A study of drinking water in Appalachian Ohio found no evidence of natural gas contamination from recent oil and gas drilling. The time-series study was the first of its kind in Ohio to examine methane in groundwater in relation to natural gas drilling. The results were published in the journal Environmental Monitoring and Assessment.
Geologists with the University of Cincinnati examined drinking water in Carroll, Stark and Harrison counties, a rural region in northeast Ohio where many residents rely on water from private underground wells.
Some people had elevated concentrations of methane in their groundwater, but the isotopic composition showed it wasn’t from natural gas.—Amy Townsend-Small, associate professor of geology in UC’s McMicken College of Arts and Sciences
UC researchers collected 180 groundwater samples in total at homes in the three counties. Some of the sites were sampled multiple times. In particular, researchers looked for evidence of methane, the primary compound in natural gas. They also studied changes in the acidity or pH of the water, and changes to its conductivity.
They found no increase in methane concentration or composition in groundwater over the four years of the study, despite the presence of new shale gas wells drilled in the study area. Likewise, they did not find higher methane levels in closer approximation to shale drilling.
Researchers did find wide variability in methane concentrations in the drinking water, ranging from 0.2 micrograms per liter to 25.3 milligrams per liter, which is strong enough to catch fire in enclosed spaces. But researchers found no relationship between the methane observed in drinking water and the new gas wells.
Researchers identified the chemical composition of the water using gas chromatography, isotope ratio mass spectrometry, and radiocarbon dating in a UC geology lab. Understanding the chemical composition helps identify the source of methane found in drinking water: from natural gas extraction, organic decomposition or even from the digestive systems of nearby cows.
The study area has seen increasing interest from natural gas companies in recent years. It’s located above a geological feature called the Utica Shale formation, which is known to harbor oil and natural gas. When UC launched its methane study in 2012, Ohio had issued 115 drilling permits for the region. By the study’s end in 2015, nearly 1,600 permits had been issued, primarily for Carroll County.
Researchers hypothesized that methane concentrations in the drinking-water wells they sampled would increase over time with the growth of natural gas drilling in the area. This is a correlation researchers observed in Pennsylvania’s Marcellus Shale region. However, that’s not what UC’s water tests revealed. The study concluded that methane observed in groundwater was “biogenic,” or naturally occurring and independent of natural gas drilling.
The study researchers in Pennsylvania thought the contamination issue was a failure of the well casings in the fracking wells. Hopefully, that doesn’t happen often. And that apparently didn’t happen with the wells of homeowners we worked with for our study.—Amy Townsend-Small
The study was funded in part with grants from the David F. & Sara K. Weston Fund and the Deer Creek Foundation. Instruments were provided with grants from the National Science Foundation.
E. Claire Botner, Amy Townsend-Small, David B. Nash, Xiaomei Xu, Arndt Schimmelmann, Joshua H. Miller (2018) “Monitoring concentration and isotopic composition of methane in groundwater in the Utica Shale hydraulic fracturing region of Ohio” Environmental Monitoring and Assessment 190:322 doi: 10.1007/s10661-018-6696-1