The latest health-effects analysis of Barnett Shale air by state environmental officials is the first to underscore similarities of toxic compounds inspectors continue to find at elevated levels around natural gas facilities.

The analysis, written May 25 and released June 4, is the fifth such analysis released by the Texas Commission on Environmental Quality since October. It examines new findings by inspectors and the long-term risks those toxic compounds could present. Inspectors have been going back, officials said, and retesting emissions at several natural gas production sites since they first tested last fall — and released those detailed results in 300-page report in January.

Among those compression plants in Denton, Hood, Parker and Wise counties that inspectors sampled again in March, the highest benzene concentration, 37 parts per billion, was detected at a Devon Energy complex on Jim Baker Road between Justin and Dish.

The Jim Baker Road site was the only Denton County facility included in the analysis.

The highest benzene reading overall, 95 ppb, was detected at a Stallion Oilfield Services commercial disposal well in Parker County.

All six facilities that state inspectors revisited are within about 1,000 feet from people’s homes.

Although benzene was not the only toxic compound found at the facilities, benzene is a known carcinogen. According to the Environmental Protection Agency’s hazard summary for benzene, continuously breathing air with an average of 0.4 ppb of benzene increases cancer risk to 1 in 100,000 over a lifetime.

Through its National-Scale Air Toxics Assessment program in 2008, the EPA set a target for cancer risk of 1 in 1 million people. Long-term, benzene levels at 0.04 ppb present the 1-in-a-million risk.

The EPA website defines a risk level of 1 in a million as the likelihood that up to one person, out of 1 million equally exposed people, would contract cancer if exposed continuously to the specific concentration over a lifetime.

The EPA does not require entities meet those risk targets with the Clean Air Act. The federal legislation only requires emissions monitoring at the source, according to Ruben Casso, EPA air toxics coordinator for Region 6.

The toxicology division at TCEQ set a threshold for long-term, or lifetime, exposure in Texas at 1.4 ppb for benzene. The EPA does not require states to do as Texas and others have, setting a long-term threshold for airborne toxic compounds such as benzene, Casso said.

“They are going above and beyond with that requirement,” he said of the state’s long-term threshold.

Devon Energy spokesman Chip Minty said state inspectors found a faulty valve before company inspectors did. The company fixed the problem right away, he said. 

Robert J. Ryan, deputy general counsel for Houston-based Stallion Oilfield Holdings Inc., said in an e-mail that the company is cooperating with TCEQ in its continuing investigations, adding that the company has been “issued a TCEQ air authorization, under permit by rule, with which we are in compliance.”

A “permit by rule” allows a company to calculate its own emissions and claim that they will not exceed certain criteria. Once the TCEQ accepts the claim, the company pays a fee for the permit to operate.

Reporting exemptions

Among those facilities required to report their toxic releases to the EPA’s Toxics Release Inventory, Texas facilities reported releasing more benzene in 2008 than any state in the nation, about 1.9 million pounds to the air, soil and water.

Facilities in Louisiana reported the second highest amount, about 500,000 pounds of benzene.

Because operating permits for nearly all Barnett Shale facilities are “permits by rule,” they do not require those companies to report their releases of benzene and other toxic compounds to the federal inventory.

Of the 15 Denton County facilities that reported to the toxics inventory in 2008, the latest year data are available, none were associated with either natural gas extraction or production.

TCEQ is compiling its first-ever inventory of permanent equipment in the Barnett Shale and expects to release the information in July, according to spokesman Terry Clawson.

Devon Energy alone has 80 compression stations in the Barnett Shale region, Minty said.

In all, there are nearly 14,000 wells in the Barnett Shale, according to the latest data released by the Texas Railroad Commission. More than 3,000 well locations have been permitted but not yet drilled. 

Devon site samples

TCEQ inspectors took several samples at Devon’s site on Jim Baker Road last fall and returned twice this spring.

On Oct. 14, inspectors detected elevated levels of benzene, at 46 ppb, and carbon disulfide, a neurotoxin, at 6.2 ppb. The amounts did not pose a threat to short-term health but raised concerns about potential long-term exposure, according to a TCEQ report.

Devon repaired the valve, which was found to be leaking, Minty said. Inspectors returned in November and found benzene at 3.7 ppb, but no carbon disulfide.

In March, state inspectors returned to collect upwind and downwind samples.

Upwind, the inspectors measured benzene at 0.14 ppb in one sample. Downwind, one sample was almost 59 times higher, at 8.2 ppb; the other was 264 times higher, at 37 ppb.

After TCEQ reported those findings to Devon, the company repaired another valve, Minty said.

Inspectors returned again in May and gathered a downwind sample, detecting benzene at 12 ppb.

A Devon employee visits every compression site every day of the week, Minty said, because problems with equipment can occur at any time, even overnight.

“In this particular case, TCEQ discovered it before we did,” Minty said. “We responded quickly, as we always do.

“It’s important to keep perspective between companies that are responsive and to circumstances that are chronic and of public concern,” he added.

The May 25 analysis

In this latest analysis from the TCEQ, toxicologists looked at follow-up samples taken by state inspectors March 1 through 5. Inspectors found “concentrations at these facilities [one commercial disposal and five compression plants in Denton, Hood, Parker and Wise counties] were similar to concentrations detected during previous sampling events in 2009,” according to the analysis.

Facilities in Hood and Parker counties also were found emitting a host of other toxic compounds, including toluene and xylene, both neurotoxins. According to the state’s analysis, levels were elevated for the short-term, but not high enough to be expected to cause immediate health effects.

However, the Hood and Parker county facilities were referred to TCEQ’s enforcement division for emitting above odor thresholds, which can cause people to have headaches and nausea.

In addition, TCEQ toxicologists recommended that monitoring continue in the Barnett Shale for long-term health risks.

The agency released a 300-page report in January, which showed that toxicologists found some emissions at nearly every Barnett Shale facility they checked last year. Tony Walker, regional director for TCEQ Region 4, said inspectors are revisiting facilities with elevated emission levels during the agency’s large-scale study of Barnett Shale facilities last fall.

“We’re working with our toxicology division to determine what the next steps will be,” Walker said.

More inspections

Walker e-mailed the May 25 analysis to Denton County Judge Mary Horn along with a chart of results from yet another inspection last month. Inspectors went back to those six facilities (one commercial disposal and five compression plants in Denton, Hood, Parker and Wise counties), including the Devon facility, and collected more samples from May 4 through 19.

The latest round of inspections again showed elevated benzene levels as found in two or more previous inspections, including the finding at the Devon facility on Jim Baker Road.

Horn said she appreciated the notification, which was a first for her office, and the level of information provided.

“People have so many questions here, and they [TCEQ] didn’t get on it as quickly as many wanted them to,” Horn said. 

Residents have complained about the Devon facility on Jim Baker Road as early as 2003.

Neither short-term samples, obtained in a day or less, nor ambient air monitoring, which continually measures certain pollutants from a fixed position, gets all the information needed, Horn said.

“It all has to be looked at,” she said.

With the additional study, however, TCEQ is closer to meeting its needs for long-term data, Walker said.

“It’s more complex gathering short-term data to make long-term decisions,” he said.

Dish complex samples

Farther north of the Devon facility, the compression complex and treatment plants in Dish were part of TCEQ’s original study, where inspectors measured benzene at 1.6 ppb on Nov. 18. Inspectors also returned to Dish on March 4. A 30-minute, downwind sample found benzene at 0.31 ppb.

The TCEQ installed its permanent, ambient air monitor in Dish in April. Inspectors did not go back to take samples in Dish in May.

Dish Mayor Calvin Tillman said he was not surprised that pollution levels could be improving in his community. He took representatives from the Heinz Endowments — a Pennsylvania-based organization that gives grants to environmental causes — on a recent tour of Barnett Shale facilities, something he has not done himself in a long time. Tillman noted that facilities in his community appeared in better shape than facilities the group saw elsewhere in Denton and Wise counties, particularly along State Highway 114.

“Frankly, as the result of our fussing, such as where a relief valve might go, I know it [the valve] sometimes ends up on the other end of the line and in someone else’s backyard,” Tillman said. “That’s a double-edged sword, and it really sucks.”

PEGGY HEINKEL-WOLFE can be reached at 940-566-6881. Her e-mail address is pheinkel-wolfe@dentonrc.com.

BENZENE BY THE NUMBERS

Here is a look at the cancer risk associated with benzene exposure compared with the recent levels state environmental officials have reported at a compression facility in Denton County since October.

Texas’ lifetime exposure threshold: 1.4 parts per billion

Level for lifetime cancer risk of 1 per 1 million: 0.04 ppb

Level for lifetime cancer risk of 1 per 100,000: 0.4 ppb

Level for lifetime cancer risk of 1 per 10,000: 4 ppb

Level found at Devon plant on Jim Baker Road on Oct. 14: 46 ppb

Amount released in 2008, as reported by Texas companies: 1.9 million pounds

Amount released in 2008, as reported by Denton County Barnett Shale operators: 0

SOURCES: Texas Commission on Environmental Quality, Environmental Protection Agency