01-30-08 Additions - Laserfiche WebLink

Home Browse Search

Stormwater Management The existing storm sewer infrastructure is limited and storm water quality treatment is lacking. The existing storm sewer infrastructure draining the two cul -de -sacs (Meadowlark Lane and Kohlman Court) would likely be replaced and upgraded due to the pipe condition. The flared end outlets extending into Kohlman Lake would also be replaced. Also the existing low point located in Kohlman Lane accepts runoff from a large street area and the pipe transporting the storm water to Kohlman Lake will be analyzed for upgrades. A capacity analysis would be performed on all existing storm sewer pipe to see if pipe size increases are necessary. Before street runoff flows into the drainage system networks, a series of residential and regional rain water gardens in addition to sump structures are proposed to reduce the runoff rate and volume in addition to reducing total suspended solids and total phosphorus. Currently sixteen residents have signed up for the rainwater garden program which will aid in meeting requirements. Exhibit 6 shows the existing and proposed drainage infrastructure along with possible locations for large rainwater gardens. City staff will work closely with Ramsey - Washington Metro Watershed District (RWMWD) during the design phase to meet all applicable infiltration and treatment requirements. The current requirement is to infiltrate a 1 -inch rainfall over all new and disturbed impervious areas in order to get total suspended solid and total phosphorus reductions of 90% and 60% respectively. The current drainage system provides little to no treatment, therefore any treatment created as part of this project will improve the quality of runoff to Kohlman Lake, Gervais Lake, and surrounding wetlands. City staff will explore installing at least two to three larger rainwater gardens at select locations as well as continuing to promote individual rainwater gardens to residents. MISCELLANEOUS PRIVATE UTILITIES Private utility companies have been notified of the proposed improvement by city staff through a standard mailing. Utility coordination is of high priority especially with the proposed water main extension and additional sanitary sewer installation. Meetings will be held with all utility holders in the project area once the design process begins in order to identify utility conflicts and plan for utility relocation or upgrades if needed. EROSION CONTROL Erosion and sediment control methods will be implemented throughout the project. Silt fence, straw wattles, erosion control blanket, and other additional methods will be utilized where direct runoff might occur. Inlet protection will be used to protect both the existing and new catch basins during construction. Street sweeping will occur, as needed, on all paved street surfaces throughout the project, including intersecting streets. Watering of exposed soils and aggregate material would be done as a dust - control measure. An erosion and sediment control plan sheet and storm water pollution 7 17