O38 Email from Nov 13 2025 to Dec 9 2025 between Mr Kleinberg and Mr Seele

From: irk Seel To: Kleinberg, Sam; pandersonpe@gmail.com ce: Maciel, Ryan; Rizzo, Jordan; Hernéndez, Nelson; Mazier, Aleiandra OS ¥ Subject: RE: WEHI Date: Tuesday, December 9, 2025 4:52:02 PM oe Attachments: Ref Miao 2025.df af ns 2006.pdf This Message is from an external sender. Sam, our responses are provided in red italic font below: 1. A basis or reference should be provided for the selection of c=100 psf. For example see attached ref from “Biotechnical Slope Protection and Erosion Control” The values selected should be based on a representative estimate of the root area ratio. The use of RAR is considered a specialized analytical technique not a universal standard of practice in typical New Jersey geotechnical engineering design. You'll recall that Langan evaluated a higher water table, which in our opinion was a worst-case condition considering there is no groundwater, and the design case you've asked us to consider seems unlikely as you testified to last week that this analysis represents a condition that is extraordinarily unlikely to occur or be problematic. The references on the subject typically relate to tree species and steep slopes in the western US/Canada/Mexico and overseas in China, New Zealand, etc. where steep slopes are generally more susceptible to failure, not specifically to conditions in the eastern US. The slopes east of Building D are generally not steep. References are attached. Miao, et al 2025 indicates trees at least 20 feet in height and 30 years of age have at least 7.5 kPa (156 psf) apparent root cohesion, and larger older trees upwards of 10 kPa (208 psf). Stevens, et al, 2006 indicates natural forests and lab analysis have apparent root cohesion of at least 25 kPa (522 psf) and 4.9 kPa (100 psf), respectively. The site has a very mature older growth woodland setting. Based on these technical references, an effective root cohesion of more than 150 psf is substantiated. See our response to #3 below for more discussion. 2. The FS decreases quickly with depth. The analysis should, in our opinion be extended to at least 3 feet depth. Infinite slope stability assumes a uniform slope and homogeneous soil conditions. Only the upper 2 feet of soil is homogeneous. Below the topsoil is predominantly dense sand and gravel (having significantly higher shear strength than the topsoil). Evaluating the upper 3 feet, in our

nly the upper 2 feet of soil is homogeneous. Below the topsoil is predominantly dense sand and gravel (having significantly higher shear strength than the topsoil). Evaluating the upper 3 feet, in our opinion, no longer represents a homogeneous soil profile; thus, further reducing the applicability of this analysis. 3. Based on our initial review safety factors of 1.2 would be appropriate for an extreme event. Lowering the effective root cohesion to 50 psf (which approximates effective root cohesion from grassland per the references), reduces the lowest FS (at only one location) to 1.2. As noted in response to #1 above, the literature substantiates higher effective root cohesion than the 100 psf we used. By further reducing the effective root cohesion to 50 psf, the value is approaching the cohesion of a saturated inorganic silt, which is what the topsoil is, and hence, 50 psf in our opinion is