2012-01-06_PERMIT FILE - C1982057 (6)

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Size Determination Once the existing size in acres of a topsoil pile location is determined, a required catchment basin capacity can be determined by utilizing SEDCAD. The capacities shown on Figure 13 -8 -1 are minimum required capacities and must be increased to allow for adequate freeboard. For a well vegetated topsoil stockpile (CN = 61), there is no runoff to contain until the watershed area of the stockpile is greater than 3.5 acres. See Addendum 1 for the SEDCAD input and output. Since there is no runoff from a 10 -year, 24 -hour storm event from these well vegetated stockpiles, a catchment sump is not required. Topsoil Stockpiles J, BB, TT, XX, and AAA require no catchment sumps however upon removal catchment ditches and sumps will be constructed. Topsoil Stockpiles PP, QQ, RR, and CCC require catchment sumps and ditches. Addendum 2 contains the SEDCAD inputs and outputs for these stockpiles. Construction The catchment basins will be field located based on existing topography to ensure that all runoff will be incepted and contained. All side slopes will be 1H: 1V or flatter and the minimum depth shall be 3.0 feet. Figure 13 -8 -1 shows a typical topsoil pile catchment basin. After construction, catchment sumps will be certified to ensure adequate capacity. Table 13 -8 -2 shows the design and actual capacity of the constructed catchment sumps. The as -built construction certification of the sumps for Topsoil Stockpiles PP, QQ, and RR are depicted on Exhibits 13 -8PP, 13 -8QQ, and 13- 8RR, respectively Catchment Ditches Catchment ditches may be utilized to contain runoff from SAE stockpiles to catchment sumps for containment. Ditches will be designed as an erodible, v -ditch channel with side slopes of 1 H: IV, and 0.3 feet of freeboard. Table 13 -8 -3 lists the catchment ditch design parameters. The catchment ditches will be routinely inspected for erosion and maintained to ensure adequate capacity. PR -06 13 -8 -2 Revised 10 /11