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n <br />U <br />H7.0 Discussion of Long-Term Stability Based on <br />Current Conditions to June 30, 1999 <br /> <br />• <br />This section is an update of Section 7.0 of the "1997/98 Landslide Corrective Measures Report". This <br />section provides new discussions on the long-term stability of the landslide based on information and <br />analysis collected to June 30, 1999. <br />The following discusses the validity of the analyses for long-term conditions, a comparison of movements <br />prior to correction and after correction, and the use of risk analysis to determine long-term stability. <br />H7.1 Validity of Models <br />Validity of Model Geometry. Refer to Section 7.0 of the 1997/98 report for a discussion of this topic. <br />Validity of FLAC Model. Refer to Section 7.0 of the 1997/98 report for a discussion of this topic. <br />Validity of Limit-Equilibrium Analysis. The results of the limit-equilibrium analysis, as shown on <br />Figure H8, H9, and H10 show that the landslide will have a relative factor of safety of above 1.28 with the <br />pins and 1.33 accounting for the 1998-99 dewatering effects. Long-term dewatering through pond lining, <br />stone columns (and horizontal wells), horizontal dewatering trenches, and reclamation activities that do not <br />concentrate water flow, should slowly increase the factor of safety to above the 1998-99 condition. <br />Therefore, the analyses indicate that the overall landslide is stable in the long-term with the existing <br />corrective measures. <br />Barr Engineering Company <br />PCDOC51208220ICAK <br />July 31,1999 <br />22 Appendix H <br />1999 Addentlum to <br />1997198 Landslide Corrective Measures Report <br />