In December, the U.S. Environmental Protection Agency (EPA) released its scientific report on the impacts from hydraulic fracturing activities on drinking water resources, which provides states and others the scientific foundation to better protect drinking water resources in areas where hydraulic fracturing is occurring or being considered. According to EPA, the report, done at the request of Congress, provides scientific evidence that hydraulic fracturing activities can impact drinking water resources in the United States under some circumstances.
As part of the report, EPA identified conditions under which impacts from hydraulic fracturing activities can be more frequent or severe. The report also identifies uncertainties and data gaps. These uncertainties and data gaps limited EPA’s ability to fully assess impacts to drinking water resources both locally and nationally. These final conclusions are based on review of more than 1,200 cited scientific sources; feedback from an independent peer review conducted by EPA’s Science Advisory Board; input from engaged stakeholders; and new research conducted as part of the study.
“The value of high-quality science has never been more important in helping to guide decisions around our nation’s fragile water resources,” said Thomas A. Burke, Ph.D., EPA’s science advisor and deputy assistant administrator of EPA’s Office of Research and Development. “EPA’s assessment provides the scientific foundation for local decision makers, industry, and communities that are looking to protect public health and drinking water resources and make more informed decisions about hydraulic fracturing activities. This assessment is the most complete compilation to date of national scientific data on the relationship of drinking water resources and hydraulic fracturing.”
The report is organized around activities in the hydraulic fracturing water cycle and their potential to impact drinking water resources. The stages include (see Figure 1):
- Water acquisition — acquiring water to be used for hydraulic fracturing;
- Chemical mixing — mixing the water with chemical additives to make hydraulic fracturing fluids;
- Well injection — injecting hydraulic fracturing fluids into the production well to create and grow fractures in the targeted production zone;
- Produced water handling — collecting wastewater that returns through the well after injection; and
- Wastewater disposal and reuse — managing the wastewater through disposal or reuse methods.
EPA identified cases of impacts on drinking water at each stage in the hydraulic fracturing water cycle. Impacts cited in the report generally occurred near hydraulically fractured oil and gas production wells and ranged in severity, from temporary changes in water quality to contamination that made private drinking water wells unusable.
As part of the report, EPA identified certain conditions under which impacts from hydraulic fracturing activities can be more frequent or severe, including:
- water withdrawals for hydraulic fracturing in times or areas of low water availability, particularly in areas with limited or declining groundwater resources;
- spills during the management of hydraulic fracturing fluids and chemicals or produced water that result in large volumes or high concentrations of chemicals reaching groundwater resources;
- injection of hydraulic fracturing fluids into wells with inadequate mechanical integrity, allowing gases or liquids to move to groundwater resources;
- injection of hydraulic fracturing fluids directly into groundwater resources;
- discharge of inadequately treated hydraulic fracturing wastewater to surface water resources; and
- disposal or storage of hydraulic fracturing wastewater in unlined pits, resulting in contamination of groundwater resources.
The report provides valuable information about potential vulnerabilities to drinking water resources but was not designed to be a list of documented impacts.
Data gaps and uncertainties limited EPA’s ability to fully assess the potential impacts on drinking water resources both locally and nationally. Generally, comprehensive information on the location of activities in the hydraulic fracturing water cycle is lacking, either because it is not collected, not publicly available, or prohibitively difficult to aggregate.
In places where activities in the hydraulic fracturing water cycle are known to have occurred, data that could be used to characterize hydraulic fracturing-related chemicals in the environment before, during, and after hydraulic fracturing were scarce, EPA said. Because of these data gaps and uncertainties, as well as others described in the assessment, it was not possible to fully characterize the severity of impacts, nor was it possible to calculate or estimate the national frequency of impacts on drinking water resources from activities in the hydraulic fracturing water cycle.
EPA said its final assessment benefited from extensive stakeholder engagement with states, tribes, industry, non-governmental organizations, the scientific community, and the public. This broad engagement helped to ensure that the final assessment report reflects current practices in hydraulic fracturing and uses all data and information available to the agency.