A private firm hired by Chesapeake Energy Corp. has determined that drinking water sources tested by the U.S. Environmental Protection Agency (EPA) in Bradford County, PA, show no signs of any adverse impact from Marcellus Shale operations.

In a 360-page report, Weston Solutions Inc., an adviser on environmental and energy issues based in West Chester, PA, said it analyzed split samples that were collected by Chesapeake and the EPA from 14 water wells and one spring last October and November as part of the EPA's national study on hydraulic fracturing (fracking).

"Based upon review of the analytical data for each of the 14 water wells and one spring...and subsequent comparison of these results with regional historical and baseline water quality databases, [we conclude] that these 15 water sources do not appear to be impacted by natural gas drilling or production activities, including hydraulic stimulation," the report said, adding that with few exceptions, "there are no significant increases in inorganic parameters when comparing current analyses with baseline conditions or from historical databases.

"None of the wells show significant increases in dissolved methane when comparing current analyses with baseline conditions or area-wide baseline databases."

Weston said organic compounds were detected in some of the wells but added that they "are not attributable to natural gas drilling or production activities, including hydraulic stimulation."

On Tuesday, Chesapeake said Weston's findings have been submitted to the EPA, the Pennsylvania Department of Environmental Protection and the landowners involved in the study.

"[We hope] the EPA will find Weston's report useful in meeting Congress' request for independent sources of information to be included in the agency's influential scientific assessment regarding hydraulic fracturing," Chesapeake said.

Bradford and neighboring Susquehanna County form one of five testing sites for retrospective case studies across the nation to determine whether fracking has impacted drinking water sources (see Shale Daily, June 24, 2011). The other four are to analyze the Bakken Shale (Bildeer and Dunn counties, ND); Barnett Shale (Wise and Denton counties, TX); Marcellus Shale (Washington County); and Raton Basin (Las Animas County, CO).

Marcellus drilling activity has dipped and leveled off after reaching a peak of more than 170 rigs in late December 2011. According to NGI's Unconventional Rig Count, for the week ending May 25, 138 rigs were drilling for oil and gas in the Marcellus Shale, which is down five rigs from both the previous week and the corresponding week one year ago.