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XX. Water Quality and Surface Water Management In the 1997 EA W, the Twin Lakes Plan would reduce storm water runoff over the development parcels and public roadway areas by 2.31 acre-feet from 39,27 acre-feet to 36.96 acre feet during a 10-year, 24-hour event. The new development would reduce storm water runoff over the development parcels and public roadway areas by 3,25 acre-feet from 55,17 acre-feet to 51.92 acre - feet during a 100-year, 24-hour event. The above runoff estimates are based on an average impervious coverage ratio of 90% currently and 80% under the proposed conditions, The majority of existing development consists of trucking facilities that include bituminous surfacing over 90% - 100% of parcel areas, and office, dispatching, and loading buildings. A goal of new development will be to require approximately 20% of a parcel to be pervious, landscaped surface. The quality of site runoff will be improved due to connection of redeveloped parcels and proposed roadways to storm water treatment basins located adjacent to the project area, The basins will intercept site runoff and remove pollutants and sediment prior to discharging into receiving waters. No ponding of site runoff occurs under the existing conditions. An effective means of reducing the amount of pollutants discharged into the receiving stream/water body is to provide sedimentation ponds at the outfall of the storm sewers. The Twin Lakes Area lies entirely within the jurisdiction of the Rice Creek Watershed District. Runoff from the site areas west will be routed through storm water treatment ponds prior to discharging into natural water bodies. The ponds provide pollutant removal and will reduce peak discharge rates to be less than the pre-existing peak runoff rates into receiving waters, Drainage from the project area is divided into three separate drainage basins, the western, central, and eastern as described below, The western drainage area includes approximately 50 acres located between Prior Avenue and Cleveland Avenue and between County Road C and County Road C-2 in the project area. Runoff from approximately 18 acres of the Centre Pointe development and an existing 6 acre parcel east of Cleveland Avenue will also be treated in the western pond. The western drainage area pond is situated directly north of and outlets to a wetland (DNR #62-50) located between Cleveland Avenue and I-35W. The western pond meets all National Urban Runoff Program (NURP) standards. This pond has a surface area 2.1 acres and permanent pool storage volume of 12,5 acre-feet. No additional ponding facilities are anticipated for this drainage area. The central drainage area includes approximately 18 acres from parcels 14 through 19 and 50 acres of existing redeveloped parcels located between Prior Avenue and Fairview Avenue and between County Road C and Terrace Drive. Runofffrom approximately 20 acres ofland located south of County Road C is also directed to the central drainage area through existing storm sewer. The central drainage area pond outlets to Langton Lake (DNR #49W) and is located along the southeast 19