General Conformity Training Module 2.3: Demonstrating Conformity

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

2.3.1 Overview

Conformity is a federal statute established by Congress within the Clean Air Act (CAA) for the prevention and control of pollutants the Environmental Protection Agency (EPA) finds to be harmful to public health and the environment, and for which the EPA has therefore established National Ambient Air Quality Standards (NAAQS). States and Tribes have a legal obligation to attain and maintain these standards within nonattainment areas or re-designated attainment areas (hereafter referred to as a maintenance areas), over which they have jurisdiction and authority. To this end, States and Tribes adopt EPA-approved air pollution prevention and control plan revisions specifically for each nonattainment and maintenance area, referred to as an air quality implementation plan, that contains all the procedures and requirements to ensure timely attainment and maintenance of the NAAQS. All such plan revisions, collectively, because there can be more than one, that apply to a specific nonattainment or maintenance area is referred to as the application implementation plan (AIP). Failure to meet or maintain the NAAQS can result in negative consequences including, but not limited to, loss of federal funding for some State or Tribal programs. The NAAQS define the criteria that constitutes healthful outside ambient air relative to the concentration of so-called criteria pollutant emissions and emissions of their precursor pollutants.

The conformity rule intends to assist State and Tribes in timely attainment and maintenance of the NAAQS by limiting federal agency authorizations to only those federal projects, programs, plans, and activities that, if implemented, will not interfere with the ability of a State of Tribe to attain and maintain the NAAQS within nonattainment or maintenance areas, as defined under CAA 176(c)(5) and (c)(6), by acting in accordance with and conform to the purpose of the AIP (42 U.S.C. Chapter 85, Subchapter I).

All federal actions are defined within just two categories subject to the CAA conformity statute. The first includes transportation projects, programs, and plans related to mobile sources of emissions operating on federal highways and subject to the requirements of 40 CFR part 93 subpart A, referred to as Transportation Conformity. The second includes all other federal actions not subject to subpart A that are referred to as "general federal activities," including but not limited to, construction and operations activities, that are subject to the requirements of 40 CFR part 93 subpart B for General Conformity.

General Conformity prohibits federal agencies from authorizing any activities unless or until the federal agency proposing the activities assures the emissions will not, within nonattainment or maintenance areas affected by the activities (referred to as the affected area):

Cause or contribute to a new violation of the NAAQS;
Increase the frequency or severity of an existing NAAQS violation; or,
Delay timely attainment or maintenance of the NAAQS.

Activities causing emissions of criteria or precursor pollutants for which the affected area is or was designated nonattainment or re-designated attainment that would originate within the affected area (referred to as emissions of relevant pollutants) must be evaluated in the federal agency's applicability analysis, so long as the activities meet the applicability requirements § 93.153(a) or (b). In the applicability analysis, the federal agency would examine each proposed activity and exclude from the analysis any emissions caused by activities that:

The EPA describes as a category of activities that are presumed to conform (PTC) under § 93.153(i); or,
The EPA describes as an exemption when the federal agency's activity is consistent with the specific scope of the exemption listed in § 93.153(c)(2)-(4), (d), or (e); or,
The federal agency includes in its own list of PTC activities developed and published in the Federal Register, as required under § 93.153(f)-(h); or,
The State or Tribe includes in its own list of PTC activities in their General Conformity implementation plan revision allowed under § 93.151 and developed according to 40 CFR 51.851; or,
The Metropolitan Planning Organization (MPO) determines are caused by transportation-related sources that would be subject to Transportation Conformity under 40 CFR part 93 subpart A. Obtain documentation from the MPO to justify the excluded emissions.

Emissions caused by the activities that remain are included in the federal agency's net emissions increase analysis, where the federal agency would calculate the total of direct and indirect emissions for each year analyzed as specified under § 93.159(d). In this analysis, the federal agency would calculate the annual emissions projected for a future year caused by the proposed activities that would originate within the affected area, this is referred to as the "Build" scenario. This tabulated data is then compared to the annual emissions caused by existing sources of the same pollutants for the same future year that originate within the affected area, this is referred to as the "No-Build "scenario. The difference between the two, year by year, pollutant by pollutant, is referred to as the "total of direct and indirect emissions" (also referred to as the annual "net emissions"). The results of the comparison of the two scenarios will indicate whether there are any annual net increases, or annual net decreases, in the emissions of the relevant pollutants:

If for all years analyzed according to § 93.159(d), and for emissions of all relevant pollutants, the federal agency finds the annual net emissions would be less than the associated annual de minimis threshold rates given in the tables at § 93.153(b)(1) or (b)(2), the agency could prepare a De minimis finding that documents the analysis and reveals all the materials and data upon which the agency relied on to reach this conclusion. No conformity determination analysis is necessary, and the federal agency should retain its documentation in its files. There are no reporting or public participation requirements that apply under §§ 93.155 or 93.156 for a de minimis finding. The federal agency must not take or start its federal action until the General Conformity finding is complete.
If for one or more years analyzed according to § 93.159(d) the federal agency finds the annual net emissions would cause an increase in emissions that would meet or exceed the associated annual de minimis threshold rates given in the tables at § 93.153(b)(1) or (b)(2), the agency must prepare a demonstration analysis using the EPA § 93.158 criteria , which would be applied according to the procedures under § 93.159, and apply, as applicable, provisions under §§ 93.160 through 93.165 to show how the emissions will "meet conformity," meaning the emissions will conform to the purpose of the applicable implementation plan under CAA 176(c)(1)(A). The federal agency must then prepare a written conformity determination that explains and describes, based on the results of the applicability analysis and their demonstration, how the emissions will meet conformity. The agency must stipulate that the emissions caused by the activities will meet the conformity requirements as defined under Clean Air Act (CAA) § 176(c)(1)(A) and (B) and therefore will not interfere with the State's or Tribe's ability to meet and maintain the NAAQS. The federal agency must retain in its files all the information relied upon to prepare the demonstration and make their positive conformity determination. The federal agency must not take or start its federal action until the General Conformity determination is complete.

There are several methods for demonstrating conformity for net emissions that equal or exceed the associated de minimis threshold rates. The federal agency must apply one or a combination of the following methods to demonstrate, for each such year, applicable under § 93.159(d), that the entire increase in annual net emissions of relevant pollutants caused by the federal activities is reduced to zero or the agency must otherwise show the emissions will conform using air quality modeling. It is not enough to reduce or offset the emissions to a rate less than the associated de minimis rates. The § 93.158 methods include:

Document that some or all of the annual increases in net emissions are specifically identified and accounted for in the applicable implementation plan's attainment or maintenance demonstration, in the plan's reasonable further progress (RFP) milestones, or in a facility-wide emissions budget included in the applicable implementation plan in accordance with § 93.158(a)(1);
Document that some or all of the annual increases in net emissions are specifically accounted for in the applicable implementation plan's Early Emissions Reduction Credits program, developed by the federal agency as coordinated with and approved by the State or Tribal air agency, according to section § 93.165(b);
Apply mitigation measures to eliminate or otherwise reduce emissions, or obtain emissions offsets to offset the annual increase in net emissions according to the methods and requirements under §§ 93.161, 93.163, and 93.164, and according to the definition of emissions offsets under § 93.152;
Obtain documentation from the Metropolitan Planning Organization (MPO) if any of the annual increases in net emissions are caused by transportation-related sources, where the emissions are already included in a current transportation plan or transportation improvement plan, either of which must have been found to conform to the applicable implementation plan under Transportation Conformity (40 CFR part 93 subpart (A), 40 CFR part 51 subpart T, 40 CFR 51.851, or General Conformity at 40 CFR part 93 subpart B).
Request the state or Tribal air agency responsible for the applicable implementation plan to agree to submit a revision to the applicable implementation plan that will include some or all of the annual increases in net emissions caused by the project's activities;
If the area was so recently designated, reclassified, or redesignated that the responsible air agency has not yet completed the development of the required revised implementation plan or the EPA has not yet approved the plan, the agency must document that the annual increases in net emissions for the future years specified under section 93.159(d) do not increase with respect to the baseline emissions, according to the criteria under section 93.158(a)(5)(iv); or
The agency may, but is not required to, conduct air quality modeling to demonstrate that the annual increases in net emissions will meet the conformity requirements under CAA section 176(c)(1)(A) and (1)(B). Conformity means the emissions caused by activities included as part of the federal project and which are applicable under the provisions of General Conformity, will conform to the purpose of the applicable implementation plan within nonattainment areas or maintenance areas, and will not cause or contribute to a new NAAQS violation within the area, will not increase the frequency or severity of the area's existing NAAQS violation within the area, and will not delay timely attainment or maintenance of the NAAQS within the area.
The agency may redesign the federal project or the individual activities subject to General Conformity to reduce all or part of the annual increases in net emissions, for instance, lengthen the construction phase of the project to distribute construction emissions over a longer period of time (more years, lower emissions per year). EPA notes that redesigning the planning, if not done before the draft General Conformity Determination is published, may require the preparation of a supplemental NEPA document because other NEPA environmental categories could be affected.

2.3.2 Mitigation and emissions offsets

Under § 93.152, the federal agency can apply mitigation measures to avoid or reduce all or a portion of the annual net increase of emissions that equal or exceed de minimis for the purpose of demonstrating conformity. In addition, emissions offsets can be obtained to compensate for a net emissions increase. Either way, the entire increase in net emissions for the year where emissions increases equal or exceed de minimis must be accounted for, as it is not enough to reduce, avoid, or compensate for net emissions increases just to the point where the increases are below the appropriate de minimis rate. For either mitigation or emissions offsets, the follow apply:

The federal agency must show that there are adequate resources to implement the mitigation measures or offset plans;
The federal agency may use either, or both strategies, for the purpose of meeting the conformity requirement under CAA § 176(c)(1)(A) and (1)(B);
After the application of mitigation or use of offsets, the net increase in emissions for the year must be zero;
Emissions reductions or offsets must occur during the same calendar year in which the activities' emissions causing the need for mitigation or offsets occur; and
An agency's plan to mitigate or offset emissions requires the reduction or offsets to be more than equal to the annual increase in net emissions caused by taking the action, depending on the area's classification (e.g., ozone Serious nonattainment area or a PM2.5 Moderate nonattainment area) as required under section 93.163 Timing of offsets and mitigation measures. For example -- If a project's activities would cause 150 tons of NOx emissions, per year, for 3 years, in a Serious ozone nonattainment area, that would be 450 tons of NOx emissions over the 3 years. For a Serious ozone nonattainment area, that would require 1.2 tons of reduced NOx emissions for every ton of new NOx caused by the project over the three years. The calculation is 450 tons NOx multiplied by 1.2 tons = 540 tons that need to be reduced. The mitigation or offsets must cause a reduction of 540 tons over a maximum of 6 years (3 x 2 = 6 years or twice the number of years needing the reduction to meet conformity.) Therefore, mitigation or offsets must provide 6 years of reductions of 90 tons of NOx per year to meet the requirements under section 93.163, because 540 tons / 6 years = 90 tons per year for 6 years.
Agreements to apply mitigation measures and plans for obtaining emissions offsets must be in place before the federal agency can rely on them demonstrate conformity and make its positive conformity determination; and
EPA, States, Tribes, and local agencies must be able to enforce the requirements of the mitigating emission reduction strategies or techniques used as an offset.
Mitigation measures:
1. Mitigation measures can be modified after the federal agency has completed its conformity demonstration by following the procedures under § 93.160(e); and
2. A written agreement to commit to mitigation measures needed to demonstrate conformity must be fulfilled by all parties that signed the agreement. Therefore, any written agreement must be signed and a copy included in the agency's conformity determination. All parties to the agreement must meet their obligations under the agreement. 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.

Emissions offsets must be:
1. Quantifiable – The federal agency must be able to quantify the emissions being offset using standard techniques or strategies;
2. Surplus – The offsets must not be required by the applicable implementation plan, or other environmental laws or regulations;
3. Enforceable – EPA or the State, Tribal, or local agency must have the ability to enforce the offsets. This can be done by including the measure in an operating permit or similar mechanism or by including the reductions in the applicable implementation plan; and,
4. Permanent – The offsets must be permanent within the timeframe the emission increases caused by the activities occur.

2.3.3 Demonstrating conformity in the absence of an approved AIP

A federal agency may propose activities within a nonattainment area or maintenance area where EPA has not approved an AIP for the area. In such case, the federal agency’s options for demonstrating conformity for its activities are limited. Since there is no AIP, the federal agency can secure a commitment from the state or Tribe to include the emissions into a future AIP. 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 an AIP occurs when the emissions from a federal activity will occur after the time period covered by the AIP. In this case, the federal agency can demonstrate conformity for the last budget in the AIP and assume that the future AIP will allow at least that quantity of emissions. The State, Tribal or local air agency would be responsible for developing the AIP to account for the emissions from the activities. If the emissions from the activities are greater than the emissions allowed in the last budget in the AIP, then the federal agency can secure a commitment from the State or Tribe to include the emission in a future AIP.

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, except when applying air quality modeling when all years required under § 93.159(d) must be evaluated. Under the worst-case approach, the federal agency would show that the year of maximum emissions from the activities would conform with the most stringent budget in the AIP. Under the year-to-year approach, the federal agency would demonstrate that each year the net emissions for the activities would conform with the AIP. The year-to-year approach may be useful for activities with specific end dates or with widely varying emissions such as construction projects.