Langan Rebuttal Report 9 15 2025

15 September 2025 Mark Hoffman Garden Homes Management 820 Morris Turnpike, Suite 301 Short Hills, New Jersey 07078 Re: Global Stability Study for Eastern Slope near Building D West Essex – Highlands Development West Orange, New Jersey Langan Project No.: 101049801 Dear Mr. Hoffman: As requested, in conjunction with the above-referenced study Langan Engineering and Environmental Services, LLC (Langan) has reviewed letters prepared by Princeton Hydro (“Princeton”), who has been retained by Objectors to the proposed Development. The Princeton letter, dated 16 July 2025, summarized their comments under four primary issues (below): 1. 2. 3. 4. Building Layout Currently Proposed Closer than Concept Parameters of Slope Stability Analysis Do Not Match Actual Conditions Geologic Hazard Review Unjustified in Dismissing the Risks Blasting Implications and Threats to Stability of the Slope Must be Addressed Before Approval In a follow up letter dated 12 August 2025, Princeton provided a slope stability analysis at site locations they defined as “Model Cross Sections C and D”, which loosely correspond to analysis sections C-C and D-D from Langan’s letter report dated 18 June 2025. In the following sections, Langan provides responses to the four primary issues raised in Princeton’s 16 July 2025 letter. In general, it is very important to note that Princeton’s slope stability analyses at the two above referenced cross sections indicated the slope to be stable with adequate factors of safety, even after Princeton assigned a much lower strength value to the rock at the site than was used in Langan’s analysis. Princeton’s slope stability results, therefore, are in general agreement with the Langan conclusions and contradict the basis for Princeton’s slope concerns which they expressed in their aforementioned letters and 16 July 2025 testimony by Geoffrey Goll. To make abundantly clear, our analysis demonstrates that the existing slopes are stable and that the new building does not change the loading condition on the slope; therefore, no change in the slope stability. Schematics below show the general area beneath the central and northern portions of the building where foundation loading occurs and will be distributed in soil. These schematics show the limited influence of the building loading, and specifically no influence on the slope.

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 2 of 7 Princeton Comment: Building Layout Currently Proposed Closer than Concept Langan Response: It is common for slight adjustments to be made between conceptual site layout and final layout. Langan utilized the most recent building layout in our slope stability analysis and concluded the slope is currently stable and will be stable under the proposed loading.

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 3 of 7 Princeton Comment: Parameters of Slope Stability Analysis Do Not Match Actual Conditions Langan Response: Princeton initially identified seven subparts associated with their position. Five of 7 relate to rock properties used in our model, one relates to building loading, and one relates to the presence of a sewer. In Princeton’s 12 August letter they provided analyses using their interpretation of our data. Overall, Princeton repeatedly claims our design values are incorrect, yet they clearly misinterpret the data and mis-apply it. Princeton is mistakenly focused on the rock parameters as being the primary controlling factor in the slope stability analysis. Although rock strength is important, the soil properties control the stability of this slope. Princeton implies that the critical section for slope stability would extend through the underlying rock stratum. Our output files, provided in our 18 June report, clearly demonstrate that all slope stability critical surfaces (i.e., lowest factors of safety) pass through the overlying soil. Princeton’s slope stability output files also clearly demonstrate that the overlying soil properties control the slope stability. The only way for the rock to govern the stability under the design loading conditions would be if the rock strength were lower than the overlying soil strength. Despite both Langan and Princeton proving that point, Princeton incorrectly maintains the rock strength is the primary controlling factor in the slope stability analysis. As there is no grading proposed on the slope, the soil properties do not change between the existing and post development conditions (i.e., no change in the stability). Princeton also incorrectly stated that Rock Quality Designation (RQD) defines rock mass quality. ASTM D6032 is the Standard Test Method for Determining Rock Quality Designation of Rock Core. The significance and use of this standard is to provide a "simple and inexpensive general indication of rock mass quality". However, RQD, which is determined from 2-inch diameter rock cores, is one basic component of rock mass classification systems which are used in engineering analysis and design to better understand rock mass

r, RQD, which is determined from 2-inch diameter rock cores, is one basic component of rock mass classification systems which are used in engineering analysis and design to better understand rock mass quality. Fundamentally, RQD is used to identify potential problems within a rock mass and to provide a basis for making preliminary decisions. The Standard clearly states that RQD alone is not sufficient to provide an adequate description of rock mass quality; and, RQD must be used in combination with other geological and geotechnical input. The Rock Mass Rating (RMR) System (aka, Geomechanics Classification System by Bieniawski, 1989) is a widely accepted and utilized method of classifying/categorizing rock masses in terms of general “quality” based on physical and mechanical properties and is used to aid in the prediction of rock mass behavior. The RMR System assigns numerical values to six important parameters (UCS, RQD, Joint Spacing, Joint Condition, Groundwater, and Joint Orientation). It is universally agreed that the RMR system is appropriate for rock mass of good to reasonable quality (i.e., GSI>25, per Hoek and Brown). We assigned values to the RMR System (see Exhibit A) and find the rock mass to be predominantly Fair to Good Quality, not Very Poor Quality as erroneously suggested by Princeton. Princeton claimed we chose the most competent rock to select model properties, yet our model clearly shows we assigned design values (GSI, UCS, Disturbance, etc.) in our slope stability analysis that are appropriate based on our borings, laboratory testing and evaluation of the rock mass quality and characteristics. Princeton recognized that basalt should have considerably higher uniaxial compressive strength values, but they incorrectly correlated the

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 4 of 7 relatively lower unconfined compressive strengths to “significant weathering”, which failed to recognize that other properties such as porosity and microstructural attributes (grain size and shape) tend to govern the unconfined compressive strength of brittle rock (Gueguen & Bouteca, 2004). Princeton’s 12 August model of sections C and D utilized a GSI of 20 and a UCS of about 2300 psi. Rock material having the Princeton assigned values would equate to a very poor quality seamy/disturbed rock or a poor quality disintegrated rock. However, our summary of the rock structure and quality in the table below shows a narrow range in structure from predominantly blocky to very blocky (at one location) and generally good quality to fair quality rock. The upper 5 feet of the rock at NLB-1 (our analysis section C-C and Princeton’s model section C) exhibits rough slightly weathered joint conditions, which are considered Good surface quality within the GSI system, not very poor surface quality as suggested by Princeton. In addition, field estimates of typical intact rock strength are shown to range from roughly 3,625 psi to 36,250 psi, the upper end of which is more closely associated with basalt. Nonetheless, we modeled analysis section C-C using a GSI value of 37 and a comparatively low intact rock strength and there was no change in the factor of safety (Exhibit B). Rock core photos are provided in Exhibit C. Princeton’s reference to using a factor of safety of 2.0 is simply not applicable. The EM 1110-1-2908 reference is applicable to US Corp of Engineer facilities built on rock that experience a lateral load (e.g., a dam), which if the slope failed would be catastrophic to neighboring properties. This development clearly does not apply. A factor of safety of 1.5 is applicable for the subject slope. Rock deformation modulus, which is measure of a rock mass’s resistance to deformation under load, calculated using a GSI of 20 and Disturbance factor of 1 (Hoek and Brown, 2018), indicates a range in values of 35 to 68 MPa, which is only 2 to 4 times greater than the unconfined compressive strength of the rock. The modulus should be hundreds of times greater than the unconfined compressive

ange in values of 35 to 68 MPa, which is only 2 to 4 times greater than the unconfined compressive strength of the rock. The modulus should be hundreds of times greater than the unconfined compressive strength of the rock. Therefore, using a GSI of 20 is not representative of the rock mass throughout the site. For comparison, the estimated deformation modulus of rock having a GSI of 65 ranges from about 2,000 to 8,000 MPa depending on the Disturbance factor.

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

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 6 of 7 favorably oriented, which are conditions that control stability in jointed hard rock formations such as the basalt. Princeton Comment: Blasting Implication and Threats to Stability of the Slope Must be Addressed Before Approval Langan Response: There has been much discussion concerning blasting; however, Langan is not aware of any plan to blast rock at the site. Based on the available subsurface information, the homes closest to rock to be excavated are roughly 450-500 feet away. Langan maintains its opinion that if blasting is used to excavate rock, controlled techniques should be used to control impacts to the rock mass such as overbreak. Langan has no knowledge of the means and methods that will be selected by the Developer’s contractor to excavate soil and rock at Building D. However, the following paragraphs address methods of rock excavation that would be appropriate for the conditions encountered. As indicated in our 18 June report that the upper rock could not be penetrated by the excavation equipment used during the investigation which included John Deere 75G, CAT 308 and Hitachi 7X85 excavators, all of which are smaller than the type of equipment we expect to be used during construction. Nonetheless, specialized equipment is expected to be required for ripping rock. Hoek-Karzulovic, 2000; and, Abdullatif and Cruden, 1983 indicate rock masses having GSI values up to 40 (1 MPa) can be excavated by conventional means, rock masses having GSI values up to 60 (10 MPa) can be ripped, and for rock masses having GSI over 60 (>15 MPa) blasting has typically been utilized. Splitters and chemical expanders can generate pressures up to 43 MPa and 30-44 MPa, respectively. These methods work based on the tensile strength of rock, which is typically 6-15% of the rock’s compressive strength (Al-Bakri and Hefni, 2021). If the basalt at the subject slope has a GSI value of 20 as suggested by Princeton, we would expect the contractor to use conventional excavation methods, not blasting. Our findings indicate most of the section of rock mass to be excavated (i.e., the large outcrop roughly 450-500 feet from Howell Drive) has a GSI value of roughly 65 but is expected to range as low as about 50.

gs indicate most of the section of rock mass to be excavated (i.e., the large outcrop roughly 450-500 feet from Howell Drive) has a GSI value of roughly 65 but is expected to range as low as about 50. Such rock is expected to require some combination of mechanical methods to excavate, including large excavators or loaders equipped with ripping teeth or shanks, hoe rams, and splitters. However, locally and at a minimum as a starter method, splitters and chemical expanders would also be effective on the higher GSI material, as would controlled blasting methods. If controlled blasting is used to excavate the rock (including properly designed and implemented channel and line drilling), the blast should be designed to produce a locally (i.e., the building limits) fractured rock mass having the maximum quality such as a GSI value of 40-60 (i.e., least disturbance) that allows for mechanical removal. Regardless of the method used, the excavation should be designed by the contractor to prevent over breakage of the rock and damage to nearby structures.