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 8 of 13 MEMO We estimated the material parameters including friction angle (ϕ’), of the surficial fill, natural soil and decomposed rock layers based on in-situ test data. The soil parameters utilized in our analyses are presented in Table 1 provided below. Table 1: Soil Strength Properties Soil/Rock Unit Weight (pcf) Friction Angle, ϕ' (deg.) Cohesion, c (psf) Topsoil 115 30 0 Medium Dense Sand 120 32 0 Dense Sand 125 34 0 Decomposed Rock/Very Dense Granular Soil 135 38 0 The rock encountered and cored during the investigation at the upper portion of the slope was classified as basalt. Rock properties were estimated using values recommended in the SLOPE/W manual and a Geologic Strength Index (GSI) of 65, an intact rock parameter (m i) of 17, a disturbance factor (D) of 1 and an unconfined compressive strength (UCS) of 316,800 psf (lowest laboratory value) were used in the analyses. Groundwater It should be noted that our original subsurface investigation was performed during a time of drought and not during the wet season. The supplemental investigation was performed at the end of the wet season as defined by the latest NJDEP stormwater best management practices manual and groundwater was not encountered in the test pits. Therefore, our primary analysis excludes groundwater, and our secondary analysis assumes a high groundwater level to be at the top of the decomposed rock / very dense granular soil layer. Proposed Building D Loading Proposed Building D will be 4-stories above structured parking. A total uniform service load of 1,000 psf was applied to the eastern slope to simulate the effect of the proposed building. This service load estimate was derived from live loads specified in the New Jersey UCC Building Subcode 2021 and an approximate estimation of the dead loads. A total uniform load of 250 psf was applied to the slope to simulate the effect of the proposed access road. LEM Analyses and Results (Service Loads) The LEM analyses were performed to represent the pre-construction condition and postconstruction condition after the construction of the structure. We used the Morgenstern-Price LEM for our analysis, which satisfies the equilibrium of forces and moments. To consider the

ition and postconstruction condition after the construction of the structure. We used the Morgenstern-Price LEM for our analysis, which satisfies the equilibrium of forces and moments. To consider the effect of the proposed construction on slope stability, the critical slip surfaces for