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<br />a <br />' ~ ~ December 1986 4 863-2052 <br />2.0 FIELD INVESTIGATION <br />Confirmatory field work relating to stability of excess spoil <br />materials in the proposed Little Middle Creek tract operation was <br />performed between October 1 and October 10, 1986. Such work was <br />performed under the supervision of a Golder geological engineer, <br />and is described in the following paragraphs. <br />2.1 Drilling Program <br />A total of five borings were drilled in the vicinity of the <br />excess spoil placement areas at the locations indicated on Figure <br />2. All drilling was performed by Boyles Brothers Drilling <br />Company (Golden, Colorado) using a Mobile B-57 drill rig and a <br />combination of drilling techniques. The purpose of this drilling <br />was to determine the geotechnical characteristics of soil, rock, <br />and mine spoil present in the vicinity of the borehole locations. <br />Borings B-2 and B-3 were drilled on steep valley slopes, since <br />slope stability is critical in such areas. Each boring was <br />extended at least 20 feet into rock to determine whether low <br />shear-strength materials are present in critical portions of the <br />foundation. All materials encountered were logged in the field <br />in accordance with the Unified Soil Classification System (Figure <br />4). <br />Hollow-stem augers (7.25-inch OD, 3.25-inch ID) were used to <br />drill through the colluvium encountered in B-1, B-3, and B-5. As <br />shown on the boring logs (Figures 5 through 9), continuous <br />2.5-inch diameter core was obtained in connection with such <br />augering. Upon encountering auger refusal materials, borings B-1 <br />and B-3 were advanced by NX coring (1.9-inch diameter core) using <br />a face discharge diamond bit and water as the drilling fluid. <br />Intact rock encountered in B-5 was weathered to a degree such <br />Golder Associates <br />