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Update on Revisions to State Implementation Plans for the South Coast Air Basin and Coachella Valley

Air quality in the South Coast AQMD region has improved significantly over the last several decades due to the rules and programs implemented by South Coast AQMD. However, more work needs to be done to meet federal air quality standards. South Coast AQMD has recently developed revisions to State Implementation Plans (SIP) to address fine particulate matter (PM2.5) in the South Coast Air Basin (Basin) and ozone in the Coachella Valley. In both cases, the areas are very close to meeting these standards.

Despite significant reductions in PM2.5 levels, the South Coast Air Basin did not meet the 2006 24-hour PM2.5 standard (35 µg/m3) by the required date of December 31, 2019. Specifically, the PM2.5 levels in two monitoring stations in Compton and Mira Loma exceeded the standard by the end of 2019. According to the new PM2.5 plan, the Basin is expected to meet this standard by 2023 based on the continued implementation of existing regulations and programs which will result in significant emission reductions over the next few years.

The Coachella Valley experienced unusually high ozone levels in 2017 and 2018, largely due to higher than normal temperatures and stagnant weather conditions. As a result, the Coachella Valley failed to meet the 1997 8-hour ozone standard (0.08 ppm) by the 2019 attainment deadline. Like the South Coast PM2.5 plan, the Coachella Valley ozone plan projects that the area will meet this standard in or before 2023 based on emission reductions from existing regulations and programs.

On December 4, 2020 the South Coast AQMD’s Governing Board approved the revisions to the SIP plans and submittal to CARB and subsequently to the U.S. Environmental Protection Agency for approval. 

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