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effluent does not need to meet settable solids standards. Therefore, Rule <br />• 4.05.6(3)(a) is not applicable. <br />The calculated peak stage from the 10 -year, 24 -hour storm event is 6,775.59 <br />feet. This elevation is 1.01 feet below the emergency spillway invert <br />elevation (6,776.6 feet). This demonstrates that no flow will pass through <br />the emergency spillway during the 10 -year, 24 -hour storm event. Therefore, <br />the impoundment as constructed and operated meets the intentions of Rule <br />4.05.9(2)(b). <br />The calculated 25 -year, 24 -hour storm event peak inflow is 6.42 cfs, while <br />the calculated peak discharge is 2.12 cfs with a corresponding peak stage <br />of 6,776.66 feet (see Addendum 7- 6g.1B). The emergency spillway <br />configuration was checked using the SEDCAD4 Channel Utility (see Addendum <br />7- 6g.1C) to show that the as -built configuration can safely pass the 25- <br />year, 24 -hour discharge. The channel utility shows a flow depth of <br />approximately 0.70 feet, which would be approximately 2.7 feet below the <br />top of the embankment (6,780.0 feet). If the principal spillway were to <br />clog, or become inoperable for some other reason, the SEDCAD4 modeling <br />• shows that the emergency spillway can safely pass the peak discharge from <br />the 25 -year, 24 -hour storm event. PECOCO Impoundment is constructed and <br />operated in compliance with Rule 4.05.9(2)(c)(ii). <br />Certification Statement <br />The earthen impoundment and spillway configurations are pre- existing. The <br />original design and modifications were prepared under the supervision of <br />others. The PECOCO Impoundment was originally constructed as shown on <br />Exhibit 7 -18, Proposed Permanent Impoundment Pecoco and certified by Ronald <br />J. Gehrke, a registered professional engineer in the State of Colorado <br />experienced in the design and construction of earthen structures. <br />I am a registered professional engineer in the State of Colorado <br />experienced in the design, construction and operation of earthen <br />structures. I have reviewed the as -built documents and inspected the site. <br />Exhibit 7 -18A, PECOCO Impoundment As- Built, presents the existing <br />configuration of the impoundment. It is in my opinion, based on the 2005 <br />survey data, that with the exception of the anti -seep collar, SCC has <br />completed the remedial actions presented on page 7 -6g -18 (and shown on <br />• <br />TR -37 4 Revised 10/05 <br />