Retention and Detention Pond Maintenance
Why is Maintenance Important?
Retention ponds, if not properly maintained, can increase pollutant discharge downstream, increase the instability of downstream channels, raise the risk of downstream flooding, and cause additional aesthetic and other nuisance issues.
A poorly maintained retention pond is doomed to fail. If the pond is not owned by the local government, it is the obligation of the association to keep it in functioning order, as well as any costs incurred.
This includes regular inspections to identify and repair areas of erosion, gullies, and other damage, especially after severe storms or heavy rain; removing sediment and debris from the pond before it reaches the outlets; and beautifying the surrounding banks with grass, shrubs, and other vegetation.
When the pond is out of sight and/or there is no plan in place to consistently maintain it, simple maintenance such as mowing, garbage and litter cleanup, modest landscaping, sediment removal, and slope stability are typically overlooked. Bringing a neglected pond up to code can be a significant, unexpected cost as well as a disaster for the environment.
Failures within the pond and property damage downstream might cost hundreds of thousands of dollars. Don’t forget about the attention from local government agencies, as well as the possible fines that come with a failed pond.
Who is Responsible for Maintaining the Retention/ Detention Pond?
Let’s start with who is required to take care of this pond maintenance. It primarily comes down to the location of the pond. Cities are responsible for any retention ponds within the public right of way or land owned by the town. Runoff that occurs on private property is the responsibility of the property owner, property management company, or community Homeowners Association (HOA). So, if a retention pond is in your community, office park, or shopping center, your HOA or property management company needs to take steps to care for it.
Businesses are required by The Clean Water Act to control runoff from construction sites and completed structures. This includes implementing measures to prevent polluted runoff from flowing into the area’s water supply (such as a retention pond).
If you’re unsure if a stormwater pond is your responsibility, it’s best to contact your city utility department.
How Often Should Retention Ponds Receive Maintenance?
There are several retention pond maintenance tasks to stay on top of. Here are the suggestions, from Water Management Inc., for the most important routine measures you should take to prevent more significant problems and keep your pond in good working condition.
- Inspections: Stormwater pond inspections should be performed as part of an overall stormwater management plan. Water Management Inc. can  conduct quarterly or annually inspections and within 24 hours of a major storm event that generates more than one inch of rain. Inspectors should have a detailed checklist of things to look for after rainfall, including obstructions, trash accumulation, erosion, and sedimentation.
- Vegetation management: Monthly mowing helps prevent erosion and maintains pleasing aesthetics around the stormwater pond. Businesses or property owners should minimize fertilizer and pesticide use to avoid downstream pollution.
- Mechanical equipment maintenance: Check valves, pumps, fence gates, locks, and mechanical components during periodic inspections.
- Sediment removal: About every six months, accumulated sediment must be removed from the bottom of the outlet structure. During this process, pond depths should also be checked at several points. Accumulated sediment should be removed if it has decreased the pond’s original design depth by more than 25%.
- Structural repair and replacement: Eventually, the structural components of a stormwater pond will need to be repaired or replaced. Water Management Inc. can help you determine when this is necessary.
