09 Stormwater Mgmt Report 122025

Introduction The subject property is located at 457 Mount Pleasant Avenue in the Township of West Orange, Essex County, New Jersey. The property is identified as Block 157, Lot 5 on the Township of West Orange tax maps and is a total of 3.71 acres in size and will hereafter be referred to as “the site”. The site is bordered to the north by Mount Pleasant Place with residential properties and a Township Fire Department building beyond; to the east by residential properties and Mount Pleasant Place, to the west by Exxon Gas Station, the Rahway River, Pleasant Valley Way, and Trojan Self Storage with residential properties beyond; and to the south by Mount Pleasant Ave with Francis A. Byrne golf course beyond. A tax map and aerial map are included at the beginning of Appendix F for reference. The site is currently an existing shopping center within the B-2 Zone. The proposed development consists of converting the existing florist footprint within the shopping center to a proposed retail store with ancillary sidewalks and parking reconfiguration. While this project proposes a decrease in total impervious surface, an increase less than 0.25 acres of regulated motor vehicle surface area, and disturbs less than 1 acre, this project is a major development due to the Township of West Orange Ordinance 2918-25, adopted May 20, 2025. Based on the Township Ordinance, a “Major Development” means an individual “development,” including redevelopment, as well as multiple developments that individually or collectively result in: 1. The disturbance of 0.5 acres of land since February 2, 2004. 2. The creation of 5,000 SF or more of “regulated impervious surface” since February 2, 2004. 3. The creation of 5,000 SF or more of “regulated motor vehicle surface” since March 2, 2021, or 4. A combination of 2 and 3 above that totals an area of 5,000 SF or more. The same surface shall not be counted twice when determining if the combination area equals one-quarter acre or more. The proposed project will disturb more than 0.5 acres of land and create more than 5,000 SF of regulated motor vehicle surface. Therefore, the proposed project will be required to comply with the Township requirements for water quality and quantity treatment. The site is previously disturbed and located in Planning Area-1, therefore recharge requirements will not apply. This report summarizes the design

equirements for water quality and quantity treatment. The site is previously disturbed and located in Planning Area-1, therefore recharge requirements will not apply. This report summarizes the design objectives, methodology, and calculations for the conveyance, attenuation, and discharge of stormwater runoff leaving the site and is meant to accompany the Site Plan documents prepared by Bohler. Pre-development and post-development conditions are examined for analysis of the stormwater quantity, water quality, and groundwater recharge based on the NJDEP Stormwater Management Regulations (NJAC 7:8) and soil erosion and sediment control based on The Standards for Soil Erosion and Sediment Control in New Jersey. Stormwater Management Design Methodology In accordance with the NJDEP Stormwater Management Regulations, the proposed development must meet the requirements, if appropriate, for stormwater quantity reductions, water quality, groundwater recharge, etc. The assessment of stormwater runoff has been based upon the Soil Conservation Service Method (SCS) Unit Hydrograph as described in Chapters 7, 9, 10, 15 and 16, Part 630 Hydrology, National Engineering Handbook (NEH) (previously described in Technical ▪ Stormwater Management Report for Proposed Retail Store▪ 1 ▪ December 2025 ▪