V4 11 Stormwater Report Rev 3 1 26 2023

CURVE NUMBERS Table 1 — Curve Number (Existing Conditions) Description Hydrologic Curve Group Number Woods A 30 Woods Cc 70 Woods D 77 Open Space ie 74 Open Space D 80 Impervious A/B/C/D 98 PEAK FLOWS Using the information described above, the peak flows during the 2-, 10-, and 100-year storm events were calculated. Table 2 below summarizes the peak flows during each storm event. (See attached Hydraflow Output for Existing Conditions Hydrographs, CN Values, and Time of Concentration Calculations.) Table 2 — Existing Peak Runoff Rates Storm Event | Existing Site Runoff 2 Year 20.08 cfs 10 Year 45.76 cfs 100 Year 96.75 cfs POST-DEVELOPMENT RUNOFF TARGET Since the improvements on the site are considered a major development, proposed runoff rates shall meet the NJDEP Stormwater regulations and reductions for the 2, 10, and 100-year storm events. NJ standards require that the preconstruction runoff rates are to be reduced to at least 50, 75, and 80, respectively, for the areas which are to be disturbed or developed. The proposed reductions will only account for the areas of the site, which are being disturbed as a result of the proposed development. The equations below were used to determine the reductions based on the limit of disturbance, as shown on the Soil Erosion and Sediment Control Plan. 5 Year Reduction = 10.50(0.50) _ 0.260 ear Keduction = 20.16 =0. 10 Year Reduction = 10.50(0.25) = 0.130 ear Keduction = 20.16 =0. 100 Year Reduction = 10.50(0.20) _ 0.104 ear Keauction = 20.16 =U. & “ ;