Natural gas is commonly found in drinking water wells in northeastern Pennsylvania, but a new Duke University study says there's a lot more of it near Marcellus Shale gas wells.
The study expands on a 2011 Duke study that shook the world of shale drilling by offering the first peer-reviewed findings correlating drilling and contaminated drinking water (Greenwire May 9, 2011). It is also a response to an industry study that discounted the Duke findings by deeming methane in the area's drinking water "ubiquitous" (EnergyWire, May 31).
The team, which also includes researchers from the University of Rochester and California State Polytechnic University, sampled 81 new drinking water wells in six counties in northeastern Pennsylvania. It combined the data with results from 60 previously sampled wells in Pennsylvania and included a few wells in New York's Otsego County.
The researchers detected methane, the principal component of natural gas, in the drinking water of 82 percent of the 141 homes. Concentrations were six times higher in homes within a kilometer (about 3,300 feet) of natural gas wells, the study found.
Of 12 houses where the concentration of methane were greater than the federal threshold for immediate remediation, 11 homes were within the 3,300-foot radius. The only exception was a house 1.4 kilometers (4,600 feet) from a well.
The study also found that ethane and propane were more common closer to wells. They are both components of natural gas but are found in the deep shale gas that drillers want. They are not found in the shallow, "biogenic" gas that is commonly found in well water supplies.
"Our observed values within 1 kilometer of drilling seem to rule out a biogenic methane source," states the peer-reviewed study, authored by Duke biology professor Rob Jackson and released today by the journal Proceedings of the National Academy of Sciences.
The original Duke study was criticized by the oil and gas industry and state regulators. Industry figures said that without knowing methane concentrations in the water wells before drilling occurred, the study couldn't draw a solid link between drilling and methane contamination.