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1MR-17-98 15:11 From:CCtV GOLD 1N• 1X96693254 • T-317 P 05/10 Job-647 <br />Based on the observations of joint seu in highwalls and [he Call and Nicholas tests and the <br />CC&V crushed ore test, and increased slightly to account for the inherent increase in friction <br />angle for the intitu rock, it is conclui~hat the effective stress friction angle for fractures in <br />the Cresson Mlne highwalls is, for cu Computation purposes, 40°. <br />Material Strength <br />The intact strength of the rock materials in the Mine highwalls was also evaluated by Call and <br />Nicholas (see Enclosure 14 of Volume VIII of CC&V's Permit Amendment Application - <br />~ prepared by Call & Nicholas, Inc. in report dated 23 February 1994). The results of the <br />analyses were: <br />Porphyritic phonolite (3 tesu) Intact rock strength = 11,000 psi <br />Volcanic breccia (3 tesu} Intact rock strength = 10,100 psi <br />Inspection of the rock mass on the Mine highwalls confirms that the pit walls aze predominantly <br />comprised of these geologic materials. There is no evidence of lazge zones of significantly <br />weaker rock materials in the Mine highwalls. <br />Grvund-water pressure <br />In addition to the slope inspection program, CC&V observes the ground-water conditions of the <br />Mine highwalls. This program consisu of the following elements. The results are cited after <br />the description of the element. <br />1. Blast hole inspection. CC&V inspects each blast hole after drilling for standing <br />water. To date, no sanding ground water has been observed in blast drill holes, ocher <br />than that associated with an occasional perched aquifer, which in all cases, has been <br />i minor in extent and water storage. <br />2. Mine highwall seepage inspection. As noted above, CC&V inspects all Mine <br />highwalls routinely for geology, structure, and condition. With the exception of some <br />minor snowmelt seepage issuing from surficial alluvial materials where they have been <br />intersected, no persistent or potentially harmful seepage to the Mine highwall faces has <br />been identified. <br />3. Exploration drill hole program. A relatively large number of holes had been drilled <br />into the rock which ultimately forms the highwalls. These holes aze usually reverse <br />circulation holes using air. Seldom is water encountered. and in all cases the water has <br />bean found in perched strata saturated in areas limited exten[. No water has been <br />produced by this drilling. Mine highwall exposures in these areas confirm the lack of <br />water. <br />4 <br /> <br />