Difference between revisions of "Requirements, recommendations and information for using bioretention BMPs in the MIDS calculator"
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Revision as of 20:25, 16 May 2013
Below is a summary of requirements, recommendations and other information for using the Minimal Impacts Design Standards (MIDS) calculator for bioretention BMPs.
Warning: The following are requirements of the Minnesota Construction Stormwater General Permit
- 3 foot separation from the bottom of the bioretention system to seasonal high water table
- Use most restrictive infiltration rate within 3 feet of the bottom of the BMP
- Drawdown time of 24 hours for trout streams
- For measured infiltration rates, apply a safety factor of 2 (2.5 for permeable pavement)
- Pretreatment
Caution: The following are recommendations for inputs into the MIDS calculator
- 5 acre or less for contributing area
- Maximum ponding depth of 18 inches, reduced to 6 inches if there is no site information (4 feet for infiltration basin)
- Field tested infiltration rates over table values
Information: The following information may be useful in determining inputs for the MIDS calculator
- Guidance on determining infiltration rates
- Information on site constraints (shallow soil, karst, etc.)
- Information on assessing BMPs
- Information on design metrics (high flow bypass, ponding depths, drawn down)
- Guidance on pretreatment
- Information on soil mixes
- Plant information, including species list that show water tolerance, potential effects of different species on infiltration rates, planting guidance
- Construction specifications
- Information on operation and maintenance of bioretention BMPs.