By Mica Rosenberg
NEW YORK (Reuters) - An Exxon Mobil Corp
In a statement announcing the fine, the U.S. Justice Department and the Environmental Protection Agency also said XTO Energy Inc
Alan Jeffers, a spokesman for XTO, said the company thought the fine was fair and already had begun spending on the improvements required.
"There is no lasting environmental impact," he said.
Fracking, short for hydraulic fracturing, involves injecting water and chemicals deep underground to fracture shale rock and unleash oil and gas. Energy companies are increasingly treating and reusing water in the drilling process.
State environmental inspectors in 2010 found dirty 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, the government agencies said.
The fine was issued for violations of the federal Clean Water Act.
Wastewater from natural gas exploration and production often contains high levels of dissolved solids and other chemicals that can contaminate the environment and drinking water, the government said.
"The operational improvements required by today's settlement will help to protect precious surface and drinking water resources in Pennsylvania and West Virginia," EPA official Cynthia Giles said in a statement.
The Justice Department and the EPA said XTO must install a remote monitoring system for its drilling operations and wastewater storage tanks, with alarms that immediately alert operators if a spill occurs.
The government also said the company cannot use open tanks to store wastewater to try to cut down on air emissions.
(Reporting by Mica Rosenberg; Editing by Howard Goller)