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• previous RDA is shown on Fig. 1. In the previous study we investigated subsurface <br />soil and groundwater conditions, evaluated strength properties for the various soils <br />types and performed parametric stabilfty analyses. The slope face angles and bench <br />configuration of the revised RDA are the same as the previous RDA. We believe the <br />previous investigation provides sufficient subsurface information and laboratory <br />testing for design of the revised RDA. <br />FIELD AND LABORATORY INVESTIGATIONS <br />The field investigation included site visks, test hole drilling and exploratory <br />test pit excavation. A total of 7 borings to depths of 15 to 35 feet, and 6 test pits to <br />depths of 3 to 17 feet were performed during May of 1992. Eight borings or test pits <br />• were located in or near the revised RDA and in our opinion provide sufficient <br />subsurface information and laboratory data for the design of the revised RDA. <br />Field Investigation <br />The test holes were drilled using 4-inch diameter solid-stem auger powered <br />by struck-mounted drill rig. The augers were removed at 5 to 10-foot intervals, and <br />samples were obtained with a standard split spoon (2.0-inch O.D.) or California-type <br />(2.5-inch O.D.) drive sampler. The location of the exploratory borings and test pits <br />are shown on Fig. 1. Graphic logs of the borings and pits are presented in Appendix <br />A. <br />A representative sample of the unprocessed coal waste was obtained from <br />the existing temporary stockpile. A processed coal waste sample was obtained <br />f from Commercial Testing and Engineering Company (CT&E). Based upon <br />discussions with Mr. Mike Placha of Twentymile Coal Company, the processed coal <br />3 <br />1 <br />