2026 05 Storm Water Management Report rcd 5 6 2026

Bioretention Basin: This area consists of 0.146 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 0.068 5.1 80 Basin (Pervious) PDA-Bioretention 0.078 0.5 98 Basin (Impervious) PDA-Uncontrolled 0.071 5.0 80 (Pervious) PDA-Uncontrolled 0.204 2.0 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 #1 1.35 2.18 4.27 1.64 2.61 5.59 Point of Analysis #2 Study Area 2: This area consists of 0.042 acres which includes the portion of the area to be developed that drains to Prospect Avenue. In the proposed condition, this area will be occupied by concrete sidewalks installed per Township request, as well as lawn area similar to the existing condition. Stormwater runoff generated by this area flows overland to the right-of-way, as depicted on the Proposed Drainage Area Map. Proposed Conditions Input Summary Table Drainage Area Drainage Time of Curve Number Name Area Concentration (CN) (acres) (minutes) PDA 2 – Impervious 0.017 0.8 98 PDA 2 – Pervious 0.025 3.5 80 Proposed Conditions Flow Summary Table

– Impervious 0.017 0.8 98 PDA 2 – Pervious 0.025 3.5 80 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 #2 0.11 0.20 0.37 0.14 0.24 0.47 Mavis Tire Supply, LLC July 2025 DEC# 1956-24-04187 5 Last revised May 2026

Point of Analysis #3 Study Area 3: This area consists of 0.076 acres which includes lawn area that sheet flows to the northeast corner of the site and is not collected by the onsite stormwater conveyance system. Proposed Conditions Input Summary Table Drainage Area Drainage Time of Curve Number Name Area Concentration (CN) (acres) (minutes) PDA 3 – Pervious 0.076 8.5 80 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 #3 0.13 0.25 0.52 0.17 0.33 0.69 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 no storage below the emergency spillway. Routing calculations for the basins and emergency spillway calculations are included in the Appendix. Bioretention Basin Summary Table Storm Event (years) Water Surface Elevation (ft) Outflow (CFS) Water Quality 622.79 0.00 Current – 2 623.12 0.24 Current – 10 623.29 0.47 Current – 100 623.54 0.85 Projected – 2 623.19 0.33 Projected – 10 623.36 0.57 Projected – 100 623.69 1.07 Mavis Tire Supply, LLC

623.36 0.57 Projected – 100 623.69 1.07 Mavis Tire Supply, LLC July 2025 DEC# 1956-24-04187 6 Last revised May 2026

Underground Detention Basin Summary Table Storm Event (years) Water Surface Elevation (ft) Outflow (CFS) Water Quality 618.77 0.22 Current – 2 618.91 0.24 Current – 10 619.58 0.31 Current – 100 620.82 0.94 Projected – 2 619.12 0.26 Projected – 10 619.94 0.34 Projected – 100 621.43 1.35 6. Green Infrastructure Compliance The bioretention basin noted above has been designed to comply with the stormwater runoff quantity, quality, and groundwater recharge requirements for the proposed development as applicable. The proposed basin has been designed in accordance with NJAC 7:8 and the New Jersey Stormwater Best Management Practices. The tables below summarize the design considerations for each basin, see the Site Plan details for additional information. Small-Scale Bioretention Basins (Table 5-1 – Quantity, Quality, & Recharge) Design Criteria Required Provided Total Drainage Area -- 0.146 acres Min. Storage Volume below 0.008 Ac-FT 0.008 Ac-FT 1st Orifice Depth of Soil Bed 18 in. Terrestrial Forested 18 in. Terrestrial Forested Community Community Max. Contributory DA 2.5 acres 0.146 acres Max. Drain Time 72 hours 27.64 hours Separation from SHWT 1 foot (Underdrain) SHWT Not encountered to depth elevation 615.0 (TP-05) Design Permeability Rate Min. = 0.5 in/hr 0.5 in/hr Max. = 10 in/hr Underdrains are proposed Max. Depth of WQ Storm 1.0 feet 0.79 feet 7. Water Quantity Control

Max. = 10 in/hr Underdrains are proposed Max. Depth of WQ Storm 1.0 feet 0.79 feet 7. Water Quantity Control Compliance The site has been designed to reduce peak flows for the 2-, 10- and 100-year storm events to the maximum extent practical as compared to the pre-development conditions. The points of analysis have been identified on the Drainage Area Maps as previously described. Below are summary tables demonstrating the proposed peak flows. Mavis Tire Supply, LLC July 2025 DEC# 1956-24-04187 7 Last revised May 2026

Point of Analysis #1 Storm Event Existing Peak Proposed Peak Percent Flow Rate (cfs) Flow Rate (cfs)* Reduction Current 2-year 1.44 1.35 6.3% Current 10-year 2.41 2.18 9.5% Current 100-year 4.45 4.27 4.0% Projected 2-year 1.75 1.64 6.3% Projected 10-year 2.94 2.61 11.2% Projected 100- 5.76 5.59 3.5% year Point of Analysis #2 Storm Event Existing Peak Proposed Peak Flow Rate (cfs) Flow Rate (cfs)* Current 2-year 0.07 0.11 Current 10-year 0.14 0.24 Current 100-year 0.30 0.37 Projected 2-year 0.09 0.14 Projected 10-year 0.18 0.24 Projected 100- 0.41 0.47 year *Increase in proposed peak flow rate is due to addition of sidewalk within the Prospect Avenue right-of-way at the request of the Township. Increase in flows do not exceed 0.10 cfs and can be considered de minimus. Point of Analysis #3 Storm Event Existing Peak Proposed Peak Flow Rate (cfs) Flow Rate (cfs)* Current 2-year 0.09 0.13 Current 10-year 0.22 0.25 Current 100-year 0.53 0.52 Projected 2-year 0.13

0.22 0.25 Current 100-year 0.53 0.52 Projected 2-year 0.13 0.17 Projected 10-year 0.30 0.33 Projected 100-year 0.76 0.69 *Drainage area to POA #3 is reduced as a result of the development, however, a small increase in peak flows occurs due to the HSG D soils being utilized for the proposed condition while HSG B soils are utilized for calculations in the existing condition. Increase in flows are less than 0.05 cfs can be considered de minimus. 8. Water Quality Compliance In accordance with the West Orange Stormwater Control Ordinance, section 25-29.4.r.2(a), major developments are required to provide 80% TSS removal for the stormwater runoff from the net increase in motor vehicle surface. The project proposed a net decrease of motor vehicle surface of 0.009 acres (0.276 acres in the existing condition and 0.267 acres in the proposed condition) therefore water quality is not required, however, the proposed bioretention basin has been designed to treat 0.064 acres of motor vehicle surface in the proposed condition to 80% TSS removal. For reference, the project proposes a net increase in on-site impervious area of 0.04 acres. Mavis Tire Supply, LLC July 2025 DEC# 1956-24-04187 8 Last revised May 2026

9. Groundwater Recharge Compliance As determined by NJ GeoWeb Mapping, this project area falls within the Metropolitan Planning Area (PA1). Under existing conditions, the site is not covered in woody vegetation nor regrowth. In accordance with New Jersey Standard for Land Grading (revised 2017), non woody vegetated PA1 areas fall under the soil compaction exemption list as an "urban redevelopment" and is defined by NJDEP as "previously developed". Therefore, this project will not be subject to comply with ground water recharge requirements set forth in NJAC 7:8-5.4. 10. Storm Sewer Design The proposed stormwater management collection system has been designed to have hydraulic capacity for the 25-year storm event. The Rational Method was used to determine inflow rates to each structure and Manning’s Equation was used to establish pipe capacity. In accordance with the NJDEP BMP Manual Chapter 5, weighted runoff coefficients were computed for each drainage area based on land cover and hydrologic soil group. A minimum time of concentration of six minutes was assumed for each area. Supporting calculations and the Inlet Drainage Area Map can be found in the appendix. 11. Soil Erosion and Sediment Control Compliance The project has been designed to comply with the Standards for Soil Erosion and Sediment Control in New Jersey. Soil erosion control measures such as a stabilized construction entrance, inlet protection and silt fence are shown on the plans. In addition, the proposed basins and underground stormwater conveyance system discharge to existing stormwater infrastructure located on the site, therefore providing a stable point of discharge. 12. Conclusion The proposed development has been designed with provisions for the safe and efficient control of stormwater runoff in a manner that will not adversely impact the existing drainage patterns, adjacent roadways, or adjacent parcels. In addition, the proposed development satisfies the runoff quality and groundwater recharge requirements set forth by the Township of West Orange Land Use Ordinance and reduces the peak flow rates to the point of analysis to the maximum extent practical and in line with the intent of the regulations through the use of the proposed green infrastructure and underground detention. With this stated, it is evident that the proposed development will not have a negative impact on the

of the regulations through the use of the proposed green infrastructure and underground detention. With this stated, it is evident that the proposed development will not have a negative impact on the existing drainage conditions, water quality or groundwater recharge on-site or within the vicinity of the subject site. Mavis Tire Supply, LLC July 2025 DEC# 1956-24-04187 9 Last revised May 2026