2025 06 18 WEH Slope Stability Analysis Letter Report

Global Stability Study for Eastern Slope near Building D West Essex – Highlands Development West Orange, New Jersey Langan Project No.: 101049801 14 January 2025 Revised 18 June 2025 Page 2 of 5 The Subject Slope descends about 150 feet in elevation to the east from the east side of proposed Building D at an overall slope of roughly 10 degrees (or roughly 17%) to the neighboring properties located on Rosemont Terrace and Mayfair Drive. The distance to the adjacent Rosemont Terrace and Mayfair Drive developments at the bottom of the slope is roughly 700 feet east of the proposed Building D. Immediately to the north of proposed Building D, the ground descends about 50 feet in elevation to the top of a 2 tiered timber and modular block retaining walls located on the property at 15 Howell Drive at a slope of roughly 19 degrees (roughly 35%). A site location map showing the approximate limits of the Study Area is provided below. As part of our supplemental investigation performed between April and June 2025, we mapped rock outcrops and boulders with the Study Area to account for variations in the slope. In general, the subsurface profile in the northernmost part of the study area (upslope from 15 Howell Drive) consists of a relatively thinner relatively dense soil overly hard basalt bedrock the upper 0.5 feet to 4 feet of which was found to be fractured and barely rippable using an excavator. The overburden soils thicken south of the 2-tiered retaining wall. Generalized subsurface conditions encountered in the borings and test pits, and from our mapping revealed the balance of the Study Area to consist of relatively shallow (outcrop to 15 feet deep) hard rock in and near the top of the slope where proposed Building D is to be located. Soils consisted of up to 2 feet of silty, sandy topsoil over relatively dense gravelly sandy soils overlying basalt bedrock at the top of the slope with similar dense sands over basalt and sedimentary bedrock at greater depths lower on the slope further to the east.