On May 15, the U.S. Geological Survey and Duke University released their study Geochemical and Isotopic Variations in Shallow Groundwater in the Fayetteville Shale Development, North-Central Arkansas. The report, which analyzed 127 shallow wells in the Fayetteville Shale formation, found minimal levels of methane present. The carbon in the methane was studied, and it was discovered that the methane resulted from biological activity not hydraulic fracturing. The report concluded that fracking did not significantly impact groundwater quality in the area.