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| colspan="4" style="text-align: center;" | <font size=1><sup>1</sup> 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; <sup>2</sup> This is only for the portion of flow that enters the infiltration basin; by-passed runoff does not receive treatment; <sup>3</sup> Low = < 30%; Medium = 30-65%; High = 65 -100%); <sup>4</sup> Assumes adequate pre-treatment; <sup>5</sup> This assumes no raised underdrain; <sup>6</sup> Certain [http://stormwater.pca.state.mn.us/index.php/Design_criteria_for_bioretention#Materials_specifications_-_filter_media soil mixes] can leach P; <sup>7</sup> Due to a size restriction<br>
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| colspan="4" style="text-align: center;" | <font size=1><sup>1</sup> 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; <sup>2</sup> This is only for the portion of flow that enters the infiltration basin; by-passed runoff does not receive treatment; <sup>3</sup> Low = < 30%; Medium = 30-65%; High = 65 -100%); <sup>4</sup> Assumes adequate pre-treatment; <sup>5</sup> This assumes no underdrain; <sup>6</sup> Certain [http://stormwater.pca.state.mn.us/index.php/Design_criteria_for_bioretention#Materials_specifications_-_filter_media soil mixes] can leach P; <sup>7</sup> Due to a size restriction<br>
 
Sources: EPA Factsheet, 1999; Davis et al., 2001, 2003, 2006; Hsieh and Davis, 2005; Hong et al., 2006; Hunt et al., 2006; NPRPD, 2007; Li and Davis, 2009; Diblasi et al., 2009; Passeport et al., 2009; Brown et at., 2011a, b; Komlos et al., 2012; Denich et al., 2013; Li and Davis, 2013; California Stormwater BMP
 
Sources: EPA Factsheet, 1999; Davis et al., 2001, 2003, 2006; Hsieh and Davis, 2005; Hong et al., 2006; Hunt et al., 2006; NPRPD, 2007; Li and Davis, 2009; Diblasi et al., 2009; Passeport et al., 2009; Brown et at., 2011a, b; Komlos et al., 2012; Denich et al., 2013; Li and Davis, 2013; California Stormwater BMP
 
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Revision as of 20:57, 22 September 2015

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.
Applications and treatment capabilities for infiltration basins
Applications Treatment capabilities3, 4, 5
Residential Yes TSS High6
Commercial Yes TN Medium/high
Ultra-urban Limited1 TP Medium/high
Industrial Yes2 Chloride Low
Highway/road Limited Metals High
Recreational Yes 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 fueling and maintenance areas. Infiltration BMPs are PROHIBITED in these areas; 3Underground infiltration systems may have different (likely lower) pollutant removal capabilities than what is provided in this table. These systems may have a wider application range. 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

Sources: Schueler, 1987, 1992; USEPA 1993a, 1993b; Maniquiz et al., 2010; NPRPD, 2007; California Stormwater Manual, 2009; Pennsylvania Stormwater Manual, 2006

An infiltration basin is a natural or constructed impoundment that captures, temporarily stores, and infiltrates a design volume of water. For more information, see the following pages in this Manual.

Infiltration trench

Photo of a Infiltration trench in Lino Lakes
Photo of a Infiltration trench in Lino Lakes
Applications and treatment capabilities for infiltration trenches
Applications Treatment capabilities3, 4
Residential Yes TSS5 High5
Commercial Yes TN Medium/high
Ultra-urban Limited1 TP Medium/high
Industrial Yes2 Chloride Low
Highway/road Yes Metals High
Recreational Yes 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; 3 This is only for the portion of flow that enters the infiltration basin; by-passed runoff does not receive treatment; 4 Low = < 30%; Medium = 30-65%; High = 65 -100%); 5 Assumes adequate pre-treatment

Sources: Schueler, 1987, 1992; USEPA 1993a, 1993b; Maniquiz et al., 2010; NPRPD, 2007; California Stormwater Manual, 2009; Pennsylvania Stormwater Manual, 2006

An infiltration trench is a shallow excavated trench that is backfilled with a coarse stone aggregate. This design allows for the temporary storage of runoff in the void space of the material in addition to the storage above the aggregate within the trench. For more information, see the following pages in this Manual.

Bioinfiltration basin

photo of a bioinfiltration BMP
Bioinfiltration basin (Source: CDM Smith)
Applications and treatment capabilities for bioinfiltration basins
Applications Treatment capabilities2, 3
Residential Yes TSS High4
Commercial Yes TN Low/Medium5
Ultra-urban Limited7 TP Medium/high6
Industrial Yes1 Chloride Low
Highway/road Yes Metals High
Recreational Yes Oils and grease High
Pathogens High
1 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; 2 This is only for the portion of flow that enters the infiltration basin; by-passed runoff does not receive treatment; 3 Low = < 30%; Medium = 30-65%; High = 65 -100%); 4 Assumes adequate pre-treatment; 5 This assumes no underdrain; 6 Certain soil mixes can leach P; 7 Due to a size restriction

Sources: EPA Factsheet, 1999; Davis et al., 2001, 2003, 2006; Hsieh and Davis, 2005; Hong et al., 2006; Hunt et al., 2006; NPRPD, 2007; Li and Davis, 2009; Diblasi et al., 2009; Passeport et al., 2009; Brown et at., 2011a, b; Komlos et al., 2012; Denich et al., 2013; Li and Davis, 2013; California Stormwater BMP

Bioinfiltration basins, often called rain gardens, use soil (typically engineered media or mixed soil) and native vegetation to capture runoff and remove pollutants. Both the media and underlying soil typically have high infiltration rates that allow captured water to infiltrate within a required drawdown time, usually 48 hours. For more information, see the following pages in this Manual.

Permeable pavement

photo of permeable pavement
Permeable pavement (Source: CDM Smith)
Applications and treatment capabilities for permeable pavement
Applications Treatment capabilities2, 3
Residential Yes TSS High4
Commercial Yes TN Medium/High
Ultra-urban Yes Nitrate Low/Medium
Industrial Yes1 TP Medium/High
Retrofit Yes Chloride Low
Highway/road Yes Metals High
Recreational Yes Oils and grease High
Pathogens 5
1 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; 2 This is only for the portion of flow that enters the infiltration basin; by-passed runoff does not receive treatment; 3 Low = < 30%; Medium = 30-65%; High = 65 -100%); 4 Assumes adequate pre-treatment; 5 Insufficient information

Source: Schueler, 1987; Pratt et al, 1999; Adams, 2003; Brattebo and Booth, 2003; Adams, 2003; Bean et al, 2007; SEMCOG, 2008; International Stormwater Database, 2012

Permeable pavements allow stormwater runoff to pass through surface voids into an underlying stone reservoir/ subbase for temporary storage and/or infiltration. They are suitable for driveways, trails, parking lots, and roadways with lighter traffic. For more information, see the following pages in this Manual.

Tree box/Tree trench

photo of tree box
Tree box (Source: CDM Smith)
Applications and treatment capabilities for tree box/tree trench
Applications Treatment capabilities2, 3
Residential Yes TSS High4
Commercial Yes TN Low/Medium
Ultra-urban Yes TP Medium/High5
Industrial Yes1 Chloride Low
Highway/road No Metals High
Recreational Yes Oils and grease High
Pathogens High
1 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; 2 This is only for the portion of flow that enters the infiltration basin; by-passed runoff does not receive treatment; 3 Low = < 30%; Medium = 30-65%; High = 65 -100%); 4 Assumes adequate pre-treatment; 5 Certain soil mixes can leach P.

Source: see [1]

Tree trenches and tree boxes (collectively called tree BMPs), consist of trees planted within underground storage reservoirs designed to retain a volume of runoff for the purpose of uptake by trees. They are a variant of bioretention BMPs. For more information, see the following pages in this Manual.

Trees - general
Tree boxes/tree trenches

Underground infiltration and dry wells

Underground infiltration systems and dry wells have been installed below parking lots and other impervious surfaces on sites where insufficient space exists for a surface infiltration system. They are designed to temporarily store stormwater runoff before slowly infiltrating the water into the subsurface (Connecticut, 2004). There is limited information on the effectiveness of these systems in removing pollutants. Limited data suggests they may be less effective at removing mobile pollutants than surface-based infiltration systems.

One concern is that underground infiltration may meet the U.S. Environmental Protection Agency (EPA) definition of a Class V injection well. Class V injection wells are defined as any bored, drilled, or driven shaft, or any dug hole that is deeper than its widest surface dimension. Class V injection wells can also be an improved sinkhole, or a subsurface fluid distribution system (from U.S. EPA, June 2003). The U.S. EPA administers Class V injection well permits in Minnesota. Minimum requirements for installing, permitting, and operating a Class V well is defined by the USEPA.

A second concern pertains to the overall pollutant removal effectiveness of those underground infiltration systems that do not meet the definition of a Class V injection well. The document released by the Transport Research Synthesis titled “Issues of Concern Related to Underground Infiltration Systems for Stormwater Management and Treatment” provides a good overview of the concerns related to underground infiltration systems (MNDOT, 2009). Issues identified in this report include:

  • There is potential that an underground infiltration system meets the criteria of a Class V injection well.
  • There is insufficient knowledge of the fate of pollutants in the subgrade below the buried infiltration systems.
  • Roadways and parking lots with high volumes of traffic have higher concentrations of certain pollutants, including heavy metals and PAHs. Pretreatment devices, such as sumps, may be necessary to protect the subgrade and groundwater.
  • Underground systems do not allow for the pollutant removal that is accomplished through biological activity and vegetation uptake.
  • The minimum separation requirement of 3 feet between the bottom of the infiltration system and the seasonally high groundwater elevation may be insufficient for adequate pollutant removal. Additional study is recommended.
  • Maintenance of underground systems is critical for effective pollutant removal. However, access for maintenance is challenging. There are concerns that the difficult access is preventing owners from properly maintaining these systems.

This Manual currently does not provide guidance for design, construction, maintenance, and assessment of underground infiltration systems.

Unit processes for different infiltration BMPs

The following table provides a summary of unit processes for the different infiltration BMPs.

Unit processes of stormwater treatment techniques (Adapted from WEF, 2008)
Link to this table

Control Infiltration basin Infiltration trench Bioinfiltration Permeable pavement Tree box/tree trench Enhanced turf
Peak flow attenuation X X X X
Runoff volume reduction X X X X X
Infiltration X X X X X X
Dispersion
Evapotranspiration X X
Runoff collection and usage X1 X1
Sedimentation X X X
Flotation X X
Laminar separation
Swirl concentration
Sorption X X X X
Precipitation X X X X
Coagulation X X X X
Filtration X
Plant metabolism X X X
Nitrification/denitrification X X X
Organic compound degradation X X X X
Pathogen die off X X X
Temperature reduction X X X X
Disinfection X X X X

1 If underdrain is present


Related pages