Methane seeping up underground pathways caused concentrated plumes of gas in the air in Bradford County where the state and a natural gas drilling company are investigating the cause of stray methane bubbling in streams and water wells, according to a study released Tuesday by the Clean Air Council.
The 3½-hour survey conducted for the environmental organization by Gas Safety Inc. in Leroy Twp. on June 8 found average ground-level methane concentrations in a roughly 2-square-mile area at nearly twice normal background levels for the region's air.
The methane concentration in the air spiked to 22 parts per million - more than 10 times the highest background level of 1.95 parts per million - during a roadside survey north of Route 414 and Rockwell Road. The concentration and size of the plume "clearly indicate that one or more methane emissions were present and releasing substantial amounts of methane into the atmosphere," according to the report.
The scientists ruled out nearby farm or other natural sources of so-called biogenic methane, like animal manure, and found no elevated levels downwind of a nearby Chesapeake Energy natural gas well pad that might have indicated leaking from above-ground infrastructure at the site.