Indiana environmental regulators got word in late July about the latest round of pollution problems at BP’s refinery in Whiting. The company itself had sent a heads-up that it was having a problem with its wastewater system, and at least one neighbor called in a complaint about the smell.

An inspector came out from the state’s Department of Environmental Management, and saw clumpy solids in the wastewater coming out of the plant. However, those solids didn’t exceed what the plant’s permits allow—nearly three tons per day. 

The next week, BP notified state officials that it had busted the permit’s three-ton limit on Monday, August 1. The next day, the waste coming out of the plant spiked—topping 13 tons. 

Why did the number continue to go up, even after BP had been aware of the problem for several days? 

“That’s a good question,” says Hala Kuss, director of IDEM’s northwest regional office. “And that’s something that we are working to understand ourselves.”

Other questions remain as well. Paperwork from BP refers to the problem as “excess biological growth,” but Kuss says she doesn’t yet know the underlying cause. 

The Whiting plant has a history of problems with pollution. 

Earlier this summer, the U.S. Environmental Protection Agency announced a proposed settlement with BP over a 2014 oil spill, a set of 2011 wastewater problems, and clean-air issues. Under the agreement, BP would pay more than $275,000 in civil penalties and commit to better air and water protections.

In 2012, BP settled a Clean Air Act complaint brought by the Natural Resources Defense Council, agreeing to install $400 million in pollution-control equipment. 

By August 3, BP reported that the water it was putting in Lake Michigan included only 4,323 pounds of solid waste—two tons, but below the three-ton limit. Kuss says one of her inspectors saw big vacuums on trucks, sucking waste out of the water before it left the plant.

Still, the water leaving the plant wasn’t clear and colorless, which Kuss says is the norm. What color was it?

“Brownish,” Kuss said. “Not like an opaque, dark brown. But, brownish.” 

Dan Weissmann is a reporter for WBEZ. Follow him @danweissmann.