2025 08 15 WEH SWM CME Memo

Chairman and Members of the West Orange Township Planning Board August 15, 2025 Re: West Essex Highlands, LLC (PB 24-01) Our File No. 115.WRP0179.V01 Response To Objector’s Stormwater Management System Review Page 8 contribute to achievement of the design and performance standards established by N.J.A.C. 7:8. Further, Special Condition #2 of the NJDEP Permit referenced above indicates that the Department has determined that this project meets the requirements of the Stormwater Management Rules at N.J.A.C. 7:8. 2.5 Impacts to Wetlands: The proposed stormwater system intends to route the stormwater runoff through a pipe network to down-gradient basins where all of the surface runoff will discharge much further downstream. The wetlands uphill of the discharge locations will therefore collect less stormwater runoff due to their reduced contributory drainage areas. Impacts to Freshwater Wetlands are under the jurisdiction of the New Jersey Department of Environmental Protection (NJDEP). As indicated above, the Applicant has received the necessary Freshwater Wetland permitting from NJDEP. 2.6 Peak Flow Calculations: “Based on our review of the existing conditions mapping and modeling, we believe the time of concentration computations were done incorrectly for this project.” “…It appears that the designer used an old method to determine the TC for drainage areas POA 1 and 2.” “…Princeton Hydro would note that the NJDEP ruling on this project means that the latest (2023) Stormwater Rule update does not apply. However, the TC calculation methodology referenced above was updated with the previous rule change in 2021.” Chapter 5 of the NJ BMP Manual outlines the method to complete time of concentration calculations. Our office agrees that there appears to be some discrepancies with the time of concentration calculation methodology completed by the Applicant’s Engineer as compared to the methodology outlined in the BMP Manual. With that said, as indicated above, the BMP Manual provides guidance to address the standards in the Stormwater Management Rules, N.J.A.C. 7:8 and alternative stormwater management calculation methods may be utilized provided the design engineer demonstrates to the review agency that the proposed measure and its design will contribute to achievement of the design and performance standards established by N.J.A.C. 7:8. S:\West Orange\Planning

demonstrates to the review agency that the proposed measure and its design will contribute to achievement of the design and performance standards established by N.J.A.C. 7:8. S:\West Orange\Planning Board\VWRP0179.01 - West Essex Highlands, Inc\2025-08-15 - WEH - SWM Memo.docx