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-6- <br />r 1 <br />U <br />and a plasticity index of 18. When compacted using the standard <br />Proctor compaction test (ASTM D 698, AASHTO T-99), the sample had a <br />maximum dry density of 112 pcf and an optimum moisture content of 15 <br />percent. Another sample of the surficial clays was obtained from the <br />auger cuttings at Borings 14, 15, 16, and 17. These borings were sub- <br />sequently renumbered to be Boring Nos. 6 through 9 at the sediment dam- <br />site. This sample was also mostly clay with 89 percent passing the No. <br />200 sieve, a liquid limit of 46 and a plasticity index of 29. The <br />maximum dry density for this sample was 101 pcf and an optimum moisture <br />content of 20.8 percent when compacted using standard Proctor compaction <br />procedures. One sample was obtained from the existing haul roads. This <br />material consisted of a combination of clay with sandstone chips and <br />• some pieces of gravel which we believe to be the result of breakdown of <br />mine spoil. This material is a less plastic soil and better suited for <br />construction of haul roads. The liquid limit was 23, plasticity index <br />was 4 and 55 percent of the material passed the No. 200 sieve. The opti- <br />mum moisture content was 10.3 percent and the maximum dry density was <br />113 pcf for this material when compacted using ASTM D 1557, method 'D' <br />(AASHTO T-180). To evaluate the structural performance characteristics, <br />composite samples were compacted at various moisture and density conditions <br />and CBR tests were performed. The results for CBR tests are shown on <br />Figs. 10 through 13. The sandy clay had a CBR of about 2.3 at 95 per- <br />cent compaction, using the standard Proctor procedure. The sample <br />clay and sandstone from the existing haul roads had a CBR value in excess <br />• of 40 when compacted using the modified Proctor compaction procedure. <br />