Summary of stormwater design recommendations to enhance phosphorus removal.
Link to this table
| BMP Design |
Design recommendations |
| Infiltration |
- Infiltration BMPs are preferred practices
- Provide a minimum 3-foot separation from the seasonally-high water table, bedrock or impervious soil layer
|
| Filtration (includes practices with an underdrain) |
- Organic filters are a source of soluble phosphorus and should not be used
- Practices with engineered media are 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 pretreatment 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 because they may export phosphorus
- Open channels should be designed to promote maximum sediment retention
|
| Stormwater Ponds1 |
- Pond aeration is encouraged
- 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
- Pond sediments may be amended to retain phosphorus (e.g. iron, aluminum)
|
| 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
|
1The recommendations for constructed ponds are from the original Minnesota Stormwater Manual. MPCA anticipates updating this information in the near future.
