February 26, 2025, Planning Board Special Meeting Transcript - WEHI

03/03/2025 06:36:47 AM Page 13 to 16 of 115 4 of 46 sheets 13 previous reports in 2021 you'll find that the seasonal1 high was done at a higher elevation.2 All right. Here at test pit number 10 the3 seasonal high water level is found three feet below4 grade, the surface elevation was 57 -- 573.5 Now, will you show us the other elevations?6 Q. Yes.7 A. This is the location of test pit number 10.8 This is the location of test pit number 10 and9 this is the location of porous pavement number 4. So10 you can see the close proximity to it, but they didn't11 make reference to it in their plans. I think it's12 something they missed, but let me scroll back down now.13 You see here the seasonal high water table based14 on test pit number 10 is in the storage area space, it's15 not down here at 567. Right now this storage basin16 isn't compliant. In fact right now this area here, it's17 called, Clean Storage Bed, this is where the porous18 pavement would hold and retain water. That's going to19 be filled up mostly with seasonal high water table, so20 it's not going to have the storage that the planners21 predicting. The basins going to overflow quicker. Peak22 flows going to come out quicker and it's going to be an23 issue.24 Now, I'd like to point out two more plans. Two25 14 more instances of this. Porous pavement number 6.1 Okay. Again, here they reference two test pits, test2 pits 42 and 43. But what they forgot to do again is3 look at the 2021 plan, it shows a different story.4 There's another test pit, test pit number 4, this shows5 the elevation much higher. Shows it about ten feet6 higher. Actually it's higher than the grade elevation7 they show. So let me --8 Which screen are you showing now?9 Q. Now I'm going to show the plan to show you the10 A. reference points of the test pits and then I'll show the11 soil borings to confirm the elevations.12 This is the location of test pit number 4. They13 referenced -- now, these are test pits 43 and 42. These14 are the ones they reference that show the seasonal high15 water table. The elevation here was 619, test pit16 number 4. Seasonal high water table was found -- sorry,17 got my notes a little confused. Oh no, sorry. I18 forgot, there's an error here on this report.19 Now, it doesn't say seasonal high water table in20 here but the seepage is at two feet. Seepage, that21 means the groundwater is leaking through the

I18 forgot, there's an error here on this report.19 Now, it doesn't say seasonal high water table in20 here but the seepage is at two feet. Seepage, that21 means the groundwater is leaking through the sidewalls22 of the test pit which means you hit the seasonal high23 water table.24 So I would like to revert back to this plan now.25 15 So here, which is a slightly different location1 than the other test pits, but the groundwater is only2 two feet below surface elevation, which is 608. I'll go3 back to show you where the seasonal high water table is.4 The grade elevation is at 50 -- they're calling it 508.5 This profile changes a bit, but right now the seasonal6 high is above the surface of the pavement. Again, the7 storage here in this parking lot is not going to be8 used. It's going to be taken up by the seasonal high9 water table, at least that's what we can tell from now.10 So, again, the basis are going be overwhelmed earlier11 than you think. It's not going to be able to12 infiltrate. Peak flows are going to increase.13 And this is the drawing, as it says on the14 Q. screen, for basin 6 out -- basin outlet structure number15 6, is that correct?16 Yes, it is. And this is where I want to point,17 A. again, on my earlier point, where these are seasonal18 high water elevations that we got from the presence of19 the water. It's not what the mottling was. So these20 elevations can be even slightly higher which would21 exacerbate the problem we've seen already.22 I have one more example here and then I'll move23 on. I'm going to go to basin number 9. All right.24 All right. Basin number 9 it says, seasonal high25 16 water table is at 548, we're at test pit number 6. And1 we're going to go to test pit number 6. This was2 actually 2004 test pits.3 Now, on this report it says the surface grade4 elevation was 574. The water level elevation, that's5 where they're saying they found seasonal high water, is6 eight feet below that, that's 568. The plan here claims7 that it's 20 feet lower than what's found in the grade.8 So once again the seasonal high water table is going to9 be much higher, it's going to fill up the storage area10 of this basin, it's not going hold any water, it's not11 going to detain, it's not going to be able to have peak12 flow elevations. It's going to increase flooding.13 These are three instances where we found that the14 seasonal high

ld any water, it's not11 going to detain, it's not going to be able to have peak12 flow elevations. It's going to increase flooding.13 These are three instances where we found that the14 seasonal high elevation -- seasonal high water table is15 higher in the documents than what they show on the plan.16 Since the plan, these designs aren't compliant they17 could risk increasing runoff and exacerbating flooding18 downstream.19 MR. AFRAN: I just want to note for the20 record, this diagram on the screen is Basin Outlet21 Structure Number 9.22 All right.23 A. Next thing I want to talk about is boring logs24 that, DEP in Chapter 5 of the BMP manual, which is the25