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1 `~ <br />' 4. The permeability of various pervious zones within the pile can <br />vary by up to two orders of magnitude. <br />' Considering the apparent subsurface flow mechanisms and the <br />heterogeneous structure of the pile the results of the present <br />t Phase II stability analysis must be viewed acknowledging the fact <br />that piezometric conditions are being measured across only two <br />sections of the pile and those piezometric conditions have <br />indicated the potential of changing on a frequent basis. Given the <br />' variability of piezometric surfaces, material composition, <br />gradation and placement, other areas or sections of the pile may <br />exhibit better and/or worse conditions, with respect to stability, <br />' than were found at the four discrete locations investigated and <br />analyzed herein. Only with these limitations in mind can it be <br />stated that those sections of the refuse pile which have been <br />evaluated meet present safety factor criteria. In an effort ,to <br />' provide some type of confidence in the present stability results it <br />must be noted that a somewhat conservative approach to evaluation, <br />modelling and analysis was taken. The pore pressure systems used <br />' in the models of existing conditions were those which equaled or <br />exceeded all measured values in each zone. The safety factors for <br />the two sections examined exceed the minimum required value of 1.5 <br />' under current conditions. Pore pressures were incrementally <br />increased to establish critical depths for each of the piezometers <br />installed under the present study. Given the considerations stated <br />above there is no reason to believe these two sections of the pile <br />will become distressed as long as piezometer measurements are made <br />at least quarterly and the critical depths presented at the end of <br />this report are not exceeded. Should any of the critical depths be <br />' e:ceeded it is strongly recommended that the issue of stability be <br />revisited based on such known conditions. The following table <br />presents the present piezometer measurements (obtained on April 23, <br />' 1994) and critical depth measurements which should not be exceeded <br />for each of the piezometers installed for the present study: <br />PZ Total Depth Depth Measured Critical Target <br />' ID (ft} on 4-23-94 (ft) Depth (ft) <br />100 14.91 Dry 13.12 <br />' 101 27.67 19.95 18.52 <br />' 102 21.50 19.74 19.03 <br />103 32.19 DRY 28.33 <br />' 104 37.29 36.94 32.10 <br />105 42.13 41.85 32.03 <br />' 106 46.21 DRY 31.96 <br />107 57.55 57.01 53.87 <br />' 31 <br />1 <br />