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Data Review <br />A. Piezometers <br />Main Mine Site Piezometers <br />MB-1 Pond: <br />A gradual increase in the ground water levels at piezometer B4, located northwest of IvIB-1 Pond <br />was recorded during the 1~` quarter, 2006. Since then, during the 2nd quarter, a slight drop in the <br />ground water level (1 ft) has been recorded at this location. <br />Recent readings of other piezometers in this area (2"d quarter 2006), and in particular piezometer <br />B2, show elevated ground water levels that are not dissipating after the spring thaw. A gradual <br />increase in the ground water table level, at approximately 2-3 ft each yeaz is being recorded at this <br />location. <br />In addition, ground water levels measwed at 98-O1B have also increased beyond their normal <br />seasonal fluctuation and do not show signs of receding. Recent data (since 2004) shows the ground <br />water levels at this location have increased steady to within approximately 16.5 ft below the ground <br />surface. During the Z"d quarter, 2006, this level has increased to 15 ft below the ground surface and <br />is not showing signs of decreasing. This is a concern that the ground water level has not dropped <br />since the spring thaw. <br />Piezometers 98-04A and 98-04B aze also showing an increase in the meastrded ground water level <br />by approximately 3 feet since this time last yeaz. Ground water levels at this location aze currently <br />within 12 feet of the ground surface and may impact the stability of the colluvium material once it <br />becomes saturated. <br />SCP-13 is also showing elevated ground water levels during the 2°d quarter 2006. The existing <br />ground water levels measured aze the highest recorded at this location since installation. <br />Ground water levels measwed in SC-15, located to the SW of the IvIB-1 Pond increased <br />significantly during the 1~` quarter 2006 (by 50 feet). This was the highest ground water elevation <br />measwed since its installation in 1998. Since then, during the 2"' quarter 2006, the ground water <br />]eve] at this location has decreased by 40 feet to 70 feet below the ground surface. This elevation is <br />still above the historical values and is cause for concern. <br />The pumping of stone columns immediately behind the IvIB-1 Pond have helped to alleviate some <br />of the high ground water levels measured (as discussed in Section D), however it seems that do not _ <br />have a widespread impact on the ground water levels measwed in surrounding piezometers. The <br />increased ground water levels azound the IvIB-1 pond correlate with increased surface displacement <br />measwed by surface mirrors and discussed in Section B. <br />Barr Engineering Company 2n° Quarter 2006 <br />0626-031 Geotechnical Monitoring <br />