November 10, 2025 Planning Board Special Meeting - WEHI Transcript

5 of 28 sheets Page 17 to 20 of 112 01/05/2026 03:19:18 PM 17 where the actual groundwater level is in the bedrock.1 There could, in this case, be at least two groundwater2 levels. There would be a groundwater level on the3 interior of the site where the wetlands exist currently4 and that could be due a first condition on the bedrock5 which is likely to be permeable. The sandstone, which6 underlies the soft bedrock at depth, have not been7 determined, that is considered an aquifer and so water8 does occur and it can move through it. So that, we9 think that the groundwater monitoring wells should be10 put there so that we could determine -- so the applicant11 could demonstrate that whatever mitigating measures are12 applied to the stormwater infiltration system, which we13 recommend that the applicants engineer address that as14 part of the approval process.15 And then the final grading should strictly be16 performed to ensure that the runoff is intercepted and17 prevented from running off over the slope.18 And that was pretty much a summary of what we are19 recommending that they, that, I don't know who's20 empowered to apply these requirements, but these are21 requirements that we think should be incorporated in the22 approvals.23 CHAIRMAN BAGOFF: Is there anything in the24 recommendation that should be done before the board25 18 continues its approval process?1 THE WITNESS: Well, I think the, the, the2 review of the infiltration basin concept and whether the3 mounding would effect, that should be done. It's4 possible -- it would be beneficial to install wells to5 actually determine what the groundwater level is. I6 would suggest maybe in the vicinity of Langan's borings,7 I think it's two and four, which are about -- they're8 two and four apparently appear to have been performed9 beyond the basalt formation and they're in the area that10 was identified in the hazard report that was produced by11 the --12 CHAIRMAN BAGOFF: So Princeton Hydro did13 four borings and they came up with mottling and Langan14 did 100 and came up with nothing. In your opinion --15 THE WITNESS: I'm not aware that Princeton16 did any borings.17 MS. McGOVERN: They were off-site.18 CHAIRMAN BAGOFF: They were off-site.19 Around the exterior of the site.20 THE WITNESS: Okay. I'm sorry, we didn't --21 I didn't pick that up in the report. If I missed it, we22 can go back and check that,

RMAN BAGOFF: They were off-site.19 Around the exterior of the site.20 THE WITNESS: Okay. I'm sorry, we didn't --21 I didn't pick that up in the report. If I missed it, we22 can go back and check that, but I didn't see any23 exploration actually done by them.24 CHAIRMAN BAGOFF: Is it possible to have an25 19 area like this where -- well, let me ask you a question.1 As an expert, do you think that there's groundwater2 infiltration in this area?3 THE WITNESS: I think there's some and4 whether it would develop a, it would be, develop a fully5 submerged condition so that pressures build up. The6 other problem you have with jointed bedrock is that the7 joints, for instance there's bedrock let's say at8 elevation 600 near the top of the slope or even higher,9 and sometimes in bedrock there will be faults or open10 joints and what happens if water opens -- enters the11 joint in a higher elevation and there's a continuous12 supply of water, that acts kind of as a short circuit13 down slope and so that, that joint fills up all the way14 down the slope and so a point down the slope is15 suddenly, or there would be a build up so that point16 down the slope is feeling a water pressure that could be17 equivalent to 20 or 30 feet of slope because of the18 amount of topography and that could be enough to19 initiate a slope failure problem and that's kind of20 things that do show up in heavy rainfall events.21 CHAIRMAN BAGOFF: Would you expect to see22 mottling somewhere in borings on this mountain?23 THE WITNESS: The, the report, if there was24 groundwater present it's likely that you would see, you25 20 would see mottling. Mottling. The, the -- Langan1 specifically states that they did not see, they looked2 for it and, they say they looked for it and they didn't3 see it. Both of their engineers used a, what's a4 general engineering color classification in their5 descriptions of conditions. Princeton Hydro indicates6 that the DEP regulations requires what's called a7 Munsell Color Chart, which involves, you have to take a8 really careful look at the colors and different shades9 mean different things in the mottling. The rocks don't10 indicate that any of that was noted and I think it's11 Langan's contention that it wasn't present.12 CHAIRMAN BAGOFF: Is mottling important to13 know if you're building a site?14 THE WITNESS: Mottling is a phenomenon that15 occur's where there

hink it's11 Langan's contention that it wasn't present.12 CHAIRMAN BAGOFF: Is mottling important to13 know if you're building a site?14 THE WITNESS: Mottling is a phenomenon that15 occur's where there is a persistent water level and16 usually the water level varies over the season and it17 rises -- it's usually the water levels are a maximum18 around the end of March and April, because the trees are19 still dormant or about to be, about to start drawing20 water. But before they enter that state there's nothing21 drawing ground water out of the ground because the22 vegetation is not active and so that represents the23 highest water level that would occur in the year and so24 if you're doing test pits in any specific time and you25