2025 06 18 WEH Slope Stability Analysis Letter Report

MEMO Global Slope Stability Study for Building D West Essex Highlands Project Langan Project No.: 101049801 Revised 18 June 2025 Revised 18 June 2025 - Page 7 of 13 the proposed Building D footprint and down the subject area slope to the eastern residences for our slope stability analyses. We also chose two additional sections (section C and section D) across the northeastern portion of the subject area and down the subject area slope near the northeastern residences on Howell Drive. The locations of the sections are shown on Figure 1. 3. We estimated strength parameters for the soil based on visual observation and the collected N-value results obtained during sampling. 4. We estimated strength parameters for the rock based on laboratory testing results and rock recovery and rock quality designation values obtained in the rock cores. 5. We analyzed the global slope stability using LEM for the estimated proposed Building D load and access road load and we calculated factors of safety with respect to global stability for the static condition. 6. We analyzed the slope stability using the LEM for the combined service and seismic loads and we calculated factors of safety with respect to global stability for the maximum considered earthquake. We used the computer software SLOPE/W for the LEM analyses. An overview of our analyses and a summary of our results are presented below. Model Parameters Model Geometry For our two-dimensional global stability analyses, we selected two representative cross-sections (section A and section B) across the proposed Building D footprint extending to the eastern property line in the subject area. The eastern property line is approximately 900 ft east of the proposed Building D footprint. We also selected two representative cross-sections (section C and section D) across the northern portion of the proposed Building D footprint and proposed access road north of the Howell Drive cul-de-sac extending to the northeastern property line. The northeastern property line is approximately 200 ft and 250 ft east of the proposed access road and proposed Building D footprint, respectively. The soil and rock elevations used in the model are based upon the results of available subsurface investigation information, which was collected from the accessible explored areas of the site. Material Properties The generalized subsurface conditions

based upon the results of available subsurface investigation information, which was collected from the accessible explored areas of the site. Material Properties The generalized subsurface conditions consisted of surficial materials (topsoil) underlain by natural sand and silt over decomposed rock and rock strata. No subsurface investigation was performed beyond the northeastern property line as part of the supplemental investigation.