What are Stormwater Ponds?

In residential developments, you will often see small
ponds throughout neighborhoods. These are stormwater ponds and they
collect stormwater runoff, a leadingcause of water pollution. Stormwater
runoff is rainwater or snowmelt that runs off streets, parking lots, rooftops
and compacted lawns.

The ponds are designed to look like natural lakes or wetlands, and as such are often mistaken for landscaping features. But they are there to prevent flooding and collect stormwater and pollutants like heavy metals, sediment, bacteria,
oils and nutrients. The ponds collect and filter the water, keeping pollutants
out of lakes and rivers.

Healthy ponds do their job better. 

Residential tips to keep ponds healthy

• Limit use of lawn fertilizers and pesticides. These have nutrients and chemicals that get washed into the ponds and can cause algae blooms.
• Preserve established trees, shrubs, and vegetation. Plant or allow a buffer strip to grow. Native plants trap and filter polluted runoff.
• Do not dump grass clippings or leaves in the pond or near stormdrains. This will cause algae blooms. Sweep or rake up any leaves from curbs and stormdrains to keep them from washing down.
• Do not pour chemicals, oils, etc. in or near the pond or allow any household or automotive chemicals to drain into the storm drain. Use biodegradable soaps for outdoor cleaning. Bring hazardous wastes to the Environmental Center in Chaska. 
• Sweep up grit and debris on driveways and sidewalks, do not hose it into the street.
• Pick up animal waste and dispose of it in the trash.
• Direct downspouts towards lawns or gardens or use a rain barrel to reduce runoff.

Living by a stormwater pond

• Stay out of the water. Stormwater ponds are not a recreational water body. It is strongly advised against any swimming, wading, and boating due to potential dangers including pollutants, toxic cyanobacteria, steep slopes and unstable bottoms. 
• 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. Skating and other activities are not recommended. 
• Do not add fish to a stormwater pond. It is illegal to add fish to lakes or ponds, including the dumping of pets. Adding fish can harm the ecosystem and the fish may become an invasive species such as the goldfish found in Big Woods Lake. 
• 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.

Each pond has a “buffer” around it. A buffer is an area of plants surrounding the pond, usually about 10 feet wide but sometimes up to 30 feet wide. This buffer strip slows down and filters stormwater running off yards before the water reaches the pond. Removing the native plants in the buffer strip or mowing straight down to the pond gives polluted water direct access to the pond. Protect the buffer and you protect the pond.

Two factors can cause green ponds. The first is related to nutrients, specifically phosphorus, which causes algae blooms. These ponds are designed to capture pollutants, such as phosphorus, so they will rarely be pristine, but homeowners around the ponds can unknowingly increase phosphorus in ponds. See above for tips on how to keep phosphorus out of ponds.

Another green factor is duckweed, which is often mistaken for algae. Duckweed is a tiny, free floating green plant that can form thick blankets across a pond. Duckweed is a native and an important food source for birds and wildlife and it has such good water filtering capabilities it is used by water treatment plants.

Maintenance

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 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.