O30 Princeton Hydro Report Dated 9 3 25

West Essex Highlands Review West Orange, NJ Permit No, 722-04-0001.1 LUP230001 April 2025 BMP 6 shows a SHWT of 598 using the 2024 soil testing data but the 2021 testing data shows a different story. In 2021, TP 4 shows seepage at 608 which is 10 feet higher than what the plans show. Based on this finding, the porous pavement design is not compliant. The SHWT (which in this case was direct seepage) is within the storage volume of the basin see Figure 1. BMP 4 shows a SHWT of 567 (Figure 2) on the plans but that is only using data from the soil tests taken in 2024 (Test Pit 28). In 2021, soil tests were also taken, and TP 10 (Figure 5) is very close to BMP4. TP 10 shows a SHWT of 573 (Figure 2) six feet higher than TP 28 which would result in the groundwater level being within the storage bed of the BMP, which clearly does not comply with the two-foot minimum separation and would result in a non-functional BMP. There is also an error on the TP- 10 soil profile. On the right-hand side of the document, there is an entry for the water level found; however it is left blank. Elsewhere on the same test pit log it states that seepage was found at 3 feet below grade which is an elevation of 573 (576-3 = 573). Groundwater seepage is water leaking through the side walls of the soil profile, the seepage is an indicator of the SHWT and it should have been marked that way. ° BMP 4 (Porous Pavement) e BMP 9 (Aboveground basin) Finally, there is an error with BMP 9. The construction detail states that TP 46 has a SHWT at 548 but the soil profile states the ground surface elevation is 574 and the depth to SHWT is 8 feet which results in an elevation of SHWT at 566. Elevation 566 is much higher than 548 and would require the design to be significantly altered if the design were to comply with the stormwater regulations. See Figure 3 below for the necessary references to the plans and soil profiles. These findings show that BMPs 4, 6 and 9 are not compliant with NJDEP. The SHWT is too high and would occupy a portion of the storage volume of each of the BMPs. This would result in less groundwater recharge than calculated in the stormwater report and higher peak flow rates from each BMP. The BMPs need to be revised. These revisions could require the BMPs to be widened, shortened or relocated in general. The bottom of the BMPs need to be maintained at the minimum of two feet

each BMP. The BMPs need to be revised. These revisions could require the BMPs to be widened, shortened or relocated in general. The bottom of the BMPs need to be maintained at the minimum of two feet above the SHWT to meet the requirements. This is another way that the design is not demonstrating compliance with N.J.A.C. 7:8 5.4 (Local Ordinance 25-29.4 P) 7:8 5.6 (Local Ordinance 25-29.4 R). Princeton Hydro, LLC Page | 7

West Essex Highlands Review West Orange, NJ Permit No. 722-04-0001.1 LUP230001 April 2025 SOR CONSULTING TEST PIT LOG TEST ENGINEERS, INC. PIT NO. TP-4 CLIENT Garden Homes GSE 510 WATER LEVEL PROJECT — Proposed Rendenta Development DATE TET TOEATION West Orange, New Jey BNO, FE REPORTRO—21-6-12 be tad DENSITY MOISTURE DESCRIPTION REMARKS: TosssiWveaetaion 1 ‘Soft Moist ‘Brown coarse to fine Sand, some Sit lttie coarse to fine Gravel “Water seepage 2 2 Becrock@2 Tesi Pa Compieed 87" Figure 1: Cross Section of PP6, Proximity of TP-4 to PP6 and TP-4 Soil Profile. Page | 8 Princeton Hydro, LLC

West Essex Highlands Review West Orange, NJ Permit No. 722-04-0001.1 LUP230001 April 2025 s7382 10% 1p 28 SCALE NTS ° SOR CONSULTING TEST PIT LOG TEST ENGINEERS, INC. PIT NO. TP-10 CLIENT Garden Homes GSE +578) WATER LEVEL PROJECT Proposed Residential Development DATE, EPEYIH TOCATION West Orange, New Jersey JOBNO 2CoT REPORTNO.__21-C-12 b=] DENSITY | MOISTURE DESCRIPTION REMARKS: ToasoWVeaetation 12° 1 = | Medium Moist Brown coarse io fng Sand, sore Sit, some coarse 0 fine Grave 2 Dense ‘occasional cobbles/boule 3 “Water seepage at 3-0" Figure 2: Cross Section of PP4 from Construction Plans, Proximity of TP-10 to PP4, TP-10 Soil Profile Princeton Hydro, LLC Page | 9

West Essex Highlands Review West Orange, NJ Permit No. 722-04-0001.1 LUP230001 April 2025 eu te S= 10% ‘TG:568.2 OUTLET STRUCTURE (#9) 4. WEIR: 564.0, 3” ORIFICE: 563.0 INV(12" IN}: 562.8 4NV(15" IN): 556,0 555.25 ‘ -109/ SAN-MH3 ~ /RIM:566.76 INV. IN: 564.90 INYOUT: 564.80 15 Le 15" SOLID HDPE —~~ 7" artnet S$=3.1% Ser eens INV: 562.0 STORAGE & OUTLET #9 SECTION VIEW ALF 12" POROUS HOPE ——_ MS S=0% SOR CONSULTING TEST PIT LOG TESTPITNO. TP-46 ENGINEERS, INC. CLIENT = Garden Homes/ West Essex Highlands, Inc. [GSE TERLEVEL PROJECT ‘Stormwater Management System [DATE LOCATION = ‘West Orange, New Jersey |JOB NO. 245-02 [REPORT NO. FET DEPTH pensity | MOISTURE GROUND SURFACE, REMARKS. : [TopsoilVVegetation 1 13 Soft Moist 2 |Gray to Reddish Brown Ciayey Silt, little coarse to fine Sand, little coarse to fine Gravel (Ciay Loam) : 2.5" Light Brown Clayey Silt, little coarse to fine Sand, kluittle coarse to fine Gravel 4 |(Ciay Loam) “01 5 ‘Stiff Reddish Brown coarse to fine Sand, some Silt, and medium to fine Gravel (Sandy Loam) ‘ Permeabiity @ 8° K=0.99 rv (K2) Figure 3: Cross section at PP9, Location of TP-46, TP-46 Soil Profile. 2.3 SOIL TESTING REQUIREMENTS FOR BMPS The New Jersey BMP Manual provides guidance on how many test pits are required based on the size of the basin in Subsection 2a of Chapter 12. The soil testing allows a designer to understand how the soil will respond to rainfall, including the elevation of the SHWT and a Princeton Hydro, LLC Page | 10

West Essex Highlands Review West Orange, NJ Permit No. 722-04-0001.1 LUP230001 April 2025 measurement of the hydraulic conductivity of the soil at the elevation where infiltration is proposed. It is a crucial part of the design process. Typically, each BMP is required to have two test pits but more can be required based on the size of the proposed BMP. The SHWT can vary based on its location and it is important to take measurements at different locations to better understand that variation. If an insufficient number of soil tests are taken, the engineer runs the risk of not understanding the elevation of the SHWT across the BMP and could design a BMP that does not have the required separation from the SHWT. A good example of this is PP4 and PPé. If you choose to review only portions of the test pit data the BMP seems properly designed but when you review the data in its entirety, including the 2021 data, you can see how the SHWT varies by location and the design needs to be modified to accommodate the variation. Princeton Hydro compared the infiltration area of each BMP on the plan to what was entered into the stormwater calculations model. Table 1 is a comparison of the infiltration area found in the model calculations and the infiltration area shown on the plan. The infiltration area is the bottom of the basin, not the side slopes. Table 1 Comparison of Infiltration Areas shown in the Plan and Stormwater Calculations Model. BMP ID- BMP Type Model Infiltration Area Plan Infiltration Area Difference, Model — Plan (SF) (SF) (SF) 1 - Large Scale Infiltration 42,000 45,490 -3,490 Basin 2 - Small Scale Infiltration 26,023 25,830 193 Basin 3— Porous Pavement 5,227 5,558 -331 4— Porous Pavement 12,197 12,369 -172 5— Porous Pavement 14,810 14,611 199} 6— Porous Pavement 35,719 37,473 -1,754 7 - Small Scale Infiltration 14,375 13,405 970 Basin 8 — Porous Pavement 10,019 15,900 -5,881 9 — Porous Pavement 6,534 17,981 -11,447 10 — Small Scale Infiltration 9,583 9,467 116 Basin 11 = Porous Pavement 13,504 22,826 9,322 12 — Small Scale Infiltration 900 1,004 -104 Basin There are differences between what was modeled and what was shown on the plan. Many of these differences are not consequential but the differences at BMP 1, 8, 9 and 11 are especially significant and the model should match what is shown on the plan. Princeton Hydro, LLC Page | 11

West Essex Highlands Review West Orange, NJ Permit No. 722-04-0001.1 LUP230001 April 2025 Princeton Hydro compared the number of test pits for each BMP to the number required by the New Jersey BMP Manual to confirm if the applicant performed the required minimum number of soil tests for each BMP as is shown below in Table 2. Due to the discrepancy outlined above with respect to the BMP areas, Princeton Hydro used the area shown on the plan for the completion of the table below. Table 2: Number of Soil Tests Performed for each BMP against the Minimum Number Required. BMP ID Infiltration Area (SF) Plan | Number of Tests Number of Test Compliant Provided Required Plan (Y/N) 1 45,490 5 8 Y 2 25,830 4 Y 3 5,558 2 2 Y 4 12,369 3 3 Y 5 14,611 2 3 N 6 37,473 4 5 N 7 13,405 1 3 N 8 15,900 2 3 N 9 17,981 3 2 * 10 9,467 1 2 N in 22,826 4 4 Y 12 1,004 2 2 ha Based on a review of the site plan alone, it will appear that there were more soil tests performed than are shown in Table 2 for BMP 7. However, the applicant did several soil tests at the wrong time of the year (for example G1 and G2 were taken in May). While you can use mottling to establish the SHWT at any time of the year, water elevation can be used to determine SHWT only if the work was done between January and through April according to the New Jersey BMP Manual. The estimated SHWT provided by the applicant for G1 and G2 is the bottom of the test pit. All the test pits labeled with letters (not TP) and numbers were performed after April and cannot be counted towards compliance. Adequate testing for BMP 7 is essential since the basin bottom is proposed at an elevation of 531.5, approximately 16.5 feet lower than the delineated wetland located a little over fifty feet to the north of the basin. BMPs 5, 6, 8, and 10 are short one soil test and BMP 7 is short two test pits. This non-compliance is important, especially considering the example of BMP 6 where the elevation of the groundwater was shown to vary greatly due to the natural topography of the site. This is a vulnerability in the design that shows how the project is potentially not conforming to N.J.A.C. 7:8 5.4 (Local Ordinance 25-29.4 P) 7:8 5.6 (Local Ordinance 25-29.4 R) for groundwater recharge and stormwater quantity control standards. 2.4 GROUNDWATER MOUNDING CALCULATIONS The soil testing showed relatively low hydraulic conductivity for

Local Ordinance 25-29.4 R) for groundwater recharge and stormwater quantity control standards. 2.4 GROUNDWATER MOUNDING CALCULATIONS The soil testing showed relatively low hydraulic conductivity for most of the Site. The applicant proposes to replace the existing soil from the bottom of the BMPs to the SHWT with a sandy soil that has much higher hydraulic conductivity in an effort to meet the requirement that all basins Princeton Hydro, LLC Page | 12

West Essex Highlands Review West Orange, NJ Permit No. 722-04-0001.1 LUP230001 April 2025 must empty in 72 hours. This is a commonly used practice that has been previously accepted by the NJDEP. However, the applicant accounted for infiltration in the runoff routing calculations. That means that the model assumes some of the runoff is infiltrated, effectively removed from the simulation, and does not travel through the stormwater piping network. When one uses infiltration in their runoff routing calculations, one must provide groundwater mounding calculations for the water quality and 100-year storm. During a rain event, the groundwater will mound below BMPs that infiltrate. Therefore, the designed must provide these calculations to confirm the mounding does not encroach on the storage volume of the BMP. If the calculations indicate that the groundwater mound will intersect the basin bottom, the system will not infiltrate at the rate implied by the calculations and measured hydraulic conductivity. While the applicant did provide calculations for both scenarios, the groundwater mounding analysis for the 100-year event is critically flawed. Upon our further review, we believe that when properly completed the groundwater mounding analysis will indicate groundwater mound conflicts for all of the following BMPs: e BMP 3 © BMP 4 ° BMP1O Princeton Hydro will rely on PP3 as an example of the analysis that was performed on each of the BMPs to determine the mounding issue under the 100-year storm scenario. Princeton Hydro observed that the duration of infiltration in the groundwater mounding analysis for the water quality and the 100-year storm, were nearly identical for both storms (0.21 hours for water quality and 0.2 for one hundred year). The analysis for the water quality storm can be found on page 821 of 946 in the Drainage Report and the analysis for the 100-year storm on page 831 of 946 in the drainage report. The duration of these two different elements of a storm event should be very different. The water quality storm is only 1.25 inches where the 100-year storm is 8.33 inches. That is almost 7 times more water in the 100-year storm, due to the sheer volume difference the time should also be substantially different. The recharge rate is also different for both storms, Princeton Hydro does not know why the recharge rate would have different values for the

difference the time should also be substantially different. The recharge rate is also different for both storms, Princeton Hydro does not know why the recharge rate would have different values for the different storms and maintains that it should be the same for any storm. As noted previously, the design proposes to replace the existing soil from the bottom of the BMP down to the SHWT with a sandy soil that has a higher hydraulic conductivity to allow the runoff to infiltrate quicker through the BMP storage area. However, the native soil at the SHWT still has a very low hydraulic conductivity so the “infiltrated runoff" from the BMP will back up in the replacement soil since the soils at and below the SHWT infiltrate at a much slower rate. Typically, the stormwater report would provide calculations demonstrating that there was enough storage in the replacement soil to hold the “infiltrated runoff" while it infiltrates below the SHWT at a much slower rate. The calculations would show that the “infiltrated” runoff would be held in the replacement soil and not mound into the storage volume of the BMP. Groundwater mounding into the storage volume would directly impact the runoff peak flow rate calculations and the groundwater recharge calculations by reducing the amount of stormwater volume that could be managed by the BMP. Princeton Hydro, LLC Page | 13