Bioretention treatment is accomplished by pooling water on the surface of the facility and allowing settling and filtering of sediment and suspended solids at the mulch layer, prior to entering the soil media proper.

Vegetated buffer strips provide an extra level of pretreatment when utilized in conjunction with the bioretention facility, and their use is optional. Some agencies require additional surface vegetated area adjacent to the bioretention area to meet their stormwater management design criteria.   For retrofit projects and sites with tight green space constraints, it may not be possible to include a grass buffer strip.  For example, parking lot island retrofits may not have adequate space to provide a grass buffer.

In lieu of grass buffer strips, pretreatment may also be accomplished by other methods such as a Forebay, Pretreatment Swale / Channel, Mulch layer, Sand Filter Layer, Gravel Diaphragm, and Up Flow Inlets for storm drain inflow.  Check with your state or local guidance for specific pretreatment expectations or requirements.

CONTINUE TO Flow Entrance

The above information was derived from the Prince George's County Bioretention Manual.

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The information on this website was compiled by T.E. Scott & Associates, Inc. from various sources.

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Last modified: 10/23/09