Elevated levels of diesel range organic compounds in groundwater near Marcellus gas operations are derived from surface activities

Abstract

Hundreds of organic chemicals are used during natural gas extraction via high-volume hydraulic fracturing (HVHF). However, it is unclear whether these chemicals, injected into deep shale horizons, reach shallow groundwater aquifers and affect local water quality, either from those deep HVHF injection sites or from the surface or shallow subsurface. Here, we report detectable levels of organic compounds in shallow groundwater samples from private residential wells overlying the Marcellus Shale in northeastern Pennsylvania. Analyses of purgeable and extractable organic compounds from 64 groundwater samples revealed trace levels of volatile organic compounds, well below the Environmental Protection Agency's maximum contaminant levels, and low levels of both gasoline range (0-8 ppb) and diesel range organic compounds (DRO; 0-157 ppb). A compound-specific analysis revealed the presence of bis(2-ethylhexyl) phthalate, which is a disclosed HVHF additive, that was notably absent in a representative geogenic water sample and field blanks. Pairing these analyses with (i) inorganic chemical fingerprinting of deep saline groundwater, (ii) characteristic noble gas isotopes, and (iii) spatial relationships between active shale gas extraction wells and wells with disclosed environmental health and safety violations, we differentiate between a chemical signature associated with naturally occurring saline groundwater and one associated with alternative anthropogenic routes from the surface (e.g., accidental spills or leaks). The data support a transport mechanism of DRO to groundwater via accidental release of fracturing fluid chemicals derived from the surface rather than subsurface flow of these fluids from the underlying shale formation.natural gas extraction | high-volume hydraulic fracturing | groundwater | hydrophobic organic contaminants | transport mechanisms

Monitoring Marcellus: A Case Study of a Collaborative Volunteer Monitoring Project to Document the Impact of Unconventional Shale Gas Extraction on Small Streams

“…Although the Pennsylvania Department of Environmental Protection (PA DEP) standards dictate that any flowback water must be treated to have a total dissolved solids (TDS) concentration of less than or equal to 500 mg/L, only one treatment plant in Pennsylvania has been completed for this purpose (Marcellus Center for Outreach and Research 2015). If not handled properly, this water may contaminate streams and groundwater (Rozell and Reaven 2012;Drollette et al 2015). Experience in Pennsylvania shows that safety and environmental violations are common in the industry: From 2009-2014, 4006 violations were reported by the PA DEP on 7,788 unconventional active wells (Amico et al 2015).…”

“…The management of large volumes of highly contaminated water may result in spills to surface water and/or movement into ground water supplies. Experience in the state has demonstrated that spills and accidents are common (NRDC 2015;Amico et al 2015;Drollette et al 2015).…”

Quantifying Market and Non-market Benefits and Costs of Hydraulic Fracturing in the United States: A Summary of the Literature

“…In Pennsylvania the rate is more variable ranging from 0.4 spills of these materials per 100 hydraulically fractured wells to 12.2 spills per 100 wells. We choose to focus on surface spills as neither Osborn et al (2011), Drollette et al (2015 nor Manning (2015) could find cases where any underground leakages had contaminated drinking water wells. As noted in U.S. Environmental Protection Agency (2015) these contaminations do occasionally happen, but it is rare enough that it is difficult to find any rates of contamination.…”

“…According to Drollette et al (2015) it is these surface spills that often result in contamination of private drinking water wells in their study area in Pennsylvania. Their careful and exhaustive study matched reported hydraulic fracturing related environmental health violations to each of their study's private drinking water well sites, and using chemical signature analysis ruled out most other non-spill related sources.…”

An analysis of the challenges for groundwater governance during shale gas development in South Africa

“…Groundwater contamination can also occur from surface activities (Drollette et al, 2015;US EPA, 2015) related to shale gas production. For example, in a study evaluating groundwater contamination in the Marcellus Shale, a compound identified in flowback [water], 2-n-Butoxyethanol, was positively identified in nearby drinking water wells (Llewellyn et al, 2015).…”