Filtration best management practices (bmps) treat urban stormwater runoff as it flows through a filtering medium, such as sand or an organic material. They are generally used on small drainage areas (5 acres or less) and are primarily designed for pollutant removal. They are effective at removing total suspended solids (TSS), particulate phosphorus, metals, and most organics. They are less effective for soluble pollutants such as dissolved phosphorus, chloride, and nitrate. Their effectiveness for bacteria varies with bmp. Link here for information on pollutant removal. Most filtration BMPs will achieve some volume reduction, depending on the BMP design. See information on credits for each BMP.
To see an overview of filtration BMPS, see BMPs for stormwater filtration.
The following practices typically employ an underdrain, which captures most of the runoff that enters the BMP. For information on these BMPs with no underdrain, see Stormwater infiltration Best Management Practices.