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December 1986 3 863-2060 <br />• <br />2.0 FIELD INVESTIGATION <br />Field work relating to the stability of Area 9/10 was performed <br />between December 2 and December 8, 198G. This work was performed <br />under the supervision of a Golder Associates' (Golder) geological <br />engineer, and is described in the following paragraphs. <br />2.1 Drilling Program <br />A total of three borings (G-8 through G-10) were drilled in the <br />vicinity of Area 9/10 at the locations indicated on Figure 2. <br />All drilling was performed by Boyles Brothers Drilling Company of <br />Golden, Colorado, using a Longyear 34 drill rig and a combination <br />of drilling techniques. The purpose of this drilling was to <br />determine the geotechnical characteristics of mine spoil and <br />• underlying bedrock units present in the vicinity of borehole <br />locations. Each boring was extended at least 10 feet into rock to <br />determine whether low shear-strength materials are present in <br />critical portions of the foundation. All materials encountered <br />were logged in the field as described in the Record of Borehole <br />logs, Figures 3 through 5. An explanation of borehole log in- <br />formation is presented on Figures 6 and 7. <br />Drilling through mine spoil was performed by advancing 4.5-inch <br />or 3.7-inch OD temporary steel-casing using a wireline- <br />retrieva6le inner tricone bit in conjunction with rotary wash <br />techniques. In addition, the bottom 14 to 18 feet of mine spoil <br />and 10 to 12 feet of underlying bedrock was cored in each boring. <br />This coring was performed using NX and NC face discharge diamond <br />bits and water as the drilling fluid. <br /> <br />Golder Associates <br />