Given the controversy over oil and gas drilling in Colorado and its impact on the environment, it's worth highlighting a new federal study that looked at one of the biggest bones of contention: the potential for groundwater contamination through hydraulic fracturing.

The study's preliminary verdict is decidely good news.

What The Associated Press is calling a "landmark federal study" by the Department of Energy monitored fracking fluids for a year that were injected deep underground in wells in western Pennsylvania. By tagging the fracking fluid with "unique markers," federal scientists could locate them if they migrated into groundwater.

They didn't.

Indeed, no trace of the fluid was detected in a monitoring zone that was still a mile below drinking water.

The study, by the National Energy Technology Laboratory, is apparently the first time a private company and federal scientists have teamed up in this fashion — which is a bit surprising.

Still, the finding itself is far from shocking. Fracking has been conducted for decades and is now a routine procedure in the vast majority of drilling operations and yet federal and state regulators have not identified one confirmed instance in which fracking chemicals have migrated through layers of shale to groundwater.

The Environmental Protection Agency did tentatively — and controversially — link water contamination to fracking at a site in Wyoming. Yet just last month, the agency abandoned further study there, reinforcing doubt about the value of its early findings.

To be sure, well construction defects and surface spills have occurred in drilling, and sometimes have impacted groundwater. But the idea that widespread fracking is poisoning drinking water supplies is — so far at least — an unsubstantiated charge by opponents, and it should be reassuring to the public that another study has confirmed this.

Whether the news will make a difference is another question. Josh Fox, director of "Gasland" and "Gasland Part II," tells visitors to his website that "water contamination due to fracking" is a "very serious" problem. And he and other activists beat that drum so insistently that it seems to influence the most unlikely audiences.

Last month, for example, a group of 26 Colorado craft brewery officials sent Gov. John Hickenlooper a letter urging stronger regulation of drilling while making specific reference to the need for "good clean water" to brew beer.