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INTRODUCTION In response to a new mine plan, which increased the disturbance area controlled by Pond 016, SCC proposed and designed a second pond to operate in series to effectively treat runoff from the mining disturbance area. Sediment Pond 016A was constructed in the NE'/. SE%., Section 27, TSN, R87W, fi[h P.M. just upstream from Pond 016. Consiruction was initiated in June 2003 and originally completed in July 2003. This As-Built Report is intended to serve as construction certification for the embankment and spillway only in accordance with Rules 4.05.6 and 4.05.9. The back slope of the impoundment began to experience slumping during the tall of 2003 and is not depicted on Exhibit 16-9C. The slumping does not currently affect the capacity or operating capability of the pond. However, SCC is evaluating methods of stabilizing this back slope and will initiate corrective action in 2004 EMBANKMENT AND EXCAVATION "ihe embankment is a homogeneous earth filled structure. The top width of the embankment is approximately 15 feet with an upstream slope of 3H:1 V and a downstream slope of The 3H:1 V principal spillway consists of a 48-inch CMP riser which drops into a 48-inch discharge CMP. The emergency spillway is a trapezoidal riprapped channel 50 feet wide fsee Exhibit 13-9C, Pond 016A As- Built). Due to the silty nature of the alluvial subgrade material at the embankment location, a keyway was constructed into impervious materials. The keyway for the embankment was constructed at a minimum 5 feet deep and 10 feet wide A portion of the pond capacity is a result of excavating topsoil and subgrade material below natural ground level. Suitable materials excavated from the pond area and associated side-slopes were used in the embankment construction. DESIGN ANALYSIS Pond 016A was designed to meet or exceed the design and performance requirements of CDMG while utilizing as much of the existing topography as possible. Sedimentation Pond O16A was designed and constructed to adhere to the following specifications: I. Provide storage and treatment for runoff from the 10-year, 24-hour storm event without experiencing any discharge through the emergency spillway; 2. Provide an emergency spillway capable of passing runoff from the 25-year, 24-hour storm event; 3. Provide adequate storage, in conjunction with Pond 016, for sediment generated as determined by SEDCAD analysis; 4. Provide a nonclogging dewatering device and principal spillway that will provide adequate detention time for the 10-year, 24-hour storm event. In some instances, mining will cause the drainage area to change during the life of the pond. When the mining into the watershed, the pit intercepts the runoff. In these cases a conservative pit move 1 3-51-1