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DESIGN ANALYSIS <br /> GENERAL <br /> Sedimentation Pond 004 was evaluated and constructed to meet or exceed the <br /> design and performance requirements of the Colorado Mined Land Reclamation <br /> Division while utilizing as much of the existing structure and topography <br /> as possible. Pond 004 was designed to adhere to the following <br /> specifications: <br /> 1. Provide storage for the runoff from the 10-year, 24-hour <br /> storm event without experiencing any discharge through the <br /> emergency spillway (0.19 ac-ft. ) . <br /> 2. Provide an emergency spillway capable of passing runoff from <br /> the 25-year, 24-hour storm event (0.25 ac-ft. ) . <br /> 3. Provide adequate storage for the sediment generated from the <br /> 10-year, 24-hour (MUSLE) storm event (3.1, 10-year, 24-hour <br /> MUSLE storm events or 0.035 ac-ft. ) . <br /> 4. Provide a nonclogging dewatering device and principal spillway <br /> that will provide adequate detention time for the 10-year, <br /> 24-hour storm event and still allow a method to dewater the <br /> pond to the 100 percent sediment storage level in a reasonable <br /> amount of time. <br /> HYDROLOGY <br /> The hydrology of the watershed was, analyzed by utilizing the SEDIMOT II <br /> computer modeling program. In performing this analysis, the <br /> characteristics of the minesite and reclamation procedures along with <br /> onsite sediment control procedures were considered. Addendums A, B, and <br /> C contain complete listings of the SEDIMOT II inputs and outputs for the <br /> 10-year, 25-year, and 100-year design storms, respectively. Table 1 is <br /> a summary of these results. <br /> TABLE 1 <br /> Design Hydrology and Sedimentology Summary <br /> Structure 004 <br /> DESCRIPTION 10yr-24hr 25yr-24hr 100yr-24hr <br /> Precipitation Depth 1.60-in. 1.80-in. 2.40-in. <br /> Inflow Runoff Volume 0. 19-ac-ft 0.25-ac-ft 0.45-ac-ft <br /> Pond Volume at Peak Stage 0.29-ac-ft 0.34-ac-ft 0.48-ac-ft <br /> Peak Stage 7.07 -ft 7.89-ft 9.42-ft <br /> 2 <br />