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 3 of 13 of the slope is mapped as the Feltville Formation, which consists of sandstone, siltstone or mudstone. A high-angle fault with no history of activity is mapped about 2,000 ft to the east of the site. An abandoned sandstone rock quarry is also identified about 1,000 ft southeast of the site. A copy of the geologic map is provided as Figure 2. SUBSURFACE INVESTIGATION A targeted subsurface investigation for the global slope stability study consisting of borings and test pits was completed between November and December 2024. A supplemental subsurface investigation for the global slope stability study located at the northern portion of the subject area consisting of borings, test pits and a rock outcrop and boulder evaluation was completed between April and June 2025. Both investigations were performed under full-time supervision by Langan. The borings and test pits were performed at accessible areas along four cross-sections running in the east-west direction through the subject area. The locations of the borings, test pits and cross-sections are shown on Figure 1. Logs of the borings and test pits are provided in Appendix A and Appendix B, respectively. Borings Eight (8) borings, identified as LB-1 through LB-4 and NLB-1 through NLB-4, were drilled within the subject area by Craig Geotechnical Drilling Co. Inc. (Craig). The borings were performed using a track-mounted drill rig and mud-rotary drilling techniques. Borings extended approximately 19 ft to 50 ft below existing surface grades. Borings NLB-2, NLB-4, LB-1 and LB-3 were performed at the higher portion of the slope near the proposed Building D footprint. Borings NLB-1 and NLB-3 were performed at the lower portion of the slope near the northeastern property line. Borings LB-2 and LB-4 were performed east of the existing sewer easement located at the lower portion of the slope. Soil samples were collected, and Standard Penetration Tests (SPT) were performed using a standard 2-inch outside-diameter split-spoon sampler driven by a 140-pound automatic hammer in accordance with ASTM D1586. Soil sampling and SPTs were typically performed continuously in the upper 12 ft and at 5 ft intervals thereafter. Recovered soil samples were visually

d automatic hammer in accordance with ASTM D1586. Soil sampling and SPTs were typically performed continuously in the upper 12 ft and at 5 ft intervals thereafter. Recovered soil samples were visually examined and classified in the field in accordance with the Unified Soil Classification System (USCS). Where encountered, rock was cored for a minimum of 10 ft using an NQ-sized core barrel. Test Pits Eight (8) test pits, identified as TP-1 through TP-8, were excavated by Frank Semeraro Construction Co., Inc. (Semeraro) using a John Deere 75G excavator during the initial subsurface investigation. Five (5) test pits, identified as NTP-1 through NTP-5, were excavated at the northeastern portion of the subject slope area by Semeraro using a CAT 308 Excavator or Hitachi 7X85 excavator during the supplemental subsurface investigation. The test pits extended approximately 3.5 ft to 13 ft below existing surface grades. Upon completion, the test pits were backfilled with excavated materials and the backfill was compacted with the excavator bucket.