Stormwater Report

CASEY & KELLER, INC. LAND SURVEYORS + CIVIL ENGINEERS + PLANNERS N.J. STATE BOARD OF PROFESSIONAL ENGINEERS & LAND SURVEYORS CERTIFICATE OF AUTHORIZATION NO. 24GA27985400 258 MAIN STREET, MILLBURN, NEW JERSEY, 07041 VOICE: 973-379-3280 FAX: 973-379-7993 STORM WATER MANAGEMENT REPORT 512-516 PLEASANT VALLEY WAY TOWNSHIP OF WEST ORANGE ESSEX COUNTY, NJ Block 154.06, Lots 11 & 12 PROJECT # 1240815 DATE: August 11, 2025 Wadd ferme gun \MICHAEL LANZAFAMA, PLE. & P.L.S. NJ REGNY G) 4

STORM WATER MANAGEMENT REPORT SUMMARY PROJECT LOCATION The project is located at 512-516 Pleasant Valley Way in the Township of West Orange, Essex County, New Jersey. The site is located across the intersection with Greenwood Avenue and about 560 feet to the intersection with the southerly line of Eagle Rock Avenue. The property lies within the Office Building Zoning District. EXISTING CONDITIONS The site is currently occupied by two commercial buildings. One is a One-Story frame dwelling with parking in the rear and the second building a Two story masonry building. This building has also a parking lot on the rear of the property. The site area is 16,242 square feet in size or 0.373 acres. Its frontage on Pleasant Valley Way 124.99 feet, and it has a lot depth of 130.0 feet. It will be serviced with all basic utilities—water, gas, electric, sanitary sewer, and cable, which are provided from underground pipelines and conduits. The area around the site is developed with residential and commercial uses. The property is not impacted by flood plains, and freshwater wetlands have not been observed. TOPOGRAPHY The site slopes from north to south. The highest elevation is approximately 422.0 feet at the most northern corner of the property. The lowest elevation is at approximately 412.0 feet in the most southern corner of the property. SOILS The site contains two soil types. The Soil Survey of Essex County has identified the soils as Urban Land, Boonton, 0 to 8 percent slopes and Boonton - Urban Land, Boonton, 0 to 8 percent slopes. The Natural Resources Conservation Service has classified these soils as being in Hydrologic Soil Group “C’”. IMPERVIOUS COVERAGE SUMMARY IMPERVIOUS COVERAGE | EXISTING PROPOSED Buildings 2676 SF 3522 SF Drive & Parking 7679 SF | 2 6682 SF Patio OSF OSE Walk/step 794 SF | 1136 SF Total 11149 SF | Net Decrease 191 SF

STORMWATER MANAGEMENT As with any construction project, stormwater management is an important part of the overall development process. Modern practice is a combination of the site designer's knowledge and goals in conjunction with the rules and regulations of the local municipality and the New Jersey Department of Environmental Protection (see Hydrology section below). Part of stormwater management is to minimize the use of artificial structures; however, practical considerations of most development sites require a combination of non-structural and structural components. A substantial portion of the existing site contains buildings and bituminous pavement. The entire site drains to the south area where it runs thru a swale to the street on the rear and is collected by the storm system within Beasly Street. Stormwater hydrographs for both existing and proposed conditions for each drainage area, are included in this report. The Township of West Orange requires that stormwater analyses be performed for the 2-year, 10-year, and 100-year storm events, applying reduction factors of 50%, 25%, and 20%, respectively, for major developments. Although this project does not qualify as a major development, these reductions were voluntarily applied to further enhance site performance. The “Natural Resources Conservation Service Method,” as outlined in Technical Release 55 (TR-55), was utilized to size and route stormwater through the proposed drywell system. DISCHARGE SUMMARY The following table shows that the site would produce post-developed runoff rates and volumes that are lower than the site’s existing rates of runoff. The existing and proposed peak runoff rates (Q) from the site are summarized as follows: Site Discharge Summary Peak Detention Flow Subject to Q Q Total Q Frequency | Reduction | Reduction Existing Allowable Proposed Q Non Disturb 2- 2020 0.50 = 0.49 10 - 2020 0.25 = 1.22 100 - 2020 0.20 = 2.38 The Site Discharge table shows that the proposed project would result in post-developed runoff rates that are less than or equal to the site’s existing runoff rates. The hydrographs for the 2-year, 10-year and 100-year storms do not exceed at any time the pre-developed hydrographs for the same events as required per West Orange's ordinance. Based upon this analysis, it is our professional opinion that the proposed storm water management system would

e pre-developed hydrographs for the same events as required per West Orange's ordinance. Based upon this analysis, it is our professional opinion that the proposed storm water management system would enhance the existing downstream conveyance systems and meet the required Municipal standards. Calculations supporting these findings constitute the remainder of this report.

SOILS

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Hydrologic Soil Group—Essex County, New Jersey Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOL Percent of AO! Boonton - Urban land, C 0.3 86.4% Boonton substratum complex, 0 to & percent slopes Urban land, Boonton 4 13.6% substratum, 0 to 8 percent slopes Totals for Area of Interest 0.4 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas, Only the soils that in their natural condition are in group D are assigned to dual classes. 2 Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey 7/24/2025

HYDROLOGIC ANALYSIS EXISTING & PROPOSED

Exisiting Reach Parking Lot Pervious Pavers Proposed Sp [7] Bypass Proposed Pipes Routing Diagram for 1240815-pipes Prepared by Casey & Keller, Inc, Printed 8/25/2025 HydroCAD® 10.20-7a sin 03272 © 2025 HydroCAD Software Solutions LLC