Slide 47 of 52
Notes:
The primary pretreatment technique for bioretention facilities is a grass filter strip or grass channel. For applications where runoff enters the bioretention system through sheet flow, such as from parking lots, or residential back yards, a grass filter strip with a pea gravel diaphragm is the preferred pretreatment method. The length of the filter strip depends on the drainage area, imperviousness, and the filter strip slope.
This slide gives some filter strip sizing guidelines as a function of inflow approach length, land use, and slope. The minimum filter strip length should be 10 feet.
