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 8 of 21 Construction Considerations Our review of the reference reports indicates that a principal concern for slope stability expressed by Princeton Hydro is that the construction, which involves excavations in rock to a depth of approximately 25 feet below the top of rock at the high point of the ridge, could lead to disturbance and weakening of the slope, particularly if blasting is used. We understand that Langan’s reply indicates that it is their opinion that it is too early in the planning stage to determine whether blasting needs to be employed, and, if it is required, the size of the blasting charge can be controlled to reduce vibration effects on the slope. For the purpose of our review, we recommend that the following construction-related conditions be addressed in the requirements that are set forth in this Planning Board Review and subsequent Municipal Reviews of the application for construction permits: 1. Clearing Site 2. Protection of the forestry on the slope 3. Soil Erosion and Sediment Control 4. Limitation of surcharges and equipment loads 5. General Excavation 6. Rock Excavation 7. Dewatering and control of runoff 8. Final Grading and Landscaping REVIEW OF EXISTING SITE CONDITIONS General This section covers a review of the existing topographic, geologic and subsurface conditions. Our review is based on both the descriptions contained in the Applicant’s and Objector’s Engineer’s reports and the references cited above. Geologic and Seismic Design Considerations The existing ridge is a segment of a prominent geological feature known as the Second Watchung Mountain. The bedrock Geology mapping was included on the map entitled “Bedrock Geologic Map of Caldwell Quadrangle” (Reference 6A). A section of this map is contained in the Langan Report dated June 18, 2025 as Figure No. 2. We have attached an extracted copy of Figure No. 2 for ease of reference by the Board. Our interpretation of the information is as described below: 1. The bedrock on the upper ridge is included in the unit described as the Preakness Basalt with map symbol

ease of reference by the Board. Our interpretation of the information is as described below: 1. The bedrock on the upper ridge is included in the unit described as the Preakness Basalt with map symbol Jp. The basic map description is given as Dark Greenish Gray to black fine-grained, dense and hard. Quarried basalt is usually high strength from deep within