The recent report by the US EPA Draft Assessment of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water ... (link to EPA study) states in the executive summary that “We did not find evidence that these mechanisms have led to widespread, systemic impacts on drinking water resources in the United States.” Many blogs, articles, and press releases have pulled this quote and focused exclusively on this sentence of the report. However, we need to be cognizant of additional information and ask ourselves some important questions. For example, what exactly does “widespread” or “systemic impact” truly mean? In addition, the report does an excellent job of pointing out key limitations with the data used to make this overall conclusion. As one example states: “Data that could be used to characterize the presence, migration, or transformation of chemicals in the subsurface before, during, and after hydraulic fracturing were found to be scarce relative to the number of hydraulically fractured oil and gas production wells” (link to executive summary).
Types of Contaminants
Contaminants found in hydraulic fracturing flowback and wastewaters include anions (link to webinar), cations (link to application note), metals (link to webinar), and fracking chemicals. Specifically, bromide (link to application note pdf) from the deep subsurface can impact drinking water supplies during the water disinfection process, resulting in bromate and halogenated organic compounds. In addition, excess barium and strontium (link to application note PDF) can cause scaling within pipes, resulting in restricted water flow and increased cost. The anions, cations, barium and strontium can be analyzed using reagent-free ion chromatography and suppressed conductivity detection. For more information, see this application note on ICP-OES and metals analysis (link to pdf).
The EPA report focuses on the organic compounds present in fracfocus (link to website), a repository for chemicals used in hydraulic fracturing that is now mandatory in many states. However, due to 1) complexity, 2) variable use, and 3) low concentration, organic contaminants are most likely not suitable candidates for indicators of hydraulic fracturing impacts. For this reason, researchers have focused on metals and, more specifically, isotope ratios for carbon and hydrogen from methane, and/or ratios of strontium and thorium isotopes (link to article).
Though the EPA report states that hydraulic fracturing impacts are not widespread, we should not forget that spills will most likely occur, as in any industrial process. This makes analysis a local issue, especially considering flowback waters in open pits, spills, transportation and disposal leaks. Serious local impacts will inevitably occur.
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