BMPs for stormwater infiltration

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. Source: Clark County, Washington, with permission.

Applications
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.