NEW YORK (Reuters) - An Exxon Mobil Corp subsidiary is being charged by the Pennsylvania attorney general for spilling more than 50,000 gallons of wastewater at a natural gas well site in 2010.
XTO Energy Inc, which was acquired by Exxon in 2010, is charged for spilling chemical-laced wastewater from a storage tank and into a local waterway, according to a statement from the Attorney General Kathleen Kane on Tuesday.
State environmental inspectors found the water leaking from an open valve on a tank at an XTO water recycling plant in Penn Township, Pennsylvania.
Authorities later found pollutants from the chemically treated water, including chlorides, barium, strontium and total dissolved solids, in a tributary of the Susquehanna River basin.
XTO is charged with five counts of unlawful conduct under the Clean Streams Law and three counts of unlawful conduct under the Solid Waste Management Act.
XTO was already fined $100,000 for the spill by the Environmental Protection Agency and the Justice Department in July, which the company said was fair, but XTO plans to contest the latest criminal charges.
"Criminal charges are unprecedented, baseless and an abuse of prosecutorial discretion," XTO said in a statement on its website. "The incident did not result in significant or lasting environmental harm."
Wastewater is a by-product of hydraulic fracturing, known as fracking, which involves pumping millions of gallons of water, sand and chemicals deep underground to fracture shale rock and release oil and gas. Much of the water returns to the surface after fracking is complete, and is often placed in holding tanks for recycling.
The chemicals used in fracking have spurred a national debate about the dangers of the process which has unlocked huge amounts of oil and gas from U.S. shale rock over the past decade.
U.S. gas production is at record highs and oil output is at its highest levels since the 1980s.
Pennsylvania, which sits atop the Marcellus shale formation, is at the heart of the U.S. fracking boom. Production there has rocketed since 2005, but the state has also experienced a number of drilling accidents and spills.
Reporting By Edward McAllister; Editing by Chris Reese