BIG RAPIDS -- Nearly all the 18,000 gallons of black water-based paint that escaped from Haworth Inc. via a city sewer Saturday was diverted into big holding tanks at the Big Rapids sewer treatment plant, officials say.

The accidental release of paint was discovered Saturday night at the steel components plant, 300 N. Bronson Ave.

"The paint has been contained in the Big Rapids sewage treatment plant, and 'very, very little' got out of the plant. In fact, our staff says none got in the river," said Mary Detloff, spokesperson for the state Department of Natural Resources and Environment.

Haworth's plant prepares steel parts for a variety of filing cabinets and storage units, and was closed overnight Saturday. It gradually began to resume operations Sunday, as city, state, and company officials launched investigations.

"We think we retained a fairly significant part of that (paint) within the (sewer) plant," said Don Greiner, director of public works for Big Rapids. "We had basins that were empty, so we diverted it into those until we filled them up.

"We went for a 13-hour period, without anything into the river at all."

The 600,000 gallons of storage capacity could handle the flow of paint-tainted sewage, Greiner said. But city and company officials are scrambling to figure out how to dispose of the polluted water.

After a two-hour meeting Wednesday, Haworth environmental engineer Steve Kooy said a decision is near on the right way to handle the tainted water in the city's sewer tanks.

"It's waiting there for us to take care of this," Kooy said. "We'll either send it to a treatment facility or treat it onsite. We want to ensure all the paint solids are taken out, and the rest of water sent through the treatment plant."

Haworth discovered the problem Saturday evening, when an employee checked the plant's paint tank and saw it was lower than it should be. When workers looked inside the paint department's onsite containment tank, they found it empty. Next, they realized the black paint was making its way down the city sewer that empties into the Muskegon River.

Fortunately, Kooy said, the gravity-fed sewer line had a slow flow rate during the weekend spill. When city officials were alerted, they diverted the paint-laden sewage into empty holding tanks at the city facility.

On Wednesday, Haworth was preparing its report on the paint spill for Big Rapids officials, who will submit their own report to the state DNR.

One suspected cause is a drain valve that was stuck open when it should have been closed. Kooy said some plumbing failure is likely to be the origin of the problem. The paint spill at the Big Rapids plant will drive inspections and safety checks at plants around the globe, he said.

In the short term, another concern is rain, Greiner said. With overflow tanks already filled with paint-laced sewage, a heavy rainfall could stress the sewer plant's capacity to fully treat incoming effluent.

"We typically run at about half the plant's rated capacity. If we got a rainfall, depending on its intensity and duration, we would not be able to fully treat the water because we don't have other basins to fall back on," Greiner said.

Worst case? Some sewage would flow out without being fully treated. But none of the paint-polluted storage tanks would be in play, he said.

E-mail Julia Bauer: jbauer@grpress.com and follow her on Twitter at twitter.com/jbauer5800