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'. <br />to near its previous level. With this rapid rise and subsequent <br />drop in PZ 306, the water Ievel measured in piezometer 302 remained <br />' constant while the piezometric levels in piezometers 303, 304 and <br />305 dropped nearly 1-foot then recovered to their previous level in <br />direct response to adjustments in PZ 306. During this period of <br />adjustment the piezometric level measured in PZ 307 (foundation <br />' piezometer) also indicated a slightly increasing trend which <br />continued to the end of the 18-day monitoring period. These <br />adjustments indicate that a connection through or around some type <br />' of boundary condition opened, draining an upper pool (measured by <br />PZs 303, 304 S 305) into an area of the pile which had previously <br />appeared dry (measured by PZ 306). This connection remained in <br />effect for a few days, then closed at which time the previously dry <br />zone drained, perhaps into the foundation material (measured by PZ <br />307). The fact that piezometer 302 was virtually unaffected by t`e <br />adjustments noted above indicates that a secondary boundary likely <br />exists near its tip elevation. Considering this data, a primary <br />boundary at elevation 4855+/- is presumed to exist which is <br />affected by a variable piezometric surface (measured by piezometers <br />303, 304 S 305 and 101 S 102). The data also suggests that the <br />material between the presumed boundary and the foundation contact <br />is at times affected by the upper piezometric surface rather than <br />I constant pore pressures. The initial data from piezometer 306 <br />revealed pressures indicative of a relatively isolated zone or <br />channel acting as a drain. However, the later measurements showed <br />an increase in pressure to as high as the zones above the presumed <br />boundary, suggesting a possible connection developing between the <br />two zones. Such a connection would subject the lower zone to pore <br />pressures generated by the phreatic surface existing above the <br />I boundary. In this instance, the effects of a variable piezometric <br />surface on the material below the boundary represents a more <br />conservative approach to modelling pore pressure. Thus, a variable <br />piezometric surface was used to model pore pressures between the <br />presumed boundary and the foundation contact in the present <br />analysis. Measurement data gathered on March 16, 1994 was used in <br />the present analysis, as it represents the most extreme combinatior. <br />of pore pressures observed during the 18-day monitoring period. <br />Given the heterogeneous nature of the pile it is unlikely the <br />adjustments observed in the 300 series piezometers during the brief <br />daily monitoring period were a one time coincidence. It is <br />however, quite likely that such adjustments take place within the <br />pile on a regular, yet unpredictable basis. The site did receive <br />1 precipitation during the monitoring period, but without the benefit <br />of monitoring piezometers through several cycles of precipitation, <br />no conclusions with respect to precipitation effects can be made at <br />this time. As noted above the data gathered on March 16, 1994 is <br />used in the present analysis and is considered the most critical <br />combination of the variable conditions observed during the short <br />monitoring period. Therefore when considering the results of <br />I stability analyses based oa this data the limitations of modelling <br />a non-steady pore pressure system must be acknowledged. In order <br />to develop a stability model far critical section C-C, the maximum <br />observed pore pressures within the pile and foundation alluvium <br />22 <br />