As required by the federal Clean Water Act, the MPCA assesses all waters of the state and creates a list of impaired waters — those that fail to meet water quality standards — every two years. The listings are based on intensive water monitoring of major lakes and streams along with data from partners. This list is used to set pollutant-reduction goals needed to restore impaired waters, called the total maximum daily load.
Defining impaired waters
A body of water is considered “impaired” if it fails to meet one or more water quality standards. Minnesota water quality standards protect lakes, rivers, streams, and wetlands by defining how much of a pollutant can be in water before it is no longer drinkable, swimmable, fishable, or useable in other, designated ways (called “beneficial uses”).
- Mercury levels that lead to limits on fish consumption
- Nutrients that grow algae
- Sediment that clouds water
- Bacteria that can make water unsafe for swimming
- Unhealthy conditions for fish and bugs
- PFOS found in fish tissue
- Sulfate impairments that may hinder the production of wild rice
The MPCA responded to all written comments received through Jan. 7, 2022. EPA took all public comments and MPCA responses into consideration when approving of Minnesota’s Impaired Waters List on April 29, 2022.
- MPCA responses to comments received on Minnesota’s draft 2022 impaired Waters List (wq-iw1-79b)
- Public comments received on Minnesota’s draft 2022 Impaired Waters List (wq-iw1-79a)
Stormwater management and in-lake treatments have made waves in two Twin-Cities area lakes, reducing pollution and improving water clarity.
Improving water quality in Lake George has required treating phosphorus in the water and filtering pollutants out of urban stormwater.
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