21 Stormwater Mgmt Report_082025

4.1.1 Proposed Drainage Area #1 Proposed Drainage Area #1 consists of approximately 1.36 acres of land, of which 1.27 acres are impervious surface, and includes the proposed portion of the building to be repurposed for retail, parking fields, sidewalks, driveways, and stormwater infrastructure. The drainage area also contains grass and landscape areas. The runoff from Proposed Drainage Area #1 flows to Rahway River, and the existing inlet along Mount Pleasant Place, which ultimately reaches Point of Analysis #1. 4.2 Stormwater Quantity Controls The following stormwater quantity standard technique from the NJDEP Stormwater Management Regulations is being applied to the drainage area as noted in Section 4.1: 1. For stormwater runoff leaving the site, the post-development runoff hydrographs for the current and future/projected 2-, 10-, and 100-year storms do not exceed, at any point in time, the pre-development runoff hydrographs for the same storm events. This technique will be applied to drainage areas that, under proposed conditions, will remain unchanged or have a net decrease in impervious coverage. Table 4.1 - Point of Analysis #1 Existing vs. Proposed Comparison Current Adjusted Precipitation Depths (Add tables for additional drainage areas as required) Existing Proposed Peak Flow Peak Flow CFS CFS 2-Year Storm 4.41 3.80 10-Year Storm 6.89 6.07 100-Year Storm 11.80 10.58 See Appendix A for Comparison Hydrographs. Table 4.2 - Point of Analysis #1 Existing vs. Proposed Comparison Future Adjusted Precipitation Depths Existing Peak Flow Proposed Peak Flow CFS CFS 2-Year Storm 5.22 4.57 10-Year Storm 8.17 7.23 100-Year Storm 14.84 13.41 See Appendix B for Comparison Hydrographs. ▪ Stormwater Management Report for Proposed Retail Store▪ 5 ▪ August 2025 ▪