PNAS (published online before print July 9, 2012, doi: 10.1073/pnas.1121181109) / by Nathaniel R. Warner, Robert B. Jackson, Thomas H. Darrah, Stephen G. Osborn, Adrian Down, Kaiguang Zhao, Alissa White and Avner Vengosha
[Abstract] The debate surrounding the safety of shale gas development in the Appalachian Basin has generated increased awareness of drinking water quality in rural communities. Concerns include the potential for migration of stray gas, metal-rich formation brines, and hydraulic fracturing and/or flowback fluids to drinking water aquifers. A critical question common to these environmental risks is the hydraulic connectivity between the shale gas formations and the overlying shallow drinking water aquifers. We present geochemical evidence from northeastern Pennsylvania showing that pathways, unrelated to recent drilling activities, exist in some locations between deep underlying formations and shallow drinking water aquifers. Integration of chemical data (Br, Cl, Na, Ba, Sr, and Li) and isotopic ratios (87Sr/86Sr, 2H/H, 18O/16O, and 228Ra/226Ra) from this and previous studies in 426 shallow groundwater samples and 83 northern Appalachian brine samples suggest that mixing relationships between shallow ground water and a deep formation brine causes groundwater salinization in some locations. The strong geochemical fingerprint in the salinized (Cl > 20 mg/L) groundwater sampled from the Alluvium, Catskill, and Lock Haven aquifers suggests possible migration of Marcellus brine through naturally occurring pathways. The occurrences of saline water do not correlate with the location of shale-gas wells and are consistent with reported data before rapid shale-gas development in the region; however, the presence of these fluids suggests conductive pathways and specific geostructural and/or hydrodynamic regimes in northeastern Pennsylvania that are at increased risk for contamination of shallow drinking water resources, particularly by fugitive gases, because of natural hydraulic connections to deeper formations.
[From Fracking Insider] … another development in this region is a new Duke University study, published in the Proceedings of the National Academy of Sciences, by the same team that last year reported on methane migration into water wells. The last one received significant media coverage, as well as significant criticism. The latest suggests that naturally occurring pathways could have allowed salty, mineral-rich fluids from the Marcellus shale formation deep underground to migrate up into shallow drinking water aquifers. This study did not tie the occurrence of these deep earth minerals to fracking activity. “The occurrences of saline water do not correlate with the location of shale-gas wells and are consistent with reported data before rapid shale-gas development in the region.” Nor were drilling chemicals, even in areas with resource extraction activities, discovered.
However, according to one of the paper’s authors, Robert Jackson, in an interview with ProPublica, “The biggest implication is the apparent presence of connections from deep underground to the surface. It’s a suggestion based on good evidence that there are places that may be more at risk.” Press coverage, such as this story from Business Insider, have picked up on this line: “[A] new study released in the Proceedings of the National Academy of Sciences concluded that fracking for natural gas under Marcellus Shale in Pennsylvania may lead to harmful gas or liquids flowing upward and contaminating drinking-water supplies.”
But one of the study’s peer reviewers, Terry Engelder of Penn State, so disagreed with the value of the report that he took the unusual step of publicly releasing his review. Chris Tucker, of Energy in Depth, a pro-industry group, also took serious umbrage with the report. Noting that the study did not find any contamination of wells by fracking fluids, Tucker lamented:
“Still, though, while the paper’s findings are benign, and the authors’ insistence that development activities had nothing to do with the detection of salt in water abundantly clear, we’ve seen this saga play out before. Already, activists are pointing to the report as evidence that fracturing fluids may someday migrate up to drinking water sources, denying the facts of science, a history of experience and even the views of the researchers themselves. And reporters, having spotted the words “hydraulic fracturing” and “contamination” in the abstract, are now deciding whether they even need to read the rest of the paper before filing on it.”
The controversy over fracking and waste water disposal, in the Marcellus formation and elsewhere, is not going away soon. At least in terms of waste water, some relief should come soon as two new treatment plants are set to come online in August.