On June 5, after years of research and continued debate over hydraulic fracturing’s impact on drinking water in the United States, the Environmental Protection Agency (EPA) released its draft assessment on the practice. Thomas Burke, lead EPA researcher on the project, describes the report as “the most complete compilation of scientific data to date, including over 950 sources of information, published papers, numerous technical reports, information from stakeholders and peer-reviewed EPA scientific reports.”

In its comprehensive study, EPA concludes that fracking has caused water contamination and does pose a risk to drinking water resources. However, EPA did not find evidence of widespread impacts to drinking water resources and further concluded that, “the number of identified cases where drinking water resources were impacted are small relative to the number of hydraulically fractured wells.”

Hydraulic fracturing (commonly referred to as fracking) is the process of pumping a slurry of water, sand and various chemicals into rock formations to release trapped gas and oil. Though fracking has been used in the United States for nearly a century, it is only within the past 15 years that it has been paired with a new technology, horizontal drilling. This new technology has allowed the United States to reach previously uneconomic oil and gas reserves, and to establish itself as the number one producer and exporter of natural gas in the world.

While fracking has increased the U.S. domestic energy supply and provided economic benefits, it has not come without controversy. Many citizens and scientists have become increasingly concerned with fracking, citing potential drinking water contamination as well as occupational safety hazards and extensive toxic air emissions which contribute to climate change. Over 8.6 million people are served by drinking water supplies in close proximity to fracking wells, making drinking water contamination a prime concern. In 2010, these concerns caused Congress to commission EPA to complete an in-depth study detailing fracking’s association with drinking water contamination.

EPA identified five different processes in the fracking water cycle that could serve as mechanisms for drinking water contamination: water acquisition, chemical mixing, well injection, water flowback, and wastewater treatment. For each process they analyzed available data and conducted additional research when necessary in order to determine fracking’s cumulative impact on drinking water.

Water Acquisition

Each fracking well requires an immense amount of water to effectively extract natural gas—on average 1.5 million gallons per well. Some areas of the United States are fortunate to have abundant water resources, but concern is growing over the sheer volume of water used by the extraction process, and potential impacts to other water users, including agriculture, ecological needs and urban users. In areas where water scarcity is more prevalent, such as Texas or California, fracking poses an even greater threat to water resources.

Chemical Mixing (Fracking Fluid)

Thousands of chemicals are contained in the fracking fluid. Many of these chemicals have potential health impacts including, according to EPA, “carcinogenesis, immune system effects, changes in body weight, changes in blood chemistry, cardiotoxicity, neurotoxicity, liver and kidney toxicity, and reproductive and developmental toxicity.” While proper safety procedures can dramatically reduce the potential for human exposure to these mixtures, EPA has found that chemical spill rates can reach 12.2 percent, reaching surface water in 9 percent of spills, and contaminating soil in 64 percent.

Well Injection

EPA reports that the most common cause for water contamination in the well injection phase is failure of the cement casings surrounding the well. The report describes two instances where inadequate or insufficient cement casing led to pollutants including methane and benzene reaching drinking water sources. Despite these two cases, EPA concludes that this component of the fracking process is unlikely to cause groundwater contamination due to the properties of the fracking chemicals and of the surrounding geologic formations. Significantly, EPA did mention that older wells were at a much higher risk for cement casing failure, raising the concern that even if well injection currently poses a limited threat to drinking water, future impacts caused by aging infrastructure could be significantly greater.


Most of the fracking fluid remains in the rock formations, but 10 to 25 percent of it returns to the surface as flowback (commonly referred to as produced water). Between 2006 and 2011, EPA reports that there were 225 spills of flowback water with a median volume of 990 gallons. The majority of these spills were a result of surface storage container failure. Additionally, the EPA found that eight percent of these spills reached surface or groundwater. To date, the largest flowback spill occurred in North Dakota, where 2.9 million gallons spilled from a broken pipeline, impacting both surface and groundwater.

Wastewater Treatment and Waste Disposal

A 2007 survey indicated that 98 percent of wastewater generated by oil and gas wells is managed by underground injection control (UIC) wells, where the wastewater is disposed of by injecting it deep underground. The EPA reports that “disposal wells are also the primary management practice for hydraulic fracturing wastewater.” Despite this, EPA states that studying the impact of UIC wells on drinking water was outside the scope of its assessment. This is because the 2005 Energy Policy Act exempts UIC wells for oil and gas production from regulation under the Safe Drinking Water Act. This exemption is commonly referred to as the “Halliburton Loophole.” An extensive review of UIC wells by ProPublica, a non-profit that conducts investigative journalism, found that structural failures in UIC wells are routine.

Limitations of the Study

While the EPA assessment may be the most comprehensive study to date on fracking, the report is still fraught with limitations. Numerous items were “outside of the scope” of the study, with the most notable exclusion being the lack of research into the potential impacts of UIC wells. EPA also cites the lack of data as a significant stumbling block. In general, very little information was collected on water quality prior to fracking operations, and data on chemical use is incomplete for many fracking wells, making it difficult to assess the direct impact of fracking operations.

EPA also reports that companies refused to release information on fracking fluid chemicals at more than 70 percent of wells, making it difficult to fully analyze the potential impacts of chemical contamination. Additionally, systematic long term health studies are not being conducted by EPA, despite the fact that many of the potential impacts associated with fracking may only become clear over long time periods.

Stakeholder Response

While this study was meant to bring clarity to the dispute over fracking, immediate stakeholder responses appear to suggest that it has only led to more debate. Industry has already touted the study as a victory. Erik Milito, Director of Upstream Operations at the American Petroleum Institute commented, “After more than five years and millions of dollars, the evidence gathered by EPA confirms what the agency has already acknowledged and what the oil and gas industry has known. Hydraulic fracturing is being done safely under the strong environmental stewardship of state regulators and industry best practices.”

Environmental groups are also advertising the study as evidence of fracking’s dangers, with Michael Brune, the Executive Director of the Sierra Club stating, “The EPA's water quality study confirms what millions of Americans already know — that dirty oil and gas fracking contaminates drinking water.” However, environmental groups have also been quick to express their displeasure with the various limitations of the study, with Kassie Siegel, Senior Counsel for the Center for Biological Diversity, commenting, “This study was hobbled by the oil industry’s refusal to provide key data. The EPA found disturbing evidence of fracking polluting our water despite not looking very hard.”


This report will not end the fracking debate and it is unclear how it will influence the direction of U.S. policy. Advocates of fracking are already using the report to fight the Bureau of Land Management’s (BLM) recently introduced regulations on fracking on federal lands, claiming that regulation should largely be left to the states, and that they are an unnecessary burden on industry. Fred Upton (R-MI), Chairman of the House Energy and Commerce Committee stated, “The administration should now reconsider the burdensome regulations it intends to place on hydraulic fracturing on federal lands.” Meanwhile, fracking opponents emphasize that there is still much research to be done. New York and Maryland have both recently extended state level moratorium on fracking, citing insufficient data and impact studies.

The EPA assessment will be finalized after an 85 day public comment period and a review by the EPA’s independent Science Advisory Board.


Author: Ori Gutin