O30 Princeton Hydro Report Dated 9 3 25

West Essex Highlands Review = West Orange, NJ Permit No. 722-04-0001.1 LUP230001 April 2025 Figure 8 Plan view of BMP 7from the construction plans showing 16.5 foot cut downgradient of mapped wetland to the north. 2.6 TIME OF CONCENTRATION Existing conditions were incorrectly calculated for this project. The time of concentration (TC) is the time it takes for runoff to travel through the watershed on the longest hydrologic flow path. The designer used an outdated method to determine the TC for the drainage areas POA | and 2. Due to the very small size of the drainage area for POA 3, it was not included in this analysis. The plans describe the land use as “unpaved” which is an older land use classification that is not used in the latest method. Princeton Hydro would note that this method was not issued during the last update to the stormwater rules which NJDEP ruled did not apply to this project, but it was updated on the previous rule change in 2021 which do apply to this application. TC for this system was broken down into two different flows: sheet flow and shallow concentrated flow. Runoff then transitions from sheet flow to shallow concentrated flow. Shallow concentrated flow Princeton Hydro, LLC Page | 18