2010-12-17_REVISION - C1981019 (94)

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SHANNON 6ML.SON, INC. have adapted several figures from the reports. Colowyo has constructed two large excess spoil fills, the Streeter Fill and the West Pit fill. Based on our experience at the site and discussions with Colowyo, both fills have performed well. 4.0 FIELD EXPLORATION AND LABORATORY TESTING We drilled four borings designated C -101 through C -104, at the locations shown on Figure 2 to evaluate the subsurface conditions. The coordinates and elevations of the borings were surveyed by Colowyo. The borings were drilled by Ager Drilling Service, Inc. (Yampa, Colorado) under subcontract to S &W. The borings were drilled using a 4- inch - diameter solid -flight auger or 8 -inch hollow stem auger powered by a track - mounted drill rig. The borings were advanced to depths of about 15 to 49 feet. Disturbed samples were obtained using a modified California (MC) barrel sampler at 5 -foot and 10 -foot intervals. The MC test procedure consists of driving a 2 1 /2 -inch outside diameter sampler (lined with 2- inch - diameter brass tubing) a distance of 12 inches beneath the bottom of the borehole with a 140 pound hammer falling a distance of 30 inches. The number of blows is recorded for the two 6 inch increments of penetration. If high penetration resistance prevented driving the total length of the sampler, the blow count and the partial penetration depth were recorded. The sum of the blow counts for the two 6 -inch increments, or the partial penetration blow count, is termed the penetration resistance. The penetration resistance values provide a means for estimating the relative density or compactness of cohesionless (granular) soils and consistency or stiffness of cohesive (fine - grained) soils. The penetration resistance values are shown in the individual boring logs in Appendix A. Published correlations exist between penetration resistance and relative density or consistency/ stiffness based on the Standard Penetration Test (SPT). The MC test method is similar to the SPT (ASTM International Designation: D 1586), except a larger diameter barrel sampler is used, and it is only driven 12 inches. As a result of the larger diameter sampler, the raw blow count numbers for the MC are typically slightly higher than the penetration resistance, or N- value, from the SPT. However, because the difference is generally small, we used the raw MC blow counts to classify the relative density and consistency /stiffness. The borings were observed by a geologist from S &W who collected soil/rock samples and prepared field logs of the borings. All samples from the MC sampler were taken to our laboratory. Visual classification of the samples was based on the classification systems shown in 23 -1- 01101- 400 -R l .docx/wp /Ikn 23-1-01101-400 3 Exh. 23 -1 -10 Revision Date: 08/05/09 Revision No.: PR -03