It took three years, but the EPA has finally decided that hydraulic fracturing (“fracking”) in Wyoming has in fact been contaminating local ground water.

When residents of Pavilion, Wyoming claimed three years ago that fracking fluid–a mix of water, sand and chemicals–as well as gas had leaked into their water supply, the EPA constructed two monitoring wells in the area. The agency also tested and retested public and private drinking water wells.

The EPA found that the water indeed contained concentrations of fracking chemicals, including glycols, alcohols and benzene, that are beyond established health and safety standards. The initial report, released on Thursday, is still subject to review and will be sent to an independent scientific review board. It is also open for public comment.

In order to extract natural gas from shale rock, a relatively new technology called “fracking” involves injecting high-pressured water mixed with sand and chemicals to crack open the rock and capture it.

“Given the area’s complex geology and the proximity of drinking water wells to ground water contamination, EPA is concerned about the movement of contaminants within the aquifier and the safety of drinking water wells over time,” the EPA wrote in a statement.

Unlike many other fracking locations, the Wyoming gas field, being fracked by Encana, was located close to drinking water wells. In places like the Marcellus Shale, thousands of feet of shale rock separate ground water from the fracking locations.

In 2010, the EPA already registered samples from Wyoming indicating that contamination had occurred. The recently released report confirmed those initial findings. Its remains to be seen how the local findings will impact, if at all, national regulations.

The EPA is currently also conducting a national report on the safety of hydraulic fracturing and will release recommendations for national oversight and regulation of the process.

Photo Caption: View of the partially frozen Yellowstone Lake at the West Thumb Geyser Basin in the Yellowstone National Park, Wyoming on June 2, 2011. Yellowstone National Park, was established by the U.S. Congress and signed into law by President Grant on March 1, 1872. The park is located primarily in the U.S. state of Wyoming, though it also extends into Montana and Idaho and was the first national park in the world. It is known for its wildlife and its many geothermal features, especially the Old Faithful Geyser.