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INTRODUCTION <br />Sedimentation Pond 002 is an earthen embankment structure constructed by <br />Peabody Coal Company in the mid-1970's as a temporary sediment structure <br />to control runoff and sediment from the disturbed areas of the Nucla <br />Mine. In 1986, Sedimentation Pond 002 was redesigned and subsequently <br />approved by CMLRD. The remedial work was completed in November, 1987. <br />Sedimentation Pond 002 is located in Section 31 of Township 47 North, <br />Range 15 West, Northwest of the town of Nucla, Colorado (see Exhibit <br />13-4). <br />SITE DESCRIPTION <br />LAND USE <br />Sediment Pond No. 002 has a 7.69-acre watershed that is tributary to <br />Tuttle Draw. This watershed is classified as approximately 96 percent <br />reclaimed and 4 percent undisturbed juniper-grassland. <br />• EMBANKMENT <br />The existing embankment is a homogeneous earth fill compacted in lifts <br />to design specifications. The top width of the embankment is a minimum <br />12 feet wide with upstream and downstream slopes of approximately 3H:1V, <br />respectively. The existing spillway consists of a 12-inch diameter drop <br />inlet corrugated metal pipe with a 0.5-inch diameter hole located at the <br />100 percent sediment storage level. <br />DESIGN ANALYSIS <br />GENERAL <br />Sedimentation Pond 002 was evaluated and constructed to meet or exceed <br />the design and performance requirements of the CMLRD while utilizing as <br />much of the existing structure and topography as was possible. Pond 002 <br />was constructed to adhere to the following specifications: <br />1. Provide storage for the runoff from the 10-year, 24-hour <br />precipitation event without having any discharge through the <br />• emergency spillway (0.26 ac-ft.). <br />1 <br />