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 11 of 21 The ridge and slope area are wooded. We understand that the wooded area on the slope is protected by regulation. Effective maintenance of the health of the forested area is necessary to maintain the benefits of the forest towards the stability of the slope. West Orange Sanitary Sewer Easement The West Orange Sanitary Sewer easement traverses the upper slope from the top of the ridge (where it is to the south of the building) to its intersection on Howell Drive between the residences at 11 and 13 Howell Drive. The easement appears graded as a side hill bench. Langan has indicated the location and inferred depth in the analysis sections. The section results did not include sections going through the sewer. Slope Hazard Mapping The slope hazard mapping for Essex County that has been reproduced in the Langan Report identifies an area of risk on the slope. The risk is categorized as Landslide Case BIII, Weakly Cemented Rock and Soil (Hazus Number 3) Slope angle 10 to 15 degrees. The map legend indicates that the slope was determined by measuring spacing of 20 feet contours on the Caldwell Quadrangle Map. The slope angle on the upper slope, as determined by the spacing of contours created by aerial survey, is steeper than indicated by the contours and ranges from 17 to 29 degrees, which may require a re-evaluation of the Hazus Class by the Agency publishing the map. The range indicated by the spacing of the contours could put it into Class BV, Hazus No. 7. We were not able to obtain additional background information on the basis of the classification in time for this review. The analyses performed by both Langan and Princeton Hydro do not, in our opinion, indicate instability under the assumed conditions. SUBSURFACE INVESTIGATION REVIEW General Our review of the Slope Stability Investigations included review of reports and subsurface exploration logs and laboratory test result reports contained in the CME files for the Planning Board Application review. Langan performed explorations on the slope for the slope stability investigation being

ion logs and laboratory test result reports contained in the CME files for the Planning Board Application review. Langan performed explorations on the slope for the slope stability investigation being evaluated herein. Sor Engineering (“Sor”) performed a geotechnical evaluation for the site buildings including Building D near the ridge. In addition, they performed 3 additional investigations for analysis and design of stormwater management systems including Basins 10 and 11 on the western side of Building D. The layout of explorations is shown on the Langan Investigation Plan. A copy of this plan marked with our notes is contained in this report to assist the Board in understanding our descriptions.