A new study finds residential wells more likely to be contaminated when near drilling for natural gas using hydraulic fracturing.
Researchers led by Duke University's Robert Jackson report that although the vast majority of wells checked in northeastern Pennsylvania and southeastern New York had methane in them, those within one kilometer of gas drilling sites had six times more of the gas, on average, than residential wells farther away.
The findings, appearing in the Proceedings of the National Academy of Sciences, shed new light on controversy over the environmental impacts of hydraulic fracturing, or "fracking," which is widely used nationwide to extract natural gas. Critics contend fracking has contaminated residential wells near drilling sites, but industry and many state officials say there is no evidence fracturing itself has fouled any wells in the region.
Methane occurs naturally in shallow ground water across the Appalachian region, which includes western Maryland. Pennsylvania officials have concluded, for instance, that it was naturally occurring methane that fouled the well of Matt and Tamming Manning in Franklin, PA, one of several such instances reported in a Baltimore Sun story about the controversy earlier this year.
The Duke-led research team analyzed the concentrations and chemical signatures of methane, ethane and propane in 141 wells in the area. Four out of five wells checked had methane in them, but levels were much higher in those closer to drilling sites.
In some cases, the Duke study says, the chemical signature of the gases found indicated they likely came from the Marcellus shale formations deep underground that are tapped by gas companies using horizontal drilling and hydraulic fracturing. The authors suggest faulty gas well casings and cement linings may have allowed gases being extracted to leak into ground water.
An industry public relations consultant, though, disputed the Duke study's conclusions, pointing out that the U.S. Geologic Survey reported finding natural-gas methane in two of 20 wells sampled in another part of Pennsylvania where there's been no drilling.
The study comes as a commission appointed by Gov. Martin O'Malley drafts a report recommending "best practices" for drilling safely for gas in the Marcellus deposits beneath Garrett and western Allegany counties. Drilling has been on hold in Maryland until the commission finishes evaluating the impacts of widespead drilling using "fracking."