The environmental impacts of fracking the Marcellus Shale are diverse. Effects on surface water,
groundwater, traffic, earthquake activity, and human health are discussed here. Other associated issues include disposal of produced water, drilling safety, forest fragmentation, encroachment on residential communities,
methane emissions, and
land reclamation.
Water use The massive hydraulic fracturing in the Marcellus uses three to five million gallons of water per well, usually taken from surface water. In Pennsylvania, withdrawals for Marcellus fracking make up 0.2% of the total water use statewide. Due to large withdrawals of surface water many water bodies may experience increased salinization and warming. The
Susquehanna River Basin Commission, which oversees this other portion of the watershed, and the
Pennsylvania Department of Environmental Protection, issued orders to suspend operations at several wells in May 2008 because surface water was being diverted by the drillers without the necessary permits, and precautions to protect streams from contaminated runoff were questioned.
Surface water The three main pathways of surface water contamination from shale gas extraction are spills of
produced water, illegal dumping of wastewater, and inadequate treatment before discharge of
produced water.
Groundwater Fugitive gas emissions can infiltrate into local aquifers around hydraulic fracturing well pads through natural underground fractures, as well as those created during the hydraulic fracturing process. In many cases, there is a significant lack of baseline data to determine if methane migration can be attributed to gas extraction or if it is naturally occurring. Recent studies evaluating noble gas concentrations, hydrocarbon stable isotopes, and molecular carbon ratios have been used to determine if the source of methane contamination is due to gas extraction. A 2013 study which evaluated data from 1701 water wells throughout
Susquehanna County in northeastern
Pennsylvania, concluded that methane was common in water wells, and that the presence of methane is best correlated with topography and groundwater geochemistry, rather than shale-gas extraction activities. The authors concluded that "This finding suggests that shale-gas extraction in northeastern Pennsylvania has not resulted in regional gas impacts on drinking water resources". The
Pennsylvania Department of Environmental Protection concluded that Marcellus gas wells caused dissolved methane to contaminate up to 15 domestic water wells in
Dimock Township, Susquehanna County, Pennsylvania. This conclusion is disputed by Cabot Oil & Gas Corp., which was cited for causing the contamination. It is also disputed by other long-term area residents who noted that high methane levels had been present for more than 60 years prior to hydraulic fracturing in
Dimock. Pennsylvania state law sets a "rebuttable presumption" for contamination occurring in water supply wells near oil and gas wells, meaning that the law automatically holds oil and gas operators responsible for contamination in nearby water wells, unless the companies can demonstrate that they were not responsible. The new Pennsylvania oil and gas law passed in February 2012 increased the rebuttable presumption distance around each oil and gas well, from 1,000 feet to 2,500 feet, and increased the time period from 6 months to one year following drilling, completion, or alteration of a well bore.
Traffic There are also impacts from heavier traffic and construction around extraction and injection wells that can increase erosion and result in sedimentation in surrounding streams. the area's 11th earthquake in 10 months. Experts believe that these were
induced seismicity triggered by disposal of wastewater from Marcellus gas wells into Class II underground
injection wells. The
Ohio Department of Natural Resources Ohio Seismic Network (OhioSeis) determined that the 2011 earthquakes are distinct from previous seismic activity in the region because of their proximity to the Northstar 1, a Class II deep injection well. All of the earthquakes were clustered less than a mile around the well. ODNR has continued to report increased seismic activity through 2017 in eastern Ohio in near proximity to injection wells.
Potential carbon impact In 2022, a team of researchers in a paper published in
Energy Policy identified the Marcellus Shale as a "carbon bomb," a fossil fuel project that would result in more than one
gigaton of
carbon dioxide emissions if fully extracted and burnt. The Marcellus Shale is the second-largest carbon bomb in the United States the researchers identified, with a total of 26.7 gigatons of if full developed and used. == Social issues ==