MPCA: Winter road salt causing chloride problems for Twin Cities waters


High levels of chloride are threatening aquatic life in some Twin Cities waters, the Minnesota Pollution Control Agency says.

The agency has a lengthy report out to try to address the problem – and wants the public to know it can weigh in.

According to the draft of the Chloride Management Plan, released in July, water quality samples taken from lakes, wetlands, streams and groundwater show increased chloride levels in urban areas across the state.

In the Twin Cities metropolitan area, data shows 39 water bodies have chloride levels that are higher than what's considered protective of the aquatic community. (The report though clarifies that monitoring has been done for only about 10 percent of all the surface water bodies in the Twin Cities area.)

The primary reason for this is road salt, according to the agency (more on that below), which says on its water quality page that 1 teaspoon of the stuff can permanently pollute 5 gallons of water.

So the challenge, the MPCA says in a news release, is balancing public safety with everyone's expectations for clear, dry roads throughout the winter.

Why does this concern the MPCA?

Too much chloride is bad for water life, basically.

The agency says high concentrations of the compound can cause problems for natural cellular processes. In turn, that can lead fish, invertebrates and plants to become stressed or die.

Getting chloride out of water is a problem, too.

The only known technological way to do it is through reverse osmosis. It has to go through "massive" filtration plants, the MPCA says, which is expensive and not realistic financially. That means, without any removal, the levels will keep building up over time.

Where's the chloride coming from?

The MPCA identifies to key sources.

One is road salt. Treatment for the thousands of miles of pavement throughout the Twin Cities relies on sodium chloride, which breaks up ice and prevents it from forming.

But when all the snow and ice melts, the chloride stays with it, essentially going wherever the water goes.

The MPCA says this is "typically the primary source" of chloride in the state's surface waters and groundwater.

There's also residential water softeners, a "significant" source of chloride, the MPCA says. This gets into the environment through sewage systems or by delivery to a municipal waste water treatment plant. But during regular treatment methods, chloride isn't extracted from the waste water – meaning it continues on.

Public comments welcome

The report is now open for public review and comment through Sept. 2, the MPCA says.

The goal of the MPCA's report is to come up with a process for measuring pollution level in water bodies, identifying why it's happening, then proposing ways to help fix the issue.

Comments can be submitted in writing to Brooke Asleson (520 Lafayette Road N., St. Paul, MN 55155-4194), or emailed that way at brooke.asleson@state.mn.us. Asleson can answer questions by phone at 651-757-2205.

In the comment, you have to include a statement about your interest in the report, then explain actions you want the MPCA to take (in detail, with specific reasons why, referring to specific sections).

Comments have to be in by 4:30 p.m. on deadline day.

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