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<br />Golder Associates Inc. <br />44 Union Boulevard, Suite 300 <br />Lakewood, CO USA 80228 <br />Telephone (303) 980-0540 <br />Fax (303) 985-2080 <br />April 19, 2002 <br />Cripple Creek & Victor Gold Mining Company <br />P.O. Box 191 <br />1280 State Highway 67 <br />Victor, Colorado 80860 <br />Attention: Mr. Ron Roberts <br />~~ = Golder <br />~ASSOCl~c'l~eS <br />Our Ref: 003-2203 <br />RE: PHASE IVb AND IVc TEMPORARY DIVERSION CHANNEL SIZING <br />Deaz Ron: <br />Golder Associates Inc. (Golder) has prepazed this letter for Cripple Creek & Victor Gold <br />Mining Company (CC&V) presenting the results of a hydraulic analysis to resize the <br />temporary diversion channel (between Phase IVb and Phase IVc) for the Phase IV Valley <br />Leach Facility (VLF). <br />The hydraulic analysis was conducted to determine the size of the temporary diversion <br />channel to safely pass the run-off from a 25 yeaz, 24 hour storm falling on the subbasins <br />upslope of the Phase IVb VLF. The hydraulic analysis was based on the following <br />assumptions: <br />- 25 yeaz, 24 hour storm event assumed to have an SCS Type II distribution. <br />The 25 year, 24 hour stone event was estimated to be 2.8 inches from <br />NOAA Atlas 2, Volume III; <br />- The Curve Number (CN) for reclaimed slopes and grass covered natural <br />terrain is 71 (per Amendment No. 8); <br />- The CN for tree covered natural terrain is 66 (per Amendment No. 8); <br />- The CN for stripped natural ground was assigned a value of 80; and <br />- Time of concentrations was determined using SCS upland methodology. <br />Detailed HEC-1 calculations for the temporary channel sizing aze attached to this letter. The <br />results of the hydraulic analysis indicate that the temporary channel should be sized to safely <br />pass a peak flow of 61 cubic feet per second (cfs). <br />OFFICES ACROSS ASIA, AUSTRALASIA, EUROPE, NORTH AMERICA, SOUTH AMERICA <br />