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Response to Significant Comments on the Proposed

Revisions to the General Conformity Regulations

(January 8, 2008; 73 FR 1402)

Docket Number OAR-2006-0669

U.S. Environmental Protection Agency

January 2010
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Table of Contents

Glossary of Terms............................................................................................................... 3

1.0 Introduction............................................................................................................. 4

2.0 Background............................................................................................................. 4

3.0 Responses to Comments on the Revised General Conformity Regulations........... 5

Part 51 – Requirements for Preparation, Adoption, and Submittal of Implementation 

Plans................................................................................................................................ 5

§51.851 State implementation plan (SIP) or tribal implementation plan (TIP) 

revision........................................................................................................................ 5

Part 93- Determining Conformity of Federal Action to State or Federal Implementation 

Plans................................................................................................................................ 6

§93.150 Prohibition..................................................................................................... 6

§93.151 State implementation plan (SIP) revision. ................................................... 8

§93.152 Definitions.................................................................................................... 9

§93.153 Applicability .............................................................................................. 15

§93.153 (b)................................................................................................................ 15

§93.153(c)(2) Treatment of aircraft emissions during takeoffs and landings........... 17

§93.153 (d)(1) Minor new source review (NSR) permit exemptions...................... 18

§93.153 (e) Emergency episodes.............................................................................. 19

§93.153 (f), (g), and (h) Presumed to conform......................................................... 20

§93.153 (i) and (j) Regionally significant emissions................................................ 23

§93.153 (i) Wildland fire .......................................................................................... 23

§93.153 (k) Grace period for newly designated nonattainment areas ..................... 25

§93.154 Federal agency conformity responsibility.................................................. 25

§93.155 Reporting requirements.............................................................................. 26

§93.156 Public participation .................................................................................... 26

§93.157 Reevaluation of conformity ....................................................................... 26

§93.158 Criteria for determining conformity of general federal actions................. 27

§93.158 (a)(5)(i)(C) .................................................................................................. 28

§93.159 Procedures for conformity determinations of general federal actions....... 29

§93.160 Mitigation of air quality impacts................................................................ 29

§93.161 Conformity evaluation for federal installations with facility-wide emission 

budgets...................................................................................................................... 29

§93.162 Emissions beyond the time period covered by the SIP.............................. 31

§93.163 Timing of offsets and mitigation measures................................................ 31

§93.164 Inter-precursor mitigation measures and offsets........................................ 33

§93.165 Early emission reduction credit programs at federal facilities and 

installations subject to federal oversight................................................................... 34

Since discrete emission reductions credits are produced in one time period and used 

at a later time, they generally would not meet the requirements for conformity. 

Therefore , EPA is not including their use in the General Conformity program...... 35

General Comments.................................................................................................... 35

Transportation Conformity ....................................................................................... 36
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Glossary of Terms

AGL – Above Ground Level

BSMP – Basic Smoke Management Practices

CAA – Clean Air Act

CFR – Code of Federal Regulations

EIS – Environmental Impact Statement

EPA – Environmental Protection Agency

ERC – Emission Reduction Credit

FAA – Federal Aviation Administration

FIP – Federal Implementation Plan

FR – Federal Register

NAAQS – National Ambient Air Quality Standard

NEPA – National Environmental Policy Act

NFR – Notice of Final Rulemaking

NSR – New Source Review

OAQPS – EPA Office of Air Quality Planning and Standards

OCS – Outer Continental Shelf

NOx – Nitrogen Oxides

PM – Particulate Matter

PM2.5 – Fine particles that are 2.5 micrometers in diameter and smaller

PM10 – Inhalable coarse particles that are larger than 2.5 micrometers and smaller than 10 

micrometers in diameter

RFP – Reasonable Further Progress

SAFETEA-LU – Safe, Accountable, Flexible, Efficient Transportation Equity Act: A 

Legacy for Users

SIP – State Implementation Plan

SMP – Smoke Management Program

TIP – Tribal Implementation Plan

VOC – Volatile Organic Compounds
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1.0 Introduction

This document, together with the notice of final rulemaking (NFR) “Revisions to 

the General Conformity Regulations,” presents the responses to significant comments 

received on the proposed revisions to the General Conformity regulations.

2.0 Background

Section 176(c) was revised by the Clean Air Act (CAA) in 1990 to require that 

federal actions conform to the appropriate state, tribal or federal implementation plan for 

attaining clean air (“General Conformity”). The Environmental Protection Agency

(EPA) issued the General Conformity regulations in 1993. The General Conformity

requirements are meant to prevent air quality impacts of federally approved or funded 

activities from causing or contributing to violations of the national ambient air quality

standards (NAAQS) in an area working to attain or maintain the standards. On January 8, 

2008, EPA proposed to revise its General Conformity regulations. EPA has only revised 

the General Conformity Regulations once since they were promulgated in 1993 to include 

de minimis emission levels for fine particulate matter and its precursors (July 17, 2006). 

Over this period, EPA and other federal agencies have gained experience with the 

implementation of the existing regulations and have identified several issues with that 

implementation. In addition, in 2004 EPA issued regulations to implement the revised 

ozone standard and in 2007 issued regulations to implement the new fine particulate 

matter standard. These regulations could affect the timing and process for General 

Conformity determinations. State and other air quality agencies are in the process of 

developing revised plans to attain the new standards; the proposed revisions to the 

General Conformity regulations will be helpful to the state, tribe, and local agencies as 

well as the federal agencies in developing and commenting on the proposed SIP 

revisions. The revised rule provides a streamlined process for federal agencies and states 

and tribes to ensure federal activities are incorporated in these state implementation plans 

(SIPs). Where that is not possible, it provides an efficient and effective process for 

federal agencies to ensure their actions do not cause or contribute to a violation of the 

NAAQS or interfere with the purpose of a state, tribal or federal implementation plan to 

attain or maintain the NAAQS. Specifically the revisions:

 Clarify and streamline the applicability, conformity determination and review 

processes, 

 Delete outdated or unnecessary requirements, provide transition tools for making 

conformity determinations for new NAAQS standards, 

 Incorporate process improvements requested by federal agencies, and 

 Further explain the General Conformity rules and policies. 
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3.0 Responses to Comments on the Revised General Conformity 

Regulations

The following sections address the comment letters received by EPA on the 

proposed revisions to the General Conformity regulations before the close of the public 

comment period on March 10, 2008. In all, EPA received over 300 comments from 65 

state, federal, or environmental organizations. The comment summaries and responses 

presented in this document follow the proposed revisions as they were presented in the 

Notice of Proposed Rulemaking. Each section has a brief overview of what EPA 

proposed, substantive comments received, and EPA’s responses. A list of commenters, 

including their docket numbers and organizations they represent, is found in Appendix A.

Part 51 – Requirements for Preparation, Adoption, and Submittal of Implementation 

Plans

§51.851 State implementation plan (SIP) or tribal implementation plan (TIP) 

revision

What EPA proposed: The EPA is revising 40 CFR 51.851 to make the adoption and 

submittal of the General Conformity SIP optional for the state and eligible federallyrecognized tribal governments. 

In addition, EPA is adding a new provision in §51.851(f), which allows states or 

tribes to include in their SIP or TIP a list of actions that are presumed to conform. For 

example, the state may identify the emissions from a certain type and size of construction 

activities that it presumes will conform. 

Comment: Several commenters supported EPA’s proposal to make the adoption and 

submittal of the General Conformity SIP optional. One commenter believed that the 

elimination of the conformity SIP requirement in §93.151 leaves a gap regarding the 

enforcement of mitigation measures. The commenter noted that under the language in 

the new provision, there is no state or federal enforceability if the state withdraws its 

conformity SIP or otherwise fails to retain a requirement that written commitments to 

undertake and implement mitigation measures are obligations of the SIP. 

Some commenters opposed allowing states to establish presumed-to-conform lists. 

One commenter thought this would allow project sponsors to avoid compliance. 

However, other commenters supported allowing states to develop their own lists. 

Response: In 1990, the CAA was amended to include a provision in Section 176(c)(4) 

that required states to adopt and submit to EPA for approval, a SIP to implement the

provisions of section 176(c). Section 6011 of the Safe, Accountable, Flexible, Efficient 

Transportation Equity Act: A Legacy for Users (SAFETEA-LU) revised the conformity 

requirements in section 176(c) of the CAA. Although most of the revisions affected the 

Transportation Conformity requirements, section 6011(f) also revised the General 
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Conformity requirements. Specifically, section 6011(f) revised section 176(c)(4)(A) of 

the CAA by including a requirement that the regulations must be periodically updated 

and by deleting the requirement for the states to adopt and submit a General Conformity

SIP. The EPA does not interpret this provision as prohibiting states or tribes from 

voluntarily adopting and submitting General Conformity implementation plans consistent 

with EPA regulations. However, EPA does believe that this revision prevents EPA from 

making submittal of a General Conformity SIP mandatory. Therefore, EPA is revising 

40 CFR 51.851 to make the adoption and submittal of the General Conformity SIP 

optional for state and eligible federally-recognized tribal governments.

The regulations require that if a state does not have conformity SIP, then federal agencies 

must conduct their conformity evaluation under the requirements of 40 CFR 93.150-165. 

These requirements are essentially the same as the requirements previously required to be 

contained in the conformity SIPs. Therefore, EPA believes there would be little 

difference in the enforceability of the regulations. The mitigation measures used for the 

conformity evaluations have always been required to be included in the attainment or 

maintenance SIP or TIP for the particular pollutant or as part of a permit program under 

the SIP or TIP, and not in the conformity SIP or TIP. Therefore, if the conformity SIPs 

are withdrawn the existing mitigation measures will not be affected, and EPA believes 

that the absence of a state adopted conformity SIP will not affect the enforcement of 

existing or future mitigation measures.

Comment: One commenter suggested that EPA needs to clarify the relationship between 

the TIP and SIP and federal agency responsibilities. The commenter supported the 

proposed listing of federally-recognized tribes for each nonattainment or maintenance 

area. The commenter noted that the list may need to provide contact information on 

Tribes that may not live in the nonattainment or maintenance area, but have “ancestral 

homeland” rights that may need to be addressed. The commenter suggested that EPA 

review 36 CFR 800.2(c)(2)(ii) to determine if the proposed regulation and preamble text 

adequately address the “ancestral homeland” issue.

Response: The EPA believes that the revised regulations provide a tribe with 

approximately the same rights afforded state and local agencies in evaluating the 

proposed conformity determinations, if the tribal land, which would include land 

designated as “ancestral homeland,” is located in the nonattainment or maintenance area 

affected by the action. If EPA has approved a tribal implementation plan for the area, the 

federal agency action must conform to that plan as well as any applicable SIP for the 

area. The consultation under the General Conformity Regulations does not relieve the 

federal agencies from other required consultation such as required under 36 CFR 

800.2(c)(2)(ii).

Part 93- Determining Conformity of Federal Action to State or Federal 

Implementation Plans

§93.150 Prohibition

§93.150 (c) Categories of actions that were not subject to the regulations at the time of 

promulgation in 1994
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What EPA proposed: Because paragraph (c) is outdated, EPA is deleting the paragraph 

and reserving it for later use. 

Comment: One commenter objected to the deletion of paragraph (c), noting that the 

deletion would create an uncertain status for projects that had been excluded under that 

provision.

Response: EPA established paragraph (c) of section 93.150 to identify the criteria for 

grandfathering actions that were started before the General Conformity Regulations were 

promulgated in 1993. If the federal agency with an action that has been grandfathered 

has not completed the action or has not commenced a continuous program to implement 

the action in the 16 years since the rules were promulgated, EPA believes that such an 

action would need to be re-evaluated, given the lapse of time. This is consistent with the 

requirements included in section 93.157. Further, EPA believes actions that have been 

completed or are being implemented would not be affected by the deletion of paragraph 

(c).

§93.150 (e) Actions affecting multiple nonattainment or maintenance areas.

What EPA proposed: The EPA is clarifying in 40 CFR 93.150 the General Conformity

evaluation for treatment of emissions from actions with emissions originating in more 

than one nonattainment or maintenance area. EPA believes that emissions in each area 

would be evaluated as if they resulted from separate actions.

Comment: Some commenters supported the concept of evaluating areas separately when 

an action results in emissions in more than one nonattainment or maintenance area. One 

federal representative commented that this approach is the most equitable approach to 

regulatory agencies as well as the project operators. Another commenter supported the 

proposal noting that it is similar to the Transportation Conformity Regulations. One 

commenter supported the proposal but requested flexibility for times when a large 

number of nonattainment or maintenance areas were involved. Another commenter 

supported the proposal but asked EPA to clarify the language regarding emissions 

originating in attainment areas that might impact nonattainment areas. 

Other commenters expressed concern about requiring separate evaluations for each area. 

One commenter said this is not a minor change. One commenter suggested the project 

should be evaluated as a whole to determine if the emissions exceed de minimis level; if 

emissions fall below de minimis levels, no conformity evaluation would be required. 

Another commenter objected to “splitting” the emissions, suggesting that this could allow 

a significant and unchecked increase in emissions downwind.

Response: Under the statutory requirements of CAA section 176, emissions from federal 

actions that affect multiple nonattainment or maintenance areas need to be evaluated to 

ensure that the action conforms with the applicable implementation plans. Since several 

of the conformity requirements are specific to the individual nonattainment or 
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maintenance areas (e.g., de minimis emission levels and emissions included in the SIP), 

federal agencies cannot evaluate the conformity of their actions except on an individual 

area basis. The EPA has allowed some flexibility in the reporting requirements where the 

action would affect a large number of areas. However, EPA believes the evaluation 

must include analysis of the individual areas to ensure that the action conforms to the 

individual SIPs. Under the CAA, only emissions in nonattainment or maintenance areas 

are subject to the conformity requirements. Emissions originating from actions in 

attainment areas are not subject to General Conformity requirements regardless of their 

affect in a nonattainment or maintenance area. In addition, EPA has clarified that under 

the relevant regulations, only emissions that fit within the definition of direct or indirect 

emissions (i.e., must be reasonably foreseeable, practically controlled, and under 

continuing program responsibility) and are above the de minimis thresholds need to be 

considered. 

§93.151 State implementation plan (SIP) revision.

What EPA proposed: In 1990, the CAA was amended to include a provision in Section 

176(c)(4) that required states to adopt and submit to EPA for approval, a SIP to 

implement the provisions of section 176(c). Section 6011 of Safe, Accountable, Flexible, 

Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) revised the 

conformity requirements in section 176(c) of the CAA. Although most of the revisions 

affected the Transportation Conformity requirements, section 6011(f) also revised the 

General Conformity requirements. Specifically, section 6011(f) revised section 

176(c)(4)(A) of the CAA by including a requirement that the regulations must be 

periodically updated and by deleting the requirement for the states to adopt and submit a 

General Conformity SIP. The EPA does not interpret this provision as prohibiting states 

or tribes from voluntarily adopting and submitting General Conformity implementation 

plans consistent with EPA regulations. However, EPA does believe that this revision 

prevents EPA from making submittal of a General Conformity SIP mandatory. 

Therefore, EPA is revising 40 CFR 51.851 to make the adoption and submittal of the 

General Conformity SIP optional for state and eligible federally-recognized tribal 

governments.

Comment: Several commenters supported EPA’s proposal to make the adoption and 

submittal of the General Conformity SIP optional. Others disagreed, noting that the 

elimination of the conformity SIP requirement in §93.151 would be an impermissible 

relaxation and would leave a gap regarding the enforcement of mitigation measures. The 

commenter noted that under the language in the new provision, there is no state or federal 

enforceability if the state withdraws its conformity SIP or otherwise fails to retain a 

requirement that written commitments to undertake and implement mitigation measures 

are obligations of the SIP.

Response: The EPA is revising its regulations to be consistent with the revised 

requirements of the CAA. In 2005, the CAA was revised to eliminate the requirement 

that a state must adopt a conformity SIP. The EPA’s original General Conformity

Regulations required federal agencies to comply with the state conformity SIP where 
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applicable. Where there is no state conformity SIP, the regulations required the federal 

agencies to demonstrate conformity under the provisions in 40 CFR Part 93. We have 

not changed that those requirements. EPA regulations require the conformity SIPs and 

TIPs to include essentially the same measure as the requirements in Part 93, therefore if a 

SIP is withdrawn there would be little difference in the requirements for the federal 

agencies or the enforceability of the regulations and thus would not be a relaxation of the 

requirements.. 

As stated in response to comments on section 40 CFR 51.851, the mitigation measures 

used for the conformity evaluations are required to be included in the attainment or 

maintenance SIP or TIP for the particular pollutant or as part of a permit program under 

the SIP or TIP and not in the conformity SIP or TIP. Therefore, if the conformity SIPs 

are withdrawn the existing mitigation measures will not be affected and EPA believes 

that the absence of a state adopted conformity SIP will not affect the enforcement of 

existing or future mitigation measures.

§93.152 Definitions

EPA proposed revising 12 of the existing definitions, adding 11 new terms, 

deleting one term, and clarifying the scope of an existing definition. The definitions that 

received comment are found below.

Applicability analysis

What EPA proposed: The EPA is adding this new term to describe the process of 

determining if the federal agency must conduct a conformity determination for its action.

Comment: A commenter suggested that EPA’s proposed definition lacks specificity and 

appropriate detail. The commenter notes that the preamble more thoroughly defines 

applicability analysis than does the rule. The commenter suggests that at a minimum, the 

rule contain the same wording as that found in the preamble. However, the commenter 

notes that neither the preamble nor the rule indicates the sort of documentation and 

analysis required for a federal agency to establish that the federal actions “total direct and 

indirect emissions are below or above the de minimis levels.”

Response: In the original promulgation, EPA established the term “applicability

analysis” to describe the activities that Federal agencies or other affected parties 

undertake in determining if a conformity determination is required. The EPA is using the 

term to clarify the steps in the process. The specific requirements included in the 

regulations and the discussion provided in the preamble are adequate to describe the 

process. 

Under the original and revised regulations, federal agencies must determine whether the 

direct and indirect emissions from federal actions are below the de minimis levels. As a 

general matter, it has always been, and continues to be, in the reasoned discretion of the 
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federal agency to decide which methods and analysis it will use when determining 

whether this or any other provision applies to the emissions from its activity. 

Caused by

What EPA proposed: The basic test established by the 1993 regulations’ definition of 

“caused by” is that the emissions would not have occurred in the absence of the federal 

action. Since promulgation of the General Conformity regulations in 1993, EPA has 

interpreted the regulations to require a federal agency to include construction emissions 

in its conformity analysis. The EPA believes that emissions from construction activities 

initiated, approved, or funded by a federal agency meets this test and should be included 

in the conformity evaluation. Therefore, EPA is clarifying that construction emissions 

are part of the total direct and indirect emissions from an action.

Comment: In the January 8, 2008 proposal, EPA solicited comment on whether 

construction emissions in general or short-term construction emissions should be exempt 

from the regulations. In addition, EPA solicited comment on what should be considered 

short-term construction emissions (1 to 5 years). The majority of commenters on this 

issue objected to exempting construction emissions. They noted:

1. That construction emissions can contribute significantly to particulate 

matter (PM) exceedances, especially off-road vehicle emissions. 

2. That exempting construction emissions from General Conformity

would be in direct conflict with the Clean Air Act. 

3. That the effects of construction emissions are not necessarily

temporary. 

4. That ignoring these emissions might drop a project below the de 

minimis threshold and result in unmitigated emissions and the exposure 

of local residents to significant levels of pollutants such as diesel 

exhaust. 

Commenters supporting the exemption of construction emissions noted: 

1. That construction emissions only peak for a short time and that a 

disproportionate amount of time in the conformity process is spent on 

addressing very short-term construction-related emissions. 

2. That construction emissions are only a small percentage of a nonattainment or 

maintenance area’s off-road emission budget and generally not included in 

New Source Review (NSR) or Transportation Conformity evaluations. 

3. That civil works projects are not inherently different from transportation 

projects and are designed to minimize effects during environmentally

sensitive seasons and thus there is no air quality reason for treating them 

differently. 

Of the commenters that thought construction emissions should be exempt, some 

thought they should be exempt for 5 years while others thought they should be 

exempt for only 2 years. One commenter agreed that construction emissions should 

be exempt noting that the General Conformity and Transportation Conformity

programs should be consistent on the handling of construction emissions. The 
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commenter thought that if EPA decides to include construction emissions in the 

conformity evaluation, EPA should exempt short-term emissions of less than 2 years. 

This commenter requested EPA clarify how construction emissions are to be handled 

under various programs such as the facility-wide emission budget and the minor NSR 

permit. One commenter suggested that the final notice lists and explain the available 

options for handling construction emissions including: incorporating them in advance 

into the SIPs.

Response: The EPA agrees with the majority of commenters on this issue that 

construction emissions can contribute to exceedances of the NAAQS, particularly

exceedances of the PM standards. Unlike the construction activities associated with 

Transportation Conformity and NSR projects, construction activities associated with 

General Conformity actions vary widely in type. For example, General Conformity is 

concerned about localized impacts of the direct and indirect impacts of particular actions

or projects, as reflected in case-by-case analysis of emissions from specific actions, while 

Transportation Conformity is primarily concerned with the regional impacts of long-term 

use of the roads, as reflected in analysis of regional transportation processes, only

secondarily concerned with short-term and localized impacts. Because of the wide 

variety of actions covered by the General Conformity regulations, it is not easy to 

characterize the relationship between the construction and post construction emissions. 

Also, NSR specifically does not apply to emissions from mobile sources, which includes 

most construction equipment -- no such restriction is found in General Conformity. 

Moreover, as explained in the preamble to the final rule, EPA believes that emissions 

from construction activities initiated, approved, or funded by a federal agency would not 

have occurred in the absence of the federal action and thus meet the “caused by” 

definition included in the General Conformity regulations. For these reasons, EPA 

believes that it is important that construction emissions be considered as part of the 

General Conformity process. EPA also believes that other flexibilities in the revised rule 

will help with planning for and addressing construction emissions in the General 

Conformity process. These flexibilities include allowing alternative mitigation schedules 

and including construction emissions in a facility emission budget. 

Also, EPA is clarifying that conformity is based on annual emissions. Therefore, federal 

agencies should estimate construction emissions on an annual basis and would only have 

to demonstrate conformity of construction emissions during the years when those 

emissions occur.

Direct emissions

What EPA proposed: EPA proposed to include a requirement that the emissions must be 

reasonably foreseeable. This was unintentionally left out of the definition when the rules 

were promulgated in 1993.

Comment: One commenter supported the proposal to include the phrase “reasonably 

foreseeable” in the definition of direct emissions. Several other commenters did not 

support adding this phrase to the definition. One commenter noted that the revised 
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definition does not allow for potential changes in the direct emissions that may occur 

during the course of the project.

Response: In promulgating the regulations in 1993, EPA discussed two different 

approaches to the regulations. First was the inclusive approach that would have required 

federal agencies to include all potential emissions that could have in any way resulted 

from the action, regardless of whether the federal agency had any control over those 

emissions. The other approach was the exclusive approach that required the federal 

agencies to address those emissions that resulted from the action and over which it had 

control through a continuing program responsibility. EPA selected the exclusive 

approach. EPA described two types of emissions -- direct and indirect. Direct emissions 

occur at the time and place of the action, while indirect emissions occur at a later time or 

removed in distance from the action. EPA stated that the indirect emissions had to be 

reasonably foreseeable. Consistent with the exclusive approach, it follows that EPA 

intended that both direct and indirect emissions should be reasonably foreseeable and 

proposed to add that phrase to the definition of direct emissions. Since the federal agency

knows the time and place of the action, all or nearly all emissions that result from the 

action at the time and place of the action would be reasonably foreseeable to the agency. 

Therefore, EPA believes the addition of the language is consistent with the 

implementation of the existing regulations and should have little-to-no impact on the 

emissions subject to the conformity requirements. 

Indirect emissions

What EPA proposed: The EPA is revising the definition for indirect emissions to clarify

that only indirect emissions originating in a nonattainment or maintenance area need to 

be analyzed for conformity with the applicable SIP. In addition, EPA is revising the 

definition of “indirect emissions” to clarify what is meant by “the agency can practically 

control” and “for which the agency has continuing program responsibility.” This 

clarification represents EPA's long standing position that Congress did not intend for 

conformity to apply to “cases where, although licensing or approving action is a required 

initial step for a subsequent activity that causes emissions, the agency has no control over 

that subsequent activity, either because there is no continuing program responsibility or 

ability to practically control.” 58 FR 63,214 at 63,221 (November 30, 1993); see also

General Conformity Guidance: Questions and Answers, USEPA, Office of Air Quality

Planning and Standards (OAQPS), Page 6, Question 2 (July 13, 1994).

Comment: One commenter believes that excluding emissions over which the federal 

agency does not have continuing program responsibility is unlawful. The commenter 

believes that the original definition of “caused by” is practical because the conformity

determination will be made in the context of an Environmental Impact Statement (EIS) 

for such major federal projects and National Environmental Policy Act (NEPA) requires 

an assessment of the expected development and reasonably foreseeable impacts 

associated with such development. The commenter noted that if the agency with 

authority to approve these expansions lacks the continuing programmatic responsibility to 

control the use of facilities approved by the agency, then the proposed activity should not 
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be approved. The commenter also believes that the proposed rule definition has the 

potential for allowing massive increases in emissions that are anticipated as a result of 

port expansions in some of the nations’ most polluted metropolitan areas. The commenter 

also noted that NEPA may also create authority to adopt environmental mitigation plans 

as part of an agency’s programmatic responsibility.

Response: EPA is not changing the requirements of this provision in the final rule – EPA 

is only clarifying the language contained in it. Since 1993, the “indirect emissions” 

definition has been limited to those emissions for which “the federal agency...will 

maintain control over due to continuing programmatic responsibility.” Accordingly, 

EPA’s reformatting of the language in this final rule does not change the practical impact 

of this definition. The commenter’s suggestion that the definition should include 

emissions over which the federal agency does not have control would greatly expand the 

program beyond what EPA believes that the law intended. Moreover, because EPA did 

not propose to expand the program to include emissions over which a federal agency does 

not have control, it cannot finalize such an expansion in this rule. Finally, EPA notes that 

the exclusion of emissions over which the federal agency does not have a continuing 

program responsibility is applicable to indirect emissions for the General Conformity

analysis and does not affect the analysis required for NEPA review. While federal 

agencies often conduct their General Conformity analysis during their NEPA review 

and/or preparation of an EIS, the General Conformity requirements are distinct from and 

different than those requirements. 

Comment: One commenter was concerned that the proposed definition would not allow 

indirect emissions outside of the nonattainment or maintenance area to be included in the 

emission estimates.

Response: The 1995 amendment to the Clean Air Act section 176(c) specifically limits 

conformity requirements to emissions in the nonattainment or maintenance area. 

Therefore, indirect emissions only from the nonattainment or maintenance area are 

subject to conformity requirements.

Comment: One commenter supported the proposal to revise the definition for indirect 

emissions to clarify that any indirect emissions originating in an attainment or 

unclassifiable area do not need to be analyzed for conformity purposes. The commenter 

supported the proposed provision that the indirect emissions must be of the type that the 

“agency can practically control” and for which the agency has “continuing program 

responsibility. The commenter asked that the revised rule clarify whether vessels are 

subject to conformity. 

Response: The EPA contends that emissions from vessels are the same as other mobile 

sources and federal actions that affect vessels should consider their emissions. Since 

vessels are mobile sources and the rule includes mobile sources as part of the direct and 

indirect emissions, EPA does not believe that it is necessary to specifically identify

vessels as covered by the rule.
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Maintenance area

What EPA proposed: EPA is making a minor wording change to clarify the definition by

citing the regulations and the section of the CAA used to identify maintenance areas.

Comment : A commenter recommended that the definition of “maintenance area” be 

consistent with the definition used in the transportation conformity regulation.

Response: The definition of maintenance area is consistent with the definition of 

maintenance area in the Transportation Conformity Regulations, and both refer to section 

175A of the CAA, which is used to identify maintenance areas. 

Restricted information 

What EPA proposed: As discussed in §§93.155 and 156 on reporting and public 

participation, EPA is specifying how restricted information used in the conformity

determination is to be handled. To support those revisions, EPA is adding a definition of 

restricted information. The definition is based upon applicable Executive Orders, 

regulations and statutes pertaining to materials and other information where disclosure is 

restricted by law.

Comment: One commenter requested that EPA state that emission data be specifically 

excluded from the definition of “restricted information.” 

Response: The EPA agrees that emission data generally can not be considered “restricted 

information.” Section 114(c) of the Clean Air Act states that emission data cannot be 

considered as “confidential business information.” Only in rare circumstances where 

data is contained in documents classified as sensitive information to which access is 

restricted by law or regulation to particular classes of persons and a formal security 

clearance is required to handle or access the classified data would emission data from a 

government facility be “restricted information.” In the situations where restricted 

information is used as part of the conformity evaluation, EPA will work with the 

appropriate federal, state and tribal agencies to ensure an adequate review of the 

conformity evaluation.

Mitigation measure

The EPA is defining a mitigation measure as a method of reducing emissions of the 

pollutant at the location of the action. This definition would distinguish a mitigation 

measure from an offset.

Comment: One commenter suggested adding the phrase “that utilizes verified 

technology approved by EPA or other technology approved by the state agency.”

Response: The EPA’s definition of mitigation measure is broad enough to encompass 

many different approaches to reducing emissions including innovative approaches that 
15

may not have been previously verified by pollution control agencies. EPA believes the 

addition of the suggested language may inhibit the development of new and innovative 

approaches. EPA also notes that credit for the emission reductions from the mitigation 

measures can be obtained only after the measure has been verified.

§93.153 Applicability

Comment: One commenter recommended that EPA revise the rule to explicitly state that 

only Outer Continental Shelf (OCS) emissions that originate in a nonattainment or 

maintenance area are subject to conformity.

Response: Generally, EPA considers the applicable nonattainment or maintenance area 

to extend 3 miles from the state’s seaward boundary, except in Texas and Florida where 

the seaward boundary is 3 leagues from the shore. However, the EPA’s OCS Air 

Regulations in (40 CFR 55) require that sources within 25 miles of the state’s seaward 

boundary must meet the same requirements as if the source was located on shore. The 

OCS Air Regulations apply to all applicable waters off the US coastline, except for the 

coast of the Gulf of Mexico west of Florida, where the US Department of the Interior, 

Mineral Management Service regulations apply instead. Therefore, federal actions 

covered by the OCS regulations and located within 25 miles of a state’s seaward 

boundary off a nonattainment or maintenance area would be subject to conformity

evaluation with regard to the implementation plan for the applicable on-shore area. For 

those actions in areas beyond 25 miles from the seaward boundary, the federal 

designation would apply because EPA has never designated those areas as nonattainment 

and are unclassified. Thus, General Conformity does not apply to actions in those areas 

because they do not meet the General Conformity applicability requirement that the 

action must in a maintenance or non-attainment area.

§93.153 (b) 

Comment: One commenter asked EPA to address the anti-backsliding issue since 

reclassifications of some areas for the new ozone standard would allow actions in the area 

to have less stringent de minimis emission levels.

Response: Under section 110(l) of the Clean Air Act, EPA cannot approve a revision to a 

SIP if the revision would interfere with attainment or maintenance of a NAAQS or any

applicable requirements of the Act. This section has been called the anti-backsliding 

provision because it prevents states from revising or dropping control requirements 

without offsetting the lost emission reductions. The promulgation of the new ozone 

standards resulted in a lower classification for some areas and thus the areas would be 

subject to less stringent requirements. Under the anti-backsliding provisions states would 

not be able to withdraw the prior regulations unless they could demonstrate that those 

regulations are not needed to attain and maintain the standard. The General Conformity

provisions of the CAA do not contain a similar restriction on backsliding, and EPA did 

not retain General Conformity as an anti-backsliding requirement in our transition 

regulations for the 8-hour ozone standard, a decision that was upheld by the D.C. Circuit. 
16

See South Coast Air Quality Management Dist. v. EPA, 489 F.3d 1245, 1248 (D.C. Cir. 

2007) (limiting the anti-backsliding findings to transportation conformity budgets) 

Accordingly, General Conformity determinations made after the area has been 

reclassified would be based upon the new area requirements and must demonstrate that 

the emissions will not interfere with the attainment or maintenance of that standard. We 

believe that the de minimis emission levels based upon the area’s new classification are 

adequate for that demonstration.

Comment: Several commenters suggested that the PM2.5 de minimis level should be 

reconsidered to be sure that the PM2.5 level is at least as stringent as PM10. One 

commenter noted that PM2.5 emissions, as a subset of PM10 emissions, are always less 

than PM10 emissions and argued that it is ineffective to have a threshold for PM2.5 that is 

higher than PM10. Another commenter suggested that the threshold for volatile organic 

compounds (VOCs), nitrogen oxides (NOx), direct PM and sulfur dioxide levels in table 

93.153(b) for the 8 hour ozone standard and the 24 hour PM2.5 standards should be 

reduced. 

Response: When EPA promulgated the PM2.5 de minimis emissions on July 17, 2006,

(71 FR 40422) it noted in response to a similar comment that “[t]he intent of the de 

minimis levels is to assure that the General Conformity rule covers only major federal 

actions that are major sources of emission. The Act in section 302(j) defines a major 

source as meaning ‘any stationary facility or source of air pollutants which directly emits, 

or has the potential to emit, one hundred tons per year or more of any air pollutant 

(including any major emitting facility or source of fugitive emissions of any such 

pollutant, as determined by rule by the Administrator).’ This definition provides a 

Congressional threshold for a major source. As discussed in the preamble of the proposal, 

EPA is using the same methodology to set the de minimis level for PM2.5 as it did for the 

other NAAQS pollutants (with the exception of lead, which had alternative de minimis 

levels in light of the unique nature of lead emissions). This methodology is based on a 

level found in the statute as defining major stationary sources of air pollution.” This 

methodology was explained in the November 30, 1993 preamble to the promulgation of 

the General Conformity Regulations (58 FR 63228). Even though the concentration 

levels for the standards have reduced, the definition of major sources have not. With 

regard to the suggestion that the general conformity de minimis thresholds for various 

pollutants should be reduced, such a change cannot be made since it was not included in 

the proposed rule. However, EPA retains the authority and discretion to re-evaluate those 

standards in a future rulemaking as appropriate. 

Comment: One commenter asked EPA to clarify that the nonattainment status of an area 

be determined based on the 8-hour ozone standard, not the 1-hour standard.

Response: The General Conformity regulations are designed to ensure that federal actions 

do not interfere with the states and tribes ability to attain and maintain the national 

ambient air quality standards. The conformity requirements apply to all applicable air 

quality standards and federal actions must conform to the SIPs, TIPs or federal 

implementation plans (FIPs) for the areas. Although EPA has replaced the 1-hour ozone 
17

standard with the 8-hour standard, many of the 1-hour existing SIPs retain the 1-hour 

standard and those requirements remain in place as a basis for addressing the 8-hour 

standard. Accordingly, in carrying out the conformity determination for a specific action, 

the federal agency should apply the standard in place in the area(s) in which the action 

will occur. 

Comment: Several commenters opposed omitting the analysis of ultra fine particles 

(PM1.0 and below)

Response: The General Conformity regulations are designed to ensure that federal actions 

do not interfere with the states and tribes ability to attain and maintain the national 

ambient air quality standards. The conformity requirements apply to all applicable air 

quality standards, and federal actions must conform to the SIPs, TIPs or FIPs for those 

standards that are applicable for the areas in which the action will occur. Because the 

EPA has not promulgated an ultra fine particulate standard, the specific analysis of ultra 

fine particles is not required under the conformity program. EPA also notes that ultra 

fine particulates are included as part of the fine particulate (PM2.5 ) emissions that are 

required to be evaluated under the current and revised rules. 

§93.153(c)(2) Treatment of aircraft emissions during takeoffs and landings 

What EPA proposed: EPA proposed revisions to the regulations that would exempt 

aircraft emissions above 3000 feet above ground level (AGL) from the General 

Conformity requirements. 

Comment: Several commenters representing state and local air quality agencies objected 

to excluding the emissions from aircraft above 3000 feet above ground level. They noted 

that the mixing height varies and can be as high as 4,500 feet AGL during the ozone 

season and that pollutants emitted at middle and high altitudes can travel long distances. 

They also noted that pollution levels were below predicted levels following September 

12, 2001 when aircraft were grounded. One commenter added that many states know 

from experience that even above 3000 feet such emissions can have adverse impacts. 

Another commenter questioned the adequacy of the Federal Aviation Administration 

(FAA) study upon which EPA relied in developing this exemption.

Other commenters representing the airports and the airline industry supported the 

exemption emission from aircraft above 3000 feet AGL. They noted that the FAA study

supports the conclusion that aircraft operations at or above 3,000 feet AGL have a 

minimal effect on ground level pollutant concentrations. The commenters also noted that 

flights over almost all major U.S. airports must be at least 7000 feet AGL, therefore, any 

commercial aircraft operating at 3000 feet would most likely either be landing or taking 

off. The commenters also noted that the FAA study concluded that any increase in 

ground level concentrations of CO and hydrocarbon (HC) due to mixing was negligible. 

A federal agency commenter believes that the exemption for air traffic control activities 

should not be restricted by altitude. The commenter noted that the proposal for 
18

exempting aircraft operations above 3,000 feet AGL is much narrower than what was 

presented in the preamble to the 1993 General Conformity rule as an example of an 

action that may be exempt from the General Conformity requirements – “air traffic 

control activities and adopting approach, departure and enroute procedures for air 

operations.” 

Response: EPA agrees that the aircraft emissions above the mixing height do not 

significantly affect ground level concentrations and acknowledges that the mixing height 

can vary from one area to another. Accordingly, in those areas where the applicable SIP 

or TIP specifies a mixing height to be used, EPA is requiring the specified mixing height 

to be used in conformity determinations. However, in those areas where the SIP or TIP 

does not specify a mixing height, EPA is allowing the federal agencies to use 3,000 feet 

AGL as a default mixing height. This conclusion is supported by the FAA study. EPA 

also notes that 3,000 feet AGL is commonly used as an estimate of the average maximum 

afternoon mixing height across the country and most air quality models use 3,000 feet 

AGL as the default mixing height. However, we also note that the FAA study showed 

that some areas have mixing heights lower than 3,000 feet AGL, so in the final rule we 

have added regulatory language to sub-paragraph (xxii) to allow federal agencies to use a 

different mixing height if they can demonstrate that emissions at and above that height 

are de minimis in the particular area. We have also explained in the preamble that it is in 

the reasoned discretion of the Federal agency to decide which methods and analysis it 

will use when determining whether this exemption or any other provision applies to the 

emissions from its activity. 

With regard to the alleged inadequacies of the FAA study, EPA believes that the study

supports the conclusion that aircraft emissions above the mixing height do not 

significantly affect ground level concentrations. The study was based on very

conservative assumptions regarding the data applied and the analysis performed, such 

that any particular concerns with the data and analysis provided in the study do not rise to 

the level of negating the usefulness of the study in our present rulemaking.

§93.153 (d)(1) Minor new source review (NSR) permit exemptions 

What EPA proposed: EPA proposed to exempt the emissions from stationary sources 

permitted under the minor source NSR programs as EPA’s existing General Conformity

regulation already provides for exemptions for emissions from major NSR sources.

Comment: The majority of commenters agreed with the proposal to exempt stationary

sources permitted under the NSR program. They believed the review to be redundant and 

unnecessary. 

Some commenters disagreed with exempting minor sources. One commenter said this 

was not a minor change to the regulations. Another thought that EPA should not exempt 

activities with emissions less than the major source threshold from conformity review 

unless some basis can be established that the cumulative emissions from such sources are 

truly de minimis with respect to the statutory conformity tests. The commenter suggested 
19

that EPA substitute a SIP-based program for establishing a budget for minor sources in 

place of the regionally significant threshold. Several commenters suggested that only

NSR permits which require offsets or are offset on a programmatic basis should be 

exempt from conformity. A few commenters thought that if EPA exempts minor sources 

for the conformity evaluation, it must first clearly demonstrate that such exemptions will 

not impede states’ ability to attain any standard. 

Response: The EPA agrees that requiring a conformity analysis for emissions covered by 

a minor source NSR permit would be redundant and provide little environmental benefit. 

EPA believes that the permitting authority has the responsibility to ensure that the source 

will not interfere with the SIP or otherwise interfere with the state’s ability to attain the 

standards. Minor source NSR permits are issued under a SIP-approved program, so there 

has already been a determination that the permitting program will not contribute to a 

violation of the NAAQS or delay the attainment or maintenance of the standards. 

Moreover, as such determinations are made with regard to all minor source permits 

issued under the program, regardless of whether or not they required offset, we do not 

think that the General Conformity exemption should apply only to permit with offsets. 

Thus, by issuing a specific permit under that program, the authority is finding that the 

emissions are accounted for in the SIP, effectively providing the same assurances as a 

conformity determination since federal agencies can demonstrate conformity for an 

action by showing that the actions will not cause a violation or interfere with the SIP. 

Therefore, in the final rule, EPA will exempt the emissions from stationary sources 

permitted under both the minor and major source NSR programs. 

§93.153 (e) Emergency episodes

What EPA proposed: EPA proposed to amend paragraph (e)(2) to provide procedures for 

reviewing the extension of time for making a conformity determination for emissions 

from federal actions related to responding to an emergency.

Comment: Most commenters supported the clarification of the procedures for extending 

the time for conducting a conformity determination for emissions generated in actions 

responding to emergency events. One commenter thought that the rule should be revised 

to require that EPA must approve extension requests beyond 2 years and also that the 

extension should be circulated for public comment and that extensions should be subject 

to judicial review. Another commenter thought that the 15 day period found in the 

proposal for review by the state and EPA is not enough time for large and complex 

federal projects. In addition, this commenter was concerned that the exemption timeline 

would go past the attainment years for the 8-hour ozone and PM2.5 NAAQS. 

Response: The purpose of this exemption is to allow federal agencies to respond 

quickly to emergencies without the need to propose and take comment on their actions. 

As a general matter, emergency events include a natural disaster, terrorist attack, military

mobilization, or other situations (such as wildfire responses) that an agency determines fit 

within the definition of emergency found in §93.152. Given the nature of such events,
20

EPA recognizes that, in some cases, those responses will result in additional emissions in 

nonattainment or maintenance areas, however the actions are necessary to address the 

aftermath of the emergency. In most cases, the federal agency can complete its action in 

a relatively short period of time, less than 6 months, but we note that in some cases, 

additional time is needed to respond to the emergency. For example, following the 

September 11, 2001 attack in New York, the subway service under the Hudson River was 

interrupted. Federal agencies took actions to provide ferry service between New Jersey

and Manhattan Island. The federal agencies were limited to the available ferries in the 

area and did not have the ability to control the emissions from those ferries. The ferry

service was required until the subway system could be reconstructed. The 1993 

regulations recognized the need for this exemption, and although those regulations 

allowed for this exemption, they did not provide procedures for extending the exemptions 

beyond the first 6 months. EPA believes that the revised regulations provide a balance 

between the need of federal agencies to continue actions to respond to the emergencies 

and the need to demonstrate conformity to the SIP or TIP. Since the actions are in 

response to an emergency, the state and tribal agencies should be aware of the actions and 

should be able to quickly review the proposed extension. Requiring agencies to take 

public comment on the proposed extension would add additional burden on the agencies 

in their attempt to respond to the emergency and would not be feasible in the timeframes 

available. EPA agrees that if the emergency occurs near the deadline for attaining an air 

quality standard, then there is a possibility that the exemption could extend beyond the 

attainment deadline. In those rare cases where this would occur, EPA will work with the 

states, tribes and other federal agencies to address the situation. 

§93.153 (f), (g), and (h) Presumed to conform

What EPA proposed: EPA proposed to clarify how federal agencies should develop their 

lists of actions that are “presumed to conform.”

Comment: Some commenters agreed with the proposed clarification while others 

opposed the development of agency presumed to conform lists. One commenter thought 

that if these lists were produced in cooperation with the states, they could decrease 

administrative burden associated with minor actions that have been shown to result in 

insignificant increases in emissions. One commenter suggested that a central location be 

established where state agencies and the public could go to view actions that have been 

approved that are presumed to conform. Another commenter supported the limitation on 

using a combination of measures that are on an agency’s presumed-to-conform list if the 

combined emissions would equal or exceed the de minimis levels. One commenter 

thought that public participation should be allowed and that there should be an 

opportunity for judicial review. The commenter asked EPA to explain in the preamble 

how any such list may be challenged.

One commenter did not agree with allowing federal agencies to develop presumed to

conform lists. The commenter thought that the federal agencies would use the presumed

to conform lists to avoid conformity evaluations. Further, the commenter believed that 
21

all contemporaneous actions taken by a federal agency should be combined for the 

conformity evaluation. One commenter thought the proposed revision to the presumed to

conform section violated the Clean Air Act and was an unlawful delegation of authority.

One commenter requested that EPA define what is meant by “clearly demonstrate” that 

the emissions from the action are included in the SIP. 

Response: In the original General Conformity Regulations promulgated in 1993, EPA 

listed a number of actions that were exempt from General Conformity review based on 

their de minimis emissions as well as actions that were presumed to conform. 40 CFR §§ 

93.153(c)(2)-(e); see also 58 FR at 63229-232. Those exemptions and presumptions 

apply to all agencies that undertake those actions and apply in all states where those 

actions might occur. At the same time, EPA recognized that individual agencies might 

want to avoid repetitive conformity analyses for actions that result in de minimis 

emissions. .Therefore, EPA allowed federal agencies to adopt their own “presumed to 

conform” list by documenting that “certain types of future actions would be de minimis.” 

58 FR at 63232. Specifically, § 93.153(g) requires federal agencies to demonstrate that 

the total emissions from the activities meet the requirements contained in CAA section 

176(c)(1) and are below the de minimis emissions levels established in the rule. EPA 

explained that experience from similar previous actions could form the basis for that 

demonstration. 58 FR at 63232. 

The regulations provide a number of additional safeguards to insure that these 

demonstrations are met. Section 93.153(h) requires that the federal agency follow certain 

procedures to provide notice of, take comment on, respond to comment on, and finalize

the list. Accordingly, these procedures allow the public, EPA, and relevant air quality

authorities to review the agency’s proposed list and accompanying de minimis 

documentation. In addition, the publication of the final presumed to conform list in the 

Federal Register is a final agency action subject to judicial review under the 

Administrative Procedures Act. And once such a list is promulgated, the public also has 

the opportunity to rebut the agency’s application of the presumption to a specific action. 

See 58 FR at 63230 (noting that some actions are exempt and others are “presumed to 

conform, with the presumption being rebuttable”). Finally, a presumed to conform list 

cannot be used to violate the statutory requirements of General Conformity because the 

regulations specifically bar an agency from relying on the presumed to conform list if its 

application to a specific activity would not comply with the criteria of CAA § 176(c)(1). 

40 CFR §93.153 (f), (g)(1), and (j). 

In revising the presumed to conform regulation, we have not changed the basic process

and safeguards provided in the original regulations, but we have provided some 

clarification on how an agency can demonstrate that a class of action could be presumed 

to conform. In the revised regulations, we have also allowed states to adopt their own 

presumed to conform lists that all federal agencies within their jurisdiction could use. 

Allowing federal agencies or states to adopt their own presumed to conform list is not an 

“unlawful” delegation of authority. Federal agencies have always had responsibility for 

complying with the General Conformity requirements of CAA § 176(c)(1). By
22

providing agencies with a process for developing a presumed to conform list, EPA is 

merely following its statutory requirement to “promulgate, and periodically update, 

criteria and procedures” that agencies can use in determining conformity. CAA § 

176(c)(4). In enacting the General Conformity requirements, Congress included only the 

general requirement for EPA to promulgate such regulations, but did not limit the scope 

of the procedures or criteria that could be used to govern General Conformity

determinations. See CAA §§ 176(c)(4) (A) & (D). The ability to develop and rely upon 

a presumed to conform list is simply another tool EPA has provided for agencies to use in 

making those determinations, but the lists are not a replacement for EPA’s General 

Conformity regulations. EPA has promulgated the criteria and procedures for 

demonstrating conformity and clearly established the requirements agencies must comply

with in establishing a presumed to conform list, such that all activities covered by such 

lists would be anticipated to satisfy the statutory conformity requirements. Further, EPA 

has provided an additional process for rebutting the general presumption as appropriate 

where case specific facts indicate that the conformity criteria may not be met in a given 

instance. Likewise, EPA’s implementing regulations have always allowed states and 

tribes to account for certain conforming emissions in their SIPs, and allowing them to 

include a list of presumed to conform activities in their SIP is just another way of 

providing for such accounting. 

EPA does not believe it is necessary to provide any additional process for EPA oversight 

of the development of presumed to conform lists. Where federal agencies follow the 

procedures established in the rule for developing their presumed to conform lists, EPA 

concludes that such lists will satisfy the conformity provisions of the Act. EPA, states 

and the public can step in to participate in the development of presumed to conform lists 

under the provisions of the regulations and can also rebut the presumption in any

particular instance as appropriate. EPA believes these processes are sufficient to satisfy

the statute. Further, EPA does not believe the process for rebutting a presumption 

imposes significant burdens on commenters beyond those involved in any rulemaking. 

The process of establishing the presumed to conform list initially should exclude 

significant numbers of projects that might not conform, and participating in the 

conformity process to reveal facts rebutting a presumption of conformity in a given case 

is no different from the burden any public commenter bears in commenting on a 

conformity determination. Thus, providing this process for federal agencies to make the 

conformity process run smoother does not constitute an illegal delegation of federal 

authority and does not violates the Clean Air Act..

The concept of a central location to view the “presume-to-conform” actions may be a 

reasonable approach if and when a number of agencies develop lists. Since at the present 

time only one agency has published a list, such an approach is not necessary at this time. 

The EPA included the term “clearly demonstrate” in its 1993 regulations to mean that the 

demonstration is straightforward and transparent. 
23

§93.153 (i) and (j) Regionally significant emissions 

What EPA proposed: EPA proposed to remove requirements for federal agencies to 

conduct conformity determinations for actions with emissions below de minimis levels 

but that may be regionally significant actions (those actions with emission greater than 

10% of the emissions inventory for the nonattainment area). The proposal notes that 

these analyses have been conducted for 12 years and never shown a federal action with 

emissions below de minimis levels to meet the regionally significant criterion. 

Comment: Some commenters supported deletion of the regionally significant provision 

noting that it is unnecessary, not helpful in determining whether a federal action will 

conform to the SIP, and an administrative burden. Other commenters believed that the 

provision should be retained or strengthened to a more appropriate percentage of the 

area’s inventory. Some commenters also pointed out that in light of the new PM2.5 and 

8-hour ozone standards, there may come a point in the near future for federal projects that 

might become “regionally significant.” 

Response: EPA believes it is most beneficial to the overall conformity program to delete 

the regionally significant provision EPA believes that determinations of whether actions 

with emissions below the de minimis emission levels are regionally significant has been 

an administrative burden to some federal agencies with little or no environmental benefit. 

Moreover, EPA believes that strengthening the provision may add to the burden and add 

no benefit. Analysis discussed in the proposal showed that the emission inventory for 

most nonattainment and maintenance areas well exceeded the ten times the de minimis 

emission levels for the area, such that no de minimis emissions could actually be 

regionally significant. Although several commenters question whether the regionally

significant test might be important for the new PM2.5 and 8-hour ozone standards, they

presented no information to show that the de minimis emission levels would exceed 10 

percent of the inventory for potential nonattainment areas for those standards. However, 

EPA retains the authority and discretion to re-evaluate whether such a test may be 

appropriate after those new standards are established. 

§93.153 (i) Wildland fire 

What EPA proposed: EPA asked for comment on allowing federal agencies to presume 

that the emissions from prescribed burns will conform, provided the burning is conducted 

under a state certified smoke management program (SMP). EPA asked for comments on 

two approaches:

1. Prescribed fires conducted in compliance with a certified SMP are 

presumed to conform. 

2. In absence of a certified SMP, prescribed fires conducted using Basic 

Smoke Management Practices (BSMP) are presumed to conform.
24

Comment: The EPA received many comments in support of the first option, noting that it 

was reasonable to assume that any action conducted in compliance with the certified 

SMP would be in compliance with the SIP. One commenter thought that the presumption 

of conformity for burns conducted under BSMP is not acceptable because BSMP are in 

no way connected to air quality and will not ensure that resulting emissions from a 

prescribed burn would conform to the SIP. One commenter also noted that the use of 

SMPs may be acceptable, but EPA has not yet issued its final wildland fire policy. 

Another commenter suggested that if prescribed burns under certified SMPs or a BSMP 

are presumed to conform, there needs to be a simple way to flag the data from affected 

monitors. EPA also received a number of comments in support of the second option, 

which allows federal agencies to determine, in absence of a certified SMP, that 

prescribed fires conducted using BSMP are considered “presumed to conform” to the 

SIP. One commenter pointed out that prescribed fires are not the reason most areas are 

designated nonattainment. Some commenters noted that to be consistent with the 

Treatment of Data Influenced by Exceptional Events, if the state does not certify a SMP, 

the exemption should be for burns using state approved BSMP. Another commenter 

suggested that SMP and BSMP were not developed for nonattainment areas but to keep 

areas from becoming nonattainment areas based solely on smoke from fires. Finally, 

numerous commenters recommended that the definition of emergency episode include 

wildfires (unplanned ignitions). 

Response: After considering the various practices and the comments received, the EPA 

believes option 1 presented in the proposed rule is more appropriate and protective of the 

air quality than option 2. Therefore, the final rule will contain the requirements under 

option 1. Under option 1, prescribed fires conducted in compliance with a SMP are 

presumed to conform. The primary purpose of a SMP is to reduce emissions from 

prescribed burns, thus preventing deterioration of air quality and NAAQS violations, 

mitigating visibility impacts in mandatory Class I federal areas and mitigating the 

nuisance and public safety hazards (e.g., on roadways and at airports) posed by smoke 

intrusions into populated areas. EPA also notes that SMPs establish procedures and 

requirements for minimizing emissions. EPA believes such purposes and requirements 

are consistent with the underlying purpose of the General Conformity program. In 

addition, a SMP is only finalized after EPA and the public have had a chance to review 

the specific provisions included in it, thus providing another level of assurance that the 

program complies with the statutory requirements found in CAA section 176. EPA does 

not believe that the second approach contains assurances that emissions would not 

contribute to new violations or otherwise violate those statutory requirements.

However, EPA recognizes that prescribed fires employing BSMPs may be as protective 

of air quality in areas where no SMP exists, and thus explains in the preamble that an 

agency may rely on BSMPs to meet a presumption of conformity if such a presumption is 

established by an agency following the requirements of 93.153(g) or by a state following 

the requirements of 51.851(f), since those requirements assure the adequacy of the 

BSMPs to meet the legal requirements of the General Conformity program as outlined in 

section 176. 

Finally, EPA does not believe that the regulatory text specifically needs to identify
25

wildland fires as an emergency event that is exempt from General Conformity, since 

responses to natural disasters are already identified as exempt from conformity, but has 

added language to the preamble identifying wildfire responses as the type of situation that 

an agency may determine fits within the definition of emergency.

§93.153 (k) Grace period for newly designated nonattainment areas

What EPA proposed: The EPA is adding a requirement at 40 CFR 93.153(k) for the 

implementation of the statutory grace period for newly designated nonattainment areas. 

From the time that an area is designated as nonattainment, the statute provides that 

agencies will have a grace period of one year to take or start the federal action before the 

General Conformity requirements for the new designation are effective. If an agency

takes or starts the federal action before the end of the grace period, it must comply with 

the applicable pre-designation conformity requirements. If an agency takes or starts the 

federal action after the end of the grace period, it must comply with the post-designation 

conformity requirements. In describing the new term “take or start the federal action,” 

EPA is defining the term to mean that a federal agency takes an action when it signs a 

permit, license, grant or contract, or otherwise physically starts the federal action. If the 

agency intends to but fails to take or start the federal action during the grace period, then 

it must re-evaluate conformity for the project based on the requirements for the new 

designation and classification.

Comment: Several commenters supported the proposal to provide a grace period for the 

applicability of the General Conformity Regulations for newly designated nonattainment 

areas. One commenter recommended a 12 month grace period. Another recommended 

that the time period align with the 2-year grace period in the Transportation Conformity

Regulations. 

Other commenters opposed the proposal, suggesting that granting a 12 month grace 

period for federal actions could allow a significant increase in unmitigated emissions in 

an area newly designated as nonattainment based on emissions at a level without the 

federal action. The commenters noted the grace period could serve as a loophole and 

allow the implementation of a project that could further exacerbate the air quality

problem without accompanying offsets or mitigation measures.

Response: Congress established the one-year grace period when it revised the Clean Air 

Act, and EPA is revising the rules to clarify this statutory requirement. Accordingly, the 

final rule will contain this revision and cannot exclude or amend the statutory

requirement. The one year grace period also applies to transportation conformity under 

the statute.

§93.154 Federal agency conformity responsibility

Comment: Several commenters support the revisions to the regulations clarifying the 

handling of restricted information. Commenters believe that the definition of restricted 

information should state that emissions data cannot be restricted. Other commenters 
26

objected to the proposed definition of restricted information saying that the definition is 

redundant and unnecessary. 

Response: EPA believes that a clarification in the final rule will provide a clearer 

statement that restricted information does not have to be disclosed. Even though other 

statutes and regulations govern the release of restricted information, EPA believes it is 

important to reiterate that these regulations do not require the release of that information. 

EPA does agree that emission information cannot be considered “restricted information” 

in most circumstances, but does not agree that it needs to be stated in the regulation. 

§93.155 Reporting requirements

No comments were received on this section.

§93.156 Public participation

No comments were received on this section.

§93.157 Reevaluation of conformity

What EPA proposed: The EPA is adding a new paragraph (d) to §93.157 to clarify the 

need to conduct a new conformity determination when modifying an action for which the 

federal agency previously made a conformity determination. 

Comment: The commenter does not believe that EPA needs to define “modification” in 

the rule. The commenter noted that EPA provided the right amount of detail by stating 

that re-determination would be required if emissions increased above the de minimis 

threshold. If EPA does include a definition for “modification” in the rule, the commenter 

recommends that maintenance of actions previously determined to be conforming actions 

be exempt.

Response: The EPA believes that providing the definition for modification in the rule 

gives more clarity to the rule. The final rule will contain this definition. With regard to 

the suggestion that the final definition contain an exemption for previously determined 

conforming actions, such a change cannot be made since it was not included in the 

proposed rule. Moreover, we do not believe there is a basis for such an exemption – if 

there are no changes in the project emissions, the original conformity determination 

would remain in effect, but if there are changes to the project emissions, a revised 

determination accounting for the change would be required in order to conform with the 

requirements of CAA section 176(c). If the conformity determination has lapsed for the 

modification, then EPA believes that it is appropriate for the federal agency to conduct a 

new conformity evaluation.

 
27

§93.158 Criteria for determining conformity of general federal actions

What EPA proposed: In §93.158(a)(2) and (a)(5)(iii), EPA proposed to allow federal 

agencies to obtain emission offsets for the General Conformity requirements from a 

nearby nonattainment or maintenance area of equal or higher classification. The 

regulation requires such emissions offsets to be obtained through either an approved SIP 

revision or an equally enforceable commitment.

Comment: Commenters representing federal agencies, industry groups and some state air 

quality agencies supported the provision to allow offsets from nearby nonattainment or 

maintenance areas. Some of these commenters suggested that additional limits could be 

imposed on the use of the out-of-area offsets. Several commenters representing state air 

quality agencies opposed allowing offsets from other areas. The commenters noted that 

EPA regulations and federal court rulings limit the area from which emissions reductions 

can be creditable for attainment demonstrations. They also opposed allowing offsets 

because conformity generally applies to mobile source emissions that are different from 

stationary source emissions covered by NSR. 

Another commenter supported a provision that would allow the conformity determination 

to be based on compliance with a budget in reasonable further progress (RFP) SIPs. A 

commenter is concerned about the changes that would allow a conformity determination 

based on an RFP budget for years beyond the year for which the RFP demonstration 

exists. The commenter did not agree with the “flat line budget” approach identified in the 

proposed rule. The commenter believed there should be an alternative approach where 

future emissions levels are identified for the affected sources with collaboration with state 

and local agencies. A commenter noted that the role of using a photochemical model 

should be clarified.

Response: The EPA agrees that offsets should be allowed in nearby nonattainment areas 

in the same manner that they are allowed under the NSR program. Accordingly, EPA is 

adding a requirement that the nearby area contribute to the violations of the NAAQS in 

the area where the federal action is located or, in the case of a maintenance area, the 

emissions from the nearby area have contributed in the past to the violations in the area 

where the federal action is located. EPAs agree with the commenter that EPA regulations 

and judicial rulings place limits on the area from which emissions reductions can be 

creditable for attainment demonstrations. The intent of those limits is to ensure that the 

emissions from the nearby nonattainment area contribute to the violations, or have 

contributed to violations in the past, in the area in which the federal action takes place. 

This is consistent with the overall revisions to this regulation. Therefore, we are 

requiring in the final rule that federal agencies show that they have met the requirements 

of §93.158(a)(2) -- that the emissions offsets originate from an area that contributes to the 

violations, or have contributed to violations in the past, in the areas with the federal 

action -- by using the same techniques EPA approved by rule or guidance for 

demonstrating contributing emissions in other SIP-related programs for a particular 

pollutant or pollutant precursor. By limiting the offsets to areas that contribute or have 

contributed to the nonattainment, EPA is narrowing the potential offsets to areas that will 
28

result in a benefit to the nonattainment or maintenance area in which the federal action 

will take place. EPA also agrees that Transportation Conformity addresses mobile 

sources, but the same is not true for General Conformity. While there are some actions 

subject to the General Conformity Regulations that involve mobile sources only, a large 

number of other actions involve stationary and mobile sources.

To conduct conformity evaluations for emissions that occur beyond the period covered by 

the SIP or TIP, EPA stated that the federal agency should use a flat line approach, ie, 

assume that the emissions allowed in the last year of the SIP or TIP are continued. As an 

alternative, the federal agency can work with the state or tribe to allow greater emission 

from the action. In such a case, the state or tribe would have to submit a revision to the 

SIP or TIP to account for those changes. This alternative would allow the flexibility

while ensuring that the SIP or TIP addresses the future emissions.

Emissions of primary pollutants (those pollutants emitted directly to the atmosphere) can 

be effectively modeled to determine their affect on specific areas. However, the impact 

of precursor or secondary pollutants (those pollutants formed in the atmosphere) are 

much more difficult to model. Therefore, we believe that it is appropriate to limit the use 

of modeling the impact of photochemical models to providing general information on the 

pollution levels in the area and not use those models to predict the impact of specific 

precursor emissions. 

§93.158 (a)(5)(i)(C)

What EPA proposed: The EPA proposed to revise §93.158(a)(5)(i)(C) to allow a state or 

tribe to commit to including the emissions from the federal action in future SIPs. Under 

the existing regulations, federal agencies can demonstrate conformity by having the state 

commit to revising the applicable SIP to include the emissions. If a state or tribe agrees to 

such a commitment, the state or tribe must submit a SIP revision within 18 months to 

include the emissions from the action and to make other necessary adjustments in the SIP 

to accommodate those emissions. However, the existing SIP or TIP, or a SIP or TIP 

required to be submitted in 18 months, may not cover the same timeframe covered by the 

conformity determination. Accordingly, it was necessary to expand the regulatory

provision to also allow states to make commitments for future revisions. 

Comment: One commenter was concerned about allowing a state to make an enforceable 

commitment to include the emission in future SIPs without the consideration of potential 

impact on downwind states.

Response: In some cases, the federal action can cause direct and indirect emissions to be 

emitted over a number of years. That can lead the federal agency to address the impact of 

the emissions beyond the time period cover by the SIP or TIP. This revised provision 

addresses the demonstration of conformity in such a situation. When a state or tribe 

makes an enforceable commitment to include the emission from the federal action in a 

future SIP or TIP, it must evaluate those emissions in conjunction with all other 

emissions in the area as part of the SIP or TIP analysis. Such an evaluation whould 
29

include local as well as regional impacts, including downwind impacts. Therefore, for 

§93.158(a)(5)(i)(C) the final rule will allow a state or tribe to commit to including the 

emissions from the federal action in future SIPs on this basis.

§93.159 Procedures for conformity determinations of general federal actions 

No comments were received on this section.

§93.160 Mitigation of air quality impacts

No comments were received on this section.

§93.161 Conformity evaluation for federal installations with facility-wide emission 

budgets

What EPA proposed: To allow federal facilities expecting to expand or make 

modifications to negotiate a facility-wide emission budget in the SIP with the applicable 

air pollution control agencies. Actions taken that do not exceed these budgets would not 

need a conformity determination. The use of this approach is strictly voluntary where a 

state and federal agency agree to use it.

Comment: The majority of commenters supported the concept of the facility-wide 

emission budget approach with the appropriate consultation and input from the states. 

Many noted that it will not interfere with attainment of the NAAQS. However, some 

commenters disapproved of the budget approach and expressed concern about a federal 

agency/airport being allowed to establish its own budget without having to do additional 

analysis. One commenter noted that many activities involve the prediction of future 

emissions but once the federal action has taken place, the agency has limited control over 

these future emissions.

While generally agreeing with the approach, many commenters asked EPA for 

clarifications. Several commenters asked for clarification in the final rule that this is 

voluntary for both the federal agency and the states, and that states can opt to use the 

existing General Conformity approach. In addition, some commenters asked EPA to 

include provisions requiring such measures as periodic reporting of emissions, antibacksliding, and a requirement to obtain offsets if the budget is exceeded. Another 

commenter requested that on-site pollution prevention projects be required to occur 

contemporaneously with any proposed emission changes at the facility. Many 

commenters requested that EPA clarify the applicability of this provision to non-federal 

facilities (e.g., airports).

One commenter noted that a number of airports have worked with state and local 

agencies to include their emissions in the SIP. The commenter believes that these 

facilities should be grandfathered.
30

Another commenter stated that 161(a)(3) should be revised to require emission budgets 

for a pollutant be established for the same averaging time as the emission inventory used 

in the attainment demonstration for the pollutant.

A commenter believes that EPA should conduct a stakeholder discussion to address how 

often facilities are required to prepare budgets and the specific procedures and 

methodology that should be used to demonstrate conformity. The commenter also 

believes that the state should determine the level of documentation needed to identify that 

the emissions for a particular facility are in the SIP.

Response: The EPA agrees with most of the commenters that the facility-wide emissions 

budget approach, including the requirement to approve a facility-wide budget into the SIP 

or TIP, will not interfere with attainment of the NAAQS and will provide flexibility to 

the facilities in meeting the General Conformity requirements, while also providing 

assurances that the budgeted actions will not interfere with the applicable implementation 

plan. EPA believes that this approach benefits both the air regulatory agencies and the 

regulated facilities. State air quality agencies would benefit by having better emission 

estimates, including growth estimates from the installation and federal agencies would 

benefit by having the General Conformity process streamlined, reducing the amount of 

time it takes to demonstrate conformity. EPA is clarifying in the final rule that this 

approach is completely voluntary by both the state and the federal agency. If the state or 

tribe agrees to allow the facility to use the emission budget approach, it must ensure that 

the budget that it approves meets all applicable air quality requirements, such as 

attainment deadlines and RFP milestones. Accordingly, we are also encouraging the 

facilities and the state or tribe developing and approving such budgets to consult with 

other agencies or authorities as may be appropriate. For example, we encourage 

consultation with the local MPO if a facility-wide emissions budget includes on-road 

mobile emissions that might also be included in an MPO’s regional emissions analysis.

While the state or tribe must approve a facility-wide budget into the SIP or TIP, once 

they have done so, they cannot compel an agency to demonstrate conformity with another 

approach if the federal agency chooses to show conformity with the approved facilitywide emission budget. Federal agencies may use any approach to demonstrate 

conformity provided for in the rule. Facilities that are not federally controlled or 

operated, but are subject to federal approvals, permits or funding (such as airports and 

seaports) may work with the state to establish facility-wide emissions budget that can be 

used by a federal agency to satisfy its General Conformity responsibilities. The approval 

by the state of a facility-wide emissions budget into the SIP does not relieve the state of 

any obligations to meet any SIP or Clean Air Act requirements, milestones or deadlines.

Under the new section 93.161, the emission budget for the facility would be developed 

and adopted under the procedures used for SIP or TIP development. The state or tribe 

would establish the appropriate averaging time for the emission limitations, how often the 

budget should be prepared and the methodology used to prepare the budget. The level of 

documentation for the budgets should be the same as required for any SIP or TIP 

revision. Since the emission budget would be part of the SIP or TIP, any exceedances of 
31

the budget can be addressed by actions by the state, tribe or EPA under normal SIP/TIP 

enforcement procedures. In addition, if a facility exceeds its budget, the federal agency

cannot rely on that budget to demonstrate conformity. Where a facility has already 

negotiated a budget with the appropriate air quality agency, it can work with that agency

to have the budget adopted as part of the SIP or TIP under the final rules and use it for 

future conformity evaluations.

Finally, EPA is not specifying any periodic reporting requirements in the final rules. 

During the conformity evaluation, federal agencies would have to determine whether 

there are adequate emissions in the budget for the action under consideration. If 

emissions were not available, they could not use the budget to demonstrate conformity

and any reliance on a budget with an inadequate emissions could be addressed using the 

relevant enforcement provisions noted above. Moreover, there is nothing in the final 

rules which would prohibit states and tribes from conditioning their approval of the 

facility emissions budget on some type of reporting requirement.

Comment: One commenter felt that facilities with emission budgets should be required 

to implement pollution prevention measures before being allowed to use the approach.

Response: The emission budget approach allows federal agencies to manage their 

allotted budget by controlling emissions through various means, including pollution 

prevention measures. In adopting and including the emission budget for the facilities in 

their SIP or TIP, states or tribes should ensure that the budget represent good control 

techniques at the facility, which may, but is not required, to include pollution prevention 

measures. 

§93.162 Emissions beyond the time period covered by the SIP

No comments were received on this section.

§93.163 Timing of offsets and mitigation measures

What EPA proposed: In general, EPA has interpreted the existing regulations to mean 

that emission reductions from offsets and mitigation measures must occur in the same 

calendar year as the emission increases caused by the action, given that the total direct 

and indirect emissions from an action are calculated on an annual basis. Therefore, EPA 

has decided to include this interpretation in the regulations. In addition, EPA is adding a 

new section to this rule to address the timing of offset and mitigation measures. First, the 

section generally requires that the emission reductions from the offsets and mitigation 

measures must occur in the same calendar year as the emission increases caused by the 

federal action and that the reductions must be equal to the emissions increases. As an 

alternative, the new section would allow, under special conditions and consistent with 

CAA requirements, the state or tribe to approve other schedules for offsets or mitigation 

measures. EPA is requiring that emissions reductions used over an alternate schedule 

must be consistent with statutory requirements that new violations are not created, the 
32

frequency or severity of existing violations are not increased, and timely attainment or 

interim milestones are not delayed. Therefore, when a state or tribe approves an 

alternative schedule for emissions reductions, it is assuring that the increased emissions 

that occur during the period of the federal action do not violate any of the three Clean Air 

Act requirements described above.

To ensure that these non-contemporaneous emission reductions provide greater 

environmental benefits in the long term, EPA is requiring that the offset or mitigation 

ratios for alternative schedules be greater than one-for-one. Specifically, EPA is 

requiring a ratio that is no less than the applicable NSR offset ratios for the area. These 

ratios are readily available and already understood to be based on the severity of the 

nonattainment problem for the area.

Also, EPA believes that the mitigation or offset compensation period should not last 

indefinitely and is requiring that the period should not exceed two times the period of the 

higher emissions. For example, a federal agency may be supporting a construction 

project lasting 3 years in a serious nonattainment area and that project will cause 150 tons 

per year of increased emissions; the state or tribe can approve mitigation measures or 

offsets which reduce emissions by less than 150 tons per year provided the total reduction 

over a 6-year period is equal to or more than 540 tons (150 tons per year times 3 years 

equals 450 tons times the offset/mitigation ratio of 1.2 to 1 for serious nonattainment 

areas equals 540 tons).

Agreeing to allow the use of offsets or mitigation measures in later years does not exempt 

the state or tribe from timely meeting any of its SIP or TIP obligations, such as RFP 

milestones or attainment deadlines. Emissions reductions which accrue beyond the 

compensation period should be properly reflected in the SIP or TIP, e.g. through a SIP 

revision.

Comment: Several commenters representing federal agencies, industry and airports 

supported the flexibility in the timing of offsets and mitigation measures. The 

commenters believe that EPA needs to clarify what entity would determine whether the 

alternative time period for mitigation would trigger the three statutory factors for 

conformity and how such an entity would do so. One commenter recommended that the 

state or tribal agency responsible for the SIP be the appropriate entity. Another 

commenter requested that EPA clarify the use of emission reduction credits in such cases. 

In addition, a commenter urges EPA to reduce the offset ratios to no more than 1.2:1 in 

extreme nonattainment areas and to provide a fixed period of time for completing the 

emissions reductions recommending a 5-year compensation period to be included in the 

rule. 

Some commenters representing state and local air quality agencies objected to the 

alternate schedule provision for offsets. The commenters believe that mitigation 

measures and offsets must be contemporaneous and occur in the same calendar year as 

the emission increases. If EPA adopts the provision, the commenters suggested 

additional limitation on the use of the alternative schedule, such as a 3 year maximum 
33

time limit for the schedule and requiring more than a one-for-one offset.

Response: We believe that the approach for the alternative mitigation schedule, as 

proposed, provides flexibility for federal agencies to demonstrate conformity while 

providing some longer term environmental benefits. The rule requires that the 

nonattainment or maintenance areas to meet the Clean Air Act requirements during the 

period of higher emissions. Therefore, states and tribes would not be able to approve any

flexibility schedule if the higher emissions would interfere with their ability to make 

progress towards or attain the air quality standards. We believe that the increased 

uncertainty involved in the longer mitigation period justifies the use of the higher offset 

ratios and those ratios are consistent with other Clean air Act programs. Since state or 

tribal approval is required for the alternative schedule, those agencies have the ability to 

ensure that the alternative schedule not cause or contribute to a violation of the SIP or 

TIP. In addition, EPA has added additional wording to the final rule to clarify that the 

state or tribe is not compelled to approve a proposed alternate schedule for mitigation 

measures. 

§93.164 Inter-precursor mitigation measures and offsets.

What EPA proposed: The EPA is adding a new section to the regulations to allow the 

use of inter-precursor offset and mitigation measures where they are allowed by the SIP. 

The 1993 General Conformity regulations do not specifically allow or prohibit interprecursor offsets and mitigation measures. Therefore, EPA is revising the regulations to 

allow such offsets or mitigation measures if they are allowed by a state or tribe NSR or 

trading program approved in the SIP, provided they:

1. Are technically justified; and

2. Have a demonstrated environmental benefit.

The ratio for the offsets must be consistent with SIP or TIP requirements and EPA 

guidance.

Comments: Commenters from a wide range of affiliations supported the provision for 

inter-precursor offsets with some conditions. The commenters suggested that offsets 

should be allowed only with adequate technical support and appropriate ratios for interpollutant mitigation. Another commenter believes cross-pollutant offsets should be 

allowed. Others thought EPA should provide a guidance document on what states may

consider as reasonable tradeoffs and procedures for evaluating such tradeoffs at the same 

time as the final rule publication. Many believed the provisions should only be 

implemented with the full involvement and approval of the state, local or tribal air quality 

agency. Some commenters representing state air quality agencies objected to the 

provision for inter-precursor offsets but gave no reason for the objection.

Response: The EPA believes that allowing inter-precursor offsets will allow facilities 

flexibility in meeting the General Conformity requirements and agrees to change the 

regulations to allow for the trading of inter-precursor emissions only if two conditions are 

met. First, such trades must be allowed by the state or tribe in a SIP or TIP. The state 

must already allow for inter-precursor offsets or trading through a SIP-approved NSR 
34

program, transportation conformity program, or in the attainment or RFP demonstration 

to ensure conformance with a SIP or a TIP. Second, the trade must be technically

justified and have demonstrated environmental benefits. This technical justification and 

demonstration should be accomplished by showing the precursors are area specific and 

appropriate ratios are identified in the SIP. As needed, EPA will provide guidance on 

tradeoffs and procedures for evaluating such tradeoffs. However, we do not believe 

allowing cross-pollutants offsets would conform with the purposes of General 

Conformity under CAA § 176(c)(1)(B), since getting offsets of one criteria pollutant 

would not assure that the federal activity was not causing or contributing to a new 

violation, increasing the frequency or severity of an exiting violation, or delaying 

attainment of any standard for the pollutant actually emitted by the project (for example, 

getting CO offsets would not lessen the impact of the NOx emissions from a project).

§93.165 Early emission reduction credit programs at federal facilities and 

installations subject to federal oversight

What EPA proposed: The EPA is adding a new section to the regulations to establish an 

early emission reduction credit program for facilities subject to the General Conformity

Regulations. The existing regulations require that the offsets and mitigation measures be 

in place before the emissions increases caused by the federal action occur. However, 

under the existing regulations, emission reduction programs undertaken before the 

conformity determination is made could be considered as part of the baseline emissions 

and not available as offsets or mitigation measures for future actions subject to the 

General Conformity requirements. EPA believes the air quality could improve sooner 

and federal agencies and their project sponsors could benefit from the ability to reduce 

emissions in advance of the time that the reductions are needed for a conformity

evaluation, while at the same time meeting the goals of the SIP and TIP and expediting

the project level conformity process. 

Comment: Most commenters supported EPA’s proposal to allow the use of emission 

reduction credits (ERCs). One commenter thought that EPA should clarify when the 

emission reduction credits can be used. Several commenters disagreed with the proposal, 

citing concerns such as violations of conformity, the additional resources required to 

certify the ERC and track them over time, avoidance of formal conformity

determinations, and the lack of ability for states and the public to enforce the measures 

relied upon to generate emission reduction credits. One commenter suggested that the 

regulations allow for discrete emission reduction credits to be used for short-term 

emission offsets.

Response: The EPA believes that by allowing early ERCs, federal agencies will be 

encouraged to develop emission reduction programs before they are needed as offsets for 

conformity determinations. Since the emissions are accounted for on an annual basis, the 

unused credits would benefit the environment. The emission reduction programs could 

be implemented in conjunction with the action requiring the conformity determination. 

Therefore, the use of ERC would not encourage an agency to violate conformity, but 

instead would encourage compliance with the specific goals of the program. In any event, 
35

under this provision, all federal actions would need applicable offsetting reductions by

the time the conformity determination was made. EPA does not believe states will be 

required to use more resources since states and tribes are only required to verify the 

credits at the time they are used in a conformity evaluation, while the agency relying 

upon the credits is required to document that usage. Federal agencies would have to 

demonstrate that the credits are still valid at the time that they are used. In addition, there 

is no need to provide mechanisms to enforce the measures relied upon to produce those 

credits because the agency’s conformity determination cannot rely on ERCs that will be 

generated in the future – any ERCs must be generated in advance of the conformity

determination and the agency must verify the validity of the credits in the determination. 

Since discrete emission reductions credits are produced in one time period and used at a 

later time, they generally would not meet the requirements for conformity. Therefore, 

EPA is not including their use in the General Conformity program.

General Comments

Comment: A few commenters disagreed with the proposed regulations, opining that the 

revisions weaken an already weak rule. One commenter noted that federal agencies 

should be afforded no special opportunities and may not do less than non-governmental 

entities. One commenter stated that EPA should withdraw the proposal and work with 

state and local agencies along with other stakeholder groups to develop a General 

Conformity rule that is consistent with the intent of the Clean Air Act.

Response: The proposed revisions to the General Conformity Regulations do not weaken 

the rule – they continue to carry out the requirements of CAA section 176 while making

implementation of the program more efficient. EPA deleted some requirements (such as 

the regionally significant test) because they required federal agencies to expend resources 

without demonstrated environmental benefit. By eliminating such provisions, EPA is 

allowing the federal agencies to use their resources on items that have environmental 

benefits. The General Conformity Regulations do not exempt the federal agencies from 

other requirements of the Act. Therefore, these rules do not give special opportunities to

federal agencies or allow them to do less than non-governmental entities. EPA worked 

with a number of stakeholders including state and local agencies, tribal agencies, other 

federal agencies and industry associations in developing the revisions to the regulations.

Comment: One commenter noted that if many of the federal actions occur in low income 

communities and communities of color and the emissions are exempt from General 

Conformity analysis, the Agency may be violating Executive Order 12898 related to 

Environmental/Public Interest/Public Interest justice for federal actions.

Response: The commenter did not present any data to demonstrate that federal actions 

subject to the conformity requirements disproportionately affect low income communities 

and communities of color. In addition, all federal agencies are subject to Executive Order 

12898, so regardless of whether an agency is exempt from making a conformity
36

determination under these rules, that agency is not exempt from their responsibility under 

the Executive Order to protect those communities.

Transportation Conformity

Comment: Several commenters stated that transportation conformity does not protect the 

population near roadways. The commenters also stated that transportation conformity

does not protect children from environmental health and safety risks under Executive 

order 13045. The commenter also urged EPA to implement regulations that protect the 

health of adults. 

One commenter stated that transportation conformity needs to address the impacts on 

local receptors and that EPA should set national standards for carcinogens. 

Response: The EPA did not propose revisions to the Transportation Conformity

Regulations in this rulemaking, consequently these comments are not germane to this 

rulemaking.. Additionally, General Conformity Regulations are not designed to address 

transportation conformity issues. Both the General and Transportation Conformity

programs are designed to implement section 176(c) of the Clean Air Act. That section 

directs federal agencies not to interfere with the implementation of the national ambient 

air quality standards. The protection of children health and population near roadways 

should be addressed in the development of the state and tribal implementation plans.
37

Appendix A

List of Commenters

Docket 

ID Commenter Name Organization Sector

09 Adriano Martinez National Defense Council Environmental/PI

66 Alan Dozier GA Forestry Commission State/local

55 Alice Edwards AK DEC DAQ State/local

63 Angelo Logan East Yard Communities for Environmental Justice Environmental/PI

11 anonymous Citizen

12 anonymous Citizen

13 anonymous Citizen

14 anonymous Citizen

15 anonymous Citizen

16 anonymous Citizen

17 anonymous Citizen

64 B. Keith Overcash NC DENR State/local

22 B.Z. Karachiwala

Harris Co, TX Public Health and Environmental 

Services State/local

10 Barry Wallerstein South Coast Air Quality Management District State/local

40 Bill Becker NACAA State/local

46

Brock Nicholson, Lynne 

Liddington NACAA State/local

85 Dale Swedberg North Central Washington Prescribed Fire Council Land mgmt

74 Dale Wade Land mgmt

54 Dana Blume Port of Houston Authority Action proponent

32 Daniel C. Murray ID DEM State/local

50 Darryl Jones SC Forestry Commission State/local

72 David Lytle Ohio DNR Land mgmt

60 David Schanbacher TX CEQ State/local

93 Debbie Goettel City of Richfield, MN State/local

24 Donald Schregardus DOD Federal

57 Doug Voltolina The Nature Conservancy FL Chapter Environmental/PI

43 Elaine Chang South Coast AQMD State/local

27 Frank Santomauro DOD USACE Federal

45 George S. Aburn MDE State/local

67 Gerald Flannery Commerce City, CO State/local

80 Glenn Dowling GA Wildlife Federation/GA Prescribed Fire Council Land mgmt

28 Jaelith Hall-Rivera The Wilderness Society Environmental/PI

52 Jessica Steinhilber ACI-NA Action proponent

86 Jim Elleson WI Prescribed Fire Council Land mgmt

30 John E. Putnam Clark County (NV) Department of Aviation (CCDOA) Action proponent

87 John Kirksey TN Prescribed Fire Council land mgmt

84 John Stivers AL Prescribed Fire Council Land mgmt

51 Kevin Kessler WI DNR State/local

73 L. Keville Larson Larson & McGowin Land mgmt

90 Larry D. Nance AR Forestry Commission Land mgmt

33 Larry Greene SMAQMD State/local
38

Docket 

ID Commenter Name Organization Sector

83 Latimore Smith LA Prescribed Fire Council Land mgmt

44 Laurel Kroack IL EPA State/local

65 Lewis Wallenmeyer Clark County (Las Vegas) DAQEM State/local

92 Linda Choate City of Romulus, MI State/local

76 Lisa Allen MO Dept. of Conservation Land mgmt

23 Lisa Beal INGAA Utility

82 Mark A. Melvin National Coalition of Prescribed Fire Councils Land mgmt

38 Mary Uhl State of NM Air Quality Bureau State/local

42 Melinda Seely Air/Fair Environmental/PI

53 Michael Kapp Complete Wildlife Conservation, Inc. Environmental/PI

25 Nancy Wrona Arizona DEQ State/local

31 Nat Williams The Nature Conservancy Environmental/PI

34 Pamela F. Faggert Dominion Energy Utility

58 Robert Yuhnke EDF Environmental/PI

49 S. Paul Watts SC Prescribed Fire Council State/local

26 Sandra Silva DOI FWS Federal

75 Shannon Henry PA Prescribed Fire Council Land mgmt

48 Steven M. Taber Chevelier, Allen & Lichman State/local

81 Terry Sharpe NC Prescribed Fire Council Land mgmt

39 Thomas C. Edwards Newport Beach and Costa Mesa State/local

41 Thomas Fidler PA DEP State/local

61 Tim Pohle Air Transport Association Action proponent

47 Wib Owen NC DENR State/local

56 William O'Sullivan NJ DEP State/local

21 William R. Taylor DOI MMS Federal

36 NOISE Environmental/PI

70 US DOT Federal

88 MO DNR State/local