For some time now, proponents of the controversial practice of hydraulic fracturing or “fracking” have claimed there was little or no evidence of real risk to groundwater. But as the classic saying goes: “the absence of evidence is not evidence of absence” of a problem. And the evidence that fracking can contaminate groundwater and drinking water wells is growing stronger with every new study.

As most people now know, fracking is a method for enhancing the production of natural gas (or oil, or geothermal energy wells). Fracking involves injecting fluids -- typically complex mixes of water and chemicals – under high pressure into wells to create cracks and fissures in rock formations that improve the rates of production.

Whether you support or oppose fracking depends on many complex factors: the economics of the practice, perceptions about the implications for national security of relying on domestic or imported energy, the consequences for climate change from the emissions of different amounts of greenhouse gases from different energy strategies, the positive and negative implications of fracking for employment and quality of life in rural communities, and the scientific evidence about the environmental consequences of the practice, including risks to water availability, water and air quality, and local ecosystems.

Some of the most significant environmental concerns associated with fracking are related to impacts on water. In 2012, the Pacific Institute released a major study on these water-related risks. These risks include growing competition for limited water resources; the production of large volumes of contaminated wastewater that comes up with the oil or gas and must be treated, reinjected, or otherwise safely stored; truck traffic and its impacts on the water quality of streams; spills and leaks; and the risks of groundwater contamination from the drilling and fracking process or from surface seepage of improperly handled wastewater. Ceres recently released a map showing that many fracking operations are occurring in regions of the US where water stress is already a real problem.

This map, produced at This map, produced at www.ceres.org , shows that nearly half of all US shale gas and oil wells are being developed in regions of the US with high to extremely high water stress. The research is based on well data from FracFocus.org.

The Pacific Institute analysis concluded that a lack of credible and comprehensive data and information makes it much more difficult to identify or clearly assess the key water-related risks associated with hydraulic fracturing and to develop sound policies to minimize those risks. While much has been written about the interaction of hydraulic fracturing and water resources, the majority of this writing is either industry or advocacy reports that have not been peer-reviewed. As a result, the discourse around the issue is largely driven by opinion. Only by comprehensive and careful independent testing and monitoring is it possible to assess the full environmental and public health risks of fracking and identify strategies to minimize these risks This is particularly true for groundwater contamination, which is hard to measure, hard to monitor, and hard to track.

Because of the limited amount of data, some industry proponents have long claimed that fracking is safe. Indeed, we sometimes see statements at odds with actual scientific evidence. Here is one from the American Petroleum Institute:

“There are zero confirmed cases of groundwater contamination connected to the fracturing operation in one million wells hydraulically fractured over the last 60 years.”

Another industry proponent recently described the risks of groundwater pollution from fracking as “almost inconceivable.”

“Inconceivable”? That brings to mind the classic scene from the film Princess Bride, where Inigo Montoya says to Vizzini: “You keep using that word. I do not think it means what you think it means.” [Here is a link to a 10-second clip from the movie: enjoy.]

In fact, even with the limited research done to date, there is clear scientific evidence that fracking not only can -- but already has -- led to groundwater contamination, including a new study just released this week. Here are just seven separate lines of evidence:

As far back as 1984, the USEPA reported on a clear case in which hydraulic fracturing fluids and natural gas from production operations contaminated a groundwater well in West Virginia, “rendering it unusable.” The USEPA issued a draft report in 2011 on groundwater contamination in Pavillion, Wyoming, that showed extensive presence of fracking chemicals (natural and synthetic) in shallow and deep groundwater systems. Some of this contamination may have resulted from faulty wells drilled through groundwater aquifers; some of it may have resulted from surface seepage of fracking waste fluids escaping from badly designed and managed wastewater pits. The US Geological Survey Report issued its own independent assessment of the Pavillion, Wyoming groundwater testing that also showed high concentrations of several chemicals used in fracking. A Canadian groundwater contamination report described a “hydraulic fracturing incident” in 2011 in which errors in well drilling and management led to the release of fracking chemicals into groundwater including isopropanolamine, benzene, toluene, ethylbenzene, xylene, petroleum hydrocarbons, and more. A Duke University peer-reviewed study showed that fracked groundwater systems pose risks to other groundwater systems that were thought to be, but were not, hydraulically separate. This study clearly shows the risks in some groundwater geologies of cross contamination. Even more compelling, another peer-reviewed study published in the Proceedings of the National Academy of Sciences documented “systematic evidence for methane contamination of drinking water associated with shalegas extraction.” The latest peer-reviewed study, released this week, also shows strong evidence that increased concentrations of methane and other hydrocarbons in drinking water wells are directly correlated with proximity to gas wells in the Marcellus Shale region of Pennsylvania.

This growing evidence of a real threat to some of the nation’s valuable groundwater makes it all the more disturbing to learn that the US EPA is halting its own independent assessment of groundwater contamination from fracking in the Pavillion gas fields of Wyoming and even worse, turning that research over to a project funded by the fracking company itself. This smells rotten and is not how independent research should be done.

Far more and better research is needed, and public agencies must demand that monitoring data be independently collected, analyzed, and publicly released. But the evidence already available shows that fracking threatens our water resources. I repeat my comment above: the net effects of fracking depend on a complicated mix of the risks and benefits of the process and how one evaluates, perceives, values, and weighs those effects. But no smart public policy can be made if we turn a blind eye to the risks, fail to pursue comprehensive independent science, or even worse, deny the science and the evidence already available to us.

Peter Gleick