Best Management Practices that infiltrate stormwater runoff into underlying soil include, but are not limited, to

  • infiltration basins,
  • infiltration trenches,
  • underground infiltration,
  • bioinfiltration,
  • permeable pavements, and
  • tree trenches and tree boxes.

These are discussed briefly below.

Infiltration basin

photo of an infiltration basin
Photo of an infiltration basin. Source: Clark County, Washington, with permission.
Residential yes
Commercial Yes
Unltra-urban Limited1
Industrial Yes2
Highway/road Limited
Recreational Yes
Treatment capabilities3, 4, 5
TSS High6
TN Medium/high
TP Medium/high
Chloride Low
Metals High
Oils and grease High
Pathogens High

1 Due to a size restriction
2 Unless the infiltration practice is located in an industrial area with exposed significant materials or from vehicle fuelling and maintenance areas. Infiltration BMPs are PROHIBITED in these areas.
3Underground infiltration systems will have different pollutant removal capabilities than what is provided in this table. These systems may have a wider application range, however, there is concern that they do not provide adequate treatment of the pollutants.
4 This is only for the portion of flow that enters the infiltration basin; by-passed runoff does not receive treatment.
5 Low = < 30%; Medium = 30-65%; High = 65 -100%)
6 Assumes adequate pre-treatment

An infiltration basin is a natural or constructed impoundment that captures, temporarily stores, and infiltrates a design volume of water.

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