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

08/07/2025 02:56:42 PM Page 29 to 32 of 175 8 of 70 sheets 29 direction from that high point. Not all that water for1 instance seeps into the ground. Some runs over2 naturally and is collected in a storm system. Some of3 it may seep into the ground, may or may not form much of4 a groundwater table only to the fact there's a5 relatively small area between the high point and this6 area here which water can be concentrated in the form of7 groundwater table.8 THE PUBLIC: Okay. Thank you.9 CHAIRMAN BAGOFF: Okay.10 Please state your name for the record?11 THE PUBLIC: Good evening. Seth Weisleder.12 Good evening, Mr. Seel. I have a question13 to just maybe refresh, I guess, everyone's memory from14 back in January. It's a long time ago, more like15 yesterday. But what was the main purpose for checking16 the stability of the slopes that we see where all the17 borings were done? What was like the main purpose of18 it.19 THE WITNESS: The purpose of a stability20 assessment is to determine whether or not the slope is21 currently stable and whether it would be stable after,22 certainly, construction activity.23 THE PUBLIC: Okay.24 Can you go more into that construction25 30 activity, would that include blasting?1 THE WITNESS: Well, it would be, it's really2 not so much about blasting, it's really mostly3 construction. So we look at the loading from the4 building, is what we look at. So we got a slope that we5 look at, then we ask them to redraw the lines to6 determine where the building is going to be going to7 load this slope and we enter that and put that8 information into a model.9 THE PUBLIC: Okay.10 That could include blasting, correct?11 MR. PLOCKER: I believe Mr. Seel testified12 extensively to blasting the last time when questions13 were brought up. It is in the transcript and it's not14 part of this report.15 THE PUBLIC: He said construction activity,16 I want to clarify specifically what construction17 activities, and does that include blasting.18 THE WITNESS: Well, let me rephrase it then.19 The stability analysis is run based on the existing20 conditions and then if conditions change during21 construction. So it's not the activity of construction,22 it is whether changing or adding -- adding grading or23 you're adding filling or cutting slopes and you're24 adding load to it. That's what --25 31 THE PUBLIC: And based on the new ones that1 you found, what kind

r changing or adding -- adding grading or23 you're adding filling or cutting slopes and you're24 adding load to it. That's what --25 31 THE PUBLIC: And based on the new ones that1 you found, what kind of rock was that? What kind of2 soil, I think there was some more specifics in your3 report.4 THE WITNESS: Yeah, the report described5 soils that were encountered, very similar to what was6 found elsewhere on-site which generally speaking is very7 dense soil, combination of sand, silt and gravel. Some8 varying amounts of clay. And the rock itself is a fine,9 relatively fine-grained igneous rock that tends to be10 very hard and ashy.11 THE PUBLIC: So could there possibly be risk12 in the surrounding area because basalt is dense and13 transmits energy efficiently like shock waves and14 blasting, couldn't that travel further based on what the15 basalt is?16 THE WITNESS: I'm sorry, when you're17 referring, specifically to an activity?18 THE PUBLIC: Since there will be some19 blasting for Building D does the rock basalt, that is a20 dense rock, correct?21 THE WITNESS: Yes, it is.22 THE PUBLIC: And it transmits energy23 efficiently, so couldn't those shock waves from the24 blasting travel further?25 32 THE WITNESS: So blasting is a science that1 is a little, it's very complex. So, yes, it is. I2 testified in the past that if they do excavate here due3 to rock issues, there's controlled blasting techniques4 to minimize the amount of energy that is transferred to5 the rock capacity and beyond the property. And when we6 do that, if it's done properly, like blasting rock7 immediately adjacent to a four story buildings without8 incident.9 THE PUBLIC: So could there be potential10 slope destabilization if blasting from, especially atop11 Preakness Basalt that kind of rock? I mean, we're12 talking about a specific kind of rock which you're13 familiar with, couldn't there be potential14 destabilization on that slope?15 THE WITNESS: I've not encountered that16 rock. This type of rock is very hard. It has a17 relatively high sheer weight and these types of, if18 they're blasting for example, those waves pass very19 quickly through the rock and it's when they slow down20 and hit material that's much softer that the material21 could tend to disturb ground. It's less likely in very22 hard rock like this. Especially unlikely in the event23 that these controlled blasting techniques

terial that's much softer that the material21 could tend to disturb ground. It's less likely in very22 hard rock like this. Especially unlikely in the event23 that these controlled blasting techniques are put into24 place.25