JMA02P003 262 270 Main Street Development Stormwater Management Report

Engineering Stormwater Narrative JMA02P003- May 26, 2026 262-270 Main St Development The remaining runoff discharges into two (2) trench drain systems that flow into an Aqua-Ponic treatment unit. The Aqua-Ponic unit treats the runoff at a rate of 80% before discharging into the porous pavement system for quantity control. Therefore, the total treatment for the site meets the required 80% and complies with Water Quality requirements. As for Water Quantity requirements, the NJDEP requires a reduction of 50%, 75%, and 80% for the 2-, 10-, and 100-year storm events, respectively, from the existing flow rates to the proposed flow rates. These requirements apply for the quantity storm events with both the current and future reduction factors applied as listed in NJAC 7:8 tables 5-5 and 5-6. These requirements will be met by the underground Cultec system and the porous pavement system which both discharge from their respective outlet control structures into the existing storm system on Main Street. The tables below demonstrate how the project complies with the Quantity reduction requirements. STORMWATER ANALYSIS (CURRENT) STORM TYPE EXISTING PERCENTAGE MAXIMUM PROPOSED RUNOFF RUNOFF RATE OF REDUCTION ALLOWABLE RATE (CFS) (CFS) RUNOFF RATE (CFS) 2-YEAR 2.68 50% 1.34 0.06 10-YEAR 4.20 75% 3.15 0.39 100-YEAR 7.27 80% 5.82 3.15 STORMWATER ANALYSIS (FUTURE) STORM TYPE EXISTING PERCENTAGE MAXIMUM PROPOSED RUNOFF RUNOFF RATE OF REDUCTION ALLOWABLE RATE (CFS) (CFS) RUNOFF RATE

RUNOFF RATE OF REDUCTION ALLOWABLE RATE (CFS) (CFS) RUNOFF RATE (CFS) 2-YEAR 3.17 50% 1.59 0.11 10-YEAR 4.98 75% 3.74 1.34 100-YEAR 9.13 80% 7.30 4.05 6 Groundwater Recharge According to chapter 5.4 of NJAC 7:8, groundwater recharge is required for a major development project. The groundwater recharge was calculated using the GSR-32 spreadsheet taken from the New Jersey Best Management Practices (NJBMP) manual. The post-development annual recharge deficit was calculated to be -543 cubic feet. Since the deficit is negative, which indicates that more groundwater will be recharged into the soil for post- development conditions than pre-development conditions, the groundwater recharge requirements for this project have been met. 2