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February 17, 2004 <br />URS Corporation <br />8181 E. Tufts Avenue <br />Denver, CO 80237 <br />Tel: 303.694.2770 and 303.740.2600 <br />Fax: 303.694.3946 <br />.10 AMS <br />Mr. Ronald J. Valentine, PE <br />Climax Molybdenum Company <br />Climax Mine <br />Highway 91 - Fremont Pass <br />Climax, CO 80429 <br />Subject: Draft St.___rim_a_r_y Construction Reort_,,,Tenmile Decant Structure No. 2 Climax <br />Mine, Climax, Colorado <br />Project No. 68- 00044694.00 -3936 <br />Dear Mr. Valentine: <br />The Climax Molybdenum Company (Climax) has requested that URS Corporation (formerly <br />Woodward -Clyde Consultants) review the existing files, observe the completed construction of a <br />new decant structure at the Climax Mine, and provide documentation that construction was <br />completed in accordance with the design. We have completed our observation of the new Decant <br />Structure No. 2 and prepared this letter documenting construction. Presented below is a brief project <br />background, followed by a description of the construction completed at the site, a discussion of field <br />observations and testing performed during the construction phase and our observations. Attachment <br />A to this letter includes a copy of the Issue for Construction drawings. <br />PROJECT DESCRIPTION <br />The Tenmile tailing impoundment is located near Fremont Pass, Colorado, approximately 20 miles <br />south of Interstate 70 on Colorado Highway 91. The tailing dam was constructed using the upstream <br />method of tailing deposition. Controlled tailing deposition is used to create free - draining sand shell, <br />which impounds finer tailing and excess water. <br />The excess water is collected by decant structure and conveyed to the Tenmile Drainage Tunnel, <br />where it is transferred to the existing water treatment system. Decant Structure 1 is a side hill decant <br />located near the southwest corner of the pond and was in use prior to the new Decant construction. <br />Decant Structure 1 is sloped to conform to the original topography and constructed of partially <br />concrete - encased, 20 -inch diameter, three - quarters round, 316 stainless steel pipe. Wood stop logs <br />are used to manually control water levels. Flow is carried beneath the tailing pond to an 18 -inch <br />vertical drill hole, drill to intersect the Tenmile Tunnel, lined with 12 -inch diameter 316 stainless <br />steel casing, grouted in place. The discharge in the tunnel is unrestricted and unimproved. <br />N: \GENERAL\ADMIN\CNH -ADMIN \CLIMAX- DECANT SUMMARY RPT_REV1.DCC 02/16/04(12:45 PM) <br />