The Proceedings of the National Academy of Sciences study that was published last week was led by researchers at Yale, including Robert Jackson (now with Stanford University) and Avner Vengosh. Both were behind previous Duke University studies that purported to find widespread contamination from shale development, but which were hobbled by lack of sufficiently relevant data including the lack of baseline measurements. But as their new study explains,
“We found no evidence for direct communication with shallow drinking water wells due to upward migration form shale horizons. This result is encouraging, because it implies there is some degree of temporal and spatial separation between injected fluids and the drinking water supply.”
It seems that although the contaminants measured were well below the EPA drinking water threshold, their signatures indicate a common source with diesel range organic chemicals and some chemicals that are fracking fluid additives.
Consequently, the paper is saying that the drilling and fracking of the boreholes per se is not the cause of what little groundwater contamination exists, minor and isolated pollution events have occurred as a result of surface spillage.