Delaware ? Motiva Enterprises LLC has agreed to pay a $12 million civil penalty to settle a lawsuit filed by government regulators following a fatal tank collapse and explosion at a Delaware oil refinery four years ago, authorities said Monday.

Motiva also has agreed to pay more than $4 million for a series of environmental projects, and to reimburse the state and federal governments more than $170,000 in costs associated with their investigations.

As part of the settlement, Premcor Inc., which acquired the refinery from Motiva in 2004, will install new safety controls valued at $7.5 million, bringing the combined total of the settlement to $23.7 million.

Officials planned to release details of the settlement at a news conference in Wilmington today.

The explosion killed boilermaker Jeffrey Davis of Pennsylvania, injured eight other workers, and spilled more than a million gallons of sulfuric acid, some of which flowed into the Delaware River.