A Marcellus shale gas well operation in Scott Township, Pennsylvania. Photo credit: wcn247/Flickr Creative Commons
At least one aspect of fracking’s risks to drinking water became a little clearer this week.
led by Rob Jackson of Duke University’s Nicholas School of the Environment, and published in the Proceedings of the National Academy of Sciences, found that drinking water wells located within 1 kilometer of a shale gas well in a region of northeastern Pennsylvania are at high risk of contamination with methane.
, shorthand for hydraulic fracturing, is the process of blasting water mixed with sand and chemicals deep underground at high pressure so as to fracture shale rock and release the gas it holds.
Colorless, odorless, and highly flammable, methane
is the primary component of natural gas. It is not regulated as a drinking water contaminant, but it poses potential health and safety hazards. If the gas builds up in a basement or other confined space, for example, it can set off an explosion or start a fire. If breathed in high enough concentrations, it can cause dizziness, headaches and nausea.
The risks of long-term exposure and of secondary water quality changes due to high levels of dissolved methane are not known.
The research team analyzed 141 drinking water wells in northeastern Pennsylvania’s gas-rich Marcellus shale region and detected methane in 82 percent of them. For homes within 1 kilometer of a gas well, the average methane concentration was six times higher than in water wells located further away.
Nearly 1 in 11 of the household wells analyzed had methane concentrations above the threshold level set by the U.S. Department of Interior for immediate remediation; all but one of those drinking water wells was within 1 kilometer of an active shale gas well.
By analyzing the isotopic signature of the gases, Jackson’s team determined that the methane found in the drinking water was of fossil origin, not from current biological activity. The presence of ethane and propane, constituents of natural gas that are not produced by microbes, also signaled that the contamination was coming from nearby fracking operations.
Ethane was detected in 30 percent of the home water wells sampled, and concentrations of this gas were 23 times higher on average for homes less than one kilometer from a fracking well.
“Overall, our data suggest that some homeowners living <1 km from gas wells have drinking water contaminated with stray gases,” Jackson’s team concluded.
Stray gases are those that leak out of the production wells and enter the surrounding environment, including groundwater. The leaks can occur, for example, from faulty steel casings, which are supposed to keep the gas inside the well. Or they can occur from imperfections in the cement sealing between the well casing and the surrounding rock that permit fluids to migrate up the outside of the gas well.
While compelling, the study is not definitive because of the lack of data on the quality of the drinking water wells before the fracking began.
To better gauge fracking’s risks to drinking water, the natural gas industry should be required to disclose its well records or pay for the state or a third party to collect water quality data before fracking operations are allowed to begin.
Without those data, we are flying blind about where, how and under what conditions fracking poses threats to drinking water.
As the Jackson team concludes: “Ultimately, we need to understand why, in some cases, shale gas extraction contaminates groundwater and how to keep it from happening elsewhere.”
The migration of methane into groundwater is only one possible risk to water quality from fracking.
Another is the potential for the fracking fluids – the toxic mixture of sand, water and chemicals used to break open the gas-holding shale formations – to move through natural or secondary fractures into groundwater. And yet another is the contamination threat posed by the discharge of toxic wastewater produced by fracking operations.
In all these cases, more scientific research is needed. Much of it requires that industry not only collect and make available pre-fracking water quality data, but also release the names of the chemicals they are using, instead of hiding them behind the veil of company secrets.
Ultimately, more transparent and safer fracking operations will benefit the industry as well as the families living in fracking territory. Until the public has full confidence that its drinking water is being safeguarded from contamination, it will continue to protest fracking’s expansion.
If hydraulic fracturing is as safe as its proponents claim, then the industry should welcome the scientific studies needed to prove it so.
Until such studies are completed, the public is wise to call for precautionary measures – including moratoriums on fracking.