Stormwater management - Southwest Washington

Detention pond

Well maintained detention ponds. Above: detention ponds are dry between storms. Below: Shortly after a rain storm, the pool of water is slowly draining.

Detention pond



Detention pond

A stormwater detention pond is an open basin built by excavating below ground or constructing above-ground berms or embankments. The detention pond temporarily stores stormwater runoff and slowly releases it through a specially designed outlet or control structure. Detention ponds typically are designed to drain completely within a few hours or days. Styles vary greatly, from well manicured to natural appearing. Generally, more natural-appearing vegetation is preferred for reduced maintenance and enhanced wildlife habitat. Some facilities are designed to appear as natural water bodies or park-like areas.

Signs that maintenance is needed and a checklist for maintaining the facility including how to fix problems.

Additional elements to detention ponds

Field inletField inlet
A field inlet is a concrete structure that collects stormwater and routes it through underground pipes. Fitted with a slanted, slotted grate, it often traps sediment and debris. Regular maintenance is important. Keep the opening clear of obstructions. A field inlet is usually cleaned by a truck with a vacuum hose but sometimes can be cleaned with hand tools.

Flow control structureFlow control structure/flow restrictor
Underground flow control structures and flow restrictors direct or restrict flow in or out of facilities. They slowly release stormwater at a specific rate. It is important to make sure they do not become plugged or damaged because the facility could release water too quickly or too slowly and overflow. They are usually found in manholes.

Debris and access barrierDebris and access barrier
A debris or access barrier is a bar grate over the open end of a pipe larger than 18 inches in diameter that prevents large material, people or animals from entering. They typically are located on the outlet pipe from a detention pond to the control structure.

For safety purposes, only qualified personnel should remove debris from the barrier when water is flowing through the pipe.