250701_42 ERW_Stormwater Report

Introduction This Stormwater Management Report for the proposed project has been prepared by Colliers Engineering & Design for The Waymaker, LLC. Colliers Engineering & Design performed a hydrological assessment for the property located at 42 Eagle Ridge Way, West Orange, New Jersey, also defined as Block 106, Lot 24.01. The site is currently ±3.09-acres in size and was previously occupied by a single-family home and associated driveways and site improvements. The house was recently demolished and the property was cleared, and is currently occupied by stockpiles of gravel and other materials. The proposed development consists of the construction of a single-family home and a barn and indoor arena for the keeping of horses. There will also be an outdoor arena, grass paddocks, and associated driveways and pathways. The proposed development results in a total disturbance of approximately 3.13 acres and a total impervious area of approximately 0.40 acres (0.19-acre increase) within the proposed development area. Purpose This report assesses the hydrologic aspects, and the stormwater drainage conditions as a result of the proposed construction, including the house, barn, arenas, paddocks, landscaping areas, stormwater management facilities, associated utilities, and related site improvements. The focus of the study is the identification of the existing drainage characteristics prior to the demolition of the house in comparison to post-development conditions. Calculations documenting the design of the stormwater management system are illustrated on the Site Plan drawing documents, prepared by Colliers Engineering & Design. Method Generally, stormwater runoff from the site flows overland from west to east and discharges to an existing drainage channel located at the northeastern corner of the site (Design Point 1). The remainder of the site drains overland to the south (Design Point 2). The area, curve number, and time of concentration for each existing watershed can be seen on the Existing Drainage Area Map included in the appendix. For the purposes of this analysis the existing conditions include the previously demolished house and site improvements. Under proposed conditions, the site will generally mimic the existing drainage pattern; however, the majority of the proposed development will be captured and routed through a subsurface infiltration basin to

oposed conditions, the site will generally mimic the existing drainage pattern; however, the majority of the proposed development will be captured and routed through a subsurface infiltration basin to attenuate peak flows. New inlets and pipes will be installed to convey the stormwater runoff from certain areas to the infiltration basins. Tributary areas to the infiltration basin are outlined on the Proposed Drainage Area Map and include the house, barn, arenas, and the majority of the proposed pathways and paddocks. The area, curve number, and time of concentration for each proposed watershed can be found on the Proposed Drainage Area Map and HydroCAD output included in the appendix. Stormwater Management Report | October 18, 2024 – Revised July 1, 2025 Page 2