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<br />No design or street grades are currently available for County Road 40. The <br />preliminary grading plans show assumed grades that work well for the <br />development plan. It is anticipated that the grading for the road would be do e <br />under a Sherbume County project. <br /> <br />X. STORMWATER MANAGEMENT <br /> <br />Stormwater management for the proposed development will be provided by <br />conveyance of runoff into 14 stormwater basins. The houses and street will d ain <br />to backyard swales and catch basins and then to a series of proposed ponds. <br />The ponds have been designed to not exceed the existing 2-year, 1 O-year an <br />1 DO-year outflow rates for the site. The ponds have been designed to NURP <br />standards requiring retention for the 2.5" design storm with a 10:1 bench at th <br />normal water level. The lowest floor elevations of the house pads are design d <br />to be at least one foot above the 1 DO-year design storm peak elevation. <br />Emergency overflow for the ponds is noted on the grading plans. The pond <br />design includes outlet control structures with submerged outlet pipes for <br />skimming. <br /> <br />Most of the soils have a low water holding capacity and relatively high rate of <br />water transmission. The soils in the area are very deep - most are greater th n <br />60 inches in depth - and the average depth to the water table is over 29 feet. <br /> <br />The existing drainage to the northeast discharges into a wetland which outlets to <br />Trott Brook. Existing drainage to the southeast is to a wetland. Existing <br />drainage to the west is to wetlands and then to Trott Brook. The proposed <br />drainage areas will follow the existing drainage pattems. <br /> <br />The normal water level and the 1 DO-year high water levels are noted on the <br />grading plans. <br /> <br />Best Management Practices will be utilized to control erosion during constructi n <br />and to restore vegetative cover on all disturbed areas. <br /> <br />XI. TRAFFIC ACCESS AND TRAILS <br /> <br />The major access to the development would be from County Road 40. The <br />proposed alignment cuts across the northeast comer of the project and contin es <br />south along the east project boundary. County Road 40, or Davis Street NW, s <br />currently a gravel street. Discussion with Dave Schwarting, Sherbume Count <br />Engineer, indicated that some federal funds should be available in about a ye r <br />for upgrading the road. The road would not be upgraded until development <br />generates the traffic to demand the upgrade. They are expecting city <br />participation in the form of right of way, storm sewer, and curb and gutter. <br /> <br />The initial phases of the development would get access from the existing Cou ty <br /> <br />F:\ENG\633001264\REPORTSIRlver Park Narratlve.426.doc <br /> <br />12 <br />