An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

General Conformity

General Conformity Training Module 2.3: Demonstrating Conformity

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

See Figure 4

2.3.1 Overview

If a federal agency determines that the emissions from an action are above the de minimis levels and the action is not otherwise exempt, then the agency must demonstrate that the action will conform with the SIP/TIP.

First, federal agencies must demonstrate that the action will meet SIP/TIP requirements and milestones including reasonable further emission reduction requirements. Such a demonstration can be made by comparing the emissions from the action to the inventory of emissions in the SIP/TIP, and by working with the state or tribal agency responsible for air quality control in the area.

There are six basic methods for demonstrating conformity:

1) Document that the emissions from the action are identified and accounted for in the SIP/TIP;

2) Obtain a statement from the applicable state, tribal, or local air quality agency that the emissions from the action along with all other emissions in the area do not exceed the budget for those emissions in the SIP/TIP;

3) Have the local Metropolitan Planning Organization (MPO) provide a statement that the emissions are included in transportation plan modeling;

4) Have the state or tribe agree to include the emissions in the SIP/TIP;

5) Conduct air quality modeling to demonstrate that the emissions will not cause or contribute to a violation of the NAAQS; this modeling option is not available for O3, NO2 and some PM 2.5 areas; or

6) Mitigate or offset the increase in emissions.

In addition, EPA has developed two alternative approaches for demonstrating conformity:

  • The emission reduction credits approach; and
  • The facility emission budget approach.

These programs allow the federal facilities affected by the General Conformity Regulations to manage the emissions to limit their need to demonstrate conformity for individual projects.

Top of Page

2.3.2 Mitigation of emissions

Federal agencies can mitigate or offset the emissions caused by the action by (a) redesigning the action to reduce the emissions, (b) reducing the same type of emissions elsewhere at the facility, or (c) by securing offsets in the same nonattainment or maintenance area or adjacent area with an equal or higher classification. The mitigation measures and offsets must meet certain requirements:

  • First, the mitigation measures must be in place before the project starts. Any agreement for the reduction of the emissions must be signed and included with the conformity demonstration;
  • The reduction in the emissions must at least equal the annual increase in emissions caused by the action. In a recent revision to the regulations, EPA added a provision to allow federal agencies under certain conditions and, with the approval of the state or tribe, to use long-term offsets for short-term increases in emissions;
  • The offset must be:
    • Quantifiable – The federal agency must be able to quantify the emissions reduced by the measure using standard techniques for determining emission reductions;
    • A surplus – The emission reduction measure must not be required by the SIP, TIP, or other environmental laws or regulations;
    • Enforceable – EPA or the state, tribe or local agency must have the ability to enforce the emission reduction measure. This can be done by including the measure in an operating permit or similar mechanism or by including the reductions in the SIP/TIP;
    • Permanent – The emission reductions must be permanent within the timeframe of the emission increases caused by the action. For example, if the action will result in construction emissions over a 5-year period, then the emission reduction measure must reduce the emissions over the same 5-year period; and
    • Adequately supported – The federal agency must show that there are adequate resources to implement the emission reduction measure;
  • The mitigation measures can be modified after the federal agency has completed its conformity demonstration by following the procedures used to establish the original measures;
  • EPA, states, tribes and local agencies will enforce the requirements of the emission reduction measures used as an offset. If a third party fails to meet its commitment in implementing the measures, the enforcement will generally be against the third party and not the federal agency.

2.3.3 Demonstrating conformity in the absence of an approved SIP

A federal agency may be taking actions in a nonattainment area where EPA has not approved the SIP/TIP for the area. In such a case, the federal agency’s options for demonstrating conformity for the action are limited. Since there is no SIP/TIP, the federal agency can secure a commitment from the state or tribe to include the emissions into the future SIP/TIP. The federal agency may still conduct modeling to demonstrate conformity or it may secure emission reductions to mitigate or offset the emission increases.

A second case of a federal agency addressing conformity in the absence of a SIP/TIP occurs when the emissions from a federal action will occur after the time period covered by the SIP/TIP. In this case, the federal agency can demonstrate conformity for the last budget in the SIP/TIP and assume that the future SIP/TIP will allow that quantity of emissions. The state, tribe or local agency would be responsible for developing the SIP/TIP to account for the emissions from the action. If the emissions from the action are greater than the emissions allowed in the last budget in the SIP/TIP, then the federal agency can secure a commitment from the state or tribe to include the emission in the future SIP/TIP.

2.3.4 Required analysis years

Federal agencies can choose to demonstrate conformity on a worst-case basis or on a year-to-year basis. Under the worst-case approach, the federal agency would show that the maximum emissions from the action would conform with the most stringent budget in the SIP/TIP. Under the year-to-year approach, the federal agency would demonstrate that each year the emissions for the action would conform with the SIP/TIP. The year-to-year approach may be useful for actions with specific end dates or with widely varying emissions such as construction projects.

Top of Page

Figure 4. Conformity Determination Process
(Click for links to relevant sections)

Figure 4. Conformity Determination Process

Top of Page

SIP emissions?add emissionsmitigate emissionsadd emissionsstate determinesin permitin budgetconformsmodeling methodcalculate emissionstype of modeloffset emissionsconformityend flow chartbaseline emissions