A new study is shedding more light on the environmental costs of shale gas extraction.
Led by Robert B. Jackson of Duke University, the study published Monday in the Proceedings of the National Academy of Sciences found that drinking water wells in close proximity to natural gas wells that use horizontal drilling or fracking were contaminated with stray gases including methane, ethane and propane, with methane concentrations an average of six times higher than those wells farther away.
“The methane, ethane and propane data, and new evidence from hydrocarbon and helium content, all suggest that drilling has affected some homeowners’ water,” lead author Robert B. Jackson, a professor of environmental sciences at Duke’s Nicholas School of the Environment, said in a statement. “In a minority of cases the gas even looks Marcellus-like, probably caused by poor well construction.”
The researchers, who studied 141 drinking water wells primarily in northeastern Pennsylvania, found methane in the drinking water of 82% of the houses sampled, and the methane concentrations in wells of homes less than one kilometer from a gas well were six times higher on average than those located farther away.
A similar pattern emerged for ethane, with concentrations of the gas found 23 times higher on average for homes less than one kilometer from a gas well. The researchers found propane in 10 of the 133 homes they studied for this gas, all close to a gas well.
"The ethane and propane are signatures of fracking," USA Today reports Jackson as saying.
The Associated Press notes that the new study "is an expansion of a 2011 study that attracted widespread attention for its finding that drilling was polluting some water wells with methane."
“The new data reinforces our earlier observations that stray gases contaminate drinking water wells in some areas of the Marcellus shale," added Avner Vengosh, study co-author and professor of geochemistry and water quality at Duke’s Nicholas School.
As DeSmogBlog's Steve Horn points out, "The Duke study offers food-for-thought in the hours leading up to President Obama's forthcoming announcement of a climate change legislative plan at Georgetown University, just a month after his Bureau of Land Management adopted the American Legislative Exchange Council (ALEC) model bill for fracking chemical fluid disclosure on public lands."