Identification of local groundwater pollution in northeastern Pennsylvania: Marcellus flowback or not?

Northeastern Pennsylvania has rapidly changed over the past 5 years from an area with no unconventional natural gas drilling, to the most productive shale gas region within the Marcellus shale play, causing concerns about environmental safety. One issue that has caught the attention of homeowners and media is the possibility that flow-back fluids from drilling and fracturing processes have contaminated private water wells. Major and trace ion water chemistry was analyzed from 21 groundwater wells suspected by homeowners to be contaminated by flow-back fluids. These data, collected in 2012–2013, were compared to historical groundwater data, Marcellus flow-back fluid, and other sources of common groundwater contamination in rural areas (agricultural waste, septic waste, and road salt). Results from graphical and statistical tests indicate that flow-back fluids have not impacted these wells. However, some of the 2012–2013 wells do plot graphically within zones identified as waters that have been influenced by animal waste, septic, or road salt. The remaining 2012–2013 wells are geochemically similar to historical groundwater wells. These findings suggest that the major and trace element geochemistry of local groundwater in the northeastern Pennsylvania study area has not been detectably influenced by flow-back fluid spills.