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11 <br />amen <br />January 3, 2010 <br />Mr. Timm Comer <br />Manager, Environmental Resources <br />Cripple Creek & Victor Gold Mining Co. <br />P.O. Box 191 <br />Victor, CO 80860 <br />Re: ADR Water Line <br />Dear Timm: <br />JAN - 7 2010 <br />AMEC Earth and Environmental (AMEC) has prepared this letter for the Cripple Creek & Victor <br />Gold Mining Company (CC&V) presenting a seepage and stability analysis for the proposed <br />ADR water line system, which is to be located along the face of the Phase 5 Pregnant Solution <br />Storage Area (PSSA) embankment. Construction of the ADR water line system will consist of <br />installation of two (2) 10-inch diameter High Density Polyethylene (HDPE) pipes within the <br />PSSA embankment face and installation of a buried power line (to be located above the pipes). <br />AMEC conducted a seepage and stability analysis to assess the potential impact on the Phase <br />5 PSSA embankment stability, should the pipelines break, saturating the embankment fill. It is <br />important to note that should the ADR water pipelines break, it would be immediately noticed at <br />the ADR and the water line shut-down and repaired. <br />Seepage and Stability Analyses <br />The Phase 5 PSSA embankment will be constructed using compacted structural fill placed over <br />a prepared subgrade. The ADR water pipelines are to be incorporated into the face of the <br />embankment fill, buried a nominal 5-feet from the finished surface. Should one or both pipes <br />break, a portion of the structural fill would become saturated, before the water lines can be <br />shutdown and repaired. <br />The seepage analyses were conducted assuming the pipelines break and discharge water for a <br />period of 15 days. This time period was selected to represent a "worst case" scenario, under <br />which a significant section of the structural fill becomes saturated. Under actual conditions, the <br />pipes would not be allowed to leak for more than 30 minutes. With both pipes broken and <br />allowed to discharge water for 30 minutes, only a very small area of embankment fill would <br />become saturated. <br />At the maximum embankment section (most critical for stability), the elevation of the pipelines is <br />approximately 9722 feet, which is 36 feet below the water tank base elevation of approximately <br />9758 feet. Based on these conditions, the water pipelines will have a minimum water pressure <br />head of about 15.6 pounds per square inch (psi). The pipes will be buried approximately 5 feet <br />below the ground surface, the confining pressure (from the embankment fill) can be estimated <br />as 5 feet times the unit weight of fill of 125 pounds per cubic foot (pco, or about 4.3 psi. Since <br />the pipe internal pressure exceeds the confining pressure, water discharge from the broken <br />AMEC h s L arts. <br />36-€ ftvwcem WW S=Ckr6 308e 40 <br />801112 <br />T-ek PM)4334M2 <br />Fa:. 2 <br />MACINTOSH HD:USERS:JLUPO:D000MENTS:CC&V:WATER LINE letler.doe