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H6.0 Discussion of Stability for Existing Conditions <br /> <br />• <br />This section is an update of Section 6.0 of the "1997/98 Landslide Corrective Measures Report". This <br />section provides new discussions on the existing stability of the landslide based on information and <br />analysis collected to June 30, 1999. <br />Based upon the analyses and the monitoring information, the existing landslide is stable from catastrophic <br />movement. Figure H8 shows slope stability in 1997 with a factor of safety of 1.04, indicating a near <br />catastrophic failure. Figure H9 shows slope stability in 1998 with a factor of safety of 1.28 after the pins <br />installed, indicating a stabilized condition. Figure H 10 shows slope stability in 1999 with a factor of safety <br />of 1.33, after installation of horizontal trenches and other dewatering activities, and reductions in <br />groundwater table, indicating even more improvement in slope stability. <br />FLAC analysis presented in the 1997/98 report indicates that micro piles will undergo 1.8 feet of <br />additional deformation before the shear strength is fully mobilized. This assumes that the strength of the <br />soil mass is constant. It is likely that the soil mass will gain strength as it is dewatered and dries. Through <br />1998 and 1999, the inclinometers have measured 1 inch of movement, well within this limit. <br />Barr Enpineerinp Company <br />PCDOCS120a220/CAK <br />July 37, 1999 <br />27 Appendix H <br />1999 Addendum to <br />1997199 Landslide Corrective Measures Report <br />