Hilcorp Energy Co. agreed to pay $2.55 million to settle claims that its extraction operations in the Appalachian Basin of Pennsylvania violated state and federal air laws.

The US Department of Justice filed a suit and proposed consent decree against the private oil and gas company Thursday in the US District Court for the Western District of Pennsylvania.

This marks the second Clean Air Act settlement for Hilcorp in the past month. The company agreed Oct. 17 to pay $9.4 million over alleged excessive emissions at its New Mexico operations.

Hilcorp's Pennsylvania operations, which include eight facilities extracting natural gas ...