Ponds with a Purpose

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Symp Hills SE basin

What are Stormwater Ponds?

Stormwater ponds are man-made basins built to capture and treat stormwater runoff in order to protect lakes and rivers from pollution.

Stormwater runoff is a leading cause of water pollution. It occurs when rains or snow melt, flows from rooftops, driveways, lawns, streets, sidewalks, and compacted yards. This water picks up dirt, sand, bacteria, and other pollutants along the way and washes them into lakes and rivers.

Stormwater ponds capture and treat polluted runoff. They allow sediments and other pollutants to settle to the bottom of the pond. Treated water then moves on slowly to lakes and rivers. Additionally, stormwater ponds prevent flooding by slowing down water flowing across the land, controlling the infiltration and retention of excess stormwater.

Residential tips to keep ponds healthy

  • Limit lawn fertilizers and pesticides. These have nutrients and chemicals that get washed into the ponds and can cause algae blooms.
  • Pick up animal waste and remove/dispose of all trash.
  • Preserve established trees, shrubs, and vegetation. Plant or allow a buffer strip to grow. Native plants trap and filter polluted runoff.
  • Sweep driveways and sidewalks clear of grass clippings and leaves instead of hosing them off. The water flows into storm drains and into your nearest pond or water body.
  • Direct downspouts towards lawns or gardens or use a rain barrel to reduce runoff.
  • Do not dump yard waste into a pond. The ponds are not designed to handle the high levels of nutrients found in leaves, grass clippings or brush. Excess nutrients cause algae.
  • Bring hazardous waste like motor oil, paint, and chemicals to the Environmental Center in Chaska to be disposed of properly. 

Living by a stormwater pond

  • Stay out of the water. Swimming, wading, and boating of any type is dangerous and is not allowed on stormwater ponds.
  • Keep pets away from the water. For the health and safety of your pets, do not allow them to swim in or drink the water.
  • Stay off the ice. Ice on stormwater ponds is weaker and unpredictable. This is because of road salt in the stormwater runoff flowing in and the constantly changing water levels. Do not skate or do other activities.
  • Do not add fish to a stormwater pond. It is illegal to add fish to lakes, including the dumping of pets. Adding fish can harm the ecosystem and the fish may become an invasive species.
  • Do not go fishing in a stormwater pond. Because of the poor water quality, fishing in a stormwater pond is a risk to your health.


Stormwater ponds are designed to capture and treat polluted runoff and therefore, can end up with a pollutant build up. As the ponds fill up, they require maintenance and cleaning. Contact your city for more information about pond inspection and maintenance.

Contact the city if you wish to do the following 

  • Remove native vegetation including cattails, shrubs, trees or native grasses.
  • Regrade the ground surface and thus disturb soil that may wash off with rain.
  • Use a pond for irrigation.
  • Plant additional vegetation.