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• The LRCWE Plate II, Hydrology and Hydraulics, gives rating <br />curves for the riser portion of the principal spillways. It <br />also shows an example of the entire principal spillway rating <br />curve for Pond A. <br />Emergency Spillways <br />In accordance with Rule 4.05.6(d), the 25-year, 24-hour <br />precipitation event was used to size the emergency spillway <br />for the Ponds. The emergency spillway crest elevation was set <br />at one-tenth of a foot above the top of riser elevation. For <br />all of the ponds, a weir-type overflow was used. The LRCWE <br />Plate II, Sedimentation Ponds, Hydrology and Hydraulics, <br />gives rating curves for representative weir-type spillways <br />ranging in length from 10 to 75 feet. The LRCWE Plate I, <br />Sedimentation Ponds lists the design frequency, the crest <br />• elevation, crest length, design depth and freeboard for the <br />emergency spillways for each of the ponds. <br />The peak discharge from the inflow design flood was used to <br />size the emergency spillway weir lengths without regard to <br />the attenuation of inflow that the reservoir together with <br />its primary spillway will achieve. This provides for a very <br />conservative emergency spillway design and adds to the factor <br />of safety for the ponds. The design depths for the spillways <br />were set at 1 foot and the emergency spillway freeboard to <br />the top of the embankment was set at one foot. <br />Emergency spillways will be constructed in cut around either <br />the right or left abutment, or over the crest of the <br />embankment as shown in LRCWE Figures 1-5, entitled Embankment <br />and Emergency Spillway Configuration. LRCWE Plate I, <br />Sedimentation Ponds, contains. summary information for each <br />• <br />Leonard Rice Consulting Water Engineers.lnc. <br />