Detention Basin & Water Quality

Detention basins are usually located in new residential, commercial, and industrial developments, helping control potential flooding. Detention basins require regular maintenance in order to ensure proper function. Poorly maintained basins lose their ability to control flooding and pollution, allowing sediments, fertilizers, and pesticides to enter creeks and streams. Homeowners associations and property owners are responsible for maintaining their detention basins.

• Dry detention basins — typically dry depressions that temporarily fill with stormwater after a major rain storm. Dry detention basins are less effective at removing pollutants because the stormwater passes through quickly.
• Wet detention basins — typically have a permanent pool of water and more native wetland plant life. These basins are more effective at removing pollutants.
• Stormwater wetlands — similar to wet detention basins, but contain more wetland native plants. They also provide fish and wildlife habitat.

Water quality best management practices (BMP) help protect water quality by removing pollutants from stormwater.

• Stormwater ponds–have a combination of permanent pool, extended detention or shallow wetland.
• Stormwater wetlands–include significant shallow wetland areas to treat stormwater but often may also incorporate small permanent pools and/or extended detention storage.
• Infiltration practices–capture and temporarily store stormwater before allowing it to infiltrate into the soil over a two day period.
• Filtering practices (bioretention)–capture and temporarily store the stormwater and pass it through a filter bed of sand, organic matter, soil or other media.
• Open channel practices–typically designed to capture and treat stormwater within swales formed by checkdams or other means.

• Get a copy of your detention basin plan — contact your municipality’s public works department in order to determine what type of detention basin is in your neighborhood.
• Inspect inlet and outlet pipes — check to make sure pipes aren’t crumbling or broken; make sure pipes are free of debris and obstructions; check for erosion around the pipes.
• Inspect for litter and debris — check for debris near the inlets and basin twice a year and after major storms. Remove debris and dispose of it with your household trash.
• Examine for erosion— check twice a year and after major storms, filling in damage with topsoil and seeding it with turf grass. If erosion problems continue, contact your municipality for further guidance.
• Inspect vegetation — inspect the banks and in the basin, removing dead vegetation. Dead vegetation should be disposed of with other compost materials. Consult with a professional landscape architect for planting information.
• Mowing — the amount will depend on the type of detention basin and desired appearance, but typically basins will only need to be mowed two or three times a year. Do not fertilize the grass in your detention basin.
• Keep records — good records will help you make adjustments to your maintenance program as needed. Keep records of all inspections, including dates, names of inspectors, maintenance activities performed, what was observed, and costs.
• Annual reporting–is required for BMPs. MSD’s Design Rules and Regulations require submittal of an annual stormwater maintenance report to insure BMPs are kept in working order. The annual report describes the inspections and maintenance activities specified for the basins and BMP in the Stormwater Management Facilities (BMP) Operation and Maintenance Plan. These plans are submitted to MSD, Division of Environmental Compliance, 10 East Grand, St. Louis, MO 63147

For more information on detention basin maintenance and water quality BMP maintenance, please contact us at (314) 768-6260.