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Stray methane gas is the most common elemental ratios and isotopic compositions exposures and different environmental
groundwater problem in areas of can provide signatures of wastewater from conditions, resulting in the identification
Marcellus Shale development in UOG production ( e.g., Akob et al., 2016; of potentially toxic metals being mobi-
Pennsylvania, followed by dissolved salts Lauer et al., 2016; McMahon et al., 2017) . liz ed from black-shale drill-cuttings ( e.g.,
from produced water ( Brantley et al., Residential water-supply wells in the Stuckman et al., 2015) . Understanding
2014) . Other contaminants linked to shale vicinity of new oil and gas production these processes will guide management of
gas include metals, naturally occurring wells are often sampled to provide pre- these waste materials.
radioactive materials ( NORM) , and drilling information about water quality.
organic compounds. Contaminants enter The data are collected for liability reasons SITE- BASED PROJ ECTS
surface water primarily through spills or ( USEPA, 2016) and are not well suited for EX AMINING POTENTIAL
leaks and infiltrate downward into shal- interpreting sources of contamination ENVIRONMENTAL IMPACTS OF
low aquifers. No evidence supports aqui- ( Table S2 [ see footnote 2] ) . Molofsky et al. UOG D EVELOPMENT
fer contamination by the upwelling of flu- ( 2016) assessed best practices for sam- Access to UOG sites for environmental
ids from production z ones ( e.g., Fisher and pling, laboratory analysis methods, data monitoring has been challenging for non-
Warpinski, 2012; Hammack et al., 2014; management, and analysis protocols for industry researchers ( Soeder, 2015) , but
McMahon et al., 2017) . residential water wells in areas of UOG collaboration between academic, govern-
Recent investigations have contributed development. ment, and industry researchers has been
to a growing consensus that stray gas in improving. A multidisciplinary project
aquifers results primarily from casing fail- RESEARCH TO AD D RESS begun in 2013 to examine potential envi-
ures in older production wells, rather than POTENTIAL IMPACTS OF LIQ UID ronmental and human-health impacts of
migration from z ones where hydraulic AND SOLID W ASTES AND SPILLS UOG development, primarily in the
fracturing was conducted in horiz ontal Increases in UOG activities result in Rocky Mountain region ( Table S3 [ see
wells ( e.g., Brantley et al., 2014; Lackey et more environmental violations ( Kell, footnote 2] ) , has produced more than 50
al., 2017) . The challenges of understand- 2011) and spills ( Lauer et al., 2016) . An publications assessing air- and water-
ing stray gas migration in the subsurface 11.3-million-liter spill of Bakken and quality impacts; wastewater treatment
were illustrated by a test at the Borden Three Forks produced water into a North and re-use; public health outcomes; and
groundwater research site in Ontario, Dakota creek contained total dissolved socio-political and economic factors asso-
Canada. Methane was injected into the solids ( TDS) of 300 g per liter and high ciated with UOG development. Potential
well-characteriz ed, shallow sand aquifer, concentrations of ammonium, barium, water-resource risks have been assessed
and migration was monitored spatially and strontium, and radium ( Lauer et al., 2016; near Marcellus Shale wells in Susquehanna
temporally at high resolution ( Cahill et al., Coz z arelli et al., 2017) . Geochemical alter- County, Pennsylvania, since 2015 ( Table
2017) . The gas was transported in solution ations in the stream persisted for at least S4 [ see footnote 2] ) . Analyses of pro-
by advection and diffusion and laterally in six months after the spill, and fish kills duced water and hydrocarbons from pro-
the gas phase through interconnected lay- were observed 7 km downstream of the duction wells are providing signatures for
ers of somewhat coarser sediments ( Fig. 1 spill site. Radium and strontium isotopic potential contaminants like trace metals,
# 7) . It persisted in the aquifer for more signatures in downstream sediments major ions, and hydrocarbons. Studies
than a year, longer than expected. resembled those from the spilled fluid like these will provide insight into the
Baseline water-quality data are needed ( Coz z arelli et al., 2017) . Slow release of natural spatial and temporal variation in
to assess potential water-quality degrada- spill-derived chemicals from sediment water quality needed to detect impacts
tion. Researchers from the USGS and could provide a long-term contaminant from UOG development.
Northeast Midwest Institute investigated source in aquatic ecosystems. Field research projects involving part-
decades of legacy water-quality data Organic-rich shales were deposited in nerships between DOE and industry are
from the Susquehanna River Basin in anoxic marine environments and contain improving UOG-development technolo-
Pennsylvania to determine if baseline con- sulfide minerals, radionuclides, and gies while reducing environmental and
ditions prior to shale-gas development reduced inorganic elements ( Chermak and health impacts. The Hydraulic Fracturing
could be determined ( Betanz o et al., Schreiber, 2014) . Hydraulic fracturing Test Site ( HFTS) in the Permian basin of
2016) . Most of the existing water-quality fluids often react with shale downhole, Texas underwent environmental assess-
monitoring sites were found in the lower mobiliz ing inorganic compounds like bar- ments before, during, and after develop-
parts of the basin and established for ium ( Renock et al., 2016) or creating new ment phases ( Fig. 1 # 1–6) . Air quality was
nutrient and pesticide inputs to the organic compounds that are found in the monitored for methane, NO , and VOCs.
x
Chesapeake Bay. The data sets were not produced fluids ( Kahrilas et al., 2016) . Groundwater quality was monitored
useful for assessing water-quality impacts Horiz ontal drilling of a single shale well within 4 km of production wells. Produced
of shale-gas development in headwater can generate several hundred tons of drill water was analyz ed to evaluate potential
streams. Impacts of UOG development on cuttings, which may release harmful ele- impacts to wellhead and casing integrity
groundwater and surface-water quality ments like arsenic, radium, and uranium ( Table S5 [ see footnote 2] ) . New hydraulic
can be difficult to distinguish from ( Phan et al., 2015) . The leachability of fracturing technologies were tested to
impacts of septic systems and legacy coal drill cuttings has been investigated in the optimiz e hydrocarbon extraction effi-
mining ( Messinger and Hughes, 2000) , but laboratory under short-term and long-term ciency. Preliminary findings indicate that

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