Methane that caused a blast in a Dimock water well, forced a family to evacuate a Terry Twp. home and bubbled up in the Susquehanna River was unsettled from porous rock between the surface and the Marcellus Shale as drillers searched for deep gas.
In high-profile cases affecting 35 drinking-water wells in Bradford and Susquehanna counties, state investigators have linked the stray methane to faulty drilling practices that did not account for the gas-rich and highly fractured shallow geology in Northeast Pennsylvania - a hazard that has made the region one of the most difficult places in the state to drill safely into the Marcellus Shale.
As shale gas drilling has increased in Pennsylvania, so has the prevalence of methane migrating into water supplies as a result of the exploration.
The number of new Marcellus wells nearly doubled between 2009 and 2010, but the rate of methane migration more than quintupled: In 2009, there were 1.26 cases of gas migrating into groundwater for every 1,000 new Marcellus wells drilled, according to the Department of Environmental Protection. Last year, there were more than seven cases for every 1,000 new wells.