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Introduction <br />• Sediment Pond 015 was constructed in the NE'/. SE, Section 23, TSN, R88W, 6th P.M. The <br />primary purpose of chrs pond and embankment will be to control runoff and sediment from <br />the mining disturbance area [o the southwest of the pond. Cons[rvction was initiated in <br />July 1999 and completed in September 1999. This sedimentation structure will be maintained <br />until reclamation of this structure rs approved by the Colorado Division of Minerals 6 <br />Geology ICDMG). <br />Embankment and Excavation <br />The embankment is a homogeneous earth fill et rucCUre. The top width of the embankment is <br />approximately 15 Eeec with upstream slope of 2.Sh:ly and downstream slope of 3.Sh:ly. The <br />principal spillway consists of an 18 inch CMP riser which drops into an 1B inch CMP; the <br />emergency spillway is a trapezoidal channel 10 feet wide (see Exhibit 13-9). A portion of <br />the pond capacity was the result of excavating topsoil and material below natural ground <br />level. Excavated suitable material was used in embankment const rucCion and came from the <br />ponding area and related side slopes. <br />• Design analysis <br />This sedimentation pond was designed to meet or exceed the design and performance <br />requirements of CDMG while utilizing as much of the existing topography as possible. <br />Sediment scion Pond o15 was designed to adhere to the following specifications: <br />1. Provide storage and treatment for the runoff from the 10-year, 24-hour storm event <br />without experiencing any discharge through the emergency spillway; <br />,.. Provide an emergency spillway capable of passing runoff from the 25-year, 24-hour <br />storm event; <br />3. Provide adequate storage for sediment generated as determined from the Sedcad+ <br />computer program. <br />4. Provide a nonclogging dewatering device and principal spillway that will provide <br />adequate detention time for the 10-year, 24-hour storm event and still allow a method <br />to dewater the pond dawn to the 100 percent sediment storage level in a reasonable <br />amount of time. <br />u <br />13-SD-1 04/00 <br />