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4. Provide a nonclogging dewatering device and principal spillway that will provide • adequate detention time for the 10-year, 24-hour storm event and still allow a method to dewater the pond down to the 100 percent sediment storage level in a reasonable amount of time. Nvdroloov. The hydrology of the watershed was analyzed utilizing the SEDCAD computer program. SEDCAD is en enhanced PC version of the SEDINOT II computer program written by Civil Software Design of Lexington, Kentucky. Tab 13, Attachment 13-1, contains a listing end description of the SEDCAD input variables. In performing this analysis, the eharacteristice of the minesite and reclamation procedures along with on-site sediment control procedures were considered. Addendums A and B contain a complete listing of the SEDCAD inputs and outputs for the 10-yesr end the 25-year design storms. Table 13-SA-1 Contains the design hydrology summary. TABLE 13-SA-1 DESIGN XYDROLOGY POND 009 \~1'CPreeipitation Depth p~ ~u Inflow Runoff Volume v~ Pond Volume at Peek Stage •~ Peek Stage ~ ~~ ~ o~ 'Peek Inflow Rete \Y ~~?' Peak Discharge Rete ~~ 1.6 in. 2.1 in. 3.46 ae-ft 9.27 ac-ft 1 rryvnoS~ol 9,q ( 8.00 ac-ft iS. fT(v 12.76 ec-ft ~O$}• O 7086.8 X091 7090.4 8.59 tfs 44.92 cfs 5, 03 4.87 cfs 33, 3(v 27.74 cfs Input consists of precl pi Cation amount (inches), watershed area (acres), time of concentration (hours), runoff curve number (CN), representative particle-size distri butione of soils in the area, sedimentology information, spillway information, etc. The drainage area for this sediment pond was measured on a 1"=400' topographic map (see Exhibit 13-2). In some instances, mining will cause the drainage area to Change during the life of the sedimentation structure. Yhen the pit moves into the watershed, runoff is intercepted by 13-SA-2