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Pitch Reclamation Project -Sediment Control Embankment November, 2002 <br />The crest of the embankment was intact and showed no signs of distress. <br />Data Review <br />Data from the piezometers and embankment design cross-sections were reviewed in the <br />Homestake office in Sargents, Colorado. Also, the 2999 annual report, a typical construction log for <br />the piezometers and files on the design of the embankment and construction logs were available for <br />review. From the documents, it was found that: <br />The piezometers aze open stand pipes with no plug to isolate the piezometer screen. Therefore, <br />the measured water levels represent the phreatic surface of the water at that location. <br />2. The water level recorded in piezometer P-3 was higher than the level recorded in piezometers <br />P-1, P-2, and P-4. <br />3. The water level in piezometer P-3 rose to the current level in 1998. An increase in the water <br />level in this piezometer was recorded as eazly as 1994. <br />Discussion <br />Based on the observations and review of data it was concluded that the wet area across the left <br />portion of the embankment face resulted from a potential preferential seepage pathway through the core <br />of the embankment. The wetted area presented itself as a potential problem that should be <br />characterized and corrected for the embankment to operate safely with the pond at full capacity. In <br />addition, it was concluded that the potential existed for a slope failure in the wetted area, the extent of <br />which could not be quantified based on the available data. <br />The development of the preferential seepage pathway through the embankment was reasoned <br />to be a result of several possible conditions, including a) a change in the construction material placed in <br />the core of the embankment over a limited area, b) unsuitable material not noticed in construction or not <br />completely removed, c) poorly compacted material resulting in a localized, relatively more permeable <br />zone, d) inadequate scarifying of a smooth surface prior to placement of the next lift of material ore) a <br />combination of these. Data in the construction records indicated the possibility of unsuitable material <br />being in the core, but the information was inconclusive. <br />The Homestake Mining Company -6- The Glasgow Engineering Group, /nc. <br />