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• Sedimentation Basins <br />The proposed modification design consists of two sedimentation basins. Sedimentation basin <br />P-1 is proposed on the southwest corner of the site between 221St Avenue North and the landfill. <br />P-1 will accept the runoff from the western half of the modification including downslope <br />structures (DS-5, DS-6, DS-7, and DS-8) and stormwater discharge outlet from sedimentation <br />basin P-2. <br />Runoff from DS-5, DS-6, DS-7, and DS-8 will be routed to an open channel on the west side of <br />the landfill. Flow from the open channel will be routed along the western side of the landfill and <br />under the maintenance road through a 60" RCP before discharging into P-1. An 18" CPEP outlet <br />pipe from P-1 will control stormwater run-off discharge. Details of the outlet structure are <br />shown on the drawings. <br /> <br />P-2 is a proposed sedimentation basin on the southeast corner of the SDA between 221St Avenue <br />North and the landfill. P-2 will accept the runoff from the eastern half of the modification <br />including downslope structures (DS-1, DS-2, DS-3, and DS-4). A 12" CPEP outlet pipe will <br />transfer water into sedimentation basin P-1 before stormwater is routed off-site. Details of the <br />outlet structure are shown on the drawings. <br />The design parameters for the sedimentation basins are listed below: <br /> Bottom Top Elevation Inlet Outlet Total Storage <br />Pond Elevation (ft) (ft) Elevation (ft) Elevation (ft) Ca aci (ac-ft <br />P-1 986 998 989 957 17.6 <br />P-2 1006 1020 1010 908.5 25.1 <br />• <br />Ia3230\323008001\Reports\Application\Drainage Calculations -Surface Water Managemen[.doc <br />