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• Most of the tests reviewed did not include correction for oversized <br />particles. The test is limited to particle sizes of less than 3/4 inches. The <br />average value was corrected using estimated gravel and moisture contents <br />according to ASTM D 4718. The corrected average values are maximum dry <br />density of 95 pcf at an optimum moisture content of 11 percent. This value <br />is considered a reasonable estimate for 'typical" coal refuse. <br />In-Situ Moisture and Density. There is considerable density testing <br />information available from this investigation and the previous studies and <br />construction testing. There have been changes in the operation of the <br />processing plant to reduce moisture and changes in placement procedures <br />over the life of the RDA. Another significant factor in our opinion is the <br />• increase in area at the top of the pile. This allows a greater area for <br />spreading the refuse and, with a constant production rate, this results in <br />thinner lifts. It is also easier to operate and "catch up" wkh drying and <br />compaction after rain or snow. <br />The data we reviewed indicate compaction has increased over time. <br />We reviewed moisture density test results from our previous investigation <br />(CTL/T 1991, Reference 5), the compaction testing performed during RDA <br />construction by Lincoln DeVore, Inc. (LD 93/94, Reference 8) and the results <br />of moisture density tests on the samples obtained from the current <br />investigation. Following is a summary of the average percent compaction, <br />moisture content and percent of failing tests for these three sources. <br />• <br />13 <br />