Tennessee 

Gas Pipeline 

an Et Paso company 

June 30, 2004 

Robert Donaldson 

Department of Environmental Protection 

Business Compliance Division 

One Winter Street 

Boston, MA 02108 

Dear Mr. Donaldson: 

Tennessee Gas Pipeline Company (TGP) submits with this letter comments on the Massachusetts 

Department of Environmental Protection (DEP) proposed Air Quality Regulation 310 CMR 

7.26(40) - (44) (Proposed Rule). These comments supplement a list of initial concerns 

submitted by TGP in October 2003. The October 2003 comments were based on the review of a 

pre-draft version of the Proposed Rule and were submitted to the DEP at your request. Several 

of the comments submitted in October have been addressed in the Proposed Rule, and TGP 

appreciates the DEP's consideration of our earlier comments. In the attached comments on the 

Proposed Rule, TGP endorses several revisions included in the Proposed Rule. In addition, the 

attached comments address portions of the Proposed Rule that TGP believes require further 

consideration and revision. TGP's comments are based on our experience operating turbines and 

internal combustion (IC) engines on our natural gas transmission pipeline system throughout the 

United States. Some of these comments were expressed in the October 2003 correspondence, 

while others comments address issues not identified in that letter. 

TGP operates natural gas compressor stations in Massachusetts, and thus has an interest in 

ensuring achievable emission limits for new gas turbines and IC engines. Based on expectations 

that new gas turbines or IC engines will be installed at TGP facilities in the future to ensure the 

continued reliable delivery of clean-burning natural gas to Massachusetts and its neighboring 

states, TGP is concerned with several aspects of the Proposed Rule. In comparison to a pre-draft 

version of the rule, the Proposed Rule now includes language that allows turbines and IC engines 

in gas pipeline service to follow an alternative permitting process by filing a Comprehensive 

Plan Application (CPA) in lieu of complying with the presumptive limits in the Proposed Rule. 

However, comments are still warranted on issues related to the feasibility of the presumptive 

limits and other rule requirements, as well as the process that resulted in application of limits 

possibly feasible for electrical generating units (EGUs) to broader industrial classes, including 

gas transmission, without providing analysis and documentation to support such a conclusion. 

The Proposed Rule apparently is based on a Model Rule developed by the Regulatory Assistance 

Project (RAP), and similar documents from other states, that were developed specifically for 

"smaller-scale electrical generation resources." Based on our experience, emissions performance 

Tennessee Gas Pipeline 

Nine Gteenway Plaza Houston, Texas 77046 

tel 832.676.2600 
for turbines and IC engines in EGU service fail to reflect the unique operating profiles and load 

following requirements of similar equipment in pipeline service. Thus, emission limitations in 

the Proposed Rule derived from the RAP Model Rule and similar EGU-related guidance are not 

appropriate for application to turbines and IC engines in pipeline service. While the CPA 

process provides an alternative permitting process for equipment in gas transmission, the 

Proposed Rule implies that the emission limits are feasible for pipeline equipment, which is not 

appropriate. Ultimately, the Proposed Rule may serve as a regulatory guideline for other areas, 

and thus it is important that the Proposed Rule and associated support documentation properly 

reflect the feasibility of the proposed emission limits for non-EGU applications. TGP 

encourages DEP to ensure that the regulation includes explanatory text or support documentation 

that is relevant to non-EGU sources such as turbines and IC engines in gas transmission. 

We remain concerned that the rule, as proposed, will have the unintended effect of inhibiting the 

development of natural gas infrastructure in the Commonwealth. Given the growing demand for 

natural gas as the fuel of choice by businesses and state of the art EGUs, we believe it is 

appropriate that the rule promotes the use of proven control technologies, but it is inappropriate 

to be designed with emission limits based on future assumptions of technological advances. 

We appreciate the DEP's consideration of these comments, and offer our assistance in the 

development of the Proposed Rule. If you have any questions, please contact me at 832-676-

7446. 

Fiji C. George 

Principal / Air Group Lead, Eastern Pipelines 

Tennessee Gas Pipeline Company 

cc: Sandra Marlin, TGP 

Sam Clowney, TGP 

Jim Sinclair, TGP 

Steve Morawski, TGP 

Bob Hall, TGP 

W. Robert Keating, Commissioner, MA DTE 

David O'Connor, Commissioner, MA DOER 

2 

i 
Tennessee Gas Pipeline Company Comments on 

MADEP Draft Air Quality Regulation 310 CMR 7.20 

June 30,2004 

This document provides comments from Tennessee Gas Pipeline Company (TGP) on the 

proposed Air Quality Regulation 310 CMR 7.26(40) - (44) (Proposed Rule) developed by the 

Massachusetts Department of Environmental Protection (DEP) for control of emissions from 

new combustion turbines and reciprocating internal combustion (IC) engines. In October 2003, 

at DEP's request, TGP submitted a letter to the DEP identifying TGP's preliminary concerns 

with a pre-draft version of the Proposed Rule. These comments supplement our preliminary list 

of concerns from October. 

TGP operations in Massachusetts include four natural gas pipeline compressor stations that 

deliver natural gas to markets in the Northeast. Based on expectations that new gas turbines or 

reciprocating internal combustion (IC) engines will be installed at these facilities in the future to 

ensure the continued reliable delivery of clean-burning natural gas to Massachusetts and its 

neighboring states, TGP is concerned about the stringent limits in the Proposed Rule. Turbines 

and IC engines at compressor stations have unique operating profiles due to the fact that the units 

must respond to the demands of the pipeline, i.e., the units are load-following. Turbine and IC 

engines in pipeline service must have the flexibility to operate from very low loads to full load 

service, and equipment must respond to pipeline demands that can vary over this load range in a 

relatively short time frame. These pipeline operations differ from the typical operating 

conditions for other industries, such as electrical generation. As a result, achievable emissions 

performance and control technology applicability for turbines and IC engines in pipeline 

operations are different than similar units in electrical generation service. This distinction is due 

to the breadth of operating conditions typical for the "load following" profile in gas transmission, 

which contrasts the characteristic constant load operation that is required to feed power into the 

grid for electrical generating units (EGUs). 

In the October 2003 letter to DEP that identified an initial list of concerns with the pre-draft rule, 

TGP expressed concern regarding the proposed emission limits and the basis for these standards. 

That letter to DEP identified a number of issues, with the major issue the infeasibility of the 

emission limits and the improper migration of an EGU based model rule to other industrial 

operations. TGP is pleased that several issues raised in our October 2003 comments have been 

addressed in the Proposed Rule, including: 

• Addition of a provision that allows units at natural gas compressor stations an alternative to 

complying with the unachievable limits in the Proposed Rule. This alternative requires the 

operator to file a Comprehensive Plan Application (CPA) in lieu of complying with the 

Proposed Rule. 

• Removal of emission limits for particulate matter (PM) for all gas-fired equipment. The predraft version of the rule included PM limits for gas-fired combustion turbines. 

• Addition of a provision that indicates that compliance testing shall be conducted at full load 

conditions. 

1 
TGP supports these changes. However, TGP believes that comments on the Proposed Rule are 

still warranted in regard to several issues. TGP still is concerned with the presumptive emission 

limits, and the implication that these limits may be appropriate for equipment in natural gas 

transmission. While filing a CPA provides gas transmission companies an alternative 

mechanism for permitting new turbines or IC engines at compressor stations, TGP believes that 

the rule development process is flawed, in that a model rule and emission limits based on 

expected performance for EGUs have been inappropriately applied to all industrial categories of 

turbines and IC engines. Such an approach does not consider the effect that the application can 

have on equipment operation and performance, and establishes a poor precedent regarding the 

basis and support documentation and analysis associated with rulemaking. 

We encourage DEP to provide background documentation that identifies the process for this rule 

development, justifies the basis for presuming that EGU emission limits are appropriate for nonEGU applications - including variable load installations such as gas compressor stations, and 

clarifies the basis for any conclusions reached on whether non-EGU applications can achieve the 

presumptive standards. In addition, the DEP should consider that by not properly defining 

appropriate emission limits for non-EGU turbines and IC engines, these source categories are 

deprived the opportunity to comply with a presumptive-limit based regulation, and only left with 

the onerous option of case-by-case review under the CPA process. This may increase the 

permitting and compliance costs for non-EGU turbines and IC engines compared to their EGU 

counterparts. 

Our comments on the Proposed Rule are based on the wealth of experience that TGP offers 

regarding emissions performance and the application of emission controls for turbines and IC 

engines employed in gas transmission service. TGP is mainly concerned with possible 

misconceptions regarding the applicability of the emission limits to turbine and IC engines in gas 

transmission service. Additional comments are offered on topics of interest, although, unless the 

emission limits in the Proposed Rule change, TGP expects that new units at our facilities will 

have to use the CPA process. The issues identified by TGP regarding the Proposed Rule include: 

1. While units in gas transmission service can follow the CPA process in lieu of complying with 

the Proposed Rule, it is implied that the emission limits in the Proposed Rule are feasible. 

Thus, it is necessary to present a case against the proposed presumptive limits. Based on 

TGP experience, the NOx limits proposed are not achievable for IC engines and gas turbines 

in transmission service. The DEP should clarify this fact in support documentation, or 

provide evidence to the contrary. 

2. The DEP should consider developing appropriate presumptive emission limits for 

subcategories of equipment that include non-EGU industrial applications. 

3. The Proposed Rule should clearly indicate that the emission limits only apply at full load. 

4. The DEP has provided only minimal background information on the Proposed Rule. More 

detailed background should be made available to discuss the basis and achievability of the 

standards, and the environmental benefits derived from implementing the Proposed Rule. 

5. TGP discourages prescriptive emission limits in 2008, 2012, and beyond, and urges DEP to 

conduct a Technology Review in advance of each phase-in date to ensure that progress in 

2 

i 
emission reduction technology is commensurate with the forecast emission target and to 

allow public/stakeholder participation in the process. 

6. The Proposed Rule does not include many necessary implementation details. For example, 

compliance monitoring requirements are not defined. Monitoring provisions should be 

included that are based on the measurement or monitoring of operating parameters. In 

addition, other implementation issues, such as allowances during start-up and shutdown, 

should be addressed. Further, the manufacturer certification process should be eliminated or 

revised to provide a meaningful guarantee of performance, and the DEP should ensure that 

certification would not introduce unnecessary market constraints. 

7. The DEP has not provided any market-based options for compliance. TGP urges the DEP to 

consider such options, as it will enable companies to derive the most cost-effective solution 

for compliance. 

8. For emergency turbines and IC engines, the maximum annual hours of operation allowed 

under the Proposed Rule should be changed from 300 hours to 500 hours. A 500 hour 

operating limit is consistent with emergency generator definitions under EPA Title V 

guidance and regulations in many other States. 

9. The emission limit sections should add a provision that exempts operations from complying 

with the emission limits when unforeseen circumstances arise that are beyond the control of 

the operator. 

10. Additional requirements in the Proposed Rule should be deleted or clarified, with a clear 

indication of need and benefit, including requirements related to greenhouse gas emissions, 

stack height, and sound. 

Detailed Comments 

Comment 1: While units in gas transmission service can follow the CPA process in lieu of 

complying with the Proposed Rule, it is implied that the emission limits in the 

Proposed Rule are feasible. Thus, it is necessary to present a case against the 

proposed presumptive limits. Based on TGP experience, the NOx limits proposed 

are not achievable for IC engines and gas turbines in transmission service. The 

DEP should clarify this fact in support documentation, or provide evidence to the 

contrary. 

The Proposed Rule includes the CPA process as an alternative for permitting new units in gas 

transmission, rather than complying with the emission limits in the Proposed Rule. However, the 

Proposed Rule and associated background released for review implies that these emission limits 

are achievable for turbines and IC engines, and does not provide any analysis or discussion 

regarding the effect of industrial application and operating conditions on emissions performance. 

In addition, while the Proposed Rule is primarily based on the Regulatory Assistance Project 

(RAP) Model Rule, and similar guideline documents from other states that address requirements 

for EGUs, the DEP has not provided any analysis or documentation that identifies limitations 

associated with background documents. Since regulations frequently migrate to jurisdictions in 

other states or local districts, the Proposed Rule may serve as guidance or background for future 

regulations in other parts of the U.S. In addition, future review under the CPA process could be 

3 
complicated if it is presumed that the emission limits in the Proposed Rule are appropriate. 

Thus, the DEP should either provide the documentation that indicates that the proposed emission 

limits are achievable for non-EGU sources, or indicate that no such conclusion has been reached, 

and clearly explain the basis behind this position. This will help ensure that features and 

requirements of the Proposed Rule are not misconstrued in the future. 

Based on TGP's operating experience, dedication to research and development to advance 

technologies for gas transmission compressor drivers, and recent experience with state-of-the-art 

technology installations, TGP does not believe that the proposed NOx emission limit for either 

turbines or IC engines is achievable for units in gas transmission. In addition, TGP believes that 

the current status of technology development does not support a conclusion that the lower NOx 

emission limits proposed to phase-in for IC engines in 2008 and 2012 will be achievable for 

engines in gas transmission. Since achieving the NOx emission targets is likely contingent upon 

successful application of exhaust after treatment such as selective catalytic reduction (SCR), the 

TGP concerns are exacerbated by the knowledge that post-combustion emission controls, such as 

SCR, are unproven for equipment in gas transmission service. Additionally, when ultra-low 

NOx levels are required for rich-burn IC engines that use non-selective catalytic reduction 

(NSCR) for NOx control, the emissions of other exhaust constituents may be impacted. 

The emissions performance associated with application of emissions control technologies to 

. similar equipment can be impacted by factors such as the duty cycle of the unit, the type and 

quality of the fuel, and operational characteristics of the equipment (e.g., turbine versus IC 

engine, lean burn versus rich burn engine, spark-ignited versus compression ignition engine, 

etc.). A combination both equipment-based and operating-based variables will impact the choice 

of emission control and the emissions performance for various control technologies. It is not 

apparent that such issues have been considered in proposing the emission limits in the Proposed 

Rule - or if applications other than EGUs have even been thoughtfully considered. If the DEP 

has based the limits on EGUs, this fact should be clearly indicated, along with clarification on 

the lack of evidence regarding feasibility of these limits for non-EGU sources, such as gas 

transmission. 

TGP experience indicates that the proposed NOx emission limit is not feasible for units in gas 

transmission. While TGP can offer a wealth of evidence and data to support this position for 

turbines and IC engines in gas transmission, the following key issues summarize the application 

of post combustion controls - which will be necessary to achieve the emission levels in the 

proposed standard: 

• Application of SCR at a single turbine facility in gas transmission has been fraught with 

problems, including the need for extensive facility-specific re-engineering, a multitude of 

regulatory variances from the local agency, the replacement and reformulation of the catalyst, 

and, ultimately, the relaxation of emission limits for NOx and ammonia to levels 

significantly higher than the standards in the Proposed Rule. For example, the emission 

limits include an ammonia slip limit of 20 ppmv. Nearly ten years after its initiation, this 

facility has proven to be more of a research test bed for the catalyst vendor than a functional 

industrial facility operating with a feasible control technology. 

• SCR has not been demonstrated on load-following IC engines in gas transmission. One 

installation in California was decommissioned due to operational problems. In addition, the 

4 

i 
EPA has acknowledged that SCR is not a proven technology for load-following IC engines. 

Further, in attempting to adapt SCR to IC engines, technology vendors have introduced 

system changes that may increase the likelihood of emissions of deleterious nitrogen 

compounds such as ammonia, cyanide, and nitrous oxide. 

• NSCR-equipped IC engines will likely only achieve the proposed limit under select operating 

conditions. In addition, most gas transmission installations use lean burn engines, which 

offer operating cost, performance, and emission advantages. Further, recent research 

indicates that NOx reduction from rich-burn engines can coincide with increases in the 

emissions of species such as ammonia and nitrous oxide, especially when high levels of NOx 

reductions are required. These other nitrogen species are formed due to reactions that can 

occur under more fuel-rich operating conditions, resulting in NOx conversion to species 

other than the desired product - molecular nitrogen. Other species that can be formed 

include ammonia (NH3) and nitrous oxide (N2O), which have been measured in recent 

emission tests, and potentially cyanide species (CN). 

As lower NOx emissions are pursued under the Proposed Regulation, NSCR-equipped 

engines may appear to be a viable option for compliance with ultra-low NOx limits. 

However, the IC engine air-to-fuel ratio required to achieve the lowest NOx emissions must 

be more "fuel rich" (i.e., more oxygen deficient). This fuel rich environment is also the 

operating mode most conducive to increases in emissions of nitrogenous species such as 

ammonia. It is conceivable that nominal incremental reductions in NOx under such 

operations may actually result in a considerable, and perhaps nearly identical, incremental 

increase in emissions of other undesirable exhaust species. Such phenomena must be 

characterized, and these potentially collateral deleterious effects should be considered by the 

DEP in judging the "environmental benefit" from emission limits in the Proposed Rule. 

TGP can provide additional discussion and information on these topics if needed. In lieu of postcombustion controls, to minimize emissions from turbines and engines in compression service, 

lean premixed combustion is employed for gas turbines and low emission combustion is used for 

lean-burn IC engines. These controls, based on modifying the combustion process to minimize 

the amount of NOx created, are technically feasible for load-following gas transmission 

applications and result in substantial reductions in NOx. However, these technologies cannot 

achieve the NOx emission limit in the Proposed Rule. Lacking credible and documented 

information to the contrary, the Proposed Rule or associated support documentation should 

clearly indicate that the presumptive emission limits have not been proven feasible for non-EGU 

applications. 

Comment 2: The DEP should develop appropriate presumptive emission limits for 

subcategories of equipment that include non-EGU industrial applications. 

The presumptive limits in the Proposed Rule provide a regulatory target that reduces the burden 

associated with acquiring a permit using case-by-case review. In failing to consider appropriate 

limits for non-EGU turbines and engines, the DEP has not afforded operators in gas transmission 

the ability to avoid case-by-case review and thus likely increased permitting and compliance 

costs for this equipment relative to similar equipment in EGU applications. 

5 
The CPA alternative requires case-by-case review and does not include presumptive emission 

limits - which can simplify the permitting process. TGP is not aware of any subjective technical 

review that indicates the proposed NOx limits can be achieved for natural gas-fired units in gas 

transmission service. Thus, turbines and IC engines in gas transmission are not afforded the 

lesser permitting burden associated with complying with presumptive limits. Such an option is 

not available to gas transmission until the DEP undertakes an effort to provide appropriate 

emission limits for non-EGU sources, which would necessarily result in several application and 

equipment-specific subcategories of turbines and IC engines with associated emission limits. 

By failing to conduct a technical review of emission limit applicability to non-EGU sources, the 

DEP has not provided sources, such as gas transmission units, the opportunity to pursue the less 

costly permitting path afforded EGU units under the Proposed Rule. The DEP should develop 

presumptive limits for non-EGU industrial categories. TGP can participate in this process and 

provide information and data to support appropriate emission limits for equipment in variable 

load gas transmission service. 

Comment 3: The Proposed Rule should clearly indicate that the emission limits only apply at 

full load. 

The Proposed Rule has added a requirement in section 7.26(43)(e)(3)(c) to conduct the 

compliance test at the full design load of the IC engine or turbine. Due to questions about 

emissions performance at off-load conditions, TGP had suggested such a provision to the DEP in 

preliminary comments on the pre-draft regulation in October 2003. However, the next 

requirement in the Proposed Rule, in section 7.26(43)(e)(3)(d), provides the DEP the ability to 

require emissions or other testing to assure compliance. This provision could be interpreted to 

allow the DEP the require emission tests at conditions other the full design load. 

Experience shows that IC engine and turbine emission profiles and control effectiveness vary 

across equipment subcategories and as load varies, and there is often a tradeoff between 

emissions of NOx and CO. EPA has acknowledged the dependence of performance on operating 

load during the SIP Call process, and a wealth of data also establishes the impact of load on 

emissions of CO and NOx. Depending upon the pollutant, the equipment, and the load 

condition, the functional relationship between load and emissions can differ. 

For example, for a gas turbine, NOx typically decreases as load decreases, with an increase in 

CO possible. However, low emissions from current generation turbines have been achieved 

primarily through design advances to control air-fuel mixing. Typical turbine vendor guarantees 

for dry low NOx (DLN) combustion technology are provided for operation above 0°F and above 

50% rated load. Engineering design strives to achieve as broad of an effective operating range as 

possible, but typically focuses on optimizing emissions at full load. Thus, variable load and 

reduced load operation can result in less than optimal performance for at least some exhaust 

species. For current generation low NOx turbines, a pilot flame is typically used to ensure stable 

combustion during load changes and at reduced load, especially for industrial scale turbines. 

Reduced load events require an increase in the percent of the fuel fed to the pilot to ensure flame 

stability. The pilot flame combustion does not provide the same level of emissions performance 

as the primary flame. Thus, variable and reduced load events will result in less than optimal 

6 
emissions from gas turbines - and can include poorer emissions performance for some pollutants 

than what is typical at full load. 

The emission limits in the standard are apparently based on EGU performance, and are thus 

likely based on a nominal full load operating condition. If this is the case, the Proposed Rule 

should clarify that since the background information is based on full load conditions, emission 

limits only apply at full load, and that compliance tests should be conducted only at full load and 

the provisions in section 7.26(43)(e)(3)(d) are not intended to supersede this requirement. 

Comment 4: The DEP has provided only minimal background information on the Proposed 

Rule. More detailed background should be made available to discuss the basis 

and achievability of the standards, and the environmental benefits derived from 

implementing the Proposed Rule. 

The Proposed Rule includes only minimal background related to environmental benefits, and 

technical and economic justification for the regulation. More detailed documentation should be 

made available for review and comment that provides: 

• The justification for the proposed requirements; 

• The technical basis for the proposed emission limits; 

• The likelihood that technology advances will achieve the lower emission limits that phase-in 

over time; 

• The projected costs for control technology and compliance implementation; 

• The environmental benefit derived from the regulation. 

The introductory text released with the Proposed Rule provides generic claims of a "positive 

impact upon air quality" and compliance costs that will be no greater as projects meet up-to-date 

technology standards. However, there is no basis or justification for these statements. 

Since the Proposed Rule is primarily (if not solely) based on emission levels associated with 

EGUs, and does not consider complicating factors for other industrial applications, supporting 

background documentation is especially important. For example, more challenging operational 

requirements related to load variability may preclude the application of technology developed 

for EGUs, which operate with a more uniform load profile. While the Proposed Rule now 

includes a provision that allows non-EGU units to follow an alternative permitting process, the 

Proposed Rule and associated text imply that the emission standards are achievable for all 

industrial categories. Since regulatory precedent in a particulate state or region can migrate to 

other jurisdictions, it is important that the Proposed Rule does not imply inappropriate 

conclusions regarding non-EGU sources. 

In addition, there are circumstances that could impact the environmental benefit from the 

Proposed Rule. For example, increasingly stringent emission limits have resulted in some to 

conclude that "rich-burn" engines with NSCR offer environmental advantages over lean burn 

units, since NSCR is presumed to effectively decrease engine NOx. However, as discussed in 

Comment 1, when very low emission levels are required, it is possible that emissions of other 

7 
exhaust species such as ammonia and nitrous oxide will increase. In fact, it is possible that 

attempts to achieve marginal incremental reductions in NOx could trigger increases in 

deleterious species - and offset or negate any presumed environmental advantage. The potential 

for these emissions will increase under variable load operation. Such "trade-offs" should be 

recognized and properly considered by the DEP, rather than making the simple presumption of a 

positive impact upon air quality. 

At a minimum, the DEP should specifically include background that acknowledges the technical 

basis for the Proposed Rule. If EGU based performance serves as the basis for the emission 

levels, this should be reported. Lacking any specific data that indicates such performance can be 

achieved in other industrial applications, the DEP should clearly discuss this in support 

documentation for the Proposed Rule. This will provide historical documentation so that others 

can understand that inclusion of other industrial categories is not consistent with the RAP Model 

Rule, is counter to the current understanding of technology performance for industrial categories 

such as gas transmission, and was stipulated by the DEP without specific documentation to 

validate the feasibility of such assumptions. 

Comment 5: TGP discourages prescriptive emission limits in 2008, 2012, and beyond and 

urges DEP to conduct a Technology Review in advance of each phase-in date to 

ensure that progress in emission reduction technology is commensurate with the 

forecast emission target and to allow public/stakeholder participation in the 

process. 

The NOx emission limits for IC engines are based on forecast improvements in technology, and 

phase in incrementally lower emission limits in 2008 and 2012 (or about 3 and 7 years after the 

projected initial compliance requirement). The Proposed Rule includes a provision for a 

technology review in advance of the 2012 standard to determine if the proposed standards should 

be amended due to technology advancing at a slower pace than envisioned at the time of rule 

development. However, no such review is planned in advance of the 2008 standard. 

The emission targets proposed for equipment installed after 2008 are considerably lower than the 

limits for equipment installed after the initial regulatory deadline (currently stated as six months 

after the effective date), and control technology development is not evolving at a pace to support 

the proposed emission limits. Thus, a technology review analogous to the review required prior 

to the implementation of the 2012 (i.e., seven year) standard is also appropriate prior to 

implementation of the 2008 (i.e., three year) standard. A provision analogous to the provision 

for 2012 in 310 CMR 7.26(43)(b)(2) should be added to the Proposed Rule for 2008 to ensure 

that available technology can achieve the proposed standard. This review will also provide the 

opportunity to consider any operational constraints or technology limitations that have been 

identified during the implementation of the initial phase of the NOx standard. 

The basis for the increasingly stringent regulations is questionable, at best. It is notable that the 

proposed emission targets in the Proposed Rule are apparently drawn from the RAP Rule and 

similar efforts in other states. These efforts appear to base future year emission limits on 

aggressive research goals from prominent IC engine research programs. For example, the U.S. 

Department of Energy (DOE) Advanced Reciprocating Engine Systems (ARES) program has a 

8 
2010 research target of 0.10 grams/bhp-hr of NOx (0.3 lb/MW-hr). An interim goal for 2004 is 

demonstration of NOx emissions of 0.25 g/bhp-hr. Similarly, the California Energy Commission 

(CEC) has implemented the Advanced Reciprocating Internal Combustion Engines (ARICE) 

research program that includes a 0.10 g/bhp-hr goal for NOx emissions in 2010, with a stretch 

goal of 0.05 g/bhp-hr. These levels are similar to the Proposed Rule NOx limits for IC engines 

of 0.3 lb/MW-hr in 2008 and 0.15 lb/MW-hr in 2012. 

With phased-in emission limits in future years similar to goals from long-term research and 

development programs, it is appropriate to contemplate the probability of success and the 

timeliness of R&D progress when considering whether a technology review is appropriate prior 

to phasing in any lower emission limit. Experience indicates that any objective review of multiyear developmental programs will conclude that research targets for technology advancement are 

seldom achieved, and, at a minimum, are typically not achieved within the timeframe forecast at 

the initiation of a long-term research program. Such long-term goals are typically intended to 

aggressively drive technology forward, and the goals are often recast as the program proceeds to 

better reflect the fundamental issues and application challenges that are discovered as the 

research program unfolds. 

TGP questions the basis for the scheduled phase-in emission requirements in the Proposed Rule, 

and all regulatory phase-ins should be preceded by a technology review to assess whether the 

presumed progress in technology advancements has been achieved. However, TGP strongly 

urges the DEP to refrain from prescribing futuristic emission limits in any rulemaking. Instead, 

TGP recommends completing technology reviews in 2008,2012, and subsequent 5-year review 

cycles, with ample opportunity for public participation and input. 

Comment 6: The Proposed Rule does not include many necessary implementation details. For 

example, compliance monitoring requirements are not defined. Monitoring 

provisions should be included that are based on the measurement or monitoring of 

operating parameters. In addition, other implementation issues, such as 

allowances during start-up and shutdown, should be addressed. Further, the 

manufacturer certification process should be eliminated or revised to provide a 

meaningful guarantee of performance, and the DEP should ensure that 

certification would not introduce unnecessary market constraints. 

Regulations that include emission standards for specific categories of equipment typically 

include provisions that address implementation and compliance issues, including compliance 

testing, monitoring requirements, and definition of exempt operations or allowances provided 

during events such as startup and shutdown. Currently, the Proposed Rule includes only minimal 

reference to potential monitoring or compliance testing requirements. In addition, the Proposed 

Rule does not discuss startup and shutdown, or other events that should be exempt from meeting 

emission limit requirements. The Proposed Rule should better define such implementation 

issues. Finally, certification per 310 CMR 7.26(43)(e)(l) presents a vendor requirement that 

may not be addressed in the current marketplace and does not define the conditions or constraints 

(e.g., operating load) under which the certification applies. 

9 
Compliance Testing 

The testing provisions in 310 CMR 7.26(43)(e)(3) indicate that compliance tests must follow 

EPA, California Air Resources Board (CARB), or equivalent test methods. However, the 

specific methods are not referenced. Further, additional details related to the requirements for 

conducting a compliance test are lacking. If the intent is to require operators of new equipment 

to conduct an initial performance test and/or subsequent compliance testing, the timing and 

requirements for these tests should be specifically identified in the regulation, including items 

such as test methods for each regulated pollutant, test planning and reporting, and schedule for 

test completion. The Proposed Rule should be revised to clarify the compliance test 

requirements for subject equipment. 

Monitoring 

The monitoring provisions in 310 CMR 7.26(43)(e)(2) only note that the DEP may require 

emissions monitoring or other monitoring for compliance assurance. The Proposed Rule should 

be revised to include more specific detail on monitoring requirements or options. Since recent 

federal actions indicate that EPA accepts the monitoring of operating parameters for compliance 

assurance, the regulation should allow operators to fulfill monitoring requirements using 

parameter-based monitoring. 

For example, the federal Phase II NOx SIP Call includes provisions for the reduction of NOx 

that will affect IC engines at gas pipeline compressor stations and storage facilities. In 

developing the requirements for the Phase II NOx SIP Call, EPA has considered recent 

information that is contrary to some of the previously available information on NOx emissions 

and control performance for equipment in gas transmission service. This has resulted in changes 

to the requirements in original NOx SIP Call, and EPA's current thinking is reflected in the 

Phase II NOx SIP Call. 

The Phase II NOx SIP Call, Interstate Ozone Transport: Response to Court Decisions on the 

NOx SIP Call, NOx SIP Call Technical Amendments, and Section 126 Rules; Final Rules 

(69 FR 21604), was finalized on April 21, 2004. Prior to this, due to the ongoing evolution of 

the EPA position and the timing of NOx reductions being considered in SIP Call states, on 

August 22, 2002, EPA released a Guidance Memorandum. The Memorandum from Ms. Lydia 

Wegman, Director, EPA Air Quality Strategies and Standards Division, Office of Air Quality 

Planning and Standards, was entitled, State Implementation Plan (SIP) Call for Reducing 

Nitrogen Oxides (NOx)--Stationary Reciprocating Internal Combustion Engines, and addressed 

to Air Division Directors at EPA Regional Offices. The final Phase II Rule and this memo 

provide EPA's current thinking and encourages states to provide flexibility in the 

implementation of engine NOx reduction strategies. A copy of the EPA memo is attached to 

these comments. In addition to discussing emissions and recommending regulatory flexibility, 

the final rule identifies acceptable approaches for compliance monitoring: 

".. .acceptable monitoring is not limited to those monitoring methods such as continuous or 

predictive emissions measurement systems that rely on automated data collection from 

instruments. Non-automated monitoring may provide a reasonable assurance of 

compliance for IC engines provided such periodic monitoring is sufficient to yield reliable 

data for the relevant time periods determined by the emission standard." (69 FR 21622) 

10 
In addition, in recent MACT standards, EPA has proposed periodic testing and monitoring of 

operating parameters for a variety of source types. For example, the combination of parameter 

monitoring and periodic testing is consistent with the monitoring approach that has been selected 

by EPA in a number of MACT standards that contemplate the use of catalytic devices to control 

emissions. Similar control devices may be necessary to comply with the proposed CO and VOC 

emission limits. 

The Proposed Rule should be revised to include more specificity regarding acceptable options 

for compliance monitoring, and the approaches accepted should include parameter monitoring. 

Exempt Practices 

The Proposed Rule provides no language related to standard operating conditions that cannot 

achieve the proposed emission limits, or how such events would be addressed. For example, 

regulations for turbines typically include provisions regarding startup and shutdown events. It is 

commonly accepted that emissions are higher for some period during startup and shutdown, thus 

exemption from complying with the emission limits is necessary during this time period. In 

addition, it is well established that load changes and reduced load operation result in different 

emission profiles then operation at nominal full load conditions. It is imperative that the 

Proposed Rule includes definitions for relevant operational events, and clarifies applicability and 

constraints regarding emission performance requirements during common operational events. 

Certification 

In subsection 310 CMR 7.26(43)(e)(l), certification requirements are presented that include a 

statement from the engine or turbine manufacturer that the unit, "is capable of complying with 

the emission limits for 15,000 hours of operation or the first 3 years of operation." Such a 

statement has little relevance unless associated operational constraints and materials that support 

the claim are better defined. In addition, all manufacturers may not be positioned or willing to 

fulfill such a requirement. The DEP should consider the burden that such a requirement, in a 

single state, will place on vendors and operators. Additionally, the DEP should consider the 

potential for the requirement to limit the turbine market available to operators based not on 

actual performance, but vendor decisions to forego sales in a single state rather than fulfill this 

requirement. In fact, it is appropriate for the potential market impacts associated with emissions 

certification to be included in discussion of the economic impacts of the Proposed Rule. 

Regarding the certification statement, it is possible that a turbine or IC engine may achieve the 

emission limits in some instances, but not others. For example, there may be cases when such 

performance is only possible at rated load with nominal ambient conditions. The certification 

statement in the Proposed Rule does not appear to require the definition of any such constraints. 

In addition, a statement that a unit "is capable" of achieving a performance target is not a 

definitive requirement. Any meaningful certification should be commensurate with a 

performance guarantee and require manufacturers to state that, within a defined set of operational 

constraints, the unit "will" comply with the standard. Lacking such commitment from the 

manufacturer, certification will only provide a false assurance of equipment performance. 

11 
If the regulation is to require certification, the DEP should ensure that turbine and IC engine 

vendors would commit to a meaningful certification process in a timely fashion. Lacking such 

commitment from the vendors, the certification process could result in hollow promises 

regarding emissions performance. Additionally, this requirement could introduce market factors 

that will result in increased costs for operators that need to procure new equipment. 

Comment 7: The DEP has not provided any market-based options for compliance. TGP urges 

the DEP to consider such options, as it will enable companies to derive the most 

cost-effective solution for compliance. 

The implementation of market-based reductions for stationary source emissions has been 

successful under the Clean Air Act Amendments of 1990. Market-based programs, such as the 

Acid Rain Program and OTC NOx Budget Program have succeeded in the cost-effective 

implementation of emission reductions to improve air quality. The NOx SIP Call Budget 

Program will continue the use of market-based reductions of NOx emissions for control of ozone 

precursor emissions in the eastern U.S. 

Massachusetts has a successful market-based program for certification of Mass Bank ERCs. For 

example, these ERCs can be used to achieve equivalent mass emissions compliance with existing 

NOx RACT limits. In fact, this compliance strategy has been employed for RACT compliance 

on a turbine at TGP's Compressor Station 264 in Charlton, MA. Requirements of NOx RACT 

can also be met via emission averaging, per 310 CMR 7.00 Appendix B(4). Since flexible 

approaches have been deemed acceptable for NOx RACT cases, a similar degree of flexibility 

should be provided to comply with the requirements of the Proposed Rule. 

In the Proposed Rule, requirements for stationary IC engines and turbines do not provide 

operators the benefits and flexibility provided by market-based or flexible control options. For 

example, flexibility could allow a regulated source to choose to install control on a particular unit 

if warranted, or consider factors such as equipment utilization rates and opt to purchase NOx 

allowances if this offers a more cost-effective solution. Additionally, emissions averaging within 

a facility or a company will also provide the flexibility that allows operators to choose the 

control options that make the most economic sense, without sacrificing environmental 

performance. 

Comment 8: For emergency turbines and IC engines, the maximum annual hours of operation 

allowed under the Proposed Rule should be changed from 300 hours to 500 hours. 

A 500 hour operating limit is consistent with emergency generator definitions 

under EPA Title V guidance and regulations in many other States. 

The Proposed Rule establishes requirements for emergency IC engines and turbines in 310 CMR 

7.26(42). Subsection (d)(1) states that emergency units shall not be operated more than 300 

hours during any rolling 12-month period. This "definition" of emergency generator is different 

than the 500 hour criterion that has become fairly standard in regulatory definitions throughout 

the United States. For example, a number States agencies and local districts use 500 annual 

12 
hours as the maximum for emergency units. In addition, guidance issued by EPA for 

"emergency generators" under the Title V program indicates that 500 hours is an appropriate 

default assumption for emergency generators. With the standard limitation in place throughout 

the U.S., there has never been an indication that the 500 hour limit has resulted in operations that 

were not necessary or were somehow trying to take advantage of the 500 hour allowance. For 

consistency with the standard regulatory definition of "emergency generator", the Proposed Rule 

should change the 300 hour criteria in subsection (d)(1) to 500 hours. 

The lower criteria in the Proposed Rule is not necessary, as other provisions provide assurance 

that emergency units are not operated unless the situation demands operation. For example, 

section 7.26(42)(a) indicates that load shaving units, peaking power units, and units in an energy 

assistance program are not emergency units. Section 7.26(42)(d)(2) requires that operation and 

maintenance (e.g., occasional start-up for testing) be conducted consistent with the 

manufacturer's recommended procedures. The definition of "emergency" in section 7.26(41) 

specifically identifies the situations that are considered an emergency and thus when the unit can 

be operated. Thus, with operation of emergency units limited by other provisions in the 

Proposed Rule, it is not necessary to introduce an hour-based threshold that differs from 

established practice. 

Emergency generator limits have typically been based on 500 hours throughout the United 

States. In addition, other provisions provide clear limitations that prevent unnecessary operation 

of emergency engines and turbines. Thus, the DEP should change the allowed hours of 

operation for emergency units to 500 hours. 

Comment 9: The emission limit sections should add a provision that exempts operations from 

complying with the emission limits when unforeseen circumstances arise that are 

beyond the control of the operator. 

The Proposed Rule includes very stringent emission limits that become more difficult to achieve 

as the emission standards decrease over time. As emission limits become more stringent, the 

possibility increases that unforeseen circumstances could result in an impact on operational 

performance that results in a short-term increase in emissions above the emission limit. The 

Proposed Rule should include a provision that provides an exception for complying with the 

emission limits when emission performance is impacted by circumstances that are beyond the 

control of the operator. Exceptions would be limited to those situations that arise from sudden 

and reasonably unforeseeable events beyond the control of the operator. 

To address exceptions, the Proposed Rule should add a provision to section 7.26(42)(b)(3) and 

section 7.26(43)(b)(5). This "exception provision" should indicate that short term emissions 

increases above the emission limit that are unavoidable are not subject to the emission limits if 

the emission increase is due to a situation arising from a sudden and reasonably unforeseeable 

event beyond the control of the operator, such as acts of God. The exempt events would not 

include noncompliance caused by circumstances within the control of the operator, such as 

' September 6, 1995 Memorandum, "Calculating Potential to Emit (PTE) for Emergency Generators", from John 

Seitz, Director, EPA Office of Air Quality Planning and Standards 

13 
improperly designed or installed equipment, lack of preventive maintenance, careless or 

improper operation, or operator error. The provision can include a requirement that the operator 

does everything reasonably available to ensure that excess emissions are minimized. In addition, 

a reporting and recordkeeping requirement can be added to the Proposed Rule to ensure that any 

such events are reported to the DEP. 

Comment 10: Additional requirements in the Proposed Rule should be deleted or clarified, with 

a clear indication of need and benefit, including requirements related to 

greenhouse gas emissions, stack height, and sound. 

The requirements related to several provisions in the Proposed Rule lack clarity, or their intent 

and need is not identified. These provisions include greenhouse gas emission requirements, 

stack height requirements, and sound requirements. The rule should delete these requirements or 

clarify the intent, need, and benefit of each requirement. 

Greenhouse Gas Emissions 

There is currently not a regulatory requirement in the United States for emissions of greenhouse 

gases (GHGs) such as carbon dioxide. Actions that have been undertaken have been voluntary 

and premised on an open-market or emissions trading type of approach. The DEP should clarify 

the intent and need for this requirement, and provide background that supports the standard and 

the prescriptive approach. Since other initiatives are underway that will likely initiate GHG 

programs in northeast states including Massachusetts, including this issue in the Proposed Rule is 

premature and may ultimately conflict with or be counter-productive to the implementation of 

other initiatives that are focused on GHGs. 

Should DEP proceed with plans to regulate or control greenhouse gases, a market-based 

approach should be adopted. Prescriptive requirements on a unit level stifles creative programs 

that have proven to be successful as part of the Acid Rain and NOx Budget Allowance programs. 

In addition, global climate change associated with GHG emissions is not a localized air quality 

problem, i.e., any potential impact occurs on a much broader scale and does not warrant unit or 

facility specific prescriptive measures. 

"Command and control" unit level limits can ignore practices or projects undertaken by a 

company on other emissions or process equipment within the state and/or the country. TGP 

opposes any specific unit-level or facility-level emission limit on any greenhouse gas pollutant. 

Any attempts to regulate such pollutants should be backed by adequate technical and scientific 

data, and be modeled after successful policies and regulations based on market-based 

approaches. In addition, in introducing GHG requirements in Massachusetts, the DEP should 

provide a clear "road map" on its GHG implementation and compliance strategies - both in the 

near-term and long-term, and identify how these limits will be integrated into other programs 

currently under consideration in the northeast U.S. 

Stack Height 

The DEP should clarify the basis for requiring and defining stack height requirements in 310 

CMR 7.26(43)(d)(3). In addition, in 310 CMR 7.26(43)(d)(3)(a), reference to the term 

14 

i 
"condition of air pollution" should be deleted or the term should be clearly defined. Subsections 

(3)(b) and (3)(c) include specific requirements related to stack parameters, and subsection (3)(d) 

indicates circumstances that require modeling to determine if impacts exceed a National Ambient 

Air Quality Standards (NAAQS), and provide a clear indication of requirements. The provisions 

in subsection (3)(a) are ambiguous and subject to interpretation. Thus, this section should be 

clarified. The best solution is to delete text referring to "a condition of air pollution". 

Sound 

The DEP should clarify requirements for "sound" limitations, which are ambiguous. The 

Proposed Rule currently requires operations to comply with the noise requirements in 310 CMR 

7.10, but these requirements are unnecessarily vague. When installing new IC engines or gas 

turbines at compressor stations, standard industry practices are employed to limit the noise that 

emanates from the operating equipment. These practices can include the use silencers to 

attenuate noise from intake and exhaust lines, and sound insulation for buildings that enclose the 

equipment. 

The cited noise requirement does not provide any specific indication of the type or degree of 

noise control that is required, performance criteria, or measurement methods or practices to 

validate acceptable performance. While 310 CMR 7.10 may have been developed for broad 

applicability and thus includes general text, the Proposed Rule specifically addresses engine and 

turbine applications. Thus, it is appropriate for noise requirements to specify practices or 

requirements that are the norm for such industrial installations, or, alternatively, delete this 

requirement from the regulation. 

Attachment: Memorandum from Ms. Lydia Wegman, Director, EPA Air Quality Strategies 

and Standards Division, Office of Air Quality Planning and Standards, State 

Implementation Plan (SIP) Call for Reducing Nitrogen Oxides (NOx) - Stationary 

Reciprocating Internal Combustion Engines, August 22, 2002. 

15 
< • —' 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

RESEARCH TRIANGLE PARK, NC 27711 

AUG % 2 2002 

MEMORANDUM 

OFFICE OF 

AIR QUALITY PLANNING 

AND STANDARDS 

SUBJECT: State Implementation Plan (SIP) Call for Reducing Nitrogen Oxides (NOx)--

Stationary Reciprocating Internal Combustion Engines 

The purpose of this memorandum is to provide guidance to Slates that choose to adopt 

rules covering stationary reciprocating internal combustion engines (IC engines) as part of their 

response to the NOx SIP call. Although the schedule for submittal of the SIPs addressing IC 

engines under the NOx SIP call is the subject of on-going rulemaking, I am aware that several 

States are taking steps toward compliance with the requirements of the SIP call. This 

memorandum addresses questions on the IC engine source category that have been raised 

recently by several States as well as by the affected industry in various discussions and meetings. 

Specifically, EPA is providing guidance on the following issues related to IC engines: State 

flexibility, periodic monitoring, new source review, and early reductions. The EPA is also 

clarifying that the guidance in this memorandum reflects EPA's current views and supersede the 

views underlying the proposed requirements in the Federal implementation plan proposed 

October 21.1998 regarding IC engines. This guidance is effective immediately. 

Stale Flexibility 

For purposes of complying with the NOx SIP call, a State is free to choose whatever mix 

of controls will meet its budget and is free not to regulate IC engines at all. Where States choose 

to regulate large IC engines, EPA encourages the States to allow owners and operators of large 

IC engines the flexibility to achieve the NOx tons/season reductions by selecting from among a 

variety of technologies or a combination of technologies applied to various sizes and types of IC 

engines. Flexibility would be helpful as companies take into account that individual engines or 

engine models may respond differently to control equipment. That is, while certain controls are 

known to have a specific average control effectiveness for an engine population, some individual 

engines that install the controls would be expected to be above and some below that average 

control level, simply because it is an average. Available technologies include combustion 

modifications, such as pre-combustion chambers or high energy ignition, and post-combustion 

controls, such as non-selective catalytic reduction. 

FROM: I ,ydia N. Wegman, Director tOL^-^l 

Air Quality Strategies and Standards' Division 

TO: Air Division Director 

Regions I-V & VII 

Internet Address (URL) • http://www.epa.gov 

Recycled/Recyclable . Printed with Vegetable Oil Based Inks on Recycled Paper (Minimum 25% Postconsumer) 

l 
2 

During the SIP development process the States may establish a NOx tons/season 

emissions decrease target for individual companies and then provide the companies with the 

opportunity to develop a plan that would achieve the needed emissions reductions. The 

companies may select from a variety of control measures to apply at their various emission units 

in the State or portion of the State affected under the NOx SIP call. These control measures 

would be adopted as part of the SIP and must yield enforceable and demonstrable reductions 

equal to the NOx tons/season reductions required by the State. What is important from EPA's 

perspective is that the State, through a SIP revision, demonstrate that all the control measures 

contained in the SEP are collectively adequate to provide for compliance with the State's NOx 

budget during the 2007 ozone season. 

Periodic Monitoring 

The NOx SIP call requires the State to provide for monitoring the status of compliance 

with any control measures adopted to meet the NOx budget.1 Title V air operating permit 

programs recognize SIP emissions limitations as applicable requirements that must be included 

in operating permits. Title V permit programs require SIP emissions limitations (and other 

applicable requirements) in permits to be accompanied by periodic monitoring sufficient to yield 

reliable data from the relevant time period that is representative of a source's compliance with 

the emissions limitation. In addition, the compliance assurance monitoring rule2 may apply to 

these emissions limitations at certain emissions units at Title V major sources. Acceptable 

monitoring is not limited to those monitoring methods such as continuous or predictive 

emissions measurement systems that rely on automated data collection from instruments. Nonautomated monitoring may provide a reasonable assurance of compliance for IC engines 

provided such periodic monitoring is sufficient to yield reliable data for the relevant time periods 

determined by the emission standard. 

Using parametric data may be appropriate, as the source owners and operators in 

permitting authorities' jurisdiction might already be collecting data that could be used to indicate 

compliance as part of normal, ongoing operations. When using parametric data to satisfy the 

periodic monitoring requirement, Title V permits should specify an operating range for each 

parameter or combination of conditions which will provide a reasonable assurance that the source 

is in compliance with the underlying requirement. The proposed range should be supported by 

documentation indicating a site-specific developed relationship between parameter indicator 

ranges and compliance with the emission limit, although it is not required that the range be set 

such that an excursion from the range will prove noncompliance with the associated limit. 

Operational data collected during performance testing is a key element in establishing indicator 

'See 40 CFR section 51.121(i). 

2

See40 CFR part 64. 
3 

ranges; however, other relevant information in establishing indicator ranges would be 

engineering assessments, historical data, and vendor data. The permit should also include some 

means of periodically verifying the continuing validity of the parameter ranges. 

New Source Review (NSR) 

Where sources choose to install combustion modification technology to reduce emissions 

of NOx at natural gas-fired lean-burn IC engines, EPA believes this action should be considered 

by permitting authorities for exclusion from major NSR as a pollution control project (PCP). 

Combustion modification technology for these IC engines is similar to the "low-NOx burner" 

technology already listed as a type of project that may be considered for exclusion from major 

NSR under EPA's PCP exclusion policy.3 Combustion modification technologies to reduce NOx 

emissions at natural gas-fired lean-burn IC engines include, for example, pre-combustion 

chambers, low emission combustion, high pressure fuel injection, and high energy ignition. It 

should be noted that, as the air to fuel ratio increases to very lean conditions, carbon monoxide 

and hydrocarbon emissions may increase slightly as excess air cools combustion temperatures 

and inhibits complete combustion. Pursuant to EPA's policy, if the source is located in a 

nonattainment area, the State or the source must provide offsetting emissions reductions for any 

significant increase in a nonattainment pollutant from the PCP. 

Unless information regarding a specific case indicates otherwise, installation of 

combustion modification technology for the purpose of reducing NOx emissions at natural gasfired lean-burn IC engines can be presumed, by its nature, to be environmentally beneficial. This 

presumption arises from EPA's experience that combustion modification technology is an 

effective pollution control technology when applied to new and modified natural gas-fired leanburn IC engines. Therefore, under EPA's PCP exclusion policy, the combustion modification 

controls may be exempted from NSR provided that the safeguards and procedural steps contained 

in the exclusion policy memorandum are met. 

Early Reductions bv IC Engines 

For large IC engines, development of the NOx SIP call budget involved (1) obtaining a 

1995 emissions inventory, (2) applying NOx reasonably available control technology (RACT) 

controls to major sources in certain areas, including the Ozone Transport Region, (3) projecting 

emissions to 2007, (4) modifying that subinventory to represent an uncontrolled level of 

emissions, and (5) calculating a percentage reduction from the uncontrolled 2007 baseline to 

determine the NOx tons reduction to include in the States' budget calculations. Because this 

methodology uses the uncontrolled value, any emission reduction from a large IC engine may be 

considered for credit toward meeting the NOx SIP call requirements. Creditable reductions may 

Memorandum from John Seitz to EPA Regional Office Air Directors, "Pollution Control 

Projects and New Source Review (NSR) Applicability," July 1,1994. 

i 
4 

include emission controls in place during or prior to 1995 as well as after 1995 for the large 

engines. The applicable control requirements must be adopted as part of the SIP and must yield 

enforceable and demonstrable reductions. 

For smaller IC engines, the first three steps above were completed as part of the NOx SB? 

call budget calculation, but the subinventory was not modified to represent an uncontrolled level 

of emissions, and no percentage reduction was applied to the 2007 baseline in detennining the 

States' budgets. Thus, the 2007 baseline for the smaller IC engines may include controls at IC 

engines, for example, that were subject to NOx RACT. Such controls would not be creditable 

toward meeting the NOx SIP call reductions because they are part of the 2007 baseline. Where 

the controls are not part of the 2007 baseline in the NOx SB? call inventory4, States may use 

emission reductions achieved after 1995 at the smaller engines as part of their NOx SB? call 

budget demonstration. The applicable control requirements must be adopted as part of the SIP 

and must yield enforceable and demonstrable reductions. 

Federal Implementation Plan (FTP) 

On October 21,1998, EPA proposed FB? requirements for States that failed to meet the 

NOx SIP call requirements published on October 27,1998. In subsequent litigation, the issue of 

the level of control for IC engines was remanded to EPA. On February 22,2002 EPA published 

a proposed rule regarding the NOx SB? call and level of control for IC engines. The views in the 

February 22 proposal and in the guidance in this memorandum reflect EPA's current views 

regarding IC engines and supersede the views underlying the proposed requirements in the FB? 

with respect to IC engines. For example, although the FB? proposed selective catalytic reduction 

(SCR) for lean-burn engines, in the February 22 notice we propose there is currently an 

insufficient basis to identify SCR as a highly cost-effective control technology for lean-bum 

engines in variable load operations and we propose that low emission combustion technology is a 

highly cost-effective control technology for the lean-burn engines. As a result, EPA would need 

to repropose the FB? requirements for IC engines prior to issuing a final FB? concerning the IC 

engines. A FB? reproposal would need to be consistent with the final rule on the NOx SB? call 

and control levels for IC engines. 

*The 2007 baseline NOx SB? Call emission inventory may be downloaded from the 

following site: i^://fh3.epa.gov/EmisInventory/NOxSB?Call_Mar2_2000/ 
5 

Please feel free to contact me or Doug Grano of my staff at (919) 541-3292 if you have 

any questions or wish to discuss any issues relating to this memorandum. 

cc: Rob Brenner, OAR 

Anna Wood, OPAR 

Sarah Dunham, OAP 

Kevin McLean, OGC 

Richard Biondi, OECA 

Tom Helms, OPSG 

i 
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