A study released on Monday reveals that drinking water wells near hydraulic fracturing—fracking—sites are six times more likely to be contaminated with methane than other wells.
A research team led by Robert Jackson of Duke University sampled 141 drinking water wells across northeastern Pennsylvania and southern New York, an area that has seen a boom in natural gas drilling in the past decade, USA Today reports. The study was published in the Proceedings of the National Academy of Sciences. The results echo those of a 2011 study that first linked proximity to fracking wells to methane contamination of drinking water.
The study found that methane contamination was more likely in wells with a thousand feet of fracking sites. The study found propane in 10 nearby wells and the researchers said ethane gas was 23 times more likely to be detected in homes close to fracking sites, according to USA Today. Jackson said the gases probably escaped from leaks in the steel or concrete casing lining the wellbore, the uppermost part of the natural gas well.
The researchers found no sign of diesel fuel or other industrial fluids used in fracking in the drinking water wells. The process of fracking injects water and sand laced with industrial fluids deep into rock and then forces it sideways under high pressure to crack shale layers and release natural gas. There was no evidence of wide-scale leaks of methane far from the fracking sites beyond naturally occurring amounts seen in recent U.S. Geological Survey reports from the region, according to USA Today.
Fracking is controversial because of the dangers in the process itself and the potential risks to the environment, including air pollution from chemicals and fuels used in fracking and contamination of drinking water. Fracking requires large volumes of water, raising concerns not only about the impact on water supplies in areas near fracking operations but also about the disposal of wastewater from fracking.
The study found a slight increase in water well contamination near older fracking sites, which could either be a sign of leaks increasing as casings age or an indication of better seals and oversight of newer natural gas wells. The Pennsylvania Department of Environmental Protection issued 32 percent more citations for faulty fracking well casings from 2010 to 2011, a sign of increased regulation, USA Today reports. In a similar survey of drinking water wells near fracking sites in Arkansas released last month, Jackson’s team found no signs of contamination, USA Today reports. “Every fracking site is different and every place’s geology is different. That may be what we are seeing here,” Jackson says. “It’s clear that we need to focus on well integrity from these results.”