O21 West Essex Highlands Geotech Slope Stability Model Memo 20250812pdf

Princeton Hydro, LLC Page | 6 It is my professional opinion that the proximity of the residential properties in the northeastern area of the site, in particular, along Howell Drive to the toe of the slope represents a severe consequence of failure as it relates to bodily harm and property loss. Limited laboratory testing was performed on the encountered rock at the site, with no rock testing performed on the rock at the northeast area of the site. As I previously testified, the stability model omitted representation of the Feltville Formation, related concerns about weathering that may occur between rock contacts, and the impact of the buried sanitary sewer utility along the toe of the slope. Due to the uncertainties regarding the subsurface conditions and their corresponding design parameters, the higher factor of safety should be evaluated for the project site. In conclusion, the uncertainty associated with the subsurface conditions of the less competent Feltville Formation downslope of the proposed Building yields considerable hesitation to the assertion that construction will not affect the short- or long-term stability of the slope. Variation of a single design parameter, GSI, which is estimated by visual assessment by Langan of isolated rock outcrops, caused significant variation in the model results. I will be available at a scheduled Planning Board meeting to discuss my observations and conclusions. Thank you. Sincerely, Geoffrey M. Goll, P.E. President Princeton Hydro, LLC cc: WeCare