09 Stormwater Mgmt Report 122025

ult in a reduction of approximately 0.07 acres of impervious coverage on the site in the post-development condition. The Proposed Drainage Area Map in Appendix F illustrates the limits of the proposed drainage area and how it relates to the proposed site conditions 4.1 Point of Analysis #1 The drainage area in the post development condition flows to the same Point of Analysis #1 identified in the existing condition, located along the western property line. The proposed runoff to Point of Analysis #1 meets the stormwater management criteria set forth in NJDEP Stormwater Management Regulations by having the post-construction hydrograph not exceed the pre-construction hydrograph at any point for the two-, 10-, and 100-year storm events. Refer to Section 4.3 Stormwater Quantity Controls for a summary of the preconstruction, allowable, and post-construction flows. ▪ Stormwater Management Report for Proposed Retail Store▪ 4 ▪ December 2025 ▪

4.1.1 Proposed Drainage Area #1 Proposed Drainage Area #1 consists of approximately 1.96 acres of land, of which 1.87 acres are impervious surface, and includes the proposed portion of the building to be repurposed for retail, parking fields, sidewalks, driveways, and stormwater infrastructure. The drainage area also contains grass and landscape areas. The runoff from Proposed Drainage Area #1 flows to Rahway River, and the existing inlet along Mount Pleasant Place, which ultimately reaches Point of Analysis #1. 4.2 Stormwater Quantity Controls The following stormwater quantity standard technique from the NJDEP Stormwater Management Regulations is being applied to the drainage area as noted in Section 4.1: 1. For stormwater runoff leaving the site, the post-development runoff hydrographs for the current and future/projected 2-, 10-, and 100-year storms do not exceed, at any point in time, the pre-development runoff hydrographs for the same storm events. This technique will be applied to drainage areas that, under proposed conditions, will remain unchanged or have a net decrease in impervious coverage. Table 4.1 - Point of Analysis #1 Existing vs. Proposed Comparison Current Adjusted Precipitation Depths (Add tables for additional drainage areas as required) Existing Proposed Peak Flow Peak Flow CFS CFS 2-Year Storm 6.36 5.78 10-Year Storm 9.92 9.16 100-Year Storm 16.99 15.85 See Appendix A for Comparison Hydrographs. Table 4.2 - Point of Analysis #1 Existing vs. Proposed Comparison Future Adjusted Precipitation Depths Existing Peak Flow Proposed Peak Flow CFS CFS 2-Year Storm 7.52 6.91 10-Year Storm 11.76 10.89 100-Year Storm 21.36 20.04 See Appendix B for Comparison Hydrographs. ▪ Stormwater Management Report for Proposed Retail Store▪ 5 ▪ December 2025 ▪

4.3 Water Quality Controls As stated in the NJDEP Stormwater Management Regulations, the stormwater runoff quality standards are applicable when the development proposes an increase of one-quarter acre (10,890 square-feet) or more of regulated motor vehicle surfaces. The proposed development of the site will result in 0.18 acres (7,999 square-feet) of new motor vehicle surfaces. However, based on the West Orange Township Ordinance 2918-25 mentioned above in Section 1, 80% of the total suspended solids (TSS) must be removed for the net increase in motor vehicle surface. In order to satisfy this requirement, a pervious pavement system is proposed to treat 0.27 AC (11,639 SF). Motor Vehicle Surface Areas on site: Existing Motor Vehicle Surface Area: 1.96 Acres Proposed Motor Vehicle Surface Area: 2.14 Acres Net Increase in Motor Vehicle Surface Area: 2.14 Acres – 1.96 Acres = 0.18 Acres Required: Net Increase in Motor Vehicle Surface Area – 80% TSS Removal Treatment required [80% (0.18 Acres)] / 2.14 Acres = 6.72% Proposed: [80% (0.27 Acres)] / 2.14 Acres = 10.09% 10.09% Weighted Proposed TSS Removal Rate > 6.72% Required TSS Removal Rate As calculated the proposed weighted TSS removal rate is greater than the required rate; the project, as designed, meets the water quality requirement for the proposed development. 4.3.1 Pervious Paving Systems Pervious paving materials have been proposed as part of the overall site design and stormwater management system to reduce the impervious surface on site, provide 80% TSS removal for motor vehicle surfaces, and reduce the flow of runoff. The pervious paving systems have been designed to have a maximum ratio of additional inflow area to the pavement surface area of less than 3:1, a maximum surface slope of 5%, a storage bed that fully contains the water quality design storm runoff volume, and to discharge the design storm within 72 hours of a rain event. ▪ Stormwater Management Report for Proposed Retail Store▪ 6 ▪ December 2025 ▪

Table 4.3 - Pervious Paving Systems Summary Pervious Paving 1 System # 5.1 Pervious Area (Acres) 0.20 Additional Drainage Area (Acres) 0.07 Drainage Area Ratio 0.35:1 Surface Slope (%) 2 Underdrain Size (Inches) 6 Drain Time (Hours) 0.9 (WQ) 9.4 (100-Year Future Adj. Storm) Groundwater Recharge The subject site has been previously developed and is located within the Metropolitan Planning Area (PA1). As such, the site falls under the NJDEP’s definition for an urban redevelopment area and this project will result in a decrease in impervious surfaces. Additionally, the site is a known contaminated site with soil and groundwater contamination that exceed NJDEP standards. Due to the conditions described above, no groundwater recharge is proposed as part of the stormwater management facilities on site. 5.2 Soil Erosion and Sediment Control The Soil Erosion and Sediment Control plans and details are included within the Site Plan documents prepared by Bohler and must be followed throughout construction. Silt fences, stabilized construction entrances, temporary stockpile and inlet filters are proposed during construction. This report and the Site Plan documents prepared by Bohler are being submitted to the Hudson Essex Passaic Soil Conservation District for approval. 5.3 Low-Impact Development and Non-Structural Stormwater Management Facilities In accordance with the NJDEP regulations (NJAC 7:8-2.4) and the latest New Jersey Stormwater Best Management Practices Manual, several non-structural stormwater management strategies have been incorporated into the design of the site and are listed below: ▪ Stormwater Management Report for Proposed Retail Store▪ 7 ▪ December 2025 ▪

1. Protect areas that provide water quality benefits or areas particularly susceptible to erosion and sediment loss. The footprint of the improvements has been minimized to the previously improved and/or disturbed areas. The majority of the existing wooded areas remain undisturbed. Stormwater runoff will be discharged in a similar manner of existing conditions. Riparian zone and wetland disturbance has been minimized to continue providing water quality benefits. 2. Minimize impervious surfaces and break up or disconnect the flow of runoff over impervious surfaces. The overall impervious coverage is reduced by 0.07 AC. As part of the proposed site design, the minimum allowable parking and drive aisle sizes, in accordance with local ordinances, are used in lieu of larger stalls and aisles to reduce the amount of impervious surface in the post-development condition. Additionally, Pervious pavement is proposed in a portion of the parking lot. 3. Maximize the protection of natural drainage features and vegetation. The footprint of the improvements has been minimized to the previously developed area. All of the existing wooded areas remain undisturbed. Stormwater runoff will be discharged in a similar manner of existing conditions. Riparian zone and wetland disturbance has been minimized to continue providing water quality benefits. Soil erosion measures are proposed to be utilized during construction to protect the adjoining riparian zones, wetlands, tributary corridors, and undisturbed vegetation. 4. Minimize the decrease in the "time of concentration" from pre-construction to postconstruction. Pervious pavement has been included within the project’s stormwater design to achieve maximized times of concentration. Unretained stormwater runoff from the remaining portion of the site will flow over the parking lot to the Rahway River as it does in existing conditions. The portions of the site where mill and overlay is proposed has been designed to match existing grade as closely as possible to avoid changing the existing flow paths and times of concentration. 5. Minimize soil compaction. The project is located in Planning Area 1 (PA-1) therefore soil compaction is not required. 6. Provide low-maintenance landscaping that encourages retention and planting of native vegetation and minimizes the use of lawns, fertilizers, and pesticides. A comprehensive

ction is not required. 6. Provide low-maintenance landscaping that encourages retention and planting of native vegetation and minimizes the use of lawns, fertilizers, and pesticides. A comprehensive landscape plan has been incorporated into the design of the proposed improvements which includes low maintenance landscaping. The use of lawn areas has been minimized where applicable and fertilizers and pesticides are to be used sparingly. Native plants, including ground cover, shrubs and trees, are proposed. The native plantings will also require little or no irrigation once they are established. 7. Provide other source controls to prevent or minimize the use or exposure of pollutants from development sites in order to prevent or minimize the release of those pollutants into stormwater runoff. These source controls include, but are not limited to: ▪ Stormwater Management Report for Proposed Retail Store▪ 8 ▪ December 2025 ▪

i. Development design features that help to prevent accumulation and discharge of trash and debris in drainage systems. Proposed stormwater inlets have been specified with “eco” type curb pieces indicating the text “Dump No Waste, Drains to Waterways” and trash racks are specified for installation at the outlet control structure. In addition, a “Stormwater Management Facilities Operation & Maintenance Manual” has been prepared for use by contractors and the owners that specify that street sweeping must occur on a bi-monthly schedule. Dumpster areas are proposed throughout the site at key points. A dumpster area exists plan northeast which is to remain, and an additional 10’ X 10’ dumpster is proposed along the easterly side of the building for the proposed retail use. ii. Development design features that help to prevent and/or contain spills or other harmful accumulations of pollutants at industrial or commercial developments. Spills and accumulation of pollutants are not anticipated due to the type of use proposed. However, proposed stormwater management facilities intercept stormwater from the impervious surfaces and the proposed roadways, which will provide a collection point for vehicular pollutants. The proposed pervious pavement will improve water quality from vehicular surfaces by 80%. iii. When establishing vegetation after land disturbance, applying fertilizer in accordance with the requirements established under the Soil Erosion and Sediment Control Act, N.J.S.A. 4:24-39 et seq., and implementing rules. The soil erosion and sediment control plans address the requirement for establishing vegetation. Preventative source controls include the use of “eco” inlet curb pieces, storm drain inlets, and trash racks on outlet control structures. Pollution prevention techniques such as water quality treatment through infiltration and minimized clearing have been implemented in the design. The soil erosion and sediment control plan addresses re-stabilizing vegetation and implementing soil erosion and sediment control protection measures. Prevention and maintenance are also addressed in the Stormwater Operations and Maintenance Manual prepared for the project. Conclusions As demonstrated in the above sections, the stormwater management plan for the proposed development meets the current NJDEP Stormwater Management Regulations and Standards for Soil Erosion

Conclusions As demonstrated in the above sections, the stormwater management plan for the proposed development meets the current NJDEP Stormwater Management Regulations and Standards for Soil Erosion and Sediment Control in New Jersey and West Orange Township Stormwater Ordinance, and addresses the requirements for stormwater quantity reductions, water quality, groundwater recharge, and soil erosion and sediment control. As a result of the design calculations contained herein, Bohler anticipates that the stormwater design will not have a negative impact to surrounding areas. G:\2023\NJA230139.00\Admin\Reports\Stormwater\Rev. 0a\Abbreviated Stormwater Mgmt Report Template.docx ▪ Stormwater Management Report for Proposed Retail Store▪ 9 ▪ December 2025 ▪

A. PRE- vs. POST-DEVELOPMENT HYDROGRAPHS Current Adjusted Precipitation Depths ♦ ♦ ♦ ♦ ♦ McCuen-Spiess Sheet Flow Length Calculations 2-Year Storm Event 10-Year Storm Event 100-Year Storm Event Pre- vs. Post Comparison

McCuen-Spiess Calcs Max Sheet Flow Length (L) Slope (S) Manning's Roughness (N) Grass (5%) Pavement (4%) 149.07 0.05 0.15 1818.18 0.04 0.011