Ray Kimble shows the discoloration in a gallon of water he says came from his well in Dimock, Pennsylvania, March, 2012. (Photo by Jim Lo Scalzo/EPA)

A federal jury awarded on Thursday $4.2 million to two Pennsylvania families after determining a nearby natural gas well contaminated their well water.

The problems in the town of Dimock were featured in Gasland, a critical HBO documentary on hydraulic fracturing. Thursday's verdict found the well operator, Texas-based Cabot Oil and Gas, negligently allowed the contamination to occur.

"This is a huge victory for Dimock families who have fighting for clean water for over six years," said Alex Lotoro, of the Energy Justice Network, an environmental group that backed the families.

"Finally, justice has been served for Scott and Monica Ely, their three children, and their neighbors, the Huberts," Lotoro said in a written statement.

Dimock is located atop northeastern Pennsylvania's Marcellus Shale, the epicenter of the fracking boom that has revolutionized the US petroleum industry. Residents began complaining about their water soon after Cabot began drilling wells in their small town in 2008, and a water well contaminated with methane exploded in 2009.

Cabot said it would appeal Thursday's verdict in a US District Court in Scranton, citing "the lack of evidence provided by plaintiffs in support of their nuisance claim."

"The verdict disregards overwhelming scientific and factual evidence that Cabot acted as a prudent operator in conducting its operations," the company said.

In 2009, state regulators cited Cabot for polluting wells used by 19 homes in Dimock. The company settled with regulators, agreeing to replace the water supplies for those homes and plug and abandon a number of nearby wells.