University of Cincinnati researchers recently conducted a peer-reviewed study that concluded hydraulic fracturing or “fracking” is not contaminating groundwater in the Utica Shale region of Ohio, according to The Heartland Institute.

After collecting 180 samples from more than two-dozen wells in Belmont, Carroll, Columbiana, Harrison and Stark counties from 2012 to 2015, the researchers found “no relationship between [methane] concentration or source in groundwater and proximity to active gas well sites.” In fact, the evidence showed a modest decline in well-water methane levels over the course of the study.

These findings were reinforced by the U.S. Environmental Protection Agency’s $29 million, six-year study of fracking’s effect on groundwater sources, which failed to find any systemic impact from the 110,000 oil and natural gas wells in operation using fracking across the country since 2011.

Learn more: The Heartland Institute > Fracking is not contaminating groundwater in Ohio, study finds