Motiva Enterprises, LLC this week pleaded guilty to negligently endangering workers at its former refinery in Delaware City, Del., discharging pollutants into the Delaware River and negligently releasing sulfuric acid into the air, both in violation of the Clean Air Act.

In a plea agreement, Motiva agreed to pay a fine of $10 million and to serve a three-year term of probation.

On July 17, 2001, Tank 393, a 415,000-gallon capacity tank at Motiva's Delaware City Refinery, exploded while containing spent sulfuric acid, which is a mixture of sulfuric acid, water and hydrocarbons. The explosion killed one worker and injured numerous others. Spent sulfuric acid from the tank farm spilled into the Delaware River, resulting in thousands of dead fish and crabs.

Shortly before the explosion, according to the statement of facts, Motiva had several warnings from its own employees about Tank 393's problems. Still, workers were sent to the acid tank farm to repair the catwalk connecting the tanks on July 17, and a hot works permit was issued for the job. During the afternoon of that day, flammable vapors from Tank 393 reached a heat source, and the resulting explosion caused the tank to separate from its foundation pad. About 99,000 gallons of sulfuric acid drained into the Delaware River for days after the explosion.