MOSCOW, September 16 (RIA Novosti) – Drinking water supplies in Texas and Pennsylvania suffer from regular natural gas contamination, although it is not a direct consequence of horizontal drilling, or fracking, US researchers say.
"Against a backdrop of naturally occurring salt- and gas-rich groundwater, we identified eight discrete clusters of fugitive gas contamination, seven in Pennsylvania and one in Texas that showed increased contamination through time," a study published in the Proceedings of the National Academy of Sciences Monday said.
The study was conducted by scientists from Ohio State University, Stanford University, Duke University, Dartmouth College, and the University of Rochester and was based on over 100 samples from drinking-water wells overlying the Marcellus and Barnett shale gas formations.
The authors of the study say that "horizontal drilling and hydraulic fracturing have enhanced energy production but raised concerns about drinking-water contamination and other environmental impacts."
The scientists note, however, that the contamination of water in Texas and Pennsylvania is not a direct consequence of fracking.
"Noble gas data appear to rule out gas contamination by upward migration from depth through overlying geological strata triggered by horizontal drilling or hydraulic fracturing," the study says.
The researchers claim that the gas leaks are caused by faulty cement casing on natural gas wells, which mirrors the conclusions of a number of earlier studies conducted by scientists from Cornell and Duke universities.
Hydraulic fracturing, or fracking, is a technique for recovering gas and oil from shale rock by drilling down into the ground and injecting water, sand and chemicals into the rock at high pressures, releasing gas to the head of the well.
The method has triggered a surge in US gas production, but raised fears that breaking up rock formations underground could allow gas to seep into drinking water.
The US Environmental Protection Agency is in the midst of a years-long study into the impacts of fracking on drinking water, and is scheduled to release a draft this year, after reports of drinking water so badly contaminated that homeowners could light it on fire.