Stormwater Management Report Feb 2026 resubmissionrcd 2 26 2026

Study Area Roof: This area consists of the entire 0.142 acres of roof area for the proposed building. Under proposed conditions the runoff generated by this area flows into a roof leader manifold and is discharged into the proposed 48” HDPE Underground Detention Basin to the north of the proposed building. The underground pipe storage provides detention for the runoff, slowing the rate of flow to the POI #1, the ultimate discharge point. Bioretention Basin: This area consists of 0.140 acres towards the front of the site which includes motor vehicle surfaces, impervious and grass areas. Under proposed conditions runoff generated by this area flows overland into the proposed bioretention basin via a 4’ wide curb cut. Proposed Conditions Input Summary Table Drainage Area Drainage Time of Curve Number Name Area Concentration (CN) (acres) (minutes) PDA-Roof Area 0.142 1 98 Impervious PDA-Bioretention 0.050 5.1 80 Basin (Pervious) PDA-Bioretention 0.090 0.5 98 Basin (Impervious) PDA-Uncontrolled 0.10 5.0 80 (Pervious) PDA-Uncontrolled 0.204 2.00 98 (Impervious) Proposed Conditions Flow Summary Table Drainage Current Adjusted Rainfall Projected Adjusted Rainfall Area Conditions Conditions Name Q2 (CFS) Q10 (CFS) Q100 (CFS) Q2 (CFS) Q10 (CFS) Q100 (CFS) POI - MH 1.47 2.42 4.93 1.79 2.92 6.44 5. Stormwater Management System Design A summary of each basin’s water surface elevation (WSEL) and outflow rates for the Water Quality, 2-, 10-, and 100-year storm event for both current and projected conditions are provided below. These WSELs and outflows assume normal operating conditions for each basin. In addition, the emergency spillway water surface elevation and outflow for the projected 10-year storm event have been calculated assuming the outlet structure has failed and there is

for each basin. In addition, the emergency spillway water surface elevation and outflow for the projected 10-year storm event have been calculated assuming the outlet structure has failed and there is no storage below the emergency spillway. Routing calculations for the basins and emergency spillway calculations are included in the Appendix. Mavis Tire Supply, LLC July 2025 DEC# 1956-24-04187 4 Last revised February 2026