There have been three instances in Butler County where gas drilling officially has impacted or contaminated water supplies, according the state Department of Environmental Protection.

Since 2008, 209 private water supplies in the state were confirmed to have been impacted by oil and gas activities. During that same time, drilling was done on more than 20,070 wells, including 12,068 conventional wells and 8,002 unconventional wells.

DEP plans on posting this month or next month a list of all confirmed cases of impacted or contaminated water, and it will update the list over time as new cases are confirmed.

“This frequently requested information is being shared with the public in our continued effort to be as open and transparent as possible,” said DEP spokesman Morgan Wagner in an e-mail.

In Butler County, two of the incidents took place in Winfield Township and one occurred in Forward Township.

The three incidents were:

• A water supply at a residence along Three Degree Road in Winfield Township was affected in 2012 by methane as a result of a compromised well casing in an old well drilled by BLX of Kittanning. The well was about 200 feet from the water supply.

BLX plugged the well and installed a permanent vent on the water supply, and the methane dissipated. The DEP received the complaint on March 25, 2012, and it was resolved on March 28, 2012.

The DEP on June 4, 2013,determined that the issue was caused by gas activity. BLX could not be reached for comment.

• A spring at a residence on Marwood Road in Winfield Township in 2012 was affected when Snyder Brothers of Kittanning was drilling for natural gas using the fracking method. Holes in a pit liner allowed fluids in that pit to mix in with the spring. The company repaired the holes, and the spring eventually returned to predrill conditions.

The DEP received the complaint July 25, 2012, and it was resolved the following day. The DEP on Sept. 7, 2012, determined the incident was caused by gas activity. Snyder Brothers could not be reached for comment.

• A water supply at a residence on Marburger Road in Forward Township in 2013 reported elevated levels of iron and manganese while XTO Energy, which has its Appalachian Division headquarters in Marshall Township, was drilling a well. XTO installed a treatment system on the water supply, and it returned to predrill conditions.

The DEP got the complaint April 16, 2013, and it was resolved April 24, 2013. The DEP on Aug. 28, 2013, determined that the incident was caused by gas activity.

Mike Johnson, vice president of operations for XTO's Appalachian Division, said in an e-mail response, “We work closely with community residents and other stakeholders to mitigate concerns on water quality and other impacts, including in April 2013 in Forward Township. Although it was not clear that our operations had an impact, XTO acted in a proactive manner and resolved the issue for the landowner.”

The counties with the most confirmed incidents are Bradford with 48, Susquehanna with 35 and McKean with 24.