O30 Princeton Hydro Report Dated 9 3 25

gz PB-24-01 West Essex Highlands, Inc. Block No. 179, Lot No.32, West Orange Township, Essex County, New Jersey September 2025 With respect to the Time of Concentration calculation the CME letter concedes the following: 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. If CME's review revealed discrepancies regarding the Time of Concentration calculation methodology, they have an obligation to outline these discrepancies, especially considering the critical implications it has for downstream residents of the Township. However, the CME letter offers no further discussion of these discrepancies and instead simply again deflects their responsibility to the NJDEP. On the contrary, Princeton Hydro was clear in the March 10, 2025 letter that part of the issue with the time of concentration calculations was not just using different velocity factors which could be classified as an “alternative method” but that the basic underlying analysis of the drainage area was incorrectly executed. Two points of analysis cannot have one drainage area and the flow path to the point of analysis was not complete, stopping several hundred feet short and thereby artificially elevating the existing peak flow rates (thus artificially reducing the necessary size of the stormwater system). The CME letter suggests that alternative methods were used but does not provide any justification for the applicant's methodologies, nor does the CME letter attempt to illustrate how the alternative method complies with the Township's stormwater ordinance. Most importantly, CME other than agreeing that there are “some discrepancies", the CME letter does not offer any objective analysis or professional opinion on whether or not the applicant's approach is sound. As the Township's consulting engineer, CME should not attempt to justify an incorrect analysis by stating that it is simply an alternative stormwater methodology, instead they have a responsibility to objectively analyze the applicant's stormwater design. This is especially relevant in this context as the 100-year storm for the proposed project would, contrary to the stormwater rules, actually generate higher peak flow rate than what currently exists (see Attachment A

ly relevant in this context as the 100-year storm for the proposed project would, contrary to the stormwater rules, actually generate higher peak flow rate than what currently exists (see Attachment A pages 19-21). This is an important issue for the Township representatives to consider as there are well-documented flood- prone areas immediately downstream of the proposed development. In order to meet the peak flow rate requirements set forth by the local ordinance, our analysis has shown that the design would need to be substantially changed to increase storage in the proposed stormwater system and this would likely have a substantial impact on the current overall site design. The CME letter concedes that the number of soil explorations is not compliant with the NJDEP BMP Manual but states that the applicant worked with the NJDEP to determine the number of required soil explorations for the development prior to completion. It is not clear if CME has an explanation for the change of requirements from the NJDEP or the applicant as it relates to this key issue. That justification should be provided as part of the application to the board. With respect to the groundwater mounding calculations, here again the CME letter states that: 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. Again, the CME letter fails to outline or offer any additional information on these discrepancies, and instead deflects this responsibility on the pretense of an NJDEP permit. The CME letter states that the sanitary sewer piping will not be installed within any of the stormwater management systems. The applicant's engineer will be required to revise the plans prior to construction. However, as shown in Figure 1 below, the sanitary sewer is surrounded by wetlands. Therefore, relocating this pipe will most likely require additional wetlands permitting; a fact and supporting context/information not provided by the CME letter. Princeton Hydro, LLC: 2151.002 3