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below natural ground level. Excavated suitable material was used in embankment construction. Excess material was wasted. The pond side elopes are 2h:Lv or flatter. For Phase III, no further excavation of the pondinq area is necessary. DESIGN ANALYSIS General. Sediment Pond 006 vas redesigned to meet or exceed the design and performance requirements of Colorado Mined Land Reclama tlon Division vhlle ut111z1 ng as much of the existing topography as possible. Sediment Pond 006 vas designed to adhere to the following specifications: 1. Provide storage and treatment for the runoff from the 10-year, 24-hour storm event without experiencing any discharge through the emergency spillvay; 2. Provide an emergency spillvay capable of passing runoff from the 100-year, 24-hour storm event; 3. Provide adequate storage for sediment generated as determined from the SEDCAD+ conpu[er program. Hyd rology. The hydrology of the watershed was analyzed utilizing the SEDCAD+ computer program. SEDCADt Ss an enhanced PC version of the $EDIMOT II computer program. Tab 13, Attachment 13-1, Addendum 1 contains a listing and description of the SEDCAD+ input variables, In performing thla analysis, the characteristics of the mineslte and reclamation procedures along with on-site sediment control procedures were considered. A complete listing of the SEDCADi inputs and outputs for the 10-year, 25 year and the 100- year design storms are provided Sn Attachment 13-4 C, Addendum 1. TABLE 13-4C-1 DESIGN HYDROLOGY AND SEDIMENTOLOGY SU)91SAY POND 006 - PHASE III Description lOYr. -24Hr. 25Yr.-29Hc. 100Y c.-24Hr. Precipitation Depth 1.7 in. Inflov Runoff volume 12.69 ac-ft Pond Yoluma at Peak Stage 17,47 ac-ft Peak Stage 7070.7 Peak Inflow Rate 99.24 cfs • 2.1 Sn. 2.5 Sn. 20.90 ac-ft 30.86 ac-ft 21.61 ac-ft 22.89 ac-ft 7072.7 7073.3 197.03 cfs 215.98 cfs 2 Revised 09/29/95