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
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