2025 01 14 West Essex Highlands Development Building D Slope Stability Study

Global Slope Stability Study for Building D West Essex Highlands Project Langan Project No.: 101049801 14 January 2025- Page 6 of 11 MEMO 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 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. 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 consisted of surficial materials (topsoil) underlain by natural sand and silt over decomposed rock and rock strata. Due to steep slope geometry, no subsurface investigation was performed at the lower slope located northeast of proposed Building D. 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 on the following page. Table 1: Soil Strength Properties Soil/Rock Unit Weight (pcf) ϕ' (deg.) 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 = = =

Global Slope Stability Study for Building D West Essex Highlands Project Langan Project No.: 101049801 14 January 2025- Page 7 of 11 MEMO 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 (mi) 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 For our main analysis, groundwater was assumed to be at the top of the decomposed rock / very dense granular soil layer. It should be noted that our subsurface investigation was performed during a time of drought and not during the wet season. To account for groundwater fluctuation, a parametric sensitivity analysis was also performed to evaluate the impact of higher groundwater. 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. 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 effect of the proposed construction on slope stability, the critical slip surfaces for the existing and proposed gravity (static) loading conditions for Sections A and B are provided in the tables below. LEM analysis results under gravity loading (static) conditions are presented in Appendix D. Table 2A - LEM Factors of Safety against Sliding for Service Loads – Section A Condition Critical Slip Surface Critical Slip Surface That Reaches the Downslope Building Existing 2.20 3.29 Proposed 2.20 3.29 = = =

Global Slope Stability Study for Building D West Essex Highlands Project Langan Project No.: 101049801 14 January 2025- Page 8 of 11 MEMO Table 2B - LEM Factors of Safety against Sliding for Service Loads – Section B Condition Critical Slip Surface Critical Slip Surface That Reaches the Downslope Building Existing 1.67 6.46 Proposed 1.67 6.45 Seismic Slope Stability Analyses Seismic slope stability analyses have traditionally been performed by using pseudo-static limit equilibrium analyses. These analyses consist of applying a lateral force to the slope equal to the product of a seismic coefficient (kh) and the weight of the slope. The seismic coefficient is based on the actual anticipated level of acceleration in the failure mass and corresponds to some 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 and B are provided in the tables below. LEM analysis results under seismic conditions are presented in Appendix E. 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 1 2 Condition Critical Slip Surface Critical Slip Surface That Reaches the Downslope Building Existing 1.29 4.59 Proposed 1.30 4.59 Hynes-Griffin Mary E; Franklin Arley G (2007). “Rationalizing the Seismic Coefficient Method”. Department of the Army. Steven L Kramer. “Geotechnical Earthquake Engineering” 1996. = = =

Global Slope Stability Study for Building D West Essex Highlands Project Langan Project No.: 101049801 14 January 2025- Page 9 of 11 MEMO Parametric Sensitivity Analysis due to Groundwater Level We performed sensitivity analyses to evaluate the impact of groundwater on the slope stability for the static loading condition. We evaluated the groundwater effect with the groundwater level located immediately below the topsoil layer, at the top of the decomposed rock/very dense sand layer and at the top of the rock stratum. The estimated resulting factors of safety are provided in Table 4A. Table 4A: LEM Factors of Safety against Sliding for Gravity Loads with Groundwater Groundwater Level Section A (Critical Slip Surface) Section B (Critical Slip Surface) Immediately Below Topsoil 1.36 1.54 Top of Decomposed Rock / Very Dense Granular Soil 2.20 1.67 Top of Rock 2.26 1.68 We also performed an infinite slope analysis for the varying groundwater level conditions as part of the sensitivity analysis. The critical slip surfaces were modeled to be at varying groundwater levels. The estimated resulting factors of safety from this analysis are provided in Table 4B. Table 4B: LEM Factors of Safety against Sliding for Gravity Loads with Groundwater (Infinite Slope Analysis) Groundwater Level/Critical Slip Surface Location Section A Section B Immediately Below Topsoil 3.44 3.09 Top of Decomposed Rock / Very Dense Granular Soil 3.94 3.87 Top of Rock 5.28 4.57 EVALUATION We utilized the NAVFAC Design Manual 7.1 “Soil Mechanics” (NAVFAC 1986) reference in the evaluation of the factors of safety calculated in our global slope stability evaluation for the static and seismic design loading conditions. This manual indicates that a factor of safety of no less than 1.5 should be utilized for permanent or sustained (static) loading conditions of slopes. This manual indicates that a factor of safety of no less than 1.15 should be utilized for seismic loading conditions of slopes due to earthquakes. = = =

MEMO Global Slope Stability Study for Building D West Essex Highlands Project Langan Project No.: 101049801 14 January 2025- Page 10 of 11 We modeled the existing slope and the proposed building loads per the available topographic survey plan, boring and test pit data and the anticipated building and seismic loads as outlined in the “Modeling Parameters” section of this memorandum. Geologic Hazard Review Based on rock maps and our subsurface findings, igneous basalt rock is near the surface at the upper portion of the slope with a few visible rock outcrops. The lower portion of the slope is anticipated to consist of sedimentary rock as part of the Feltville Formation at depth greater than 50 ft from existing surface grade based on the subsurface investigation. The eastern slope does not appear to have significant amounts of exposed rock outcrops along the slope so rock fall hazard due to the toppling of exposed rock faces would be limited. Due to the relatively shallow slope and distance to adjacent properties, rock fall does not appear to be a high risk. Based on a review of New Jersey earthquake history provided by the New Jersey Department of Environmental Protection (NJDEP), the seismic risk of the site appears to be low. Stability for Gravity Loading Condition Our evaluation indicates that the factor of safety values for the gravity loading (static) condition for both the existing and proposed conditions is greater than the minimum required safety factor of 1.5, indicating stable slopes. The proposed construction of Building D will have a negligible impact on the global stability of the eastern slope as shown in Tables 2A and 2B. Stability for Seismic Loading Condition Our evaluation indicates that the factor of safety values for the seismic loading (dynamic) condition for both the existing and proposed conditions is greater than the minimum required safety factor of 1.15, indicating stable slopes. Additionally, the proposed construction of Building D will have a negligible impact on the global stability of the eastern slope as shown in Tables 3A and 3B. Groundwater Impacts Our sensitivity analysis associated with groundwater level indicates the factors of safety with respect to global stability generally decrease when the water level increases. Although highly unlikely, we modeled the groundwater immediately below the topsoil layer resulting in a

rs of safety with respect to global stability generally decrease when the water level increases. Although highly unlikely, we modeled the groundwater immediately below the topsoil layer resulting in a factor of safety of 1.36 for the critical potential failure surface. This potential slip surface is surficial and does not pose an impact on the downslope residences. The lowest factor of safety against sliding for gravity loads at varying groundwater levels was approximately 3.09 when the groundwater was modeled to be below the topsoil layer for the infinite slope analysis. This is above the minimum required safety factor of 1.5, indicating stable slopes. = = =

MEMO Global Slope Stability Study for Building D West Essex Highlands Project Langan Project No.: 101049801 14 January 2025- Page 11 of 11 As part of the proposed development, we understand that appropriate drainage conveyances will be provided to prevent site development stormwater from entering the eastern slope. As such, the proposed construction of Building D will not have an impact on increasing groundwater levels at the eastern slope. LIMITATIONS Our evaluation is based on the geotechnical subsurface data collected at the subject area (at accessible areas), the topographic survey data, currently existing site conditions and proposed building information made available to us. Any proposed changes in proposed structures (location, layout, loading, elevation) or existing slope conditions should be brought to our attention so that we can determine whether such changes affect our conclusions. CLOSURE This memorandum summarized our global slope stability analyses and results associated with the proposed eastern slope of the West Essex Highlands project site located in West Orange, New Jersey. \\langan.com\data\PAR\data8\101049801\Project Data\_Discipline\Geotechnical\Reports\2024 - Slope Stability Memorandum\2025-01-14- Attachment A - Slope Stability Analysis Memo.docx = = =

FIGURES Figure 1 Figure 2 Boring and Test Pit Location Plan with Building Sections A and B Geological Map = = =

TP-F2 TP-F1 B-11 FF: 618.0 GF: 607.0 BUIL D ING 101147901 D.1 TP-12 B-12 TP-1 AA el 606 > 9 ft belowLB-1 elel597 597 TP-8 beyond TP-2 TP-3 LB-2 A A 3 LB-1 el 606 11 13 ft el 595 593 el el 582 582 > 5.5 4 ft ft below 576.5 el el 578 el 604 14 ft el 590 el 522 >> 50 50 ftft below elel472 beyond 472 el 550 >> 12 12 ftft below elel538 beyond 538 TP-13 FF:618.0 GF: 597.0 TP-E2 B-13 TP-D1 FF: 618.0 GF: 594.0 TP-14 BB LB-3 TP-4 TP-4 T LB-3 TP-7 el el616 616 3.75 > 5 ft el 612.2 below el 611 TP-5 TP-5 LB-4 TP-6 TP-6 B el 584 >4.5 4.8ftft below elel579.2 beyond 579.2 el 579.5 el 528 > 12 ft below elel516 beyond 516 LB-4 B el 548 584 el > 45ftft >45 below el beyond el 503 503 DING D.2 el el 614 614 > 3.5 3.7 ftft below el 610.3 el 610.5 el 614 9 ft el 605 TP-D2 B-14 BUIL TP-15 LGF: 582.0 TP-C2 1. BASE PLAN OBTAINED FROM PLAN TITLED "OVERALL GRADING PLAN SP-11" DATED 1 OCTOBER 2024 PREPARED BY ANDERSON CONSULTING SERVICES LLC (ACS).AND IS 1. AERIAL PHOTOGRAPH TAKEN FROM NEARMAP LB-1 ED 30 OCTOBER 2024. el 606 13 ft el 593 SCALE: 1" = 50' LEGEND: APPROXIMATE LOCATION OF LANGAN BORING Langan Engineering and Environmental Services, LLC. TP-1 APPROXIMATE SURFACE ELEVATION APPROXIMATE LOCATION OF LANGAN TEST PIT APPROXIMATE OVERBURDEN SOIL AND DECOMPOSED ROCK THICKNESS APPROXIMATE TOP OF ROCK Figure 101049801 101147901 A A APPROXIMATE LOCATION GLOBAL SLOPE STABILITY ANALYSIS SECTION 300 Kimball Drive Parsippany, NJ 07054 T: 973.560.4900 F: 973.560.4901 www.langan.com NJ CERTIFICATE OF AUTHORIZATION No. 24GA27996400 WEST ESSEX HIGHLANDS WEST ORANGE NEW JERSEY PROPOSED INVESTIGATION INVESTIGATION PLAN PLAN 1/14/2025 11/4/2024 1 RLB AY © 2021 Langan NOTES:

N APPROXIMATE SUBJECT SLOPE AREA LEGEND Preakness Basalt – Dark-greenish-gray to black, fine-grained, dense, hard basalt Feltville Formation – Reddish-brown or light-grayish-red, fine-to-coarse-grained sandstone, siltstone, shaly siltstone and silty mudstone. Source: Bedrock Geologic Map of The Caldwell Quadrangle, Essex and Morris Counties, New Jersey by Richard A. Volkert (2006) WEST ESSEX - HIGHLANDS GEOLOGIC MAP WEST ORANGE NEW JERSEY PROJECT NO. SCALE DATE FIGURE 101049801 N.T.S. 1/14/2025 1/13/2025 11/4/2024 2 \\langan.com\data\PAR\data8\101049801\Project Data\_Discipline\Geotechnical\Reports\2024 - Slope Stability Memorandum\Figure 2 - Geologic Map.docx