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Understanding General Conformity in Texas

Information about the EPA's General Conformity regulation and how it affects projects inTexas.

What is General Conformity?

Pursuant to the Federal Clean Air Act, the general conformity rule as codified in 40 Code of Federal Regulations Part 51 Subpart W and 40 Code of Federal Regulations Part 93 Subpart B was created to ensure that actions by the federal government will neither cause nor aggravate a violation in air quality standards, nor delay timely attainment of standards. In other words, general conformity aims to prevent federal projects from jeopardizing a state’s ability to achieve air quality standards. The federal general conformity rules required states to adopt and submit a general-conformity State Implementation Plan not later than November 30, 1994.

De Minimis Levels in Texas

The federal general conformity rules establish de minimis, or maximum, emissions levels in tons per year (tpy) based on the severity of an area’s air quality problem. These levels for nonattainment areas in Texas are identified in the following tables. If air emissions from a proposed federal action are anticipated to be below de minimis levels, then the project may proceed. If, on the other hand, emissions are expected to exceed the de minimis levels, a general-conformity determination must be made by the federal agency involved.

De minimis levels for Texas’ ozone nonattainment and maintenance areas

Area Classification VOC tpy NOx tpy
El Paso County Maintenance 100 100
Dallas–Fort Worth Nonattainment Area Moderate  100 100
Houston-Galveston-Brazoria Nonattainment Area Marginal  100 100


De minimis levels for Texas’ carbon monoxide nonattainment area

Area Classification CO tpy
El Paso County (portion) Maintenance 100


De minimis levels for Texas’ lead nonattainment area

Area Classification Lead tpy
Collin County (portion) Nonattainment 25


De minimis levels for Texas’ PM10 nonattainment area

Area Classification PM10 tpy
El Paso County (portion) Moderate 100


In quantifying the emissions associated with a project, both direct and indirect emissions are included. Only emissions within the scope of the federal agency’s authority are included. For example, a federal military facility expansion would be paid for and operated with federal money with every aspect of the project under the control of the Department of Defense. Direct emissions such as construction activities are included, as well as indirect emissions such as on-site emissions from the vehicles of military personnel associated with the facility.

Demonstrating Conformity

If emissions exceed de minimis levels, some options for demonstrating conformity include, but are not limited to;

  • identifying and accounting for the emissions in the latest EPA-approved state implementation plan (SIP),
  • providing written assurance from the state that it will revise the SIP to include the project’s emissions, and
  • offsetting emissions exceeding de minimis levels through a SIP revision, purchase of emission reduction credits, use of cleaner equipment, or by some other approved means.


Related Web pages and publications

EPA General Conformity Web page Exit the TCEQ


Contact Us

Jamie Zech, Ph.D
Air Quality Division, TCEQ
Phone: 512-239-3935