Stormwater wetland design criteria Revision as of 14:04, 22 January 2013 by Chochstein (talk | contribs)
Revision as of 14:04, 22 January 2013 by Chochstein (talk | contribs)
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| Design Criteria | Shallow Wetland | Pond/Wetland | ED Shallow Wetland* |
|---|---|---|---|
| Wetland/Watershed Ratio (Ac/Ac) | 0.2 | 0.1 | 0.1 |
| Minimum Drainage Area (Ac) | 25 | 10 | 25 |
| Length to Width Ratio (minimum)(ft/ft) | 2:1 | 2:1 | 2:1 |
| Extended Detention (ED) | No | Optional | Yes |
| Allocation of Vwq (pool/marsh/ED) in % | 25/75/0 | 70/30/0(includes pond volume) | 25/25/50 |
| Allocation of Surface Area (deepwater/low marsh/high marsh/semi-wet) in % | 20/35/40/5 | 45/25/25/5 (includes pond surface area) | |
| Forebay | Required | Required | Required |
| Micropool | Required | Required | Required |
| Outlet Configuration | Reverse-slope pipe or hooded broad-crested weir | Reverse-slope pipe or hooded broad-crested weir | Reverse-slope pipe or hooded broad-crested weir |
*Note: The ED Shallow Wetland design guidance does not meet the MPCA requirements for permanent volume. The guidance may be applied in a stormwater retrofit situation where area requirements preclude the use of a Shallow Wetland