A new study of private water wells in rural Pennsylvania found 20% to be contaminated with methane before Marcellus operations began nearby, but also found increased bromide levels that could be the result of natural gas drilling.
Pennsylvania State University researchers sampled 233 water wells in Marcellus country, testing wells before and after hydraulic fracturing (hydrofracking) and drilling occurred nearby in addition to control wells not near drilling sites.
"In this study, statistical analyses of post-drilling versus pre-drilling water chemistry did not suggest major influences from gas well drilling or hydrofracking on nearby water wells, when considering changes in potential pollutants that are most prominent in drilling waste fluids," the study found.
Those findings contradict a May study from Duke University that found a correlation between higher levels of methane in water wells and hydraulic fracturing, a report that drew heavy criticism from the Pennsylvania Department of Environmental Protection (see Shale Daily, June 8; May 11).
The Penn State researchers sampled 48 private water wells within 2,500 feet of a Marcellus well pad and 185 wells within 5,000 feet of a Marcellus well pad before and after drilling began.
For the 48 wells closest to Marcellus drilling, "the research found no statistically significant increases in methane levels after drilling and no significant correlation to distance from drilling."
However, the researchers noted that more research needs to be done to identify the source of the methane found in wells, in addition to the potential long term impact of drilling on private wells.
The bipartisan Center for Rural Pennsylvania, an agency of the Pennsylvania General Assembly, funded the study. The group is responsible for a 2009 study that came to similar conclusions.
Under existing Pennsylvania law, operators are liable for contamination incidents at water wells within 1,000 feet of well pads unless they collected water samples before drilling began (a distance set to triple under legislation pending in the state Senate). While operators now typically sample water supplies within this circumference, the Penn State researchers found "a rapid drop-off in testing beyond this distance," and therefore chose to sample wells at 2,500 and 5,000 feet.
The study found increased bromide levels at some water wells after drilling activities, suggesting "more subtle impacts to groundwater and the need for more research," but noted that this was mostly observed within 3,000 feet of drilling sites, suggesting the need for increased setbacks.
Pennsylvania currently requires natural gas wells to be set back 200 feet from private water wells, and legislation pending in the state Senate would increase that distance to 500 feet.
While the findings about methane and bromide are of most interest to natural gas operators worried about being blamed for contamination, the study also found concerning public health issues.
"Approximately 40% of the water wells failed at least one Safe Drinking Water Act water quality standard, most frequently for coliform bacteria, turbidity and manganese, before gas well drilling occurred," the study concluded, calling those findings "similar" to previous studies in Pennsylvania.