1990-02-01_REVISION - M1988112 (2)

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~ III IIIIIIIIIIIII III ~ 999 STEEPEN ROBERTSON AND KIRSTEN Consulting Engineers and Scientists F E B 1 1990 MINED LAND HECLAMATIG~Pt i3~'+/t~'.-J~nuary 30, 1990 SRK Project #14710 Mined Land Reclamation Division 215 Centennial Building 1313 Sherman Street Denver, Colorado 80203 Attention: Steve Renner RE: STRENGTH TESTING OF EMBANKMENT FILL - SAN LUIS PROJECT Dear Steve; During our discussion on the stability of the proposed embankments at the Battle Mountain Gold's San Luis Project, Jim Pendleton inquired as to actual strength test data on the embankment fill material. Due to the physical characteristics of the embankment fill material being generally a well-graded minus 3 inch sandy gravel, no testing of the material had been performed. The constraint applied by conventional testing equipment limits the maximum size of the material that can be tested. To test the embankment fill, the approach required us to "scalp" the larger material and test the smaller particle sizes only. The effect of this is to produce a result which is typically less than the entire material in cases where, as for San Luis, the larger gravel consists of a relatively competent rock. The attached test report is for the minus 3/8 inch portion of the fill which was tested in a drained, direct shear. The sample was tested in a saturated state at a density considered representative of that which will exist in the embankment. The test result shows a shear strength composed of a friction angle of 36.6 degrees and a cohesion of 15.3 kpa (320 psf). The result confirms that the assumed strength of the fill used in the stability analysis (~ = 35°, c = 0) is conservative and that a higher strength of ~ = 38° c = 200 psf would be more representative of the entire fill material. Steffen Robertson and Kirsten (U.S.), Inc. 3232 South Vance Street, Lakewood, Colorado 80227, U.SA. Tel. (303) 985-7333 Facsimile (303) 985-9947 Other oilices in: U.S.A., Canada, United Kingdom and Africa