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news_2012_08_13

Austin Measures Highest 8-Hour Ozone Average since 2003, Is One Day Away from Violating Ozone Standard

On Saturday, August 11th, the ozone monitor at Murchison Middle School (CAMS 3) measured an 8-hour ozone average of 94 parts per billion (ppb). Elevated ozone was also measured at other ozone monitors in the Austin on the same day, but none nearly as high as at the Murchison Middle School:

  • Austin Audubon Society (Travis County): 80 ppb
  • Dripping Springs Elementary School (Hays County): 73 ppb
  • Lake Georgetown (Williamson County): 73 ppb
  • Hutto (Williamson County): 69 ppb
  • McKinney Roughs Nature Park (Bastrop County): 66 ppb
  • San Marcos (Hays County): 61 ppb

High ozone levels were also measured to the north of the Austin area, with monitors in Killeen and Waco both measuring 87 ppb 8-hour ozone averages, and winds appeared to be coming from the north during this day.

Here are the monitoring parameters measured at CAMS 3 for that day:

Monitoring Measurements at CAMS 3 for 8/11/2012

With this high ozone day, the Austin area is now one high ozone day away from violating the 2008 ozone National Ambient Air Quality Standard of 75 ppb. If the Murchison Middle School measures another 8-hour ozone average of 79 ppb or higher before the end of the ozone season, it will put the Austin area's 2012 ozone "design value" above the standard, putting the area at risk for being designated nonattainment for ozone.

The "design value" for a monitor is calculated by taking an average of the 4th highest daily 8-hour ozone averages over a 3-year period. Here is an example of how this statistic is calculated:

Day 2009 2010 2011 2012
Highest 80 77 82 94
2nd Highest 77 76 79 87
3rd Highest 77 75 78 80
4th Highest 76 74 75 74

2011 Design Value = Average (2009 4th Highest, 2010 4th Highest, 2011 4th Highest) = (76+74+75)/3 = 75

2012 Design Value as of 8/13/12 = (2010 4th Highest, 2011 4th Highest, 2012 4th Highest) = (74+75+74)/3 = 74 (fractions of 1 ppb are truncated)

2012 Design Value if CAMS 3 Measures a day of 79 ppb in 2012 = (74+75+79)/3 = 76 ppb