Five years ago, Congress asked the Environmental Protection Agency to evaluate the potential for hydraulic fracturing to harm the U.S. drinking water supply. Earlier this month, the agency released its long-awaited draft report and concluded that the controversial oil and natural gas extraction technique has had no “widespread, systemic impact” on water resources.
EPA warned, however, that the technology commonly known as fracking can pose water quality risks in specific situations. The agency identified several areas of “potential vulnerability,” including spills of the fluids used in fracking operations, inadequate treatment and disposal of wastewater, and poorly constructed wells.
Although water quality problems have occurred at some well sites, the agency said there have been relatively few issues.
Thomas A. Burke, deputy administrator for EPA’s Office of Research & Development, stressed that the study focused on “how we can best protect our water resources. It’s not a question of safe or unsafe.”
Fracking involves injecting millions of gallons of water mixed with other chemicals and sand into underground geologic formations at high pressure, breaking apart the rock and releasing trapped oil and gas. Trade groups representing the fossil-fuel industry say EPA’s study confirms that there’s nothing inherently unsafe about fracking.
But use of the technology has generated an intense backlash among environmental activists, who say fracking can pollute nearby freshwater supplies. They discount EPA’s study, charging it is too narrow in scope and based largely on theoretical modeling.
“The lack of actual field data calls into question how definitive EPA can actually be in suggesting that there isn’t evidence of systemic water contamination,” says Mark Brownstein, vice president for the climate and energy program at the Environmental Defense Fund. “I think that anyone who reads this study and thinks that this issue has been put to bed is sadly mistaken.”
One issue that EPA had indicated it would examine is the use of chemical tracers for monitoring fracking fluids. The simple hydrological method was included in the agency’s November 2011 study plan on the basis that a chemically stable tracer mixed in with a fracking fluid might offer some insight about its environmental fate.
“The tracers may be used to determine if fracturing fluid migrates from the targeted formation to an aquifer via existing natural or man-made pathways,” the agency wrote in the 2011 plan. But in the final report, tracers are mostly absent: Only one case study includes a perfluorocarbon tracer.
“Tracers would be a blessing and a curse to the industry,” says Briana Mordick, a staff scientist with the Natural Resources Defense Council, an environmental group. The fracking industry would “have a more definitive way to prove that they aren’t involved” in water supply contamination, she says. “But it also could make it really hard to deny that they aren’t responsible.”
“The status quo right now is that it can be really difficult to distinguish contamination caused by oil and gas from contamination from natural causes,” she adds.
The use of fluorescent dyes, salts, and stable isotopes has been commonplace for decades in hydrology to track surface and groundwater. “People are worried that contamination can get out of shale gas wells somehow and get into groundwater,” and a tracer seems like a direct way of figuring that out, says Susan L. Brantley, a geochemist at Pennsylvania State University.
What Brantley and other geochemists do, she says, is look for natural tracers such as strontium, barium, and bromine that are already in the water they’re sampling.
“People have talked about the possibility of using tracers for a long time, but I’m not sure it’s being done in any real way,” says Avner Vengosh, an environmental geochemist at Duke University.
Like Brantley, Vengosh searches for natural tracers in fracking wastewater that can give him clues to the water’s source (C&EN, March 16, page 8). “Why would the industry let someone put in a tracer to find wrongdoing?” he asks.
Although there is little available evidence to suggest that tracers are being used widely by the oil and gas industry to track the movement of fracking fluids, a niche industry has grown around tracers used to improve the efficiency of frack jobs.
“This is a way for oil and gas to be more efficient in production, and for oil and gas producers to know more about what’s happening with their wells,” says Justine C. Kmiecik, chief executive officer of BaseTrace, a start-up located in Research Triangle Park, N.C. (C&EN, May 12, 2014, page 31).
C&EN reached out to a number of energy industry representatives, but all declined to comment on the use of tracer technology.
EPA’s fracking study will be reviewed by a research advisory panel comprising industry and academic scientists. Brantley is a member of that panel but says she is not authorized to speak about the study.