An article by Daniel Rozell and Sheldon Reaven on water pollution risks associated with natural gas extraction from the Marcellus shale has been published in Risk Analysis. According to the authors:
"The public policy decision to pursue natural gas extraction from the Marcellus Shale involves several potential risks and benefits. The crucial unknown is the potential risk of water contamination from hydraulic fracturing."
"There are many types of water contamination that can result from the shale gas extraction process,including: gases (e.g., methane and radon), liquids (e.g., hydraulic fracturing fluids), and solids (e.g., drill cuttings). Because the hydraulic fracturing process generates primarily liquid waste products, this risk assessment only considers water contamination from drilling and hydraulic fracturing fluids."
"Given recent public attention to the potential environmental risks of hydraulic fracturing, drillers have been making the transition to hydraulic fracturing components that are considered largely benign. However, even a benign hydraulic fracturing fluid is contaminated once it comes in contact with the Marcellus Shale. Recovered hydraulic fracturing fluid contains numerous materials from the Marcellus Shale formation in excess of drinking water standards, including: sodium, chloride, bromide, arsenic, barium, and naturally occurring radioactive materials such as uranium, radium, and radon. Thus, any drilling or fracturing fluid is suspect for the purposes of this study."
The article identifies 5 sources of contamination:
- Fracturing fluid transportation spills
- Well casing failures
- Underground fluid migration through fractured rock
- Drilling site surface leaks and spills
- Wastewater treatment and disposal