New “Serious” Classification for Nonattainment For Ozone

On December 16, 2019, the U.S. Environmental Protection Agency (EPA) announced a final rule to reclassify the Denver Metro/North Front Range ozone nonattainment area from Moderate to Serious nonattainment under the Clean Air Act. The area covered embraces all of Adams, Arapahoe, Boulder, Denver, Douglas, and Jefferson counties as well as the southern portions of Larimer and Weld counties.

Under the Clean Air Act, areas that do not attain national ozone standards in a timely manner are reclassified to a higher nonattainment status. The DenverMetro/North Front Range area has been classified as a Moderate nonattainment area for the 2008 ozone 8-hour National Ambient Air Quality Standard since 2016. The reclassification to Serious is based on an evaluation of air quality data collected between 2015 and 2017.

Colorado must now revise its State Implementation Plan (SIP) for ozone with enforceable rules and programs to achieve compliance with the national air quality standard for ozone including a lower threshold for permitting large sources. Colorado has until July 20, 2021 for the affected area to attain the 2008 ozone standard.

Link for details on EPA’s action: https://www.epa.gov/ground-level-ozone-pollution/2008-ozone-national-ambient-air-quality-standards-naaqs-nonattainment

Link to map of the Denver Metro/North Front Range nonattainment area: https://www3.epa.gov/airquality/greenbook/co8_2008.html