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Size Determination • <br />Once the existing size in acres of a topsoil pile location is determined, a required <br />catchment basin capacity can be determined by utilizing SEDCAD The capacities shown on <br />Figure 13-8-1 are minimum required capacities and must be increased to allow for adequate <br />freeboard. For a well vegetated topsoil stockpile (CN = bt), there is no runoff to <br />contain until the watershed area of the stockpile is greeter than 3.5 acres. See Addendum <br />1 for the SEDCAD input and output. Since there is no runoff from a 10-year, 24-hour <br />storm event from these well vegetated stockpiles, a catchment sump is not required. <br />Topsoil Stockpiles A, C, D, E, F, G, T45, 86, and J require no catchment sumps. Topsoil <br />Stockpiles PP, DO, and RR require catchment sumps and ditches. Addendum 2 contains the <br />SEDCAD inputs and outputs for these stockpiles. <br />Construction <br />The catchment basins will 6e field located based on existing topography to ensure that all <br />runoff will be incepted and contained. All side slopes will be th:1v or flatter and the <br />minimum depth shall be 3.0 feet. Figure 13-8-1 shows a typical topsoil pile catchment • <br />basin, After construction, catchment sumps will be certified to ensure adequate capacity. <br />cable 13-8-2 shoos the design and actual capacity of the constructed catchment sumps. the <br />as-built construction certification of the sumps for Topsoil Stockpiles PP, 00, and RR are <br />depicted on Exhibits 13-BPP, 13-800, and 13.8RR, respectively. The catchment basins will <br />be reclaimed the same as a containment ditch or sedimentation pond according to the <br />approved permit when no longer required to control runoff. <br />Catchment Ditches <br />Catchment ditches may be utilized to contain runoff from SAE stockpiles to catchment sumps <br />for containment. Ditches will be designed as en erodible, v-ditch channel with side <br />slopes of 1h:ty, and 0.3 fee[ of freeboard. Table 13-8-3 lists the catchment ditch design <br />parameters. The catchment ditches will be routinely inspected for erosion and maintained <br />to ensure adequate capacity. The catchment ditches will be reclaimed when the topsoil <br />stockpile is removed. <br /> <br />13-8-2 Revised 11/05/93 <br />