The release occurred when an electric pump in the facilitys waste oil/water separation system failed on Sunday morning, EPA Region 5 said in a statement. About 10 percent (6,000 to 6,500 gallons) flowed down a 150-foot embankment and into the river. The rest of the oil collected in a gravel parking area and on the embankment.

EPA Region 5, with support from Illinois EPA and the U.S. Coast Guard Ninth District Marine Safety Unit, responded to the waste oil release incident early Sunday afternoon. The government agencies, Caterpillar workers and contractors worked through the night to contain the spill, EPA said.

The cleanup effort had made good progress, Illinois EPAs Carson said yesterday. They said the shoreline cleanup was nearly completed, and that they have removed most of the impacted gravel and soil between the release point and the river, she told Lube Report. Theyre working on a sampling plan. The plant is back in full production, and all parts that malfunctioned have been replaced.

The Coast Guard said it is monitoring the clean up of the oil that spilled into the river, adding that 1,200 feet of containment boom was deployed on the river near the Caterpillar facility to contain the oil. The Coast Guard temporarily closed the Des Plaines River to vessel traffic and enforced a safety zone. The river is open again, with no restrictions, Illinois EPAs Carson noted yesterday.

A Coast Guard helicopter survey on Sunday showed no observable fish kills or ecological impacts. The EPA said it and natural resource agencies began conducting comprehensive shoreline and embankment assessments Monday.

Caterpillar bills itself as the world’s largest maker of construction and mining equipment, diesel and natural gas engines, and industrial gas turbines.