Stormwater Management Report Revised as of 01282026 4936 0314 8685 v2

STORMWATER MANAGEMENT REPORT FOR Sofia By Gomes 525 Northfield Avenue Lot 1.01, Block 159.04 Township of West Orange Essex County, New Jersey Applicant 525 Northfield Ave., LLC 91 KOSSUTH STREET NEWARK, NJ 07105 pedro@bygomes.com ARCHITECTURE Prepared by ENGINEERING SPACE PLANNING Jarmel Kizel Architects & Engineers, Inc. INTERIOR DESIGN IMPLEMENTATION SERVICES PRINCIPALS MARVIN JARMEL, IIDA MATTHEW B. JARMEL, AIA, Jarmel Kizel Project No. GOMESGR24-223 MBA Dated: October 22, 2025 IRWIN H. KIZEL, AIA, PP RICHARD A. JARMEL, PE Revised January 28, 2026 NJ STATE BOARD OF ARCHITECTS CERTIFICATE OF AUTHORIZATION NUMBER 161 NJ STATE BOARD OF PROFESSIONAL ENGINEERS Anthony Facchino, PE, PLS AND LAND SURVEYORS CERTIFICATE OF Professional Engineer and Land Surveyor AUTHORIZATION NUMBER N.J. License No. GE042585 GA278177 42 Okner Parkway Livingston, NJ 07039 TEL: (973) 994-9669 FAX: (973) 994-4069 Signature www.jarmelkizel.com

Table of Contents Introduction .............................................................................................................. 3 Existing Site Conditions ........................................................................................ 3 Proposed Site Conditions ..................................................................................... 3 Groundwater Recharge ....................................................................................... 4 Water Quality Design .......................................................................................... 5 Water Quantity Design ........................................................................................ 5 Soil Erosion and Sediment Control Compliance ................................................. 8 Collection and Conveyance System Design ........................................................ 8 Conclusion............................................................................................................. 8 APPENDICES A. Existing Runoff Calculations B. Proposed Runoff Calculations C. Storm Sewer Capacity Calculations D. NRCS Soil Mapping Data E. Geotechnical Report F. Drainage area maps 2

Introduction The purpose of this report is to present the stormwater runoff calculations performed for this development and to demonstrate compliance with the Townships Code 25-29 on Stormwater Control and NJDEP Best Management Practices (BMP) specifically regarding the four (4) components of a major development: stormwater quantity, stormwater quality, groundwater recharge, and erosion control. The project site is located at 525 Northfield Avenue, and is the site of the Essex House restaurant. The property has been designated as Tax Lots 1.01, 1.02 and 1.03, Block 159.04 on the current Township Tax Maps. The site has a total land area of 2.530 acres. The site is located on the corner of Northfield Avenue and Sheridan Avenue in the B-2 zone district, and it backs up to Masson Place and Lenox Terrace. Across the street from the site is the Turtle Back Zoo and the South Mountain Arena in South Mountain Reservation. Existing Site Conditions The site is currently occupied by a two-story masonry building with a parking lot for approximately 171 cars. The site is bisected by a 72” diameter concrete culvert pipe that flows east to west. The site’s topography is such that the site receives off-site runoff from the residential properties to the northeast. Therefore, the drainage study considers a total area of 3.0609 acres. The site slopes considerably from the northeast corner, southwesterly toward the intersection of Northfield Avenue and Sheridan Avenue. The site has excessive slopes of approximately 50% along its northern boundary. These slopes terminate at the edge of the existing parking lot. The parking lot currently has an average slope of 5%. The site is currently composed of 69.2% impervious areas and 30.8% pervious areas. The pervious areas are, for the most part, located in the rear of the site. The vegetation in this area is mostly woods and shrubs. Access to the site is available from Northfield Avenue and Sheridan Avenue. There is no access to the site from Masson Place and Lenox Terrace because of the steep slopes in that section of the site. Proposed Site Conditions The proposed development requires to remove all existing building area, pavement, and site infrastructure for submission for preliminary and final site plans seeking approval to construct a multi-family 105-unit apartment building with an underground parking garage. The

, pavement, and site infrastructure for submission for preliminary and final site plans seeking approval to construct a multi-family 105-unit apartment building with an underground parking garage. The 52,940 square foot building will have (84) one-bedroom units, (16) two-bedroom units and (5) three- bedroom units. The building will also have 1,200sf retail space and 5,784sf of outdoor amenity area. The building will also have a total of (200) parking spaces. The existing property has a total land area of 110,205 square feet (2.53 acres). The proposed conditions will have a reduction in impervious coverage by 3,265sf. Please also note that the proposed 5,784sf of outdoor amenity space has been considered impervious area to provide a conservative approach to our stormwater design. The amenity space will have planter area to infiltrate and absorb runoff. In proposed conditions we are maintaining drainage patterns 3

as close to existing conditions as possible. Do to the fact that the proposal will disturbance more than 1/2 acre of land, causes the project to meet the definition of a “Major Development” under the State and local regulations Code 25-29. Soils From the Natural Resources Conservation Service, one soil type was found at the project site: BouB—Boonton substratum, 0 to 8 percent slopes. The soil is ranked with a hydraulic soil group C. For design purposes Hydrologic Soil Group C will be used for design comparison. Nonstructural Best Management Practices (Bmps) Stormwater management is an important aspect of the project, not only for the safety and convenience of potential residents, but for the environment as well. Thus, it has been endeavored to include various stormwater management techniques that include both natural and structural means to accomplish that task. The following low impact, nonstructural, development approaches to site design have been incorporated into this project as per Township code 25-29.4 and the NJDEP storm water management regulations 7:8-5.3; notably: 25-29.4(a) Land disturbance would be minimized by maintaining as much native vegetation around the site as possible. 25-29.4 (b) A Maintenance plan has been prepared to address ongoing maintenance of the project. NJDEP 7:8-5.3 (b) 6. Much of the proposed building area has been previously disturbed and/or filled. It is these areas where most of the contemplated soil compaction would take place in order to construct the new buildings, parking areas, and drives. In other locations that have not seen extensive disturbance, rubber tired vehicles would be used to minimize compaction. NJDEP 7:8-5.3 (b) 7. Extensive, supplemental landscaping would be added throughout the project site in the form of trees, shrubs, and ground cover. Groundwater Recharge This section of the report describes the groundwater recharge provisions of the stormwater management system’s design. The site falls within the State’s Planning Area 1 (Metropolitan) and therefore the site can be considered as part of the urban redevelopment area. This groundwater recharge requirement does not apply to areas of the project that have been previously developed. Consequently, pursuant to 25-29.4 (q)3 and NJAC 7:8-5.4(b)2 the 4

groundwater recharge requirements do not apply to this development. The reduction in impervious coverage would likely allow groundwater infiltration. Water Quality Management As stated previously, since the project does not increase impervious cover by more than 0.25 acres (impervious cover is reduced in the proposed condition), the site does not drain to a water that has a total maximum daily load (TMDL) for TSS reduction, the regulatory requirements of the Code 25-29.4(r) and NJAC 7:8-5.5 are not applicable. Nevertheless, we believe implementation of the project will result in an improvement of runoff quality, when compared to existing site conditions and former use of the property. The anticipated improvement in water quality is based upon the net reduction in impervious cover, as well as a higher percentage of the post-project cover being comprised of mainly roof areas consisting of 52,940 square feet. The NJDEP considers roof runoff “clean,” not requiring TSS removal pursuant to State regulation. Hydrology And Stormwater Management Quantity Control (Peak Flow Attenuation) Estimating runoff rates and volumes for quantity control purposes is done by utilizing what is referred to as the “NRCS Method”, which is also known as the “TR-55” methodology. This is described at length in Chapter 5 of the BMP Manual According to the National Engineering Handbook, as published by the NRCS, the combination of a hydrologic soil group and a land use and treatment class is a hydrologic soil-cover complex, to which a runoff curve number (CN) can be assigned. The CN is an indication of the complex’s runoff potential. The Hydrologic Soil Group(s) for the project site were determined by referencing the NRCS’s Web Soil Survey for the appropriate county. The Time of Concentration, “Tc”, for the existing and the proposed conditions have been calculated through modeling software and the paths are shown on the coverage maps. For the various ground covers, runoff coefficients, “CN”, used in the analysis were 98 for impervious areas such as buildings, parking lot, and walkways, and 71-74 for wooded/landscape areas. The rainfall depths utilized for the project’s design were derived from NOAA Atlas 14, Volume 2, Version 3 point precipitation frequency estimates. An adjustment factor increasing the runoff factor by 1%-6% was applied in per 54 NJR 2187(a) for current

n were derived from NOAA Atlas 14, Volume 2, Version 3 point precipitation frequency estimates. An adjustment factor increasing the runoff factor by 1%-6% was applied in per 54 NJR 2187(a) for current storms and another 23% to 46% was added to arrive at a “future” storm intensity. Below is a summary of the storm rainfall depths used for both the existing and proposed conditions. 5

Storm 2-year 10-year 100-year Current-Year-2020 3.47 in 5.38 in 9.18 in Future-Year-2050 4.09 in 6.37 in 11.52 in. The project’s approach for compliance with the regulatory requirements for “quantity control” are set forth at Township Code 25-29.4(s) and Subpart 5.6(b)(2) of the Stormwater Management Regulations (NJAC 7:8), specifically “Demonstrate through hydrologic and hydraulic analysis that there is no increase, as compared to the pre-construction condition, in the peak runoff rates of stormwater leaving the site for the current and projected two-, ten-, and 100-year storm events, as defined and determined pursuant to § 25-29.5c and d, respectively, of this section, and that the increased volume or change in timing of stormwater runoff will not increase flood damage at or downstream of the site. This analysis shall include the analysis of impacts of existing land uses and projected land uses assuming full development under existing zoning and land use ordinances in the drainage area;” As the project is divided into two primary drainage areas with two design points, quantity control considerations are evaluated for each design point. The TR-55 calculations provided in Appendix No. A and Appendix No. B indicate the total peak runoff and total runoff volumes from the subject drainage areas under pre-project and post- project conditions respectively. Tables below provide a summary of the peak runoff rates and total runoff volumes for the regulated storms under existing and proposed conditions for both design points and the overall site, respectively. The following data verifies the project’s compliance with the standards pertaining to “quantity control” as the peak runoff rates for post- project conditions never exceed the pre-project conditions. There is no increase in volume for post-conditions because we were able to maintain drainage areas with the use of roof drains, therefore, we will not increase flood damage at or downstream of the site. Our site currently connects to an existing 72” culvert pipe and a storm sewer system on Sheridan Avenue which will safely convey the runoff and minimize erosion. 6

Table No. 1 Design Point #1 Storm Freq. Runoff Rates (cfs) Total Volume Runoff (cf) PRE POST PRE POST 2-Year(2020) 3.42 3.38 23,157 23,111 10-Year(2020) 5.82 5.75 39,692 39,645 100-Year(2020) 10.83 10.67 74,476 74,356 2-Year(2050) 4.21 4.17 28,405 28,362 10-Year(2050) 7.17 7.08 48,587 48,528 100-Year(2050) 14.10 13.89 96,456 96,261 Table No. 2 Design Point #2 Storm Freq. Runoff Rates (cfs) Total Volume Runoff (cf) PRE POST PRE POST 2-Year(2020) 0.61 0.52 3,919 3,361 10-Year(2020) 0.99 0.91 6,436 5,818 100-Year(2020) 1.77 1.71 11,573 10,992 2-Year(2050) 0.73 0.65 4,727 4,140 10-Year(2050) 1.20 1.12 7,763 7,141 100-Year(2050) 2.26 2.22 14,774 14,261 Table No. 3 Overall Site (Total) Storm Freq. Runoff Rates (cfs) Total Volume Runoff (cf) PRE POST PRE POST 2-Year(2020) 4.03 3.90 27,076 26,472 10-Year(2020) 6.82 6.65 46,128 45,463 100-Year(2020) 12.60 12.38 86,050 85,348 2-Year(2050) 4.95 4.81 33,132 32,502 10-Year(2050) 8.36 8.20 56,350 55,669 100-Year(2050) 16.35 16.11 111,230 110,523 7

5. Soil Erosion and Sediment Control Compliance The project has also been designed to minimize erosion and sedimentation in accordance with The Standards for Soil Erosion and Sediment Control in New Jersey”. “Soil Erosion and Sediment Control Plan” is included in the set of project plans, specifying numerous practices to achieve this goal. The project’s “Soil Erosion and Sediment Control Plan” is subject to review and approval by the Hudson Essex Passaic Soil Conservation District (HEPSCD). The District’s certification of the plan is required before any construction may commence, which provides further assurance that the project’s implementation will minimize erosion and sedimentation. 6. Collection and Conveyance System Design The project’s storm water management system also includes a network of storm sewer pipes to convey the stormwater runoff to and from the various management facilities. Similarly, stormwater inlets are strategically located to collect runoff from the surface of the ground. The collection and conveyance systems (storm sewers) were designed for the peak rate of runoff during a 100-year storm calculated per the Rational Method. Appendix No. C of this report contains the storm sewer design calculations. The Proposed Inlet Area Map presents the inlet drainage areas for each proposed inlet collecting roof runoff via downspout leaders. There are multiple storm sewers systems proposed: system B-F encompasses Proposed Drainage Area to mimic existing condition drainage patterns. Conclusion The proposed improvements are designed in accordance with local, county and state standards as specified herein. The measures and design provided herein are intended to prevent or limit the impact of the proposed development on the site and the surrounding areas with respect to stormwater quantity, quality, groundwater recharge, and erosion from stormwater runoff. The proposed project will not increase impervious surfaces within the property in question and will provide peak flow attenuation by reducing the peak flow and volume as compared to existing conditions. As per the requirements for a major site development, there is a reduction in the existing peak runoff rates and volumes for stormwater leaving the site for the 2, 10, and 100-year storm events at each design point respectively. It is our opinion that the calculations provided and summarized