2020_07-28_PWETCpacket - Laserfiche WebLink

Home

Describe stormwater pollution prevention plans including temporary and permanent runoff controls and potential BMP site locations to manage or treat stormwater runoff. Identify specific erosion control, sedimentation control, or stabilization measures to address soil limitations during and after project construction. Existing conditions stormwater on the project site flows to a private storm sewer system on the property that connects to the public storm sewer system within County Road B2 at Snelling Avenue. The public storm sewer is conveyed to Little Lake Johanna, which is an impaired water. There is very minimal pervious surface coverage (about 5.5 acres), and it is mostly located within parking lot islands and around the perimeter of the parking fields. Total existing impervious area within the project site is approximately 67.3 acres. As part of the proposed project, stormwater will be managed on site with a series of underground stormwater filtration systems. The project will be designed to maintain the current drainage patterns to the public storm sewer system. The proposed development will require compliance with the standards of the Rice Creek Watershed District and the City of Roseville for water quality, volume control, rate control, and erosion control. As required by the City and Rice Creek Watershed District, the quantity and rate of stormwater runoff from the 2-, 10-, and 100-year, 24-hour rainfall events in post - development conditions will be managed to not exceed the existing conditions. Infrastructure will be constructed to convey stormwater to proposed underground stormwater filtration basins, which will be designed to help achieve this water quantity requirement. The soil across the project site has generally low permeability rates and is not suited for infiltration. The required treatment volume is determined by the Rice Creek Watershed District and is a function of new impervious area. Due to the low permeability rates, Rice Creek Watershed District will require all development within the project site to provide filtration (volume reduction) for 2 inches of runoff from all proposed impervious areas (streets, buildings, parking areas, driveways, etc.). The proposed filtration basins will be required to drawdown within 48 hours after a rainfall event. Stormwater modeling of runoff will be completed as part of the final design of the project. The modeling will be performed to ensure conformance to all City of Roseville and Rice Creek Watershed District standards. With the construction of the project, a Stormwater Pollution Prevention Plan (SWPPP) will be created and used to prevent erosion and stabilize the site during and after project construction. The SWPPP will document that the sitework contractor is to immediately initiate stabilization of exposed soil areas and complete the stabilization within seven calendar days after the construction activity in that portion of the site temporarily or permanently ceases. The SWPPP will also direct the contractor to construct temporary sediment basins for common drainage locations that serve an area with five or more acres disturbed Rosedale Center EAW 9 February 2020