Drinking-water wells in Pennsylvania close to natural gas sites do not face a greater risk of methane contamination than those farther away, according to a new study published in Environmental Science & Technology (ES&T). But the study is now being called into question because of its methodology and some undisclosed ties to energy giant Chesapeake Energy.
The findings contradict recent studies that identified a correlation between proximity to natural gas wells and higher methane levels in well water. The new study analyzed more than 11,000 water samples collected by Chesapeake and provided to researchers.
Methane is the main component of natural gas and is not toxic for humans. But if the gas escapes from water taps and accumulates in confined spaces such as basements it poses a risk of explosion.
"We found no statistically significant relationship between dissolved methane concentrations in groundwater from domestic water wells and proximity to pre-existing oil or gas wells," wrote the authors, led by Donald Siegel, chairman of earth sciences at Syracuse University. "Previous analyses used small sample sets compared to the population of domestic wells available, which may explain the difference in prior findings compared to ours."
Industry welcomed the Siegel study, the largest ever evaluating methane in water near gas development, as evidence of the safety of hydraulic fracturing. The production method is driving the gas boom in Pennsylvania's Marcellus Shale and across the country.
But scientists not involved in the study reacted cautiously because of its methodology, in which Chesapeake sampled treated water and used a methane sampling method that major water labs don't use.
Further, the study authors failed to divulge the scope of their ties to Chesapeake, including fees the company paid to Siegel to carry out his research. One of the paper's four co-authors, Bert Smith, worked for Chesapeake during some of the period when the study took place, which also wasn't disclosed. Smith works for the company today. The paper only acknowledges that Chesapeake provided the dataset.
After questions from InsideClimate News, a spokesman for ES&T said its editors would review whether their disclosure conformed to its ethics guidelines. The peer-reviewed journal requires a paper's lead author to submit a statement that describes "all potential sources of bias, including affiliations, funding sources, and financial or management relationships, that may constitute conflicts of interest."
Siegel said that he considered the disclosure on the paper adequate, and that his analysis was not influenced by Chesapeake. "I've done work for any number of environmental groups, and I've worked for industry," he said. "I go where the science is. I have no hidden agenda here." He declined to specify the fee amount he received, other than to say "I didn't get rich."
Chesapeake, the nation's second-largest producer of natural gas, shared its water samples from northeastern Pennsylvania with Siegel about three years ago because he had gained a reputation among oil and gas companies as a fair researcher, he said. "I agreed to work on the project as long as I was unfettered in what I do and say," Siegel said.
Chesapeake and Smith declined to comment. Siegel said Smith's affiliation with Chesapeake was not revealed in the paper because Smith worked elsewhere for most of the time the analysis was being done.
Smith's work history on LinkedIn changed over the last two weeks, showing conflicting accounts of his employment in the last two years. But a presentation of the methane paper at an October 2014 conference lists Smith as a Chesapeake employee. The paper, when it was received in November 2014 by ES&T, however, lists Smith as an employee of Enviro Clean, an Oklahoma-based environmental remediation company that is a Chesapeake contractor.
"This struck me as problematic. In general, it's unusual for academics to not disclose external funding sources, especially on controversial topics such as fracking," said Gretchen Goldman, lead analyst at the Union of Concerned Scientists' Center for Science and Democracy. "We could argue it would have been good policy for him to mention that."
Siegel, a hydrogeologist with long experience in the Marcellus Shale, said isolated cases of methane contamination from gas development have occurred as fracking spread through the area. But he called fears of widespread water contamination overblown.
Siegel challenged, in particular, studies led by the influential former Duke University earth science professor Robert Jackson. Jackson's teams found a correlation between proximity to gas development and elevated concentrations of methane in residential well water. His research, known as the "Duke studies," has been widely cited and was used by New York officials in the decision to ban fracking, according to reports.
"They were going to places where they know a priori that there was a gas problem," Siegel said of Jackson's team. "You have to sample broadly and randomly to avoid bias."
Jackson, who is now at Stanford University, disputed Siegel's characterization of his studies. "Our goal is to understand the exceptions, the minority of cases where something went wrong; why it happened; and how can we keep it from happening somewhere else," he said. Jackson said he offered to Chesapeake to help analyze its well data, but the company did not respond.
The Siegel study was based on water samples taken between June 2009 and November 2011 from homes within a three-quarter-mile radius of Chesapeake's planned new gas wells. Because the region already had so much gas development, in many cases an operating well was already nearby, the paper said. In 75 percent of the cases, no methane was detected. The rest showed some methane but no relationship to gas well proximity. The Chesapeake samples were gathered a few months before drilling; they didn't track the wells over time to see if changes occurred.
Amy Townsend-Small, a geology professor at the University of Cincinnati, said she welcomes the bigger data set that Chesapeake provided. But she challenged suggestions that the new paper refutes Jackson's studies. She said Jackson's team tried to home in on the origins of the methane they detected in well water. Industry has argued that methane in well water originated in microbial sources rather than Marcellus gas and was present before fracking began.
A 2013 Duke study of 141 water wells in northeastern Pennsylvania found 82 percent contained methane. Contaminated wells within about a half a mile of an active gas well had concentrations of methane six times higher than those farther away.
The scientists looked at the ratio of noble gases such as helium to methane in contaminated water. They also looked at the levels of ethane and propane in methane-tainted water. Particular ratios of helium to methane and certain levels of ethane and propane in contaminated water indicated that some methane was from a deep geological source, such as the Marcellus Shale. The isotopic fingerprint of the methane was also similar to that of Marcellus gas.
The studies suggested the Marcellus methane ended up in well water because of the wells' faulty metal casings that allowed the methane to seep out into aquifers as natural gas was pumped to the surface. The research said the leaks could also be linked to poor concrete construction inside gas wells.
"We've worked hard to develop additional tools that complement the methane sampling," Jackson said in an email. "For example, the [Siegel] paper doesn't acknowledge or discuss ethane or noble gases. Why not?"
Jackson also challenged the study's water collection methods. Chesapeake hired contractors to sample the water at the tap. As a result, some of the water had already undergone treatment on its way from well to faucet. Treatment and running the water adds "noise" to the readings and affects the amount of methane in a sample, Jackson said.
Further, the contractors used the so-called inverted bottle method to collect the samples, which entails placing an upside-down bottle in a bucket of water to collect the escaping gas. Jackson said he does not use the inverted bottle method because it doesn't produce reliable results. The United States Geological Survey and some other major water testing labs do not use the technique to measure methane.
Siegel said the testing protocol followed Pennsylvania regulatory guidelines. He said that testing water at the tap would not lead to substantially lower readings of methane.
Chesapeake's data would yield new papers in the coming months, Siegel said.