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Retrospective Case Study in the Raton Basin, Colorado, Study of hte Potential Impacts of Hydraulic Fracturing on Drinking Water Resources.
Citation:
Wilkin, Rick, A. Wolfe, T. Lee, C. Ruybal, AND G. Oberley. Retrospective Case Study in the Raton Basin, Colorado, Study of hte Potential Impacts of Hydraulic Fracturing on Drinking Water Resources. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-14/091, 2015.
Impact/Purpose:
As a component of the EPA’s National Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources (US EPA, 2012), five retrospective case studies were conducted to investigate reported instances of drinking water resource contamination in areas of natural gas development and use of hydraulic fracturing technology. These studies were intended to inform primary research questions related to the hydraulic fracturing water cycle (US EPA, 2012).
Description:
This report describes the retrospective case study that was conducted in the Colorado portion of the Raton Basin, located within Las Animas and Huerfano counties. These locations are the focus of unconventional gas production of coalbed methane (CBM) from several coal-bearing strata in the basin. CBM development and production within the Raton Basin have increased over the past decade, and is one of the most productive CBM basins in the United States. Recovery of CBM in the Raton Basin occurs within or in close proximity to resources classified as Underground Sources of Drinking Water. In this study, water quality samples were collected from 14 domestic wells, five monitoring wells, three production wells, and three surface water bodies during four sampling rounds in October 2011, May 2012, November 2012, and April/May 2013. Specific sampling locations were selected based on criteria such as well depth, geologic and hydrologic characteristics, and proximity to CBM wells. In order to help differentiate potential impacts from hydraulic fracturing or processes related to hydraulic fracturing from other potential contaminant sources that may have caused or contributed to alleged impacts on water quality, detailed environmental record searches were conducted.Water samples were analyzed for metals, anions, dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), dissolved gases (e.g., methane and ethane), volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), low-molecular-weight acids (LMWAs), glycol ethers, gasoline-range organics (GRO), diesel-range organics (DRO), dissolved strontium isotope ratios (87Sr/86Sr), and stable isotopes of oxygen and hydrogen in water (18OH2O, 2HH2O), carbon and hydrogen in methane (13CCH4, 2HCH4), carbon in dissolved inorganic carbon (DIC; 13CDIC), sulfur and oxygen in sulfate (34SSO4, 18OSO4), and sulfur in hydrogen sulfide (34SH2S). These data were collected in order to evaluate possible scenarios of drinking water impairment that may be related to CBM development.Study results showed consistent major ion patterns over the one-and-a-half-year period of the project. Time-independent trends in major ions suggest that significant water migration from gas-producing zones to shallower aquifers used for drinking water has not occurred. TBA was detected in ground water samples collected from three domestic wells, two monitoring wells, and one production well. The formation pathway of TBA is unresolved; both anthropogenic and natural sources are possible. Methane was ubiquitous in ground water samples collected in this study. In one area, methane isotope data indicate that the methane is microbially sourced and distinctive from the thermogenic gas present in the underlying CBM-producing coal beds.
URLs/Downloads:
https://www.epa.gov/hfstudy/report-retrospective-case-study-raton-basin-colorado-pdfRetrospective Case Study in the Raton Basin, Colorado
Fact Sheet: Raton Basin, Colorado RetrospectiveCase Study