25 10 28 Slope Stability Review

Chairman and Members of the West Orange Planning Board Application No. PB24-01, West Essex Highlands, LLC, Warner Road, Block 179, Lot 32 Review of Applicant’s Engineer’s Slope Stability Analysis Reports, the Objector’s Engineer’s Response Reports; and the Applicant’s Engineer’s Rebuttal Report October 28, 2025 Page 13 of 21 rock. The test pits extended to depths of 12, 14, 16 and 9 feet below the existing grade respectively. Bedrock was reported encountered only in Test Pit D2. The report included the results of grain size tests, moisture content and falling head permeability test results for bulk samples taken from the test pits. INFERRED SUBSURFACE CONDITIONS General Our review indicates that Langan has prepared a generalized stratigraphy for their stability analysis that conforms generally to the anticipated geology contained on the reference geologic mapping of bedrock and surficial geology of the Caldwell Quadrangle. The stratigraphy is shown on the attached markup of the Langan Analysis Sections A through D. Our review is summarized below. In addition, we have reviewed comments on the inferred stratigraphy provided by Princeton Hydro for the Objector in this section of the letter. Generalized Stratigraphy for Stability Evaluation The soil overburden varied from 7 to 20 feet thick in the borings that encountered the underlying Basalt. Borings LB-2 and LB-4 were advanced to depths of 50 and 45 feet and did not encounter Basalt. The soil overburden conformed to the following generalized stratum as established by Langan for their evaluation of the stability of the slope: Topsoil: The boring’s sample descriptions indicate a “topsoil” layer approximately two feet thick with field standard penetration test values indicating that the layer is generally in a loose state of compaction. Langan has assigned a strength envelope with cohesion of 0 psf and a friction angle of 30 degrees. Medium Dense Sands: Medium dense sands with field standard penetration test values indicating that they are in a medium dense state were indicated on the Analysis Sections below the topsoil in the NLB borings on Cross Sections C and D. On Analysis Sections A and B, the medium dense sands are shown as an inclusion within the dense to very dense glacial tills. Langan has assigned a strength envelope equivalent to a cohesion intercept of 0 psf and an angle of internal friction of 32

ands are shown as an inclusion within the dense to very dense glacial tills. Langan has assigned a strength envelope equivalent to a cohesion intercept of 0 psf and an angle of internal friction of 32 degrees. Dense to Very Dense Sands with varying percentages of Silt and Gravel: Most of the borings encountered dense sands with field blow counts indicating that the materials are dense to very dense. Boulders were encountered within this layer. These sands conform generally with the materials described as yellow Rahway till on the Surficial Geology