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• <br />Sediment Pond 011 was constructed in the GWN, Fection 16, TSN, RB~W, 6th P.M. The <br />primary purpose of this pond and embankment will be to control runoff and sediment from <br />the mining disturbance area almost 2500 feet to the west of the pond. Construction was <br />initiated the last week of August 199 and r_omplet ed in the first week of October 199. <br />The embankment was ronsttucted with a he ri -ontal drainage system. A toe drain was <br />installed that will collect the water and discha rqe tt below the toe of the embankment. <br />This system is d=signed to act as controlled seepage Lh ro ugh the embankment. This <br />sedimentation structure will be maintainea until reclamation of this structure is <br />approved by the Colorado Di vl sien of Minerals b Geology ICDMG). <br />Ir,t roduction <br />Site Description <br /> Land 'JSe Sedimentation Pond 011 has a 141.E-acre watershed (see Exhibit 13-2). Thrs <br /> waCershe_d w111 be disturbed by mining activities as shown on Exhibits 12-1 and 20-1 and <br /> contempor aneously reclaimed as shown on Exhibit 19-1. T he land condition of the <br /> 'watershed was conserva[Svely based on the ma:<i mum disturbance at any one time within the <br />• proposed mining area, approximately 45 perce r.t undisturbed and 55 percent disturbed. <br />Embani:ment and Excavation The embankment is a homogeneous earth fill structure. The top <br />width of the ernbankmer.t is app roxi ma rely 20 feet with upstream slope of 3h:1v and <br />downs[[eam slopes of approximately ?. Ph:l v. The principal spillway consists of a 1?-inch <br />CM P: *_he emergency spillway is a trape~o idal channel 15 fee[ wide Isee Exhibit 13-SA1. A <br />portion of the pond rapacity was the result of excavating topsoil and material below <br />natural ground level. Excavated suitable material was used in embankment construction <br />and came from the pond log area and re la[ed side slopes. <br />Des ign Analysis <br />General Thts sedimentation pond was desiyn_d to meet or exceed the design and <br />performance reyui rements of CDMG while u[ili zi ng as much of the existing topography as <br />possible. Sedimentation Fond 0:1 was designed tc adhere to the following speciftcations: <br />1. Provide storage and treatment for the runoff fmm the 10-yea[, 24-hour storm event <br />• without experienci nq any discharge through the emergency spillway; <br />13-9A-1 Revised 12/12/9 <br />