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satisfies the operational criteria of Rule 4.05.9 (2)(b) and Rule <br />4.05.9(2)(c){iii). <br />The number of storage years (Y) uas increased in the aedimentology sub-routine <br />until the effluent settleable solids concentration in the pond discharge <br />exceeded the water quality criterion (0.5 milliliters per liter [ml/1]), or <br />until there was two feet of elevation between the top of the sediment storage <br />and the invert elevation of the principal spillway. The atorage year value was <br />then set at the year preceding the year that the settleable solids <br />concentration exceeded the effluent limitation or for the last year the model <br />indicated there was sufficient storage for the sediment yield from the design <br />storm. The SEDCAD4 model results presented herewith reflect a (Y) value that <br />allows for the maximum sediment storage that is either just below the elevation <br />which would result in a settleable solids concentration in the pond discharge <br />greater than the water quality criterion or at an elevation which retains <br />sufficient capacity to store sediment yield from the design storm event. <br />Pond 004 Summary <br />Total pond storage capacity (at principal spillway elevation) _ <br />Principal spillway invert elevation (ft msl) _ <br />Storm predicted peak settleable concentration = <br />Predicted annual sediment loading = <br />Predicted sediment storage (total volume) _ <br />Predicted sediment atorage elevation (ft msl) _ <br />Number of storage years (Y) _ <br />Certification Statement <br />7.55 ac-ft <br />6,948.2 ft <br />0.0 ml/1 <br />0.01 ac-ft <br />3.77 ac-ft <br />6,946.0 ft <br />600 years <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 004 was originally <br />constructed as shown on Exhibit 7-12, Pond #009 and certified by Ronald J. <br />Gehrke, a registered professional engineer in the State of Colorado <br />experienced in the design and construction of earthen structures. The <br />design and construction of the replacement principal spillway, an 8-inch <br />plastic corrugated straight pipe, approved under TR-37 in October 2005, was <br />supervised and certified by Robert J. Shevling, Colorado Registered <br />Professional Engineer, No. 37382. <br />TR-92 5 Revised 09/07 <br />