06-24-2024 Council Packet - Laserfiche WebLink

Home Browse Search

23-2129 SUNRISE OVER GERVAIS Site Drainage Narrative Date: December 28, 2023 This project proposes the subdivision of a 2.04-acre property into four single-family residences in the City of Little Canada in Ramsey County. The project site’s current address is 2395 Sunrise Avenue, Little Canada, MN 55117. The site is located within the Ramsey Washington Metro Watershed District (RWMWD). NOTE: NOAA Atlas 14 rainfall data is being used for this drainage report: 2-year 2.81 -in 10-year 4.19 -in 100-year 7.39 -in Modeling uses MSE Type 3 storm distribution. Existing Conditions The existing site contains short vegetative cover and a few trees. With regards to the drainage areas, the total drainage area analyzed is approximately 2.80 acres. Approximately 0.81 acres drains to the West to a wetland while another 1.99 acres (approx.) in the middle and eastern portion of the site that includes runoff from the adjacent public roads that enters a ditch along Edgerton and is discharged Northward. The only existing impervious surfaces include an existing residence south of the property to be split, its driveway, and portions of Sunrise Avenue and Edgerton adjacent to the property. The peak flow rates were assessed at the two discharge points from the site (to the West and to the North). A USDA NRCS web soil survey shows that the site mainly consists of Hayden fine sandy loams and Urban land-Hayden-Kingsley complex in the construction limits. These soils are typically modeled as HSG “B” type soils. Based on the currently available data, HSG B curve numbers have been selected. Proposed Conditions The same area was analyzed under proposed conditions. The majority of the surface runoff from the proposed private driveways and roof drainage will be collected and routed to two stormwater basins (both infiltration-type features) to undergo treatment prior to discharging into the existing ditch. The BMPs are designed to provide volume and rate control; post-construction run-off volume shall be retained on site for 1.1 inches of run-off from all impervious surfaces on the site.