Ozone Season Ends with Positive News

At the end of the season, be it ground-level ozone or sports, there are certain stats everyone talks about. For air quality planners, those numbers are the Design Value and 4th Highest Eight-Hour Average. The 2013 ozone season (April-October) saw the lowest eight-hour averages, and produced the lowest Design Value, the region has monitored in over 15 years.

Design Value is the number U.S. Environmental Protection Agency (EPA) uses to determine a region’s compliance with federal ozone standards. It is the rolling, three-year average of the fourth-highest day of ozone readings (as averaged over eight consecutive hours) at a single monitor.
The three-year/fourth-highest calculation is done annually for each of the region’s regulatory monitors. (There are two regulatory monitors in the CAMPO region, located at Murchison Middle School and at the Austin Audubon tract.) The monitor with the higher average sets the Design Value for that year. In 2013, the Audubon monitor provided the Design Value; in other years Murchison has had the higher readings.

EPA currently requires a Design Value of no higher than 75 parts per billion (ppb) to remain in attainment of the ozone standard.

AQ Table

With 4th-high readings of 69 ppb and 70 ppb, and a Design Value of 73 ppb, the region’s 2013 ozone season was outstanding. The region is clearly monitoring compliance; however, EPA is reviewing the 75 ppb standard and is expected to set a more stringent standard of between 60 ppb and 70 ppb within the next several years.

The region has been proactively engaged in air quality improvement since 2002, when it adopted the first in a series of voluntary ozone reduction plans in collaboration with EPA. The fourth such plan, Ozone Advance, is scheduled to be in place by the end of 2013.

AQ graph

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