Why Is There a Pond in My Backyard - Maintenance Requirements for Detention & Retention Basins
If there’s a pond in your neighborhood where rainwater eventually flows, its value goes far beyond aesthetics. Retention basins, detention ponds, and other stormwater facilities prevent flooding and downstream erosion, and they improve the quality of your community’s streams, rivers, and bays. n natural areas, only 10% of the rain that hits the ground runs off into streams, most of it is absorbed directly into the ground. When subdivisions are built, natural surfaces are replaced with hard surfaces like roofs, patios, driveways, and roads that prevent water from infiltrating into the ground dramatically increasing the amount of stormwater runoff. That’s A LOT more water moving MUCH faster causing downstream flooding, erosion of stream banks, and overwhelming wetlands.
Considered by the EPA to be the number one threat to America’s waters, stormwater conveys all the residues of our urban living as it courses through its drainage area, or watershed, to local streams and rivers receiving that water. To help mitigate the effects of stormwater runoff, many communities require developers to install stormwater infrastructure that reduces the flow of water from the subdivision to pre-development rates.
Wade Burcham, "So when you move into a subdivision, you, of course, want to be a good neighbor to your downstream neighbors, and you want your upstream neighbors to be a good neighbor to you. So that’s what detention/retention basins basically do. They can help hold that excessive amounts of water that is formed from the increasing of the impervious area. It holds that water and allows that water to slowly dissipate over time reducing the erosion on either your downstream neighbors or on you from your upstream neighbors."
Along with reducing the volume of stormwater runoff, these ponds also minimize downstream impacts and capture trash, sediment, organic debris, chemicals, and other pollutants.
The most common types of stormwater facilities include:
1. Dry ponds (detention basins), which hold stormwater for a short amount of time before slowly emptying out completely, and
2. Wet ponds (retention basins), which maintain a permanent pool of water throughout the year with levels that fluctuate to accommodate additional stormwater.
As a developer completes the construction of a subdivision, they’ll transfer the responsibility of pond maintenance to the property owners association. Along with as-built drawings and an inspection report, the developer should provide an Operations and Maintenance Plan which will include instructions on how to inspect and maintain all stormwater facilities in the subdivision. It’s important to recognize that once this transfer takes place, the property owners of the entire subdivision are responsible for the pond’s ongoing maintenance.
J.J. McCool, "The thing about retention ponds that’s so important, that with a detention pond, if you let it go unmaintained for a number of years trying to get it back to a state that’s functioning can be very expensive. So the old adage about an ounce of prevention is worth a pound of cure, is very apt when talking about retention ponds."
By regularly inspecting and maintaining your subdivision’s pond, you’re not only being a good neighbor, your improving water quality for everyone’s benefit. While some municipalities require routine inspections, it’s important that all stormwater infrastructure is inspected every 6 to 12 months and following every major rain event. Be sure to perform your first inspection before the developer transfers the responsibility of your pond to the POA. Look for any sediment that has built up in the pond itself and the “in falls” and “out falls” Construction activity without properly functioning erosion control, like silt fences, result in excess sediment washing into your stormwater pond which can block outfalls and reduce storage capacity.
The developer is responsible for the removal of any sediment found in the pond before turning control over to the association. In dry ponds, look for standing water which can be a breeding ground for mosquitoes and indicate ongoing erosion within the pond. Look for overgrown grass and brush which can block the outfall and decrease storage capacity. Check for any bare or unstable surfaces which become extremely vulnerable to additional erosion and cause sedimentation. Look out for any large trees within a pond which can reduce storage capacity, and make sure no trees are growing on the berm. Their roots can deteriorate the integrity of that berm increasing the likelihood of a blowout.