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STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Depanment of Natural Resources ~I~~ <br />1713 Sherman St., Room 215 <br />Denver, Colorario 80203 <br />Phone: (303) 866-3567 <br />FA%. (3071 83_>>-A106 <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />DATE: July 22, 1996 Roy Romer <br />Governor <br />TO: Berhan Keffelew Iames S. LOC hhead <br />A Exec utive Dire<Inr <br />//~ MichaelB Long <br />FROM: Allen Sorenson }'1( Div is inn Direcinr <br />RE: Freeze-Thaw Effects on Soil Liner Hydraulic Conductivity, <br />Cripple Creek and Victor Gold Mininq Company, Cresson Project, <br />Permit No. M-80-244 <br />I have reviewed the information related to soil <br />characterization provided in a letter and <br />and Victor Gold Mining Company (CC&V) <br />information provided by CC&V supports the <br />layer because the test data indicate that <br />liner hydraulic conductivity will occur <br />thawing of the soil liner. <br />liner freeze-thaw <br />attachments from Cripple Creek <br />dated July 15, 1996. The <br />use of a 2 foot drain cover fill <br />no significant increase in soil <br />as a result of freezing and <br />Hydraulic conductivity measurements conducted as a component of the soil <br />liner freeze-thaw characterization yielded some values for hydraulic <br />conductivity on the order of 10-10 cm/sec. These are extraordinarily low <br />hydraulic conductivity values, and would not be anticipated for the clayey <br />gravels that were tested. It is likely that the hydraulic conductivity <br />values from the laboratory testing are not equal to the actual hydraulic <br />conductivity of the soils that are placed in the construction of the leach <br />facility. However, since the hydraulic conductivity values were measured <br />using a rigorous, standard laboratory method approved by ASTM, they are <br />at least correlatable to actual hydraulic conductivity, and are comparable <br />to each other, so the conclusion that freeze-thaw cycling does not <br />significantly affect hydraulic conductivity for these soils is valid. <br />C:\WP51\CRESSON.SB <br />