V3 RESUBMISSION Stormwater Management Report Rev 2 Dated November 3 2022

BASIN #1B — 4.474 CF Detention Basin #1B is a subsurface detention basin with 4,474 cubic feet of storage. The system is comprised of 5 rows of 48" diameter HDPE pipe, totaling 300 feet in length. The bottom of the basin is at elevation 404.00, along with 2 — 4" x 5" orifices. At elevation 406.35, 1 — 6” x 18" orifice will also be placed, followed by a 4' weir at an elevation of 407.25. BASIN #2 — 16,898 CF Detention Basin #2 is a surface basin with 16,898 cubic feet of storage. The bottom of the basin is set at elevation 414.00 along with 1 — 8" x 16" rectangular orifice. 2 — 13” x 22” orifices will be placed at elevation 416.00, and a 4' weir is placed at elevation 418.00. It should be noted that the 100-year storm event reaches an elevation of 417.97, just below the elevation of the weir. The top of the basin is set at 419, which allows for 1 foot of freeboard. BASIN #3 — 11,200 CF Detention Basin #3 is another surface basin with 11,200 cubic feet of storage. The bottom of the basin is set at elevation 416.00, where 1 — 4” x 10" orifice will also be placed. 2 — 6” x 10" orifices will be placed at elevation 417.00, and 2 — 8” x 10" orifices will be placed at an elevation of 418.00. Finally, a 4' weir will be placed at elevation 420.00. It should be noted that the 100-year storm event reaches an elevation of 419.98, just below the elevation of the weir. The top of the basin is set at 421.00, which allows for 1 foot of freeboard. POST-DEVELOPMENT RUNOFF Using the information described above, the peak flows during the 2-, 10-, and 100-year storm events were calculated. Table 5 below summarizes the peak flows during each storm event. (See attached Hydraflow Output for Proposed Conditions Hydrographs, CN Values, and Time of Concentration Calculation.) Table 5 — Proposed Peak Runoff Rates Target Storm Event Site Proposed Site Runoff Runoff 2 Year 14.859 cfs 14.78 cfs 10 Year 39.811 cfs 39.73 cfs 100 Year _| 86.688 cfs 86.57 cfs DRAIN TIME As shown by the Hydraflow Hydrographs attached to this report, the detention time of the system is below 72 hours and is broken down as follows: Detention Basin #1A — 27 hrs. Detention Basin #1B — 27 hrs. Detention Basin #2 —-27 hrs. Detention Basin #3 — 27 hrs.