Laserfiche WebLink
The updated SEDCAD4 demonstration shows that with the revised number of storage <br />• years (650 years for the 2009 demonstration), the effluent from Pond 004 meets <br />the requirements of Rule 4.05.2(7). In addition, the updated SEDCAD4 <br />demonstrations shows that the pond satisfies the operational criteria of Rule <br />4.05.9(2)(b) and Rule 4.05.9(2)(c)(iii). <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/1]), or until there was approximately two feet of <br />elevation between the top of the sediment storage and the invert elevation of <br />the principal spillway (as recommended in the SEDCAD4 Design Manual and User's <br />Guide [Warner et al., 1998]). The storage year value was then set at the year <br />proceeding the year that the settleable solids concentration exceeded the <br />effluent limitation or for the last year the model indicated there was <br />sufficient storage for the sediment yield from the design storm. The SEDCAD4 <br />model results presented herewith reflect a (Y) value that allows for the <br />maximum sediment storage that is either just below the elevation which would <br />result in a settleable solids concentration in the pond discharge greater than <br />the water quality criterion or at an elevation which retains sufficient <br />• capacity to store sediment yield from the design storm event. <br />Pond 004 Summary <br />Total pond storage capacity (at principal spillway elevation) = 7.56 ac-ft <br />Principal spillway invert elevation (ft msl) = 6,948.2 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) = 4.0 ac-ft <br />Predicted sediment storage elevation (ft msl) = 6,946.2 ft <br />Number of storage years (Y) = 650 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 004 was originally <br />constructed as shown on Exhibit 7-12, Pond #004, 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 />TR-51 5 Revised 09/09