2009-05-13 PH - PFA/CWSRF - Laserfiche WebLink

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Stormwater Project Plan A. Project Description The proposed project focuses on developing best management practices for Centerville Lake as a part of the redevelopment of Centerville's downtown. Stormwater runoff is conveyed by an existing storm sewer system directly to Centerville Lake with no treatment as shown on the attached figure. The green infrastructure aspect of the project includes a new storm sewer system to convey downtown runoff to a proposed holding pond to be utilized for irrigation of an existing park facility. Centerville Lake is 303(d) listed by the MPCA as impaired for aquatic recreation due to total phosphorus loads. Rice Creek Watershed District (RCWD) notes that improvement of the lake for water-based recreation is one of the primary goals of the watershed. RCWD is currently in the process of a completing a TMDL study for Centerville Lake. Retrofitting best management practices with the proposed downtown redevelopment aligns with the goal of improving the water quality of Centerville Lake. The City wishes to leverage Green Infrastructure Funds along with its stormwater utility, RCWD Urban Stormwater Remediation Cost-Share Program grant, and Board of Soil and Water Resources Clean Water Legacy Grant for the first phase of the stormwater improvements. B. Project Service Area A key component of this project is installation of storm sewer and construction of a holding pond and irrigation system to meet Rice Creek Watershed District (RCWD) requirements. The project serves an approximately 22 acre drainage area (13.8 acres of impervious). Specifically, the features have been designed to capture 2.8 inches of runoff from the impervious surfaces. There is a significant decrease in the 2, 10 and 100-year proposed discharge rates from existing conditions. Table 1 lists the existing and proposed discharge rates to Peltier Lake and Clearwater Creek from the project area. Scenario Dischar a cfs 2- ear 10- ear 100- ear Existing 14.7 32.3 60.7 Pro osed 4.3 6.2 8.2 C. Project Location, BMPs, Construction Costs, Operations and Maintenance, Equipment Costs The project is located in the City of Centerville in Anoka County, specifically within the downtown area roughly bounded by Main Street to the north Goiffon Road to the east, bordering Heritage Street to the south and the property east of Progress Road as shown on the attached figure. A combination of BMPs is proposed including a new storm sewer system to convey runoff to the proposed holding pond, water re-use system, pervious pavement, rain gardens/bioretention. The holding pond allows for sedimentation prior to being utilized by the water re-use system for irrigation of an adjacent park area. The total estimated construction cost for the stormwater improvements is $852,863 as shown on the attached construction cost estimate. The City is requesting PFA funding for $549,913 of the total cost. Routine maintenance of the holding pond and water re-use system is to be completed by the City. Routine maintenance of the local BMPs within the downtown redevelopment is also to be completed by the City, except with small BMPs that may be proposed with the construction of private properties. (These private BMPs have not been included in the cost estimate). Holding ponds of this type have an estimated life cycle of 50-75 years. Estimated annual maintenance