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\J -6- Pond A, a 48-inch reinforced concrete pipe (RCP) riser and a 36-inch conduit under the embankment were selected. The riser pipe will have six sets of four 5-inch diameter holes spaced at 1~-feet along the riser from elevation 6930 to 6938.5. For Ponds D, E, F, and G, a Type 2 riser was designed. It will be constructed of corrugated metal pipe (CMP) and have sets of four fl- inch diameter holes at two-foot spacing, beginning at specified elevations and extending along the riser height. For the remainder of the ponds, a Type 3 riser constructed of CMP was designed. The Type 3 riser has only one or two holes whose size and elevation vary for each pond. The risers are detailed on the LRCWE Plate I, Sedimentation Ponds, Energy Ptines No. 1 and 2, and Eckman Park. For Sedimentation Pond A, the riser elevation was set at one-half foot above the routed 10-year flood elevation. In addition to the riser holes, Pond A is provided with a 12-inch gated outlet at elevation 6920 feet to allow release of stored irrigation water. For all of the other ponds, the riser crest elevation was set at 0.1 foot above the 10-year flood elevation, The LRCWE Plate I Sedimentation Ponds, Energy Mines No. 1 and 2, and Eckman Park gives rating curves for the riser portion of the principal spillways for riser Types 1, 2, and 3. It also shows examples of the entire principal spillway rating curves for Ponds D and R which have Type 2 and Type 3 risers, respectively. Emergency Spillways In accordance with 30CFR816.46 (i), the 100-year 24-hour precipitation event was used to size the emergency spillway for each pond whose height (as mea- sured from upstream toe of embankment to emergency spillway) exceeded 20 feet, or whose storage volume exceeded 20 acre-feet. For those ponds not exceeding this criteria, the 25-year flood was utilized. In all cases, the emergency spillway crest elevation was set at one-foot above the riser crest elevation. For Pond A, a 5-foot diameter RCP was selected as the emergency spillway because the planned haul road immediately downstream From the dam . would not allow a weir type overflow. For all of the other ponds, a weir m Leonard Rice Consulting Waler Engineers, Inc.