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<br />._. _,. <br />r • III IIIIIIIIIIIIIIII <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Depanmenl of Naniral Resources <br />1 113 Sherman 51., Room 215 <br />Denver, Culorado 80207 <br />Phone: 13031 8663567 <br />FAX: (303) 83?-8106 <br />DATE: August 12, 1995 <br />TO: Berhan Keffelew <br />FROM: Jim Pendleton <br />RE: CRESSON <br />Carlton <br />~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />r Roy Romer <br />Governor <br />lames 5. Lnchhead <br />9 - Executive Director <br />hLChaeIB Long <br />Drvia on DireUUr <br />MIInical Spec Revision <br />Tai ngs Lift Thickness Elimination <br />(Permit No: M-SO-244) <br />During our presence at the Cresson mine site on Friday, September <br />8, 1995, John Hardaway presented me with a copy of a supplemental <br />analysis of the Carlton tailings fill. This analysis was prepared <br />by Golder Associates in response to my earlier adequacy comments. <br />I have reviewed Terry Manziac's supplemental submittal. <br />Briefly summarized, Cripple. Creek & Victor Gold (CC&VG) originally <br />requested a revision to increase the relocated Carlton Mill <br />Tailings placement lift thickness specification from a maximum of <br />18 inches to 7 feet. The revision application stated that the <br />structural stability of the relocated Carlton Tailings material is <br />not of importance, because it will be covered with waste rock and <br />be buttressed by the relocated Highway embankment. I responded <br />that the structural character of foundational materials is <br />important for any large earthen structure. In the short term the <br />Carlton Tailings materials will not be buttressed. Further, I also <br />intended to express a longer term concern, noting that a failure of <br />this low strength foundational material beneath the final Arequa <br />Gulch excess overburden fill and adjoining superimposed structure <br />might compromise the hydrology control structures located above the <br />relocated highway embankment. <br />Short Term Scenario <br />John Hardaway had submitted a supplemental response including a <br />reevaluation of the stability of the relocated Carlton Mill <br />Tailings. This stability analysis was limited to my short term <br />concern, in that it evaluated the stability of a zoned relocated <br />Carlton Mill Tailings fill, buttressed by a waste rock embankment. <br />Golder theorizes that conservatively weak properties for the <br />Carlton Mill Tailings are achieved by modeling the fill assuming <br />"p = 0", with an assumed cohesion of 300 psf. This case is <br />