Difference between revisions of "Overview of unified stormwater sizing criteria"
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'''Regular Waters:''' None required, although recharge and infiltration are strongly encouraged through better site design and stormwater credits. | '''Regular Waters:''' None required, although recharge and infiltration are strongly encouraged through better site design and stormwater credits. | ||
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'''CGP Special Waters:''' Full infiltration of the excess runoff volume from the two year-24 hour storm event is one option contained in the CGP to meet the requirement for temperature control for trout streams. | '''CGP Special Waters:''' Full infiltration of the excess runoff volume from the two year-24 hour storm event is one option contained in the CGP to meet the requirement for temperature control for trout streams. | ||
| − | '''Other Sensitive Receiving Waters:'' Recharge recommended as a local option. | + | |
| + | '''Other Sensitive Receiving Waters:''' Recharge recommended as a local option. | ||
Recharge may be restricted or prohibited in certain settings, as outlined in the Recharge and Infiltration Criterion below.</td> | Recharge may be restricted or prohibited in certain settings, as outlined in the Recharge and Infiltration Criterion below.</td> | ||
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'''Regular Waters:''' Apply MPCA Sizing Rule 1 or 3 in 2003 GCP, depending on BMP used. | '''Regular Waters:''' Apply MPCA Sizing Rule 1 or 3 in 2003 GCP, depending on BMP used. | ||
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'''CGP Special Waters:''' Apply MPCA Sizing Rule 2 or 4 in 2003 GCP, depending on BMP used. Additional BMPs required under CGP Appendix A (B) for special waters. | '''CGP Special Waters:''' Apply MPCA Sizing Rule 2 or 4 in 2003 GCP, depending on BMP used. Additional BMPs required under CGP Appendix A (B) for special waters. | ||
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'''Other Sensitive Receiving Waters:''' Recommend expanded sizing criteria for most-sensitive lakes, trout streams (in CGP), susceptible wetlands and impaired waters, as described later in this section.</td> | '''Other Sensitive Receiving Waters:''' Recommend expanded sizing criteria for most-sensitive lakes, trout streams (in CGP), susceptible wetlands and impaired waters, as described later in this section.</td> | ||
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'''Regular Waters:''' No current state requirement. It is recommended that communities adopt a criterion for either 24-hour extended detention of the 1-year, 24-hour design storm or one-half of the 2-yr, 24-hr pre-development peak flow when revising or adopting local stormwater ordinances for peak flow control (and eliminate two-year peak discharge requirements). | '''Regular Waters:''' No current state requirement. It is recommended that communities adopt a criterion for either 24-hour extended detention of the 1-year, 24-hour design storm or one-half of the 2-yr, 24-hr pre-development peak flow when revising or adopting local stormwater ordinances for peak flow control (and eliminate two-year peak discharge requirements). | ||
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'''CGP Special Waters:''' One- and two-year design storm peak discharge and volume control required in four special water categories (wilderness, trout lakes, lake trout lakes, and scientific and natural areas). | '''CGP Special Waters:''' One- and two-year design storm peak discharge and volume control required in four special water categories (wilderness, trout lakes, lake trout lakes, and scientific and natural areas). | ||
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'''Other Sensitive Receiving Waters:''' 12-hour detention of water is recommended as the most for discharge to trout streams (to prevent heating), while other sensitive receiving waters should maintain the 24-hour minimum.</td> | '''Other Sensitive Receiving Waters:''' 12-hour detention of water is recommended as the most for discharge to trout streams (to prevent heating), while other sensitive receiving waters should maintain the 24-hour minimum.</td> | ||
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'''Current Local Requirement:''' Varies, but typically involves either 10-year design storm peak discharge control, or a combination of 10- and 25-year design storm peak discharge control. | '''Current Local Requirement:''' Varies, but typically involves either 10-year design storm peak discharge control, or a combination of 10- and 25-year design storm peak discharge control. | ||
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'''CGP Special Waters and Other Sensitive Receiving Waters:''' No additional requirements.</td> | '''CGP Special Waters and Other Sensitive Receiving Waters:''' No additional requirements.</td> | ||
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<td>Extreme Storm <sub>(Vp100)</sub></td> | <td>Extreme Storm <sub>(Vp100)</sub></td> | ||
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| − | '''Current Local Requirement:''' Varies, but frequently involves 100-year design storm peak discharge control. In other cases, peak discharge control is waived | + | '''Current Local Requirement:''' Varies, but frequently involves 100-year design storm peak discharge control. In other cases, peak discharge control is waived if development is excluded from ultimate 100-year floodplain, or an acceptable downstream hydrologic analysis indicates it is not needed. Stormwater BMPs must be designed to provide safe overflow of the 100 year-peak discharge even if extreme storm control is not required at the site. |
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'''CGP Special Waters and Other Sensitive Receiving Waters:''' No additional requirements.</td> | '''CGP Special Waters and Other Sensitive Receiving Waters:''' No additional requirements.</td> | ||
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Revision as of 15:39, 25 March 2013
Link to this Overview of unified stormwater sizing criteria
| Target | Current State or Local Sizing Criteria |
|---|---|
| Recharge (Vre) or Infiltration |
Regular Waters: None required, although recharge and infiltration are strongly encouraged through better site design and stormwater credits. CGP Special Waters: Full infiltration of the excess runoff volume from the two year-24 hour storm event is one option contained in the CGP to meet the requirement for temperature control for trout streams. Other Sensitive Receiving Waters: Recharge recommended as a local option. Recharge may be restricted or prohibited in certain settings, as outlined in the Recharge and Infiltration Criterion below. |
| Water Quality (Vwq) |
Regular Waters: Apply MPCA Sizing Rule 1 or 3 in 2003 GCP, depending on BMP used. CGP Special Waters: Apply MPCA Sizing Rule 2 or 4 in 2003 GCP, depending on BMP used. Additional BMPs required under CGP Appendix A (B) for special waters. Other Sensitive Receiving Waters: Recommend expanded sizing criteria for most-sensitive lakes, trout streams (in CGP), susceptible wetlands and impaired waters, as described later in this section. |
| Channel Protection (Vcp) |
Regular Waters: No current state requirement. It is recommended that communities adopt a criterion for either 24-hour extended detention of the 1-year, 24-hour design storm or one-half of the 2-yr, 24-hr pre-development peak flow when revising or adopting local stormwater ordinances for peak flow control (and eliminate two-year peak discharge requirements). CGP Special Waters: One- and two-year design storm peak discharge and volume control required in four special water categories (wilderness, trout lakes, lake trout lakes, and scientific and natural areas). Other Sensitive Receiving Waters: 12-hour detention of water is recommended as the most for discharge to trout streams (to prevent heating), while other sensitive receiving waters should maintain the 24-hour minimum. |
| Overbank Flood (Vp10) |
Current Local Requirement: Varies, but typically involves either 10-year design storm peak discharge control, or a combination of 10- and 25-year design storm peak discharge control. CGP Special Waters and Other Sensitive Receiving Waters: No additional requirements. |
| Extreme Storm (Vp100) |
Current Local Requirement: Varies, but frequently involves 100-year design storm peak discharge control. In other cases, peak discharge control is waived if development is excluded from ultimate 100-year floodplain, or an acceptable downstream hydrologic analysis indicates it is not needed. Stormwater BMPs must be designed to provide safe overflow of the 100 year-peak discharge even if extreme storm control is not required at the site. CGP Special Waters and Other Sensitive Receiving Waters: No additional requirements. |