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The EPA regulates ground level ozone based on the three-year average of the fourth-highest eight-hour average ozone concentration at regulatory monitoring sites within the region. This is referred to as the area’s design value.
Early Action Compact and Nonattainment
On April 15, 2004, the EPA designated Bexar, Comal and Guadalupe Counties in violation, or "nonattainment", of the eight-hour ozone standard. That standard was set at 85 parts per billion (ppb).
The area entered into an Early Action Compact (EAC) with the EPA that deferred nonattainment status for three years. As part of the EAC, the EPA would designate the area in attainment for ozone if the area’s air quality could comply with the 80 ppb ozone NAAQS during the 2005-2007 monitoring period. The area succeeded in the EAC, and, in 2008, the EPA proposed and ultimately designated the Alamo Area in attainment.
In late 2008, the EPA set a new ozone standard of 75 parts per billion (ppb). The Alamo Area violated this standard by 2012. With a new ozone NAAQS due in 2015, though, the EPA refrained from designating areas newly in violation of the outgoing standard.
While declining since 2012, ozone levels in the Alamo Area have not met the most recent ozone NAAQS set in 2015 of 70 ppb. In 2018, the EPA designated Bexar County as marginal nonattainment, effective September 24, 2018. Under this marginal classification, the area has until September 24, 2021 to attain the 2015 ozone NAAQS.
Bexar County Design Value (2000-2018)
Air Monitoring Stations
The EPA monitors air pollution around the country through a nationwide network of monitors. When a monitor detects smog in violation of federal standards, it is posted on the AirNow.gov website.
The Texas Commission on Environmental Quality (TCEQ) manages several Continuous Air Quality Monitoring Systems (CAMS) that record pollutant levels daily within the Alamo Area MPO study area. Three of the CAMS are regulatory monitors used by the EPA for the area’s attainment of air quality standards. These are: San Antonio Northwest (C23), Camp Bullis (C58) and Calaveras Lake (C59).
For More Information:
Allison Blazosky, AICP
Regional Transportation Planner