OREANDA-NEWS. The US Environmental Protection Agency's (EPA) independent scientific advisers are pushing the agency to revise a major study that found hydraulic fracturing has not caused "widespread, systemic" impacts to drinking water.

That conclusion is ambiguous and appears inconsistent with the observations and data in the rest of the 998-page draft study, EPA's Science Advisory Board said yesterday in a letter that concludes a year-long peer review. Of the 30 scientists on the board, 26 recommended that the agency needed to provide more scientific support for its finding.

"If the EPA retains this conclusion, the EPA should provide quantitative analysis that supports its conclusion that hydraulic fracturing has not led to widespread, systemic impacts on drinking water resources," says the letter to EPA administrator Gina McCarthy.

Four scientists on the advisory board disagreed and said the statement was clear, concise and accurate. But the recommendation from the rest of the board undercuts a finding the oil and gas sector rallied around after EPA published the fracturing study in June 2015. Industry groups hoped the conclusion would finally vindicate the safety of the well stimulation technique, which environmental groups often blamed for harming drinking water quality.

EPA's scientific advisers early on during their year-long review of the study complained that the agency had never said what qualified as a "widespread" impact to drinking water, making the conclusion ambiguous. Another concern the board raised was that the study glossed over instances where actions related to hydraulic fracturing, such as well flowback and waste disposal, had local impacts on drinking water.

Oil and gas industry groups have defended the study's conclusions. The American Petroleum Institute's upstream director Erik Milito today said the "science is clear" that hydraulic fracturing is safe.