After weeks of apprehension, the Environmental Protection Agency will step in to supply drinking water to residents of Dimock, PA, a de facto acknowledgment that fracking led to contamination of the water supply in this town along the Delaware River Basin.

On Friday, the agency announced it would bring tanks of drinking water to four homes, including that of Julie Sautner, whom ProPublica first interviewed about her water problems in 2009.

“Data reviewed by EPA indicates that residents’ well water contains levels of contaminants that pose a health concern,” the agency said in a statement. Tests showed dangerous levels of arsenic, a carcinogen, as well as glycols and barium in at least four wells, and the EPA is apparently concerned that the contamination may be more widespread.

According to the statement, the EPA plans to test the water supplies in 60 additional homes for hazardous substances.

Cabot Oil & Gas, which had drilled the wells in Dimock, had been providing drinking water to the residents for some time. But they abruptly cut off service in December, and residents had no stable source of water for weeks. It appeared that the EPA would step in earlier in the month, but they changed their mind for a time while they sought further study and testing. Apparently those tests have satisfied the EPA that Dimock’s water supply is indeed damaged enough to require this intervention.

Through this action, the EPA basically admits that fracking, the process of boring into rock with mass quantities of fluid to release trapped natural gas, does endanger water supplies. They had already proved this through scientific study in Wyoming. It’s hard, then, to just continue a hands-off approach to fracking, allowing state environmental agencies to handle the regulation. Indeed, the Pennsylvania Department of Environmental Protection allowed Cabot to stop supplying Dimock residents with water. Environmental groups jumped on the announcement:

Environmental groups are applauding the EPA’s move. “This finding confirms what Dimock residents have said for months, that the Pennsylvania Department of Environmental Protection should have never allowed Cabot to end deliveries of clean water,” said Environmental Working Group senior counsel Dusty Horwitt.

But they also say the time has come for the EPA to address water contamination concerns in other communities across the country where residents say drilling has harmed their water.

Once the EPA goes down this road, it’s going to be hard for them to stop. And that’s good news for the residents impacted by fracking. Everyone with video of their water being lit on fire, send them to Washington.