The results were published online Monday in the Proceedings of the National Academy of Sciences.
Sheila Olmstead, Lucija Muehlenbachs, Jhih-Shyang Shih, Ziyan Chu, and Alan Krupnick relied upon more than 20,000 surface water quality observations taken over 11 years in Pennsylvania to estimate the effects of shale gas development on downstream water quality through 2011.
The results indicate statistically significant water quality impacts from wastewater sent to treatment plants and runoff from well pad development. The study found no systematic statistical evidence of spills or leaks of flowback and produced water from shale gas wells into waterways.
Specifically:
The upstream treatment and release of shale gas wastewater by treatment plants raised downstream chloride concentrations in surface water, but not TSS concentrations. The researchers estimated that an increase of 1 upstream waste treatment facility accepting shale gas waste raises downstream chloride concentrations in a watershed by about 7 percent.
The presence of well pads upstream raised the concentration of TSS, but not chloride. An additional 18 well pads upstream increases downstream TSS concentrations in a watershed by about 5 percent.
In 2011 Pennsylvania increased the stringency of wastewater treatment standards for several water pollutants and placed a voluntary ban on the shipment of shale gas waste to municipal sewage treatment plants and some industrial wastewater treatment plants. These changes partially address the chloride concentrations impacts estimated by this study.
The finding of measurable downstream impacts on TSS from shale gas infrastructure in only these first years of burgeoning shale gas development in Pennsylvania suggests that land management issues may be important as well.
“While much of the public concern and controversy around shale gas development has focused on its impacts on groundwater, our findings indicate that there are risks to rivers and streams,” said lead author, Sheila M. Olmstead.
The results are also consistent with a recent survey of experts carried out by scholars at RFF’s Center for Energy Economics and Policy. “We found a high level of agreement among the experts we surveyed that surface water impacts should be a high priority for risk mitigation,” said CEEP Director and survey lead author Alan Krupnick. “This study supports that perspective.”
Study details:
-- The first large-scale statistical examination of the extent to which shale gas development affects surface water quality.-- 20,283 water quality observations in Pennsylvania (2000 to 2011).
-- The research design exploits spatial variation in the location of water quality monitors, shale gas wells, and wastewater treatment facilities that have accepted shale gas waste along with inter-temporal variation generated by the timing of well development and waste shipments.
-- The effects of shale gas activity on water quality are estimated using regression analysis controlling for rainfall, general trends over time, intra-annual variation by watershed, and time-constant characteristics of the location of the monitors.
A copy of the study is available online.