David Biello over at Scientific American had a story in 2011 that looked at research establishing a link between methane contamination in well water and nearby hydraulic fracturing of shale rock. The research came out of Duke University and was published online in Proceedings of the National Academy of Sciences. The Duke researchers analyzed water samples from 60 wells located within a kilometre of active shale-gas drilling operations — specifically, the Marcellus and Utica shale formations of northeastern Pennsylvania and upstate New York. They found that “average and maximum methane concentrations in drinking-water wells increased with proximity to the nearest gas well” and were at levels high enough to pose “a potential explosion hazard.”
As Biello pointed out, this “marks the first time that drinking water contamination has been definitely linked to fracking.” His story, which is old but I’ve just come across, is well worth the read. He makes clear that while a small amount of methane isn’t uncommon in most aquifers in the region, the researchers were able to distinguish between “new” methane being produced by the ongoing decay of biological material and “old” methane trapped and released from fossil rock. This was done by measuring the ratio of radioactive carbon present in the methane. Very cool.