alternative 

Exhaust 1 Class I $1,500 more $2,130 

2 Class II $1,860 more $3,180 

3a OB/PWC $630 more $1050 

4 SD/I <373 kW $980 less $950 

5 more $1100 

6 SD/I $373 kW $2370 less $1440 

Evap 7b HH NA more $8150 

8 Class I & Class II $720 less $640 

9b Class I & Class II NA more $4910 

10 Installed marine fuel 

tank 

$600 less $500 

11 more $730 

12 Portable marine fuel tank $180 less $190 

a

 Cost effectiveness of more stringent alternative is presented incremental to the proposal for 

OB/PWC because, for this alternative, a second stage of standards is considered in 2012 beyond 

the 2009 primary alternative. 

b

 Only considers standards for venting emission control which are not in the proposal. The 

venting emission standards considered here are diurnal for Class I and Class II and 

diurnal/running loss/diffusion 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 proposed 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 

proposal. 

11.5.1 Exhaust Emission Standards 

11-21 
Draft Regulatory Impact Analysis 

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 

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 standards we are proposing. 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 proposed standards. For the analytical 

period we considered, the proposal provides more emission reductions than the alternative by 

211,000 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 

44,000 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 4g/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. For the current proposal, we 

are expecting engine manufacturers to meet the standards by applying closed loop EFI on a 

portion of their V-twin 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 standards we are 

proposing. 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 

proposed standards. For the 30 year analytical period we considered, the proposal provides 

fewer overall emission reductions than the alternative, but between 2011 and 2020 the proposal 

gives 177,000 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 proposing 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 

11-22 
Regulatory Alternatives 

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. 

11.5.1.3 Sterndrive/Inboard (SD/I) Engine HC + NOx and CO Emission Standards 

11.5.1.3.1 SD/I <373 kW 

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 proposed 

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. 

11.5.1.3.2 SD/I $373 kW 

This section addresses the alternative of setting less stringent standards for high 

performance SD/I engines. These engines have very high power outputs, large exhaust gas flow 

rates, and relatively high concentrations of hydrocarbons and carbon monoxide in the exhaust 

gases. From a conceptual perspective, the application of catalytic converter technology to these 

engines is feasible. As is the case in similar heavy-duty on-highway gasoline engines, these 

catalytic converters would have to be quite large in volume, perhaps on the order of the same 

volume as the engine displacement, and would involve significant heat rejection issues. 

Manufacturers have expressed concern that catalysts may not be practical for these 

engines due to the high exhaust flow rates and short low useful life periods. We are requesting 

comment on an alternative approach not based on catalysts but based on engine and fuel system 

modifications. This option is less costly and more cost effective than our primary proposal, but 

provides less emission reductions. This alternative remains under active consideration. We 

11-23 
Draft Regulatory Impact Analysis 

intend to continue to work with the marine industry to gather additional data in order to further 

investigate this option. 

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 and diffusion emissions 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. 

Other approaches would be to move the fuel tank away from heat sources or to use heat 

protection such as a shield or directed air flow. Diffusion can be controlled by simply using a 

tortuous tank vent path, which is commonly used today on Small SI equipment to prevent fuel 

splashing or spilling. These emission control technologies are 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 proposing 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 

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. 

11-24 
Regulatory Alternatives 

Carbon canisters have been installed on fourteen boats by industry in a pilot program intended 

to demonstrate the feasibility of this technology. The proposed standards would be 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 

proposed engineering design-based certification. Eliminating these requirements would not 

meaningfully affect the cost effectiveness of the marine evaporative program. Not proposing 

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 proposing these controls would be inconsistent with the requirements of 

section 213 of the Clean Air Act. 

11-25 
Draft 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 considered a standard of 350 g/kW-hr 

HC+NOx. 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 4.05 1.26 4.00 1.03 96.3 1.35 345 

$373 kW 10.1 1.26 6.79 1.03 207 1.35 362 

11A.2 Evaporative Emission Factors 

As discussed above, no changes in the proposed 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. 

11-26 
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 proposal. 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 proposed 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 proposal. 

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 

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Draft 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 0.470 391.13 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 proposed primary 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 proposed 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 proposing 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 proposed 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 

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Regulatory Alternatives 

For SD/I engines greater than 373 kW, we use the same control scenario as for the 

primary alternative. 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 proposed 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 proposed 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. 

11-29 
Draft 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. 

11-30