Retrospective Case Study in Northeastern Pennsylvania, Study of the Potential Impacts of Hydraulic Fracturing On Drinking Water Resources
Citation:
Ludwig, R., D. Beak, Rick Wilkin, AND C. Ruybal. Retrospective Case Study in Northeastern Pennsylvania, Study of the Potential Impacts of Hydraulic Fracturing On Drinking Water Resources. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-14/088, 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 for northeastern Pennsylvania, which was conducted in Bradford and Susquehanna Counties where some of the most intensive unconventional gas production from the Devonian-age Marcellus Shale has occurred. Gas production from the Marcellus Shale depends on recent advances in horizontal drilling and hydraulic fracturing technologies to enhance and create fracture porosity and permeability to facilitate gas flow. In this study, water quality samples were collected from domestic wells, springs, and surface water locations during three events in fall 2011, spring 2012, and spring 2013. The sampling locations were selected based upon homeowner complaints/ concerns about deteriorated water quality potentially linked to nearby hydraulic fracturing activities. The geochemistry of water samples was investigated by analysis of major ions, trace metals, dissolved methane/ethane gas concentrations, volatile organic compounds (VOCs), low-molecular-weight acids, semivolatile organic compounds (SVOCs), glycol ethers, diesel-range organics (DRO), gasoline-range organics (GRO), radiometric constituents, strontium isotope ratios, and selected stable isotopes. Major-ion data collected for this study were compared to historical water quality data for the study area obtained from the literature and national water quality databases. Statistical comparisons were made between the data collected for this study and the historical data to evaluate possible differences or inconsistencies. To help determine whether hydraulic fracturing or processes related to hydraulic fracturing had impacts on water quality, other potential contaminant sources were also identified through detailed environmental record searches. The study data indicated evidence of stray gas (methane and ethane) impacts to one or more domestic wells sampled in the study, and chloride and TDS impacts to a homeowner pond likely originating from past releases of fluids and/or solids on a well pad located adjacent to the pond. Gas isotopic analysis and methane to ethane ratio data indicated stray gas in domestic wells was thermogenic in nature originating from both shallow and deeper formations with gas in one cluster of wells exhibiting Marcellus-like signatures. The elevated chloride and TDS concentrations measured in the homeowner pond were not consistent with chloride and TDS concentrations found in surface waters in the study area. Iron and/or manganese concentrations were found to exceed secondary MCLs in more than 40% of wells sampled in the study, although this is consistent with historical data for the study area. Methane occurs naturally as background gas in many domestic wells in northeastern Pennsylvania.
URLs/Downloads:
https://www.epa.gov/hfstudy/report-retrospective-case-study-northeastern-pennsylvania-pdfRetrospective Case Study in Northeastern Pennsylvania
Fact Sheet: Northeastern Pennsylvania Retrospective Case Study