Mealey's (June 18, 2015, 4:46 PM EDT) -- WASHINGTON, D.C. — A study scheduled to be published in the forthcoming issue of the Proceedings of the National Academy of Sciences (PNAS) and made available online Sept. 15, 2014, found that, with regard to hydraulic fracturing, when fugitive gas contamination occurs, well integrity problems are most likely associated with casing or cementing issues. The data do not support a finding that fracking “has provided a conduit” to connect deep Marcellus Shale or Barnett Shale formations directly to surface aquifers....