Lisa Molofsky, an environmental geologist at GSI Environmental, a consulting group that works with industry to manage and assess environmental risk, echoes Baldassare’s concerns. "How were these water wells selected?" she asks. "Are these from people who are already concerned? If so, there is a high potential for selection bias."
John Connor, president of GSI, also cautions against extrapolating to a wider problem. "They're making very broad statements about things that could be very local," he says, referring to other studies that do not show evidence for methane contamination on a wider scale. "If you happen to pick the one place where a meteor hit the planet, you'll think meteors hit all the time. Maybe they're just standing on the edge of a smoking crater."
Connor and Molofsky wrote a report in 2011 for the Oil & Gas Journal that challenges Jackson’s findings. They find methane to be not only common in groundwater in northeastern Pennsylvania, but also more concentrated in valleys as opposed to higher elevations. They argue that geology, not compromised well casings, is to blame for methane contamination. Houston-based Cabot Oil & Gas Corp., owner of numerous wells in the Marcellus shale region, supported the research. "It's very important to talk about this candidly," Baldassare says. "There have been incidents related to gas well drilling, I'll be the first to admit that.” In 2009, for example, the town of Dimock, Pa, garnered attention when one water well exploded after an electric spark ignited methane in the water. Thirteen wells in the area showed dangerously high levels of a wide range of contaminants, including methane. "But from 2009 to 2013 the way the industry operates is like day and night. They're working hard to improve well integrity."
Both Connor and Molofsky stress the importance of understanding the local geology and getting better baseline data. Whereas the ethane and propane data do seem to rule out a biological source, there are many ways natural gas can seep into the water supply. "It’s hard to say which hat a rabbit came from when all hats contain rabbits," Connor says. "We don't want to bash these guys,” Connor adds. “No one has this really figured out. Papers like this are important in moving the ball forward. They're posing questions, important questions. It's helpful to the overall process."
To move forward, researchers need water samples taken before wells are drilled. Pre-drilling data will establish a baseline for naturally occurring gases and help determine whether or not drilling is introducing methane into the water supply. Some of the homes in the Duke study were selected because they are in areas slated for wells in the next few years. "My motivation is to figure out why sometimes things go wrong and how to fix it," Jackson says. "We're not interested in shutting an industry down, we're interested in solving problems. We just want to make this better."