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6560-50-P

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 51 and 93

[EPA-HQ-OAR-2004-0491; FRL- ]

RIN 2060-AH93

Revisions to the General Conformity Regulations

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

SUMMARY: The EPA is revising its regulations relating to the 

Clean Air Act (CAA) requirement that federal actions conform to 

the appropriate state, tribal or federal implementation plan

(SIP, TIP, or FIP) for attaining clean air (“General 

Conformity”). EPA and other federal agencies have gained 

experience with the implementation of the existing regulations, 

which were promulgated in 1993 (and underwent minor revisions in 

2006) and have identified several issues with their 

implementation. In addition, in 2004, EPA issued regulations to 

implement the revised ozone National Ambient Air Quality 

Standards (NAAQS) and in 2007 issued regulations to implement 

the new fine particulate matter standard. State and other air 

quality agencies are in the process of developing revised plans 

to attain the new standards and the revisions to the General 

Conformity Regulations will be helpful to the state, tribe, and 

local agencies in developing and federal agencies in commenting 
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on the proposed SIPs revisions. This rule revision will also 

facilitate federal agency compliance with conforming its 

activities to the SIPs thereby preventing violations of the 

NAAQS. This rule revision provides for a timely and effective 

process for federal agencies and states and tribes to ensure 

federal activities are incorporated in these 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 SIP, TIP or FIP to attain or maintain the NAAQS.

DATE: This action is effective on [INSERT DATE 90 DAYS FROM

PUBLICATION IN THE FEDERAL REGISTER]

ADDRESSES: EPA has established a docket for this rulemaking 

under Docket ID No. EPA-HQ-OAR-2004-0491. All documents in the 

docket are listed in the www.regulations.gov index. Although 

listed in the index, some information is not publicly available, 

e.g., Confidential Business Information (CBI) or other 

information whose disclosure is restricted by statute. Certain 

other material, such as copyrighted material, is not placed on 

the Internet and will be publicly available only in hard copy. 

Publicly available docket materials are available either 

electronically in www.regulations.gov or in hard copy at the EPA 

Docket Center EPA/DC, EPA West, Room 3334, 1301 Constitution 

Avenue, Northwest, Washington, D.C. The Public Reading Room is 
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open from 8:30 a.m. to 4:30 p.m., Monday through Friday, 

excluding legal holidays. The telephone number for the Public 

Reading Room is (202) 566-1744, and the telephone number for the 

EPA Docket Center is (202) 566-1742. 

FOR FURTHER INFORMATION CONTACT: Mr. Thomas Coda, Office of Air 

Quality Planning and Standards, U.S. Environmental Protection 

Agency, Mail Code C539-02, Research Triangle Park, NC 27711, 

phone number (919) 541-3037 or by e-mail at coda.tom@epa.gov or 

Mr. H. Lynn Dail, Office of Air Quality Planning and Standards, 

U.S. Environmental Protection Agency, Mail Code C539-02, 

Research Triangle Park, NC 27711, phone number (919) 541-2363 or 

by e-mail at dail.lynn@epa.gov.

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does This Action Apply to Me?

 Entities affected by this rule include federal agencies and 

public and private entities that receive approvals or funding 

from federal agencies such as airports and seaports.

B. How is This Preamble Organized?

The information presented in this preamble is organized as 

follows:

Outline

I. General Information

A. Does This Action Apply To Me?

B. How is this preamble organized?
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C. When did EPA propose these revisions to the General 

Conformity Regulations?

 D. Where Can I Obtain Additional Information?

II. Background

A. What Is General Conformity and How Does It Affect Air 

Quality?

B. Why Is EPA Revising These Regulations at This Time?

III. How are the Existing Regulations Implemented?

 A. Applicability Analysis

B. Conformity Determination

C. Review Process

IV. Comments Submitted on the Proposed Rule

V. Summary of the Final Revisions and Clarifications of the

General Conformity Regulations

A. Overview of Revisions to the General Conformity 

Regulations

B. What Innovative and Flexible Approaches Are Being 

Finalized?

C. What Burden Reduction Measures Are Being Finalized?

D. What Revisions Provide Tools and Guidance for 

Transitioning to New or Revised NAAQS?

E. What Revisions Are Being Finalized at the Request of 

Other Agencies?

F. What Are Some of the Clarifications to the Existing 

Regulations That Are Being Finalized?

VI. Detailed Discussion of the Final Revisions to and 

Clarifications of the General Conformity Regulations

A. 40 CFR Part 51, Subpart W--Determining Conformity of 

General Federal Actions to State or Federal Implementation 

Plans

B. 40 CFR 93.150--Prohibition

C. 40 CFR 93.151--SIP Revision

D. 40 CFR 93.152--Definitions

E. 40 CFR 93.153--Applicability Analysis

F. 40 CFR 93.154--Federal Agencies Responsibility for a 

Conformity Determination

G. 40 CFR 93.155--Reporting Requirements

H. 40 CFR 93.156--Public Participation

I. 40 CFR 93.157--Re-evaluation of Conformity

J. 40 CFR 93.158--Criteria for Determining 

Conformity for General Federal Actions

K. 40 CFR 93.159--Procedures for Conformity Determinations 

for General Federal Actions

L. 401 CFR 93.160--Mitigation of Air Quality Impacts

M. 40 CFR 93.161--Conformity Evaluations for Installations 

With Facility-Wide Emission Budget

N. 40 CFR 93.162--Emissions Beyond the Time Period Covered 
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by the Applicable SIP or Tribal Implementation Plan (TIP)

O. 40 CFR 93.163--Timing of Offsets and Mitigation Measures

P. 40 CFR 93.164--Inter-Precursor Offsets and 

Mitigation Measures

Q. 40 CFR 93.165--Early Emission Reduction Credit Program

VII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

B. Paperwork Reduction Act

C. Regulatory Flexibility Act

D. Unfunded Mandates Reform Act

E. Executive Order 13132: Federalism

F. Executive Order 13175: Consultation and Coordination 

With Indian Tribal Governments

G. Executive Order 13045: Protection of Children From 

Environmental Health and Safety Risks

H. Executive Order 13211: Actions That Significantly Affect 

Energy Supply, Distribution, or Use

I. National Technology Transfer Advancement Act

J. Executive Order 12898: Federal Actions To Address 

Environmental Justice in Minority Populations and LowIncome Populations

K. Congressional Review Act

L. Judicial Review

VIII. Statutory Authority

C. When did EPA propose these revisions to the General 

Conformity Regulations?

The EPA proposed the revised General Conformity Regulations 

in the Federal Register on January 8, 2008 at 73 FR 1402. 

D. Where Can I Obtain Additional Information?

 In addition to being available in the docket, an electronic 

copy of this final rule is also available on the worldwide web. 

Following signature by the EPA Administrator, a copy of this 

notice will be posted at

http://www.epa.gov/oar/genconform/regs.htm.

II. Background
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A. What Is General Conformity and How Does It Affect Air 

Quality?

The intent of the General Conformity requirement is to 

prevent the air quality impacts of federal actions from causing 

or contributing to a violation of the NAAQS or interfering with 

the purpose of a SIP, TIP, or FIP.

In the CAA, Congress recognized that actions taken by 

federal agencies could affect state, tribal, and local agencies' 

ability to attain and maintain the NAAQS. In section 176(c)(42 

U.S.C. 7506) of CAA, Congress established requirements to ensure 

federal agencies proposed actions conform to the applicable SIP, 

TIP or FIP for attaining and maintaining the NAAQS. That 

section requires federal entities to find that the emissions 

from the federal action will conform to the purposes of the SIP, 

TIP or FIP or not otherwise interfere with the state's or 

tribe's ability to attain and maintain the NAAQS.

The CAA Amendments of 1990 clarified and strengthened the 

provisions in section 176(c). Because certain provisions of 

section 176(c) apply only to highway and mass transit funding 

and approval actions, EPA published two sets of regulations to 

implement section 176(c). The Transportation Conformity 

Regulations, first published on November 24, 1993 (58 FR 62188) 

and recently revised on July 1, 2004 at 69 FR 40004, May 6, 2005 

at 70 FR 24280 and March 10, 2006 at 71 FR 12468, and January 
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24, 2008 at 73 FR 4420, address federal actions related to 

highway and mass transit funding and approval actions. The 

General Conformity Regulations, published on November 30, 1993 

(58 FR 63214), cover all other federal actions.

B. Why Is EPA Revising These Regulations at This Time?

On July 17, 2006 at 71 FR 40420, EPA revised the General 

Conformity Regulations to include de minimis emission levels for 

particulate matter with an aerodynamic diameter equal to or less 

than 2.5 microns (PM2.5) and its precursors. Otherwise, EPA has 

not revised the General Conformity Regulations since they were 

promulgated in 1993. Since that time, EPA and other federal 

agencies have gained experience with the implementation of the 

existing regulations and have identified several issues with 

their implementation. Therefore, EPA initiated a process to 

review, revise and streamline the regulations. In addition, EPA 

is in the process of developing regulations to implement the 

revised ozone standard and regulations to implement the new 

particulate matter standard. In the near future, state and 

local air quality agencies will be required to develop revised 

SIPs to attain these new standards. Knowledge of the revised 

General Conformity Regulations will be helpful to the state, 

tribal, and local agencies in the SIP development process as 

well as the federal agencies in commenting on the proposed SIP 

revisions. This rule revision will also facilitate federal 
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agency compliance with conforming its activities to the SIPs and

thereby preventing violations of the NAAQS. 

III. How are the Existing Regulations Implemented?

Federal agencies and other parties involved in the 

conformity process have found that in implementing the existing 

General Conformity Regulations their process falls into three 

phases: (A) Applicability analysis, (B) Conformity 

determination, and (C) Review process. Besides ensuring that 

the federal actions are in conformance with the SIP, the 

regulations encourage consultation between the federal agency 

and the state or local air pollution control agencies before and 

during the environmental review process.

The existing regulations do not specifically identify the 

roles of Indian tribes in the General Conformity process or the 

connection between the regulations and TIPs. In the revised 

regulations, EPA has specifically identified tribal agencies as 

stakeholders in the conformity process such as requiring 

specific notification for any federally recognized tribes in the 

nonattainment or maintenance area where the action is occurring. 

In addition, the revised regulations also clarify that federal 

actions must conform to any applicable TIP.

A. Applicability Analysis

The National Highway System Designation Act of 1995 (Pub. 

L. 104-59) added section 176(c)(5) to the CAA to limit 
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applicability of the conformity programs only to areas 

designated as nonattainment under section 107 of the CAA and 

maintenance areas established under section 175A of the CAA.

Therefore, only actions which cause emissions in designated 

nonattainment and maintenance areas are subject to the 

regulations. In addition, the regulations recognize that the 

vast majority of federal actions do not result in a significant 

increase in emissions and, therefore, include a number of 

exemptions such as de minimis emission levels based on the type 

and severity of the nonattainment problem.

In the applicability analysis phase, the federal agency 

determines:

1. Whether the action will occur in a nonattainment or 

maintenance area;

2. Whether one or more of the specific exemptions apply to 

the action;

3. Whether the federal agency has included the action on 

its list of “presumed to conform” actions; 

4. Whether the total direct and indirect emissions are 

below or above the de minimis levels; and/or

5. Where the facility has an emission budget approved by 

the state or tribe as part of the SIP or TIP, the federal agency 

determines if the emissions from the proposed action are within 

the budget.
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If the action will cause emissions above the de miminis in 

any nonattainment or maintenance area and the action is not 

otherwise exempt, “presumed to conform,” or included in the 

existing emissions budget of the SIP or TIP, the agency must 

conduct a conformity determination before it takes the action.

B. Conformity Determination

When the applicability analysis shows that the action must 

undergo a conformity determination, federal agencies must first 

show that the action will meet all SIP control requirements such 

as reasonably available control measures, and the emissions from 

the action will not cause a new violation of the standard, or 

interfere with the timely attainment of the standard, the 

maintenance of the standard, or the area's ability to achieve an 

interim emission reduction milestone. Federal agencies then 

must demonstrate conformity by meeting one or more of the 

methods specified in the regulation for determining conformity:

1. Demonstrating that the total direct and indirect 

emissions are specifically identified and accounted for in the 

applicable SIP,

2. Obtaining a written statement from the state, tribe or 

local agency responsible for the SIP or TIP documenting that the 

total direct and indirect emissions from the action along with 

all other emissions in the area will not exceed the SIP emission 

budget,
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3. Obtaining a written commitment from the state or tribe 

to revise the SIP or TIP to include the emissions from the 

action,

4. Obtaining a statement from the metropolitan planning 

organization (MPO) for the area documenting that any on-road 

motor vehicle emissions are included in the current regional 

emission analysis for the area's transportation plan or 

transportation improvement program,

5. Fully offsetting the total direct and indirect emissions 

by reducing emissions of the same pollutant or precursor in the 

same nonattainment or maintenance area, or

6. Conducting air quality modeling that demonstrates that 

the emissions will not cause or contribute to new violations of

the standards, or increase the frequency or severity of any 

existing violations of the standards. Air quality modeling 

cannot be used to demonstrate conformity for emissions of ozone 

precursors or nitrogen dioxide (NO2). As stated in EPA's 

proposal of the 1993 regulations (58 FR 13845), due to the 

complex interaction of the ozone precursors, the regional nature 

of the ozone and NO2 problems, and limitations of current air 

quality models, it is not generally appropriate to use an air 

quality model to determine the impact on ozone or NO2

concentrations from a single emission source or a single federal 

action.
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C. Review Process

As public bodies, federal agencies must make their 

conformity determinations through a public process. The General 

Conformity Regulations require federal agencies to provide 

notice of the draft determination to the applicable EPA Regional 

Office, the state and local air quality agencies, the local MPO 

and, where applicable, the Federal Land Manager(s)(FLM). In 

addition, the regulations require federal agencies to provide at 

least a 30-day comment period on the draft determination and 

make the final determination public. State agencies and the 

public can appeal the final determination in the U.S. Courts 

system. Failure by a federal agency to follow the substantive

and procedural General Conformity requirements can result in an 

adverse court decision if challenged.

IV. Comments Submitted on the Proposed Rule

The proposed rule on the “Revisions to the General 

Conformity Regulations” was issued on January 8, 2008 (73 FR 

1402). The EPA received 65 letters from state and local 

governments, federal agencies, environmental groups, and private 

citizens commenting on the proposed regulations. Some of the 

comments are discussed in section VI of this notice as they were 

relevant to the detailed discussion of revisions. The EPA has 

included a response to comments document which addresses all of 
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the timely comments received on the proposed rule in the docket 

of this rulemaking action (See Docket No. EPA-HQ-OAR-2004-0491).

V. Summary of the Final Revisions and Clarifications of the 

General Conformity Regulations

A. Overview of Revisions to the General Conformity Regulations

In accordance with the requirements of section 

176(c)(4)(C) of the CAA, when EPA promulgated General Conformity 

Regulations in 1993 in 40 CFR 93 subpart B (sections 150 to 160) 

it also promulgated regulations at 40 CFR part 51, subpart W 

(sections 850-860) which required states to adopt and submit 

SIPs for General Conformity. In August 2005, Congress passed 

the Safe, Accountable, Flexible, Efficient Transportation Equity 

Act: A Legacy for Users (SAFETEA-LU) which eliminated the 

requirement for states to adopt and submit General Conformity 

SIPs. Therefore, EPA is revising its regulations to make the 

adoption and submittal of the General Conformity SIP or TIP 

optional for the state or tribe.

Because 40 CFR part 51, subpart W (§§51.850-51.860) 

essentially duplicates the regulations promulgated at 40 CFR 

part 93, subpart B (§§93.150-93.160), EPA is deleting all of 

subpart W except for §51.851. In the revision to §51.851, EPA 

is requiring that if a state or tribe submits a General 

Conformity SIP or TIP that it be consistent with the 

requirements of 40 CFR part 93, subpart B. The EPA added 
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paragraph (f) to 40 CFR 51.851 to allow the states and tribes to 

develop their own “presumed to conform” list for actions covered 

by their conformity SIPs or TIPs.

In 40 CFR part 93, subpart B, EPA is making specific 

revisions to the regulations which (1) clarify the process, (2) 

delete outdated or unnecessary requirements, (3) authorize 

innovative and flexible approaches, (4) reduce the paperwork 

burden, (5) provide transition tools for implementing new 

standards, (6) address issues identified by implementing 

agencies, and (7) provide a better explanation of regulations 

and policies.

Several of the revisions encourage both the federal 

agencies and the states or tribes to take actions in advance of 

the project environmental review. Such advance action should 

speed the review process for the individual projects and reduce 

the delays for the project without impairing the environmental 

review. This is discussed in more detail in section VI below.

B. What Innovative and Flexible Approaches Are Being Finalized?

1. The EPA is adding a new section (40 CFR 93.161) to 

allow for a facility-wide emission budget approach. Under this 

voluntary arrangement, federal agencies, in anticipation of 

future major actions, may negotiate a facility-wide emission 

budget with the appropriate state, tribal, or local air quality 

agency responsible for the SIP or TIP. The state, tribal, or 
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local agency could incorporate the facility-wide emission budget 

into the applicable SIP or TIP and submit it to EPA for 

approval. After EPA approves the SIP or TIP, any action at the 

facility can be “presumed to conform” provided that the 

emissions from the proposed action along with all other 

emissions at the facility are within the EPA approved facilitywide emission budget and a conformity determination would not be 

necessary. Alternatively, a facility with an approved facilitywide emission budget could demonstrate conformity by the 

conventional methods afforded in the General Conformity 

Regulations. For example, once approved, minor actions under 

the control of the facility where an applicability analysis 

results in a determination that the emissions are below a de 

minimis threshold could proceed with no conformity 

determination.

2. The EPA is adding a new section (40 CFR 93.165) to 

explicitly incorporate the use of early emission reduction 

credits into the regulations. The proposal reflects the 

provisions established by Congress in Federal Aviation 

Administration (FAA) Reauthorization Act of 2003 for the Airport 

Early Emission Reduction Credit (AERC) program and the guidance 

to implement that program. The revised regulations provide a 

similar framework for other federal agencies.
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3. The EPA is adding a new section (40 CFR 93.164) to 

allow, with certain limitations, the emission of one precursor 

of a criteria pollutant to be mitigated or offset by the 

reduction in the emissions of another precursor of that 

pollutant.

4. The EPA is adding a new section (40 CFR 93.163) to 

allow alternate schedules for mitigating emissions increases. 

The mitigation timing approach allows some flexibility for 

federal agencies and states or tribes to negotiate a program for 

some emissions mitigation to occur in future years. States or 

tribes can allow this approach to accommodate short-term 

increases in emissions if they believe a substantial long-term 

reduction in emissions will result from a federal action.

C. What Burden Reduction Measures Are Being Finalized?

1. The EPA is deleting the provision in the existing 

regulation (40 CFR 93.153) that required federal agencies to 

conduct a conformity determination for regionally significant 

actions where the direct and indirect emissions of any pollutant 

represent 10 percent or more of a nonattainment or maintenance 

area’s emissions inventory for that pollutant, even though the 

total direct and indirect emissions from the actions were below 

the de minimis emission levels or the actions were otherwise 

“presumed to conform”.
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2. The EPA is adding in 40 CFR 93.153 new types of actions 

that federal agencies can include in their “presumed to conform” 

lists and EPA is also permitting states or tribes to establish 

in their General Conformity SIPs or TIPs “presumed to conform” 

lists for actions within their state or tribal area.

3. The EPA is finalizing an exemption in 40 CFR 93.153 for 

the emissions from stationary sources permitted under the minor 

source New Source Review (NSR) programs similar to the EPA's 

existing General Conformity regulation which already provides 

for exemptions for emissions from major NSR sources.

D. What Revisions Provide Tools and Guidance for Transitioning 

to New or Revised NAAQS?

1. The EPA is adding a definition in the regulation (40 

CFR 93.152) for “Take or start the Federal action” to help 

federal agencies determine what, if any, conformity requirements 

apply when an area is designated or re-designated as 

nonattainment.

2. The EPA is adding requirements 40 CFR 93.153(k) for the 

implementation of the statutory grace period for newly 

designated nonattainment areas.

3. The EPA is adding alternate methods (40 CFR 93.162) to 

demonstrate conformity for time periods beyond those covered by 

the SIP or TIP. The EPA is also allowing states or tribes to 
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include an enforceable commitment in the SIP or TIP to address 

future emissions from a federal action.

E. What Revisions Are Being Finalized at the Request of Other 

Agencies?

1. As part of EPA's efforts to finalize an Air Quality 

Policy on Wildland and Prescribed Fires, which was undertaken in 

consultation with FLMs, EPA took comment on two possible 

approaches: To include a presumption of conformity for (1)

prescribed fires conducted in accordance with a state certified 

smoke management programs (SMPs) which meets the requirements of 

EPA’s Interim Air Quality Policy on Wildland and Prescribed 

Fires or an equivalent replacement EPA policy, or (2) prescribed 

fires conducted in accordance with a state certified SMPs which 

meets the requirements of EPA’s Interim Air Quality Policy on 

Wildland and Prescribed Fires or an equivalent replacement EPA 

policy or, in the absence of a stated certified SMP, where the 

federal agency has obtained written assurance from the state 

prior to the burn that the planned burn employs state approved

basic smoke management practices (BSMP). EPA is finalizing 

option 1 to include a presumption of conformity for prescribed 

fires that are conducted in compliance with SMPs (40 CFR 

93.153(i)(2)), with recognition that prescribed fires employing 

BSMPs may be able to meet a presumption of conformity if such a 

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

requirements of 51.851(f). In the absence of such SMPs, we

encourage states and federal agencies to work together to 

develop and finalize SMPs or to include prescribed fires

conducted in accordance with BSMPs as presumed to conform 

actions in the applicable SIP. In addition, federal agencies 

could undertake actions in accordance with 40 CFR 93.153(f) and 

(g) to include prescribed fires conducted in accordance with 

specific BSMPs as actions that are presumed to conform.

2. The EPA is finalizing the proposal (40 CFR 93.158) to 

allow federal agencies to obtain emission offsets for general 

conformity purposes from another nearby nonattainment or 

maintenance area of equal or higher nonattainment classification 

provided the emissions from that area contribute to violation of 

the NAAQS in the area where the federal action is located or, in 

the case of maintenance areas, the emissions from the nearby 

area contributed in the past to the violations in the area where 

the federal action is occurring.

3. At the request of several federal agencies, EPA is 

clarifying the language in the regulation that states that 

nothing in these regulations (40 CFR 93.155 and 40 CFR 93.156) 

requires the release of materials and other information where 

disclosure is restricted by law. Also, EPA is including a 

similar clarification for CBI.
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4. Several federal agencies and others involved in the 

General Conformity process suggested that EPA should consider 

exempting construction activity emissions from the conformity 

regulations requirements(40 CFR 93.153). Although the existing 

General Conformity Regulations do not specifically mention 

construction emissions, they implicitly require federal agencies 

to include emissions from construction activities in the 

conformity evaluation. 

The EPA understands these concerns and, in the discussion 

about the revision to the definition of “caused by,” has 

identified a number of ways that federal agencies can work with 

the state, tribe, and local agencies to address construction 

emissions in the General Conformity assessment. However, EPA is 

not finalizing an exemption for construction emissions in the 

revisions and is instead affirming that emissions from 

construction activities must be considered in a conformity 

evaluation. 

5. At the request of the FAA, EPA is codifying one of the 

examples contained in the preamble to the existing General 

Conformity Regulations (58 FR 63229) that stated “the EPA 

believes that the following actions are illustrative of de 

minimis actions: * * * Air traffic control activities and 

adopting approach, departure and enroute procedures for air 

operations.” The FAA conducted a study of ground level 
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concentrations caused by elevated aircraft emissions released 

above ground level (AGL) using EPA-approved models and 

conservative assumptions.1 The study concluded that aircraft 

operations at or above the average mixing height of 3,000 feet 

AGL have a very small effect on ground level concentrations and 

could not directly result in a violation of the NAAQS in a local 

area. Consequently, this study supports the example provided in 

EPA's initial preamble language for air traffic control 

activities and adopting approach, departure and enroute 

procedures for aircraft operations above the mixing height. As 

some of the commenters noted, the mixing height for some areas 

can vary and some SIPs and TIPs identify a specific mixing 

height to be used. Therefore, EPA’s final rule (40 CFR 93.153) 

exempts as de minimis aircraft emissions above the specific 

mixing height identified in the SIP or TIP. If no mixing height 

is identified in the SIP or TIP, the federal agency can use 

3,000 feet AGL as a default mixing height. The list of 

exemptions under 40 CFR 93.153(c)(2)(xxii) has been updated in 

this final rule to reflect this policy.

 

1

Wayson, Roger, and Fleming, Gregg, ``Consideration of Air 

Quality Impacts by Airplane Operations at or Above 3000 feet 

AGL,'' Volpe National Transportations Systems Center and FAA 

Office of Environment & Energy, FAA-AEE-00-01-DTS-34, September 

2000. 

http://www.faa.gov/regulations_policies/policy_guidance/envir_po

licy/
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F. What Are Some of the Clarifications to the Existing 

Regulations That Are Being Finalized?

1. 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. The emissions in each area would be treated as 

if they result from a separate action.

2. The EPA is establishing procedures in 40 CFR 93.153 to 

follow in extending the 6-month conformity exemption for actions 

taken in response to an emergency.

3. The EPA is revising (40 CFR 93.158) the procedures that 

can be used to demonstrate conformity with the applicable SIP

when the SIP does not contain an attainment demonstration or 

when the emissions from the federal action are projected beyond 

the period of the SIP. In addition, EPA is adding a new section 

(40 CFR 93.162) to establish procedures for demonstrating 

conformity beyond the time period covered by the SIP or TIP.

4. The EPA is revising the review process (40 CFR 93.155) 

to require federal agencies to notify tribal governments in the 

nonattainment or maintenance area of General Conformity 

evaluations.

5. The EPA is clarifying the definition (40 CFR 93.152) of 

several terms used in the regulations.
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6. The EPA is including specific language through out the 

regulations to identify the role of Indian tribes and TIPs in 

the General Conformity evaluation.

VI. Detailed Discussion of the Final Revisions to and 

Clarifications of the General Conformity Regulations

A. 40 CFR Part 51, Subpart W--Determining Conformity of General 

Federal Actions to State or Federal Implementation Plans

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 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. Therefore, EPA is revising 40 CFR 51.851 

to make the adoption and submittal of the General Conformity SIP 

optional for the state and eligible federally-recognized tribal
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governments.

In promulgating the General Conformity Regulations in 1993, 

EPA published two sets of regulations: 40 CFR Part 51, subpart W 

(§§51.850 through 51.860) directed states to adopt and submit 

General Conformity SIPs to EPA for approval and 40 CFR Part 93 

subpart B (§§93.150 through 93.160) provided the requirements 

for federal agencies to follow in conducting their conformity 

evaluations before EPA approved the General Conformity SIP for 

the area. Section 40 CFR 51.851 directed states to adopt SIPs 

meeting the requirements of 40 CFR part 51, subpart W. The other 

sections in subpart W repeated the requirements found in 40 CFR 

part 93, subpart B. The EPA is deleting 40 CFR 51.850, and 

§§51.852 through 51.860 since those sections merely repeated the 

language in 40 CFR 93.150 and §§93.152 through 93.160 and is 

including a requirement in 40 CFR 51.851(a) that the General 

Conformity SIP or TIP, if adopted, must meet the requirements in 

40 CFR part 93, subpart B.

In addition, EPA is restructuring §51.851.

1. The EPA is dividing paragraph (b) of 40 CFR 51.851 into 

four paragraphs--(b), (c), (d), and (e):

a. Paragraph (b) now states that until EPA approves the 

General Conformity SIP, federal agencies must meet the 

requirements of 40 CFR part 93, subpart B.

b. Paragraph (c) states that after EPA approves a SIP or 
25

TIP meeting the requirement of 40 CFR part 93, subpart B, or 

portion thereof, the federal agencies must meet the requirements 

of the SIP or TIP and any other portions of 40 CFR part 93, 

subpart B if not contained in the approved SIP or TIP. In 

addition, paragraph (g) states that any conformity requirements 

in an existing implementation plan remain enforceable until the 

state submits and EPA approves a revision to the applicable 

state implementation plan to specifically remove the conformity 

requirements. Since there is no longer a requirement for SIPs

to include conformity requirements and the applicable statutes 

do not grant EPA additional authorities to condition approval of 

a state's request to remove the General Conformity requirements 

from an implementation plan, it is EPA's intent, once requested 

by a state, to expeditiously review and approve implementation 

plan revisions that seek to remove General Conformity 

requirements.

c. Paragraph (d) contains the requirement that the SIP or 

TIP can be no less stringent than 40 CFR part 93, subpart B.

d. Paragraph (e) contains the requirement that the SIP or 

TIP can be no more stringent that the requirement in 40 CFR part 

93, subpart B unless the provisions apply equally to non-federal 

as well as federal entities.

2. The 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 
26

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. 

Another commenter supported the requirements for states to 

develop conformity SIPs.

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. If a state does not have a conformity SIP, then 

federal agencies must conduct their evaluation under the 

requirements of 40 CFR 93.150-93.165. These requirements are 

essentially the same as the requirements contained in the 

conformity SIPs. Therefore, there would be little difference in 

the enforceability of the regulations. Mitigation measures are 
27

included in the SIP or TIP. A conformity SIP is not needed to

include the mitigation measures in the SIP or TIP. They are 

included in the SIP to attain or maintain the ambient air 

quality standards. Section 93.160 has been changed by deleting 

the term “General Conformity Regulations” to ensure this fact is 

clear.

B. 40 CFR 93.150--Prohibition

Section 93.150 establishes the general prohibition against 

federal agencies taking actions that do not conform with the SIP 

and requirements for the federal agencies to make the conformity 

determinations following the procedures of subpart B of part 93. 

The EPA is making two revisions to §93.150. First, EPA is 

deleting the language in paragraph (c) of that section and 

reserving that paragraph. Second, EPA is adding a new paragraph 

(e) to the section to state that if an action occurs in more 

than one nonattainment area, that each area must be evaluated 

separately.

In paragraph (c) of the 1993 regulations, EPA identified 

categories of actions that were not subject to the regulations 

based on environmental review for the action that was either 

completed or underway at the time the regulations were 

promulgated. The paragraph was based on the environmental 

reviews (either the conformity determination or the National 

Environmental Policy Act (NEPA) analysis) being completed in 
28

early 1994. Therefore, paragraph (c) was outdated and not 

necessary at this time.

In the new paragraph (e) in §93.150, EPA is clarifying the 

regulations to state specifically that conformity determinations 

must be made for each nonattainment or maintenance area in which 

emissions from the federal action occur. The emissions from most 

federal actions or projects occur within one nonattainment or 

maintenance area; however, some actions or projects could extend 

across area boundaries, causing emissions in more than one area.

A facility (for example, a national park, military installation 

or an airport) could be located in multiple counties or in 

multiple states. Emissions from an action at such facilities 

could extend across the nonattainment or maintenance area 

boundaries. Some federal actions could result in direct or 

indirect emissions in non-contiguous areas, or even nationwide, 

that are above the de minimis thresholds and affect multiple 

nonattainment or maintenance areas. The 1993 regulations did 

not specify how actions or projects affecting multiple areas 

should be addressed. Therefore, EPA added paragraph (e) to 

state that an action's emissions in each area would be treated 

as if they result from separate actions.

The EPA clarified that emissions from actions be treated 

separately for each nonattainment and maintenance area for the 

following reasons:
29

1. Federal agencies demonstrate conformity to a SIP, TIP or 

FIP that are developed on an area-specific basis and SIP 

requirements may vary from one area to another.

2. The General Conformity Regulations exemptions are also 

area-specific. For example, the de minimis levels are based 

upon the type and classification of the nonattainment or 

maintenance area.

3. Section 176(c)(5) of the CAA limits the applicability of 

the conformity regulations to actions in nonattainment and 

maintenance areas. Therefore, actions, which affect broad 

regions encompassing several nonattainment, maintenance or 

attainment areas, must be evaluated based only on the portions 

of the emissions in the nonattainment and maintenance areas.

C. 40 CFR 93.151—SIP Revision

The main purpose of §93.151 is to specify that the 

regulations in part 93 subpart B apply to federal actions unless 

the state or tribe adopts and EPA approves a General Conformity 

SIP or TIP for the area. The EPA did not change the purpose of 

the section, but is revising the section to clarify its wording. 

The 1993 regulations included statements about the stringency of 

the SIP compared to the requirements in subpart B of part 93.

The EPA is deleting those statements because they duplicate 

statements in 40 CFR 51.851 which specifies the requirements for 

the SIP and TIP.
30

D. 40 CFR 93.152--Definitions

Section 93.152 provides the definition of terms used in the 

regulations. The EPA is revising 12 of the definitions, adding 

11 new terms, and deleting one term, and clarifying the scope of 

an existing definition as follows:

Applicability analysis. 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.

Applicable implementation plan or applicable SIP. The EPA 

is making two minor revisions to the definition. First, EPA is 

correcting the citation for the SIP approval and second, EPA is 

clarifying the definition by adding a parenthetical phrase to 

clarify that the term includes an approved TIP. The 

requirements for eligible tribes are found in 40 CFR 49.6.

Area-wide air quality modeling analysis. The EPA is 

clarifying this definition by making a minor wording change and 

by including photochemical grid model in the definition. Also, 

EPA is adding an example of the type of models that could be 

used for the area-wide air quality modeling analysis.

Caused by. 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 the General Conformity Regulations were promulgated in 

1993, EPA has interpreted the regulations to require a federal 
31

agency to include construction emissions in its conformity 

analysis. The EPA believes that emissions from construction 

activities initiated by, 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 that construction emissions can 

contribute significantly to particulate matter (PM) exceedances, 

especially off-road vehicle emissions. Some believed 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. However, some commenters thought that 

construction emissions should be exempted. They noted 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 
32

emissions. They also pointed out that construction emissions 

are generally not included in NSR or Transportation Conformity 

evaluations. 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.

Response: The EPA agrees with the majority of commenters on 

this issue that construction emissions can contribute 

significantly 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 action 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, and 

secondarily concerned with short-term and localized impacts. 

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 above, EPA believes that emissions from construction 
33

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 should 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 the emissions occurred.

Confidential business information (CBI). In §§93.155 and 

93.156, EPA is clarifying how CBI used in the conformity 

determination is to be handled. To support those provisions, 

EPA is adding a definition of CBI. The definition is based upon 

that used to define CBI under the Freedom of Information Act.

Conformity determination. The EPA is adding a new term to 

describe the decision that a federal agency official makes in 

determining that the action will conform with the SIP, TIP or 
34

FIP.

Conformity evaluation. The EPA is adding a new definition 

to describe the entire conformity analysis process from the 

applicability analysis through the conformity determination, if 

necessary.

Continuing program responsibility. In the 1993 

regulations, EPA used the term “emissions that a federal agency 

has a continuing program responsibility for.” That term was 

awkward and confusing. The EPA is shortening the term to the 

“continuing program responsibility” and reformatting the 

definition to make it clearer.

Continuous program to implement. This term was used in the 

1993 regulations but was not defined. Therefore, EPA is adding 

a definition for this term. The definition would require the 

federal agency to have a program to implement the action. That 

program can include a number of steps such as preparation of 

final design plans and can also allow for seasonal shutdowns. 

The definition includes a requirement that the action does not 

stop for more than 18 months unless such a delay is included in 

the original plans for the action.

Direct emissions. The EPA is revising the definition of 

direct emissions to include a requirement that the emissions 

must be reasonably foreseeable. This revision reflects EPA’s 

policy as set forth in the July 1994 implementation guidance 
35

that direct emissions must be reasonably foreseeable. (General 

Conformity Guidance: Questions and Answers, USEPA, OAQPS, Page 

6, Question 2, July 13, 1994).

Emission Inventory. This term is used but not defined in 

the 1993 regulations. Therefore, EPA is adding a definition of 

this term.

EPA. Since some states have Environmental Protection 

Agencies, EPA is adding “U.S.” in the definition to clarify that 

the regulations refer to the U.S. Environmental Protection 

Agency.

Indirect emissions. 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 
36

63.214,63.221, November 30, 1993). (General Conformity Guidance: 

Questions and Answers, USEPA, 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 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 be 

approved.

The commenter believes that the proposed rule definition 

has the potential for allowing massive increases in emissions 

that is anticipated as a result of port expansions in some of 

the nations’ most polluted metropolitan areas. The commenter 

also noted that the NEPA may also create authority to adopt 

environmental mitigation plans as part of an agency’s 

programmatic responsibility.

Response: The exclusion of emissions over which the federal 
37

agency does not have a continuing program responsibility is 

related to indirect emissions for the General Conformity 

analysis and does not affect the analysis required for NEPA 

review. EPA is not changing the requirements of that provision; 

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 revision 

does not change the practical impact of this definition, and 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. In any event, since EPA did not propose to 

expand the program to include emissions over which a federal 

agency does not have control, it cannot go final with such an 

expansion in this rule.

Local air quality modeling analysis. The EPA is revising 

the definition to include an example of the type of models that 

are used in the local air quality modeling analysis.

Maintenance area. The 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.

Metropolitan Planning Organization. The EPA is revising 
38

its regulatory definition to make it more consistent with the 

statutory definition in SAFETEA-LU, which was signed into law on 

August 10, 2005.

Mitigation measure. The 1993 regulations used the term 

“mitigation measure” and had a section specifying the 

requirements for a mitigation measure; however the regulations 

did not define the term. 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.

National ambient air quality standards. In 1997, EPA 

promulgated new NAAQS for both ozone and for fine particles. 

The definition in the 1993 regulations is broad enough to cover 

the new ozone standard, but the definition did not cover the 

fine particle standard known as PM2.5. Therefore, EPA is revising 

the definition of NAAQS to include PM2.5.

Precursors of criteria pollutants. The 1993 regulations 

define precursors for both ozone and PM-10. Since the PM2.5

standard was promulgated after the General Conformity 

Regulations, the original regulations did not include the 

precursors for PM2.5. EPA recently amended the regulations (July 

17, 2006 at 71 FR 40420) to add PM2.5 precursors, consistent with 

the proposed implementation program for the PM2.5 standard (70 FR 

65984). The EPA defined the precursors of PM2.5 as follows:
39

1. Sulfur dioxide (SO2) is a regulated pollutant in all PM2.5

nonattainment and maintenance areas.2

2. Nitrogen oxides (NOX) are regulated pollutants in all 

PM2.5 nonattainment and maintenance areas unless both the 

state/tribe and EPA determine that they are not.

3. Volatile organic compounds (VOC) and ammonia (NH3) are 

not regulated pollutants in any PM2.5 nonattainment or 

maintenance area unless either the state/tribe or EPA determines 

that they are.

Reasonably foreseeable emissions. As discussed above, 

under “direct emissions,” EPA is revising the term “direct 

emissions” to limit the emissions to those which can be 

reasonably foreseeable. Therefore, EPA is revising the term 

“reasonably foreseeable” to include “direct emissions.”

Regionally significant action. As discussed in the 

revisions to 93.153(i) below, EPA is deleting the requirement 

 

2

While sulfur dioxide must be addressed in general conformity 

determinations for PM2.5 , sulfur dioxide is not required to be 

addressed in transportation conformity determinations before a 

SIP is submitted, unless either the state air agency or EPA 

regional office makes a finding that on-road emissions of sulfur 

dioxide are significant contributors to the area's PM2.5 problem. 

Sulfur dioxide would be addressed in transportation conformity 

after a PM2.5 SIP is submitted if the area's SIP contains an 

adequate or approved sulfur dioxide motor vehicle emissions 

budget. EPA based its decision regarding treatment of sulfur 

dioxide in transportation conformity on the de minimis amount of 

on-road emissions of sulfur dioxide now and in the future, and 

on the implementation of low sulfur gasoline beginning in 2004 

and low sulfur diesel fuel beginning in 2006. (70 FR 24283).
40

that conformity determinations are required for actions that 

would normally be exempt if those actions are considered 

regionally significant. Therefore, EPA is deleting the 

definition of the term.

Restricted information. 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 for the definition of “restricted 

information.” 

Response: The EPA agrees that emission data generally can not 

be considered “restricted information.” Under EPA policy 

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 
41

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.

Take or start the federal action. The EPA is adding a new 

term to define the date when an action occurs or starts. This 

date is important in determining what, if any, conformity 

requirements apply when an area is designated or re-designated 

as nonattainment. The EPA is defining this term as the date the 

decision-maker signs a document such as a grant, permit, license 

or approval. Otherwise, EPA is defining the term as the date 

the federal agency physically starts the action that requires 

the conformity evaluation.

Tribal implementation plan (TIP). The EPA is adding a 

definition for TIP to mean plans adopted and submitted by 

federally recognized Indian tribes. 

E. 40 CFR 93.153--Applicability Analysis

The EPA is clarifying the process of determining if the 

General Conformity requirements are applicable to a federal 

action. Although EPA is providing clarification on actions that 

are exempt or “presumed to conform” in this regulation, nothing 

in this regulation is intended to interfere with any exemptions 

previously established by law.

1. The EPA is revising the title of the section to include 
42

the word “analysis.” The EPA believes that adding the word 

would make the title more descriptive of the section's content.

2. The EPA is making technical changes to paragraph (a) of 

§93.153. The technical correction in section 93.153(a) is to 

update the reference to the transportation conformity 

regulations. Section 93.153(a) currently states that the 

transportation conformity regulations are codified at 40 CFR 

part 51 subpart T, but EPA deleted transportation conformity 

criteria and procedures from 40 CFR part 51 subpart T a number 

of years ago. (62 FR 43779) Accordingly, section 93.153(a) has 

been revised to refer to the transportation conformity criteria 

and procedures now codified at 40 CFR part 93 subpart A.3 

EPA is not finalizing the proposed changes to paragraph 

(b). Following proposal of changes to this paragraph EPA 

realized that the minor wording changes we had proposed (adding 

the word “criteria” before the word “pollutant” and “or 

precursor” after the word to clarify the paragraph) had been 

accomplished by changes made to this section in a July 17, 2006 

regulatory action (71 FR 40426). Therefore, EPA is making no 

changes to this paragraph from the current regulatory language.

 

3

While we did not issue a proposal or provide an opportunity for 

public comment for this minor correction to the rule, we believe 

such actions are unnecessary because this minor revision in no 

way changes substantive conformity procedures described in the 

general conformity rule but merely updates the reference to the 

proper location of the transportation conformity regulations in 

the CFR.
43

3. The EPA is revising the table in sub-paragraph (b)(1) 

to include all nonattainment areas in the Ozone Transport 

Regions. In 1993, when the General Conformity Regulations were 

promulgated, all nonattainment areas in the Ozone Transport 

Region were classified pursuant to Table 1 in CAA section 

181(a)(1) as marginal or above for the 1-hour ozone NAAQS. When 

EPA later designated areas for the 8-hour ozone NAAQS, some 

nonattainment areas were identified as needing to meet only the 

requirements in subpart 1 of Part D of Title I of the CAA and 

were not classified pursuant to Table 1. However, the decision 

to place certain areas only under subpart 1 was vacated by the 

decision in South Coast Air Quality Management District v. EPA, 

472 F.3d 882 (DC Cir. 2006). Although there are currently no 

areas classified under subpart 1, the Court left open the door 

that EPA may be able to justify such action in the future. 

Accordingly, EPA is revising the table in §93.153(c)(1) to 

ensure that the General Conformity requirements would apply to

any area placed in the subpart 1 in the future by changing the 

classification from “Marginal and moderate non-attainment areas 

inside an ozone transport region” to “other non-attainment areas 

inside an ozone transport region.”

4. The EPA is adding a new sub-paragraph (xxii) to 

§93.153(c)(2) to clarify the exemptions for aircraft emissions 

above the mixing height for the area. Specifically, EPA is 
44

exempting aircraft emissions above the mixing height identified 

in the applicable SIP, TIP or FIP. Where the SIP does not 

contain a specific mixing height, EPA is establishing a default 

mixing height of 3000 feet AGL. In the January 2008 proposal, 

EPA had proposed to exempt all aircraft emissions above 3000 

feet AGL. 

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. 

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 
45

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 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 is 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, EPA is 

requiring the specified mixing height to be used. 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. In addition, 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 
46

the FAA study showed that some areas have mixing heights lower 

than 3,000 feet AGL, so 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. As a general matter, 

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, including making an applicability 

determination under section 93.153(b), finding emissions result 

in no increase under section 93.153(c)(2), or concluding 

emissions are presumed to conform under section 93.153(f).

5. The EPA is revising paragraph (d)(1) of §93.153 to 

exempt emissions covered by a NSR permit for minor sources. The 

1993 regulations exempt emissions covered by a NSR permit for 

major sources but not for minor sources. EPA concluded at that 

time that the purposes of the General Conformity review would be 

adequately met by the major source NSR review, and that 

additional review would not be necessary. The EPA now believes

that minor source NSR provides similar review, and that this 

approach will reduce the duplicate review of emissions under 

both minor source NSR and conformity programs and treat all NSR 

permitted emissions the same way. Accordingly, we are revising 

§93.153(d)(1) to also exempt emissions covered by minor source 
47

NSR permits issued pursuant to the general permitting authority 

provided by section 110(a)(2)(c) of the CAA.

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 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 suggests 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 emission 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 
48

otherwise interfere with the state’s ability to attain the 

standards. Minor source NSR permits are issued under a SIPapproved 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. 

Thus, by issuing a specific permit under that program, the 

authority is stating 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. 

6. The EPA is deleting “or natural disasters such as 

hurricanes, earthquakes, etc.,” and “or disaster” from paragraph 

(d)(2) of §93.153 because they are unnecessary words. In 

§93.152 EPA defines an emergency; therefore the words in §93.153 

describing an “emergency” are not necessary and may be confusing 

since they do not include all types of emergencies.

7. The EPA is amending paragraph (e)(2) of §93.153 to 

provide procedures for reviewing an extension of the exemption 

from making a conformity determination for actions related to 

responding to an emergency. A federal agency, in responding to 

an emergency event such as a natural disaster, terrorist attack, 

military mobilization, or other situations (such as wildfire 

responses) that an agency determines fit within the definition 
49

of emergency found in §93.152, may find it impractical to 

conduct a conformity evaluation on the action before it must 

take the action. To address this situation, 40 CFR 93.153(d)(2) 

of the 1993 regulations provides federal agencies with a 6-month 

exemption from the requirement to undertake a conformity 

analysis for actions taken in response to an emergency. The EPA 

recognizes that in rare situations it may be impractical, even 

after 6 months, to conduct a conformity evaluation and is 

amending §93.153(e) to allow the agencies to extend the 

exemption for another 6 months. This section requires federal 

agencies to make a written determination that it is impractical 

to conduct an evaluation for the action. The 1993 regulations 

were not clear about the number of additional extensions 

permitted under §93.153(e) nor do those regulations provide any 

procedures for agencies to follow in deciding on the extension.

The EPA is not revising requirements for the initial 

exemption for actions in response to emergencies. The initial 

governmental actions that are typically commenced within hours 

or days in response to emergencies or disasters would still be 

exempt from the General Conformity requirements for six months 

after the commencement of the response to the emergency or 

disaster. However, EPA is adding requirements for federal 

agencies that want to extend the exemption beyond the initial 6-

month period. First, EPA is requiring the federal agencies to 
50

allow EPA and the state 15 days to review and provide comments 

on the draft written determination to extend the exemption at 

the beginning of the extension period. Next, EPA is requiring 

federal agencies to publish a notice within 30 days of making 

the extension decision. The notice must be published in a daily 

general circulation newspaper for the affected area. Finally, 

EPA is limiting the maximum number of 6-month extensions an 

agency may declare without additional documentation on their own 

to three. Thereafter, the revisions require that the agency 

must provide additional information concerning the emergency 

conditions to EPA and the state or tribe

8. The EPA is revising paragraphs (f), (g), and (h) of 

§93.153 to provide federal agencies clear guidance in developing 

their list of actions that are “presumed to conform” and provide 

requirements for the materials that must be included in the 

documentation and draft list. Specifically, EPA is adding 

wording to paragraph (f) to specify when and how more than one 

“presumed to conform” exception may be taken for a federal 

action; adding a new paragraph (g)(3) to specify that federal 

agencies can list actions that are for individual areas or SIPs 

or TIPs; adding a sentence to paragraph (h)(1) to specify the 

information that must be included in the documentation; and 

adding a sentence to paragraph (h)(2) to allow the federal 

agencies to notify EPA headquarters when the “presumed to 
51

conform” actions would have multi-regional or national impacts. 

In addition, EPA is revising paragraphs (f) and (h) to include a 

reference to the new paragraph (g)(3).

In promulgating the existing regulations, EPA allowed a 

number of actions that were “presumed to conform.” The 

regulations also allow federal agencies to establish their own 

lists of actions that are “presumed to conform” with applicable 

SIPs and TIPs. Under the 1993 regulations, federal agencies 

must justify the inclusion of the actions on their “presumed to 

conform” list by either demonstrating: (1) That the actions 

will not cause or contribute to an air quality problem or 

otherwise interfere with the SIP, TIP, or FIP, or (2) that the 

actions will have emissions below the de minimis levels. The 

federal agencies must provide copies of the proposed list to 

EPA, affected state and local air quality agencies and MPOs. In 

addition, the agencies must provide at least a 30-day public 

comment period and document its response to all comments. The 

notice of the proposed and final list must be published in the 

Federal Register.

The EPA is adding sub-paragraph (g)(3) to clarify that a

presumption could apply to one facility or for facilities in a 

specified area and does not have to be nationally applicable. 

For example, if the nonattainment area's SIP includes a sector 

emission budget for construction activities, a facility in that 
52

area may be able to demonstrate that construction activities of 

a certain size or type fits within the SIP's emission budget. 

With the concurrence of the state or tribe, the federal agencies 

could publish a “presumed to conform” list that includes the 

construction activity emissions that are specific to a facility.

9. The EPA is deleting the regionally significant test 

included in paragraph (i) of §93.153. The existing regulations 

in §93.152 define “regionally significant” as “a federal action 

for which the direct and indirect emissions of any pollutant 

represent 10 percent or more of a nonattainment or maintenance 

area's emissions inventory.” 40 CFR 93.153(i) and (j) require 

conformity determinations for all regionally significant 

actions, regardless of any exemptions or presumptions of 

conformity based on other provisions in the regulations. 

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 is an administrative burden. Other commenters believed that 

the provision should be retained or strengthened or a more 

appropriate percentage of the area’s inventory be used for the 

test. Some commenters also pointed out that in light of the new 

PM2.5 and 8-hour ozone standards, certain federal projects might 

become “regionally significant” in the near future. 
53

Response: EPA agrees that the determination of whether actions 

with emissions below the de minimis emission levels are 

regionally significant has been a burden to some federal 

agencies with little or no environmental 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 

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. 

10. In a revised paragraph (i) of §93.153, EPA allows 

installations with a facility-wide emission budget to presume 

that an action at the installation will conform provided that 

the emissions from that action along with all other emissions 

from the facility will not exceed the budget. A more detailed 

discussion of the facility-wide emission budget concept is found 

in §93.161.

11. Also in §93.153(i), EPA identified emissions from a 

prescribed fire conducted under an approved smoke management 

program as “presumed to conform.” In the January 2008 proposal, 

EPA asked for comments on two options for allowing a presumption 
54

of conformity for prescription fires. Option 1 would have 

allowed federal agencies to presume that the emissions from 

prescribed burns will conform provided the burning is conducted 

under a state certified approved SMP or an equivalent 

replacement EPA policy. Option 2 would have also allowed

federal agencies, in the absence of a certified SMP, to presume 

that emissions from prescribed burns will conform provided they

obtain written permission from the state and uses BSMP. 

Comment: The EPA received many comments in support of the 

second option, which allows federal agencies to determine, in 

absence of a certified SMP, that prescription fires conducted 

using BSMP are considered “presumed to conform” to the SIP. 

Some commenters noted that to be consistent with the “Treatment 

of Data Influenced by Exceptional Events” rule (72 FR 13559, 

March 22, 2007), if the state does not certify a SMP, the 

exemption should be for burns using state approved BSMP. Many 

commenters also supported 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. This 

commenter also noted that the use of SMP may be acceptable, but 
55

EPA has not yet issued its final wildland fire policy. Another 

commenter suggested that if prescribed burns under certified SMP 

or a BSMP are “presumed to conform,” there needs to be a simple 

way to flag the data from affected monitors. Numerous 

commenters recommended that the definition of emergency include 

wildfires.

Response: After considering the various practices and the 

comments received, the EPA believes option 1 presented in the 

proposed rule is more protective of the air quality than option 

2. However, we also recognize that prescribed fires employing 

BSMPs may be able 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). Under option 1, prescribed fires 

conducted in compliance with a SMP are “presumed to conform”. 

The purpose of an SMP is to mitigate nuisance smoke and public 

safety hazards, prevent NAAQS violations, protect public health, 

and address visibility impacts in Class I areas. EPA also notes 

that SMPs establish procedures and requirements for minimizing 

emissions. EPA recognizes that prescribed burns employing BSMPs 

may be as protective of air quality in areas where no SMP 

exists. BSMPs can be connected to air quality and may protect 

air quality as outlined in the “Treatment of Data Influenced by 

Exceptional Events” rule. In order to assure the adequacy of the 
56

BSMPs to meet the legal requirements of the General Conformity 

program as outlined in section 176, Federal agency developed 

BSMPs must be publicly and state reviewed as part of a presumed 

to conform action under section 93.153(g) or 51.851(f) of these

regulations to establish such a presumption. . Because the EPA 

chose not to require the certification of the SMP under the 

final “Treatment of Data Influenced by Exceptional Events” rule, 

EPA is also removing the term “certified” from this final 

General Conformity Rule. Finally, EPA has identified wildfire

response as an example of an emergency event that may be exempt 

from General Conformity requirements under 93.153 (d)(2) and (e) 

if that agency determines it fits within the definition of

emergency found in §93.152.

12. As discussed above, EPA also added a provision in 

§93.153(i) to allow a state or tribe to adopt in their SIP or 

TIP a list of actions it “presumes to conform.”

13. The EPA is revising paragraph (j) of §93.153 by 

deleting the reference to regionally significant emissions, by 

adding a reference to paragraph (i) and by describing the 

criteria for requiring a conformity determination for an action 

that otherwise would be “presumed to conform”. The 1993 

regulations state that an action cannot be “presumed to conform”

if it was regionally significant or did not in fact meet the 

requirements of sub-paragraph (g)(1). As discussed above, EPA 
57

has deleted the regionally significant test, therefore reference 

to it is has been deleted from this paragraph. For clarity, 

instead of referring to sub-paragraph (g)(1), EPA is repeating 

the requirements in this paragraph.

14. The EPA is revising paragraph (k) of §93.153 to 

incorporate the provisions of section 176(c)(6) of the CAA. (42 

U.S.C. 7506(c)(6)). In November 2000, Congress added section 

176(c)(6) to the CAA to allow for a conformity grace period for 

newly designated nonattainment areas (Pub. L. 106-377). That 

section establishes a 1-year grace period following the 

effective date of the final nonattainment designation for each 

new or revised NAAQS before the conformity requirements must be 

met in the area. 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. As discussed above 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. From the time that an area is 

designated as nonattainment, agencies will have a year to take 

or start the federal action. If the agency fails to take or 
58

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.

F. 40 CFR 93.154--Federal Agencies Responsibility for a 

Conformity Determination

1. The EPA is revising the title of this section to 

clarify the purpose of the section. In the 1993 regulations 

this section is entitled broadly “Conformity Analysis.” Since 

the short section only discusses the requirement for each 

federal agency to make its own determination, EPA is revising 

the title of the section to more closely describe the section’s 

content.

2. The EPA is adding language to this section to 

specifically state that the conformity determination must meet 

the requirements of this subpart.

G. 40 CFR 93.155--Reporting Requirements

1. Since EPA is adding additional sections to subpart B, 

it is revising the references to those sections in §93.155.

2. Consistent with EPA’s Tribal Authority Rule (63 FR 

7253), EPA is providing federally-recognized Indian tribal 

governments the same opportunity to comment on draft conformity 

determinations as given to states. Therefore, EPA is requiring 

the federal agencies to notify all the federally-recognized 

Indian tribal governments in the nonattainment or maintenance 
59

area. 

3. The EPA is adding an alternative procedure for notifying 

EPA when the action would result in emissions originating in 

nonattainment or maintenance areas in three or more EPA regions. 

Specifically, EPA is allowing agencies to notify the EPA Office 

of Air Quality Planning and Standards rather than each 

individual regional office. A single contact point for EPA 

should be more efficient for the other federal agencies than 

notifying up to 10 regional Offices. This final notification 

provision also corrects an inconsistency between the proposed 

rule preamble and the proposed regulation, which stated that the 

EPA Office of Air Quality Planning and Standards could be 

contacted when the action would result in emissions originating 

in nonattainment or maintenance areas in two or more EPA 

regions. 

4. The EPA is adding a new paragraph to §93.155 to describe 

how restricted information used to support conformity 

determinations should be handled when provided to EPA, states 

and tribal governments. The 1993 General Conformity Regulations 

do not contain an explicit statement about protecting restricted 

information from public release. The interagency review and 

public participation provisions in the 1993 regulations require 

federal agencies to make available for review the draft 

conformity determination with supporting materials that describe 
60

the analytical methods and conclusions relied upon in making the 

determination. Disclosure of classified information by a 

federal employee is a criminal offense (18 U.S.C. 1905). In 

addition, certain unclassified information is privileged or 

otherwise protected from disclosure. Therefore, several federal 

agencies wanted to ensure that the General Conformity 

Regulations clearly state that no agency or individual was 

required to release restricted information including, but not 

limited to, classified materials. Therefore, EPA is revising 

the regulation to add explicit language concerning the 

protection of restricted information. In addition, conformity 

determinations could, in part, be based upon restricted

information. The EPA is adding specific language to the 

regulation to protect restricted information in accordance with 

each federal agency's policy and regulations for the handling of 

restricted information. The regulations would allow state or 

EPA personnel with the appropriate clearances to be able to view 

the restricted information.

H. 40 CFR 93.156--Public Participation

1. The EPA is correcting the section referenced in §93.156. 

The 1993 regulations refer to §93.158. The correct reference 

should be §93.154. Section 93.158 prescribes the criteria for 

conducting a conformity analysis, while §93.154 requires federal 

agencies to make the determination and references the 
61

requirements in the other sections of subpart B.

2. The EPA is providing an alternative public notification 

procedure for actions that cause emissions above the de minimis

levels in three or more EPA Regions. This corrects a mistake 

made in the proposed rule preamble that stated “EPA is proposing 

to provide an alternative public notification procedure for 

actions that cause emissions above the de minimis levels in more 

than three nonattainment or maintenance areas.” In addition, 

this corrects an inconsistency with the proposed regulation, 

which stated that the alternative public notification procedure 

is for actions that have multi-regional or national impacts in 

two or more regions. The 1993 regulations require that the 

federal agency publish a notice in a daily newspaper of general 

circulation in the nonattainment or maintenance area. Some 

federal actions affect a large number of nonattainment and 

maintenance areas. The notification procedure for such an action 

could be burdensome and inefficient. Therefore, EPA is amending 

the rules to allow the federal agencies to publish a notice in 

the Federal Register if the action would cause emissions above 

the de minimis levels in three or more nonattainment or 

maintenance areas.

3. The EPA is adding a new paragraph to §93.156 to describe 

how restricted information and CBI used to support conformity 

determinations should be handled in providing the information to 
62

the public.

I. 40 CFR 93.157--Reevaluation of Conformity

1. The EPA is revising the title of this section to more 

appropriately describe the section's content. The 1993 

regulations section is entitled “Frequency of Conformity 

Determinations.” That title implies that the General Conformity 

requirements for federal actions must be reevaluated on a 

regular basis. However, the section states that conformity must 

be reevaluated only if the determination lapses or the action is 

modified, resulting in an increase in emissions.

2. If an action's emissions are below the de minimis levels 

or the action is not located in a nonattainment or maintenance 

area, a conformity determination is not required. Therefore, 

the federal agency would not have a date for the conformity 

determination to use in determining if reevaluation is required. 

The EPA is making minor wording changes in paragraphs (a) and 

(b) to clarify that the date of a completed NEPA analysis, as 

evidenced by a signed finding of no significant impact (FONSI) 

for an environmental assessment, a record of decision (ROD) for 

an environmental impact statement, or a record of a categorical 

exclusion, can be used when a conformity determination is not 

required.

3. The EPA is adding a new paragraph (d) to §93.157 to 

clarify the requirements for needing to conduct a conformity 
63

determination when the action is modified. Paragraph (d) deals 

with modifying an action for which the federal agency made a 

conformity determination. In order to make the original 

determination, the federal agency had to demonstrate that all 

the emissions caused by the initial action conformed to the SIP. 

Since conformity determinations are only needed for emissions 

that exceed the de minimis levels, EPA has clarified in the rule 

that the federal agency does not have to revise its conformity 

determination unless the modification would result in an 

increase that equals or exceeded the de minimis emission levels 

for the area. Paragraph (d) also deals with modifying an action 

that the federal agency determined had emissions below the de 

minimis level. Since the emissions from the unmodified action 

were determined to be de minimis and not fully evaluated to 

determine conformity, EPA is requiring federal agencies to 

conduct a conformity determination for the modified action if 

the total emissions (the emissions from the unmodified action 

plus the increased emissions resulting from the modification) 

equal or exceed the de minimis levels for the area. Thus, in 

both situations, all emissions that exceed de minimis levels are 

evaluated for conformity impacts, either initially or after 

modification

J. 40 CFR 93.158--Criteria for Determining Conformity for 

General Federal Actions
64

1. In §93.158(a)(1), EPA is adding “or precursor” after 

“any criteria pollutant” to clarify that federal agencies must

demonstrate conformity for the precursors of the criteria 

pollutants if the precursor emissions are specifically 

identified and accounted for in the applicable SIP, TIP or FIP.

2. In §93.158(a)(2) and (a)(5)(iii), EPA is allowing 

federal agencies to obtain emission offsets for the General 

Conformity requirements from a nearby nonattainment or 

maintenance area of equal or higher classification, provided 

that the emissions from 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. 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 the allowing of offsets from other areas. The 
65

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.

Response: The EPA agrees that offsets should be allowed in 

nearby nonattainment areas in the same manner as they are 

allowed under the NSR program. We 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 also recommending that federal agencies show 

that they have met the requirements of §93.158(a)(2) -- that the 

emission offsets originate are 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 has approved by rule or guidance for 

demonstrating contributing emissions in other SIP-related 

determinations, such as Reasonable Further Progress, Rate of 
66

Progress, or Attainment Demonstrations 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 result 

in a benefit to the nonattainment or maintenance area in which 

the federal action will take place. 

3. In §93.158(a)(2), (a)(3) and (a)(4), EPA is revising 

the regulations to address the precursors of PM2.5. The EPA does 

not believe that the current models are adequate to reasonably 

predict the project level impact of individual precursor sources 

of ozone or PM2.5. Therefore, EPA is allowing federal agencies 

to use modeling to demonstrate conformity only for directly 

emitted pollutants. Precursors of PM2.5 will be treated the same 

as precursors of ozone and direct emissions of PM2.5 will be 

treated the same as CO and PM-10 for purposes of identifying 

available tests to demonstrate conformity. 

4. In §93.158(a)(3) and (5), EPA is correcting two 

typographical errors. In sub-paragraph (3), EPA is correcting 

“meet” to “meets” and in sub-paragraph (5), EPA is changing 

“paragraph (a)(3(11)” to “paragraph (a)(3)(ii).”

5. In §93.158(a)(5)(iv)(A)(1), EPA is deleting the 

reference to the year 1990 and replacing it with a generic 

reference to the most current calendar year with a complete 

emission inventory available before an area is designated unless 
67

EPA sets another year. In addition to requiring the conformity 

regulations, the CAA Amendments of 1990 required the designation 

of areas as nonattainment based on the existing air quality 

data. Therefore, when EPA promulgated the 1993 regulations, all 

the designations were based on a 1990 date. Since EPA 

promulgated the conformity regulations, it has promulgated new 

8-hour ozone and PM2.5 standards and designated a number of areas 

as nonattainment. By changing the regulations to reference the

date when the area was designated as nonattainment, EPA is 

allowing for the General Conformity regulations to address these

new designations and any future designations through 

identification of appropriate inventory levels. In addition,

including the option to allow EPA to set another year for the 

baseline allows EPA and other federal agencies to work together 

to determine if another baseline may be appropriate for 

determining conformity of a particular action, such as 

determining that an agency can rely on one specific baseline 

year for an action subject to both the general and

transportation conformity regulations when those regulations 

otherwise indicate application of two different baseline years.

6. Also in §93.158(a)(5)(i), EPA is revising the paragraph 

to allow federal agencies to make conformity determinations

based upon a state's or tribe's determination that the emissions 

from the action along with all other emissions in the area would 
68

not exceed the emission budget in the applicable SIP or TIP. 

Under the 1993 regulations, states could only make such a 

determination if they had an approved attainment demonstration 

or maintenance SIP. This revision would allow the state or 

tribe to make its determination based upon a post-designation 

applicable SIP or TIP even though the plan does not include an 

attainment demonstration. For example, the state or tribe could 

base their determination on an emission budget in an EPA 

approved “Reasonable Further Progress” plan. By adopting the 

budget and submitting it as part of the SIP or TIP, the state or 

tribe is treating the federal action like any other source in 

the area. When the state or tribal agency adopts the attainment 

or maintenance SIP or TIP, it will have to consider the 

emissions from the federal action, and if necessary require 

additional controls on the sources as necessary to meet air 

quality needs.

7. The EPA is revising §93.158(a)(5)(i)(C) to allow the 

state or tribe to commit to including the emissions from the 

federal action in future SIPs. Under the 1993 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 
69

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. For example, a SIP for a 

nonattainment area that demonstrates attainment may only cover 

the period until the attainment date while the conformity 

determination may cover emissions for many years beyond that 

date. The state or tribe may be submitting future SIPs or TIPs 

to address either maintenance of the standard or to address a 

continuing nonattainment problem that would cover the time 

period of the emissions. The revision to §93.158(a)(5)(i)(C) 

would continue to require states to revise the SIP within 18 

months of the conformity determination based upon a state's or 

tribe's commitment. However, if the existing SIP or TIP (or a 

SIP or TIP due within 18 months) does not cover the time period 

of the emissions, then the state or tribe will submit a SIP 

revision that includes an enforceable commitment to account for 

the emissions in future SIP revisions. This approach will allow 

states and tribes flexibility in committing to include the 

emissions from the federal action in the SIP covering the 

relevant time period.

8. The EPA is revising §93.158(a)(5)(iv) to delete the use 

of 1990 as the baseline year. As discussed above, when EPA 

promulgated the existing General Conformity Regulations in 1993, 
70

the designations and classifications were based upon the 1990 

air quality and emissions. Since 1993, EPA has promulgated new 

standards and designated additional areas as nonattainment. 

Therefore, in many cases the 1990 date for the baseline emission 

inventory is inappropriate. The EPA is setting the baseline 

year as the most current calendar year with a complete emission 

inventory available before an area is designated unless EPA sets 

another year. As noted above, including the option to allow EPA 

to set another year for the baseline allows EPA and other 

federal agencies to work together to determine if another 

baseline may be appropriate for determining conformity of a 

particular action.

Finally, EPA is deleting another alternate baseline year 

that no longer is applicable in PM-10 areas. Specifically, EPA 

is deleting in §93.158(a)(5)(iv)(A)(3) the use of the “year of 

the baseline inventory in the PM-10 applicable SIP.” EPA 

believes that the deletion of this out-dated baseline year 

should not affect current General Conformity determinations in 

PM-10 nonattainment and maintenance areas.

K. 40 CFR 93.159--Procedures for Conformity Determinations for 

General Federal Actions

1. EPA is changing §93.159(b)(1)(ii) to address when new 

motor vehicle emissions factors models are used in General 

Conformity determinations. EPA is clarifying that the grace 
71

period before such new models are used will be 3 months from 

EPA's model release, unless a longer grace period is announced 

in the Federal Register. This is more consistent with 40 CFR 

93.111 of the transportation conformity rule that allows grace 

periods for new motor vehicle emissions factor models to be 

between 3-24 months.

2. The EPA is revising §93.159(b)(2) and (c) to update the 

reference to the Compilation of Air Pollutant Emission Factors 

and the Guideline on Air Quality Modeling. EPA has released 

updated versions of these documents since it promulgated the 

existing regulations in 1993.

3. The EPA is revising paragraph (d)(1) to clarify that 

analysis is first required for the attainment year specified in 

the SIP. In some cases, such as SIPs for marginal ozone areas, 

an attainment demonstration date was not required in the SIP. 

Therefore, EPA is requiring that if the SIP or TIP does not 

specify an attainment demonstration year then the analysis is 

conducted for the latest attainment year possible under the CAA. 

Since the CAA requires the SIP demonstrate attainment as 

expeditiously as possible but no later than the CAA mandated 

attainment date, it is possible that a SIP or TIP could have an 

earlier attainment date. That earlier date if specified in the 

SIP would be the appropriate year for the conformity analysis.

4. The EPA is making a minor wording revision to paragraph 
72

(d)(2) to clarify the paragraph. The EPA is replacing the word 

“farthest” with “last.” The maintenance plans are developed for 

a 10-year period and revised as necessary for the next 10-year 

period. The purpose is for conformity to be evaluated for the 

last year of the maintenance plan. The word “last” conveys that 

meaning.

L. 40 CFR 93.160--Mitigation of Air Quality Impacts

The EPA is revising paragraph §93.160(f) to clarify its 

meaning. The regulations were meant to require that the 

mitigation measures include a written commitment from the person 

or organization reducing the emissions and that those 

commitments must be fulfilled. EPA is adding text to state that 

those commitments must be fulfilled to clearly provide for 

enforcement of those commitments under the federal regulations.

M. 40 CFR 93.161--Conformity Evaluations for Installations With 

Facility-Wide Emission Budget

The EPA is adding a new section to the regulations to 

facilitate the use of a facility-wide emission budget in 

evaluating conformity. Although the existing regulations do not 

preclude states and federal agencies from using this approach, 

the regulations do not specifically authorize its use. This 

section for developing such a budget would be in conjunction 

with a new §93.153(i)(1), which provides a mechanism for 

demonstrating that the emissions are in conformance with the SIP 
73

or TIP. This approach allows states or tribes and federal 

agencies to identify acceptable levels of emissions from the 

facility for inclusion in the SIP before starting the 

environmental review for the actions and thereby expedite the 

review of the federal actions at the facilities that do not 

exceed the emission levels.

The EPA believes that this provision would encourage the 

state, tribe or local air quality agency and the federal 

facilities to develop an upfront emission budget for the 

facility, and the action or project environmental review would 

be streamlined as long as the facility remains within an 

established budget.

The development and use of a facility-wide emission budget 

would be voluntary on the part of the federal agency, state, 

tribe and local air quality agency. No party would be required 

to participate. If the parties agreed to participate, an 

emission budget would be established based upon specific 

guidance and documented growth projections for the facility, and 

adoption of that budget into a SIP or TIP would demonstrate that 

the area could meet its air quality obligations with the 

identified emission budget.

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 
74

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 their own budget without having to do additional 

analysis. 

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 the 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, anti-backsliding, 

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).

Response: The EPA agrees with most of the commenters that the 

facility-wide emissions budget approach will not interfere with 

attainment of the NAAQS and will provide flexibility to the 

facilities in meeting the General Conformity requirements. EPA 

believes that this approach benefits both the air regulatory 

agencies and the regulated facilities. State air quality 
75

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 reasonable 

further progress milestones. Thus, in developing and approving 

such budgets, we encourage the facilities and the state or tribe 

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 facility-wide emission budget. Federal agencies may 

use any approach to demonstrate conformity provided for in the 

rule. Facilities that are not federally controlled or operated, 
76

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 obligation to meet any 

SIP or CAA requirements, milestones or deadlines.

N. 40 CFR 93.162--Emissions Beyond the Time Period Covered by 

the Applicable SIP or TIP

The EPA is adding a new section to address how federal 

agencies can demonstrate conformity for an action that causes 

emissions beyond the time period covered by the SIP or TIP. 

First, EPA is allowing federal agencies to demonstrate 

conformity using the last emission budget in the SIP or TIP. If 

it is not practicable to demonstrate conformity using that 

technique, then the federal agency can request the state or 

tribe to provide an enforceable commitment to include the 

emissions from the federal action in a current or future SIP or 

TIP emissions budget. In such a case, the state or tribe would 

be required to submit a SIP revision within 18 months to either

include the emissions in the current SIP or TIP or a commitment

to account for the emissions in future SIPs or TIPs. The 

emissions included in the future SIP should be based on the 

latest planning assumptions at the time of the SIP revision.
77

Although a state is committing to include the emissions in the 

emissions budget for the SIP revisions, this commitment does not 

prevent the state from requiring the use for the effected 

sources of reasonably available control technology (RACT), 

reasonably available control measures (RACM) or any other 

control measures within the state's authority to ensure timely 

attainment of the NAAQS.

O. 40 CFR 93.163--Timing of Offsets and Mitigation Measures

Mitigation measures and offsets are used to reduce the 

impact of emission increases from a project or action. To 

alleviate the impact of the project's emissions, the emissions 

reductions from offsets or mitigation measures should occur at 

the same time as the emission increases from the project. In 

general, EPA has interpreted the existing regulations to mean 

that the reductions must occur in the same calendar year as the 

emission increases caused by the action because the total direct 

and indirect emissions from an action are collated on an annual 

basis. Therefore, EPA has decided to include this interpretation 

in the regulations.

The EPA is adding a new section to address the timing of 

offset and mitigation measures. First, the section generally 

requires that the emission reductions for the offset and 

mitigation measures must occur in the same calendar year as the 

emission increases caused by the federal action and that the 
78

reductions are 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 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. Therefore, 

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 
79

requiring that the period should not exceed two times the period 

of the under-mitigated 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 reasonable

further progress 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 entity would do 

so. One commenter recommended that the state or tribal agency 
80

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 time limit for 

the schedule and requiring more than a one-for-one offset.

Response: The EPA believes the rule should be finalized as 

proposed. This will allow federal agencies to work with states 

or tribes to develop an alternative schedule for the emission 

reductions in cases where a greater environmental benefit can be 

obtained. The requirement for the additional reductions to meet 

the ratios in the regulations ensures that the area is receiving 

at least a minimum environmental benefit consistent with other 

CAA programs. Since state or tribal approval is required for 

the alternative schedule, those agencies have the ability to 
81

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 clarify that the state or tribe is not 

compelled to approve a proposed alternate schedule for 

mitigation measures. 

P. 40 CFR 93.164--Inter-Precursor Offsets and Mitigation 

Measures

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. For example, some states and local 

air districts have SIP-approved NSR regulations that allow new 

or modified stationary sources to offset the increase in 

emissions of one criteria pollutant precursor by reducing the 

emissions of another precursor of the same criteria pollutant, 

provided there is an environmental benefit to such an exchange

and an appropriate ratio of precursor reductions has been 

established. The 1993 General Conformity regulations do not 

specifically allow or prohibit inter-precursor 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 tribal NSR or trading program approved in the SIP,

provided they:

1. Are technically justified; and

2. Have a demonstrated environmental benefit.
82

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 inter-pollutant mitigation. 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 program, transportation conformity program, or in the 

attainment or reasonable further progress (RFP) demonstration to 
83

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 that 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.

Q. 40 CFR 93.165--Early Emission Reduction Credit Program

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, 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. To expedite the project 

level conformity process, EPA believes federal agencies and 

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. 

The EPA is adding a new section, §93.165, to the General 
84

Conformity Regulations to define the requirements of this 

program. Under the program, federal agencies or project 

proponents (such as airport authorities) could identify emission 

control measures and present the proposed reduction to the 

state, tribe or local air quality agency. If the measure met 

the criteria for an offset (quantifiable; consistent with the 

applicable SIP attainment and RFP demonstrations; surplus to the 

reductions required by and credited to other applicable SIP 

provisions; enforceable at both the state and federal levels; 

and permanent within the timeframe specified by the program) as 

well as all state, tribe or local requirements, the state, tribe 

or local agency can approve the measure as eligible to produce 

emission reduction credits. If credits are issued, then a 

federal agency will be allowed to use the credits to reduce the 

total of direct and indirect emissions from a future proposed 

action. At the time the credits are used, the state, tribe or 

local agency must certify that the reductions still meet the 

criteria listed above. The credits must be used in the same 

calendar year in which they are generated under this program.

In paragraph (a), EPA establishes the ability for the state 

or tribe and federal agency to create and use the emission 

reduction credits.

In paragraph (b), EPA identifies the criteria for creating 

the credits. The criteria are similar to the requirements that 
85

apply to any offset or mitigation measure used to compensate for 

the increased emissions caused by the action. First, the 

federal agency must be able to quantify the reductions using 

reliable techniques. In some cases, however, it may not be 

possible to precisely quantify the reductions until after the 

measure has been implemented. For example, a facility may adopt 

a strategy calling for the purchase and use of alternate-fueled 

vehicles. Although the agency could calculate the difference in 

the emissions between the alternate-fueled vehicle and the 

standard vehicle, it may not know the amount the vehicles will 

be used. In this case, the state or tribe and federal agency 

could agree on an emission factor and determine the use at a 

later time. However, the reductions must be quantified before 

the credit is used to support a conformity determination.

In paragraph (c), EPA establishes the requirements for the 

use of the credits. If the emission reduction credits are 

created at the same facility and in the same nonattainment or

maintenance area as the federal action, the credits can be used 

to reduce the total emissions from the action. This may allow 

the federal agency to determine the action conforms because the 

total emissions are below the de minimis levels for the area.

If the strategy is not implemented at the same facility but is 

in the same nonattainment or maintenance areas as the action, 

then the credits can be used as offsets or mitigation measures 
86

for the emissions caused by the action, but not to determine if 

the action emissions fall below de minimis thresholds. In this 

context, “same facility” means a contiguous area that a federal 

agency manages or exercises control over. Generally, all 

actions and operations within a fence line of a facility such as 

an airport would be considered to be at the “same facility.” 

However, military operations at a civilian airport would not be 

considered to be at the “same facility.” Therefore, an airport 

could install equipment to supply power and conditioned air to 

airplanes parked at a gate to reduce the use of diesel 

generators and auxiliary power units at an airport terminal. 

Those reductions could be considered to be implemented as part 

of an airport expansion project to improve the terminal and thus 

would be at the “same facility.”

Since the General Conformity program is based on annual 

emissions, EPA is requiring that the credits be used in the same 

year as they are generated under the program. Such a restriction 

would ensure consistency with the other parts of the General 

Conformity program. This does not mean that an emission 

reduction strategy cannot produce an annual stream of credits, 

but does mean that the reduction credits cannot be carried over 

to another year. Although the emission reduction credits must 

meet the criteria for use of offsets or other mitigation 

measures, EPA is not allowing the credits to be combined with 
87

other program areas such as the alternate schedules for 

mitigation measures under §93.163 or the inter-precursor 

mitigation offset program under §93.164. At this time, EPA 

believes that, because of the newness of the emission reduction 

credit program and the lack of available implementation data, it 

is better to take a conservative approach on implementing the 

program to ensure that it can be effectively implemented and 

evaluated.

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 ERCs can be used. Several 

commenters disagreed with the proposal, citing concerns such as

violations of conformity, while another was concerned about the 

additional resources required to certify the ERC and track them 

over time, and avoidance of formal conformity determinations. 

Still another commenter thought that under §93.165(b)(4) there is 

no ability for states and the public to enforce the measures 

relied upon to generate emission reduction credits.

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 
88

conjunction with the action requiring the conformity 

determination. Therefore, the use of ERC would not encourage an 

agency to violate conformity. In any event, 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 when 

they are used in a conformity evaluation, while the agency 

relying upon the credits is required to document that usage.

VII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

Under Executive Order (EO) 12866 (58 FR 51735, October 4, 

1993), this action is a “significant regulatory action” because 

it may interfere with actions taken or planned by other federal 

agencies. Accordingly, EPA submitted this action to the Office 

of Management and Budget (OMB) for review under EO 12866 and any 

changes made in response to OMB recommendations have been 

documented in the docket for this action.

B. Paperwork Reduction Act

This action does not directly impose an information 

collection burden under the provisions of the Paperwork 

Reduction Act, 44 U.S.C. 3501 et seq., on non-federal entities. 

The General Conformity Regulations require federal agencies to 

determine that their actions conform to the SIPs or TIPs. 
89

However, depending upon how federal agencies implement the 

regulations, non-federal entities seeking funding or approval 

from those federal agencies may be required to submit 

information to that agency.

Although the present revisions to the regulations do not 

establish any specific new information collection burden, it 

would establish alternative voluntary approaches that may result 

in a different burden. For example, the proposed facility-wide 

emission budget would allow federal agencies or operators of 

facilities subject to the General Conformity requirements such 

as commercial service airports to work with the state, tribe or 

local air quality agency to develop an emission budget for the 

facility. The state, tribe or local agencies and federal 

agencies or third party facility operators would incur the 

burden of developing the budget. However, those entities are 

not required to implement such a program and would be relieved 

of the burden of conducting and reviewing some, if not all, of 

the General Conformity determinations for the facility if they 

do so. States are not required to implement a program that 

would increase their burden, and we assume they would not choose 

to do so.

C. Regulatory Flexibility Act

The Regulatory Flexibility Act (RFA) generally requires an 

Agency to prepare a regulatory flexibility analysis of any 
90

regulation subject to notice and comment rulemaking requirements 

under the Administrative Procedures Act or any other statute 

unless the Agency certifies the rule will not have a significant 

economic impact on a substantial number of small entities. 

Small entities include small businesses, small organizations, 

and small governmental jurisdictions.

For purposes of assessing the impacts of these regulation 

revisions on small entities, small entity is defined as: (1) A 

small business that is a small industrial entity as defined in 

the U.S. Small Business Administration (SBA) size standards. 

(See 13 CFR 121.); (2) A governmental jurisdiction that is a 

government of a city, county, town, school district or special 

district with a population of less than 50,000; and (3) A small 

organization that is any not-for-profit enterprise which is 

independently owned and operated and is not dominant in its 

field.

After considering the economic impact of these revisions to 

the regulations on small entities, I certify that this action 

will not have a significant economic impact on a substantial 

number of small entities. These revisions will not impose any 

significant requirements on small entities, because the General 

Conformity Regulations set requirements on federal agencies to 

show that their actions conform to the appropriate state, tribal 

or federal implementation plan for attaining clean air. 
91

D. Unfunded Mandates Reform Act

This action contains no federal mandates under the 

provisions of Title II of the Unfunded Mandates Reform Act of 

1995 (UMRA), 2 U.S.C. 1531-1538 for state, local, or tribal 

governments or the private sector. Therefore, this action is not 

subject to the requirements of section 202 and 205 of the UMRA.

This action is also not subject to the requirements of 

section 203 of UMRA because it contains no regulatory 

requirements that might significantly or uniquely affect small 

governments. Nonetheless, EPA carried out consultations with 

governmental entities affected by this regulation.

E. Executive Order 13132--Federalism

Executive Order 13132, entitled “Federalism” (64 FR 43255, 

August 10, 1999), requires EPA to develop an accountable process 

to ensure “meaningful and timely input by state and local 

officials in the development of regulatory policies that have 

Federalism implications.” “Policies that have Federalism 

implications are defined in the Executive Order to include 

regulations that have substantial direct effects on the states, 

on the relationship between the national government and the 

states, or on the distribution of power and responsibilities 

among the various levels of government.”

This final rule does not have federalism implications. It 

will not have substantial direct effects on the states, on the 
92

relationship between the national government and the states, or 

on the distribution of power and responsibilities among the 

various levels of government, as specified in Executive Order 

13132. Previously, EPA determined the costs to states to 

implement the General Conformity Regulations to be less than 

$100,000 per year. Thus, Executive Order 13132 does not apply 

to these regulation revisions.

In the spirit of Executive Order 13121 and consistent with 

EPA policy to promote communications between EPA and state and 

local governments, EPA held meetings with the federal agencies 

and organizations that prepare technical support for federal 

agencies determinations. EPA described the approaches it was 

considering and provided an opportunity for states, federal 

agencies and other stakeholders to comment on the options being 

considered.

F. Executive Order 13175--Consultation and Coordination With 

Indian Tribal Governments

This action does not have tribal implications, as specified 

in Executive Order 13175 (65 FR 67249, November 9, 2000). They 

do not have a substantial direct effect on one or more Indian 

tribes, since no tribe has to demonstrate conformity for their 

actions. Furthermore, except for allowing the tribes to comment 

on draft conformity determinations, these regulation revisions 

do not affect the relationship or distribution of power and 
93

responsibilities between the federal government and Indian 

tribes. The CAA and the Tribal Air Rule establish the 

relationship of the federal government and tribes in developing 

plans to attain the NAAQS, and these revisions to the 

regulations do nothing to modify that relationship. Because 

these regulation revisions do not have tribal implications, 

Executive Order 13175 does not apply.

Although Executive Order 13175 does not apply to these 

regulations, EPA did consult with some tribal officials in 

developing these regulations revisions and encouraged tribal 

input at an early stage. The EPA specifically solicited

additional comment on the proposed revisions to the regulations 

from tribal officials.

G. Executive Order 13045: Protection of Children from

Environmental Health and Safety Risks

EPA interprets EO 13045 (62 FR 19885, April 23, 1997) 

as applying only to those regulatory actions that concern 

health or safety risks, such that the analysis required 

under section 5-501 of the EO has the potential to 

influence the regulation. This action is not subject to EO 

13045 because it does not establish an environmental 

standard intended to mitigate health or safety risks.

H. Executive Order 13211: Actions That Significantly Affect 

Energy Supply, Distribution, or Use
94

This action is not a “significant energy action” as defined 

in Executive Order 13211 (66 FR 28355, May 22, 2001), because it 

is not likely to have a significant adverse effect on the 

supply, distribution, or use of energy. Further, we have 

concluded that this rule is not likely to have any adverse 

energy effects.

I. National Technology Transfer Advancement Act

Section 12(d) of the National Technology Transfer 

Advancement Act of 1995 (NTTAA), Public Law 104-113, section 

12(d) (15 U.S.C. 272 note) directs EPA to use voluntary 

consensus standards (VCS) in its regulatory activities unless to 

do so would be inconsistent with applicable law or otherwise 

impractical. The VCS are technical standards (e.g., materials 

specifications, test methods, sampling procedures, and business 

practices) that are developed or adopted by VCS bodies. The 

NTTAA directs EPA to provide Congress, through OMB, explanations 

when the Agency decides not to use available and applicable VCS.

This action does not involve technical standards. 

Therefore, EPA did not consider the use of any VCS.

J. Executive Order 12898: Federal Actions To Address 

Environmental Justice in Minority Populations and Low-Income 

Populations

Executive Order (EO) 12898 (59 FR 7629, (Feb. 16, 1994)) 

establishes federal executive policy on environmental justice. 
95

Its main provision directs federal agencies, to the greatest 

extent practicable and permitted by law, to make environmental 

justice part of their mission by identifying and addressing, as 

appropriate, disproportionately high and adverse human health or 

environmental effects of their programs, policies, and 

activities on minority populations and low-income populations in 

the United States.

The EPA has determined that this final rule will not have 

disproportionately high and adverse human health or 

environmental effects on minority or low-income populations 

because it does not affect the level of protection provided to 

human health or the environment. The revisions to the 

regulations would revise procedures for other federal agencies 

to follow and does not relax the progress toward attainment and 

maintenance for the NAAQS as required by individual SIPs and 

TIPs As such, they do not affect the health or safety of 

minority or low income populations. The EPA encourages other 

agencies to carefully consider and address environmental justice 

in their implementation of their evaluations and conformity 

determinations.

K. Congressional Review Act

The Congressional Review Act, 5 U.S.C. 801 et seq., as 

added by the Small Business Regulatory Enforcement Fairness Act 

of 1996, generally provides that before a rule may take effect, 
96

the agency promulgating the rule must submit a rule report, 

which includes a copy of the rule, to each House of the Congress 

and to the Comptroller General of the United States. EPA will 

submit a report containing this rule and other required 

information to the U.S. Senate, the U.S. House of 

Representatives, and the Comptroller General of the United 

States prior to publication of the rule in the Federal Register. 

A major rule cannot take effect until 60 days after it is 

published in the Federal Register. This action is not a “major 

rule” as defined by 5 U.S.C. 804(2). This rule will be 

effective [INSERT DATE 90 DAYS AFTER DATE OF PUBLICATION IN 

FEDERAL REGISTER].

VII. Statutory Authority

The statutory authority for this action is provided by 

section 176(c) of the CAA as amended (42 U.S.C. 7506). 

List of Subjects

40 CFR Part 51

Environmental protection, Administrative practice and 

procedures, Air pollution control, Carbon monoxide, 

Intergovernmental relations, Lead, Nitrogen dioxide, Ozone, 

Particulate matter, Reporting and recordkeeping requirements, 

Sulfur dioxide, Volatile organic compounds.
97

Page 95 of 133 - Revisions to the General Conformity Regulations

40 CFR Part 93

Environmental protection, Administrative practice and 

procedures, Air pollution control, Carbon monoxide, 

Intergovernmental relations, Lead, Nitrogen dioxide, Ozone, 

Particulate matter, Reporting and recordkeeping requirements, 

Sulfur dioxide, Volatile organic compounds.

_______________________________

Dated:

_______________________________

Lisa P. Jackson,

Administrator.
98

 For the reasons stated in the preamble, title 40, chapter I 

of the Code of Federal Regulations is amended as follows:

PART 51--REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL 

OF IMPLEMENTATION PLANS

1. The authority citation for part 51 continues to read as 

follows:

Authority: 23 U.S.C. 101; 42 U.S.C. 7401-7671q.

Subpart W--[Amended]

2. Remove and reserve §51.850 and §§51.852 through 51.860.

3. Section 51.851 is revised to read as follows:

§51.851 State implementation plan (SIP) or Tribal implementation 

plan (TIP) revision.

(a) A state or eligible tribe (a federally recognized tribal

government determined to be eligible to submit a TIP under 40 

CFR 49.6) may submit to the Environmental Protection Agency 

(EPA) a revision to its applicable implementation plan which 

contains criteria and procedures for assessing the conformity of 

federal actions to the applicable implementation plan, 

consistent with this section and 40 CFR part 93, subpart B.

(b) Until EPA approves the conformity implementation plan 

revision permitted by this section, federal agencies shall use 

the provisions of 40 CFR part 93, subpart B in addition to any 

existing applicable state or tribal requirements, to demonstrate 

conformity with the applicable SIP or TIP as required by section 
99

176(c) of the CAA (42 U.S.C. 7506).

(c) Following EPA approval of the state or tribal conformity 

provisions (or a portion thereof) in a revision to the 

applicable SIP or TIP, conformity determinations shall be 

governed by the approved (or approved portion of) state or 

tribal criteria and procedures. The federal conformity 

regulations contained in 40 CFR part 93, subpart B would apply 

only for the portion, if any, of the part 93 requirements not 

contained in the state or tribe conformity provisions approved 

by EPA.

(d) The state or tribal conformity implementation plan criteria 

and procedures cannot be any less stringent than the 

requirements in 40 CFR part 93, subpart B.

(e) A state's or tribe's conformity provisions may contain 

criteria and procedures more stringent than the requirements 

described in this subpart and part 93, subpart B, only if the 

state's or tribe's conformity provisions apply equally to nonfederal as well as federal entities.

(f) In its SIP or TIP, the state or tribe may identify a list of 

federal actions or type of emissions that it presumes will 

conform. The state or tribe may place whatever limitations on 

that list that it deems necessary. The state or tribe must 

demonstrate that the action will not interfere with timely 

attainment or maintenance of the standard, meeting the 
100

reasonable further progress milestones or other requirements of 

the Clean Air Act. Federal agencies can rely on the list to 

determine that their emissions conform with the applicable SIP 

or TIP.

(g) Any previously applicable SIP or TIP requirements relating 

to conformity remain enforceable until EPA approves the revision 

to the SIP or TIP to specifically remove them.

PART 93--DETERMINING CONFORMITY OF FEDERAL ACTIONS TO STATE 

TRIBAL OR FEDERAL IMPLEMENTATION PLANS

4. The authority citation for part 93 continues to read as 

follows: Authority: 42 U.S.C. 7401-7671q.

Subpart B--[Amended]

5. Section 93.150 is amended by removing and reserving paragraph 

(c) and by adding paragraph (e) to read as follows:

§93.150 Prohibition.

* * * * *

(e) If an action would result in emissions originating in more 

than one nonattainment or maintenance area, the conformity must 

be evaluated for each area separately.

6. Section 93.151 is revised to read as follows:

§93.151 State implementation plan (SIP) revision.

The provisions and requirements of this subpart to demonstrate 

conformity required under section 176(c) of the Clean Air Act 

(CAA) apply to all federal actions in designated nonattainment 
101

and maintenance areas where EPA has not approved the General 

Conformity SIP revision allowed under 40 CFR 51.851. When EPA 

approves a state's or tribe’s conformity provisions (or a

portion thereof) in a revision to an applicable implementation 

plan, a conformity evaluation is governed by the approved (or 

approved portion of the) state or tribe’s criteria and 

procedures. The federal conformity regulations contained in this 

subpart apply only for the portions, if any, of the part 93 

requirements not contained in the state or tribe conformity 

provisions approved by EPA. In addition, any previously 

applicable implementation plan conformity requirements remain 

enforceable until the EPA approves the revision to the 

applicable SIP to specifically include the revised requirements 

or remove requirements.

7. Section 93.152 is amended as follows:

a. Adding in alphabetical order a definition for “Applicability 

analysis.” 

b. Revising the definition of “Applicable implementation plan or 

applicable SIP.”

c. Revising the definition for “Areawide air quality modeling 

analysis.”

d. Adding the following definitions in alphabetical order: 

“Confidential business information,” “Conformity determination,” 

“Conformity evaluation,” “Continuing program responsibility,” 
102

and “Continuous program to implement.”

e. Revising the definition of “Direct emissions.”

f. Adding in alphabetical order a definition for “Emission 

inventory.”

g. Removing the definition for “Emissions that a federal agency 

has a continuing program responsibility for.”

h. Revising the definition of “EPA.”

i. Revising the definition of “Indirect Emissions.”

j. Revising the definition of “Local air quality modeling 

analysis.”

k. Revising the definitions for “Maintenance area” and 

“Metropolitan Planning Organization (MPO).”

l. Adding in alphabetical order a definition for “Mitigation 

measure.”

m. Revising the definition for “National ambient air quality 

standards (NAAQS).”

n. In the definitions for Precursors of a criteria pollutant” 

revising paragraphs (3)(i), (3)(ii) and (3)(iii).

o. Revising the definition for “Reasonably foreseeable 

emissions.”

p. Removing the definition for “Regionally significant action.”

q. Adding the following definitions: “Restricted information.”

r. Adding in alphabetical order the definitions for “Take or 

start the federal action” and “Tribal implementation plan 
103

(TIP).”

The additions and revisions read as follows:

§93.152 Definitions.

* * * * *

Applicability analysis is the process of determining if your 

federal action must be supported by a conformity determination.

Applicable implementation plan or applicable SIP means the 

portion (or portions) of the SIP or most recent revision 

thereof, which has been approved under section 110(k) of the 

Act, a federal implementation plan promulgated under section 

110(c) of the Act, or a plan promulgated or approved pursuant to 

section 301 (d) of the Act (Tribal implementation plan or TIP) 

and which implements the relevant requirements of the Act.

Areawide air quality modeling analysis means an assessment on a 

scale that includes the entire nonattainment or maintenance area 

using an air quality dispersion model or photochemical grid 

model to determine the effects of emissions on air quality, for 

example, an assessment using EPA's community multi-scale air 

quality (CMAQ) modeling system.

* * * * *

Confidential business information (CBI) means information that 

has been determined by a federal agency, in accordance with its 

applicable regulations, to be a trade secret, or commercial or 

financial information obtained from a person and privileged or 
104

confidential and is exempt from required disclosure under the 

Freedom of Information Act (5 U.S.C. 552(b)(4)).

Conformity determination is the evaluation (made after an 

applicability analysis is completed) that a federal action 

conforms to the applicable implementation plan and meets the 

requirements of this subpart.

Conformity evaluation is the entire process from the 

applicability analysis through the conformity determination that 

is used to demonstrate that the federal action conforms to the 

requirements of this subpart.

Continuing program responsibility means a federal agency has 

responsibility for emissions caused by:

(1) Actions it takes itself; or

(2) Actions of non-federal entities that the federal agency, in 

exercising its normal programs and authorities, approves, funds, 

licenses or permits, provided the agency can impose conditions 

on any portion of the action that could affect the emissions.

Continuous program to implement means that the federal agency 

has started the action identified in the plan and does not stop 

the actions for more than an 18-month period, unless it can 

demonstrate that such a stoppage was included in the original 

plan.

* * * * *

Direct emissions means those emissions of a criteria pollutant 
105

or its precursors that are caused or initiated by the federal

action and originate in a nonattainment or maintenance area and 

occur at the same time and place as the action and are 

reasonably foreseeable.

* * * * *

Emission Inventory means a listing of information on the 

location, type of source, type and quantity of pollutant emitted 

as well as other parameters of the emissions.

* * * * *

EPA means the U.S. Environmental Protection Agency.

* * * * *

Indirect emissions means those emissions of a criteria pollutant 

or its precursors:

(1) That are caused or initiated by the Federal action and 

originate in the same nonattainment or maintenance area but 

occur at a different time or place as the action;

(2) That are reasonably foreseeable;

(3) That the agency can practically control; and

(4) For which the agency has continuing program responsibility.

For the purposes of this definition, even if a federal 

licensing, rulemaking or other approving action is a required 

initial step for a subsequent activity that causes emissions, 

such initial steps do not mean that a Federal agency can 

practically control any resulting emissions.
106

* * * * *

Local air quality modeling analysis means an assessment of 

localized impacts on a scale smaller than the entire 

nonattainment or maintenance area, including, for example, 

congested roadways on a federal facility, which uses an air 

quality dispersion model (e.g., Industrial Source Complex Model 

or Emission and Dispersion Model System) to determine the 

effects of emissions on air quality.

Maintenance area means an area that was designated as 

nonattainment and has been re-designated in 40 CFR part 81 to 

attainment, meeting the provisions of section 107(d)(3)(E) of 

the Act and has a maintenance plan approved under section 175A 

of the Act.

* * * * *

Metropolitan Planning Organization (MPO) means the policy board 

of an organization created as a result of the designation 

process in 23 U.S.C. 134(d).

* * * * *

Mitigation measure means any method of reducing emissions of the 

pollutant or its precursor taken at the location of the federal

action and used to reduce the impact of the emissions of that 

pollutant caused by the action.

* * * * *

National ambient air quality standards (NAAQS) are those 
107

standards established pursuant to section 109 of the Act and 

include standards for carbon monoxide (CO), lead (Pb), nitrogen 

dioxide (NO2), ozone, particulate matter (PM-10 and PM2.5), and 

sulfur dioxide (SO2).

* * * * *

Precursors of a criteria pollutant are:

* * * * *

(3) * * *

(i) Sulfur dioxide (SO2) in all PM2.5 nonattainment and 

maintenance areas, 

(ii) Nitrogen oxides in all PM2.5 nonattainment and maintenance 

areas unless both the state and EPA determine that it is not a 

significant precursor, and

(iii) Volatile organic compounds (VOC) and ammonia (NH3) only in 

PM2.5 nonattainment or maintenance areas where either the state

or EPA determines that they are significant precursors.

Reasonably foreseeable emissions are projected future direct and 

indirect emissions that are identified at the time the 

conformity determination is made; the location of such emissions 

is known and the emissions are quantifiable as described and 

documented by the federal agency based on its own information

and after reviewing any information presented to the federal

agency.

* * * * *
108

Restricted Information is information that is privileged or that 

is otherwise protected from disclosure pursuant to applicable 

statutes, Executive Orders, or regulations. Such information 

includes, but is not limited to: Classified national security 

information, protected critical infrastructure information, 

sensitive security information, and proprietary business 

information.

Take or start the federal action means the date that the federal

agency signs or approves the permit, license, grant or contract 

or otherwise physically begins the federal action that requires 

a conformity evaluation under this subpart.

* * * * *

Tribal implementation plan (TIP) means a plan to implement the 

national ambient air quality standards adopted and submitted by 

a federally recognized Indian tribal government determined to be 

eligible under 40 CFR 49.9 and the plan has been approved by 

EPA.

8. Section 93.153 is amended as follows:

a. By revising the table in paragraph (b)(1).

b. By adding paragraph (c)(2)(xxii).

c. By revising paragraphs (d)(1) and (d)(2).

d. By revising paragraph (e)(2).

e. By adding paragraph (e)(3).

f. By revising paragraph (f).
109

g. By revising paragraph (g) introductory text.

h. By adding paragraph (g)(3).

i. By revising paragraphs (h) introductory text, (h)(1), (h)(2), 

and (h)(4).

j. By revising paragraphs (i), (j), and (k).

§93.153 Applicability analysis.

* * * * *

(1) For purposes of paragraph (b) of this section, the following 

rates apply in nonattainment areas (NAA's):

-------------------------------------------------------

Tons/year

-------------------------------------------------------

Ozone (VOC's or NOX):

 Serious NAA's................................50

 Severe NAA's.................................25

 Extreme NAA's................................10

 Other ozone NAA's outside 

 an ozone transport region..................100

 Other ozone NAA's inside an ozone transport region:

 VOC..........................................50

 NOX.........................................100

Carbon monoxide: All NAA's......................100

SO2 or NO2: All NAA's...........................100

PM-10:
110

 Moderate NAA's..............................100

 Serious NAA's................................70

PM2.5:

 Direct emissions............................100

 SO2.........................................100

 NOX (unless determined 

 not to be significant precursors)...........100

 VOC or ammonia (if determined 

 to be significant precursors)...............100

Pb: 

 All NAA's....................................25

-------------------------------------------------------

* * * * *

(c) * * *

(2) * * *

(xxii) Air traffic control activities and adopting approach, 

departure, and enroute procedures for aircraft operations above 

the mixing height specified in the applicable SIP or TIP. Where 

the applicable SIP or TIP does not specify a mixing height, the 

federal agency can use the 3,000 feet above ground level as a 

default mixing height, unless the agency demonstrates that use 

of a different mixing height is appropriate because the change 

in emissions at and above that height caused by the federal 

action is de minimis.
111

* * * * *

(d) * * *

(1) The portion of an action that includes major or minor new or 

modified stationary sources that require a permit under the new 

source review (NSR) program (§110(a)(2)(c) and §173 of the Act) 

or the prevention of significant deterioration program (title I, 

part C of the Act).

(2) Actions in response to emergencies which are typically 

commenced on the order of hours or days after the emergency and, 

if applicable, which meet the requirements of paragraph (e) of 

this section.

* * * * *

(e) * * *

(2) For actions which are to be taken after those actions 

covered by paragraph (e)(1) of this section, the federal agency 

makes a new determination as provided in paragraph (e)(1) of 

this section and:

(i) Provides a draft copy of the written determinations required 

to affected EPA Regional office(s), the affected state(s) and/or 

air pollution control agencies, and any federal recognized 

Indian tribal government in the nonattainment or maintenance 

area. Those organizations must be allowed 15 days from the 

beginning of the extension period to comment on the draft 

determination; and
112

(ii) Within 30 days after making the determination, publish a 

notice of the determination by placing a prominent advertisement 

in a daily newspaper of general circulation in the area affected 

by the action.

(3) If additional actions are necessary in response to an 

emergency or disaster under paragraph (d)(2) of this section 

beyond the specified time period in paragraph (e)(2) of this 

section, a federal agency can make a new written determination 

as described in (e)(2) of this section for as many 6-month 

periods as needed, but in no case shall this exemption extend 

beyond three 6-month periods except where an agency:

(i) provides information to EPA and the state or tribe stating 

that the conditions that gave rise to the emergency exemption 

continue to exist and how such conditions effectively prevent 

the agency from conducting a conformity evaluation.

(ii) [Reserved]

(f) Notwithstanding other requirements of this subpart, actions 

specified by individual federal agencies that have met the 

criteria set forth in either paragraphs (g)(1), (g)(2), or 

(g)(3) of this section and the procedures set forth in paragraph 

(h) of this section are “presumed to conform,” except as 

provided in paragraph (j) of this section. Actions specified by 

individual federal agencies as “presumed to conform” may not be 

used in combination with one another when the total direct and 
113

indirect emissions from the combination of actions would equal 

or exceed any of the rates specified in paragraphs (b)(1) or (2) 

of this section.

(g) The federal agency must meet the criteria for establishing 

activities that are “presumed to conform” by fulfilling the 

requirements set forth in either paragraphs (g)(1), (g)(2), or 

(g)(3) of this section:

* * * * *

(3) The federal agency must clearly demonstrate that the 

emissions from the type or category of actions and the amount of 

emissions from the action are included in the applicable SIP and 

the state, local, or tribal air quality agencies responsible for 

the SIP(s) or TIP(s) provide written concurrence that the 

emissions from the actions along with all other expected 

emissions in the area will not exceed the emission budget in the 

SIP.

(h) In addition to meeting the criteria for establishing 

exemptions set forth in paragraphs (g)(1), (g)(2), or (g)(3) of 

this section, the following procedures must also be complied 

with to presume that activities will conform:

(1) The federal agency must identify through publication in the 

Federal Register its list of proposed activities that are 

“presumed to conform” and the basis for the presumptions. The 

notice must clearly identify the type and size of the action 
114

that would be “presumed to conform” and provide criteria for 

determining if the type and size of action qualifies it for the 

presumption;

(2) The federal agency must notify the appropriate EPA Regional 

Office(s), state, local, and tribal air quality agencies and, 

where applicable, the agency designated under section 174 of the 

Act and the MPO and provide at least 30 days for the public to 

comment on the list of proposed activities “presumed to 

conform”. If the “presumed to conform” action has regional or 

national application (e.g., the action will cause emission 

increases in excess of the de minimis levels identified in 

paragraph (b) of this section in more than one of EPA's 

Regions), the federal agency, as an alternative to sending it to 

EPA Regional Offices, can send the draft conformity 

determination to U.S. EPA, Office of Air Quality Planning and 

Standards;

* * * * *

(4) The federal agency must publish the final list of such 

activities in the Federal Register.

(i) Emissions from the following actions are “presumed to 

conform”:

(1) Actions at installations with facility-wide emission budgets 

meeting the requirements in §93.161 provided that the state or 

tribe has included the emission budget in the EPA-approved SIP 
115

and the emissions from the action along with all other emissions 

from the installation will not exceed the facility-wide emission 

budget.

(2) Prescribed fires conducted in accordance with a smoke 

management program (SMP) which meets the requirements of EPA's 

Interim Air Quality Policy on Wildland and Prescribed Fires or 

an equivalent replacement EPA policy.

(3) Emissions for actions that the state or tribe identifies in 

the EPA approved SIP or TIP as “presumed to conform”.

(j) Even though an action would otherwise be “presumed to 

conform” under paragraph (f) or (i) of this section, an action 

shall not be “presumed to conform” and the requirements of 

§93.150, §93.151, §§93.154 through 93.160 and §§93.162 through 

93.164 shall apply to the action if EPA or a third party shows 

that the action would:

(i) Cause or contribute to any new violation of any standard in 

any area;

(ii) Interfere with provisions in the applicable SIP or TIP for 

maintenance of any standard;

(iii) Increase the frequency or severity of any existing 

violation of any standard in any area; or

(iv) Delay timely attainment of any standard or any required 

interim emissions reductions or other milestones in any area

including, where applicable, emission levels specified in the 
116

applicable SIP or TIP for purposes of:

(A) A demonstration of reasonable further progress;

(B) A demonstration of attainment; or

(C) A maintenance plan.

(k) The provisions of this subpart shall apply in all 

nonattainment and maintenance areas except conformity 

requirements for newly designated nonattainment areas are not 

applicable until 1 year after the effective date of the final 

nonattainment designation for each NAAQS and pollutant in 

accordance with section 176(c)(6) of the Act.

9. Section 93.154 is revised to read as follows:

§93.154 Federal agency conformity responsibility.

Any department, agency, or instrumentality of the federal

government taking an action subject to this subpart must make 

its own conformity determination consistent with the 

requirements of this subpart. In making its conformity 

determination, a federal agency must follow the requirements in 

§§93.155 through 93.160 and §§93.162 through 93.165 and must 

consider comments from any interested parties. Where multiple 

federal agencies have jurisdiction for various aspects of a 

project, a federal agency may choose to adopt the analysis of 

another federal agency or develop its own analysis in order to 

make its conformity determination.

10. Section 93.155 is revised to read as follows:
117

§93.155 Reporting requirements.

(a) A federal agency making a conformity determination under 

§§93.154 through 93.160 and §§93.162 through 93.164 must provide 

to the appropriate EPA Regional Office(s), state and local air 

quality agencies, any federally-recognized Indian tribal

government in the nonattainment or maintenance area, and, where 

applicable, affected federal land managers, the agency 

designated under section 174 of the Act and the MPO, a 30-day 

notice which describes the proposed action and the federal

agency's draft conformity determination on the action. If the 

action has multi-regional or national impacts (e.g., the action 

will cause emission increases in excess of the de minimis levels 

identified in §93.153(b) in three or more of EPA's Regions), the 

federal agency, as an alternative to sending it to EPA Regional 

Offices, can provide the notice to EPA's Office of Air Quality 

Planning and Standards.

(b) A federal agency must notify the appropriate EPA Regional 

Office(s), state and local air quality agencies, any federallyrecognized Indian tribal government in the nonattainment or 

maintenance area, and, where applicable, affected federal land 

managers, the agency designated under section 174 of the Clean 

Air Act and the MPO, within 30 days after making a final 

conformity determination under this subpart.

(c) The draft and final conformity determination shall exclude 
118

any restricted information or confidential business information. 

The disclosure of restricted information and confidential 

business information shall be controlled by the applicable laws, 

regulations, security manuals, or executive orders concerning 

the use, access, and release of such materials. Subject to 

applicable procedures to protect restricted information from 

public disclosure, any information or materials excluded from 

the draft or final conformity determination or supporting 

materials may be made available in a restricted information 

annex to the determination for review by federal and state

representatives who have received appropriate clearances to 

review the information.

11. Section 93.156 is revised to read as follows:

§93.156 Public participation.

(a) Upon request by any person regarding a specific federal 

action, a federal agency must make available, subject to the 

limitation in paragraph (e) of this section, for review its 

draft conformity determination under §93.154 with supporting 

materials which describe the analytical methods and conclusions 

relied upon in making the applicability analysis and draft 

conformity determination.

(b) A federal agency must make public its draft conformity 

determination under §93.154 by placing a notice by prominent 

advertisement in a daily newspaper of general circulation in the 
119

area affected by the action and by providing 30 days for written 

public comment prior to taking any formal action on the draft 

determination. This comment period may be concurrent with any 

other public involvement, such as occurs in the National 

Environmental Policy Act (NEPA) process. If the action has 

multi-regional or national impacts (e.g., the action will cause 

emission increases in excess of the de minimis levels identified 

in §93.153(b) in three or more of EPA's Regions), the federal

agency, as an alternative to publishing separate notices, can 

publish a notice in the Federal Register.

(c) A federal agency must document its response to all the 

comments received on its draft conformity determination under 

§93.154 and make the comments and responses available, subject 

to the limitation in paragraph (e) of this section, upon request 

by any person regarding a specific federal action, within 30 

days of the final conformity determination.

(d) A federal agency must make public its final conformity 

determination under §93.154 for a federal action by placing a 

notice by prominent advertisement in a daily newspaper of 

general circulation in the area affected by the action within 30 

days of the final conformity determination. If the action would 

have multi-regional or national impacts, the federal agency, as 

an alternative, can publish the notice in the Federal Register.

(e) The draft and final conformity determination shall exclude 
120

any restricted information or confidential business information. 

The disclosure of restricted information and confidential 

business information shall be controlled by the applicable laws, 

regulations or executive orders concerning the release of such 

materials.

12. Section 93.157 is revised to read as follows:

§93.157 Reevaluation of conformity.

(a) Once a conformity determination is completed by a federal

agency, that determination is not required to be re-evaluated if 

the agency has: maintained a continuous program to implement the 

action; the determination has not lapsed as specified in 

paragraph (b) of this section; or any modification to the action 

does not result in an increase in emissions above the levels 

specified in §93.153(b). If a conformity determination is not 

required for the action at the time NEPA analysis is completed, 

the date of the finding of no significant impact (FONSI) for an 

Environmental Assessment, a record of decision (ROD) for an 

Environmental Impact Statement, or a categorical exclusion 

determination can be used as a substitute date for the 

conformity determination date.

(b) The conformity status of a federal action automatically 

lapses 5 years from the date a final conformity determination is 

reported under §93.155, unless the federal action has been 

completed or a continuous program to implement the federal
121

action has commenced.

(c) Ongoing federal activities at a given site showing 

continuous progress are not new actions and do not require 

periodic re-determinations so long as such activities are within 

the scope of the final conformity determination reported under 

§93.155.

(d) If the federal agency originally determined through the 

applicability analysis that a conformity determination was not 

necessary because the emissions for the action were below the 

limits in §93.153(b) and changes to the action would result in 

the total emissions from the action being above the limits in 

§93.153(b), then the federal agency must make a conformity 

determination.

13. Section 93.158 is amended as follows:

a. Revising paragraphs (a)(1), (a)(2), (a)(3) introductory text 

and (a)(4) introductory text;

b. Revising paragraph (a)(5) introductory text;

c. Revising paragraphs (a)(5)(i) introductory text, and 

(a)(5)(i)(C;

d. Adding paragraph(a)(5)(i)(D).

e. Revising paragraphs (a)(5)(iii), (a)(5)(iv) introductory 

text; (a)(5)(iv)(A)(1), (a)(5)(iv)(A)(2) and paragraph 

(a)(5)(iv)(B).

§93.158 Criteria for determining conformity of general federal
122

actions.

(a) * * *

(1) For any criteria pollutant or precursor, the total of direct 

and indirect emissions from the action are specifically 

identified and accounted for in the applicable SIP's attainment 

or maintenance demonstration or reasonable further progress 

milestone or in a facility-wide emission budget included in a 

SIP accordance with §93.161;

(2) For precursors of ozone, nitrogen dioxide, or PM, the total 

of direct and indirect emissions from the action are fully 

offset within the same nonattainment or maintenance area (or 

nearby area of equal or higher classification provided the 

emissions from that area contribute to the violations, or have 

contributed to violations in the past, in the area with the 

federal action) through a revision to the applicable SIP or a 

similarly enforceable measure that effects emissions reductions 

so that there is no net increase in emissions of that pollutant;

(3) For any directly-emitted criteria pollutant, the total of 

direct and indirect emissions from the action meets the 

requirements:

* * * * *

(4) For CO or directly emitted PM--

* * * * *

(5) For ozone or nitrogen dioxide, and for purposes of 
123

paragraphs (a)(3)(ii) and (a)(4)(ii) of this section, each 

portion of the action or the action as a whole meets any of the 

following requirements:

(i) Where EPA has approved a revision to the applicable 

implementation plan after the area was designated as 

nonattainment and the state or tribe makes a determination as 

provided in paragraph (a)(5)(i)(A) of this section or where the 

state or tribe makes a commitment as provided in paragraph 

(a)(5)(i)(B) of this section:

* * * * *

(C) Where a federal agency made a conformity determination based 

on a state’s or tribe’s commitment under paragraph (a)(5)(i)(B) 

of this section and the state has submitted a SIP or TIP to EPA 

covering the time period during which the emissions will occur 

or is scheduled to submit such a SIP or TIP within 18 months of 

the conformity determination, the state commitment is 

automatically deemed a call for a SIP or TIP revision by EPA 

under section 110(k)(5) of the Act, effective on the date of the 

federal conformity determination and requiring response within 

18 months or any shorter time within which the state or tribe

commits to revise the applicable SIP;

(D) Where a federal agency made a conformity determination based 

on a state or tribal commitment under paragraph (a)(5)(i)(B) of 

this section and the state or tribe has not submitted a SIP 
124

covering the time period when the emissions will occur or is not 

scheduled to submit such a SIP within 18 months of the 

conformity determination, the state or tribe must, within 18 

months, submit to EPA a revision to the existing SIP committing 

to include the emissions in the future SIP revision.

* * * * *

(iii) The action (or portion thereof) fully offsets its 

emissions within the same nonattainment or maintenance area (or 

nearby area of equal or higher classification provided the 

emissions from that area contribute to the violations, or have 

contributed to violation in the past, in the area with the 

federal action) through a revision to the applicable SIP or an 

equally enforceable measure that effects emissions reductions 

equal to or greater than the total of direct and indirect 

emissions from the action so that there is no net increase in 

emissions of that pollutant;

(iv) Where EPA has not approved a revision to the relevant SIP 

since the area was designated or reclassified, the total of 

direct and indirect emissions from the action for the future 

years (described in §93.159(d)) do not increase emissions with 

respect to the baseline emissions:

(A) * * *

(1) The most current calendar year with a complete emission 

inventory available before an area is designated unless EPA sets 
125

another year; or

(2) The emission budget in the applicable SIP;

* * * * *

(B) The baseline emissions are the total of direct and indirect 

emissions calculated for the future years (described in 

§93.159(d)) using the historic activity levels (described in 

paragraph (a)(5)(iv)(A) of this section) and appropriate 

emission factors for the future years; or

* * * * *

14. Section 93.159 is amended as follows:

a. Revising paragraphs (b) introductory text and (b)(1)(ii);

b. Revising paragraphs (b)(2) and (c) introductory text; and

c. Removing footnotes 1 and 2,

d. Revising paragraph (d).

The revisions and additions read as follows:

§93.159 Procedures for conformity determinations of general 

Federal actions.

* * * * *

(b) The analyses required under this subpart must be based on 

the latest and most accurate emission estimation techniques 

available as described below, unless such techniques are 

inappropriate. If such techniques are inappropriate, the federal

agency may obtain written approval from the appropriate EPA 

Regional Administrator for a modification or substitution, of 
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another technique on a case-by-case basis or, where appropriate, 

on a generic basis for a specific federal agency program.

(1) * * *

(ii) A grace period of 3 months shall apply during which the 

motor vehicle emissions model previously specified by EPA as the 

most current version may be used unless EPA announces a longer 

grace period in the Federal Register. Conformity analyses for 

which the analysis was begun during the grace period or no more 

than 3 months before the Federal Register notice of availability 

of the latest emission model may continue to use the previous 

version of the model specified by EPA.

(2) For non-motor vehicle sources, including stationary and area 

source emissions, the latest emission factors specified by EPA 

in the 

“Compilation of Air Pollutant Emission Factors” (AP-42, 

http://www.epa.gov/ttn/chiefs/efpac) must be used for the 

conformity analysis unless more accurate emission data are 

available, such as actual stack test data from the stationary 

sources which are part of the conformity analysis.

(c) The air quality modeling analyses required under this 

subpart must be based on the applicable air quality models, data 

bases, and other requirements specified in the most recent 

version of the “Guideline on Air Quality Models.” (Appendix W to 

40 CFR part 51).
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* * * * *

(d) The analyses required under this subpart must be based on 

the total of direct and indirect emissions from the action and 

must reflect emission scenarios that are expected to occur under 

each of the following cases:

(1) The attainment year specified in the SIP, or if the SIP does 

not specify an attainment year, the latest attainment year 

possible under the Act; or

(2) The last year for which emissions are projected in the 

maintenance plan;

(3) The year during which the total of direct and indirect 

emissions from the action is expected to be the greatest on an 

annual basis; and

(4) Any year for which the applicable SIP specifies an emissions 

budget.

15. Section 93.160 is amended as follows:

a. Revising paragraph (e);

b. Revising paragraph (f); and

c. Revising paragraph (g).

§93.160 Mitigation of air quality impacts.

* * * * *

(e) When necessary because of changed circumstances, mitigation 

measures may be modified so long as the new mitigation measures 

continue to support the conformity determination. Any proposed 
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change in the mitigation measures is subject to the reporting 

requirements of §93.156 and the public participation 

requirements of §93.157.

(f) Written commitments to mitigation measures must be obtained 

prior to a positive conformity determination and such 

commitments must be fulfilled.

(g) After a state or tribe revises its SIP or TIP and EPA 

approves that SIP revision, any agreements, including mitigation 

measures, necessary for a conformity determination will be both 

state or tribal and federally enforceable. Enforceability 

through the applicable SIP or TIP will apply to all persons who 

agree to mitigate direct and indirect emissions associated with 

a federal action for a conformity determination.

16. Subpart B is amended by adding §93.161 to read as follows:

§93.161 Conformity evaluation for federal installations with 

facility-wide emission budgets.

(a) The state, local or tribal agency responsible for 

implementing and enforcing the SIP or TIP can in cooperation 

with federal agencies or third parties authorized by the agency 

that operate installations subject to federal oversight develop 

and adopt a facility-wide emission budget to be used for 

demonstrating conformity under §93.158(a)(1). The facility-wide 

budget must meet the following criteria:

(1) Be for a set time period;
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(2) Cover the pollutants or precursors of the pollutants for 

which the area is designated nonattainment or maintenance;

(3) Include specific quantities allowed to be emitted on an 

annual or seasonal basis;

(4) The emissions from the facility along with all other 

emissions in the area will not exceed the emission budget for 

the area;

(5) Include specific measures to ensure compliance with the 

budget, such as periodic reporting requirements or compliance 

demonstration, when the federal agency is taking an action that 

would otherwise require a conformity determination;

(6) Be submitted to EPA as a SIP revision;

(7) The SIP revision must be approved by EPA.

(b) The facility-wide budget developed and adopted in accordance 

with paragraph (a) of this section can be revised by following 

the requirements in paragraph (a) of this section.

(c) Total direct and indirect emissions from federal actions in 

conjunction with all other emissions subject to General 

Conformity from the facility that do not exceed the facility 

budget adopted pursuant to paragraph (a) of this section are 

“presumed to conform” to the SIP and do not require a conformity 

analysis.

(d) If the total direct and indirect emissions from the federal

actions in conjunction with the other emissions subject to 
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General Conformity from the facility exceed the budget adopted 

pursuant to paragraph (a) of this section, the action must be 

evaluated for conformity. A federal agency can use the 

compliance with the facility-wide emissions budget as part of 

the demonstration of conformity, i.e., the agency would have to 

mitigate or offset the emissions that exceed the emission 

budget.

(e) If the SIP for the area includes a category for construction 

emissions, the negotiated budget can exempt construction 

emissions from further conformity analysis.

17. Subpart B is amended by adding §93.162 to read as follows:

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

If a federal action would result in total direct and indirect 

emissions above the applicable thresholds which would be emitted 

beyond the time period covered by the SIP, the federal agency 

can:

(a) Demonstrate conformity with the last emission budget in the 

SIP; or

(b) Request the state or tribe to adopt an emissions budget for 

the action for inclusion in the SIP. The state or tribe must 

submit a SIP or TIP revision to EPA within 18 months either 

including the emissions in the existing SIP or establishing an 

enforceable commitment to include the emissions in future SIP 

revisions based on the latest planning assumptions at the time 
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of the SIP revision. No such commitment by a state or tribe

shall restrict a state's or tribe’s ability to require RACT, 

RACM or any other control measures within the state's or tribe’s

authority to ensure timely attainment of the NAAQS.

18. Subpart B is amended by adding §193.163 to read as follows:

§93.163 Timing of offsets and mitigation measures.

(a) The emissions reductions from an offset or mitigation 

measure used to demonstrate conformity must occur during the 

same calendar year as the emission increases from the action 

except, as provided in paragraph (b) of this section.

(b) The state or tribe may approve emissions reductions in other 

years provided:

(1) The reductions are greater than the emission increases by 

the following ratios:

(i) Extreme nonattainment areas........... 1.5:1

(ii) Severe nonattainment areas............1.3:1

(iii) Serious nonattainment areas..........1.2:1

(iv) Moderate nonattainment areas.........1.15:1

(v) All other areas........................1.1:1

(2) The time period for completing the emissions reductions must 

not exceed twice the period of the emissions.

(3) The offset or mitigation measure with emissions reductions 

in another year will not:

(i) Cause or contribute to a new violation of any air quality 
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standard, 

(ii) Increase the frequency or severity of any

existing violation of any air quality standard; or

(iii) Delay the timely attainment of any standard or any interim 

emissions reductions or other milestones in any area.

(c) The approval by the state or tribe of an offset or 

mitigation measure with emissions reductions in another year 

does not relieve the state or tribe of any obligation to meet 

any SIP or Clean Air Act milestone or deadline. The approval of 

an alternate schedule for mitigation measures is at the 

discretion of the state or tribe, and they are not required to 

approve an alternate schedule. 

19. Subpart B is amended by adding §93.164 to read as follows:

§93.164 Inter-precursor mitigation measures and offsets.

Federal agencies must reduce the same type of pollutant as being 

increased by the federal action except the state or tribe may 

approve offsets or mitigation measures of different precursors 

of the same criteria pollutant, if such trades are allowed by a 

state or tribe in a SIP or TIP approved NSR regulation, is 

technically justified, and has a demonstrated environmental 

benefit.

20. Subpart B is amended by adding §93.165 to read as follows:

§93.165 Early emission reduction credit programs at federal

facilities and installation subject to federal oversight.
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(a) Federal facilities and installation subject to federal

oversight can, with the approval of the state or tribal agency 

responsible for the SIP or TIP in that area, create an early 

emissions reductions credit program. The federal agency can 

create the emission reduction credits in accordance with the 

requirements in paragraph (b) of this section and can use them 

in accordance with paragraph (c) of this section.

(b) Creation of emission reduction credits. 

(1) Emissions reductions must be quantifiable through the use of 

standard emission factors or measurement techniques. If nonstandard factors or techniques to quantify the emissions 

reductions are used, the federal agency must receive approval 

from the state or tribal agency responsible for the 

implementation of the SIP or TIP and from EPA's Regional Office. 

The emission reduction credits do not have to be quantified 

before the reduction strategy is implemented, but must be 

quantified before the credits are used in the General Conformity 

evaluation.

(2) The emission reduction methods must be consistent with the

applicable SIP or TIP attainment and reasonable further progress 

demonstrations.

(3) The emissions reductions can not be required by or credited 

to other applicable SIP or TIP provisions.

(4) Both the state or tribe and federal air quality agencies 
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must be able to take legal action to ensure continued 

implementation of the emission reduction strategy. In addition, 

private citizens must also be able to initiate action to ensure 

compliance with the control requirement.

(5) The emissions reductions must be permanent or the timeframe 

for the reductions must be specified.

(6) The federal agency must document the emissions reductions 

and provide a copy of the document to the state or tribal air 

quality agency and the EPA regional office for review. The 

documentation must include a detailed description of the 

emission reduction strategy and a discussion of how it meets the 

requirements of paragraphs (b)(1) through (5) of this section.

(c) Use of emission reduction credits. The emission reduction 

credits created in accordance with paragraph (b) of this section 

can be used, subject to the following limitations, to reduce the 

emissions increase from a federal action at the facility for the 

conformity evaluation.

(1) If the technique used to create the emission reduction is 

implemented at the same facility as the federal action and could 

have occurred in conjunction with the federal action, then the 

credits can be used to reduce the total direct and indirect 

emissions used to determine the applicability of the regulation

as required in §93.153 and as offsets or mitigation measures 

required by §93.158.
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(2) If the technique used to create the emission reduction is 

not implemented at the same facility as the federal action or 

could not have occurred in conjunction with the federal action, 

then the credits cannot be used to reduce the total direct and 

indirect emissions used to determine the applicability of the 

regulation as required in §93.153, but can be used to offset or 

mitigate the emissions as required by §93.158.

(3) Emissions reductions credits must be used in the same year 

in which they are generated.

(4) Once the emission reduction credits are used, they cannot be 

used as credits for another conformity evaluation. However, 

unused credits from a strategy used for one conformity 

evaluation can be used for another conformity evaluation as long 

as the reduction credits are not double counted. 

(5) Federal agencies must notify the state or tribal air quality 

agency responsible for the implementation of the SIP or TIP and 

EPA Regional Office when the emission reduction credits are 

being used.