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By MIKE LEE
The Fort Worth Star-Telegram

State environmental officials say that an ÃÛÌÒ½´researcher was correct: Gas drilling in the Barnett Shale contributes about as much air pollution to the Dallas-Fort Worth area as car and truck traffic.

But the Texas Commission on Environmental Quality doesn’t plan on taking any action about chemicals released during gas drilling because they typically happen in rural areas, not in the immediate metro area, where the EPA is forcing state and local governments to control air pollution.

And it’s more efficient to tackle the Metroplex’s air problem by going after other sources of pollution, such as cars and trucks, Andrea Morrow, a spokeswoman for the environmental commission, said via e-mail.

Al Armendariz, an engineering professor at ÃÛÌÒ½´Methodist University, published a study in February about the amount of air pollution released by Barnett Shale gas drilling. Industry groups attacked the study as biased, so Armendariz recalculated the numbers using data the commission collected.

"The estimates Dr. Armendariz provides for individual source categories are comparable to the TCEQ estimates," Morrow said. But, "Most of the Barnett Shale area is currently in attainment for the ozone standard, and the TCEQ cannot selectively regulate certain industries in these counties."

Armendariz estimated that, in the nine-county Metroplex area, gas drilling produced about 112 tons per day of pollution, compared with 120 tons per day from vehicle traffic. In a 20-county area, including rural counties, he estimated that gas drilling produced 191 tons per day.

The pollution comes from a couple of major sources. The tank batteries used to store wastewater and condensate, which is a light form of crude oil, often vent to the atmosphere. The motors used to drive pipeline compressors often have no pollution controls. And drillers frequently vent natural gas to the atmosphere when they complete a well.

The commission’s numbers come within 25 percent of Armendariz’s original calculations: 90 tons per day in the nine-county area, 200 per day in the larger area. The calculations "appear reasonable," Morrow said.

Where the commission differs is how to fix the pollution. The area is under orders from the Environmental Protection Agency to reduce the amount of ground-level ozone. Levels have been falling, but the area is still above the federal standard, Morrow said.

There are two primary ingredients to ozone: Volatile organic compounds, like the petroleum vapors that leak from the storage tanks in the Barnett Shale, and nitrous oxides, which are released by car exhausts and other sources.

The commission believes it’s easier to address ozone by reducing the amount of nitrous oxides. The easiest way to do that is to reduce pollution from cars and trucks. The volatile organic compounds can be toxic, but they’re harder to control, Morrow said.

Also, she said, "The biggest gas-producing counties in the Barnett Shale are contiguous to D-FW. However, the prevailing winds in the D-FW area are such that emissions from the Barnett Shale are carried away from the D-FW area."

Armendariz and the Environmental Defense Fund, which paid for his study, suggested using available technology to reduce the pollution released at gas-related sites: Vapor-control systems on tank batteries and "green completions" to prevent gas from being released when a well is being connected to pipelines.

A bill to require green completions in the Barnett Shale died in the recent legislative session. Still, Armendariz said he was hopeful. "It is clear that in the future, state and federal regulators will have a more accurate picture of the true magnitude of emissions from the oil/gas sector in this part of Texas," he said. "I hope the industry realizes that the days of venting methane and hydrocarbons to the atmosphere are probably numbered."

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