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J <br /> <br />• <br />the movement/deformation was observed and the number of days after the installation of the wells that the movement <br />was recorded are shown on the Logs of Exploratory Test Holes (Figures #2 and 43). <br />Conclusions and Recommendations: Based on the results of our measurements and observations made over the last <br />year at the project site and the bedrock and groundwater information obtained from the test holes and test trench/pit <br />excavated along the eastern edge of the slide area, it is our belief that the subject slope failure is occurring in the natural <br />clays and weathered claystone materials that are underlying the fill materials previously placed at the project site <br />during the reclamation of the haul road that previously traversed across the slope in which the failure is located. It also <br />appears that a considerable amount of groundwater is flowing within these overburden soils and highly weathered <br />bedrock materials. <br />Based on the bedrock and groundwater surface maps that have been developed with the information obtained from the <br />test holes/wells and our observations of the bedrock and groundwater conditions encountered in Test Trench/Pit #1, it <br />appears that the groundwater, which we believe is a major contributor to the slope failure, is flowing in a south to <br />southwest direction. It also appears that a moderate dip/anomaly in the bedrock surface is occurring in the vicinity of <br />TH-7. The dip/change in depth may be related to a fault in the bedrock. It also appears that considerably more <br />groundwater flow is occurring in this area. <br />underdmin/cutoff trench be <br />the failure area, the amount <br />of regrading and buttress construction required at the lower portion of the slide can be substantially reduced. <br />Based on the information obtained from Test Trench/Pit 1, which was excavated along the east side of the failure area, <br />we strongly recommend that two additional test trench/pits be constructed at the site at the approximate locations <br />shown in Figure #6 to provide additional information on a depth and condition of the bedrock materials and <br />undwater flows. We recommend that the base o e trenches be excavated at least 2 feet into the competent <br />bedrock materials or until practical rig refusal is encountered. The test trench/pits should daylight into Pond 12. We <br />also recommend that the southern half of Test Trench/Pit #1 be extended down into the bedrock materials so that the <br />groundwater flows in this area can be evaluated and the groundwater flows can be diverted into Pond 12 as well. We <br />also recommend that the groundwater levels in the test holes/wells be monitored as the trench/pits are constructed and <br />for at le tional months. <br />We believe that the information obtained from test trench/pits will allnw us to design a cost effective underdmin/cutoff <br />trench that should adequately dewater the slide area. In addition, we believe that the test trench/pits can be incorporated <br />into the final underdmin/cutoff trench design. As stated in our original report, we recommend that the drain system <br />consist of a 6-inch diameter perforated PVC pipe that is surrounded with free draining gravels. The actual location and <br />trench/pits is obtained. <br />trench will be determined after the bedrock and groundwater t? tion from the <br />We recently obtained a sample of the proposed drainage rock from the Peabody Energy Pit that is situated <br />approximately 7 miles north of the subject site. A gradation/sieve analysis was completed on a sample of the pit run <br />materials being mined from the site. The gradation/sieve test results are shown in Figure #10. We believe that gravels <br />Job Number. 07-7600 NWCC, Inc. Pagc 3 <br />we believe that it is imperative that an <br />and east sides of the failure to intercept and divert the water <br /> <br />Based on the groundwater and bedrock conditions observed to this date,