Water Pollution Risk Associated with Natural Gas Extraction from the Marcellus Shale

Water Pollution Risk Associated with Natural Gas Extraction from the Marcellus Shale by Daniel J. Rozell and Sheldon J. Reaven, August 2012, Article first published online: December 28, 2011, Society for Risk Analysis
DOI: 10.1111/j.1539-6924.2011.01757.x
The study model identified five pathways of water contamination: transportation spills, well casing leaks, leaks through fractured rock, drilling site discharge, and wastewater disposal. Probability boxes were generated for each pathway. The potential contamination risk and epistemic uncertainty associated with hydraulic fracturing wastewater disposal was several orders of magnitude larger than the other pathways. Even in a best-case scenario, it was very likely that an individual well would release at least 200 m3 of contaminated fluids. … According to PA-DEP records(53) from July 2009 to June 2010, there were about 4,000 permitted Marcellus wells in PA. Of these wells, about 850 wells were producing gas, 400 wells were not producing, and 2,800 wells were planned or in process. During this same time, 630 environmental, health, and safety violations were issued for Marcellus wells in PA, of which approximately half were for discharges up to 60 m3 or for potential to cause discharge. These data are acknowledged by public officials to be underreported.(42) … Although some well operators recycle and reuse hydraulic fracturing fluids for multiple wells, most operators do not due to the cost of separation and filtration.(54) Instead, the used hydraulic fracturing fluid is transported to a wastewater treatment facility and discharged to streams. … Municipal wastewater treatment facilities are not designed to handle hydraulic fracturing wastewater containing high concentrations of salts or radioactivity two or three orders of magnitude in excess of federal drinking water standards.(42,56) As a result, high salinity and dissolved solids in Appalachian rivers have been associated with the disposal of Marcellus Shale hydraulic fracturing wastewater after standard wastewater treatment.(57) The amount of wastewater treated in public sewage facilities seems to be underreported and actual levels may be as high as 50%.