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-7- <br />t>Pe overflow was used. The LRCWE Plate II Sedimentation Ponds, Hydrology <br />and Hydraulics, gives rating curves for the 5-foot diameter spillway and <br />representative weir type spillways ranging in length from 15 to 75 feet. <br />The LRCWE Plate I, Sedimentation Ponds, Energy Mines No. 1 and 2, and Eckman <br />Park lists the design frequency, the crest elevation, crest length, design <br />depth and freeboard for the emergency spillways for each of the ponds. <br />For Pond A, the 100-year flood was routes using standard reservoir routing <br />techniques to determine the maximum ponding elevation and dam freeboard. <br />LRCWE Plate II1, Sedimentation Pond A, Hydrology and Hydraulics shows the <br />inflow and routed outflow for the 10-year, 100-year and PMP floods. For the <br />li other reservoirs, a more conservative approach was taken. The peak dis- <br />charge from the inflow design flood was used to size the emergency spillway <br />weir length without regard to the attenuation of inflow that the reservoir <br />together with its primary spillway will achieve. This provides for a very <br />conservative emergency spillway design and adds to the factor of safety for <br />the ponds. The design depth for the emergency spillway on Pond A is 3.3 <br />feet. The design depths for the other ponds was set at 1 or 2 feet depending <br />on the spillway length and other factors. Emergency spillway freeboard to <br />the top of the reservoir for Pond A was 2.7 fee[ and is very close to 1-foot <br />for all of the other ponds. <br />Emergency spillways will be constructed in cut, around either the right or <br />left abutments, or over the top of the embankment. LRCIdE Figure 1, Example <br />of Emergency Spillway in Cut and LRCWE Figure 2, Example of Emergency Spill- <br />way over illustrate both concepts. The weir type spillway will be provided <br />with 27-inches of 18-inch riprap to the anticipated design depth. It is <br />recommended that erosion protection be provided at each site. <br />Energy Dissipators <br />Riprap energy dissapators will be provided at the outlet ends of all primar}• <br />outlet works. The LRCWE Figure 3, Typical Primar;~ Spillway Energy Dissapator <br />illustrates the protection to be provided, but it is recommended that approp- <br />riate erosion control methods be utilized for each site. <br />Permit Renewal No. 3 Exhibit Sq 1/IS/00 <br />Paee 9 oC?? <br />