2151002Princeton Hydro West Essex Stormwater Comments to Planning Board 20250310

Dr. Robert Bagoff- Chair March 10, 2025 West Orange Planning Board 66 Main Street West Orange, NJ 07052 RE: PB-24-01 West Essex Highlands, Inc Block: 179 Lot: 32 Zone: IH-1 Warner Road West Orange Township, Essex County, New Jersey Dear Dr. Bagoff, At the request of attorney Bruce Afran, counsel for objectors and We Care NJ Corp., Princeton Hydro has performed an independent technical review of the aforementioned development located in West Orange Township, NJ. The project is also the subject of a Planning Board Approval from the West Orange Planning Board. Documents central to the contents of this letter include but are not limited to the following: • Subsurface Investigation Report Subsurface Stormwater Management System West Orange, New Jersey for Garden Homes Short Hills, New Jersey Prepared by Sor Consulting Engineers, Inc. 98 Sand Park Road, Cedar Grove, NJ 07009, Report Number 23-C-17 May 23, 2023, Job No. 23-C-16 • Subsurface Investigation Report Subsurface Stormwater Management System West Orange, New Jersey for Garden Homes Short Hills, New Jersey Prepared by Sor Consulting Engineers, Inc. 98 Sand Park Road, Cedar Grove, NJ 07009, Report Number 21-C-21 May April 19, 2021, Job No. 21-C-01 • Subsurface Investigation Report Subsurface Stormwater Management System West Orange, New Jersey for Garden Homes Short Hills, New Jersey Prepared by Sor Consulting Engineers, Inc. 98 Sand Park Road, Cedar Grove, NJ 07009, Report Number 24-C-11 April 4, 2024, Job No. 24-C-02 • Subsurface Investigation Report Subsurface Stormwater Management System West Orange, New Jersey for Garden Homes Short Hills, New Jersey Prepared by Sor Consulting Engineers, Inc. 98 Sand Park Road, Cedar Grove, NJ 07009, Report Number 24-C-02 February 12, 2024, Job No. 24-C-02 • Plan titled, “Preliminary and Final Site Plans West Essex Highlands Block 179 Lot 32, Block 179.17 Lots 8 and 9 Township of West Orange Essex County, New Jersey, Overall Drainage Area Map” prepared by Paul W. Anderson, PE of Anderson Consulting Services LLC., dated September 23, 2022, last revised October 28, 2024. • Drainage Report, “Stormwater Management Report (formerly Drainage Report) West Essex Highlands Block 179, Lot 32, Township of West Orange, Essex County, New Jersey,” prepared for West Essex Highlands Inc., prepared by Anderson Consulting Services LLC., dated March 12, 2023, last revised October 28,

k 179, Lot 32, Township of West Orange, Essex County, New Jersey,” prepared for West Essex Highlands Inc., prepared by Anderson Consulting Services LLC., dated March 12, 2023, last revised October 28, 2024. It is our professional opinion that the application contains critical deficiencies and errors related to stormwater management design. For this reason, the application should not be approved at this time.

Stormwater Management Review for Municipal Planning Board Approval West Highlands, Inc. Block No. 179, Lot No.32, West Orange Township, Essex County, New Jersey March 2025 Princeton Hydro, LLC: 2151.002 2 1.0 INTRODUCTION The application entails the proposed construction of multi-family residential development with recreational facilities and a clubhouse for residents of the facility with a limit of disturbance of 1,233,793 sf (28.32 acres). The 120-acre parcel is currently undeveloped. The project has not received any Municipal but has received DEP approval in October 2024. The purpose of this letter is to briefly summarize deficiencies that we have observed in the revised application materials related to critical aspects of the application’s compliance with the New Jersey Stormwater Management Rules at N.J.A.C. 7:8 and the Township’s local stormwater ordinance, §25-29 of the general ordinances. 2.0 STORMWATER MANAGEMENT The site plans and stormwater calculations have been reviewed to determine if the design engineer has demonstrated compliance with N.J.A.C. 7:8, the New Jersey Stormwater BMP Manual and §25-29 of the local general ordinances. We find the application fails to demonstrate it meets the requirements as it relates to the soil testing requirements (Chapter 12 of the New Jersey Department Best Management Practices Manual, BMP Manual) and the two of the three primary stormwater management performance metrics, groundwater recharge (section P of §25-29) and stormwater runoff quantity standards (section R of §25-29). The following subsections outline our specific concerns as they relate to these three areas with the application submission. It is our professional opinion that the applicant has failed to demonstrate compliance with the requirements of N.J.A.C. 7:8. 2.1 SOIL TESTING REQUIREMENTS Before discussing the issues of compliance with two of the three primary stormwater management performance metrics, this section will provide a breakdown of the soil testing requirements as stated in Chapter 12 of the BMP Manual and compare it to the soil testing provided in this application. The BMP manual was developed to provide examples of ways to meet stormwater design standards set by the state. The BMP Manual was developed by the New Jersey Department of Environmental Protection, in coordination with the New Jersey Department of Agriculture, the New Jersey

design standards set by the state. The BMP Manual was developed by the New Jersey Department of Environmental Protection, in coordination with the New Jersey Department of Agriculture, the New Jersey Department of Community Affairs, the New Jersey Department of Transportation, municipal engineers, county engineers, consulting firms, contractors, and environmental organizations. As stated in Chapter 12 of the BMP Manual, understanding the character and saturated conductivity of surface and subsurface soils at a proposed land development site is crucial to the design of stormwater best management practices (BMPs) that meet the requirements of the New Jersey Stormwater Management rules at N.J.A.C. 7:8 and §25-29 of the local general ordinances. Section 2 of Chapter 12 further clarifies that saturated soil hydraulic conductivity and depth to Seasonal-High Water Table (SHWT) are of high importance for the design of stormwater BMPs. Subsection 1d of Chapter 12 provides guidelines for determining the upper limit of the zone of saturation which is known as the SHWT. The chapter states there are two methods for determining the SHWT: 1. When mottling showing the redoximorphic features is observed at any season of the year, the SHWT shall be taken at the highest level at which mottling is observed except when the water table is observed at a higher elevation. 2. When mottling showing redoximorphic features is not observed the SHWT shall be determined by water level elevation observed in the soil pit or boring when the testing took place from January through April.

Stormwater Management Review for Municipal Planning Board Approval West Highlands, Inc. Block No. 179, Lot No.32, West Orange Township, Essex County, New Jersey March 2025 Princeton Hydro, LLC: 2151.002 3 If the work was done at other times, the depth to SHWT can be obtained from the NRCS Web Soil Survey. Mottling is defined as contrasting or “blotchy” color patterns within a dominant soil color. It is forms as the SHWT rises into oxygenated soils, changing the conditions in the soils from aerobic to anoxic resulting in a gray “blotches”, see Figure 1 below. The coloring of the soil is caused when the water table rises, createing anaerobic (oxygen-depleted) conditions. Bacteria that thrive in anaerobic conditions use the oxygen in iron and manganese oxides, changing the color of the minerals. When the water table drops, the dissolved minerals are deposited on the soil particles. The deposited minerals appear as coatings on the soil particles in colors such as yellow, red, orange, brown, blue, or black. Areas that have been saturated for long periods can lose all of their iron and manganese oxides, turning gray. The mottling will show the highest elevation that SHWT has occurred historically. This process takes years to occur and is considered more accurate than the water elevation because it is not impacted by recent weather conditions. Figure 1: Example of Mottling in Soil While reviewing the multiple subsurface investigation reports for this project, the soil profiles never make any mention of mottling. That is very unusual, as stated above the BMP Manual states that mottling should be used to established using mottling with the observed water level. Importantly, soil logs must also be specific in their identification of various color throughout the profile, as is consistent with the Field Indicators of Hydric Soils in the United States referenced by the NJDEP BMP Manual. Color identification is key in correctly identifying mottling by recording both the number of different colors observed, as well as the value and chroma of the observed colors. Figure 2 provides a comparison of a sample soil profile which uses the Munsell method per the Field Indicators of Hydric Soils (top) and the soil profiles for this project (bottom). It appears that the SHWT was only established using the elevation of the water found in the test pit or boring and no effort was made

ydric Soils (top) and the soil profiles for this project (bottom). It appears that the SHWT was only established using the elevation of the water found in the test pit or boring and no effort was made to document mottling. As noted in the NJDEP BMP Manual, there are instances where mottling can be absent from a soil profile, but it is highly unusual that mottling was not found in any of the soil test pits or borings provided by the applicant. Mottling is a natural and common process, thus it is fair to assume mottling should have been observed in some of the soil profiles. The concern is that the groundwater level found in a test pit can fluctuate on a daily basis based on the recent weather. Using the mottling to determine the SHWT is recommended because it estimates the highest (most conservative) elevation that does not vary with time. If one only uses the observed groundwater elevation, it is safe to assume that the SHWT elevation is probably underestimated. It is recommended that the professionals who documented these test pits should provide the Planning Board with testimony to explain why mottling was never documented and discuss the how their reports could be underestimating the elevation of SHWT.

Stormwater Management Review for Municipal Planning Board Approval West Highlands, Inc. Block No. 179, Lot No.32, West Orange Township, Essex County, New Jersey March 2025 Princeton Hydro, LLC: 2151.002 4 The NJDEP BMP Manual requires that BMPs maintain a minimum vertical difference of 2 feet from the bottom of the BMP to the SHWT elevation for BMPs without underdrains. The BMPs in this project do not have underdrains. BMPs 2, 6 and 7 maintain that minimum separation. If the SHWT elevations are higher than what was recorded in this plan, then there is a risk these designs are not compliant with the NJDEP BMP Manual. The manual requires these depths as a precaution to prevent groundwater from mounding into the storage area of the basins during rain storms. If the groundwater mounding encroaches on the storage area, it will increase the stormwater runoff from the BMP and decrease the amount of groundwater recharge the BMP provides. N.J.A.C. 7:8 5.4 (§25-29.4 P) sets the groundwater recharge requirements and 7:8 5.6 (§25-29.4 R) sets the minimum reductions in the peak flow rates for runoff exiting a site. If the SHWT is higher in BMPs 2, 6 or 7 that would impact the site’s compliance with those two standards. Figure 2: Example of Soil Profiles that use the Munsell Method to document SHWT and the Soil Profiles for this project

Stormwater Management Review for Municipal Planning Board Approval West Highlands, Inc. Block No. 179, Lot No.32, West Orange Township, Essex County, New Jersey March 2025 Princeton Hydro, LLC: 2151.002 5 2.2 BMP DESIGN STANDARDS AND SHWT Princeton Hydro reviewed the SHWT elevations documented in the subsurface investigations against the proposed BMP designs to confirm that each of the proposed BMPs met the minimum two vertical feet of separate from the bottom of the basin to the SHWT. Princeton Hydro found that the following BMPs did not meet that minimum standard: • BMP 6 (Porous Pavement) • BMP 4 (Porous Pavement) • BMP 9 (Aboveground basin) BMP 6 shows a SHWT of 598 ft using the 2024 soil testing data but 2021 shows a different story. TP 4 shows seepage at 608 ft, which is 10 feet higher than what the plans show. Based on this finding, the porous pavement design not compliant. The SHWT intersects the storage volume of the basin as shown in Figure 3. Figure 3: Cross Section of PP6, Proximity of TP-4 to PP6 and TP-4 Soil Profile Likewise, BMP 4 records the SHWT at 567 ft (Figure 4) on the plans but that is only using data from the soil tests taken in 2024 (TP 28). In 2021, soil tests were also taken and TP 10 (Figure 4) is very close to BMP 4. TP 10 shows a SHWT of 573 ft, 6 feet higher than TP 28 which would have the SHWT intersecting the storage bed of the BMP. Please note that there is 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; it is left blank. Elsewhere on the document it states that seepage was found at 3

Stormwater Management Review for Municipal Planning Board Approval West Highlands, Inc. Block No. 179, Lot No.32, West Orange Township, Essex County, New Jersey March 2025 Princeton Hydro, LLC: 2151.002 6 feet below grade which is an elevation of 573 ft (576 ft - 3 fbgs). 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. Figure 4: Cross Section of PP4 from Construction Plans, Proximity of TP-10 to PP4, TP-10 Soil Profile

Stormwater Management Review for Municipal Planning Board Approval West Highlands, Inc. Block No. 179, Lot No.32, West Orange Township, Essex County, New Jersey March 2025 Princeton Hydro, LLC: 2151.002 7 Finally, there is an error with BMP 9. The construction detail states that TP 46 has a SHWT at 548 ft, but the soil profile states the ground surface elevation is 574 ft and the depth to SHWT is 8 ft, which would locate the SHWT at 566 ft. Elevation 566 ft is much higher than 548 and would require the design to be significantly altered. See Figure 5 below for references to the plans and soil profiles. Figure 5: Cross section at PP9, Location of TP-46, TP-46 Soil Profile These findings show that BMPs 4, 6 and 9 are not compliant with NJDEP BMP Manual. 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 what is calculated in the stormwater report and higher peak flow rates from each BMP, which