November 10, 2025 Planning Board Special Meeting - WEHI Transcript

01/05/2026 03:19:18 PM Page 21 to 24 of 112 6 of 28 sheets 21 do notice mottling, the mottling, the elevation that1 mottling occur's would define the groundwater level that2 would be assumed to be the seasonal high water table.3 CHAIRMAN BAGOFF: Would that be important to4 your calculations or your estimation of safety?5 THE WITNESS: That would -- you would6 ordinarily assume water levels that would be at the7 seasonal high water table in your stability analysis.8 Now, in their, in the contact with us after reading this9 report Langan indicates that they do have stability10 cases that address that. We haven't seen them yet.11 CHAIRMAN BAGOFF: So there's more things for12 you, there are more things for you to see to make a more13 accurate opinion, is that correct?14 THE WITNESS: That's correct.15 CHAIRMAN BAGOFF: Okay. Okay.16 Mayor McCartney.17 MAYOR McCARTNEY: Thank you, Mr. Kleinberg.18 THE WITNESS: Yes, ma'am.19 MAYOR McCARTNEY: Thank you. I do have20 questions, but first I want to say thank you for your21 analysis of this and in your delivery because I actually22 understood everything that you said. I do have23 questions, but it was explained very nicely. Thank you24 very much.25 22 Just go back to the beginning a little bit.1 Where you mentioned in the Langan report the bedrock or2 the basalt, that the sanitary sewer that runs between3 the basalt and the sandstone.4 THE WITNESS: I'm sorry.5 MAYOR McCARTNEY: That the sanitary sewer6 runs the between the basalt and sandstone.7 THE WITNESS: Oh, what I said is that it8 appears that there is a, what happens, what happened is9 it was originally only sandstone here and then Jurassic10 -- this volcanic material came through and pushed the11 sandstone apart, and so what we're looking at with the12 basalt is right where the basalt ended when the volcanic13 flow ended. So there's sandstone underneath it and if14 you go father to the west there would be sandstone over15 it and then you have this same cycle repeating in the --16 this is the second Watchung Mountain. At the first17 Watchung Mountain where there are some slope problems,18 that's a second intrusion of the basalt and then there's19 sandstone to the east of that.20 MAYOR McCARTNEY: It seems to me what you're21 saying they're avoiding basalt, so you would not want to22 disturb the basalt?23 THE WITNESS: What -- well, it may have been24 that sandstone is

f that.20 MAYOR McCARTNEY: It seems to me what you're21 saying they're avoiding basalt, so you would not want to22 disturb the basalt?23 THE WITNESS: What -- well, it may have been24 that sandstone is much easier to excavate than the25 23 basalt and that may have been the reason for the1 location of the easement at that location, but we didn't2 review the plans for the, the sewer, the existing sewer.3 MAYOR McCARTNEY: I had a question about,4 you referred to 1.7 as a safety and that would be5 adequate. So on the scale or rating where is 1.76 adequate?7 THE WITNESS: Okay. 1.7 is a result that8 Princeton Hydro, just to be clear, was a value for a9 slope failure surface that passed through the bedrock10 and then low value safety factor of 1.7. And the way11 the safety factor is defined, you have a, a lot of the12 failure surface is shown as a circle and so what the13 driving force is, is the weight inside the circle, the14 resisting forces, the sheer resistance along the15 circumference of the circle and so 1.7 means that the16 material has about 70 percent more strength than would17 be required to prevent, to just reach equilibrium at the18 slope. So that means that, and they used a very, a GSI,19 Geological Strength Index, that was very low. It's for20 a very poor, poor quality rock and even when they did21 that for that particular failure surface it still had 7022 percent more strength than was required. The convention23 as for -- well, I think it's even referred to in the24 Corps of Engineers Manual for ordinary slopes. In other25 24 words, where you're not putting a dam or a founding a1 large retaining wall on rock and that sort of thing, the2 convention is that 1.5 would be the safety factor. And3 those 50 percent more strength than you need.4 MAYOR McCARTNEY: So is more or less on5 that, if this is adequate what is --6 THE WITNESS: Well, Princeton Hydro referred7 to a statement in the Corps of Engineers Manual for8 rock, for structures constructed on rock and it also9 included recommendations for slopes and these are for10 things like, for Corps of Engineers projects would be11 large dams, military work and things, or things that if12 they failed could produce catastrophic results. And so13 a factor of 2 would definitely be justified in that14 case. But for this slope, and I would say if Building D15 was going to be built on the slope, then the, but

produce catastrophic results. And so13 a factor of 2 would definitely be justified in that14 case. But for this slope, and I would say if Building D15 was going to be built on the slope, then the, but it's16 not, but if it was getting built on the slope then maybe17 that kind of a safety factor would be required. But the18 construction here is just, just to the, the west of the19 crest of the ridge and they have demonstrated that the20 influences of the structure wouldn't extend onto the21 slope. And the safety, they computed safety factors22 with the building in place and, and compared it to23 safety factors under existing conditions and there24 wasn't much of a change due to influence of the25