2025 12 08_West Orange SMP Memorandum

Stormwater Management Plan Memorandum Public Service Electric and Gas Company West Orange 26kV Switching Station Project No. 144507 Revision A 12/8/2025

Stormwater Management Plan Memorandum prepared for Public Service Electric and Gas Company West Orange 26kV Switching Station West Orange, New Jersey Project No. 144507 Revision A 12/8/2025 prepared by Burns & McDonnell Engineering Company, Inc. Kansas City, Missouri COPYRIGHT © 2025 BURNS & McDONNELL ENGINEERING COMPANY, INC.

Stormwater Management Plan Memorandum Revision A Table of Contents TABLE OF CONTENTS Page No. 1.0 SITE CONDITIONS ........................................................................................... 1-1 1.1 Site Description .................................................................................................... 1-1 2.0 HYDROLOGY AND HYDRAULICS .................................................................. 2-1 2.1 Rainfall Data ........................................................................................................ 2-1 2.2 Runoff Data .......................................................................................................... 2-1 2.3 Stormwater Management Facilities ..................................................................... 2-2 2.4 Results .................................................................................................................. 2-3 3.0 SOIL EROSION AND SEDIMENT CONTROL MEASURES ............................ 3-1 4.0 CONCLUSIONS ................................................................................................ 4-1 EXHIBITS Exhibit A: Pre-Developed Watershed Plan Exhibit B: Post-Developed Watershed Plan Public Service Electric & Gas Company TOC-1 Burns & McDonnell

Stormwater Management Plan Memorandum 1.0 1.1 Revision A Site Conditions SITE CONDITIONS Site Description Public Service Electric and Gas Company (PSE&G) proposes to expand the existing West Orange 26kV switching station, located in West Orange, Essex County, New Jersey. The property is designated by West Orange as Block 155, Lot 26.01 in the City of West Orange, New Jersey, which encompasses a total of 23.57 acres (refer to Figure 1-1 for the project’s general vicinity map). The site is located at the corner of Prospect Avenue and Mt Pleasant Avenue. One access point to the station will be reconstructed at the south side of the station from Mt Pleasant Avenue. The expansion of the switching station, including the fence replacement, utility connections, and driveway updates, has an overall project disturbance of approximately 3.92 acres. Public Service Electric & Gas Company TOC-1-1 Burns & McDonnell

Stormwater Management Plan Memorandum 2.0 2.1 Revision A Hydrology and Hydraulics HYDROLOGY AND HYDRAULICS Rainfall Data Per the updated N.J.A.C. 7:8 regulations effective July 17, 2023, the Essex County adjustment factor is applied for both the current and future precipitation depth values for the 2-, 10-, and 100-year return frequencies used for stormwater design. Table 2.1: Design Storm Frequency with Depth Precipitation Adjustment Factors (AF) Return Frequency (yr) Water Quality (WQ) 2 10 100 NOAA Atlas 14 (in) 1.25a 3.42 5.20 8.71 24 Hour Depth Current Current Future Adjusted AF AF (in) Future Adjusted (in) 1.01 1.03 1.06 4.07 6.36 11.58 3.45 5.37 9.23 1.19 1.22 1.33 a N.J.A.C. 7:8-5.5 requires the WQv storm to be 1.25 inches of rainfall in two hours. 2.2 Runoff Data HydroCAD-10 software was utilized to model the stormwater runoff by the SCS TR-55 methodology to calculate the pre- and post-developed runoff rates. Table 2.2 provides detailed information regarding curve numbers and land coverages for pre- and post-developed watersheds, respectively. Table 2.2: Land Coverages Land Coverage CN HSG Pre-Development Impervious, Pavement 98 D >75% Grass cover, Good 80 D Yard Stone/Gravel Pad 85 D Brush, Good 73 D Non-Contributory* 73-85 D Post-Development Impervious, Pavement 98 D >75% Grass cover, Good 80 D Yard Stone/Gravel Pad 85 D Brush, Good 73 D Non-Contributory* 73-85 D Area (acres) 0.973 1.345 1.926 1.261 1.411 1.373 2.102 2.003 0.000 1.438 *Non-Contributory refers to areas that do not contribute to Underground Detention or the existing Aquashield system. Non-Contributory areas include the grassed slope areas and the transformer containment pits. Public Service Electric & Gas Company TOC-2-1 Burns & McDonnell

Stormwater Management Plan Memorandum 2.3 Revision A Hydrology and Hydraulics Stormwater Management Facilities This project is considered a major development but is only required to address stormwater quantity and quality. A modular underground detention basin is proposed to mitigate the effects of higher runoff rates from the proposed switching station expansion. Stormwater will be routed to the underground detention basin via a 4 foot wide flat bottom grass swale running along the east edge of the switching station, discharging into a catch basin and through a stormwater pipe network. Stormwater quality will be addressed via the use of the grass swale BMP. To prevent the non-contributory area drainage from reaching the switching station, and impacting the stormwater detention basin quantity control, an additional trench drain is proposed to the east of the grass swale. This trench drain will be connected to separate stormwater pipe network and shall connect to the existing stormwater infrastructure located within Mount Pleasant Avenue. The underground detention basin is designed to attenuate the post-construction peak runoff rates for the current and future 2-, 10- and 100-year storm events to rates that are less than 50%, 75% and 80%, respectively, of the pre-construction peak runoff rates as shown in Table 2.3 below. Table 2.3: Underground Detention System Discharge Return Frequency (yr) Inflow (cfs) Discharge (cfs) Stage Elevation (ft) WQ 1.59 0.17 591.17 2 (Current) 3.14 0.64 592.14 2 (Future) 4.07 1.48 592.29 10 (Current) 5.61 3.66 592.59 10 (Future) 7.14 4.92 592.85 100 (Current) 10.65 7.15 593.55 100 (Future) 14.18 8.71 594.19 Max Available Storage (cf) Bottom of Underground Detention Elevation (ft) 32,340 590.00 Table 2.4: Underground Detention Control Devices Outlet Control Structure Name CS-01 Public Service Electric & Gas Company Control Device Outlets (1) – 18” Concrete Pipe @ 590.00’ (1) – 2.5” Circular Orifice @ 590.00’ (1) – 30”W x 6”H Rectangular Orifice @ 592.00’ TOC-2-2 Burns & McDonnell

Stormwater Management Plan Memorandum 2.4 Revision A Hydrology and Hydraulics Results The post-developed watersheds PO-DA A and PO-DA I, which discharge into the existing onsite stormwater pipe network that drains to the AquaShield, will be a reduction in size from the pre-developed watersheds PO-DA 6 and PO-DA 8, thus providing no adverse impact to the original AquaShield design or outfall. As summarized in Section 2.3, an underground detention basin will be utilized to address the water quantity for the peak discharge for the newly developed areas associated with the switching station expansion, specifically post-developed watersheds PO-DA C, PO-DA D, PO-DA E, PO-DA F, and PODA H. The peak post-developed runoff rates do not exceed the peak pre-developed runoff rates for 50% of the 2-year, 75% of the 10-year, and 80% of the 100-year storm events. Runoff from the noncontributory post-developed watershed PO-DA J drains to the same outfall, O-2, as pre-developed watershed PO-DA 1 and should result in minimal change of the peak flowrates. Table 2.5 below summarizes the stormwater flow conditions for the project. Table 2.5: Site Flow Results Pre Q(2-YR) Current (cfs) 4.09 3.60<4.09 OK 2.09 Q(2-YR) Future (cfs) 5.27 4.62<5.27 OK 2.84 Q(10-YR) Current (cfs) 7.37 6.46<7.37 OK 4.20 Q(10-YR) Future (cfs) 9.33 8.15<9.33 OK 5.49 Q(100-YR) Current (cfs) 14.11 12.29<14.11 OK 8.61 Q(100-YR) Future (cfs) 18.67 16.20<18.67 OK 11.65 Post 2.09 2.84 4.20 5.49 8.61 11.65 Outfall Discharge Point O-AquaShield (PO-DA 6 / A, DA 8 / I) O-1A (PO-DA B, PODA G) O-1Bb (Detention Basin Areas (PO-DA 7 / C, D, E, F, H)) Pre Post 2.66*50% = 3.49*50% = 5.20*75% = 6.61*75% = 10.52*80% = 13.89*80% = 1.33 1.75 3.90 4.96 8.42 11.11 0.64<1.33 1.48<1.75 3.66<3.90 4.92<4.96 7.15<8.42 8.71<11.11 Post OK OK OK OK OK OK Pre 2.45 3.19 4.81 6.07 9.80 12.86 O-2 2.36<2.45 3.10<3.19 4.48<4.81 5.72<6.07 8.86<9.80 11.77<12.86 (PO-DA 1 / J) Post OK OK OK OK OK OK b N.J.A.C. 7:8-5.6 requires post-construction peak runoff rates for the 2-, 10-, and 100-year storm events to be 50%, 75%, and 80%, respectively, of the pre-construction peak runoff rates. Pre Public Service Electric & Gas Company TOC-2-3 Burns & McDonnell

Stormwater Management Plan Memorandum 3.0 Revision A Soil Erosion and Sediment Control Measures SOIL EROSION AND SEDIMENT CONTROL MEASURES A soil erosion and sediment control plan and associated details have been developed to control sediment during construction activities. Silt sock and/or silt fence will be installed around the perimeter of the areas to be disturbed prior to beginning construction. Newly graded areas will be stabilized with erosion control blanket during construction, and the project entrance will be stabilized with 1.5” to 2.5” stone tracking pads. Filter protection will be provided at existing and proposed inlets to minimize sediment from entering the subsurface storm drainage system. Upon completion of earthwork activities, the station yard within the fenced area will be rocked with a sacrificial rock working surface to temporarily stabilize the site. Public Service Electric & Gas Company TOC-3-1 Burns & McDonnell

Stormwater Management Plan Memorandum 4.0 Revision A Conclusions CONCLUSIONS Because this project disturbs more than one acre, it is classified as a Major Development. However, as it is located within an urban redevelopment area, the project is not required to provide groundwater recharge. The underground detention basin system will address the stormwater quantity requirements while the grass swale addresses stormwater quality. Eventually, the treated stormwater is to be released into the existing municipal storm drain infrastructure, located within Mount Pleasant Avenue. There is no anticipated adverse impact to the public or private lands adjacent to the site. Temporary on-site erosion control measures have been designed in accordance with the New Jersey Department of Environmental Protection’s standards set forth in the New Jersey Stormwater BMP Manual and the New Jersey Department of Agriculture’s Standards for Soil Erosion and Sediment Control. Public Service Electric & Gas Company TOC-4-1 Burns & McDonnell

EXHIBIT A - PRE-DEVELOPED WATERSHED PLAN