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Air Quality

Air Quality Conformity

As the region's planning agency for transportation, SANDAG is required to demonstrate that transportation projects that receive state and federal funding will not adversely affect the region's air quality standards.

The Clean Air Act, which was last amended in 1990, requires the U.S. Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for pollutants considered harmful to public health and the environment. The Clean Air Act defines a 'nonattainment area' as a region where air pollution levels persistently exceed the NAAQS. The EPA requires that each state containing nonattainment areas develop plans for reaching attainment. These plans are called State Implementation Plans (SIP).

The Clean Air Act requires federally supported transportation activities to be consistent with the SIP. This requirement is referred to as transportation conformity. Conformity is to ensure that new transportation projects do not jeopardize air quality in nonattainment areas.

Conformity also is a way to ensure that federal funding and approval are given to those transportation activities that are consistent with air quality goals. Projects cannot be approved, funded, advanced through the planning process, or implemented unless those projects meet air quality standards.

SANDAG must demonstrate that the Regional Transportation Plan (RTP) and the Regional Transportation Improvement Program (RTIP) are in conformity with the SIP for meeting air quality standards.

On July 20, 2012, the U.S. EPA designated the San Diego air basin as a non-attainment area for the 2008 Eight-Hour Ozone Standard and classified it as a marginal area with an attainment date of December 31, 2015. SANDAG determined conformity to the new standard on May 24, 2013, using the model approved by U.S. EPA to forecast regional emissions (EMFAC2011). The U.S. DOT, in consultation with the U.S. EPA, made its conformity finding on June 28, 2013.  

Effective June 3, 2016, the U.S. EPA determined that 11 areas, including the San Diego air basin, failed to attain the 2008 ozone NAAQS by the applicable attainment date of July 20, 2015, and thus are reclassified by operation of law as “Moderate” for the 2008 ozone NAAQS. The San Diego Air Pollution Control District submitted a SIP revision addressing Moderate area requirements to CARB on December 27, 2016. Effective December 4, 2017, the U.S. EPA found the motor vehicle emissions budgets for the Reasonable Further Progress milestone year of 2017 from the 2008 Eight-Hour Ozone Attainment Plan for San Diego County adequate for transportation conformity purposes for the 2008 ozone NAAQS.

On October 26, 2015, the U.S. EPA announced a revised and stricter ozone standard, referred to as the 2015 Ozone standard. On June 4, 2018, U.S. EPA published a final rule designating the SANDAG region as nonattainment, with a classification of Moderate, for the 2015 ozone NAAQS with an attainment deadline of August 3, 2024, and an attainment year of 2023, effective August 3, 2018.

On May 24, 2019, the SANDAG Board of Directors adopted the 2015 Ozone National Ambient Air Quality Standard Conformity Demonstration for San Diego Forward: The Regional Plan (2015 Regional Plan) and the 2018 RTIP. The conformity demonstration found the 2015 Regional Plan and 2018 RTIP, as amended, in conformity with the requirements of the federal Clean Air Act and applicable SIP. The U.S. DOT, in consultation with U.S. EPA, made its conformity determination on June 21, 2019, indicating that all air quality conformity requirements have been met, including those for the 2015 ozone standard.

On September 28, 2018, the SANDAG Board of Directors adopted the final 2018 RTIP (see Chapter 5 and Appendices E and F) and its conformity determination and redetermination of conformity for San Diego Forward: The Regional Plan. The U.S. DOT, in consultation with U.S. EPA made its conformity determination on December 17, 2018.

On October 25, 2019, the SANDAG Board of Directors adopted the air quality conformity determination finding that San Diego Forward: The 2019 Federal Regional Transportation Plan (Appendix B) is in conformance with the SIP for air quality and adopted the 2019 Federal RTP and its supporting analyses. On this same date, the Board also adopted Resolution No. RTC-2020-03, approving Amendment No. 8 to the 2018 RTIP. U.S. DOT, in consultation with U.S. EPA, issued its conformity finding for the 2019 Federal RTP and 2018 RTIP, through Amendment No. 8, on November 15, 2019.

Project Manager

Rachel Kennedy, Senior Regional Planner
Phone: (619) 699-1929, Email:

For media inquiries, please contact the SANDAG Public Information Office at (619) 699-1950 or