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Pond 008 • <br />'This Sediment Pond 008 modification redesigns the principal and emergency <br />spillways. The elevation of the principal spillway orifice. will be at <br />elevation 7011.5 and the orifice reduced to 4.7 inches. Thca top of the <br />24-inch perforated riser pipe will be at elevation 7015.0. A trapezoid <br />channel, at elevation 7016.0, will replace the emergency spillway function <br />of the current riser pipe. No modifications are needed to the embanlanent. <br />Please refer to Dd~ibit 7-17B for the redesign of Pond 008 spillways. <br />DESIGN ANALYSIS <br />General <br />'The diversion ditch was designed to meet Colorado Mined Land <br />Reclamation Division regulations. The ditch and existing Fend 008 were <br />designed with the following in mind: <br />1. 'The ditch was designed to safely corrvey the runoff from the <br />10-year, 24-hour storm event. <br />2. Fond 008 had to continue to meet design requirements and all • <br />applicable CMLRD regulations as originally designed. <br />3. Pond 008 must have a separate principal and emergency spillway. <br />Hvdrolccrv <br />'The hydrology of the watershed was analyzed utilizing the SEDCIID+ computer <br />program. SIDG4D+ is an enhanced PC version of the SIDII~X7P II computer <br />program. Addendum 7-6f A contains a listing and description of the <br />SIDCAD+ input variables. In performing this analysis, the characteristics <br />of the m~*~~ite and reclamation procedures, along with on-site carlimr-+.+t <br />control procedures were considered. A complete listing of the SIDCIiD+ <br />inputs and outputs for the 10-year and the 25-year design storms are <br />provided. <br />• <br />7-6f-2 Revised 08/21/91 <br />