O17 West_Essex_Highlands_Geotech_Slope_Stability_Review_20250716

Dr. Robert Bagoff, Chair July 16, 2025 West Orange Township Planning Board West Orange Township 66 Main Street West Orange, NJ 07052 RE: Review of Langan Slope Stability Analysis, January 14, 2025, revised June 18, 2025 PB-24-01 West Essex Highlands, Inc Block: 179 Lot: 32 Zone: IH-1 Warner Road Project 2151.002 Dear Chair Bagoff, I have been tasked with reviewing the above referenced executive summary and letter report and the basis of analysis prepared by Langan, dated January 14, 2025, last revised June 18, 2025. As will be discussed, the slope stability analysis is flawed, specifically not reflecting the actual conditions on the eastern slope of the site. In fact, the analysis picked the data obtained from the soil borings with the most competent parameters, when, in fact, the areas most vulnerable to initiating slope failure, the toe or bottom of the steep slope, especially in the northern area of the slopes analyzed found rock quality as “very poor”1. This review is focused on this eastern area of the site, the location of proposed Building “D”. Building Layout Currently Proposed Closer to Slope than Concept As we understand, the Settlement of Litigation Agreement (Settlement Agreement), signed by Mark Hoffman on April 23, 2020, an application before the Planning Board must be developed “…consistent with the ‘West Essex Highlands Concept Plan 16 for West Essex Highlands, Block 179, Lot 32, Township of West Orange, Essex County, New Jersey’ dated March 3, 2020 prepared by Anderson Consulting Services, LLC (the ‘Concept Plan’)”2. A review of the building layout provided as Figure 1 in the Langan report reveals that Proposed Building ‘D’ is 50 feet closer (east) to the slope, and atop the knob on the eastern end of the building and over 30 feet closer (east) to the slope on the western end of the building; in addition to the change in building layout. The relocation of this building adds additional risk to the stability of the slope in question. Parameters of Slope Stability Analysis Do Not Match Actual Conditions We reviewed the approach and parameters to the slope stability analysis and found significant inconsistencies with the data obtained in the field, as well as mapped geologic conditions. As illustrated in the table below, the borings identified in red were the ones chosen to include as the chosen parameters, with 67% RQD chosen to develop the

ld, as well as mapped geologic conditions. As illustrated in the table below, the borings identified in red were the ones chosen to include as the chosen parameters, with 67% RQD chosen to develop the strength of the overall rock. 1 An actual designation of the quality of bedrock as defined by ASTM D603 and US Army Corps of Engineers Engineering Manual, EM-1110-1-1804. 2 Page 2 of the Settlement Agreement.