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The increasing ground water levels around the MB-1 Pond are a concern and it is expected that <br />increased ground water levels in this area may contribute to instability. As discussed in the 1~` <br />quarter report it might be beneficial to jet the horizontal drains located in this azea to ensure that <br />they are not clogged and restricting drainage out of the colluvium material that becomes unstable <br />when it is saturated. <br />Old Main Substation: <br />Ground water levels in piezometers measured aoound the Old Main Substation show the nonna] <br />increasing/decreasing seasonal trends. Ground water in I-26P reached the Bound surface during the <br />1~` quarter 2006. Measurements of the ground water level at this location in the subsequent months <br />show a slight decrease (2 ft} in the ground water level. <br />The Bound water levels in W1J are increasing, and during the 2"s quarter 2006, the seasonal <br />increase in ground water levels measured at this location were not followed by the usual decrease. <br />In fact, the standing water levels at this location have increased by approximately 5 ft since this <br />time last yeaz. <br />The ground water level in piezometer I-26P and WIJ will be measured in subsequent months and if <br />a drop is not measured, remedial action may be required as it is Imown that saturated colluvium <br />creates instability in the main landslide slope. In addition, as discussed in the 1~` quarter report it <br />might be beneficial to clean out the horizontal drains located in this azea with a high pressure hose <br />to ensure that they aze not clogged and restricting drainage. <br />F-Seam Portal: <br />' Ground water levels in piezometer PB2 increased by 7 feet during the 1~` half of 2006. This <br />increase is slightly less than the typical (based on historical data) seasonal fluctuations. Other <br />' piezometers in this azea, I-lOP and I-9P, showed the usual seasonal fluctuation is in the Bound <br />water levels. These seasonal fluctuations in the ground water level correlate well with the surface <br />displacement measured at this location, as discussed in Section D. <br />Above the Material Storaee Bench (MSB): <br />During Mazch 2006 a piezometer was installed above the MSB at elevation approximately 6565 to <br />intersect and straddle the F-Coal Seam. The ground water level in this piezometer was measured at <br />a depth of 143 feet (approximately 2 feet above the F-Coa] Seam) immediately after the installation. <br />Recent measurements at this location show the same water level as that measured immediately after <br />installation. This suggests that the F-Coal Seam is continually saturated and may be a source of <br />water that is creating instability on the MSB. <br />An engineering design for a dewatering trench at the MSB that will help alleviate the high ground <br />water Ievels at this Iocation is currently under review by MCC. <br />Bart Engineering Company 2~ Quarter 2006 <br />' O6fZ6-031 Geotechnical Monitoring <br />