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EPA Proposes to Reclassify DM/NFR Area to “Serious” Nonattainment for 75 ppb Ozone Standard

Published: August 9, 2019

The U.S. Environmental Protection Agency (EPA) is proposing to determine that the Denver Metro/North Front Range ozone nonattainment area did not meet the 2008 National Ambient Air Quality Standard (NAAQS) (i.e. 75  parts per billion (ppb)) by the specified deadline of July 20, 2018 and should be reclassified from a Moderate to a Serious nonattainment area.

The proposed rule aligns the DM/NFR State Implementation Plan (SIP) deadlines with the rest of the Serious Areas with an attainment deadline of July 20, 2021 (based on three-year average of 2018-2020 ozone season data).

Because of Colorado’s specific requirements that SIPs go through legislative review, the earliest a Serious SIP will be able to be submitted to EPA is February 2021.  The RAQC has already begun development of this SIP and this rulemaking does not impact the timing of our planning efforts.

EPA will be accepting public comment on the proposed action for a 30-day period beginning on August 15 and will hold a public hearing on September 6 at 9:00am at the Agency’s Region 8 office (1595 Wynkoop St., Denver, CO 80202).

For more details on EPA’s proposed action visit:

For current ozone monitoring reports visit: