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• • iii iiiiiiiiniu iii <br />999 <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Depanmenl of Natural Resources <br />171 J Sherman 51.. Room 215 <br />Denver, Colorado 80207 <br />Phonc OO11866~3567 <br />FAX: 13031 872-8106 <br />DATE: June 22, 1994 <br />TO: Berhan Keffelew <br />FROM: Allen Sorenson ~'~ <br />./~ <br />, ~~ <br />RE: Durability and Slake Testing of Granitic <br />Leach Pad Footprint, Cripple Creek and <br />Cresson Project, File No. M-80-244 <br />II~~~ <br />DEPARTMENT OI <br />NATURAL <br />RESOURCE` <br />Ray Romer <br />Governor <br />lames 5. Luchhead <br />E+tec ulrve Direanr <br />Michael B. Long; <br />Dm¢iun Dueaw <br />Rock in the <br />Victor Gold, <br />I have reviewed the physical testing results submitted for the <br />material proposed to be used for construction of the leach pad <br />underdrain. This testing demonstrates that the granite proposed <br />for use is comprised of a non-slaking type material, however the <br />durability of this material is questionable based on the results of <br />testing in the Los Angeles Abrasion Machine. This testing resulted <br />in 47.7 percent loss in weight from the sample. The Division will <br />not accept underdrain materials that lose more than 40 percent by <br />weight during the L.A. test. The operator believes that the sample <br />that was tested had been subjected to near surface weathering, and <br />would not be representative of the durability of the granites that <br />will be blasted from the leach pad footprint to obtain materials <br />for underdrain construction. If the operator is confident of this <br />assumption, the Division can approve generation of representative <br />underdrain rock in the footprint through blasting and excavation, <br />with the stipulation that a minimum of three samples be subjected <br />to the L.A. abrasion test, and the understanding that samples <br />losing more than 40 percent by weight during the testing would <br />represent material that is unsuitable for underdrain construction. <br />I did not review the results of chemical testing on the granitic <br />material proposed for use as underdrain fill. Obviously, all <br />underdrain fill will have to meet the gradation as approved in the <br />specifications. <br />cc: Jim Pendleton <br />Carl Mount <br />C:\WP51\CRESSON6 <br />