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1 <br />1 <br /> <br /> <br /> <br /> <br /> <br />1 <br /> <br /> <br /> <br />L_I <br />1 <br /> <br /> <br />1 <br />1 <br />1 <br />It would be beneficial if the sources of the subsurface <br />moisture could be more accurately identified. Considering only, <br />the available data, the moisture sources which seem to affect the <br />southern portion of the pile appear to be steady state, falling <br />gradient conditions. It is conceivable that a significant and <br />somewhat constant amount of moisture enters the pile along the <br />alignment of the southern toe or groin ditch, then gradually <br />drains, towards both, the toe of the slope and underdrain No.2. On <br />the other hand, based on the variable conditions found in the <br />remainder of the pile, it is also possible that what appears to be <br />a uniform ground water flow regime with its primary source either <br />on the pile perimeter or off the pile, is actually a more intricate <br />system with several sources. This suspected system is not apparent <br />because of the type and location of the wells. Even though there <br />is strong evidence to suggest that the pore pressures cannot be <br />accurately represented by a single phreatic surface, for lack of <br />discrete pore pressure measurements, the stability models used in <br />this analysis included single phreatic lines for the determination <br />of pore pressures. Two critical stability sections were selected <br />from the southern portion of the pile, which consider the single <br />piezometric line conditions noted above. The first section <br />(designated as Section A-A on Plate 1 in the appendix) is taken <br />through piezometers R-1, B2-4, B1-1 and BO-1. The piezometric <br />surface modelled for the first section corresponds to piezometer <br />data collected on January 14, 1994 and is presented on Plate 9 of <br />the Appendix. The second section is taken through Piezometers <br />B2-1, P-la and BO-1 (designated as Section B-B on Plate 1). Again, <br />the piezometric surface is modelled from data collected on January <br />14, 1994 and is presented on Plate 10 in the appendix. <br />The piezometric condition which affects the center portion of <br />the pile, is more complex and is not completely or well defined by <br />the available data. The water level measurements present two <br />difficulties relative to understanding subsurface flow conditions <br />in this area. Those being, the fact that companion wells near each <br />other show strikingly different levels, and that all wells in the <br />vicinity of P-1 exhibit water levels well in excess of what would <br />be expected based on the other wells. Several possible <br />explanations have been considered to account for these <br />observations: <br />1.) Since the wells do not include a surface seal, it is <br />possible that surface runoff could get inside the hole <br />and influence water levels. However, if that was the <br />case, the water levels would be expected to fluctuate <br />wildly, somewhat concurrently with climatic conditions. <br />Such a pattern was not observed and it does not appear <br />that surface runoff could be having a significant effect. <br />2.) If the wells had somehow become sealed during <br />installation, trapping water in the holes, the <br />unexpectedly high water levels in some of the wells could <br />13 <br />1 <br />