A controversial natural gas production technique, which is key to a century of U.S. domestic supply, is causing contamination of drinking water, a study released by the Proceedings of the National Academy of Sciences said on Monday.
Scientists from Duke University collected 68 drinking water samples which showed potentially harmful levels of methane in drinking water near drilling sites in Pennsylvania and New York associated with the process of hydraulic-fracturing, or fracking.
"In aquifers overlying the Marcellus and Utica shale formations of northeastern Pennsylvania and upstate New York, we document systematic evidence for methane contamination of drinking water associated with shale gas extraction," the report said.
Fracking involves releasing natural gas trapped in shale formations by blasting a mix of water, sand and chemicals into the rock. It has unlocked reserves that could supply the United States for 100 years, though environmentalists say that fracking can contaminate water supplies.
Methane concentrations were detected in 51 of 60 drinking-water wells across the region, regardless of gas industry operations, but concentrations were much higher closer to natural-gas wells, the report said. Levels were 17-times higher on average in shallow wells from active drilling areas than in wells from nonactive areas, the report said.
The report concluded that "greater stewardship, data, and possibly regulation are needed to ensure the sustainable future of shale-gas extraction and to improve public confidence in its use."
Last week, President Barack Obama asked the U.S. Department of Energy to form a panel of academic and environmental experts to identify any immediate steps that can be taken to improve the safety and environmental performance of fracking after a series of high-profile natural gas drilling spills.
Fracking has opened up vast new supplies of natural gas that will reduce imports of the fuel, and drillers argue that methane contamination was present in drinking water before drilling began. Backers also say it could reduce oil imports in the future, if vehicles are converted to run on natural gas.
But residents near drilling wells have complained fracking has polluted ground water supplies enough that they can light their drinking water on fire. In addition, accidents at wells have led to fires and floods of fracking fluids have reached streams.