Researchers monitored the site for a year, using drilling fluids tagged with markers that were injected more than 8,000 feet below the surface, but were not detected in a monitoring zone 3,000 feet higher, Begos reports. "That means the potentially dangerous substances stayed about a mile away from drinking water supplies."
During the study "eight new Marcellus Shale horizontal wells were monitored seismically and one was injected with four different man-made tracers at different stages of the fracking process, which involves setting off small explosions to break the rock apart," Begos reports. "The scientists also monitored a separate series of older gas wells that are about 3,000 feet above the Marcellus to see if the fracking fluid reached up to them." Most gas wells are more than a mile underground, while drinking water aquifers are usually 500 to 1,000 feet below the surface. (Read more)