Final Draft Staff Report with Appendices 

 For Proposed Amendments to Rule 4702 

SAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT 

FINAL DRAFT STAFF REPORT 

Proposed Amendments to Rule 4702 (Internal Combustion Engines) 

August 18, 2011 

Prepared by: Anna Myers, Senior Air Quality Specialist, Plan Development 

 Sandra Lowe-Leseth, Air Quality Engineer, Permits 

Reviewed by: Brian Clements, Senior Air Quality Engineer, Permits 

 Ramon Norman, Air Quality Engineer, Permits 

Patrick Houlihan, Senior Air Quality Specialist, Compliance 

Kevin McCaffrey, Senior Air Quality Specialist, Incentives 

Leonard Scandura, Manager, Permits 

Errol Villegas, Program Manager, Strategies and Incentives 

Samir Sheikh, Director, Strategies and Incentives 

I. SUMMARY 

The San Joaquin Valley Unified Air Pollution Control District (District) is committed to 

protecting public health for all residents in the San Joaquin Valley (Valley) through 

efforts to meet health-based state and federal ambient air quality standards with 

efficient, effective, and entrepreneurial air quality management strategies. One such 

strategy includes a commitment in both the District’s 2007 Ozone Plan and 2008 PM 2.5 

Plan to amend Rule 4702 (Internal Combustion Engines) to reduce emissions of oxides 

of nitrogen (NOx) from this source category. 

District staff is proposing to amend Rule 4702 to clarify existing rule standards and to 

achieve much needed NOx emission reductions. Proposed amendments would be 

applicable to non-agriculture operated internal combustion engines. Proposed 

amendments include provisions for limited use engines, point of sale requirements for 

engines rated at 25 to 50 brake horsepower (bhp), more stringent NOx emission limits 

for various types of engines within this category, and SOx requirements would be added 

to rule language. 

A. Reasons for Rule Development and Implementation 

The federal Environmental Protection Agency (EPA) has classified the San Joaquin 

Valley Air Basin as extreme non-attainment area for federal ambient air quality standard 

for ozone and non-attainment for the standard for particulate matter with aerodynamic 

diameter of 2.5 micrometers and less (PM2.5). The California Air Resources Board 

(ARB) has classified the basin a severe non-attainment area for the state’s ozone 
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standard. As a result of these classifications, the District is required to evaluate sources 

of pollution and create a strategy (plan) for how the District will come into attainment of 

the standards. The ozone and PM2.5 attainment strategies are comprised of regulatory 

and incentive-based measures to reduce emissions of NOx, volatile organic compounds 

(VOCs), sulfur oxides (SOx) as well as directly-emitted particulates. 

The District’s 2007 Ozone Plan and 2008 PM 2.5 Plan each identified Rule 4702 

(Internal Combustion Engines) as part of the District’s attainment strategy. There is no 

commitment for a specific quantity of NOx reductions in either District attainment plan. 

B. Description of Rule Project 

The proposed amendments to Rule 4702 will seek to obtain as much NOx emission 

reductions from the source category as expeditiously practical, technologically feasible, 

and economically reasonable, as determined by the District’s Governing Board. 

C. Rule Development Process 

Work on this rule amending project began in 2007 with the adoption of the District’s 

2007 Ozone Plan and then the adoption of the 2008 PM 2.5 Plan. Each attainment plan 

identified Rule 4702 as part of the District’s attainment strategy. District staff began the 

rule development process with extensive research as a part of a feasibility study 

performed to determine if there was potential from this source category for achieving 

additional emission reductions. 

After the completion of the feasibility study, staff continued to research the District’s 

permits database, industry standards, technological advancements and actions taken 

by other regulatory agencies regarding the technological and economic feasibility of 

amending rule standards to make them more stringent. District staff presented their 

research findings to stakeholders, industry, ARB, and EPA during a public Scoping 

Meeting on June 24, 2010. During the Scoping Meeting staff outlined the potential 

range of the rule project and requested comments, feedback, and cost information from 

all interested parties. It was during the public Scoping Meeting that staff explained to 

stakeholders that research was being conducted as to the feasibility of controlling SOx 

and that staff was considering the replacement of engines with electric motors where 

possible. Staff also explained the decisions why certain engine categories would not be 

amended during this rule-amending process; specifying that these decisions were 

based on research, the evaluation of the permits database, and conversations with 

industry. 

After evaluating the comments received regarding the proposed rule concepts, staff 

crafted draft rule requirements based on the best available information. The District 

then hosted a Public Workshop on September 9, 2010 to present and discuss the 

proposed amendments to the rule. The draft amendments to Rule 4702, as presented 

in September 2010, included requirements that nearly all non-AO spark ignited engines 
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meet a NOx concentration of 11 ppmvd (@ 15% O2). Draft VOC and CO limits were 

also being proposed to be lowered to levels seen in a comparable South Coast AQMD 

engine rule. Knowing that the proposed rule requirements would potentially be costly to 

some facilities, the District included an annual fee option (similar to Rule 4320), allow 

additional compliance options. 

A socioeconomic focus group was also held during the first public workshop. 

Stakeholders were solicited for more cost information and potential impacts to their 

operations in light of the draft amendments. 

After the September Public Workshop, District staff met several times with stakeholders. 

District staff worked closely with the affected stakeholders to refine the rule 

requirements and address the cost impacts to affected facilities and address feasibility 

concerns of implementing various control technologies. Due to the remaining issues, in 

December 2010, District staff provided an update to the District’s Governing Board on 

the status of this project with plans to bring forth a proposed rule for Governing Board 

consideration in 2011. 

The District hosted a technical discussion session in January 2011 for the District’s 

Citizens’ Advisory Committee of Industry (CAGI) to get further input on issues and 

concerns from affected stakeholders. The comments received from the public, affected 

sources, interested parties, EPA, and ARB during the public workshop, stakeholder 

meetings, and technical session were used to develop the second draft amendments to 

the rule. The new amendments included provisions for engines used on a limited basis, 

meaning they are only used during part of the year. A phased compliance schedule 

was developed to extend compliance deadlines for facilities with multiple engines to 

lessen the financial burden on these facilities. In order to maximize NOx reductions 

VOC and CO limits were changed back to current levels. Upon further reflection, the 

cyclically loaded and waste gas combustion engines were returned to current NOx 

emission limits. The second draft of the rule was released to the public for comment 

and the District conducted the final public workshop June 22, 2011. 

Staff continued to work diligently with the remaining affected stakeholders and EPA to 

draft the Proposed Rule. Compared to the June version of the rule, the Proposed Rule 

provides a requirement specific to lean burn engines used for gas compression. 

Additionally, the phased in compliance schedule has been further extended for those 

operators with more than twelve engines at a stationary source. Section IV.B of this 

Final Draft Staff Report provides a detailed discussion for each proposed amendment. 

Pursuant to state law, the District performed a socioeconomic impact analysis. As part 

of the District socioeconomic analysis process, District staff solicited volunteers from 

affected stakeholders and interested parties to participate as members of the 

Socioeconomic Focus Group. District staff convened a meeting of the Focus Group in 

conjunction with the first workshop in September 2010 to assist District staff in gathering 

information on regulatory compliance costs and business impacts resulting from 
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compliance with the draft amendments. The results of the socioeconomic analysis were 

published in a report and presented along with the draft rule amendments to the public 

and interested parties during the June 2011 workshop; at which time staff solicited more 

feedback from stakeholders. 

The proposed rule and final draft staff report were published and made available to 

affected sources and interested parties prior to a public hearing to consider the adoption 

of the rule by the District Governing Board. The proposed amendments are scheduled 

to be presented to the Governing Board for the public hearing to consider adoption of 

the amendments to the rule on August 18, 2011. 

II. GLOBAL CLIMATE CHANGE AND GREENHOUSE GASES 

The California Global Warming Solutions Act of 2006 (AB 32) created a comprehensive, 

multi-year program to reduce greenhouse gas (GHG) emissions in California, with the 

overall goal of restoring emissions to 1990 levels by the year 2020. In the coming 

years, ARB and the Legislature will be developing policies and programs to implement 

AB 32. The District believes that the evidence and the rationale that climate change is 

occurring is compelling and convincing. In addition to the long-term consequences of 

climate change, the District is concerned with the potential ramifications of more 

moderate but imminent changes in weather patterns. The Valley depends heavily on 

agriculture for its economy and has developed agricultural practices based on the last 

several decades of weather patterns. Unanticipated and large fluctuations in these 

patterns could have a devastating effect on the Valley’s economy. 

While there are many win-win strategies that can reduce both GHG and criteria/toxic 

pollutant emissions, when faced with situations that involve tradeoffs between the two, 

District staff believes that the more immediate public health concerns that may arise 

from an increase in criteria or toxic pollutant emissions should take precedence. The 

San Joaquin Valley Air Pollution Control District’s Governing Board adopted the Climate 

Change Action Plan (CCAP) in August 2008. For California Environmental Quality Act 

(CEQA) requirements, one of the goals of the CCAP is to establish District processes 

for assessing the significance of greenhouse gas impacts. The District has developed a 

policy and guidance for addressing greenhouse gases under CEQA. 

III. BACKGROUND 

An internal combustion (IC) engine is any engine that operates by burning its fuel inside 

the engine. IC engines generate power by the combustion of an air/fuel mixture. The 

main types of IC engines are spark-ignited (SI) engines and compression-ignited (or 

diesel) engines. In the case of spark-ignited (SI) engines, a spark plug ignites the 

air/fuel mixture. SI engines come in several designs such as: two-stroke and fourstroke, rich-burn and lean-burn, turbocharged and naturally aspirated. SI engines may 
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use one or more fuels, such as natural gas, propane, butane, liquefied petroleum gas, 

oil field gas, digester gas, landfill gas, methanol, ethanol, and gasoline. 

Compression-ignited (CI) engines rely on heating of the inducted air during the 

compression stroke to ignite the injected diesel fuel. In addition to being classified into 

compression-ignited and spark-ignited, IC engines can be further divided into two-stroke 

and four-stroke engines. Most diesel engines are four-stroke, while larger diesel 

engines often are two-stroke. Natural gas fired spark-ignited engines are usually fourstroke, but some operators prefer two-stroke engines for their applications. 

Most IC engines are used to power pumps, compressors, or electrical generators. IC 

engines are used by a large variety of private businesses and public agencies 

throughout the SJVAB. Examples of businesses and industries that use IC engines that 

could be affected by this project include schools and universities, agriculture, oil and 

gas production and pipelines, petroleum refining, manufacturing facilities, food 

processing, electrical power generation, landfill and waste water treatment facilities, and 

water districts. Many of the permitted compression-ignited engines in the District are 

used as emergency engines and are used to provide backup power when electric 

service is interrupted. 

IV. CURRENT RULE 4702 AND PROPOSED AMENDMENTS 

A. Existing Rule 4702 

Rule 4702 was adopted in August 2003 and was last amended in January 2007. The 

purpose of Rule 4702 is to limit NOx, CO, and VOC emissions from stationary IC 

engines. The rule applies to any stationary IC engines with a rated brake horsepower 

(bhp) greater than 50. The rule divides engines into those used in agricultural 

operations (AO) and those used in other, non-agricultural operations (non-AO). 

Rule 4702 provides some exemptions from the emissions standards or other 

requirements of the rule for engines used in certain specific applications, such as an 

emergency standby engine, military tactical equipment, and certain types of engines 

used in AO (e.g., wind machines, mobile agricultural equipment, engines used to propel 

implements of husbandry). Rule 4702 exempts engines from complying with the 

emission limits provided they do not exceed 200 hours of operation per calendar year 

and meet other conditions. 

The existing NOx concentration limits in Rule 4702 range from 25 ppmv to 150 ppmv 

corrected to 15% O2, depending on engine category. The VOC and CO concentration 

limits range from 250 to 750 ppmv (depending on engine category) and 2,000 ppmv, 

each corrected to 15% O2, respectively. 

 
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B. Proposed Amendments to Rule 4702 

The following paragraphs detail the proposed modifications to rule language. See 

Proposed Rule 4702 for exact changes. 

1. Rule Title, Section 1.0 Purpose and Section 2.0 Applicability 

The rule’s title would be modified to remove the phrase “Phase 2”. This phrase is a 

holdover from past years and the phrase no longer reflects the rule’s scope. 

The Purpose section of the rule would add SOx to the list of pollutants. In the 

Applicability section, the minimum horsepower rating of engines subject to the rule 

would be amended from 50 brake horsepower to 25 brake horsepower. 

2. Section 3.0 Definitions 

The definitions for “Agreement to Electrify,” “Beam Balanced Pumping Engine,” and 

“Crank Balanced Pumping Engine” would be removed, since they are no longer found in 

the body of the rule. 

The existing rule defines “Agricultural Operations” by referencing it to the definition in 

Rule 4550 (Conservation Management Practices). For reader clarity, the definition of 

“Agricultural Operation” will be included in Rule 4702. 

Seven definitions would be added to the rule. These definitions are: Air Pollution 

Control Officer (APCO); California reformulated diesel; higher heating value; limited-use 

engine; operator; owner; and variable-load engine. These definitions would be added to 

improve reader clarity. Also, throughout the rule, the word “owner” would be replaced 

with the word “operator” to make the rule language consistent with other District rules, 

and to provide clarity as to whom rule requirements are applicable to. 

District staff is re-locating the definition of low-use engine from the Section 4.0-

Exemptions to the Section 3.0-Definitions. No requirements have been added or 

removed from the definition. 

The language in two definitions would be edited. The definition of California 

reformulated gasoline would better specify the section of the California Code of 

Regulations where the state’s definition is located. The definition of replacement engine 

would be modified to change the starting date of replacement to reflect the current 

amendments to the rule. 

The definitions would be renumbered as needed. 

In the June 22, 2011 version of the staff report, there was a definition of “existing cyclic 

field gas fueled engines.” This has been removed from the rule because there is no 
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NOx control technology that will allow newer cyclically-loaded engines to be controlled 

below their current emission level, even with the latest emission control technology. 

3. Section 4.0 Exemption

The language in Section 4.2 would be amended to consolidate requirements for 

emergency standby and low-use engines. The requirements to be considered a lowuse engine would be moved to Section 3.0 (Definitions) of the rule. 

Section 4.4 allows an exemption from the requirements of Best Available Control 

Technology (BACT) and Offset requirements of Rule 2201 (New and Modified 

Stationary Source Review Rule) if the replacement engine is installed for the sole 

purpose of complying with Rule 4702. In the first draft version of the rule presented 

during the September 2010 public workshop, District staff proposed to delete Section 

4.4 because, in the past, EPA has disapproved prohibitory rules which included a 

similar exemption. EPA has stated in previous rulemaking projects that BACT and 

Offset requirements should be addressed in District Rule 2201 instead of the prohibitory 

rule. 

However, comments were received from stakeholders recommending to keep the 

existing BACT and Offset exemption in the rule for replacement engines that are 

needed to comply with the draft rule requirements. After conferring with the District’s 

Permit Services Department, staff agrees with the commenter’s justification. The 

existing Section 4.4 in Rule 4702 will be retained. Staff believes that the narrow and 

limited exemption from BACT and Offset specified in existing Rule 4702 for replacement 

engines is appropriate since Section 5.2 of the rule requires an operator to replace 

existing older compression-ignited engines with cleaner EPA-certified Tier 3 or Tier 4 

engines. 

If the exemption were removed from Rule 4702, operators who, according to the rule, 

must replace their engines with Tier 3 engines, for instance, would instead be subject to 

BACT when they apply for permits to install those Tier 3 engines. Instead of installing a 

Tier 3 engine, an operator may be required to electrify. Although existing Rule 2201 

Sections 4.2.3 and 4.6.8 allow exemptions from BACT and Offset requirements, the 

exemptions apply only to the installation or modification of an emission control 

technique performed solely for the purpose of compliance with the requirements of 

District, State or Federal air pollution control laws, regulations or orders. Such 

exemptions do not apply to replacement units needed to comply with the prohibitory 

rules. Therefore, the District will retain the existing language in Rule 4702. 

4. Section 5.0 Requirements 

This section of the rule enumerates emission limits and monitoring requirements for 

stationary IC engines. 
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o New Section 5.1 – IC Engines between 25 and 50 Brake Horsepower 

New Section 5.1 would establish the requirements for spark-ignited engines and 

compression-ignited engines rated at 25 to 50 brake horsepower (bhp) that are used 

exclusively in Non-AO. These small engines are already regulated under the existing 

federal Standards of Performance. The provision is intended to be a point of sale 

provision and would prohibit a person from selling, or offering for sale engines rated at 

25 to 50 bhp unless the engines meet the applicable requirements and emission limits 

specified in the Code of Federal Regulation Title 40 Part 60 (40 CFR 60) Subpart IIII 

(Standards of Performance for Stationary Compression Ignition Internal Combustion 

Engines) and 40 CFR 60 Subpart JJJJ (Standards of Performance for Stationary Spark 

Ignition Internal Combustion Engines) for the year that the engine is purchased. The 

provision is intended to ensure that more polluting engines are not sold to another 

person or entity if cleaner small engines that meet the NSPS standards are available in 

the market. District staff has removed the terms “solicit the operation, supplying, and 

install” from this provision. This provision would not affect the leasing of these engines 

because the ownership of the engine would remain with the lessor until such time as the 

lessor chooses to sell the engine; at which time, this provision would apply. 

This provision regulates engines by attrition rather than requiring the operator to install 

additional emission control system on existing engines as is the case for engines 

greater than 50 bhp. Over time, the non-agricultural operations (non-AO) engines 

between 25 and 50 bhp will be replaced with the cleanest-burning engines available and 

the replacement happens at a time of the operator’s choosing, since the operator elects 

when to replace a given engine. If there is no cleaner engine available, meaning that 

the federal emission limits haven’t changed since the engine was manufactured, the 

engine can change hands and continue to operate within the Valley because the engine 

is the cleanest version available. Conversely, if there is a cleaner federal emission 

standard than the standard at the time the engine was manufactured, rather than 

continuing to have the older, dirtier engine continuing to operate, but at a different 

Valley location, the District is proposing that the older engine be retired or retrofitted to 

meet the latest standard. The draft requirement, as written, is a win-win situation for 

both operators and Valley air quality because it provides continuous air quality 

improvement through normal engine turnover as well as operator flexibility by allowing 

the operator, not the District, to determine when to replace an engine. 

Additionally, the draft rule amendments would require the current owner of non-AO 

small engines operated in commercial, industrial, and institutional facilities to submit a 

one-time report to the District which includes information on the number of engines, 

location of each engine, engine manufacturer, model designation and engine serial 

number, engine bhp, fuel type and consumption rate, ignition type and combustion type, 

purpose of the engine, and daily operating schedule. The purpose of the report is to 

allow the District to improve the emission inventory for this category. 

 
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o Section 5.2 – Engines Greater than 50 Horsepower 

Section 5.2 would separate the existing emission limits/standards for non-AO from 

agricultural operations (AO) spark-ignited engines and from compression-ignited 

engines greater than 50 bhp. This section would also specify the proposed limits for 

non-AO spark-ignited engines greater than 50 bhp. The following are the sub-sections 

being modified as well as the new provisions being proposed: 

• Section 5.2.1 – Existing Emission Concentration Limits 

Section 5.2.1 would be reorganized to separate AO engines from non-AO engines. The 

existing emission limits for spark-ignited engines used in AO would be relocated and 

new emission concentration limits for non-AO engines would be placed in a separate 

table. The non-AO limits would be effective until the new emission limits in new table 

become effective. The compliance schedule for the non-AO spark-ignited engines is 

specified in Section 7.4 of the rule. 

District staff did not consider reducing the emission limits on AO engines as part of this 

rule project. AO engines have just recently been required to comply with Rule 4702; the 

current emission limits have compliance dates from January 2009 through January 

2015. By comparison, non-AO engine emission limits were first adopted in 2003; 

meaning that operators with non-AO engines have had an opportunity to get a return on 

their investment. . Appendix D of the Final Draft Staff Report for Revised Proposed 

Amendments to Rule 4570 (Confined Animal Facilities) dated October 2010 discusses 

the San Joaquin Valley agricultural community economic conditions. Farms, ranches 

and dairies generally, speaking, do not have the ability to pass on higher costs to the 

supply chain due to regulatory framework for these operations. In order to give 

agricultural operators some return on their capital investment, it would be imprudent to 

impose new limits for agricultural engines at this time. District staff will re-evaluate 

potential emission reductions from AO engines as part of future plan control measures 

and rule projects. 

A new constraint has been added to this section. In Section 5.1.2.2, if an operator 

elects to use the “fee payment in lieu of compliance” option, the current emission limits 

would remain in place for these engines. In other words, the provision prevents existing 

engines that are included in a fee payment program from increasing their emissions 

above the current emission limits. Including this provision is fulfills an EPA requirement 

called “anti-backsliding,” meaning changes to a rule cannot allow operators to increase 

their emissions above whatever is currently in place. An example of when emissions 

could increase would be if operators in the fee payment program were allowed to pull all 

NOx emission control equipment off their engines, and then pay the fee based on 

uncontrolled engine emissions. NOx emissions from the individual engine would be 

higher than the current rule allows and EPA would consider such an action “backsliding” 

from current level of control. Previous draft versions of the rule did not address the 

potential for increased emissions when engines enter the fee payment program. 
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• Section 5.2.2 – Non-AO Spark-Ignited Engine Emission Concentration 

Limits 

Section 5.2.2 would establish the emission concentration limits for non-AO spark-ignited 

engines greater than 50 bhp. In the September 9, 2010 version of the draft rule 

amendments that were presented at the first public workshop, District staff proposed 11 

ppmv NOx limit for all engines in this category. However, after considering the 

comments and recommendations from stakeholders and the Citizens Advisory Group of 

Industry (CAGI), District staff is now proposing the NOx emission limits that take into 

account the differences between engines used in different applications. Table 1 

summarizes the proposed emission limit changes. The limits are in concentration units 

of parts per million by volume on a dry basis (ppmvd), corrected to 15% oxygen. 

Table 1 – Current and Proposed NOx Limits (in ppmvd corrected to 15% oxygen) 

Current Limit Proposed Limit 

Rich-Burn Engines 

A. Waste Gas Fueled Engine 50 50 

B. Cyclic Loaded, Field Gas Fueled 50 50 

C. Limited Use Engine ---- * 25 

D. Rich-Burn Engine, not listed above 25 or 

96% reduction 11 

Lean-Burn Engines 

E. Two-Stroke, Gaseous Fueled, 

 < 100 hp Engine 

75 or 

90% reduction 75 

F. Limited Use Engine --- * 65 

G. Lean-Burn Engine used for gas 

compression 

--- * 65 or 93% reduction 

H. Lean-Burn Engine, not listed above 65 or 

90% reduction 11 

* Limited-use engines and variable-load engines are not categories in the current rule. They are 

currently subject to the applicable “not listed above” emission limits.

Due to the heat content variability of waste gas, NOx control can be problematic for 

engines fired on waste gas, therefore, District staff is proposing that there be no change 

to the NOx emission concentration limit for waste gas fueled engines. 

Cyclic-loaded, field gas fueled engines can achieve some level of control, but not the 

very stringent control that can be imposed on engines that operate in a narrow range of 

loads. The exhaust gas temperature of cyclic loaded engines varies as a function of the 

engine load. Catalyst chemistry depends on a minimum temperature to be effective. 

When the cyclic load engine is operating in an engine load range that the exhaust gas is 

in the catalyst’s effective range, the emissions are well-controlled, but as the engine 

cycles out of the “sweet spot,” NOx control is less. Eventually, the exhaust gas 

temperature can be too low for any effective control. For this reason, District staff is 
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proposing that the NOx limit for cyclic loaded field-gas fueled engines be left 

unchanged. 

Two-stroke, gaseous fueled engines between 50 hp and 100 hp would remain at the 

current NOx emission level. There is no technology that will allow a lower NOx level. 

The proposed amendments create a new category of engines that operate less than 

4,000 hours per year, based on the cost effectiveness of installing additional catalyst for 

these engines compared to engines that have higher utilization. These engines will be 

designated as limited use engines. This is not to imply that the proposed amendments 

leave the engines as uncontrolled. The NOx concentration limit for limited use rich-burn 

engines would be 25 ppmv NOx, which is the current emission limit for rich-burn 

engines. The NOx emissions foregone resulting from not lowering the existing NOx limit 

of 25 ppmv to 11 ppmv for the limited use engines is about 1.3 tons NOx/year or about 

0.004 tons/day as shown in Appendix C of the Draft Staff Report. 

Based on the District Permit Services database, there are no lean-burn engines 

currently operating less than 4,000 hours per year in the District. However, District staff 

is proposing to include this limited-use category of engines in order to provide operators 

with the option of limiting their engine usage so as not to retrofit with an expensive SCR 

system, in exchange for reduction in their current emissions level. Since there are no 

lean-burn engines currently operating less than 4,000 hours per year in the District, in 

carving out this group of engines, there is no NOx emission impact from this engine 

category. 

Another new category would be created by the proposed rule - lean-burn engines used 

in gas compression. In general, these engines operate over a wide range of loads. As 

noted in the EPA’s technical support document (see Appendix F), these engines 

fluctuate over a broad range of conditions making SCR use problematic. For this 

reason, District staff proposes that the lean-burn engine used in gas compression be 

created with a NOx control as a percent reduction over the uncontrolled emission factor. 

Although District staff is leaving certain types of engines at their current numeric 

emission limits, for most engines the proposed rule removes the percent reduction as 

an alternative limit. As currently enforced, the operators with the percent reduction are 

assuming that the input to the control device is an uncontrolled engine. The percent 

reduction option when converted from pounds NOx per MMBtu to ppmvd at 15% 

oxygen is equal to or greater than the proposed numeric limit, therefore, removing the 

percent reduction option will not increase emissions from the targeted engine. 

• VOC and CO Emission Limits 

The September 2010 draft rule contained a CO limit of 500 ppmv and 30 ppmv VOC 

limit. Stakeholders recommended leaving the existing 2,000 ppmv CO and 250/750 

VOC limits in place. The Engine Manufacturers Association (EMA) commented that 

they do not believe reductions are achievable in practice for all stationary engine 
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systems particularly for existing engines under varied operating and field conditions. 

EMA stated that for spark-ignited engines, there is a known relationship between 

emissions of NOx, VOC, and CO, in that as the engine is adjusted to reduce NOx, the 

VOC and CO emissions will increase. Efforts to adjust the engine to reduce VOC and 

CO emissions would result in an increase in NOx emissions. District staff contacted 

South Coast AQMD staff to determine if the current 30 ppmv VOC in South Coast 

AQMD’s Rule 1110.2 (Emissions from Gaseous - and Liquid-Fueled Engines) is being 

achieved. District staff has found that there are several variances that have been 

approved by South Coast AQMD Hearing Board allowing a temporary regulatory relief 

from the 30 ppmv VOC limit until such time that an alternate limit, which is an allowable 

provision of South Coast AQMD Rule 1110.2, could approved by their Executive Officer. 

Based on stakeholders’ recommendations and results of the South Coast AQMD 

variances, District staff believes that it is appropriate to not change the existing VOC 

limits in Rule 4702. Likewise, the current CO limit of 2,000 ppmv would not be changed. 

Keeping the existing VOC and CO emission limits in the current rule would allow engine 

manufacturers and emission control system manufacturers to have the much-needed 

flexibility to be able to achieve much lower NOx emissions under varying field operating 

conditions and applications. 

• Section 5.2.2.2 – Alternative Emission Control Option 

Section 5.2.2.2 allows operators of non-AO spark-ignited engines an alternative to 

installing a NOx emission control system. Operators have the option to pay annual 

fees. The District would take the fees generated by the alternative emission control 

option to fund other emission-reducing projects that would get equivalent reductions. 

Operators would remain subject to CO and VOC emission concentration limits – only 

NOx emissions would be allowed to fall under an alternative emission control option. As 

noted above, a provision would be added to re-iterate the Section 5.2.1.2 requirement 

that the engines of operators who elect the fee payment option would not be allowed to 

emit NOx above the applicable current NOx limit to preclude any increase above the 

current NOx emissions. More details on the fee-payment option are contained in new 

Section 5.6 of the rule. 

o Section 5.6 – Alternative Emission Control Option Calculations

Section 5.6 details the calculation of emissions and fees for this option. The fees are 

based on the total annual NOx emissions for the unit. As such, this program does not 

constitute a discretionary economic incentive program as defined by 40 CFR 61 Subpart 

U. The District intends to use the money generated by this program to acquire 

equivalent emission reductions from other sources. Details of the program itself will be 

sent to EPA when the program is initiated. Because any emission reductions generated 

by the fee program cannot be credited to the District until the reductions are actually 

achieved, District staff is taking no State Implementation Plan (SIP) emission reduction 

credit for the overall rule project. Not taking SIP credit for NOx emission reductions 

does not affect either the District’s 2007 Ozone Plan attainment strategy nor does it 

affect the District’s 2008 PM2.5 attainment strategy because the control measure for 
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amending Rule 4702 did not include any specific amount of emission reductions. The 

emission reduction analysis in Appendix B of this staff report is based on each engine 

complying with the rule through the installation of NOx emission control technology. 

The District staff expects that the emission reductions associated with the fee payment 

option will be higher than by requiring installation of individual control technology. 

However, any estimate of additional reductions would be speculative, because neither 

the number nor the size of engines participating in the fee payment program can be 

predicted in advance of the program. 

o Section 5.7 – Control of Sulfur Oxide (SOx) Emissions and 

o Section 5.10 – SOx Emissions Monitoring Requirements 

The rule would limit SOx emissions through fuel choice. For non-AO engines, these 

fuels are widely available. Although the proposed sections limit the sulfur in the 

engine’s fuel, for SIP purposes, the District is not taking any credit for SOx emission 

reductions associated with the rule modifications because it is expected that most 

operators are already comply with the requirement. Although SOx is a precursor to 

PM2.5, the control measure in the PM2.5 Plan did not commit the District to any SOx 

reduction, therefore, the attainment date is not affected by not taking SIP credit for the 

potential SOx emission reductions. 

o Section 5.0 – Miscellaneous Changes

Sections and section references have been renumbered as needed and some section 

titles have been modified for reader clarity. 

5. Section 6.0 Administrative Requirements 

o Section 6.1 – Emission Control Plan 

Language would be added to these section allowing operators with no changes to their 

emission control plan to submit a letter stating that there are no changes rather than 

having to submit the entire plan. District staff agreed with a stakeholder who stated that 

preparing an emission control plan is time-consuming and is redundant if the existing 

emission control plan is already adequate. The proposed change would streamline 

compliance for certain operators of existing engines. 

o Section 6.4.6 – SOx Test Methods and 

o Section 6.4.7 – Higher Heating Value Test Methods 

Section 6.4.6 would be added in order to specify the test methods for determining 

oxides of sulfur, total sulfur as hydrogen sulfide, sulfur content of liquid fuel, and 

calculation method for SOx control efficiency. Section 6.4.7 would be added to specify 

the allowable test methods for determining a fuel’s higher heating value. These test 

methods were added to complement the addition of SOx requirements. 

o Section 6.5 – Inspection and Monitoring (I&M) Plan 

Language would be added to this section to indicate that operators, who have no 

changes to the facility’s I&M Plan, can submit a letter to that effect rather than 
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submitting a new plan. This provision affords operators a streamlined process when 

there are no changes to the facility’s current I&M Plan. 

o Section 6.0 – Miscellaneous Changes

Section numbers and section references would be renumbered, as needed. 

6. Section 7.0 – Compliance Schedule 

District staff has reviewed the compliance schedules already in the rule and removed 

those schedules that have are in the past. A new compliance section was added for 

existing engines that would need to comply with the proposed amendments. 

o Existing Sections 7.3, 7.4, and 7.5 

Language has been removed from these sections that apply to schedules that have 

already passed. 

o New Section 7.5 

This section would require the owner of a non-AO spark-ignited engine subject to the 

rule to comply with the proposed requirements according to a specific compliance 

schedule. The September 2010 version of the draft rule had a single compliance date. 

In response to stakeholder comments, the draft compliance date has been amended 

and now a phased-in compliance schedule is proposed. Additional discussions with 

stakeholders yielded a further refinement - operators with more engines have a longer 

period of time to come into compliance, starting in 2014 and ending in 2017. The longer 

compliance schedule recognizes that operators with more engines might have some 

logistical issues in bringing so many engines into compliance in a short amount of time, 

while recognizing the District’s commitment to expedite air quality benefits as committed 

to by the Governing Board with the dual path strategy. 

Stakeholders asked for a compliance timeline ending in 2020. While staff recognizes 

that there is no specific NOx reduction commitment in either air quality attainment plan; 

staff feels that providing a nine-year compliance timeline would be counterproductive to 

District air quality attainment goals and the dual path strategy adopted by the District 

Governing Board. 

In developing and adopting the 2007 Ozone Plan, the District’s technical and legal 

analysis indicated that reclassification to “extreme” reflecting attainment no later than 

2023 was the only option available to the District. However, the District Governing 

Board concurrently adopted a dual path strategy to ensure continual progress and 

attainment at earliest practicable date. This dual path strategy commits the District to 

continuously look for any and all new measures that could bring the Valley into 

attainment sooner. Table 2 below shows the proposed compliance schedule. It is 

important to note that the division of compliance date requirements in Table 2 is specific 

to the amount of engines per stationary source and not to the amount of engines owned 

by an operator. For example, an operator that owns 12 engines with five engines at one 
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facility and the other seven engines at another facility would not have the 2017 

compliance timeline as allowed for operators with at least 12 engines at a stationary 

source; because all the engines are not at one stationary source, rather than one 

location. 

Table 2 – Proposed Compliance Schedule for Non-AO Spark Ignited Engines 

Engines to be in Compliance at a 

Stationary Source 

Emission 

Control Plan 

Authority to 

Construct and 

Inspection and 

Monitoring Plan 

Full 

Compliance 

Single Engine at a stationary 

source 

1/1/12 1/1/13 1/1/14 

Operator with at least two engines, but less than 12 engines at a stationary source 

33% or more of the engines 7/1/12 1/1/13 1/1/14 

66% or more of the engines 7/1/12 1/1/14 1/1/15 

100% of the engines 7/1/12 1/1/15 1/1/16 

Operator with at least 12 engines at a stationary source 

25% or more of the engines 7/1/12 1/1/13 1/1/14 

50% or more of the engines 7/1/12 1/1/14 1/1/15 

75% or more of the engines 7/1/12 1/1/15 1/1/16 

100% of the engines 7/1/12 1/1/16 1/1/17 

o New Section 7.6 

The owner of a Non-AO spark-ignited engine who elects to pay annual NOx emission 

fees to the District in lieu of complying with the proposed Table 2 emission limits of the 

rule would be required to submit an Emission Control Plan which includes the 

information specified in new Section 7.6.1 by July 1, 2012 as specified in Table 6 of the 

rule. The owner would be required to pay the total annual fee to the District no later 

than June 30 of each year for the NOx emissions of the previous calendar year. 

Payment would continue annually until the engine either is permanently removed from 

use in the San Joaquin Valley Air Basin and the Permit-to-Operate is surrendered, or 

the operator demonstrates compliance with the proposed rule’s Table 2 emission limits. 

o Section 7.0 – Miscellaneous Changes

Section numbers and section references would be renumbered, as needed. 

C. Implications of the Federal Stationary IC Engine Requirements

Although the District has some of the most stringent rules in the nation, EPA also 

creates rules to limit emissions. One such rule that affects stationary IC engines is 40 

CFR 63 Subpart ZZZZ (National Emissions Standards for Hazardous Air Pollutants for 

Stationary Reciprocating Internal Combustion Engines). Also called a Maximum 

Achievable Control Techniques (MACT), the MACT divides the engines into several 

groups and has different provisions for the different engine groups depending on 
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16 Final Draft Staff Report with Appendices 

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whether facility where the engine is located is a major or area Hazardous Air Pollutants 

(HAPs) source, spark-ignited or compression-ignited, rich-burn or lean-burn, etc. For 

some engines, the MACT requires periodic maintenance only. For other engines, there 

are specific emission limits, source testing, and monitoring requirements. There are 

either CO or formaldehyde emission limits for certain larger spark-ignited engines. It is 

these engines that are of interest for this rule project. 

There are some engines that are in compliance with the MACT’s low emission limits for 

CO/formaldehyde without an add-on control system. An existing engine that does not 

meet the emission limits would need to be modified, which usually means installing an 

emission control system containing an oxidation catalyst. The installation of the 

oxidation catalyst would be in addition to any equipment necessary to meet the Draft 

Rule 4702’s proposed NOx limit. 

In addition to the potential to have a two-catalyst emission control system, the MACT 

compliance schedule is a little ahead of schedule for Draft Rule 4702. All spark-ignited 

engines at area HAPs sources that are subject to the IC engine MACT must be in full 

compliance with standards by May 2013. As noted earlier, some engines are already in 

compliance with the MACT’s CO/formaldehyde limits and no retrofit would be required 

to meet the MACT standard. The compliance schedule for Draft Rule 4702 is tiered, 

meaning that, for operators with multiple engines, compliance deadlines are phased in 

over three or four years beginning in 2014. In a worst case scenario, operators could 

make modifications to meet the IC engine MACT in 2013, and then need to make more 

modifications in 2014. District staff believes that by making operators aware of the 

changes in the District’s rule soon enough would allow the operators to combine MACT 

and District rule retrofits to minimize downtime and costs. 

Stakeholders contacted about how they were going to meet the IC engine MACT stated 

that they were early in their assessment process and hadn’t fully determined their 

course of action. In general, operators are concerned about the engineering design 

challenges as well as the operational complexity inherent in a two-catalyst emission 

control system. 

V. EMISSION REDUCTION ANALYSIS 

District staff queried the District Permit Services Database for all engines, and then 

manually sorted the engines into one of three categories: emergency standby, richburn, and lean-burn. No analysis was done for emergency standby engines because 

the proposed rule amendments do not affect this type of engine. Of the remaining 

engines, District staff determined that out of 326 rich-burn engines, only 160 engines 

would be required to reduce their NOx emissions. For lean-burn engines, District staff 

found a total of 97 lean-burn engines, of which 62 have permit limits higher than the 

proposed rule limits. Based on the assumptions used, District staff estimates that the 

proposed changes in the rule limits for non-AO spark-ignited engines would lead to 
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approximately 1.4 tons per day of NOx emission reductions. However, in the strictest 

sense, these emission reductions cannot be directly credited to the District’s attainment 

plans (State Implementation Plan (SIP) purposes) because at least a portion of them 

will come as part of the fee payment program. Emission reductions in a fee payment 

program cannot be credited to the District until they are actually achieved. Although 

District staff expects that the Rule 4702 program will generate more emission reductions 

than what has been calculated, this rule project will take no credits for SIP purposes at 

this time. 

It is the District’s experience that, when an emission limit is reduced, a small percentage 

of operators will choose to replace their IC engines with electric motors rather than 

retrofit with an emission control system. Based on past experience with engine rule 

amendments, there could be two or three of the 222 affected engines replaced by 

electric motors. It would be speculative, at best, to determine which engines would 

electrified, therefore the following emission reduction analysis does not include an 

estimate for NOx reductions associated with electrification scenarios. All affected 

engines are analyzed as if they will add NOx controls rather than replace the engine 

with an electric motor. 

District staff will use 1.4 tons per day of NOx reductions for cost effectiveness purposes. 

A summary of the analysis results is shown in Table 3 and details of the calculations are 

in Appendix B of this staff report. 

Table 3 – Summary of Estimated NOx Reductions Used for Cost Effectiveness 

Calculations 

Engine Type 

Total 

Permitted 

Engines 

Number 

Affected 

Engines 

Total Rated 

Power (bhp)

Estimated 

NOx 

Reductions 

(tpy) 

Estimated 

NOx 

Reductions 

(tpd) 

Rich-Burn 326 160 80,738 131.5 0.36

Lean-Burn 97 62 123,886 390.9 1.07

Totals 423 222 204,624 522.4 1.43

VI. COST EFFECTIVENESS ANALYSIS 

Draft Rule 4702 would implement low NOx limits for non-AO spark-ignited engines. 

These engines burn natural gas, gas from waste products or field gas. It is the District’s 

experience that, when an emission limit is reduced, a small percentage of operators will 

choose to replace their IC engines with electric motors rather than retrofit with an 

emission control system. Based on this past experience, there would be two or three 

engines replaced by electric motors. It would be speculative, at best, to determine 

which engines would electrified, therefore the following compliance costs and cost 

effectiveness analysis do not include any cost-of-electrification scenarios. 
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The estimated total annual cost to retrofit 222 engines is a range between $12.3 million 

and $27.1 million annually. District staff believes that the lower cost number reflects 

smaller engines with situations that are relatively easy to retrofit and the higher number 

is more likely for large engines that need significant modification in order to install 

control equipment. 

Absolute cost effectiveness is the estimated total annual cost divided by the estimated 

emission reductions. District staff estimates that the overall cost effectiveness of the 

draft amendments is between $23,600 and $51,800 per ton NOx removed. A summary 

of the costs and cost effectiveness are shown in Table 4. 

Table 4 – Summary of Compliance Costs and Cost Effectiveness 

Rich-Burn Lean-Burn Overall 

Number Affected Engines 160 62 222

Total Cost ($/yr) a lower cost 

higher cost

--- 

$3,900,000

$8,400,000 - 

$23,200,000

$12,300,000 - 

$27,100,000

Cost Effectiveness b ($/ton NOx) --- 

$29,600

$21,600 - 

$59,300

$23,600 - 

$51,800

a

 Rounded to nearest $100,000 

b Rounded to nearest $100 

The incremental cost effectiveness is the difference in cost between successively more 

effective controls. For engines operating at least 6,750 hours annually, the NOx 

emission concentration limits are the most stringent available. For this reason, no 

incremental cost effectiveness analysis can be done because there is no more stringent 

option available for these engines. 

The incremental cost effectiveness for requiring engines operating less than 4,000 

hours per year to retrofit to meet a lower NOx limit was evaluated. Incremental cost 

effectiveness cannot be directly compared to the absolute cost effectiveness, but allows 

comparison between successively more stringent compliance options. In this case, the 

incremental cost effectiveness analysis focuses on limited-use engines and evaluates 

the difference between keeping the current NOx emission limit and requiring a lower 

NOx limit for these engines. The incremental cost effectiveness for limited-use engines 

is about $183,800 per ton additional NOx removed. 

VII. SOCIOECONOMIC IMPACT ANALYSIS 

Pursuant to California Health and Safety Code (CH&SC) 40728.5(a), “Whenever a 

district intends to propose the adoption, amendment, or repeal of a rule or regulation 

that will significantly affect air quality or emissions limitations, that agency shall, to the 

extent data are available, perform an assessment of the socioeconomic impacts of the 

adoption, amendment, or repeal of the rule or regulation.” As part of the District’s 

socioeconomic analysis process, a meeting of operators and other interested parties 
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Final Draft Staff Report: Rule 4702 (Internal Combustion Engines) August 18, 2011 

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was convened in September 2010 to discuss compliance costs and possible business 

responses to the proposed amendments. Using information gathered during Focus 

Group meeting and public comment period, a draft of the socioeconomic impact 

analysis report was presented during the June 2011 workshop for the rule. After 

receiving comments, the final socioeconomic impact analysis report has been published 

prior to the public hearing to consider rule adoption. The report is contained in 

Appendix D of this staff report. The public hearing is anticipated August 18, 2011. 

VIII. ENVIRONMENTAL IMPACT ASSESSMENT 

It is assumed that rich burn engines affected by this rule amendment already are 

equipped with NSCR. As such, there will be no GHG increase attributed to the richburn engine category at this time because there is no change to the control technology. 

For purposes of assessing environmental impact, District staff assumes that operators 

of the lean-burn engines affected by the draft rule amendments do not currently have 

SCR units, but will install SCR units as the control technology of choice in order to meet 

the rule’s stringent NOx emission limits. 

• SCR control technology can reduce the fuel efficiency of an engine by as much 

as 5%, meaning that 5% more fuel must be burned in order to have the same 

power output.

• Utilizing 5% as a conservatively high assumption for an engine's power penalty 

due to the use of an SCR system, and conservatively applying that power loss to 

the total rated horsepower of all engines affected by the rule changes (a total of 

123,886 bhp), there is an equivalent 6,194 bhp increase required to maintain 

current power levels.

• Using a conversion factor to convert the additional 6,194 hp to carbon dioxide 

equivalents (metric ton CO2-e), it is estimated that the installation of 62 SCR 

units will increase GHG emissions by 15,200 metric ton-CO2e/year.

• However, electrification as a method of compliance has the potential to offset any 

increases in GHG emissions. The District identified the number of engines 

subject to Rule 4702 that are needed to electrify to offset the potential increase in 

GHG emissions. The assessment demonstrated electrification of two to three 

engines would reduce the net increase in GHG emissions. See Appendix B for 

more details on the calculations. 

• Based on prior rule projects, electrification of two to three engines is a plausible 

compliance response to the rule requirements, offsetting the increased GHG 

emissions from the SCR. 

Thus, the District concludes that implementation of the proposed revisions would have a 

less than cumulative significant impact on global climate change. 

District staff concludes that there is no substantial evidence in the whole record before 

the District that the proposed amendments to Rule 4702 would cause any adverse 
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Final Draft Staff Report: Rule 4702 (Internal Combustion Engines) August 18, 2011 

20 Final Draft Staff Report with Appendices 

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effects on the environment. Pursuant to CEQA Guidelines §15063 (a), District staff will 

prepare an Initial Study and Negative Declaration for the project. Upon approval of the 

proposed amendments by the District’s Governing Board, District staff will file a Notice 

of Determination with each County Clerk within the boundaries of the District, CEQA 

Guidelines § 15075(d). 

IX. RULE CONSISTENCY ANALYSIS 

Pursuant to California Health and Safety Code Section 40727.2, staff has prepared a 

rule consistency analysis that compares the elements of Rule 4702 with the 

corresponding elements of other District rules and federal regulations and guidelines 

that apply to the same type of equipment or source category. The analysis is discussed 

in Appendix E of this staff report. District staff has concluded that Proposed Rule 4702 

is not in conflict with nor inconsistent with other District rules nor is Proposed Rule 4702 

in conflict with nor inconsistent with federal policy, rule, or regulations governing the 

same source category. 

X. OTHER ANALYSES 

A. Reasonably Available Control Technology (RACT) Analysis 

Sections 182(b)(2) and 182(f) of the federal Clean Air Act require ozone nonattainment 

areas to implement RACT for sources that are subject to Control Techniques Guidelines 

(CTG) documents issued by EPA and for “major sources” of VOCs and NOx, which are 

ozone precursors. RACT can be defined as devices, systems, process modifications, or 

other apparatus or techniques that are reasonably available, taking into account the 

necessity of imposing such controls in order to attain and maintain a national ambient 

air quality standard (NAAQS); the social, environmental, and economic impact of such 

controls; and alternative means of providing for attainment and maintenance of such a 

standard. These control techniques, which are defined in EPA guidelines for limiting 

emissions from existing sources in nonattainment areas, are adopted and implemented 

for nonattainment areas by state analysis. The following paragraphs evaluate the 

requirements of Proposed Rule 4702 in light of the RACT definition outlined previously. 

1. Emergency Engines and Low-Use Engines 

District staff is not proposing any changes to the exemption requirements for emergency 

standby engines and low-use engines. The existing requirements are consistent with 

ARB RACT/BARCT Determination for Spark-Ignited Engines and ARB Airborne Toxics 

Control Measures (ATCM). In addition, the ATCM is already being implemented 

through the District’s process for issuing Permits to Operate. The exemptions as 

outlined in the current rule represent RACT for these sources. 
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2. AO Spark-Ignited Engines 

District staff is not proposing any changes to the existing emission limits for AO sparkignited engines because the current limits have been recently implemented in January 

2009. 

In August 2007, EPA published the Technical Support Document (TSD)1 for the current 

version of Rule 4702 in conjunction with EPA’s full approval of the rule for inclusion into 

the State Implementation Plan (SIP). The TSD stated that SJVUAPD provided 

documentation for the process of determining BACM/BACT2 and in the staff report, 

provided analyses of the inventory of affected engines and the technological and 

economic feasibility of possible control technologies. The TSD also stated that EPA 

concurs with the BACM/BACT analysis, and noted that the emission limits and other 

provisions in submitted Rule 4702 are quite stringent when compared with the 

Determination and comparable rules in other air districts, and in light of the economic 

and social circumstances in the San Joaquin Valley.

In March 2010, EPA approved the District’s 1-Hour Ozone Plan (Federal Register/Vol. 

75, No. 44, March 8, 2010), which listed Rule 4702 as one of the NOx control rules that 

have been approved into the SIP. Therefore, the District believes that the recent 

approval of the 1-Hour Ozone Plan validated that EPA has accepted that existing Rule 

4702 constitutes RACT level. Since EPA’s approval of the District’s 1-Hour Ozone Plan 

in March 2010, there has been no further advancement in control technologies that 

would be feasible for use on agricultural engines. 

As previously stated, owners of AO engines have just recently installed emission control 

systems to meet the current emission limits effective January 2009. The control 

systems included a 3-way catalytic converter, air/fuel ratio controller, and oxygen 

sensor. The District are still evaluating the effects and other technical operational 

problems associated with this type of control system because of the conditions they 

were installed such as remote locations, fluctuations in gas pressures, and unattended 

operations, which make it more difficult to constantly monitor the emissions level during 

day-to-day operation of the engines. The District will be evaluating the long-term 

effectiveness of the currently installed emission control system for possible future rule 

amendments on AO engines. The currently installed controls give the District a better 

understanding if lower limits can be achieved under these conditions that exist in the 

farms. In addition, the District would also pursue incentive program route to addressing 

agricultural pumping engines any further than has already been accomplished. 

For example, the On-Road Heavy-Duty Diesel Vehicles (In-Use) Regulation and the InUse Mobile Agricultural Equipment Regulation are going to place very significant 

economic burden on the agricultural industry. Furthermore, in order to give agricultural 

 

1

 Technical Support Document for EPA’s Notice of Proposed Rulemaking and Direct Final Rule for the 

California State Implementation Plan – San Joaquin Valley Unified Air Pollution Control District Rule 4702 

(Internal Combustion Engine – Phase 2), August 2007. 

2

 The TSD stated that BACM includes BACT in the same way as RACM includes RACT. 
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22 Final Draft Staff Report with Appendices 

 For Proposed Amendments to Rule 4702 

operators some return on their capital investment, the District does not want to impose 

new lower limits for agricultural engines at this time. District staff believes that the 

existing Rule 4702 emission limits for agricultural engines meets RACT. 

3. Compression Ignited Engines (AO and non-AO) 

The existing emission limits for compression-ignited engines apply to both nonagricultural and agricultural engines. It should be noted that certified Tier 1 or Tier 2 

diesel engines are required to comply with EPA certified Tier 4 by January 1, 2015 or 12 

years after installation date, whichever is later. Non-certified diesel engines that are 

required to meet either Tier 3 or Tier 4 depending on the engine size and its operating 

hours have just began complying with the existing emission limits early this year, and 

some of the larger engines will need to comply by mid-2011. Engines greater than 500 

hp that operate at least 1,000 hours annually were required to meet 80 ppmv NOx last 

January 1, 2008 or by January 1, 2010, if the owner has an agreement to replace the 

diesel engine with electric motor. For this reason, District staff believes that the current 

emission limits represent RACT for compression ignited engines. 

4. Limited-Use Non-AO Spark Ignited Engines (Rich-Burn and Lean-Burn) 

District staff evaluated stationary engines that operate less than 4,000 hours annually 

and compared the cost effectiveness for the limited-use engines and full-time use 

engines. Since limited-use engines have fewer emissions on an annual basis, the cost 

effectiveness for a limited-use engine is higher than for a full-time engine. For this 

reason, the draft rule includes a separate category for limited-use engines that keeps 

the current emission limit, which, as discussed earlier, meets RACT. 

5. Waste Gas Fueled Non-AO Spark Ignited Rich-Burn Engines 

The current NOx limit in Rule 4702 for non-AO waste gas fueled rich-burn engines is 50 

ppmv (at 15% O2) or 90 percent reduction. Although SCAQMD Rule 1110.2 specifies a 

NOx limit of 11 ppmv for landfill gas or digester gas fired engines effective July 1, 2012, 

Rule 1110.2 includes a provision to complete a technology assessment by July 2010 

and that the limit will only be implemented if the result of SCAQMD’s technology 

assessment that is confirms that 11 ppmv is indeed achievable. In a recent telephone 

conversation with South Coast AQMD staff, District staff has found that the technology 

assessment would not be completed until next year. Therefore, District staff is not 

proposing any change to the current limit for non-AO waste gas fueled rich-burn 

engines until such time that South Coast AQMD’s technology assessment confirms that 

it is technologically and economically feasible to achieve the rule limit. 

 
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6. Cyclic Loaded Field Gas Fueled Non-AO Spark Ignited Rich-Bun Engines 

As noted earlier in this report, cyclic-loaded, field gas fueled engines can achieve some 

level of control, but not the very stringent control that can be imposed on engines that 

operate in a narrow range of loads. The exhaust gas temperature of cyclic loaded 

engines varies as a function of the engine load. Catalyst chemistry depends on a 

minimum temperature to be effective. When the cyclic load engine is operating in an 

engine load range that the exhaust gas is in the catalyst’s effective range, the emissions 

are well-controlled, but as the engine cycles out of the “sweet spot,” NOx control is less. 

Eventually, the exhaust gas temperature can be too low for any effective control. For 

this reason, District staff believes that the current emission limit fulfills RACT. 

7. 2-Stroke Engines Less than 100 hp Non-AO Spark Ignited Lean-Burn Engines

There is no technology for these engines that will allow a lower NOx level. District staff 

believes that the current emission limit for 2-stroke engines less than 100 hp fulfills 

RACT. 

8. Lean-Burn Engine Used For Gas Compression 

Most large natural gas-fired lean-burn IC engines in the region are in natural gas 

distribution and storage service and these engines experience frequently changing load 

conditions. In the technical support document for the EPA’s 2003 NOx SIP call, the 

EPA stated that there is an insufficient basis currently to conclude that SCR is an 

appropriate technology for the large lean-burn engines used for gas compression. The 

proposed emission limit is achievable through low-NOx combustion technology, which 

includes changes to the engine’s timing, enhanced control of the air-fuel ratio and other 

changes that lower NOx emissions. For this reason, District staff believes that the 

proposed emission limit for these engines fulfills RACT for this source category. 

9. Non-AO Spark Ignited Engines, Not Listed (Rich-Burn and Lean-Burn) 

The proposed emission limit of 11 ppmvd for non-AO spark ignited engines is more 

stringent than RACT since the engines in question would be required to install 

advanced add-on controls in order to meet the proposed limit. The proposed emission 

limit goes beyond RACT for this source category. 

10. Consideration for Prohibitory Rules in Other California Air Districts: South Coast 

AQMD Rule 1110.2 (Emissions from Gaseous - and Liquid-Fueled Engines) 

In considering what benchmarks to use for RACT, it is important to evaluate other 

emission limits that have been imposed on the same source category. District staff 

reviewed South Coast AQMD Rule 1110.2, which covers the same source category as 

District Rule 4702. South Coast AQMD Rule 1110.2 has stringent NOx, CO, and VOC 

emission limits for internal combustion engines. 
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24 Final Draft Staff Report with Appendices 

 For Proposed Amendments to Rule 4702 

While on the surface it would appear that the South Coast AQMD rule is more stringent, 

the medium and large operators in the South Coast Air Basin are most likely part of the 

South Coast RECLAIM program and therefore, not meeting the emission limits outlined 

in the South Coast AQMD rule. All facilities that emit more than a certain amount of 

pollution are required to be in the RECLAIM program. Certain companies receive 

emission allocations every year. Each allocation is good for 12 months. The portion of 

the allocation not needed to offset the operator’s own emissions can be sold to other 

companies. If the operator does not receive an emission allocation, they must buy 

emission credits from operators with unused emission allocations. In this way, the 

RECLAIM program is similar to a cap-and-trade program. At this time, the District is not 

planning a RECLAIM-type program for this source category. Instead a fee payment 

program in lieu of complying with the very stringent NOx limits is proposed. District staff 

believes that the current rule limits fulfill RACT, as evidenced by the recent approval of 

the current version of Rule 4702 by EPA. The proposed limits are beyond RACT and 

fulfill the state mandate for all feasible measures. 

11. Conclusion 

Since the previous rule was determined to meet RACT and this amendment further 

strengthens the rule requirements, this rule is expected to satisfy RACT, if not go well 

beyond RACT. 

B. Consideration for the Condensable Fraction of PM2.5 

Certain high-temperature processes emit gaseous pollutants that rapidly condense into 

particle form in the ambient air. After January 1, 2011, areas that are nonattainment for 

the National Ambient Air Quality Standard (NAAQS) for PM2.5 are to consider the 

condensable fraction of directly emitted PM2.5 for purposes of establishing the 

emissions limits for: 

• Reasonable Further Progress (RFP), in which an area shows continuous 

reductions of directly emitted PM2.5 and precursors, with sufficient emissions 

reductions to demonstrate attainment by the applicable deadline

• Reasonably Available Control Technology (RACT) and Reasonably Available 

Control Measures (RACM), in which a nonattainment area shows that it is 

adopting technologies and measures reasonably available, considering technical 

and economic feasibility; sufficient to demonstrate expeditious attainment; and 

meet RFP. 

(Code of Federal Regulations Title 40 Section 51.1002(c))

The District established emissions limits for its attainment, RFP, and RACT/RACM 

demonstrations in the 2008 PM2.5 Plan for the PM2.5 NAAQS as set by EPA in 1997. 

The District continues to evaluate condensable particulates and other directly emitted 

PM2.5 to improve its PM2.5 emissions inventory for future attainment plan efforts. 
SAN JOAQUIN VALLEY UNITIFED AIR POLLUTION CONTROL DISTRICT 

Final Draft Staff Report: Rule 4702 (Internal Combustion Engines) August 18, 2011 

25 Final Draft Staff Report with Appendices 

 For Proposed Amendments to Rule 4702 

Specific emission reduction targets for Rule 4702 were neither included in, nor does this 

action impede, the emissions limits set in the 2008 PM2.5 Plan. The District is not 

currently aware of significant uncontrolled condensable PM2.5 emissions or related 

condensable PM2.5 emissions control technologies for the sources affected by this 

amendment. Therefore, the District has satisfied any applicable requirement to 

consider condensable particulates from this source at this time. 

XI. REFERENCES 

1. California Air Resources Board: Determination of Reasonably Available Control 

Technology and Best Available Retrofit Control Technology for Stationary SparkIgnited Internal Combustion Engines. November 2001. 

2. South Coast Air Quality Management District: Rule 1110.2 (Emissions from 

Gaseous- and Liquid- Fueled Engines). February 1, 2008. 

3. South Coast Air Quality Management District: Final Staff Report for Proposed 

Amended District Rule 1110.2 (Emissions from Gaseous- and Liquid- Fueled 

Engines). December 2007. 

4. U.S. Environmental Protection Agency: Alternative Control Techniques Document 

– NOx emissions from Stationary Reciprocating Internal Combustion Engines. 

EPA-453/R-93-032. July 1993. 

5. U.S. Environmental Protection Agency: Code of Federal Regulation Title 40 Part 

51 Subpart U (Economic Incentive Programs)

6. U.S. Environmental Protection Agency: Code of Federal Regulations Title 40 

Section 51 Subpart Z (Provisions for Implementation of PM2.5 National Ambient Air 

Quality Standards).

7. U.S. Environmental Protection Agency: Technical Support Document for EPA’s 

Notice of Proposed Rulemaking and Direct Final Rule for the California State 

Implementation Plan – San Joaquin Valley Unified Air Pollution Control District 

Rule 4702 (Internal Combustion Engine – Phase 2). August 2007. 

8. U.S. Environmental Protection Agency: Stationary Reciprocating Internal 

Combustion Engines Technical Support Document for NOx SIP Call. October 2003 

 
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