Stormwater filtration Best Management Practices

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. Filtering BMPs are designed only for pollutant removal, and do not reduce peak flows for flood control or channel protection. These BMPs have not been widely applied in cold climates (CWP, 1997), but some filtering systems have the potential to be valuable BMPs in these regions.

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 Infiltration practices.

• Permeable pavement (+)
• Trees
• Bioretention - biofiltration
  • Rain garden (bioretention)
• Swale
• Sand filter

Other filtration BMPs, including pre-treatment practices

• Green roofs (+)
• Turf
• Vegetated filter strips
• Manufactured devices
  • Filtration devices

• Examples of filtration systems. Click on an image for enlarged view.
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  Schematic of a biofiltration BMP.

• Permeable pavement credits underdrain.jpg

  Schematic of a permeable pavement BMP.

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  Schematic of a sand filter BMP.