Laserfiche WebLink
store water. This minimal amount of sediment storage capacity caused SCC to <br />• evaluate the need to clean the pond on a yearly basis. <br />To maximize sediment storage capacity the number of storage years (Y) was <br />increased in the sedimentology sub-routine until the effluent settleable solids <br />concentration in the pond discharge exceeded the water quality criterion (0.5 <br />milliliters per liter [ml/11), or until there was two feet of elevation between <br />the top of the sediment storage level and the invert of the principal spillway (as <br />recommended in the SEDCAD4 Design Manual and User's Guide [Warner et al., 1998]). <br />The August 2009 SEDCAD4 demonstration predicted minimal sediment yield (<0.01 so- <br />ft per year); consequently, the sediment capacity was a user input value which <br />maximized the sediment storage at two feet below the invert elevation of the <br />principal spillway. <br />The August 2009 SEDCAD4 demonstration shows that, with a user input storage <br />capacity of 3.9 ac-ft, effluent from Pond 008 meets the requirements of Rule <br />4.05.2(7). In addition, the updated SEDCAD4 demonstration shows that the pond <br />satisfies the operational criteria of Rule 4.05.9(2)(b) and Rule <br />4.05.9(2)(c) (iii). <br />• Pond 008 Summary <br />Total pond storage capacity (at principal spillway elevation) = 7.6 ac-ft <br />Principal spillway invert elevation (ft msl) = 7,015.3 ft <br />Predicted peak settleable concentration (outflow) = 0.0 ml/l <br />Predicted annual sediment loading = < 0.01 ac-ft <br />Predicted sediment storage (total volume) = 3.9 ac-ft <br />Predicted sediment storage elevation (ft msl) = 7,013.3 ft <br />Number of storage years (Y) = > 500 years <br />Certification Statement <br />The earthen impoundment, principal spillway and emergency spillway are pre- <br />existing. The original design, as-built plans and modifications were <br />prepared under the supervision of others. Pond 008 was originally <br />constructed as shown on Exhibit 7-17A, Sediment Pond 008 As-Built, which was <br />certified by Ronald J. Gehrke, a registered professional engineer in the <br />State of Colorado experienced in the design and construction of earthen <br />structures. The trapezoidal emergency spillway was constructed in 1992 as <br />• shown on Exhibit 7-17C, Sediment. Pond 008 As-Built, and which was certified <br />by Mike Alltavia, a registered profession engineer in the State of Colorado <br />TR-51 5 Revised 09/09