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• • `.J movement is likely. (2) slow movement, factor of safety between 1.0 and 1.2, failure is incipient, tension cracks form, and (3) very slow movement, a factor of safety between 1.2 and 1.5, commonly used for temporary structures. (4) extremely slow movement, a factor of safety greater than 1.5, commonly used for permanent structures. 1997 Probabilities. A graph of shear strength verses factor of safety was prepared (Figure HS-8). A soil shear strength of 12.1° corresponded to a factor of safety of 1.0. Assuming a normal distribution and a coefficient of variation of 30%, the values were normalized, the area each condition occupied under the normal distribution curve was computed, and probabilities were calculated for each expected outcome. Calculations are provided in Appendix H5, demonstrating the procedure. Probabilities of outcomes based on the 1997 condition are summarized in Table H2, column 3. 1998 Probabilities. Probabilities were revised based upon the construction of the pins and the 1997 groundwater conditions. A graph of shear strength verses factor of safety was prepared (Figure HS-10). The 1998 soil shear strength of 12.1° corresponded to a factor of safety of 1.25. The mean shear strength was once again the value determined from the 1997 analysis, 12.1°, and the coefficient of variation was again assumed to be 30%. The revised strength values were normalized and the areas these values occupied under the normal distribution curves were computed. These areas correspond with the probabilities assigned to each outcome. Probabilities of outcomes based on the 1998 condition are summarized in Table H2, column 4. 1999 Probabilities. Probabilities were revised based upon the construction of the pins and dewatering measures with 1999 groundwater conditions. A graph of shear strength verses factor of safety was prepared (Figure HS-11). The L999 soil shear strength of 12.1° corresponded to a factor of safety of 1.30. The mean shear strength was once again the value determined from the 1997 analysis, and the coefficient of variation was again assumed to be 30%. The revised strength values were normalized and the azeas these values occupied under the normal distribution curves were computed. These azeas correspond with the probabilities assigned to each outcome. Probabilities of outcomes based on the 1999 condition aze Barr Enpineerinp Company PCDOC51209220/CAK July 37, 1999 25 Appendix H 1999 Addendum to 7997198 Landslide CorreMive Measures Report