In this June 25, 2012 file photo, a crew works on a gas drilling rig at a well site for shale based natural gas in Zelienople, Pa. (Photo: AP/Keith Srakocic)
Tests and scientific experts have already claimed that many health and environmental concerns tied to hydraulic fracturing for natural gas, often voiced by opponents of the process, lack scientific backing. Now, yet another study has found that wells near fracking sites did not experience water contamination.
Duke University and members of the U.S. Geological Survey examined 127 drinking water wells for evidence of pollution from methane gas or chemicals. With more than 4,000 new gas wells drilled in Arkansas' Fayetteville Shale since 2004, researchers were looking for the presence of contamination from drilling, or from naturally occurring gas or ultra-salty liquids that seep up through pre-existing faults.
What they found was that Arkansas homeowners "typically had good water quality, regardless of whether they were near shale gas development," Robert Jackson, a professor of environmental sciences at Duke, said in a statement.
Romanian protesters holds a banner during a demonstration against hydraulic fracturing (fracking) in Bucharest April 4, 2013. Around 300 protesters gathered in Bucharest's University Square in protest against the drilling technique, which uses high pressure injections of water, sand and chemicals to crack open rock and release oil and gas trapped inside. Hundreds of Romanians rallied in several cities to protest against shale gas drilling, voicing concerns over environmental pollution and health hazards. (Photo: DANIEL MIHAILESCU/AFP/Getty Images)
"Only a fraction of the groundwater samples we collected contained dissolved methane, mostly in low concentrations, and the isotopic fingerprint of the carbon in the methane in our samples was different from the carbon in deep shale gas in all but two cases," Avner Vengosh, professor of geochemistry and water quality at Duke's Nicholas School of the Environment, said, according to the university's press release.
This would indicate that the methane resulted from biological activity not from shale gas contamination, Vengosh said.
The most passionate critics and supporters of fracking often describe the process in extremes, suggesting it is either inherently dangerous for the environment or that it poses virtually no risk at all. But Vengosh noted that generalizations about fracking in Arkansas, Pennsylvania and Colorado don't make scientific sense.
Environmentalists stage a protest to coincide with a fundraising event by U.S. President Barack Obama on May 13, 2013 in New York City. Hundreds of demonstrators marched to protest the building of oil pipelines and calling for the end of hydraulic fracking for oil and gas. (Photo: Getty Images/John Moore)
"Each basin will have its own dynamics and its own rules," he said of the possibility of contamination, adding that differences in well construction and regulations play a role, too.
In the contentious debate over fracking, the Duke team has shown a willingness to report both positive and negative studies. In 2011, Duke researchers found higher concentrations of methane gas near drilling sites in Pennsylvania, and state regulators denounced the findings even as environmental groups cheered them.
During fracking, large volumes of water, along with sand and hazardous chemicals, are injected into the ground to break rock apart and free the oil and gas trapped inside. In some areas fracking has been blamed for air pollution and gas leaks that have ruined well water, but the Obama administration and many state regulators say the practice is safe when done properly.
A poster projecting job and economic growth related to "fracking" is used by lawmakers while answering questions from reporters concerning oil drilling in Illinois, at the Illinois State Capitol Tuesday, April 30, 2013, in Springfield, Ill. (Photo: AP/Seth Perlman)
Deb Nardone, a spokeswoman for the Sierra Club, said that there "are going to be geological differences" in different areas, the Associated Press reported. But she said what that means is that research should be done in each area before drilling begins, to identify possible problems. Nardone also questioned whether over time the Arkansas water wells might start to show pollution from drilling. "It would be interesting to come back at this after five years," she said of the study.
One representative from industry agreed with some aspects of the Arkansas study, but questioned others.
"It does clearly speak to the need to think about these things from a regional and local perspective," said Andrew Place, the interim director of the Center for Sustainable Shale Development, a Pittsburgh-based partnership between industry, environmental groups, and philanthropies that is promoting higher standards for drilling in the Marcellus Shale, which covers Pennsylvania, Ohio, West Virginia and New York.
Place questioned the suggestion that the Marcellus Shale is uniquely different from the Fayetteville Shale, noting that Marcellus wells are typically two or three times the depth of those in Arkansas. Place said there are 6,000 feet or more of different rock layers between Marcellus gas wells and surface aquifers, and suggested that makes a "pretty compelling" case that pollution doesn't migrate unless wells are improperly constructed.
"Well casing can be done right," Place said.
Vengosh said the Arkansas findings don't mean that contamination can't happen, since faulty well construction or areas with different geology could cause different results.
The Associated Press contributed to this report.