Road Salt & Our Lakes and Waterways

City skyline over Lake Monona.

Our local lakes, waterways, groundwater and soil have been absorbing virtually all of the salt spread in the city for more than six decades. Chloride from salt is toxic to small aquatic life and degrades the natural eco-system of our lakes. Once salt is in our waterways, it does not break down – it’s here to stay.

Lake Wingra

According to Public Health Madison Dane County (PHMDC), average chloride concentrations in Lake Wingra have been increasing by about 2 milligrams per liter (mg/L) per year since 1962. In 2016, the average chloride level in Lake Wingra was more than 100 mg/L, about ten times what it was in the early 1960s.

Lakes Mendota, Monona, Kegonsa and Waubesa

Our larger lakes are not immune from the impact of salt. Chloride levels in Lakes Mendota, Monona, Kegonsa and Waubesa have been increasing by about 1 mg/L per year since 1962. In 2016, Monona, Kegonsa and Waubesa all had chloride levels averaging more than 60-70 mg/L. Chloride levels in Lake Mendota averaged around 50 mg/L.

Smaller water bodies

Chloride levels exceeding the Chronic Toxicity Criteria for small aquatic life have been observed in Dunn’s Marsh, University Bay Creek, and Starkweather Creek. According to PHMDC, “Local creeks and marshes are strongly affected by seasonal spikes in chloride. Some shallow groundwater has become a chloride sink, slowly releasing elevated chloride to surface waters.”

Read the full PHMDC Annual Road Salt Report here.

Taking action

Environmental groups like the Friends of Lake Wingra, Friends of the Yahara River and Friends of Starkweather Creek have joined the WI Salt Wise partnership, an initiative focused on raising awareness about responsible salt use.

Want to help make a difference? Start by using only what you need. The image below shows what the right amount of salt looks like:

Correct Salt Distribution

And remember, salt becomes ineffective when temps drop below 15 degrees.

More Information

If you hire a landscaping company to handle your winter maintenance, let them know about the City’s new Winter Salt Certification Program and encourage them to get certified.

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