Protect Our Lakes

What is an MS4 and how to protect our Lakes

If you ask an average citizen what an MS4 is they likely would not know what it was, but MS4 plays into daily life for each and every one of us whether you know it or not. MS4 stands for Municipal Separate Storm Sewer System. Examples of this can be well known from roads, curbs, and stormwater drainage systems, to less known but equally as important such as drainage ditches, conveyances and other man-made channels where stormwater moves throughout our cities. The stormwater that moves through these systems can be polluted, if untreated, and discharged directly to bodies of water such as lakes and rivers that we use every day. These bodies of water are used for recreation and sometimes as a source of drinking water for people. Therefore, it is important to understand how daily activities can impact these water sources.

Total maximum daily load (TMDL) is the amount of pollutants that a water body can absorb daily before water quality standards are impaired. Minnesota currently has 6,168 bodies of water that are impaired with some type of restriction whether it be sediment, nutrients, heavy metals, or bacteria. So, how can your average citizen lower the pollutant load carried by these MS4 conveyances?


Start with your lawn, fertilizer can have a large impact on algae blooms and the oxygenation of our lakes and rivers. Apply fertilizers at the correct rate of application per acre listed on the bag. Fertilizers in Minnesota are required to have less than .7% Phosphorus in the fertilizer mix. All fertilizer bags have a three-number reading that contains nitrogen, phosphorus, and potassium in that order. Every second number on your fertilizer bag should have zero as the middle number, representing 0 phosphorus (ex 20-0-13). When applying fertilizer, ensure that any excess fertilizer on the pavement is cleaned up immediately to prevent washouts to stormwater discharge basins. Leaves and grass clippings can also contain these nutrients, so it is pivotal to sweep after lawn mowing. It is also important to clean up animal droppings to prevent nutrient loading of local waterways from excess pet waste.

Leaks and Spills

Leaks and spills are sources of pollution that can be picked up and carried away with each rainfall event. Vehicle maintenance can be a large source of leaks and spills. When working on vehicles, try to work inside an area that is covered. Check to ensure that once work is done nothing has spilled or leaked. Spilled chemicals need to be cleaned up with absorbents and swept up immediately. Any leaked materials such as fuel, oil, solvents, or grease can carry unwanted chemicals to waterways that will damage water quality. Labels on containers that say caution, warning, danger, or poison need to be disposed of at a hazardous waste facility. Each county will have hazardous waste drop-off sites where chemicals or spilled materials can be disposed of properly.


Salting practices on your property are also a great way to minimize water quality impacts at home. Salt contains chloride which is a labeled impairment on fifty lakes and streams in Minnesota. Safe salting practices are a great way to mitigate the amount of salt that ends up in stormwater conveyances. One cup of salt will safely melt about 250 square feet of paved area and can be applied at that rate. Excess salt that has accumulated once the ice is gone is no longer functional. Extra salt materials can be swept up and disposed of to prevent water quality damage and stop vegetation from dying off and the degradation of cement on your property.

These are all simple preventative actions that can be implemented by everyone to protect our lakes and streams. Preventing pollutants from reaching these MS4 conveyances can uphold water quality for fishing and recreation in the land of 10,000 lakes.