HENV-713: BMP Maintenance and Operation: Retention Basin

Benjamin Currens, Andrea Drayer, Rick Durham, Brad Lee | Oct. 12, 2023 (New)

Retention basins, or wet ponds, retain a deep, permanent pool of water that can collect stormwater and release it slowly to maintain a desired water level, after which the excess stormwater is released slowly via an outlet (drawdown orifice). Retention basins should always have a baseline level of water present and may be vegetated. Retention basins provide a higher level of pollutant retention (up to 80 percent) and a lower chance of sediment resuspension than detention basins (dry ponds).

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HENV-714: BMP Maintenance and Operation: Grass Swale

Benjamin Currens, Andrea Drayer, Rick Durham, Brad Lee | Oct. 12, 2023 (New)

Grass swales, or dry swales, are designed to transport stormwater, promote infiltration, and capture sediment during a storm event. Grass swales are turfgrass-planted channels constructed with wide bottoms to encourage infiltration of stormwater into the underlying soil. Vegetation in the channel functions to reduce the speed of stormwater and trap sediment as water is conveyed through the channel. When functioning properly, these swales hold water no longer than six hours after a storm and should remain dry until the next storm event.

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HENV-712: BMP Maintenance and Operation: Filter Strip

Benjamin Currens, Andrea Drayer, Rick Durham, Brad Lee | Oct. 12, 2023 (New)

Filter strips are planted and maintained strips of vegetation designed to provide pretreatment of stormwater runoff before it flows into adjacent best management practices (BMPs). Gently sloped, the dense vegetation within the strip reduces the speed of stormwater. This allows for the capture of sediment as stormwater from impervious surfaces passes through the filter strip.

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HENV-715: BMP Maintenance and Operation: Detention Basin

Benjamin Currens, Andrea Drayer, Rick Durham, Brad Lee | Oct. 12, 2023 (New)

Detention basins, or dry ponds, are designed to collect water during a storm event and hold it for a certain amount of time, usually 48 hours. This short impoundment of stormwater allows pollutants carried in the stormwater to settle to the bottom of the basin before collected stormwater is released through a slow-release outlet. When functioning properly, these basins should remain dry after the release of water until the next storm event.