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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 rock riprap <br />lined trapezoidal channel, underlain with Mirafi 600X geotextile, as shown on <br />Exhibit 13-5C. The invert elevation is at 7,431.4 feet. The emergency <br />spillway is constructed to safely pass the peak discharge from the 25-year, <br />24-hour storm (see Addendum 13-19.1-C). <br />Summary <br />The capacity of Perd O11A is attributed partially to the embankment and <br />partially to the pond excavation. There is no flow through the emergency <br />spillway as a result of the 10-year, 24-hour storm event. The emergency <br />spillway was designed and constructed to safely handle a storm event equal <br />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 postmine condition SEDCAD demonstration. Exhibit 13-5C, As- <br />Built Pond 011A, 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 />This postmine sediment storage capacity addendum confirms that the pond <br />configuration and sediment storage capacity meet or exceed the Rules and <br />Regulations of the Colorado Mined Land Reclamation Board for Coal Mining. <br />\\\\\\\\~~~~~~0~~~ ~R~E lC/ ~~~~~j///// <br />C,~~~ 1.727 <br />t C~%~, ~ <br />j ~ ~_ ~ <br />% S '• <br />~~~~~ 111/~~~i~II1111\~~~~~~~~~ <br />///~~/ I <br />~~ r~. g~~ s~~-os <br />• Curtis M. Belden Date <br />Colorado P.E. 17274 <br />TR-37 13-19.1-4 Revised 08/08 <br />