Study: Drinking water could be at risk

A study that found hydraulic fracturing for natural gas puts drinking-water supplies in Pennsylvania at risk of contamination may renew a long-running debate between industry and activists.

The report by researchers at Duke University, published Monday in the Proceedings of the National Academy of Sciences, said a chemical analysis of 426 shallow groundwater samples found matches with brine found in rock more than a mile deep, suggesting paths that would let gas or water flow up after drilling. While the flows weren't linked to hydraulic fracturing, or fracking, the study found natural routes for seepage into wells or streams.

In fracking, water, sand and chemicals are injected into deep shale formations to crack the rock and free trapped gas.

Gas is likely to leak up from the shale formation first, before water or drilling fluids, said Avner Vengosh, a professor at the Nicholas School of the Environment at Duke University and one of the study's eight authors.

The study found that the minerals in shallow wells flowed there naturally, over time. It found no connection between gas drilling and water contamination.

Industry representatives said that was the most important finding. "The researchers make it crystal clear that the phenomena they observed had nothing to do with shale development," said industry spokesman Chris Tucker.