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.
- 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.
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| 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.
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| 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.
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| Infiltration |
- Infiltration BMPs are preferred practices.
- Provide a minimum 3-foot separation from the seasonally-high water table, bedrock or impervious soil layer.
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