Langan Rebuttal Report 9 15 2025

Global Stability Study for Eastern Slope near Building D West Essex – Highlands Development West Orange, New Jersey Langan Project No.: 101049801 15 September 2025 Page 5 of 7 Princeton also claimed we used incorrect values for the overlying soil in their 12 August letter. Their model of sections C and D use a thicker medium dense section than exists. We provide in Exhibit D a summary of the Standard Penetration Test N-values and their associated correlations to strength parameters for the soils encountered in our borings. We have stated that our design parameters are lower bound (conservative) values, as clearly shown in the graphic. Yet, Princeton continues to misinterpret the available data. In their 12 August models for sections C and D, they assigned 32 degrees friction to a 20-foot-thick section of soil, despite there being only one boring location (NLB-3) where a 4-ft-thick-layer of the upper sands was encountered to have N-values that correlate to 32 degrees. The average friction value for these soils in our Sections C-C and D-D are 39 degrees and 45 degrees, respectively. Princeton mistakenly stated Langan dismissed Building D loading at the top of the slope. Princeton also mistakenly stated Langan did not model the excavation. We modelled the proposed loading conditions, just as we said we did in our report. We also modelled a strip load of 4 ksf; neither a strip load nor a uniform load had an impact on the slope stability. Princeton also stated we should not ignore the Feltville Formation. The borings (LB-2 and LB-4) in our analysis sections C-C and D-D were terminated in decomposed rock (roughly 50 feet below ground) based on split-spoon refusal values. The critical surfaces for all our slope stability models did not extend into the decomposed rock stratum for any of the design cases. As demonstrated above, the Feltville Formation also does not factor into the slope stability due to its depth and the fact that decomposed rock is stronger than the overlying soils. We modeled our analysis sections A-A and B-B with the discontinuity of the wastewater utility line as a trench of medium dense sand having a friction value of 32 degrees extending from ground surface to the decomposed rock over 30 feet below the existing grade. Our models show that there is no change in the location of the critical failure surfaces or corresponding factors of safety

ground surface to the decomposed rock over 30 feet below the existing grade. Our models show that there is no change in the location of the critical failure surfaces or corresponding factors of safety (Exhibit B). Princeton Comment: Geologic Hazard Review Unjustified in Dismissing the Risks Langan Response: Langan has not dismissed any risk of a slide. We were retained to investigate and analyze the slope subsurface conditions to assess the slope stability risk. Langan performed the necessary investigations including borings, test pits and outcrop mapping. Langan concluded that the outcrops and overall slopes are stable under existing and proposed conditions. Furthermore, Princeton mistakenly dismissed rock outcrop mapping and stated that the slopes would be susceptible to landslides based solely on RQD results. Rockfall hazard was assessed by Langan and was found to be low based on the predominance of favorable joint orientations. Furthermore, Mr. Goll’s testimony suggested a fictitious rock mass instability could develop during the limited excavation of rock in the building footprint beyond the top of the ridge and further suggested that rock anchors would likely be used to stabilize the rock mass. This idea that the rock in the slope would fail without any disturbance in the slope completely ignores the fact that the rock structure/jointing is both relatively rough and