Basically, the study's authors say that fracking companies are acting without regard to the aquifers of drinking water, but they can't prove the companies contaminated the drinking water -- because no one really knew they were doing it! Via the L.A. Times:

Energy companies are fracking for oil and gas at far shallower depths than widely believed, sometimes through underground sources of drinking water, according to research released Tuesday by Stanford University scientists.

Though researchers cautioned their study of hydraulic fracturing, or fracking, employed at two Wyoming geological formations showed no direct evidence of water-supply contamination, their work is certain to roil the public health debate over the risks of the controversial oil and gas production process.

Fracking involves high-pressure injection of millions of gallons of water mixed with sand and chemicals to crack geological formations and tap previously unreachable oil and gas reserves. Fracking fluids contain a host of chemicals, including known carcinogens and neurotoxins.

Fears about possible water contamination and air pollution have fed resistance in communities around the country, threatening to slow the oil and gas boom made possible by fracking.

Fracking into underground drinking water sources is not prohibited by the 2005 Energy Policy Act, which exempted the practice from key provisions of the Safe Drinking Water Act. But the industry has long held that it does not hydraulically fracture into underground sources of drinking water because oil and gas deposits sit far deeper than aquifers.

The study, however, found that energy companies used acid stimulation, a production method, and hydraulic fracturing in the Wind River and Fort Union geological formations that make up the Pavillion gas field and that contain both natural gas and sources of drinking water.

“Thousands of gallons of diesel fuel and millions of gallons of fluids containing numerous inorganic and organic additives were injected directly into these two formations during hundreds of stimulation events,” concluded Dominic DiGiulio and Robert Jackson of Stanford’s School of Earth Sciences in a presentation Tuesday at the American Chemical Society conference in San Francisco.