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General Conformity

General Conformity Training Module 3.1: Applicability Analyses

Words that are shown in bold and italics are defined in the Glossary.

3.1.1 Nonattainment and maintenance areas

The Conformity Regulations apply only to pollutants or their precursors that are emitted in designated nonattainment or maintenance areas. Federal actions that cause emissions only in areas not designated as nonattainment or maintenance, such as attainment or unclassified areas, are not required to evaluate conformity for the action even though the emissions may impact a nonattainment or maintenance area.

The official record of the area’s attainment status is in Title 40 of the Code of Federal Regulations, part 81. EPA periodically revises the designations or classifications by publishing the revisions in the Federal Register. In addition, EPA makes the attainment status of areas available by publishing a document known as the “Green book,” which is also available on the EPA Green Book web site. Specific details about the nonattainment or maintenance area can also be obtained by contacting the state, tribal, or local air quality agencies responsible for the area. Additional assistance may be obtained at the EPA Regional Office. The list of EPA’s Regional Offices is available on the General Conformity website under "Contact Us."

The boundaries of the nonattainment and maintenance areas are generally defined in the designations. In most cases the boundaries are political boundaries such as county lines or are physical features (such as streets or rivers). However, in some cases the boundaries may not be well defined. For coastal areas, EPA interprets the nonattainment or maintenance area boundary to extend to the state’s seaward boundary, which for most of the United States, is 3 miles. The exceptions are Florida and Texas where the boundary is 3 leagues, approximately 9 miles. Federal agencies should consult with the state, tribal or local air quality agency about specific questions concerning the boundaries of the nonattainment or maintenance area. Under EPA’s Outer Continental Shelf (OCS) Air Regulations, (40 CFR 55), sources within 25 miles of the state’s seaward boundary and that are attached to the seabed must comply with the same regulations as if the sources were onshore. Therefore, those sources would also require a conformity evaluation if the nearest onshore land is a designated nonattainment or maintenance area. The OCS Air Regulations are applicable to all coastal waters except for the Western Gulf of Mexico (west of 87 o 30’, or the Florida/Alabama border).

Some federal actions involve emissions from aircraft at various elevations. The designations do not define the vertical height of the nonattainment or maintenance areas. Generally the area’s mixing height is used in air quality analyses; however, the mixing height is not constant and varies with meteorological conditions. If a specific mixing height is not defined by the state or tribe, EPA recommends that federal agencies use an average mixing height or a default height of 3000 feet above ground level. Federal agencies should consult with the state, tribal or local air quality agency about specific questions concerning the height of a nonattainment or maintenance area.

Besides designating nonattainment and maintenance areas, EPA also designates ozone transport regions (OTR). At the present time, EPA has only designated one OTR, which extends from Northern Virginia to New England. The purpose of the OTR is to coordinate the control of ozone precursors across the area. To that end, EPA has established special requirements for actions that cause emissions in the OTR. For example, EPA has established more restrictive de minimis emissions levels for lower classified nonattainment and maintenance areas in the OTR. Further information can be obtained from the Ozone Transport Commission, the individual states or EPA Regional Offices in Boston, New York and Philadelphia.

On occasion, federal agencies will take actions that will cause emissions in more than one nonattainment or maintenance area. These actions could affect two areas, such as an expansion of an airport that crosses the boundary between the two areas or could be national in scope affecting all of the areas. Since the SIPs and TIPs are designed for each area separately, the conformity evaluation is completed separately for each area. Emissions from the action are estimated for each area and compared with that area’s de minimis levels. If conformity demonstrations are necessary, they should show that for each area that exceeds the de minimis emission levels, the emissions conform with the SIP/TIP. Although each area is evaluated separately, the federal agency can combine the review and public notification process, provided the agency publishes notices in each area affected and notifies all affected states and tribes.

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3.1.2 Transportation projects

Federal actions covered by Transportation Conformity are exempt from the General Conformity requirements. Actions by some federal agencies could involve transportation-related projects such that a portion of the emissions caused by the action would be subject to the requirements of the Transportation Conformity Regulations and the remainder by the General Conformity Regulations. For example:

  • The local mass transit authority seeks approval to operate a commuter rail service over leased tracks owned or controlled by a federal agency. The agency can exclude any emissions that were included in the transportation planning process;
  • The local airport is seeking approval from the Federal Aviation Administration (FAA) for a plan to provide light rail service to the airport. The train station and a portion of the rail line will be on the airport property. The project is to be partially funded under the Federal Transit Act and has been included in the area’s transportation plan. Since the construction of the line and station are on the airport property and FAA approval is required, FAA would have to determine if the emissions from that portion of the project were above the de minimis levels. If so, the FAA would have to make a conformity determination before the approval could be granted. The emissions related to the operation of the line would be included in the Transportation Conformity analysis and FAA would not include them in their analysis;

3.1.3 Exempt actions

The EPA has identified a number of actions that are determined to be below the de minimis emission levels or otherwise are presumed to conform. De minimis Table (Module 2.1) lists those exemptions and identifies any guidance that EPA has provided on the exemption. Federal agencies can also develop their own list of presumed to conform actions. The development of such a list is discussed in Module 3.4. Questions about the exemptions should be addressed to the General Conformity contact in the EPA Region where the emissions are projected to occur.

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3.1.4 Conformity on tribal lands

Under the Clean Air Act, federally recognized Indian tribes are treated the same as states. Therefore, EPA has made a provision in the General Conformity Regulations for the tribal authority to review and comment on the draft demonstrations in the nonattainment or maintenance areas where the tribe is located. 

In most cases for tribal lands, either the tribe has developed a tribal implementation plan (TIP) for the area or EPA has promulgated a federal implementation plan (FIP) for the area. These plans generally take precedence over any state implementation plan (SIP) for the area. Federal agencies should consult with EPA regional general conformity contacts about the applicable plan for tribal lands.

Where EPA has approved a TIP, the tribal authority can provide documentation that the emissions for the proposed action are included in the TIP or can commit to including the emissions in existing or future TIPs. For the tribal areas where EPA has not approved the TIP and has promulgated a FIP for the area, EPA will perform those functions. Questions concerning the authority for TIP statements should be addressed to EPA’s regional general conformity contacts.

3.1.5 Grace period for new nonattainment designation

The regulations allow a one-year grace period before the conformity requirements apply to the area after the area is newly designated as nonattainment. When EPA publishes the designation of nonattainment for an area, it also identifies an effective date of the designation. The conformity requirements apply one year after the effective date of the designations. Actions that commence before that date do not have to meet the new conformity requirements. However, actions that commence on or after that date will have to meet the requirements for the area’s new designation . Since EPA proposes the designations before it publishes the final designations, federal agencies have more than a year to take the action before they would be required to demonstrate conformity. Changes in an area's nonattainment classification is not a new designation, therefore there is not a grace period. Likewise, where a new NAAQS is published by EPA and an area is found to continue to be nonattainment under the revised NAAQS, there is no grace period

3.1.6 Revisions to the General Conformity Regulations

When EPA revises its General Conformity Regulations, it also identifies an effective date for those revisions. Usually, the effective date of the regulations is 30 to 60 days after the publication of the promulgation final revisions in the Federal Register. Actions that commence before the effective date of the regulatory revisions do not have to meet the new requirements. However, actions that commence after the effective date of the revisions will have to meet any new requirement. Since EPA proposes the revisions before it promulgates the final revisions, federal agencies have more than 30-60 days to take the action before they would be required to meet any new requirement.

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