June 30, 2025, Planning Board Special Meeting Transcript - WEHI

7 of 70 sheets Page 25 to 28 of 175 08/07/2025 02:56:42 PM 25 to ask you to also describe what you're pointing at on1 the figure.2 THE WITNESS: Sure.3 MS. McGOVERN: Thank you.4 THE WITNESS: I'll describe it as this, so5 this is the area here. These two pink lines, A and B.6 These are the areas that we focused on initially and if7 you scroll up to the north. Up to here. These are the8 additional investigations that were done as part in May9 of this year.10 MS. McGOVERN: Those are C and D pink lines?11 THE WITNESS: Correct, C and D lines. This12 is Howell Drive over here. There's 13, 15 Howell. This13 is the entrance into the access road into the14 development, Building D, and we show our property and15 rock, some bolder's and some supplemental test pits.16 This is the majority of the work that was being17 described in this report.18 THE PUBLIC: How many borings did you do?19 THE WITNESS: There's four borings. Two on20 the C line, two on the B line -- D line, excuse me. And21 then there's an additional five test pits through here22 and there's additional test pits that were done a little23 further to the south.24 THE PUBLIC: How deep do you go?25 26 THE WITNESS: These vary, but the test pits1 were typically 5-feet or less. And the borings went2 variable depths, at least typically about 20-feet. We3 took them into the rock.4 THE PUBLIC: Can you just remind us, why did5 you have to go back or what was the indication to do6 more borings?7 THE WITNESS: Well, it was brought up during8 the, during the January 29 meeting, the question was9 raised about what about this area here, that there10 wasn't date that was further here that we were going to11 use for that, so we went back and did the additional12 investigation up in this area to the north.13 THE PUBLIC: And did you find any noticeable14 difference?15 THE WITNESS: Yes. One noticeable16 difference was that the rock was generally shallower to17 the north. So in this area here rock was about 10-feet18 deep, 10 or 12 and the same here. I think it was also19 10-feet here and dropped to about 20-feet over here.20 And then rock through this cross section A was a little21 bit deeper. So relatively thin as you went from, or22 shallow rather, as you went from north and south and I23 think, but the soils themselves were very -- showed very24 dense soil profile.25 27 THE PUBLIC: So overall what's your1 impression of what

or22 shallow rather, as you went from north and south and I23 think, but the soils themselves were very -- showed very24 dense soil profile.25 27 THE PUBLIC: So overall what's your1 impression of what your findings were from the borings?2 THE WITNESS: That this area up -- or this3 areas a very, it's a dense soil profile over hard rock.4 It's a condition that is favorable for slope stability5 and that the, our analysis indicated that slopes are6 stable now and would be after the development.7 THE PUBLIC: And how -- what's the depth of8 the bedrock?9 THE WITNESS: The bedrock vary from about10 10-feet here. You can see here -- well, this shows an11 elevation and a depth. That's the depth of rock that12 was encountered in the boring.13 THE PUBLIC: That's good.14 THE WITNESS: And then similarly, so there15 was rock around six and half feet shown here. I think16 that was -- it was probably broken rock and as we went17 further to the south, NLB-4, it was 12-feet and as you18 to scroll into this area here. It shows it was deeper19 than 11, but, again, it's weathered rock and broken20 profile below 11-feet.21 THE PUBLIC: So I am trying to understand,22 when you got bedrock you said 22-feet as you have there,23 that means the bedrock went down, your borings were24 22-feet, but how deep was the actual bedrock?25 28 THE WITNESS: So for example, right here1 this is telling us the depth of this boring, it is2 telling us the depth is below ground surface at which3 the top of rock is encountered. So 10-feet below ground4 surface we encountered rock.5 THE PUBLIC: So what constitutes the minimum6 requirements for a stable --7 THE WITNESS: Well, stability is a function8 of materials, strength of properties. So in rock like9 this it's very, we look at density of the soil, number10 one. Then we look at the rock properties, rock quality,11 strength of material and we enter those values into our12 model and that helps inform us of the overall stability13 of the material.14 THE PUBLIC: So the last question is15 regarding water flow, stormwater over bedrock down into16 that area. As a geologist, can you explain what your17 findings are to me as a layperson?18 THE WITNESS: Well, we found in our borings19 that we are not seeing groundwater, so when you look at,20 I will say from a precipitation event, there's an21 approximate peak or high point or elevation on this site22 that runs

und in our borings19 that we are not seeing groundwater, so when you look at,20 I will say from a precipitation event, there's an21 approximate peak or high point or elevation on this site22 that runs right about through this area. So everything23 to the right of that, any stormwater that hits will tend24 to flow overland in this direction and overland in this25