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

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Stormwater Project Plan A. Project Description The proposed project includes street and utility improvements on Peltier Lake Drive which is tributary to Peltier Lake and 73rd Street which is tributary to Clearwater Creek. Stormwater runoff is conveyed by an existing storm sewer system directly to Peltier Lake and Clearwater Creek with no treatment as shown on the attached figure. Peltier 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 and protection of the creek by promoting retrofits is one of the primary goals of the watershed. RCWD is currently in the process of a completing a TMDL study for the Peltier Lake and Clearwater Creek. Clearwater Creek is listed as impaired for aquatic life by the MPCA based on fish and aquatic macroinvertabrate bioassessments. Retrofitting best management practices with the proposed street improvement project aligns with the goal of improving the water quality of both Peltier Lake and Clearwater Creek. B. Project Service Area A key component of this project is installation of storm sewer and a combination of surface and subsurface infiltration and filtration features to meet Rice Creek Watershed District (RCWD) requirements. A total of 18 depressed filtration BMPs are proposed in the existing road right-of- way. The project serves an approximately 36 acre drainage area. Specifically, the features have been designed to capture 0.8 inches of runoff from connected impervious surfaces. There is a 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 Peltier Lake Discharge (cfs) Clearwater Creek Discharge (cfs) 2- ear 10- ear 100- ear 2- ear 10- ear 100- ear Existin 53.0 96.2 149.7 29.0 50.3 76.3 Proposed 45.1 85.5 139.1 24.2 46.8 73.2 C. Project Location, BMPs, Construction Costs, Operations and Maintenance, Equipment Costs The project is located in the City of Centerville in Anoka County, specifically on Peltier Lake Drive and 73rd Street as shown on the attached figure. A total of 18 depressed filtration BMPs are proposed. Runoff enters the BMPs from the streets through a curb cut and a turf grass filter strip for pretreatment. The BMPs consist of a surface depressed area approximately one foot deep and a 2.25 foot deep below ground sand/compost mix. Draintile has been provided due to the clayey, poorly draining soils. The total estimated construction cost for the Stormwater improvements is $817,397 as shown on the attached construction cost estimate. The BMPs are proposed to be seeded with a Minnesota Department of Transportation (MnDOT) moveable seed mix to minimize annual maintenance costs. Routine maintenance is to be completed by the homeowners. Filtration BMPs of this type have an estimated life cycle of 20-30 years. Assuming replacement of the sand filter and vegetation every 20 years, the estimated annual maintenance cost is $4,000. There are no equipment replacement costs associated with this project.