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• • III IIIIIIIIIIIII III <br />999 <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />U 13 Sherman St., Room 215 + <br /> <br />Denver, Colorado 80?03 ~ <br /> <br />Phone: (3071 866-7567 I <br />I <br />FAX: X3031 B32 8106 <br /> DEPARTMENT OF <br /> NATURAL <br /> RESOURCES <br />DATE: April 12, 1994 Ruy ROmer <br /> Governor <br />T0: John Hardaway Ken Salazar <br />Exec ulitt' DuPClor <br />FROM: Allen Sorenson ~/l//+/~]' ~ M~chacl 8. Lung <br />• Division Director <br />RE: Demonstration of Geochemical Suitability of Underdrain <br />Fill, Cresson Project, File No. M-80-244: AM-006 <br />In response to your question regarding the proposed stipulation to <br />amendment 6 approval, the following methodology is provided as a <br />mechanism for Division's acceptance of Arequa Gulch underdrain <br />fill. <br />Three random composite samples of the underdrain fill are to be <br />subjected to Meteoric Water Mobility Testing. There are to be two <br />samples from underdrain fill below the Highway 67 relocation, and <br />one sample from above the Highway 67 relocation. The sampling <br />methods should be sufficiently documented in field notes to assure <br />that the samples are representative. <br />The leachate from the tests must, on average, meet the Cripple <br />Creek stream standards for Al(sol), As, Be, Cd, Cr III, Cr IV, Cu, <br />Fe, Pb, Mn, Hg, Ni, Se, Ag, and Zn where sot denotes the soluble or <br />dissolved form of the metal. The leachate must also fall within <br />the pH range of the Cripple Creek stream standard. <br />If this testing demonstrates that effluent from the proposed <br />underdrain fill will meet receiving stream standards, the Division <br />will accept and permit the material. Durability of the proposed <br />underdrain fill has already been demonstrated via LA Abrasion <br />Testing, and the specifications for gradation are sufficient to <br />assure that the underdrain will be free-draining. If the leachate <br />from the tests does not meet receiving stream standards, increased <br />testing frequency or selection of a different material source would <br />be indicated. <br />cc: Berhan Keffelew <br />Harry Posey <br />Carl Mount <br />C:\WP51\CRESSON3 <br />