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 7 the Department as necessary to provide designs specifications on additional best management practices and new information on already included practices reflecting the best available current information regarding the particular practice and the Department’s determination as to the ability of that best management practice to contribute to compliance with the standards contained in this chapter (N.J.A.C. 7:8). Alternative stormwater management measures, removal rates, or calculation methods may be utilized, subject to any limitations specified in this chapter, provided the design engineer demonstrates to the review agency, in accordance with N.J.A.C. 7:8-5.2(g), that the proposed measure and its design will contribute to achievement of the design and performance standards established by this chapter.” Chapter 12 of the NJ BMP Manual outlines the location and number of required soil explorations. Our office defers to NJDEP review regarding the number of required soil explorations for the proposed development. With that said, it is our understanding that the Applicant’s Engineer worked with the NJDEP to determine the number of required soil explorations for the development prior to completion. Finally, as indicated above, the Applicant received a NJDEP Permit which granted a Flood Hazard Area Individual Permit, Freshwater Wetlands General Permit 10B, Freshwater Wetlands General Permit 11, Freshwater Wetlands General Permit 17, and a Water Quality Certificate, dated November 15, 2024. 2.4 Groundwater Mounding Calculations: “…the groundwater mounding analysis for the 100-year storm has errors in it and upon further investigation, the groundwater mounding will reach into the storage volume for the following BMPs: • • • BMP 3 BMP 4 BMP 10” Chapter 13 of the NJ BMP Manual outlines the method(s) to complete groundwater mounding calculations for an infiltration BMP. Our office agrees that there appears to be some discrepancies with the groundwater mounding 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

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 S:\West Orange\Planning Board\VWRP0179.01 - West Essex Highlands, Inc\2025-08-15 - WEH - SWM Memo.docx