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Principal spillway invert elevation (ft ms1) = 7,385.0 ft <br />Total pond storage capacity (at principal spillway elev.) = 10.5 ac-ft <br />Storm predicted effluent peak settleable concentration = 0.0 ml/1 <br />Predicted annual sediment loading = <0.01 ac-ft <br />Predicted sediment storage capacity = 8.9 ac-ft <br />Predicted maximum sediment storage elevation (ft msl) = 7,383.1 ft <br />Number of storage years (Y) _ >500 years <br />The 25-year, 24-hour event SEDCAD demonstration presents a user input storage <br />volume that corresponds to the storage volume calculated in the 10-year, 24- <br />hour demonstration. This demonstration assumes the principal spillway is <br />clogged and, consequently, the peak stage and discharge are over estimated. <br />Spillways. In accordance with Rule 4.05.9(2), Pond 013 was designed and <br />constructed with both a principal and emergency spillway. Exhibit 13-17 <br />shows spillway locations and specifications. The principal spillway consists <br />of a 30-inch CMP riser that drops into a 24-inch CMP barrel pipe. The <br />spillway will keep the pond level at the 7,385.0 elevation. The SEDCAD4 <br />demonstration in Appendix 13-17.1-A shows, in accordance with Rule <br />4.05.9(2)(b), there is no discharge through the emergency spillway during the <br />10-year, 24-hour event. <br />The embankment portion of the emergency spillway consists of a 20-foot wide <br />trapezoidal channel, as shown on Exhibit 13-17. The invert elevation is at <br />7,387.5 feet, with a corresponding storage volume of 12.9 ac-ft. The <br />emergency spillway is constructed to safely pass the runoff volume from the <br />25-year, 24-hour storm (see Appendix 13-17.1-B). <br />Summary <br />The capacity of Pond 014 is attributed partially to the embankment and <br />partially to the pond excavation. During passage of the 10-year, 24-hour <br />storm the discharge through the principal spillway meets effluent <br />limitations. In addition, there is no flow through the emergency spillway. <br />The emergency spillway was designed and constructed to safely handle a storm <br />event equal too, or larger than the 25-year, 24-hour event. <br />Revised Storage Capacity Certification <br />I am a registered professional engineer in the State of Colorado experienced <br />in the design, construction and operation of earthen structures. I have <br />reviewed the storage capacity SEDCAD demonstrations. Exhibit 13-17, Pond 014 <br />As-Built, presents the existing configuration of the impoundment. The <br />earthen impoundment and spillway configuration are pre-existing and have been <br />certified by others (see Part II). <br />TR-37 13-17.1-4 Revised 02/08 <br />