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• LABORATORY INVESTIGATION <br />Samples obtained from the test pits and holes were examined and classified in the laboratory by the <br />project engineer. Laboratory testing included standazd property tests, such as moisture contents, dry unit <br />weights, grain size analyses and liquid and plastic limits. Direct sheaz tests were conducted on remolded <br />samples of the processed waste coal materials to determine the strength coefficients of these materials in <br />their compacted stale. In addition, unconfined compressive strength tests were conducted on relatively <br />undisturbed samples to correlate the sheaz strength of these materials. Falling head permeability tests <br />were also conducted on samples of the remolded waste coal materials so that the permeability of these <br />materials could be determined. <br />Results of the laboratory testing program aze shown in Figures k6 and N7 and aze summa,;~ed in Table 1. <br />The laboratory testing was conducted in general accordance with applicable ASTM specifications. <br />SUBSURFACE CONDITIONS <br />The subsurface conditions encountered in the test pits and holes were fairly consistent and generally <br />consisted of a 32 to 34 foot thick layer of compacted, processed waste coal materials overlying a thin <br />• layer of natural clays and clays[one bedrock to the maximum depth investigated, 40 feet. <br />Based on the information obtained during [he field and laboratory investigations and our periodic <br />inspections made at the site, it appears that the processed waste coal materials which have been placed in <br />the pile aze variable in classification and consistency. In general, it appears that the processed waste coal <br />materials are sandy to clayey with gravel sized fragments and these materials are typically low to <br />moderately plastic, moist to very moist and gray to black in color. It appears that the majority of the <br />processed waste coal materials consist of sand and gravel sized materials with approximately 65 to 75 <br />percent of the material being retained on the No. 4 and No. 200 sieves and the percentage of fines <br />(percent passing the No. 200 sieve) ranges from 25 to 35 percent. However, we did encounter several <br />layers of processed waste coal which had a larger amount of fines. These materials had 50 to 55 percent <br />of the samples passing through the No. 200 sieve. [t should also be noted that the moisture content of <br />these materials was generally higher. The laboratory test results obtained from the waste coal materials <br />aze summarized in Table 1. <br />Based on the nucleaz density tests taken in the test pits and the results of the moisture density tests <br />conducted on the undisturbed samples obtained from [he [es[ holes, it appears that the compaction of the <br />waste coal materials ranges from 9l [0 99 percent of the maximum standazd Proctor density determined <br />• in accordance with ASTM D698. In addition, the moisture content of the fill materials ranged from 2 <br />percent below the optimum moisture content to 5 percent over the optimum moisture content. It should <br />lob No. 97-3216 Nonhwest Colorado Consultants. Inc. Page 4 <br />