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U.S. Standard <br />Sieve Size <br />Percent Passing <br />by Dry Weight <br />2 -inch <br />100 <br />No. 200 <br />15 — 50 <br />• July 12, 2010 <br />• <br />Mr. Timm Corner <br />Manager, Environmental Resources <br />Cripple Creek & Victor Gold Mining Co. <br />P.O. Box 191 <br />100 North Third Street <br />Victor, CO 80860 <br />Re: Proposed SLF Specification Changes <br />Dear Timm: <br />AMEC Earth and Environmental (AMEC) has prepared this letter proposing some modifications <br />to the Soil Liner Fill (SLF) specifications presented in Amendment No. 9. The current physical <br />specification for the SLF is: <br />Soil Liner Fill - processed materials as approved by MANAGER and CERTIFYING <br />ENGINEER, conforming to the following SPECIFICATION: <br />AMEC Earth & Environmental, Inc. <br />304 Inverness Way South, Suite 490 <br />Englewood, Colorado 80112 <br />Tel: (303) 433 -0262 <br />Fax: (303) 433 -0362 <br />Plasticity Index: <br />Hydraulic Conductivity: <br />S: \PROJECTS \1125E CCV CQA \e - correspondence \slf spec letter.doc <br />www.amec.com <br />10 minimum <br />1X10 -6 cm /s maximum <br />ame <br />Recent SLF samples from the current borrow source have had a fines content over 50 percent <br />(the current maximum limit). The SLF samples with fines contents over 50 percent have not <br />shown any observable increasing trend in the Plastic Index (PI), indicating that the fines <br />increase is due to silt not clay particles. In all cases, the SLF samples with fines over 50 percent <br />met the hydraulic conductivity specification. <br />AMEC is proposing increasing the maximum fines limit to 65 percent so that SLF with higher <br />fines can be blended in the stockpile and used for the VLF construction. Increasing the <br />maximum limit on fines will not physically change the performance of the SLF in the VLF as the <br />increased fines are silt not clay particles (e.g. not fat clays). The increased fines content will <br />affect the Maximum Dry Density (MDD) and Optimum Moisture Content (OMC) of the SLF. <br />However, per the current specifications, a Proctor Compaction test is required every 5,000 cubic <br />yards, so any changes in the MDD and OMC will be automatically updated and implemented in <br />the field. <br />