After years of study, on December 13, 2016, the U.S. Environmental Protection Agency (EPA) finally released its final report on Impacts from the Hydraulic Fracturing Water Cycle on Drinking Water Resources in the United States. Despite much attention on the changes to some of the specific language used, this long-awaited final report largely conforms with the preliminary findings set out in the EPA’s draft assessment, dated June 2015, that hydraulic fracturing activities have some potential to impact drinking water resources, but that impacts to date have been relatively isolated rather than pervasive.
Changes have been made in the final report, in comparison with the draft assessment, including providing further clarification relating to the major findings, adding other chemicals to the chemicals listed in the draft assessment, and better identifying gaps in data and uncertainties in scientific knowledge. Notably, EPA also reconsidered the language of its conclusion in the draft assessment that the agency “did not find evidence that these mechanisms have led to widespread, systemic impacts on drinking water resources in the United States.” EPA excluded this sentence in its final report explaining that “contrary to what the sentence implied, uncertainties prevent EPA from estimating the national frequency of impacts on drinking water resources from activities in the hydraulic fracturing water cycle.”
The final report is structured in a similar manner to the draft assessment, focusing on five stages in the hydraulic fracturing water cycle: i) water acquisition; ii) chemical mixing; iii) well injection; iv) produced water handling; and v) wastewater disposal and reuse. For each stage, EPA evaluated the potential for impacts on drinking water resources and factors that affect the frequency or severity of impacts. In addition, EPA stated that only relevant scientific literature, available data and public comments were used in assessing the relationship between hydraulic fracturing and drinking water resources.
Concerning the stage of water acquisition, EPA found that groundwater withdrawals may have a considerable impact on the quality of drinking water resources, especially in regions with low water availability due to high water demand and/or changing seasonal and annual weather patterns. EPA explained that groundwater generally recharges quite slowly; thus any impacts on water resources could last decades.
For the chemical mixing stage, although the concentration of additives used in hydraulic fracturing is deemed small, EPA pointed out that the delivered quantities of fracturing fluid at the well site are generally large; as a consequence, fracturing fluid management can present a problem if not handled well. EPA concluded that spills are mainly caused by equipment failure, human error or storage facility impairment. In addition to specifying that the potential for impacts on water resources largely depends on the hydraulic fracturing-related spill characteristics, transport methods and spill response operations, EPA noted the lack of site-specific studies to identify the factors establishing frequency and severity of impacts from the chemical mixing stage of the hydraulic fracturing water cycle. EPA, however, determined that “impacts on groundwater resources have the potential to be more severe than impacts on surface water resources because it takes longer to naturally reduce the concentration of chemicals in groundwater and because it is generally difficult to remove chemicals from groundwater resources.”
As for the well injection stage, EPA sets out the mechanical integrity of well as a significant factor influencing the frequency and severity of impacts on drinking water resources and, more specifically refers to inadequate well casing and cementing as well as improper well plugging and abandonment. According to the report, another important factor concerns the underground injection of fracturing fluids creating fractures that could establish a pathway to aquifers. Interestingly, mostly due to poor data availability, EPA declared it was “unable to determine with certainty whether fractures created during hydraulic fracturing have reached underground drinking water resources.” EPA, however, determined that experience has shown it is unlikely that “hydraulic fracturing fluids would reach an overlying drinking water resource if . . . the vertical separation distance between the targeted rock formation and the drinking water resource is large and . . . there are no open pathways.”
With regard to produced water handling, EPA explained that produced water spills have great potential to impact drinking water sources. Based on available site-specific studies, EPA found that local geology, fluid flow path and chemical composition of produced water are factors affecting the frequency and severity of impacts. Furthermore, EPA added that “large volume spills are more likely to travel further from the site of the spill, potentially to groundwater or surface water resources . . . leading to long-term groundwater contamination.”
Wastewater disposal and reuse is considered the last stage of the hydraulic fracturing water cycle. According to EPA, wastewater from hydraulic fracturing operations is usually injected into Class II wells but also could be managed through evaporation ponds and percolating pits depending upon the geographic region where the wastewater is generated. EPA underscored that wastewater disposal has the potential to create impacts on water resources because fracturing fluids can end up either in surface or groundwater. EPA, however, mentioned that the risk of contamination is higher for underground aquifers because of the slow groundwater flow speed but noted that soil and sediment properties are also factors to consider.
EPA dedicated a whole section of its report to explain the data gaps and uncertainties during the course of its assessment. EPA admitted lacking important information on data regarding the location of drinking water resources, water withdrawals, hydraulically fractured oil and gas production wells, and hydraulic fracturing wastewater management practices as well as information on chemicals in the hydraulic fracturing water cycle. As a result, EPA emphasized the need for further research highlighting the fact that “the uncertainties and data gaps identified throughout this report can be used to identify future efforts to further [the] understanding of the potential for activities in the hydraulic fracturing water cycle to impact drinking water resources and the factors that affect the frequency and severity of those impacts.”
In its concluding observations, EPA commented that “evaluating the potential for activities in the hydraulic fracturing water cycle to impact drinking water resources will need to keep pace with emerging technologies and new scientific studies.” The agency finally contended that “this report provides a foundation for these efforts, while helping to reduce current vulnerabilities to drinking water resources.”
An upcoming blog article will address the timeline of events that led up to the EPA’s final report in assessing the potential impacts of hydraulic fracturing on drinking water resources. Stay tuned!
Written by Chloe Marie - Research Fellow