America’s largest oil refinery, in Port Arthur, Texas, prepared to shut down Tuesday as Tropical Storm Harvey continued to batter the storm-ravaged region, plant operation sources said.

The Motiva Enterprises refinery produces 603,000 barrels a day out of Port Arthur, which is about 80 miles up the coast from Galveston.

The pending shutdown was first reported by Reuters. A rep for Motiva told The Post on Tuesday night that the refinery was running at 40 percent of normal production.

“Although weather conditions continue to deteriorate, Motiva’s Port Arthur Refinery remains stable at reduced rates approximately equal to 40 percent of capacity,” according to a Motiva spokeswoman. “Our highest priority remains the safety of our employees and community.”

The company announced earlier Tuesday that it was chipping in $500,00 to recovery efforts in Houston and Port Arthur areas.