Drainage Statement 07 2025 submission

DRAINAGE STATEMENT 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 DEC# 1956-24-04187

TABLE OF CONTENTS Section Page I. Introduction ....................................................................................... 1 II. Existing Pipe Capacity ...................................................................... 1 III. Drainage Summary ........................................................................... 1 APPENDIX • Aerial Photo Map • USGS Map • Pipe Sizing • Existing Inlet Drainage Area Map • Proposed Inlet Drainage Area Map

I. Introduction 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 (New Jersey State Highway #280), 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 6,952 SF (0.16 acres). The overall development will result in 0.04 acres (1,329 SF) of new impervious surfaces (inclusive of MVS)(less than 0.25 acres of impervious coverage increase), and 0.66 acres of land disturbance (less than 1 acre of disturbance). Moreover, the proposed development will reduce existing motor vehicle surfaces by approximately 670 SF. Additional site improvements include modifications to the associated parking areas, landscaping, lighting, signage, and utilities as reflected on the accompanying Site Plan drawings. II. Existing Pipe Capacity The subject site has been evaluated using the Manning’s Equation to understand the maximum flow capacity for each of the pipes proposed in the stormwater system. (1.49) 2/3 𝑄𝑄 = 𝐴𝐴𝐴𝐴 √𝑆𝑆 𝑛𝑛 Equation 1: Manning’s Equation This was determined by first approximating the maximum flow conveyed into the existing system from the 6” CIP line. The slope of the 6” CIP pipe, connecting from the adjacent property, cannot be verified from the property survey, however it can be assumed that capacity of the pipe cannot exceed the downstream pipe at 2.5% slope. The flow from this pipe (1.0 CFS utilized in calculations) has been

ified from the property survey, however it can be assumed that capacity of the pipe cannot exceed the downstream pipe at 2.5% slope. The flow from this pipe (1.0 CFS utilized in calculations) has been modeled in the attached Pipe Sizing calculations to demonstrate the proposed system has adequate capacity to convey the flow from the adjacent property, even when flowing at full capacity. III. Drainage Summary As a result of the proposed redevelopment, the overall impervious coverage onsite will increase from existing to proposed conditions by 4.7% (approximately 1,329 SF) and the limit of disturbance for proposed site improvements is approximately 0.66 acres. Mavis Tire Supply, LLC 1 July 2025 DEC# 1956-24-04187

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 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 proposed development has been designed to generally maintain similar drainage patterns as the existing condition. As shown on the Inlet 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. Pipe Sizing calculations have been provided in the Appendix of this report to demonstrate that the proposed pipes have adequate capacity to handle the anticipated flows generated by the 25-year storm event. The project does not result in greater than 1 acre of disturbance or create ¼ acre or more of new regulated impervious or motor vehicle surface; and therefore, the project is not subject to the stormwater management quantity, quality and recharge requirements set forth at NJAC 7:8. Further, due to the minimal increase in impervious coverage from existing to proposed conditions (with a reduction in motor vehicle surface), the proposed development will not significantly impact the existing drainage infrastructure located within the adjacent roadway or the surrounding properties. Mavis Tire Supply, LLC 2 July 2025 DEC# 1956-24-04187

APPENDIX

AERIAL PHOTO MAP

Aerial Photo Map (Not to scale) 5 Greentree Center, Suite 406, Marlton, NJ T. 856-334-2000 245 Main Street, Suite 110, Chester, NJ 07930 T. 908-879-9229 100 NE 5th Avenue, Suite B2, Delray Beach, FL 33483 T. 561-291-8570 8 Robbins Street, Suite 102, Toms River, NJ 08753 T. 732-974-0198 14521 Old Katy Road, Suite 270, Houston, TX 77079 T. 281-789-6400 826 Newtown Yardley Rd., Suite 201, Newtown, PA 18940 T. 267-685-0276 714 S. Greenville Avenue, Suite 100, Allen, TX 75002 T. 972-534-2100

USGS MAP

USGS Map (Not to scale) 5 Greentree Center, Suite 406, Marlton, NJ T. 856-334-2000 245 Main Street, Suite 110, Chester, NJ 07930 T. 908-879-9229 100 NE 5th Avenue, Suite B2, Delray Beach, FL 33483 T. 561-291-8570 8 Robbins Street, Suite 102, Toms River, NJ 08753 T. 732-974-0198 14521 Old Katy Road, Suite 270, Houston, TX 77079 T. 281-789-6400 826 Newtown Yardley Rd., Suite 201, Newtown, PA 18940 T. 267-685-0276 714 S. Greenville Avenue, Suite 100, Allen, TX 75002 T. 972-534-2100