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Another study, this one by the USGS in North Dakota, suggests fracking has not degraded water quality in an overlying aquifer.

In the last decade, the Bakken Formation has been the focus of intensive fracking for oil recovery, making North Dakota the second most productive state for oil/gas in the U.S. (Texas is number 1). The USGS researchers collected 30 samples from the age Paleocene Fort Union sandstone aquifer. The base of the aquifer is at least 2,500 meters higher that the top of the Bakken Formation. In addition to analyzing for the usual inorganic constituents found in groundwater, the researchers also analyzed for several organic compounds that might be associated with oil deposits, such as methane and benzene.

They concluded that the data gave “no indication that energy-development activities affected groundwater quality.” However, they caution that this does not mean we don’t have to worry about groundwater contamination. Most of the groundwater in the upper Fort Union Aquifer appears to be pre-1950s in age, and thus would not exhibit recent contamination. They state that domestic wells in the region “may not be as well suited for detecting contamination associated with recent surface spills as shallower wells screened near the water table.” None of the sampled wells was close enough to an oil well to be contaminated, based on groundwater flow velocities. Not yet. Thus the researchers recommend a long-term commitment to groundwater quality monitoring in the aquifer.

McMahon, P.B., R.R. Caldwell, J.M. Galloway, J.F. Valder, and A.G. Hunt. Quality and Age of Shallow Groundwater in the Bakken Formation Production Area, Williston Basin, Montana and North Dakota. Groundwater.