2151002Princeton Hydro West Essex Stormwater Comments to Planning Board 20250310

Stormwater Management Review for Municipal Planning Board Approval West Highlands, Inc. Block No. 179, Lot No.32, West Orange Township, Essex County, New Jersey March 2025 Princeton Hydro, LLC: 2151.002 7 Finally, there is an error with BMP 9. The construction detail states that TP 46 has a SHWT at 548 ft, but the soil profile states the ground surface elevation is 574 ft and the depth to SHWT is 8 ft, which would locate the SHWT at 566 ft. Elevation 566 ft is much higher than 548 and would require the design to be significantly altered. See Figure 5 below for references to the plans and soil profiles. Figure 5: Cross section at PP9, Location of TP-46, TP-46 Soil Profile These findings show that BMPs 4, 6 and 9 are not compliant with NJDEP BMP Manual. The SHWT is too high and would occupy a portion of the storage volume of each of the BMPs. This would result in less groundwater recharge than what is calculated in the stormwater report and higher peak flow rates from each BMP, which