Study: Gas drilling in state hasn’t contaminated wells

Shale-gas production in Arkansas has not resulted in groundwater contamination, according to a study by researchers at Duke University and the U.S. Geological Survey.

The results of the study are based on sampling of127 shallow drinking-water wells in the region of the Fayetteville Shale natural gas production in north-central Arkansas.

“Indeed, we did not find evidence of contamination in groundwater we tested,” said Avner Vengosh, professor of geochemistry and water at Duke University’s Nicholas School of the Environment, on Thursday.

In regions such as the Fayetteville Shale, hydraulic fracturing - often referred to as fracking - is used to break up rock formations to release the gas. The process involves forcing a high volume of water, sand and chemicals deep into rock formations, then horizontally, to fracture rock layers and release the gas.

Environmental groups have contended that the process threatens groundwater many communities rely on for drinking water and other household purposes.

Vengosh said the study group wanted to determine whether water supplies were threatened by potentially elevated methane gas levels, as the group found in Pennsylvania last year. The testing in Arkansas did not reveal such elevated levels, he said. The testing was done over the past year.

“We didn’t see any effect of shale gas,” Vengosh said.

Katherine Benenati, a spokesman for the Public Outreach and Assistance Division of the Arkansas Department of Environmental Quality, said the agency had no comment about the findings.

In the joint news release, Vengosh said that “only a fraction of the groundwater samples we collected contained dissolved methane, mostly in low concentrations, and the isotopic fingerprint of the carbon in the methane in our samples was different from the carbon in deep shale gas in all but two cases.”

That finding indicated that the methane resulted primarily from biological activity in the region’s shallow aquifers, rather than from shale-gas contamination, he said.

“The take-home message is that regardless of the location, systematic monitoring of geochemical and isotopic tracers is necessary for assessing possible groundwater contamination,” Vengosh said. “Our findings in Arkansas are important, but we are still only beginning to evaluate and understand the environmental risks of shale-gas development. Much more research is needed.”