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2. Provide an emergency spillway capable of passing runoff from the 100-year, 24-hour ~~ storm event; 3. Provide adequate storage for sediment generated ae determined from the Sedcad+ computer program. 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. HW rology. The hydrology of the watershed was analyzed utilizing the SEDCAD+ confuter program. SEDCAD+ is an enhanced PC version of the SEDIMOT II con~utez program written by CSv11 Software Design of Lexington, Kentucky. Tab 13, Attachment 13-1, contains a listing and desc rlptlon of the SEDCAD+ input va rl ables. In performing this analysis, the characterSstlcs of the mineslte and reclamation procedures along with on-site sediment control procedures were considered. Addendums A, B, and C contain a complete listing of the SEDCAD+ Snpu[s and outputs for the 10-year, 25-year, and the 100-year design storms. Table 13-3-1 contains the design hydrology summary. TABLE 13-3-1 DESIGN HYDROLOGY SU144ARY POND 010 Description 10-Y r, 29-Hr 25-Yr,24-Nr 100-Yr,2d-Hr Precipitation Depth 1.7 Sn. 2.1 Sn. 2.5 in. Inflow Runoff Volume 18.3 ac-ft 28.1 ac-ft 40.1 ac-ft Pond Volume at Peak Stage 19.6 ac-ft 26.5 ac-ft 28.3 ac-ft Peak Stage Elevation 6788.5 6790.6 6791.1 Peak Inflow Rate 109.3 cfs 167.6 cfs 232.9 cfs Peak Discharge Rate 29.0 cfs 113.5 cfs 169.9 cfs Input consists of precipitation amount (inches), watershed area (acresl, time of concentration (hoursl, runoff curve number (CN1, representative particle-size distributions of soils Sn the area, sedlmentology information, spillway information, etc. The drainage area for this sediment pond was measured on a 1"=400' topographic map (see Exhibit 13-21. 13-3-2 Revised 09/OB/95