A definitive study published by the National Academy of Sciences has concluded that horizontal drilling and hydraulic fracturing to extract shale gas and oil do not, in themselves, cause contamination of drinking-water sources. However, faulty cementation and construction techniques, such as improperly cementing well casings and linings, can potentially trigger migration of methane into groundwater wells and aquifers, according to the report, published in the Sept. 12 issue of the Proceedings of the National Academy of Sciences.
The study's conclusions are significant because fracking remains controversial, polarizing opinions on whether the practice causes contamination of drinking-water wells and aquifers near drilling sites. A handful of states and cities, including New York state and Fort Collins, Colo., have put in place temporary moratoria on fracking.