DIMOCK TOWNSHIP - A leaked Environmental Protection Agency (EPA) slideshow presentation showed natural gas drilling could cause "significant damage" to drinking water through migrating methane, something the federal agency did not look for when it spent months in the heavily drilled Dimock Township in 2011-12.
The slideshow revealed the federal agency was told methane migration from natural gas drilling posed a threat to drinking water, a main concern of residents of Dimock. Environmental groups called on the EPA to revisit the Susquehanna County township.
"The PowerPoint raises important questions about how EPA came to its determination that the water in Dimock was OK to drink when it points to the possibility of significant long-term contamination," said Kate Sindig of the Natural Resources Defense Council.
The slideshow discusses isotopic analysis - a means of determining the origin of natural gas in water. The isotopic analysis presented in the slideshow could distinguish between gas from shallow pools and those from deep rock formations.
David Yoxtheimer of Penn State University's Marcellus Center for Outreach and Research said the isotope analysis discussed in the EPA presentation is less than exact and could result in a false positive.
"The isotopic signatures of some of these gases are close and overlap," he said. "It's not a slam-dunk diagnostic tool."
The EPA said the slideshow was the work of an on-scene coordinator. It has not been peer reviewed and does not reflect the official agency position.
"The EPA will consider this information, along with tens of thousands of other data points, as a part of its ongoing and comprehensive National Study on the Potential Impacts of Hydraulic Fracturing," said EPA spokeswoman Alisha Johnson.
The leaked presentation emerged almost exactly one year after the EPA closed its investigation into Dimock water contamination saying "sampling and an evaluation of the particular circumstances at each home did not indicate levels of contaminants that would give EPA reason to take further action."
While methane was central to the concerns of residents, evidenced by dramatic images of water from faucets flaring flames, the EPA tests were limited to contaminants in the Safe Drinking Water Act, which do not include methane. The agency scrutinized levels of hazardous substances such as arsenic, barium and manganese and declared them within safe levels in Dimock. In some cases, water treatment brought water back into safe levels. The EPA declared Cabot Oil & Gas no longer had to provide drinking water to residents. The industry touted the findings as absolving drilling activity of connection to water contamination.
Methane, in fact, is not considered a contaminant, noted Sindig, and no federal agency has established levels that are safe or pose a threat. But the Natural Resources Defense Council believes it should be looked at.
The EPA viewed water quality in the most narrow sense instead of looking at the broader context of the potential long term impacts, Sindig said.
While not identified as a serious contaminant, studies show that methane enhances other contaminants in water, Sindig said.
"We think the public deserves is an explanation. Why didn't the agency didn't go further in light of what was being presented by to them?"
Cabot has long held that methane in Dimock groundwater was naturally occurring and existed long before drilling began in the region.
"The drinking water in Dimock has been thoroughly and repeatedly tested over the past several years," a Cabot statement read. "The Environmental Protection Agency, state authorities and third-party experts have all tested the water."
Yoxtheimer said cases of natural gas migration have decreased as the industry gets a more refined knowledge of the geology. Well construction improved thanks to regulations passed in 2011. Pre-drilling water testing and baseline groundwater monitoring are commonplace, he said, and perhaps should include isotopic analysis of methane.