2026 05 Storm Water Management Report rcd 5 6 2026

STORMWATER MANAGEMENT, WATER QUALITY AND GROUNDWATER RECHARGE ANALYSIS For Mavis Tire Supply, LLC Proposed Automotive Service and Retail Center Block 105, Lot 64.01 460 Prospect Avenue Township of West Orange, Essex County, NJ Prepared by: 5 Greentree Centre, Suite 406 Marlton, NJ 08053 (856) 334-2000 Rodman R. Ritchie, PE, PP NJ Professional Engineer License #43547 July 2025 Last Revised May 2026 DEC# 1956-24-04187

TABLE OF CONTENTS Page No. 1. Site Description & Project Overview ..............................................1 2. Design Methodology .....................................................................1 3. Existing Drainage Conditions ........................................................2 4. Proposed Drainage Conditions .....................................................4 5. Stormwater Management System Design .....................................6 6. Green Infrastructure Compliance ..................................................7 7. Water Quantity Control Compliance ..............................................7 8. Water Quality Compliance ............................................................8 9. Groundwater Recharge Compliance .............................................9 10. Storm Sewer Design .....................................................................9 11. Soil Erosion and Sediment Control Compliance ............................9 12. Conclusion ....................................................................................9 APPENDIX • NRCS Web Soil Survey • Existing Conditions Hydrology – Current & Projected 2, 10, & 100 yr. • Proposed Conditions Hydrology – Current & Projected 2, 10, & 100 yr. • Water Quality Calculations • Stormwater Collection System Calculations (Pipe Sizing) • Basin Drain Time Calculations • Riprap Stability Calculations • Results of Test Pit Excavation and Infiltration Testing – Prepared by ECS • Drainage Area Maps

1. Site Description & Project Overview This Drainage Statement has been prepared to analyze the stormwater drainage conditions that would occur as a result of the redevelopment of Block 105, Lot 64.01, located in the Township of West Orange, Essex County, New Jersey. The analysis contained within this Drainage Statement is limited to the proposed area of disturbance. According to the Township of West Orange Zoning Map, the site is located in the (B-2) General Business District. The proposed property consists of 0.74 acres (+/-32,118 SF) and is located on Prospect Avenue (County Route #677), West Orange Township. The site is currently developed with an existing realtor’s office consisting of a two (2) story building, parking, sidewalks, lighting and other site amenities. The proposed project will replace the existing 3,338 SF (GFA) building east of Prospect Avenue to be redeveloped with an Automative Service and Retail Center. The proposed building will include a total footprint of approximately 6,205 SF. The overall development will result in approximately 0.04 acres of new impervious surfaces and approximately 0.8 acres of land disturbance. Moreover, the proposed development will reduce existing motor vehicle surfaces by approximately 0.009 acres. Additional site improvements include modifications to the associated parking areas, landscaping, lighting, signage, and utilities as reflected on the accompanying Site Plan drawings. 2. Design Methodology This report has been prepared to define and analyze the stormwater drainage conditions that would occur as a result of the development of the subject site. Based upon the fact that the proposed development will result in more than 0.5 acres of land disturbance, this project is classified as a “major development” as defined in Township of West Orange Land Use Ordinance § 25-29.2. However, based upon the fact that the proposed development will not result in more than one (1) acre of land disturbance, increase impervious coverage by more than ¼ acre, and increase motor vehicle surfaces by more than ¼ acre, this project is not classified as a “major development” as defined in NJAC 7:8. Although not defined as a major development, the proposed development has been designed to meet the stormwater runoff quantity, quality, and groundwater recharge standards, as set forth by the Township of West Orange Land Use

major development, the proposed development has been designed to meet the stormwater runoff quantity, quality, and groundwater recharge standards, as set forth by the Township of West Orange Land Use Ordinance (§ 25-29) and NJAC 7:8. The following documents and data were used in the support of the design of the project: • ALTA/NSPS Land Title Survey, prepared by Dynamic Survey, LLC, dated 12/04/2024, last revised 12/17/2024 • Preliminary & Final Site Plans, prepped by our office, dated 07/16/2025, last revised 02/13/2026 • Test Pit Excavation and Infiltration Testing Report, prepared by ECS, dated 01/29/2025 • NRCS Soil Survey • NJDEP Stormwater Management Best Management Practices Manual Mavis Tire Supply, LLC July 2025 DEC# 1956-24-04187 1 Last revised May 2026

The hydrology for the site was calculated using the NRCS Runoff Equation and Dimensionless Unit Hydrograph as noted in Part 630, Hydrology National Engineering Handbook. The following particular references were used: • Curve Numbers were established via Chapter 9 – Hydrologic Soil-Cover Complexes • Time of Concentrations were calculated in accordance with Chapter 15 • Rainfall Distributions are based on NOAA Type D rainfall distribution • The Standard Unit Hydrograph was utilized • The rainfall depths are based on Essex County NOAA Atlas 14 Data and adjusted per NJAC 7:8-5.7 Tables 5-5 and 5-6 as noted below: Return Period Current Adjusted Projected Adjusted Rainfall Depth Rainfall Depth (inches) (inches) 2 Year Storm 3.47 4.09 10 Year Storm 5.38 6.37 100 Year Storm 9.18 11.52 Based upon the Essex County Soil Survey, the soil types native to the site include: Soil Type Soil Type Name Hydrologic Soil Group USBONB Urban Land, Boonton Substratum Unrated* *When the hydrologic soil group (HSG) is unrated for a particular soil, the stormwater design shall assume HSG B for existing conditions and HSG D for proposed conditions for projects located outside the Coastal Plain. Based on the methodology and data noted above a hydrologic evaluation of the NJDEP Water Quality, 2, 10, and 100-year storm events was prepared. This report will address compliance with the following standards: • West Orange Township Stormwater Control Standards (§ 25-29) 3. Existing Drainage Conditions The area to be analyzed consists of approximately 0.681 acres and is comprised of the existing building, parking lot, and associated lawn areas within the limit of disturbance. In the existing condition, stormwater runoff is conveyed overland to five (5) separate inlets. The two yard inlets and two inlets within and surrounding the existing parking lot captures the majority of the

existing condition, stormwater runoff is conveyed overland to five (5) separate inlets. The two yard inlets and two inlets within and surrounding the existing parking lot captures the majority of the on-site runoff, ultimately discharging offsite through the existing 15” RCP stormwater line. The round inlet within the existing entrance on Blueberry Bend captures runoff from the adjacent properties, also ultimately discharging to the northeast offsite. The subject site has been Mavis Tire Supply, LLC July 2025 DEC# 1956-24-04187 2 Last revised May 2026

evaluated with the following drainage sub-watershed areas as depicted on the Existing Drainage Area Map included in the Appendix of this report. Point of Analysis #1 Study Area 1: This area consists of 0.534 acres which include roof, motor vehicle surfaces, impervious and grass areas. Under existing conditions, stormwater runoff generated by this area flows to the five (5) on-site inlets, as depicted on the Existing Inlet Area Map. Existing Conditions Input Summary Table Drainage Area Name Drainage Area Time of Curve Number (acres) Concentration (CN) (minutes) EDA 1 - Impervious 0.377 Ac 1.6 98 EDA 1 - Pervious 0.157 Ac 4.5 61 Existing 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 1.44 2.41 4.45 1.75 2.94 5.76 Point of Analysis #2 Study Area 2: This area consists of 0.044 acres which include the portion of the area to be developed which drains to Prospect Avenue. Under existing conditions, stormwater runoff generated by this area flows overland to the right-of-way, as depicted on the Existing Drainage Area Map. Existing Conditions Input Summary Table Drainage Area Name Drainage Area Time of Curve Number (acres) Concentration (CN) (minutes) EDA 2 - Impervious 0.015 Ac 0.8 98 EDA 2 - Pervious 0.029 Ac 4.1 61 Existing 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

d Adjusted Rainfall Area Conditions Conditions Name Q2 (CFS) Q10 (CFS) Q100 (CFS) Q2 (CFS) Q10 (CFS) Q100 (CFS) POI #2 0.07 0.14 0.30 0.09 0.18 0.41 Mavis Tire Supply, LLC July 2025 DEC# 1956-24-04187 3 Last revised May 2026

Point of Analysis #3 Study Area 3: This area consists of 0.103 acres which includes sidewalks and lawn area that sheet flows to the northeast corner of the site and is not collected by the onsite stormwater conveyance system. Existing Conditions Input Summary Table Drainage Area Name Drainage Area Time of Curve Number (acres) Concentration (CN) (minutes) EDA 3 - Impervious 0.019 Ac 8.1 98 EDA 3 - Pervious 0.084 Ac 8.6 61 Existing 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 0.09 0.22 0.53 0.13 0.30 0.76 4. Proposed Drainage Conditions The proposed development has been designed to generally maintain similar drainage patterns as the existing condition. As shown on the Proposed Drainage Area Map in the Appendix of this report, the majority of the stormwater runoff for the proposed development will be captured by the proposed inlets and yard drains and conveyed to the same offsite region as in the existing condition. Moreover, the proposed development will incorporate a small bio-retention basin to the west of the proposed building along the site frontage, and an underground pipe storage detention basin to the north of the proposed building along the northern property line for stormwater management. The basins are designed to detain stormwater runoff generated by the development to meet the stormwater management requirements. The proposed site conditions have been evaluated using the following drainage sub-watershed areas as depicted on the Proposed Drainage Area Map included in the Appendix of this report. Point of Analysis #1 To On-Site Conveyance System: This area consists of 0.275 acres and includes motor vehicle surfaces, impervious and grass areas throughout the site. Under proposed conditions runoff generated by this area sheet flows into the proposed storm conveyance system and

s and includes motor vehicle surfaces, impervious and grass areas throughout the site. Under proposed conditions runoff generated by this area sheet flows into the proposed storm conveyance system and discharges in the same location under existing conditions. 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. Mavis Tire Supply, LLC July 2025 DEC# 1956-24-04187 4 Last revised May 2026