Exhibit O6 2151002Princeton Hydro West Essex Stormwater Comments 202401115

Stormwater Management and Freshwater Wetlands Review West Highlands, Inc. Block No. 179, Lot No.32, West Orange Township, Essex County, New Jersey November 2024 Princeton Hydro, LLC: 0683.022 6 The time of concentration (Tc) calculations for the existing conditions model were performed incorrectly, yielding a smaller Tc and resulting in a higher peak flow rate in the existing condition. The designer is required to use the Velocity Versus Slope for Shallow Concentrated Flow graph found on page 26 of Chapter 5 of the BMP Manual (Figure 5-13) to determine the velocity of the runoff traveling through the segment of shallow concentrated flow, but they did not use that graph to determine the velocity. For example, in the existing conditions model at POA 1, the designer assumed the runoff would have a velocity of 16.1 ft/s for 1,625 ft (travel time of 7.2 minutes). Per Figure 5-13, a forested area at a ground slope of 5% would yield a velocity of 0.5 ft/s (travel time of 54.2 minutes). The total time of concentration would thereby be 69.1 minutes as opposed to the 22.1 minutes as used in the applicant’s model. A longer time of concentration results in a lower peak flow rate and as stated previously, the proposed design must yield peak flow rates lower than the existing condition. By artificially increasing the pre-development flow rates with erroneous Tc computations, the applicant is able to show the proposed design is in compliance, where in reality, it is not. To demonstrate this, Princeton Hydro remade the model for POA 1 existing conditions using the higher Tc value and found that it lowered the peak flow rate from 19.4 cfs to 10.52 cfs, which is almost a 50% reduction in the peak flow rate. With the reduced existing conditions peak flow rate, POA 1 no longer is compliant with the peak flow rate reduction for the 10-year storm. The proposed condition actually has a higher peak flow rate (15.29 cfs) than the existing conditions (10.52 cfs). This error is present in each drainage area in the existing conditions model, invalidating all reported results. 2.4 GENERAL PLAN COMMENTS Sanitary sewer and other utilities are proposed below (or within) proposed porous pavement BMPs. Sanitary sewers are required to have 18 inches of vertical separation and 10 feet of horizontal separation from stormwater facilities. Sanitary sewer cannot run through stormwater detention

ment BMPs. Sanitary sewers are required to have 18 inches of vertical separation and 10 feet of horizontal separation from stormwater facilities. Sanitary sewer cannot run through stormwater detention systems. The analysis provided in this letter is based on the guidance from the NJDEP that this project is exempt from the Inland Flood Protection Rules that became effective on July 17, 2023, and should be evaluated on the NJDEP Green Infrastructure Rules that became effective on March 2, 2021. On the advice of counsel, Objectors reserves the right for further legal action to determine if the Inland Flood Protection Rules are applicable. 3.0 SUMMARY In conclusion, our detailed review has found that the application is not in compliance with applicable State stormwater requirements. It is my professional opinion that the application does not meet all three central performance requirements of the State stormwater requirements. Since the project has not demonstrated compliance with all three specific stormwater management requirements of the central goals of stormwater management planning as outlined in NJAC 7:8, in my professional opinion, the application is non-approvable as designed. If the application is approved as designed, the development will increase the frequency and severity of damage expected during a flood in the adjacent and downstream areas.