Marcellus Shale development in Pennsylvania and the emerging aquatic contamination concerns

Background/Question/Methods

The rapid expansion of natural gas development in the Marcellus Shale play threatens both surface and ground water quality at multiple points, creating a need to assess and understand the overall costs and benefits of extracting this resource.  Development of the Marcellus Shale creates surface disturbances as a result of land clearing, infrastructure development, and release of contaminants produced from deep groundwater.  In addition the use of hydraulic fracturing poses further environmental threats due to water withdrawals and contamination from fracking-fluid chemicals.  Many gas wells are installed in area where water is already being withdrawn for agriculture, and thus the large amount of water needed for hydrofracking may further stress the resource. Streamflow may be negatively affected if water is dammed to create holding ponds or if water is directly extracted for the fracturing process. The rapid and concentrated extraction of water may create shortages during periods of drought, resulting in altered flow regime and the further degradation of critical habitat for aquatic biota.  Fracturing fluids typically include a combination of additives that serve as gelling agents, surfactants, friction reducers, and pH adjusters.  Produced waters from Marcellus Shale wells pose a threat to surface waters because they typically contain not only hydrofracking additives but also elevated levels of metals, organics, dissolved solids, and radionuclides that occur naturally in deep groundwaters. Onsite waste ponds could overflow, spill, or leach into groundwater and contaminate nearby streams. Even after treatment, total dissolved solids (TDS) in Marcellus Shale produced waters are very high and remaining salts are often disposed of through land application or used as road salts, which can enter surface waters and contribute to increased stream salinization.

Results/Conclusions

Water samples taken from 50 streams in north central Pennsylvania where ongoing Marcellus Shale development is ongoing were analyzed for a variety of contaminants typically associated with Marcellus Shale natural gas development including metals, organics, nutrients, dissolved solids, and radionuclides. Water samples are being tested for a variety of cations including: Ba, Sr, Na, K, Ca, Mg, Al, Fe, and Mn. In addition samples are also being tested for anions including: Cl, Br, SO₄. and several nutrients including: ammonia, nitrate+nitrite-N, soluble reactive phos., and total P.