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

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

5 of 46 sheets Page 17 to 20 of 115 03/03/2025 06:36:47 AM 17 guide they provide to engineers to design stormwater1 structures according to the standards. They have rules2 about how many test pits you're supposed to dig for3 every basin or underground structure you're going to4 build. It's mostly based on size of the structure. So5 you have minimal of two and then the larger the6 structure gets the more they want you to dig test pits7 for. As you can see in the first example I gave with8 porous pavement number 4 there could be a lot of9 variation. Lots of different test pits to make sure you10 capture the entire picture. You're not missing11 anything.12 We did note that not all of the -- not all the13 test pits were dug for all areas. For instance five,14 six, eight, nine and ten there were test pits for it but15 then 7 they should've dug three test pits, they only dug16 one, that isn't compliant. And then you're thinking17 Sean Walsh is being a stickler, there's only one, but18 again porous pavement number 4 there can be a lot of19 variations. Some of these are very large basins. It's20 important to be able to capture the entire story of21 what's going on underneath the ground for these basins22 so you don't have a mistake and you don't -- you make23 sure you have the capacity that you're designing for.24 So that actually notes that six of the 12 basins25 18 do not have the sufficient number of test pits they're1 supposed to have.2 All right. Next I would like to talk about3 groundwater mounding. Groundwater mounding is the4 process of, you'll have the seasonal high water table on5 this level here. During a rain event -- I'm sorry, I'm6 pointing using my hands. It's on a level, right. It7 rains, when you have a concentrated area of infiltration8 like a basin, it will mound a little bit. It's a normal9 process, the DEP has a form and it's a calculation you10 have to fill out to make sure that the mound doesn't get11 to far or perhaps get into someone's basement, I'm sure12 everyone's familiar with that, when it rains the mound13 rises. So they make you -- they provide a form, you14 have to fill it out and demonstrate that you're not15 mounding anywhere to cause any issues. Now, typically16 you have to do this for the water quality storm and, you17 know, the applicant provided all the forms for that and18 it was compliant. But what the applicant does with

use any issues. Now, typically16 you have to do this for the water quality storm and, you17 know, the applicant provided all the forms for that and18 it was compliant. But what the applicant does with some19 of these basins is they use infiltration as a way to20 keep the flow -- reducing the peak flow runoff rate. So21 that's, they're not just passing the water through pipe,22 they're pushing the water through the ground. So in23 those situations you also have to do groundwater24 mounding for a 100 year storm. The DEP wants to see not25 19 just a small storm but they want to see what happens1 during the larger storms. To give you guys a2 perspective, the water quality storm is about an inch3 and a quarter. The ten-year storm -- sorry. The4 100-year storm is eight inches of rain. So it's a much5 more significant amount of rainfall, so mounding can be6 significantly different.7 All right. One other section, porous pavement 38 from the applicants design plan.9 For the record, this is a diagram headed, Basin10 Q. Outlet Structure Number 3.11 It's a profile section of porous pavement number12 A. 3, sorry. So it's a cross section or a profile of the13 porous pavement system.14 So when you have a history of pavement or porous15 core stone, you have stone storage and now your soil16 replacement permeability and that soil replacement17 permeability ends at the seasonal high water table, what18 happens --19 When you say, ends, do you mean the bottom line20 Q. of the soil section or the top line?21 The bottom. The bottom of the soil replacement22 A. ends at the elevation of the seasonal high water table.23 Thank you.24 Q. Okay.25 A. 20 So what they did here was, when they did the soil1 borings they did all the soil tests, they measured2 infiltration rates as well, because they needed to know3 how quickly the water would go into the ground. And4 what they found was that this ground doesn't have great5 infiltration rates, which is not unusual or unexpected6 for this area. So what they chose to do is they chose7 to replace that soil. They dig deeper in the bottom of8 the basin and replace that soil with sand material9 that's a much higher infiltration rate. Allows the10 basin to go, to go down quicker and get rid of the water11 quality storm. Here's the problem, it wasn't the water12 quality storm, and that's why mounding is fine if you13 didn't have any issues, but the

in to go, to go down quicker and get rid of the water11 quality storm. Here's the problem, it wasn't the water12 quality storm, and that's why mounding is fine if you13 didn't have any issues, but the issue here is -- so the14 sand here you can see it says eight-inches per hour15 infiltration rate, which is fantastic. But when you get16 down to this soil that's when the soil infiltration rate17 becomes 0.25 inches per hour. This is effectively a18 wall. So what you need to demonstrate is that when19 you're infiltrating the 100-year storm you need to show20 whatever you're promising to infiltrate you can hold21 that water in here. That you don't have any, the22 groundwater mounding is not supposed to go into your23 storage. It's supposed to get down and not interfere24 with the storage of your basins.25

03/03/2025 06:36:47 AM Page 21 to 24 of 115 6 of 46 sheets 21 So you're probably asking yourself, how do you do1 that. What you do is you go to the modeling. We look2 at their model, we decide -- they show how much water3 they're going to infiltrate during the 100-year storm.4 So let me go to the model for one moment.5 At this point the model as in M-O-D-E-L?6 Q. Yeah, the stormwater model, M-O-D-E-L.7 A. Okay. Right now we're looking at the stormwater8 report provided by the applicant. This is for basin9 number 3, that's what they call porous pavement section10 number 3. It's essentially an underground stormwater11 basin. You'll see here, this is kind of a -- they use12 the modeling software HydroCAD, which is a summary of13 different volumes. Discarded section is the14 infiltration. It's discarded because it doesn't go into15 any of the pipes. It just kind of goes away. It16 disappears. Right. So they say that during the17 100-year storm, which is shown right here, they're going18 to infiltrate 10,971 cubic feet of water. So now, we19 have to translate that into a height, we're looking at a20 profile and right then on the same page they give the21 surface area of the basin, which is 5,227. So if you22 divide the 10,000 number by the 2 -- by the 5,00023 number, you roughly get two feet of water. So that24 means you're going to have two feet of standing water in25 22 that basin that they got to hold before the storage.1 Let me go back to the plan.2 Now, I'm going to go back to the plan. So now3 what you're thinking is, all right, so tell me, talk4 about how long. Right. Here it says two feet, no5 problem. That's two feet full of sand. We're talking6 about two feet vertical of just plain vertical water.7 So you have to fit the water with the sand. Sand8 significantly has what we call a void ratio of 0.4.9 Which means if you have one cubic foot of sand, 4010 percent of it is empty space. So you would take that11 two feet of water and you would divide it by 0.4, and12 that's how high -- that's the height you would have of13 water with sand.14 All right. When you divide two -- it's 2.1, when15 you divide 2.1 by 0.4 you have 5.25 feet of water. And16 at this point it's going to exceed the height of17 pavement. Again, the water's being held, the water's18 going to be trapped by this slow infiltrate soil, it's19 going to build up in the sand, it's going to exceed

it's going to exceed the height of17 pavement. Again, the water's being held, the water's18 going to be trapped by this slow infiltrate soil, it's19 going to build up in the sand, it's going to exceed the20 sand depth, it's going to fill up the void space in the21 storage area, more water's going to go through the pipe.22 The amount of peak flow rates they show in the models23 aren't correct. It's going to capture, the storage is24 going to -- sorry, the runoff is going to go more25 23 through the pipes and it's going to run into this wall.1 What happens it when goes through the pipes?2 Q. When it goes through the pipes the peak flow rate3 A. they report in the model is inaccurate, it's under.4 It's going to be higher, which means that they have5 limitations on how high they can make the peak flow6 runoff for this developed site. It's supposed to be7 less than what exists and right now for this situation8 it's going to be higher for the larger storms.9 Now, we saw -- now, I used porous pavement10 section number 3, we saw the same instance in porous11 pavement number 4, 5, 6, basin 7, 8, 9 and basin 10. So12 now, I'm not going to through all these because I13 respect your time, but I want to detail an example. It14 wasn't always this extreme but in those basins the15 stormwater, it's going to affect the peak flow runoff16 rate, which is really crucial because we do have17 flooding downstream and we have to meet certain peak18 flow rate reductions and what they are reporting is not19 going to happen in reality. These basins are going to20 be strained by the storage from too much flow, too much21 runoff being trapped and we're going to have higher peak22 flow rates.23 What does that translate to in terms of practical24 Q. counts?25 24 It means that the water's not going to infiltrate1 A. like the model says. It means more water in the pipes,2 more water going downstream and you can potentially3 increase the water coming off the site and reduce it,4 which you're supposed be doing according to the5 standards and if you increase the runoff you can get6 flooding, or you can get more flooding.7 All right. I would like to, now that we propose8 a new high water table, I would like to take a moment to9 talk about runoff in general.10 Let me just identify the screen, if I can.11 Q. CHAIRMAN BAGOFF: One second, I'm sorry.12 Let it be noted Mr. Cardoza joined the planning

ould like to take a moment to9 talk about runoff in general.10 Let me just identify the screen, if I can.11 Q. CHAIRMAN BAGOFF: One second, I'm sorry.12 Let it be noted Mr. Cardoza joined the planning board.13 Thank you.14 MR. AFRAN: It says on the bottom, Figure 1,15 Proposed Grading Plan. And then it has additional16 words, With blue arrows showing the existing drainage17 path and the red arrows showing the proposed drainage18 path and how the runoff is being diverted from the19 wetlands. I'm just reciting that so we have a reference20 point.21 This figure is from the letter we submitted to22 A. the DEP based on our review of the applicants23 submission.24 MS. MCGOVERN: O-5, that we marked November25

7 of 46 sheets Page 25 to 28 of 115 03/03/2025 06:36:47 AM 25 15, 2024?1 MR. AFRAN: Yes.2 THE WITNESS: Yes.3 All right. So what I did here was I took a plan4 A. that the applicant provided and I superimposed some5 arrows to give some direction here. So I want to talk6 about how the wetlands are going to be affected by this7 development. The blue arrows show the direction of8 runoff in the existing condition, so they basically9 travel perpendicular to the contour lines. You can see10 the runoff up here contributes to the wetlands up here11 and so forth. Runoff that runs here runs parallel and12 it feeds a continuos line of wetlands right here. Same13 with over here and over here. They're rerouting -- the14 runoff is spread equally.15 Now --16 Are these -- let me ask you one question.17 Q. The blue arrows, are they reflecting present18 conditions on the site before the development?19 Yes, they're showing present conditions of the20 A. site.21 So now what else is on here is the red arrows.22 The red arrows show how the water that lands on the23 developed area will be rerouted due to the stormwater24 system. So for example, in this section here in the25 26 existing condition the blue point this way. Now the red1 arrows point towards the street. The stormwater runoff2 would be captured by the parking lot, put into the3 stormwater pipes, it will travel down the road and it4 will go into these basins. Same with over here and same5 with over here. So instead of equally distributing the6 runoff to the entire wetlands a large portion -- a7 portion of land runoff that used to go here now is going8 to be rerouted. It's going to avoid these upper9 wetlands and go into this basin and get discharged down10 here. So the drainage for these basins are going -- the11 drainage area for these wetlands are going to change due12 to the development.13 Now, you just referred to the upper wetlands.14 Q. You are referring to the left side of the diagram. Is15 it fair to say that the same would apply to the wetlands16 in the center and on the right side of the diagram?17 Yes, that's true.18 A. Thank you.19 Q. All right. So this is an existing drainage area20 A. map that the applicant provided with their submission.21 What I did is I superimposed rough drainage areas for22 the wetlands and for this point of discharge. It is the23 printout used in their models and I'm trying

plicant provided with their submission.21 What I did is I superimposed rough drainage areas for22 the wetlands and for this point of discharge. It is the23 printout used in their models and I'm trying to24 demonstrate the drainage area that feeds the wetlands25 27 through these area.1 For the record, the area to the left is a dark2 Q. green color, the area to the right is a light green3 color. And obviously if anyone sees the black and white4 version and wanted to define the two color sections.5 This is a newer document with Mr. Walsh's color6 additions superimposed on the document already in the7 record. So some point we should mark this as an8 objectors exhibit, I believe.9 MS. MCGOVERN: We don't have that yet?10 MR. AFRAN: No, we'll have to supply that.11 MS. MCGOVERN: All right. So let's see, we12 are going to call that one O-8, because we already got13 some exhibits from you earlier today. The Princeton14 Hydro report is O-5. CD from his computer is O-6 and15 the color diagram that you sent was O-7. So this will16 be O-8 and we'll call this colorized --17 MR. AFRAN: I suggest we might call it --18 MS. McGOVERN: DA-1.19 MR. AFRAN: Yeah. DA-1. Colorized DA-1.20 MS. MCGOVERN: All right.21 MR. PLOCKER: Could we just make it clear22 for the record, I know you say DA-1, but this is23 something that my client submitted. Could we just get24 clear for the record that this is something that was25 28 colorized by the objectors witness and if we could get a1 date. I just want to make clear for the record that2 this originally was our document.3 MS. MCGOVERN: All right. This is what4 we're going to call it, colorized DA-1 from objector.5 MR. AFRAN: We agree the original document6 was submitted by the applicant.7 MS. MCGOVERN: The colorized version?8 MR. AFRAN: Colorized version --9 MS. MCGOVERN: Yeah. Okay. So DA-1,10 colorized version by the objector.11 MR. AFRAN: Yes.12 MR. KLEIN: Didn't change the shape and size13 of the areas, just colored them in, is that correct?14 THE WITNESS: No, I drew the drainage area15 with the wetlands there. So I drew in that green. I16 didn't colorize it. I used the contours that he had and17 those green areas are drawn by me. Sorry for the18 confusion.19 MR. KLEIN: What was it before you drew that20 on there? What was that drawing.21 MR. AFRAN: It was -- DA-1 as was submitted22 by the applicant. What Mr. Walsh has done is he

rry for the18 confusion.19 MR. KLEIN: What was it before you drew that20 on there? What was that drawing.21 MR. AFRAN: It was -- DA-1 as was submitted22 by the applicant. What Mr. Walsh has done is he used23 the contour lines on the original exhibit to demonstrate24 two drainage areas on the existing site, as shown as25