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III IIIIIIIIIIIIIIII s~~: ~~`~'` ~ <br />Doc Date:12/11/2001 ~~ <br />• <br />Technical Revision 7 <br />N OV C-94-024 <br />Canadian Strip Mine, C-81-026, Pond 1 <br />Review of Emergency Spillway Riprap <br />Requirement <br />X.'CGL~.'PC'v:P^.0.Tv'R'd9l~RmVF4SRSC3.'&YtYUlW.~K.~.)`:v:N.:w`~a<c'..w.w.n:~%:NM"N:Ran'G~iGK+nVR~..W'T'~CtQ.F3::o'A^F~+~ae4:Y.h~:G'0:a::Gn:"v.:n~.iue::.:w`:(n4:v:a,.iSe::Um:.:n:ii.:?ia,<q'.i.::.:p>:d[tl96) <br />1. INTRODUCTION <br />1.1 Methods of Analysis <br />This review and analysis was made using the Sediment, Erosion, Discharge by Computer Aided Design <br />(SEDCAD+ Version 3) developed by Ms. Pamela J. Schwab of Civil Software Design and Dr. Richard C. <br />Warner, Agricultural Engineering Department, University of Kentucky. The analysis was performed by <br />Catherine Begej, of Greystone, and was based on permit documentation and Feld reports. The analysis was <br />reviewed and a site visit made by the undersigned. <br />• 1.2 Project Description <br />The project was to review the requirement for tiptop in the emergency spillway of Pond 1. The original design <br />of the pond called for tiptop. The existing tiptop in the bottom of the emergency spillway is disintegrating. <br />This analysis is limited to an evaluation of the emergency spillway, and does not address other aspects of the <br />dam or pond. <br />1.2.1 Location <br />The pond is located approximately 12 miles east of Walden, Jackson County, Colorado, in Section 2, T8N, <br />R78W, bth P.M. It is the northern-most pond of two ponds on the site. <br />1.2.2 Configuration <br />The configuration of Pond I is depicted on (Permit) Figure 2, Post-Mining Soil Erasion Analysis Watershed. <br />This confguratioo was, for this analysis, modified slightly in response to information from a cursory field <br />survey accomplished on 14 October 1994 (Figure Q-1, 10/27/94, attached). <br />Contributing watersheds were determined from Figure 2, as extended onto Exhibit C-2, Geologic Map of <br />Permit Area and Index to Cross Sections, March 5, 1981. <br />The emergenry spillway is located at the northern abutment of the dam, and is depicted on Figure 2, Mining <br />and Reclamation Plan, Mar. 30, 1981. Field measurements taken on 14 October 1994 determined that the <br />current width (bottom) of the emergency spillway was 16.5 feet, the slope of the south embankment was 3.5 <br />• <br />(Canadian Stnp Mine, Pond 1 Riprap Review, 27 Dec 94, Page t of 5) <br />