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J4.0 Analyses of Corrective Measures <br /> <br /> <br />This section is an update of Section H4.0 of the 1999 Addendum. In accordance with the observational <br />approach, the overall stability of the landslide was analyzed accounting for corrective measures made to <br />June of 1999 and geotechnical monitoring to November 2001. The overall landslide stability was <br />reanalyzed using slope stability limit equilibrium models. As indicated in the 1999 Addendum, a single <br />cross section along the greatest extent of historic movement through the main landslide was analyzed. <br />The analyses of corrective measures were based upon aback-calculation of 1997 conditions and the <br />increase in stability with the corrective measures installed in 1998 and early 1999. Geotechnical <br />parameters were taken from Table 1 0. the "1997/98 Landslide Corrective Measures Report". Piezometric <br />levels were updated to 2001 conditions based on well levels observed. This information was used to <br />model the groundwater and the slope stability of the landslide. <br />As a note, the rapid movement of the landslide was arrested using micropiles and the slower long term <br />movement of the landslide is reduced by continued dewatering and drainage of the slide. The slope <br />stability analysis is reevaluated yearly [o account for the change in water levels due [o dewatering and <br />climate and the recent groundwater levels observed. <br />J4.1 Groundwater Analyses <br />See the "1997/98 Landslide Corrective Measures Report" and the 1999 Addendum for a discussion on <br />groundwater analysis. The models that have been established have been updated to reflect the present <br />Spring 2001 groundwater conditions. <br />J4.2 Limit Equilibrium Slope Stability Analyses <br />A limit equilibrium analyses was used to predict the factors of safety under 2001 conditions. Spencer's <br />Procedure of Slices using the computer program SLOPFIW was used because it satisfies all conditions of <br />equilibrium and allows for noncircular failure planes. Figure J2 shows stability under these conditions. <br />Barr Englneering Company <br />PCDOCS1230503/CAK <br />December 15, 2000 <br />Appendlz J <br />2001 Addendum to <br />1997198 Landslide Correetlve Measures Report <br />