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• fill materials in TH-9 and the clays extended to a depth of approximately 38 feet beneath the existing ground surface. <br />Highly weathered claystone materials were encountered below the clays in TH-9 and below the fill materials in TH-10 <br />at a depth of 20 feet beneath the existing ground surface. Competent claystone-shale bedrock was encountered below <br />the highly weathered claystone materials at a depth of 44 feet beneath the existing ground surface in TH-9 and 30 feet <br />beneath the existing ground surface in TH-10. Based on the depth to bedrock in these two test holes and the previously <br />drilled test holes, an interpreted Bedrock Surface Contour Map was prepared and is shown in Figure V. Based on our <br />observations recently made of Test Trench/Pit 1, it appears that a considerable amount of weathered bedrock materials <br />are situated over the competent claystone-shale bedrock materials. The weathered claystone materials were <br />encountered near the ground surface at the north end of the trench and competent claystone-shale bedrock was <br />encountered at depths ranging from 15 to 20 feet beneath the existing ground surface at this end of the trench. It should <br />be noted that practical rig refusal with the trackhoe was encountered in the bedrock materials in the northern end of the <br />trench. Bedrock materials were not encountered in the southern half of the trench. <br />Groundwater seepage was encountered in TH-9 at a depth of 22 feet beneath the existing ground surface and in the <br />natural clays at the time of drilling. It should be noted that groundwater seepage was not encountered in TH-10 at the <br />time of drilling. Groundwater seepage was not encountered in the weathered bedrock materials or overburden soils <br />exposed in the northern end of Test Trench/Pit 1. However, a considerable amount of groundwater seepage was <br />observed flowing from the west side of the trench at the approximate mid-point of the trench. The trench was <br />daylighted to the south-southwest and into the existing drainage channel situated south of the slide area. <br />To evaluate the groundwater levels and underlying ground movement, NWCC visited the site a number of times over <br />the past year to measure and record the groundwater levels in the monitor wells, as well as to evaluate the ground <br />?• movement in the test hole locations. The groundwater levels measured in the test holes/monitor wells, as well as the <br />number of days after drilling that the measurement was taken are shown on the Logs of the Exploratory Test Holes <br />(Figures 92 and #3). Based on our measurements taken over the last year, it appears that the groundwater was <br />encountered in the majority of the test holes within the natural clays or weathered bedrock materials and at depths <br />ranging from 6 to 37 '/2 feet beneath the ground surface at the time of drilling. It should be noted that the only test hole <br />in which groundwater was not encountered at the time of drilling was TH-10, which is located to the east-northeast of <br />the other test holes/wells and outside of the slide area. The groundwater levels rose considerably over time in all of the <br />wells. Based on our most recent measurements, it appears that the groundwater levels in a majority of the wells have <br />stabilized and are situated within 10 feet of the existing ground surface. It should also be poted that groundwater <br />continued to flow from the top of the PVC casing in TH-3, which is situated approximately 2 % feet above the existing <br />ground surface. Potentiometric Groundwater Surface maps have been prepared based on the groundwater levels <br />measured at the time of drilling and at the groundwater levels measured on May 28, 2009. These maps are provided in <br />Figures 08 and #9. <br />As noted above, our firm also measured and observed the PVC casing to determine if any soil movement had occurred <br />within the PVC casing that was installed in the test holes. Soil movement or deflection of the PVC casing had not been <br />observed in any of the test holes/wells last year; however, four of the monitoring wells (TH-1, TH-3, TH-6 and TH-7) <br />did exhibit ground movement/deflection when measured earlier this year. The deformation was observed in the natural <br />clays or weathered bedrock materials in three of the four wells and in the fill materials in the fourth well. The depth at <br />which the movement was observed ranged from 16 to 27 feet beneath the existing ground surface. The depths at which <br />• Job Number. 07-7600 NWCC, Inc. Page 2