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*Organic filters are a source of soluble phosphorus and should not be used.
 
*Organic filters are a source of soluble phosphorus and should not be used.
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*Biofiltration is acceptable when the appropriate [[Design criteria for bioretention#Materials specifications - filter media|filter media]] is used.
 
*Employ finer-grained media in the filter bed with a small diameter (15 microns), or provide a finer-grained layer at mid-depth in the filter profile.
 
*Employ finer-grained media in the filter bed with a small diameter (15 microns), or provide a finer-grained layer at mid-depth in the filter profile.
 
*The process for pre-treatment and/or filtration should extend from 36 to 48 hours, where possible.
 
*The process for pre-treatment and/or filtration should extend from 36 to 48 hours, where possible.

Revision as of 01:21, 21 February 2014

Summary of stormwater design recommendations to enhance phosphorus removal.
Link to this table

BMP Design Design recommendations
Bioinfiltration Bioinfiltration is a preferred practice.
Filtration (includes bioretention with an underdrain)
  • Organic filters are a source of soluble phosphorus and should not be used.
  • Biofiltration is acceptable when the appropriate filter media is used.
  • Employ finer-grained media in the filter bed with a small diameter (15 microns), or provide a finer-grained layer at mid-depth in the filter profile.
  • The process for pre-treatment and/or filtration should extend from 36 to 48 hours, where possible.
  • Filters should be oriented to provide maximum solar exposure.
  • Wet swales are not recommended.
  • Open channels should be designed to be either self-cleansing or promote maximum sediment retention.
  • Open channels should not be relied on as the only BMP to remove phosphorus at a site, with the exception of an engineered dry swale.
Stormwater Ponds
  • Design wet ponds with a depth no greater than 10 feet to prevent stratification and potential release of phosphorus from bottom sediments.
  • Avoid the use of dry or dry extended detention ponds
  • Designers should consider the snowmelt runoff volume and design ponds for seasonal operation
  • Use a surface or mid-depth release from the pond.
  • Landscape pond to discourage geese.
  • Add shallow benches and wetland areas to enhance the plankton community.
  • Follow mosquito advisories in Chapter 6.
Constructed Stormwater Wetlands
  • Pond/ wetland system is the preferred wetland design.
  • Use a surface or mid-depth release from the wetland.
  • Maximize surface micro-topography.
  • Landscape wetland to discourage geese.
  • Follow mosquito advisories in Chapter 6.
Infiltration
  • Infiltration BMPs are preferred practices.
  • Provide a minimum 3-foot separation from the seasonally-high water table, bedrock or impervious soil layer.