A study done by researchers at Penn State University for the Center for Rural Pennsylvania sampled 233 water wells in 20 counties for impacts from gas drilling. http://www.rural.palegislature.us/documents/reports/Marcellus_and_drinking_water_2011.pdf. What are its findings?
In the Marcellus wars, it probably will be spun in both directions. To avoid spinning, I will quote key sections from the Executive Summary.
"In this study, statistical analyses of post-drilling versus pre-drilling water chemistry did not suggest major influences from gas drilling or hydrofracturing (fracking) on nearby water wells, when considering changes in potential pollutants that are most prominent in drilling waste fluids." (Page 4)
Unlike the Duke Study, the PSU study found no correlation between distance from drilling and methane contamination of water wells. "When comparing dissolved methane concentrations in the 48 water wells that were sampled both before and after drilling...the research found no statistically significant increases in methane levels after drilling and no significant correlation to distance from drilling." (Page 4).
I suspect the different outcomes between the Duke and PSU studies may have a lot to do with the county location of wells. Duke conducted its analysis in the few counties where confirmed gas migration cases are concentrated. PSU's study used water wells in 20 counties.
The researchers further state, "The research found that bromide levels in some water wells increased after the drilling and/or fracking. These increases may suggest more subtle impacts to groundwater and the need for more research. Bromide increases appeared to be mostly related to the drilling process. A small number of water wells also appeared to be affected by the disturbances due to drilling as evidence by sediment and/or metals increases that were noticeable to the water supply owner and confirmed by water testing results. Increased bromide concentrations in water wells along with sporadic sediment and metals increases were observed within 3,000 feet of Marcellus gas well sites in this study." (Page 4). See further discussion at pages 16 to 19.
The researchers speculate the source of the bromide may be drilling muds used in the drilling phase and kept at well pads. The researchers call for more research on this issue. Whatever the source, stopping it should be the top priority.
The researchers also found that 40% of the water wells tested prior to drilling "failed at least one Safe Drinking Water Act water quality standard, most frequently for coliform bacteria, turbidity, and manganese..." The researchers also found methane in 20% of the pre-drilling water wells, "although levels were generally far below any advisory levels."
The Center for Rural Pennsylvania is an agency of the Pennsylvania General Assembly. I recommend reading the report.