A landmark study by the Environmental Protection Agency that concluded fracking causes no widespread harm to drinking water is coming under fire, this time, from the agency's own science advisers.
The EPA's preliminary findings released in June were seen as a vindication of the method used to unlock oil and gas from dense underground rock. A repudiation of the results could reignite the debate over the need for more regulation.
Members of the EPA Science Advisory Board, which reviews major studies by the agency, says the main conclusion — that there's no evidence fracking has led to "widespread, systemic impacts on drinking water" — requires clarification, David Dzombak, a Carnegie Mellon University environmental engineering professor leading the review, said in an e-mail.
The panel that Dzombak leads will release its initial recommendations this month.
"Major findings are ambiguous or are inconsistent with the observations/data presented in the body of the report," the 31 scientists on the panel said in December, in a response to the study.
The scientific panel's recommendations aren't binding, and the EPA is not required to change its findings to accommodate them. But they already are raising questions about the most comprehensive assessment yet of a practice that has driven a domestic oil and gas boom but spawned complaints about water contamination.
An EPA spokeswoman said the agency will use comments from the scientists and the public to "evaluate" possible changes to the report.
A significant change could be a big blow to an industry that is celebrating major policy wins, including the end of trade restrictions that for four decades blocked the export of most raw, unprocessed U.S. crude.
Fracking, also known as hydraulic fracturing, involves pumping water, sand and chemicals underground to free oil and gas trapped inside dense rock formations.
For the study, mandated by Congress, the EPA analyzed more than 950 sources of information, including previously published papers, state reports and the agency's own scientific research, but found no clear evidence that the fracking process could cause chemicals to flow through underground fissures and contaminate drinking water.
When the agency took a broader look at the entire water cycle around fracking, from getting water supplies to disposing of fluid waste, it documented instances where failed wells and above-ground spills might have affected drinking water resources.
Robust peer review by the EPA's Science Advisory Board, established by Congress in 1978, is designed to ensure the integrity of scientific reports, agency spokeswoman Melissa Harrison said in an e-mail.
She said the agency will use the comments from the advisory panel, as well as those submitted by the public, "to evaluate how to augment and revise the draft assessment."
"The final assessment will also reflect relevant literature published since the release of the draft assessment," she said.
Environmentalists want the final document to include more information about alleged contamination near drilling sites in Dimock, Pa.; Parker County, Texas; and Pavillion, Wyo. Those episodes "show how out of step the conclusion is with the body of the report," Clean Water Action oil and gas campaigner John Noel said.
Wyoming's Department of Environmental Quality said in a report last month that there is a "negligible" likelihood that fracking was to blame for any water contamination in Pavillion.
Sen. James Inhofe, R-Okla., said Wyoming's report supports the EPA's broad conclusions.
The review panel could ask the EPA to rescind its top-line finding altogether or clarify it.
Several science advisers reviewing the fracking report said the evidence doesn't support the EPA conclusion about water safety.
Spill data alone "give sufficient pause to reconsider the statement" that there's no evidence of systemic, widespread damage, said panelist Bruce Honeyman, professor emeritus at the Colorado School of Mines.