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of <br />Written by: JOE TAM Date: 22 -Oct -99 Reviewed by: _ Date: Q <br />Client: Allied Waste Project: Forward Landfill Project/Proposal No.: WS0264 Task No.: Ol <br />Sheet Flow: <br />Cover - Use "Grass: Short" <br />Length (L) - Taken from Figure 1 <br />Slope (s) - Taken from Figure 1 <br />2 -year, 24-hour rainfall (P2) - 1.51 in (see Attachment A) <br />Open Channel Flow: <br />Ditch Cross Section - Chosen to accommodate design flow <br />Culvert Diameter - Chosen to accommodate design flow <br />Length (L) - Taken from Figure 1 <br />Slope (s) - Taken from Figure 1 <br />Manning's Roughness Coefficient (n): (see <br />n = 0.03-0.2 for low-retardance grass lining (Class D) [ASCE,1992] <br />Note: For grass lining, n varies with the product of velocity and hydraulic radius <br />n = 0.015 for asphalt -lined ditches [ASCE, 1992]. <br />n = 0.035 for articulated concrete blocks (maximum roughness for riprip [ASCE, 199 <br />0 <br />n = 0.012 for smooth interior wall HDPE culverts [ADS, 1995] <br />n = 0.024 for corrugated metal pipe [AISI, 19941 <br />Parameters for Ditches and Culverts (Conduits) <br />See "Open Channel Flow" in the previous section. <br />CI„lver-'r e_A-.ravIce I;��s t � Ec;e��S art;�cw.-�C�r��n�"B, <br />The HydroCAD output files for the 100-year/24-hour storm analysis are presented in Attachment 3. <br />The peak discharges from the 100-year/24-hour storm were used to design the ditches and drainage <br />pipes. The minimum ditch depths for 2H:1 V ditch slopes are shown on Table 1. The minimum pipe <br />diameter and design slope are summarized on Table 2. <br />n <br />MALLIEDWASTMFORWARD WMU B\CLOSURE PLAN\DRAINCALCS\SW2.DOC <br />