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Pond 5/6 <br />RoCkcastle proposes to backfill the south end of Pond 5/6 at a 5H:1 V slope to <br />provide livestock access and to stabilize the surfical slump on the east side of the <br />pond. In addition, Rockcastle proposes to remove the existing riser and culvert <br />which extends through the embankment and replace it with a riprapped trapezoidal <br />emergency spillway. The emergency spillway is designed to safely pass the runoff <br />from a 25-year, 24-hour event. <br />The new pond configuration will meet all requirements for permanent <br />impoundments in accordance with Rule 4.05.9 (1). The pond design and <br />stage/storage curve are shown on the Pond 5/6 Design Map (Map R-4). the <br />following summarizes the Revised Pond 5/6 design: <br />Elevation Emergency Spillway Invert (ft) 7415.4 <br />Dead Storage (ac-ft) 1.27 <br />• Elevation Maximum Water Level 25-Year, 24-Hour Event(ft) 7416.3 <br />Elevation Top of Structure 7417.4 <br />Freeboard (ft) 1.1 <br />The emergency spillway capacity was calculated using Mannings Equation for <br />Open Channel Flow. The results are shown on the Pond 5/6 Design Map (Map <br />R-4). <br />Riprapped Road Crossings <br />Rockcastle will locate and remove all culverts on all pit access roads and replace <br />them with riprapped road crossings. Road crossings will be lined with riprap <br />(Minimum D~ = 3 inches), and will function as California Crossings. The <br />riprapped sections will protect the ditches from damaged by vehicular traffic. Ditch <br />sideslopes will be laid back in the crossing area to an approximate 5H:1 V slope <br />to facilitate vehicular access. <br /> <br />20 <br />