Courtesy of the EPA
When fracking wastewater is not properly discharged, it has the potential to contaminate. A stream of wastewater flows from an oilfield on the Wind River Reservation in Wyoming. Credit: Courtesy of the EPA

The oil and gas industry has long claimed that there is no evidence that hydraulic fracturing has contaminated drinking water. But a new, major Environmental Protection Agency assessment has determined that fracking and another widely used drilling technique called horizontal drilling have the potential to contaminate drinking water.

The study also identified the greatest risks to drinking water, including spills, water withdrawals, wastewater releases and migration of gas and oil underground.

The nearly 1,000-page EPA study—a draft awaiting public comment and scientific review—found no evidence that “widespread” pollution of drinking water has occurred from these drilling techniques, which have driven a renaissance of the U.S. oil and gas industries over recent years. The number of known cases of well contamination and other impacts to drinking water sources was small compared to the estimated 25,000 to 30,000 new wells that were drilled and hydraulically fractured between 2011 and 2014, and the many more older wells that also were fracked, the study states.

Industry groups say this conclusion confirms the safety of their operations. But the EPA study concedes that a lack of sufficient scientific research may explain why the agency failed to find widespread impacts.

“That means they don’t know how often these things occur,” said Rob Jackson, a Stanford University environmental science professor.

Even after several years of work, the federal EPA failed to answer questions about the impacts of new drilling techniques that caused panic in communities across the country.

When the EPA launched its study of hydraulic fracturing and drinking water in 2011, scientists and environmental advocates expected it would fill in the knowledge gaps.

“This was supposed to be their job,” said Jackson, who is a leading researcher on the issue. “My frustration with the report is they left the difficult stuff out. They didn’t sink their teeth into the meat of this issue, into the controversial parts of this issue. That’s what we hoped EPA would do. Who else has the resource to do it?”

The study is less conclusive than originally envisioned, in part because the EPA failed to reach agreement with industry to do the kinds of studies scientists and the federal government believe are necessary. These studies would test drinking water sources before and after companies hydraulically fracture wells nearby. The EPA’s new assessment repeatedly cites the need for such studies.

Along the way, other significant efforts by the EPA to seek answers got derailed. The EPA investigated a possible case of well contamination in Pavillion, Wyo. But as reported, after EPA’s original findings linked hydraulic fracturing to water contamination, industry interests challenged agency scientists’ methodology and, in 2013, the agency abruptly dropped its research. The EPA backed out of investigations in Texas and Pennsylvania as well.

Still, the EPA’s new assessment, which draws from hundreds of reports and data sources, does have merit in pinpointing the riskiest steps for drinking water in modern drilling and production processes:

When companies withdraw large quantities of fresh water for hydraulic fracturing during times or in areas with low water availability.

When companies spill hydraulic fracturing fluids and produced water. (In Colorado, the state with the second-most wells hydraulically fractured over the period the EPA studied, the spill rate was one every 100 wells.)

When companies fracture directly into underground drinking water resources.

When liquids and gases migrate below ground. (This can be caused by intense pressures used in hydraulic fracturing, poorly constructed wells, or when the casing or cement used in wells degrade.)

When companies fail to adequately treat or properly discharge of wastewater, including when, as reported, they release that wastewater directly onto the land or into streams.

These weaknesses were illuminated by retrospective studies the EPA conducted that examined suspected contamination of drinking water from hydraulic fracturing in five locations including the Colorado’s Raton Basin and North Dakota’s Bakken Shale.

In Killdeer, North Dakota, a blowout during the hydraulic fracturing of an oil well in 2010 caused the release of fracking fluids. Drinking water wells did not show signs of contamination, but two monitoring wells found both brine and tert-butyl alcohol in the Killdeer aquifer. An EPA analysis determined the only possible source of this contamination was the 2010 blowout.

The EPA failed to definitively link contamination to hydraulic fracturing in other cases. For instance, people in Colorado’s Las Animas and Huerfano counties had complained about a change of appearance, odor and taste of water from their wells. The EPA study showed levels of dissolved methane in domestic wells that were consistent with natural background levels in the area. However, in one sampling area, two years after hydraulic fracturing, gas migrated into a shallow aquifer used for drinking water. The EPA and other researchers have been unable to prove definitively that the gas migrated because of the hydraulic fracturing and not because of natural causes.

The new assessment repeatedly stressed how holes in research and data often make it difficult to make definitive conclusions. For example, the EPA analyzed 151 spills of hydraulic fracturing fluid in 11 states and found that the most common cause was equipment failure, particularly the failure of valves and blowout preventers, devices intended to prevent uncontrolled releases of oil and gas. However, EPA stressed data was lacking to analyze spills. For instance, only two states, Colorado and Pennsylvania, provided statistics on spill frequency.

Other gaps noted in the EPA report included the dearth of science on the fate of the vast quantities of fracking fluids that don’t flow back to the surface, and the lack of data on how much fracking takes place in formations that also contain drinking water.

Congress requested the assessment in response to communities’ concerns and questions about the safety of the industry. The EPA estimates that public drinking-water systems that serve more than 8.6 million people were located within a mile of at least one well hydraulically fractured in 2013 alone. That doesn’t include the many private wells located near such well sites.

Congressional Republicans said the study affirms that the industry needs no additional federal regulation.

“We all want clean water, and we all want affordable energy, and today, the administration confirmed we can have both,” said Fred Upton, R-Michigan, chairman of the House Energy and Commerce Committee. “The (Obama) administration should now reconsider the burdensome regulations it intends to place on hydraulic fracturing on federal lands, and should certainly refrain from any notion of broader federal involvement in an issue that states and communities are safely managing.”

But Rep. Raul Grijalva, D-Arizona, took away another message: “Irresponsible oil and gas development puts water quality at risk for millions of Americans, and no amount of spin can change that.”

Environmental groups and scientists stressed that the report underscores how many questions remain. “We look at this report as very much the beginning of a process to understand what the impacts of unconventional oil and gas are to the water cycle,” said Mark Brownstein, of the Environmental Defense Fund.

EPA’s assessment is open for public comment while the document undergoes review by the EPA’s Scientific Advisory Board, which plans public teleconferences and meetings in September and October.

This piece originally appeared in High Country News.