A U.S. subsidiary of Calgary-based Talisman Energy Inc. has been fined by Pennsylvania regulators for a large diesel fuel spill that occurred last year at a Marcellus Shale natural gas well pad.

The Pennsylvania Department of Environmental Protection (DEP) said it fined Talisman Energy USA Inc. of Horseheads, NY, $24,608 for the spill, which occurred last March at the company’s Putnam 77 well pad in Armenia Township, Bradford County.

“This spill went off the well pad and into a neighboring farm field,” said DEP North-central Regional Director Nels Taber. “Talisman is extremely fortunate that it did not impact surface water or wetlands.”

The company reported the spill to DEP, but it has been unable to explain the cause, officials said. Under DEP’s regulations, discharging a polluting substance like diesel fuel without a permit violates the Clean Streams Law and failing to manage the waste properly violates the Solid Waste Management Act.

The cleanup required 3,800 tons of contaminated soil to be excavated and 132,000 gallons of contaminated water was collected, from which about 450 gallons of diesel fuel was recovered, according to DEP.

Talisman management said Thursday it “deeply regrets” the spill and said it had taken steps to improve safety and environmental safeguards at its operations in the Marcellus Shale.