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SHANNON F~WILSON, INC. <br />• <br />4.0 FIELD EXPLORATION AND LABORATORY TESTING <br />As discussed above, we have considerable knowledge of the soil conditions in this area (Figure <br />3). For this project, we completed two borings, designated ST-1 and ST-2, to evaluate the <br />subsurface soil, rock, and groundwater conditions at the project site. The conditions encountered <br />in the two borings at this site were consistent with our previous experience. As such, for the <br />purpose of our analyses, we assumed that similar conditions exist in the valley below the planned <br />east fill. <br />The locations of the two borings are shown on the Site and Exploration Plan (Figure 2), and the <br />locations of previous studies are shown on Figure 3. The locations and elevations of the new <br />borings were determined using ahand-held GPS unit and should be considered accurate only to <br />the degree implied by the method used. The locations of the previous study areas were <br />approximated from the reports. <br />The two borings were drilled by Custom Drilling Services, Inc. under subcontract to S&W. The <br />borings were drilled using a 4-inch-diameter solid-flight auger powered by a trnck-mounted drill <br />rig. The borings were advanced to depths of about 35 feet. <br />• Disturbed samples were obtained using a modified California barrel sampler (MC) at 5-foot and <br />10-foot depth intervals. The MC test procedure consists of driving a 2 %x-inch outside diameter <br />sampler (lined with 2-inch diameter brass tubing) a distance of 12 inches beneath the bottom of <br />the borehole with a 140-pound hammer falling a distance of 30 inches. The number of blows is <br />recorded for the two 6-inch increments of penetration. If high penetration resistance prevented <br />driving the total length of the sampler, the blow-count and the partial penetration depth were <br />recorded. The sum of the blow-counts for the two 6-inch increments, or the partial penetration <br />blow-count, is termed the penetration resistance. The penetration resistance values provide a <br />means for estimating the relative density or compactness of cohesionless (granular) soils and <br />consistency or stiffness of cohesive (fine-grained) soils. The penetration resistance values are <br />shown in the individual boring logs in Appendix A. <br />Published correlations exist between penetration resistance and relative density or consistency/ <br />stiffness based on the Standard Penetration Test (SPT). The MC test method is similar to the <br />SPT (ASTM Designation D 1586), except a larger diameter barrel sampler is used, and it is only <br />driven 12 inches. As a result of the larger diameter sampler, the raw blow-count numbers for the <br />MC are typically slightly higher than the penetration resistance, or N-value, from the SPT. <br />~J <br />23-1-01105-200-Rl.doc 23-1-0 1 1 05-200 <br />