2012 07-17 CCP - Laserfiche WebLink

Home

c. Stormwater facilities must provide: 1. An identified overflow spillway and downstream route sufficiently stabilized to convey a 100-year critical storm event; 2. Pond outlets designed to prevent short circuiting of the flow from pond inputs to the outlet; 3. A minimum depth for ponds of three (3) feet and conform to the design specifications of the Stormwater Manual, 2005. 4. An outlet skimmer to prevent migration of floatables and oils for the 2- year event; and 5. Access for future maintenance that is free of plantings and impediments. d. Regional ponds and practices can be used to provide for stormwater management based on the following criteria: 1. Regional ponds are required to be designed based on ultimate conditions for the contributing subwatershed. 2. Regional ponds are required to be constructed and operational prior to constructing imperviousness within the contributing drainage area. e. Design of all Best Management Practices (BMPs) will be consistent with the Minnesota Stormwater Manual, 2005, and as amended and the MPCA General Permit for Construction Activities, 2008, and as amended. f. When using infiltration for volume control, infiltration volumes and facility sizes shall be calculated using the appropriate hydrological soil group classification and infiltration rate, and shall be capable of infiltrating the required volume within 72 hours or as specified in the MPCA General Permit for Construction Activities. g. In evaluating the infiltration capacity of a constructed BMP under post - development conditions, the infiltration rates in the Minnesota Stormwater Manual should be used. Select the design infiltration based on the least permeable soil horizon within the first five (5) feet below the bottom elevation of the proposed infiltration facility. Site -specific infiltration measurements completed by a licensed professional (as described in the Minnesota Stormwater Manual, November 2005, and as amended) may be used in place of the values in the Minnesota Stormwater Manual, and as approved by the City. h. All stormwater retention practices designed to meet the volume control regulation must provide pretreatment of stormwater runoff prior to infiltrating into the groundwater system or discharging downstream. Pretreatment methods must comply with the Minnesota Stormwater Manual, 2005, and as amended, for the proposed practice. All highly recommended and recommended design criteria must be met, unless specifically waived by the Technical Commission of VLAWMO or RWMWD, as appropriate.