The Minnesota Pollution Control Agency would like you to think about salt, and not just because we saw snow on May 19. As chloride concentrations continue to rise in lakes, rivers, and groundwater around Minnesota, the agency is working with partners to develop a Statewide Chloride Management Plan that will help to keep our freshwater resources, well…fresh.
Chloride (salt) concentrations have been increasing in the Minnesota, St. Croix, and Mississippi Rivers since 1985 and MPCA’s most recent water monitoring data show that 50 water bodies around the state – that’s 221 river miles and 1,400 acres of lakes – have accumulated so much chloride that they are now toxic to fish and aquatic life. While most people are familiar with the harmful impacts of winter road salt, it turns out there are also several other significant ways that chloride makes its way into our environment. Some surprising culprits include water softener salt, agricultural fertilizer, manure, industrial discharges from factories, and dust suppressants applied to dirt and gravel roads. In fact, a 2019 report by the University of Minnesota estimates that 65% of all chloride discharged into lakes and rivers by wastewater treatment plants (136,000 tons of chloride annually) comes from water softeners.
Chloride is a tricky pollutant because it persists in the environment and cannot be filtered out with practices such as raingardens, buffer plantings or stormwater ponds. Once salt is in water, it can only be removed through reverse osmosis. Imagine trying to run an entire lake through a reverse osmosis filter, and you’ll quickly see understand why most experts agree that chloride in our environment is basically there to stay.
High chloride levels can kill fish, invertebrates, and plants, but salty water isn’t just a problem for nature. The MPCA has found that 16% of monitoring wells in the Twin Cities area that are located in shallow sand and gravel aquifers have too much chloride; this is a major reason for concern in a state that gets 75% of its drinking water from groundwater. Chloride in drinking water can also corrode lead and copper pipes, leading to additional health concerns.
Through the Statewide Chloride Management Plan, MPCA hopes to work with municipalities, counties, watershed districts and other state experts to develop strategies for reducing the biggest sources of chloride in our waterways – winter maintenance, dust control, and water softening. The agency is also focusing on critical areas around the state where more salt is being used – highly developed watersheds with lots of roads and parking lots, and areas with very hard drinking water.
Over the next month, MPCA will hold three meetings around the state to share the draft plan and seek input from the public:
- Twin Cities — Thursday, May 30, 8:30 a.m. – noon, Dakota Lodge, 1200 Stassen Lane, West St. Paul, MN 55118
- Duluth —Wednesday, June 12, 8:30 a.m. – noon, Griggs Center, Kirby Student Center, 1120 Kirby Dr., Duluth, MN 55812
- Cloud/Alexandria — Wednesday, June 19, 8:30 a.m. – noon, Douglas County Public Works Department, 526 Willow Dr., Alexandria, MN 56308
Learn more about chloride and its impacts on Minnesota water at www.pca.state.mn.us/water/chloride-101.
Hi Angie, Thanks for your article,…very enlightening. We have seen the same thing here in WI. Have you looked at Cl levels in groundwater at all? This may be also a source of Cl discharges to surface water. We are seeing quite high levels of Cl in groundwater primarily connected with road salt. Take care and best regards, Steve Oberle
Hi Steve – yes, the MPCA has also been testing groundwater around the state. They’ve found that chloride levels are rising in shallow groundwater in the metro area due to road salt, but there are also concerns that water softener salt is gradually contaminating groundwater in rural areas with septic systems as well. It is such a confounding problem!