Fracking has not led to widespread pollution of drinking water, the U.S. Environmental Protection Agency said on Thursday in a long-awaited draft study, but warned that certain drilling activities could pose risks.
The study, requested by Congress and five years in the making, found specific instances where water sources were affected by hydraulic fracturing, the injection of large amounts of sand, water and chemicals deep underground to crack open rock formations holding natural gas and oil.
The EPA also found risks to drinking water in formations where fracking occurred and where water supplies were scarce.
U.S. EPA finds fracking poses no 'widespread risk' to drinking water
FILE - In this Feb. 23, 2012 file photo, signs opposing the hydraulic fracturing process of drilling for gas, or "fracking" are posted in Evans City, Pa. The Obama administration said Friday it will for the first time require companies drilling for oil and natural gas on public and Indian lands to publicly disclose chemicals used in hydraulic fracturing operations. The proposed "fracking" rules also set standards for proper construction of wells and wastewater disposal. (AP Photo/Keith Srakocic, File)
In this photo made on Saturday, Feb. 16, 2013, a pumping truck is seen near the well where pumps move a brine water below the surface in a hydraulic fracturing process to release natural gas from shale deposits in Zelienople, Pa. (AP Photo/Keith Srakocic)
FILE - In this Feb. 17, 2012 file photo, the Pittsburgh skyline rises above the waters of the Ohio River, which starts at the confluence of the Monongahela and Allegheny Rivers in Pittsburgh. The U.S. Coast Guard wants to allow barges filled with fracking wastewater to ply the nationâs rivers on their way toward disposal, an idea thatâs raising alarm among environmentalists but could also provide long-elusive information on what exactly the toxic brews contain. (AP Photo/Keith Srakocic, File)
Demonstrators march near the U.S. Capitol against the fracking gas exports in Washington on Sunday, July 13, 2014. Activists from across the Mid-Atlantic region and beyond rallied against the gas industry's controversial push to export fracked and liquefied natural gas (LNG) from U.S. coastlines. (AP Photo/Jose Luis Magana)
In this March 25, 2014 photo, perforating tools, used to create fractures in the rock, are lowered into one of six wells during a roughly two-week hydraulic fracturing operation at an Encana Corp. well pad near Mead, Colo. Proponents of hydraulic fracturing point to the economic benefits from vast amounts of formerly inaccessible hydrocarbons that now can be extracted with hydraulic fracturing. Opponents point to potential environmental impacts, with some critics acknowledging that some fracking operations are far cleaner than others. (AP Photo/Brennan Linsley)
In this March 25, 2014 photo, workers keep an eye on well heads during a hydraulic fracturing operation at an Encana Corp. oil well, near Mead, Colo. The first experimental use of hydraulic fracturing was in 1947, and more than 1 million U.S. oil and oil wells have been fracked since, according to the American Petroleum Institute. The National Petroleum Council estimates that up to 80 percent of natural oil wells drilled in the next decade will require hydraulic fracturing. (AP Photo/Brennan Linsley)
In this March 25, 2014 photo, a worker adjusts hoses during a hydraulic fracturing operation at an Encana Corp. oil well, near Mead, Colo. The first experimental use of hydraulic fracturing was in 1947, and more than 1 million U.S. oil and oil wells have been fracked since, according to the American Petroleum Institute. The National Petroleum Council estimates that up to 80 percent of natural oil wells drilled in the next decade will require hydraulic fracturing. (AP Photo/Brennan Linsley)
This Thursday March 6, 2014 photo shows the setting sun behind pumpjacks operating at the Inglewood oil fields in the Baldwin Hills area of Los Angeles. The Los Angeles City Council has taken steps to prohibit hydraulic fracturing, or fracking. (AP Photo/Richard Vogel)
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But overall, the EPA saw little impact to water supplies from the thousands of fracking wells across the country.
The draft study will give state regulators, local communities and companies "a critical resource to identify how best to protect public health and their drinking water resources," said EPA science adviser Thomas Burke.
Other vulnerabilities to water supplies from fracking-related activities can result from inadequately cased or cemented wells that leak gases and liquids underground when inadequately treated wastewater is discharged into the resource, the study said.
The study contained a compilation of more than 900 references and citations, as well as agency-conducted research that has undergone "extensive peer review," Burke told reporters.
Environmental groups cast doubt on the EPA's findings.
"There are still significant gaps in the scientific understanding of fracking," said Amy Mall, senior policy analyst at the Natural Resources Defense Council. "This study is site-specific and limited, as EPA has explained, which makes it impossible to fully understand all the risks at this time."
Mall said, however, that unlike in the past updates on the study, the EPA this time acknowledged there are some effects on water.
Mark Brownstein, vice president of the Environmental Defense Fund, said the process of fracking itself is just one risk factor.
"Ongoing physical integrity of the wells and handling the millions of gallons of wastewater coming back to the surface after fracking, over the lifetime of each well, are even bigger challenges," he said. "Relentless focus on these issues by regulators and industry is critical."
The EPA's Burke told reporters that oil and gas companies were a major source of information on locations and practices, and that the agency had a "very cooperative relationship with industry."
Energy groups embraced the EPA's findings, saying they backed up other studies by the Energy Department and U.S. Geological Survey.
"The report contradicts the most prevalent claim from anti-fracking activists, which have made 'water contamination' the very foundation of their campaign against hydraulic fracturing," said Katie Brown, spokeswoman for the Independent Petroleum Association of America's Energy In Depth arm.
The American Petroleum Institute said the study affirmed the sector's record of "continuous safety improvements."
The draft study will undergo external review by the public and the agency's Science Advisory Board and is due to complete the process by next year.
(Reporting by Valerie Volcovici and Timothy Gardner; Editing by Lisa Von Ahn)