State predicts air will improve

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TCEQ models for area rely on cleaner cars burning cleaner gas

The Texas Commission on Environmental Quality has predicted a dramatic drop in North Texas ozone levels over the next three years, according to a preliminary model of air quality from now through 2018.

But will it happen? The agency doesn’t have a good track record with predictions.

Three years ago, the agency predicted a similar dramatic drop in the eight-hour ozone average for North Texas, and agency officials acknowledged they were wrong during a presentation earlier this month to the North Texas Clean Air Steering Committee. At the time, new modeling software showed that cars built to cleaner federal standards were expected to make a big difference for North Texas air.

It had taken a decade for ozone averages at the Denton Enterprise Airport monitor to drop from about 97 parts per billion to 87 ppb, yet the agency had predicted that between 2010 and 2013 the averages would drop another 10 ppb.

And even though the Denton monitor now sits at 87 ppb — essentially where the eight-hour average has hovered for the past five years — the state agency is again predicting that the region’s ozone levels will drop to about 76 ppb by 2018.

This time, state environmental officials are hanging their hats on a new federal gasoline standard, which the Environmental Protection Agency plans to phase in beginning in 2017.

TCEQ staff member Chris Kite, who presented the latest prediction, said that the high readings at Denton’s monitor were driving the state’s model. He also said that increased ozone averages from 2011 were an aberration because of the drought.

North Texas has not been able to meet the eight-hour standard for ozone since it was set in 1997. Now, state environmental officials must write and submit to federal officials a new plan to meet a far stricter standard, 75 ppb, for 10 North Texas counties, including Wise County, which was added this year.

The model’s final prediction, expected early next year, is a key step in writing the cleanup plan. The model combines known emissions from traffic and industry with weather data to forecast future ozone levels.

A few committee members questioned the model’s assumptions for industry emissions, which used the maximum amounts permitted from many factories, but not from some oil and gas equipment, such as compressors. Instead, the agency calculates a blanket amount of emissions from smaller oil and gas production facilities based on production data from the Texas Railroad Commission, Kite said.

Since 2003, about 15,000 oil and gas wells have been drilled in the Barnett Shale area, for a total of 17,332 wells as of October, according to commission records.

Should the model show that the region cannot meet the new standard with current control measures — including the new cleaner cars burning cleaner gas — then state environmental officials, with the help of the steering committee, must come up with additional strategies.

Chris Klaus, senior planner with the North Central Texas Council of Governments, which is home to the steering committee, reminded the group that for each 1 ppb of ozone above the new standard, the region must find enough local control measures to reduce about 20 tons per day of nitrogen oxides.

Ground-level ozone is made when volatile organic compounds, or VOCs, and nitrogen oxides, or NOx, combine in sunlight. In North Texas, most ozone tends to form in the warmer months during hot, dry weather when the winds stagnate, Kite said.

For many years, state environmental officials have focused on strategies that reduce NOx, rather than VOCs. NOx comes from vehicle and factory combustion. VOCs can come from human activity, such as emissions from oil and gas operations or from plants.

However, Neelesh Sule, a University of Texas at Arlington graduate with the Dallas engineering firm Conestoga-Rovers and Associates, told the committee that ozone formation is dynamic and depends on time and place, too. He made a different recommendation.

Using data from past ozone seasons, he and UTA professors Victoria Chen and Melanie Sattler tested strategies and found that reducing NOx from certain sources at certain times of day would help. But they also found that reducing VOCs in Denton, Ellis and Kaufman counties would also be effective.

In mid-October, the World Health Organization declared air pollution a human carcinogen, after a panel of experts reviewed thousands of scientific papers. Spending the day outdoors doing intermittent work in ozone at 60-70 ppb can cause injury to lung tissue and other health effects, according to the Environmental Protection Agency.

PEGGY HEINKEL-WOLFE can be reached at 940-566-6881 and via Twitter at @phwolfeDRC.

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