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1 1 1 1 1 stability analysis previously described indicates that, if significantly higher pore pressures exist in isolated locations, the safety factor could drop below acceptable limits. The higher phreatic surface stability analysis still cannot necessarily be considered the worst case conditions. Even though, it is difficult to conceive of higher pore pressures occurring in the vicinity of piezometer P-1, there may be other areas where higher pore pressures occur which are not accounted for in the analysis. Because there are remaining questions, we do not believe the issue of stability can be completely resolved based on the existing information. We suggest that, as a minimum, the following three items be addressed as described below: 1.) As was previously mentioned, the strength of the alluvial foundation material used in the analysis is based on assumed values. Since the foundation strength has a significant impact on pile stability, we recommend that the values be confirmed with a program of sampling and laboratory testing to determine both general soil characteristics and specific strength values. Samples for testing could be taken from proposed piezometer drill holes extending into the foundation in the area of wells P-1 and P-2. 2.) Even though we suspect that the existing wells are neither sealed nor significantly influenced by surface runoff, it would be relatively easy to confirm this by bailing the wells dry and observing their rate of recovery. 3.) The limitation of the current open-well type piezometers is that, in a heterogeneous material, as this pile appears to be, they are incapable of providing information concerning pore pressures at specific depths. In fact, in a horizontally zoned system, the water levels may not reflect pressures at any specific depth but rather present a composite of several water bearing zones. We suggest that additional piezometers be installed which are hydraulically isolated at specific depths. This is done by slotting the piezometer tube along a limited interval, providing a sand pack around the slots and sealing that interval of hole with a bentonite seal. Small diameter piezometer tubes should be used to allow piezometer tips to be placed at 3 or depths in a single drill hole. Plate 13 of the Appendix shows a typical multi-tipped piezometer installation. The holes should be continuously sampled and logged to identify any apparent water bearing zones as well as any low permeability layers. It is difficult to determine the number and location of piezometers until the work is started. The results of initial piezometer installations will determine subsequent locations and configurations. 18