For over 50 years, Minnesota's de-icing salt has made roads, sidewalks, parking lots and other paved surfaces less slippery. Unfortunately, de-icing salt does not break down in the environment, does not flush away easily, and is nearly impossible to remove. Most de-icing salt stays in waterways near its application. This has resulted in more than 4,000 waterways listed as impaired for aquatic life due to high concentrations of chloride according to the MPCA.
As de-icing practices increase with new development, Twin Cities' waterways are increasingly at risk for chloride impairment. High levels of chloride harm native vegetation and wildlife, and can impair ecological services such as lake turn over in Spring and Autumn. More on lake turn over here.