Difference between revisions of "Summary of stormwater credits function"
(Created page with "<center><font size=3>'''Table summarizing stormwater credits function. The table illustrates how to calculate water quality volume, channel protection and overbank storm volum...") |
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Link to this Summary of stormwater credits function|table]].</center> | Link to this Summary of stormwater credits function|table]].</center> | ||
| − | <table class="sortable"><tr> | + | <table class="sortable"> |
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<th>Stormwater credit</th> | <th>Stormwater credit</th> | ||
<th>Adjusted water quality volume</th> | <th>Adjusted water quality volume</th> | ||
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<tr> | <tr> | ||
<td>Streams and shoreline buffers</td> | <td>Streams and shoreline buffers</td> | ||
| − | <td>Subtract ADB from site IC when computing V<sub>wq</td> | + | <td>Subtract ADB from site IC when computing V<sub>wq</sub></td> |
<td>Adjust CN for ADB to woods in good condition</td> | <td>Adjust CN for ADB to woods in good condition</td> | ||
</tr> | </tr> | ||
Revision as of 20:25, 14 January 2013
Link to this Summary of stormwater credits function|table]].
| Stormwater credit | Adjusted water quality volume | Channel protection and overbank storms |
|---|---|---|
| Natural area conservation | Subtract CA from site IC when computing Vwq | Adjust CN for CA to woods in good condition |
| Site reforestation/prairie restoration | Subtract 1/2 RA from site IC when computing Vwq | Adjust CN for RA to woods or prairie in fair condition |
| Streams and shoreline buffers | Subtract ADB from site IC when computing Vwq | Adjust CN for ADB to woods in good condition |
| Surface impervious cover and disconnection | Subtract DIA from site IC when computing Vwq | Adjust CN for DIA to grass in good condition. Adjust Tc |
| Rooftop disconnection | Subtract DRA from site IC when computing Vwq | Adjust CN for DIA to grass in good condition. Adjust Tc |
| Grass channels | Subtract GA from site IC when computing Vwq | Adjust Tc |
Note: Unless otherwise noted, all units below are measured in acres
- CA = combined area of all natural areas conserved at site
- RA – Total area of site reforestation or prairie restoration
- ADB – Total area draining to buffer with appropriate flow path distance
- DIA – Total area of surface impervious cover that can be effectively disconnected
- DRA – Aggregate rooftop area that can be effectively disconnected
- GA - total non-roadway area draining to swale (rooftop, yard and driveway)
- CN – Runoff curve number for area (units: dimensionless) (see Ch.8 and App. B)
- Tc – Time of Concentration (units: time)
Vwq – Water quality volume, as defined by relevant MPCA sizing rule - IC - Impervious area of site (acres)