1240815StormWaterManagementReportrcd 3 12 2026

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 REVISED: December 02, 2025 REVISED: February 04, 2025 ______________________________________________________ MICHAEL LANZAFAMA, P.E. & P.L.S. NJ REG. # GB 30084

TABLE OF CONTENTS PROJECT LOCATION…………..…...…………….………………1 EXISTING CONDITION……………………………………….…....1 TOPOGRAPHY………...……………………………………………1 SOILS…………………………………………………………………1 IMPERVIOUS COVERAGE SUMMARY…………….……………1 STORMWATER MANAGEMENT…………………………………2 DISCHARGE SUMMARY………………………………….……....2

APPENDICES I SOILS….…………………………………………………………...3 II WATER QUALITY CALCULATIONS….……………………...10 III TIME OF CONCENTRATION CALCULATIONS…………….25 IV HYDROLOGIC ANALYSIS EXISTING AND PROPOSED…29 V DRAINAGE COLLECTION SYSTEM………………….……135 VI SCOUR HOLE CALCULATIONS…………………………....138 VII GROUNDWATER RECHARGE………………………….…..140 VIII MOUNDING CALCULATIONS……………………………....144 IX DRAINAGE AREA MAPS……………………….…………...147

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 EXISTING (LOT EXISTING (LOT 11) 12) PROPOSED BUILDING(S) 1685 1023 3426 DRIVEWAY(S) 5460 2102 6411 WALKS/STEPS 595 69 1265 PATIO/DECK 0 82 0 MISC. 12 0 93 TOTAL 7752 3276 11195 NET 167 COVERAGE

93 TOTAL 7752 3276 11195 NET 167 COVERAGE 1

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, 25-year, and 100-year storm events. For major developments, the reduction factors applied to the 2-, 10-, and 100-year storm events are 50%, 25%, and 20%, respectively. This project does qualify as a major development, and these reductions were applied to comply with the township’s requirements in addition to further enhancing 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 After Q Q Total Q Non Frequency Disturbed Reduction Reduction Disturb Allowable Proposed Q Q 2 - 2020 0.97 x 0.50 = 0.49 + 0.00 =

uction Reduction Disturb Allowable Proposed Q Q 2 - 2020 0.97 x 0.50 = 0.49 + 0.00 = 0.49 0.44 COMPLY 10 - 2020 1.63 x 0.25 = 1.22 + 0.00 = 1.22 0.79 COMPLY 25 - 2020 2.10 x 0.00 = 2.10 + 0.00 = 2.10 1.09 COMPLY 100 - 2020 2.96 x 0.20 = 2.37 + 0.00 = 2.37 1.80 COMPLY 2 - 2050 1.19 x 0.50 = 0.60 + 0.00 = 0.60 0.56 COMPLY 10 - 2050 1.98 x 0.25 = 1.49 + 0.00 = 1.49 1.00 COMPLY 25 - 2050 2.59 x 0.00 = 2.59 + 0.00 = 2.59 1.51 COMPLY 100 - 2050 3.81 x 0.20 = 3.05 + 0.00 = 3.05 2.35 COMPLY 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 enhance the existing downstream conveyance systems and meet the required Municipal standards. Calculations supporting these findings constitute the remainder of this report. 2

SOILS

Development Engineering, LLC 550 Colfax Road Wayne, NJ 07470 (973) 835-0340 Soil Percolation Report June 30, 2025 Isaac Lefkowitz 127 Mitchell LLC 516 Pleasant Valley Way West Orange, NJ RE: Percolation Test Seepage Pit/Drywell for Proposed Office Building 512 & 516 Pleasant Valley Way West Orange, NJ Percolation Rate by Soil Category Percolation speed or percolation rate, measured in inches per hour, depends greatly on the soil type as described below:  Sandy soils usually have very high percolation rates, measured in the range of 1 to 8 inches or more per hour. That means sandy soils dry out very quickly, heat up very quickly.  Silty soils, including loam, have moderate percolation speeds, ranging from 0.1 to 1 inch per hour.  Clay soils have notoriously slow percolation speeds of 0.1 inch or less per hour. These soils easily become waterlogged, and plant roots can suffocate as a result.  Any soil can vary significantly from the percolation rate averages. This variation can be due to factors that include soil compaction, organic matter content and/or soil temperature. Yet soil types are by far the single biggest determinant for percolation rates. Percolation Rate Field Measurement Estimating percolation speed is based on general knowledge of soil's type and/or through observation of how well it drains. Also, however, a simple percolation test can easily be done to determine a more precise percolation rate following the steps below to conduct the field tests: Field Tests 6

Development Engineering, LLC 550 Colfax Road Wayne, NJ 07470 (973) 835-0340 The field test was performed Monday about 10:30 AM June 13, 2025 within the proposed area of the seepage pit, shown on the proposed Drainage Plan of the Site Plan, in accordance to the following steps: Step 1: Test Hole Excavated one hole in the proposed drywell area (desired soil percolation rate testing area). The hole measured about 4 feet wide by 7 feet long and about 10 feet deep. Since the proposed seepage pit area is about 8 feet x 10 feet wide, only one hole was dug in the center of the proposed seepage pit area. A soil sample was also collected from the bottom of the pit for libratory analysis. Step 2: Soil Saturation Attempted to completely fill the test hole with water, and waited several hours for the water to fill the hole so it subsequently drains into the soil but the water was draining very rapidly. Step 3: Refill Test Hole Ensured the water had drained completely, and refilled the hole with water up to within 10" inches of its bottom. Step 4: Measure Initial Water Level Laid a wood board across the top of the test hole as the measuring baseline. Then, inserted a tape measure to the test hole bottom and measured the distance from the measuring baseline (2x10 board) to the water level. Step 5: Measure Final Water Level Change Returned to the test hole, inserted a tape measure to the test hole's bottom, and after 7.5 minutes measured the new distance from the board to the water level. Step 6: Repeat Measurements Measured the distance between the water level and the board every 7.5 minutes three additional times. After taking four measurements, determined how much the water level had dropped between each measurement. The amount of change per hour is the soil's percolation rate. For the proposed seepage pit area, the water level dropped at the rate of more than 5.8 inches per hour. The water table was not encountered during the test hole excavation about 10.0 feet below the grade. 2 7