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 4 of 5 respectively. In addition to the base cases described above, we analyzed groundwater at the the top of decomposed rock. Factors of safety greater than 1.5 resulted, indicating stability. Analysis Sections C-C’ and D-D’ Our base case static and seismic analyses used the base groundwater level encountered in our one test pit. The results of the static case indicate the lowest factors of safety exceed 1.5, indicating stable slopes. The potential slip plane surface that resulted in the lowest factor of safety was limited in length to roughly 100 feet to 125 feet and occurred east of the rock outcrop as a slip surface within the upper 6 feet of soil. Similarly, the results of the dynamic (seismic) case indicate the lowest factors of safety to be greater than 1.2, indicating stable slopes during a potential earthquake. In addition to the base cases described above, we analyzed groundwater at the the top of decomposed rock. Factors of safety greater than 1.5 resulted, indicating stability. Construction Related Blasting Impacts We understand up to 25 feet of rock is expected to be excavated from one localized area at the top of the Subject Slope in order to reach design grades for Building D. If blasting is to be performed for construction, we recommend using controlled blasting techniques, which include but are not limited to line and/or channel drilling, limiting charge per delay, use of blasting mats, and performing vibration monitoring to assess the effects of blasting. Controlled blasting techniques thereby limit the amount of energy transmitted to the surrounding rock, generally limit the nuisance impacts of construction compared to conventional earth excavating methods (i.e., less time to excavate and haul off material), and limit the potential for impacts to neighboring properties. OPINIONS Based on our investigation and analysis, the Subject Slope is not at risk of failure under current conditions or from proper construction of Building D. Our analyses further indicate that there would be negligible impact on the global stability of the Subject Slope even if groundwater levels were to rise. However, direct precipitation and runoff can be expected to flow over the

te that there would be negligible impact on the global stability of the Subject Slope even if groundwater levels were to rise. However, direct precipitation and runoff can be expected to flow over the sloping ground surface with some lesser amount of infiltration, and the development is not expected to increase stormwater run off toward the Subject Slope. As part of the proposed development, we understand that appropriate drainage and conveyances will be provided to prevent site development stormwater from entering the Subject Slope. LIMITATIONS Our study is based on the geotechnical subsurface data collected at accessible locations within the Study Area, the topographic survey data, currently existing site conditions and proposed building information made available to us. Any proposed changes in proposed structures