Texas environmental regulators are asking natural gas producers that operate in the Barnett Shale to voluntarily reduce air pollution emissions at drilling sites before they consider more stringent permitting rules.
Most gas wells that are drilled produce condensate, which is collected in tanks with other drilling waste. The amount of condensate from drilling locations varies, but the wastewater at some sites across the Barnett Shale's 17-county region has been found to contain several volatile organic compounds (VOC), including benzene, according to the Texas Commission on Environmental Quality (TCEQ).
In August and again in October the TCEQ used infrared cameras to monitor well sites in the North Texas region to collect ambient air data. According to preliminary reports, hydrocarbon vapors were emitted from the hatches and valves on storage tanks and from vents on compressor stations. The benzene levels were discovered as part of the larger emissions study.
According to the TCEQ, air samples indicated "alarming" levels of benzene at several locations. One sample taken downwind from a tank seven miles west of DISH, TX, showed a benzene level of 1,000 parts per billion (ppb), which is more than five times the TCEQ's short-term exposure limit of 180 ppb (see related story). The 1,000 ppb level, according to the commission, is the equivalent of a person sniffing a gallon of gasoline. A sample at another site found benzene levels measuring 500 ppb.
The TCEQ summary stated that it "is possible that adverse health effects could occur from exposure to this concentration of benzene," and the commission's toxicology division "strongly recommends additional sampling in the area."
Michael Honeycutt, who heads TCEQ's toxicology department, said the commission is continuing to collect ambient air data in the region, including Tarrant, Wise, Denton, Parker and Johnson counties, where gas drilling is under way. The TCEQ is unsure if the level "is one out of every two facilities, one out of every 100 or one out of every 1,000." In any case, more testing needs to be performed, it said. The commission is planning to complete the emissions study in January.
What happens after the data is compiled is unclear but "everything is on the table." Permitted gas drilling sites in Texas don't ordinarily set benzene emission levels, and some industry members have discounted suggestions that gas drilling and air pollution are linked in the Barnett Shale area.
"We cannot speak for other operators, but the wells and production equipment that Chesapeake Energy has in the Barnett Shale -- specifically in Johnson and Tarrant counties -- do not have VOC emissions," Chesapeake Energy Vice President Julie Wilson wrote in an e-mail to Fort Worth City Council members on Oct. 14, 2008. "The gas in the Barnett is lean, meaning it is 95 to 96% methane gas (very clean), so it does not contain the liquid hydrocarbons that produce the VOC emissions."
Operators could prevent the state from stepping in and imposing more stringent permitting limits if they were to address the problem under a "find and fix" program by voluntarily reducing high VOC emissions from their drilling sites, said Honeycutt. Otherwise, state regulators may impose stricter permit limits to lower benzene emissions from the area, he said.
"To some people, it's not a good solution, but we get the reductions faster," he said of the revised permitting process.
It could take the TCEQ up to five years before the permits for gas wells were revised, he noted.
Texas state Sen. Wendy R. Davis, who represents Fort Worth, TX, has asked Lt. Gov. David Dewhurst to call for a special Senate investigation of drilling operations in the Barnett Shale (see NGI, Nov. 9). Davis also has asked industry representatives and the commission to work together to come up with a plan to address the Barnett Shale's air pollution. Without a plan, Davis suggested that she could push for legislation when state lawmakers meet again to speed up the TCEQ's rulemaking process.
"I'm hopeful we're going to have the companies come through and do what's asked of them," Davis said.
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