Recent statewide media have reported growing resident dissatisfaction with neighborhood ponds. Most of the water bodies are man made and were never intended for any purpose other than treating stormwater runoff. Stormwater ponds serve an important function but, depending on their construction, may not live up to the expectation of shimmering blue waters.
Stormwater and snowmelt were once absorbed by undisturbed trees, vegetation, wetlands and other natural features. However, as communities grew and formerly undisturbed natural space gave way to rooftops, roads and parking lots - what stormwater professionals refer to as hard cover or impervious surfaces - stormwater became unable to soak into the ground. Today, the water pools in yards and streets, becoming a nuisance and creating property damage and posing a threat to safety.
Ponds have become a popular method of managing stormwater runoff. A properly designed pond can hold excess water for up to three weeks, allowing pollutants to settle to the bottom. As water was "cleaned" by this process, it was slowly released from the pond.
The process also reduced the rate that water reached downstream locations, greatly reducing incidences of flooding. In some respects, stormwater ponds have re-created the functions of drained or filled wetlands. However, given the purpose of the ponds, their small size and the amount of pollutants handled, there is no guarantee that they will function like the lakes residents hope for.
Maintaining Your Pond
Stormwater ponds will always be just that - ponds that clean runoff. However, they need not be a nuisance. Residents can help reduce algae and odors and promote an attractive appearance by taking simple action. Some suggestions include:
- Buffer strips of plants, shrubs and trees 25 to 50 feet in width around ponds will absorb nutrients, catch sediment, provide habitat and add to the natural effect of ponds.
- Do not dump household or automotive chemicals in yards or storm drains. Included is chlorinated swimming pool water.
- Do not over-water. Depending on the soil, lawns need only one to two inches of water per week, includes rainfall.
- Include native plants in landscape. Such plants are acclimated to the natural conditions and produce deep root systems that promote infiltration of runoff.
- Keep grass clippings and leaves out of ponds. As grass and leaves decompose, they produce phosphorus, the nutrient that promotes algae, which decreases oxygen in water and causes scum and odor. Mulch grass clippings and leaves or bag and dispose of yard waste. Do not blow yard waste materials into the street or down the catch basin. Every storm pipe leads to a body of water that will be negatively impacted by such materials.
- Mow grass taller, promoting root growth. Plant roots open pore spaces in the soil, allowing more water to soak into the ground.
- Pick up trash and pet waste before it enters ponds or storm sewers. Keep trash out of the street and use proper disposal containers.
- Plant a rain garden to slow runoff from roofs, driveways and yards. This improves lawn health and reduces the amount of runoff needing management to maintain clean lakes. Cities and watershed districts have plans and plant lists available.
- Turn downspouts onto lawns instead of driveways and sidewalks.
- Use phosphorous-free fertilizers and apply only the necessary amount of fertilizer. Have soils tested to determine how much and what type of fertilizer to use. What the lawn does not absorb will be washed into storm sewers and ponds.
The City is required to obtain a permit from the State of Minnesota Pollution Control Agency that mandates stormwater management. An annual schedule of inspection for all stormwater-related structures has been developed by the Engineering and Public Works departments. Inspections ensure these features are working properly and necessary repairs are made promptly. Streets are swept at least twice per year to prevent sediment build up in ponds and storm sewer pipes.