MARSHALL — Helping to keep pollution out of the Redwood River has been a big task for the city of Marshall over the past several years. The work’s not done yet, as Marshall City Council members heard earlier this week.

On Tuesday, the council voted to accept a quote from engineering firm Bolton & Menk to assist with both an ongoing study of the city’s wastewater, and compliance with new limits on pollutants released into the river.

“There’s six new things they want us to have on our next permit, so we basically need engineering services to look this over and see what we have to do,” said Marshall wastewater superintendent Scott Truedson.

The total cost of the services from Bolton & Menk are not to exceed $40,000, city staff said.

Truedson said there were two parts to the services Bolton & Menk would be helping the city with. The first was testing and study of the Whole Effluent Toxicity (WET) of the wastewater Marshall discharges into the river.

“It’s a test that we have to take,” Truedson said of the WET. “We actually failed that back in 2011, so the Minnesota Pollution Control Agency had us enter into a toxicity reduction evaluation.”

It’s currently thought that chloride or possibly nitrogen levels in the wastewater were the reason the city failed the test, Truedson said. With MMU’s new water pre-softening plant operational, the city might be able to narrow down what the problem is, he said.

The second process Marshall was looking for engineering help on had to do with new pollutant limits the MPCA has set for the city, Truedson said. Marshall’s National Pollutant Discharge Elimination System (NPDES) permit expired in 2019, but the city has continued to comply with those standards while waiting for the new ones. In April, the MPCA gave the city an outline of what the new permit will require.

The MPCA would be setting new limits for the amounts of chlorides, copper, phosphorous, sulfate and other pollutants that could be discharged from the Marshall wastewater plant.

Mayor Bob Byrnes said he thought Bolton & Menk would be helpful in figuring out what Marshall needs to do to meet the new limits.

Byrnes said he had spoken with the MPCA environmental specialist working on Marshall’s permit.

“I think it’s probably one of the more complex permits that this person has handled,” he said. “I think from the MPCA’s side, they’d also appreciate the engineering assistance and working collaboratively with the city.”