2025 06 18 WEH Slope Stability Analysis Letter Report

Global Slope Stability Study for Building D West Essex Highlands Project Langan Project No.: 101049801 Revised 18 June 2025 Revised 18 June 2025 - Page 10 of 13 MEMO fraction of the anticipated peak acceleration (amax). Hynes-Griffin and Franklin (1984)1 seismic coefficient equation kh=0.5amax/g is considered appropriate to use for most slopes (Kramer, 1996)2. For this site, we utilized the Hynes-Griffin and Franklin (1984) criteria that resulted in kh=0.0875. To consider the effect of the proposed construction on slope stability, the critical slip surfaces for the existing and proposed seismic loading conditions for Sections A, B, C and D are provided in the tables below. LEM analysis results under seismic conditions satisfy a minimum acceptable factor of safety of 1.15 and are presented in Appendix F. Table 3A: LEM Factors of Safety against Sliding for Seismic Loads – Section A Condition Critical Slip Surface Critical Slip Surface That Reaches the Downslope Building Existing 1.65 2.23 Proposed 1.65 2.23 Table 3B: LEM Factors of Safety against Sliding for Seismic Loads – Section B Condition Critical Slip Surface Critical Slip Surface That Reaches the Downslope Building Existing 1.29 4.59 Proposed 1.30 4.59 Table 3C: LEM Factors of Safety against Sliding for Seismic Loads – Section C Condition Critical Slip Surface To Upper Tier Retaining Wall Existing 1.26 Proposed 1.26 Table 3D: LEM Factors of Safety against Sliding for Seismic Loads – Section D 1 2 Condition Critical Slip Surface within Site Limits Existing 1.47 Proposed 1.47 Hynes-Griffin Mary E; Franklin Arley G (2007). “Rationalizing the Seismic Coefficient Method”. Department of the Army. Steven L Kramer. “Geotechnical Earthquake Engineering” 1996.