MARSHALL — Marshall has been making progress on reducing the amount of water softener salt that ends up in the Redwood River. But there’s still a way to go before the city can meet new standards for chlorides in its wastewater, said Marshall wastewater superintendent Scott Truedson.

“The easy work has been done,” Truedson said. He suggested opening up a city rebate program for more than just optimizing or replacing water softeners. Marshall residents could qualify for the rebate with do-it-yourself installation, or by choosing to go without a water softener altogether, he said.

At Tuesday’s Marshall City Council meeting, council members voted to approve the proposal.

Over the past few years, the city has been working to reduce the amount of chloride released in city wastewater in order to comply with stricter limits from the Minnesota Pollution Control Agency. City staff said water softener salt was a major source of chlorides in Marshall’s wastewater.

Marshall now pre-softens its city water to reduce the need for water softener salt in homes. The city also received a state grant to provide free water softener optimization, and to offer rebates for upgrading old and inefficient water softeners.

“The wastewater staff have put a lot of effort into the chloride reduction,” and did a lot of outreach work with local water customers, said Marshall Public Works Director Jason Anderson.

However, Truedson said the city wasn’t meeting new chloride limits just yet. The limit the city would have to meet was a monthly average of 261 milligrams per liter of chloride, with a daily maximum of 302 milligrams per liter.

Truedson said one challenge in meeting that limit was that dry weather increases the concentration of chlorides in wastewater, Truedson said.

The new chloride limits will become enforceable on April 1. Truedson said Marshall has applied for a 10-year variance to buy time to meet the new limits. The MPCA has agreed to the variance, but it also needs approval from the Environmental Protection Agency, he said.

Truedson said there were additional steps the city could potentially take to try and cut down on salt in Marshall wastewater.

“The city will have to continue to work with local industries to reduce chlorides,” he said.

Additionally, the city could open up the water softener rebate program to do-it-yourself installation to encourage more water softener compliance, or encourage going without a water softener, he said. Another option could be city enforcement, like setting a deadline to optimize or replace old water softeners, and then adding a monthly surcharge until residents and businesses could prove they were in compliance. The city could also ban salt-based water softeners.

“That’s harsh, but I’m just putting those options out there. They need to be talked about,” Truedson said.

Council members voted to approve a proposal to expand the rebate program.

On Tuesday, Truedson also gave an update on the process of getting a new permit for the Marshall wastewater plant. The chloride limits are just one requirement Marshall will have to meet, Truedson said.

“Right now the city has received a draft version” of the new permit, he said. “We just started our 30-day pre-public review period, and during that we can send comments to the MPCA on anything we see that isn’t right.”

The city received notification of its new limits from the MPCA on April 1 of this year. Since then, the city has had meetings with the MPCA, the Minnesota Environmental Science and Economic Review Board, attorneys and consultants with engineering firm Bolton & Menk to talk about the proposed limits, Truedson said.

In addition to chloride, the Marshall wastewater treatment plant will have to meet limits for the levels of phosphorus and sulfates in city wastewater.

“Sulfates in the groundwater in this area are high,” Truedson said.

Industry in Marshall also adds to the sulfate levels in city wastewater.

“Source reduction is the only way we can meet the new limit at the wastewater plant,” he said.

Truedson said the MPCA granted Marshall a 15-year schedule of compliance to meet the new limits.

“Phosphorus, we’ve been treating for that for quite some time, but we have a new, more stringent limit that we’ll have to meet June through September,” Truedson said.

Phosphorus can have a bigger negative impact on the Redwood River at that time, he said.

“Currently, the city can just meet the proposed limit, with no margin for mechanical or biological failure,” he said.

The city was granted a 10-year schedule of compliance for the phosphorus limit, Truedson said.