PB 22 10 Altera 769 LLC Filed Application with Exhibits Final Site Plan Phase 2

proposed aboveground stormwater management basin. Stormwater runoff is then detained and released at a controlled rate to the existing stormwater management structure (POI-2). A time of concentration of 13.3 minutes has been calculated and utilized for this drainage area. DA-3: This area consists of the remainder of the subject site which includes the existing office building, remaining parking areas and open space (lawn) areas. Stormwater runoff generated by this area sheet flows overland in a southerly direction where it is collected by a series of existing inlets. Ultimately, stormwater runoff is conveyed to the existing stormwater conveyance system within Northfield Avenue (CR 508) (POI-3). A minimum time of concentration of six (6) minutes has been utilized for this drainage area. IV. DESIGN METHODOLOGY The intention of the design of the proposed stormwater management facilities is to provide measures as required to address applicable aspects of the Township of West Orange Land Use Ordinance, NJAC 7:8, and the New Jersey SESC standards. In order to prepare the stormwater management design for the subject project, an extensive initial investigation of the property and a topographic survey were performed. On-site review of the tract was performed by Dynamic Engineering Consultants, PC to verify existing site conditions and land cover characteristics. A Boundary, Location & Topographic Survey of the subject site was also prepared by Dynamic Survey, LLC, to depict the existing site conditions. The calculations were established through an examination of the existing site conditions, a review of the topographical survey, and establishing our drainage area maps. The plans were designed to ensure that runoff from the proposed development could be directed to the proposed stormwater management facilities, and designed to meet applicable stormwater quantity and quality requirements set forth by the Township of West Orange and NJAC 7:8. Based on our review of the existing site conditions, review of the survey, and establishment of the Drainage Area Maps for the existing and proposed site conditions, the calculations of this Report were established. A grading plan was also developed for the proposed site improvements with consideration to the existing drainage patterns. The plan was designed to ensure that runoff from the proposed development could

grading plan was also developed for the proposed site improvements with consideration to the existing drainage patterns. The plan was designed to ensure that runoff from the proposed development could be directed to the proposed stormwater management facilities and reduce peak flow rates when compared to existing conditions. The site has been evaluated using the TR-55 ‘Urban Hydrology for Small Watersheds’ standards. Stormwater runoff rates for the subject site were modeled using Hydrology Studio. The 2-, 10-, and 100-year design storms are based upon the New Jersey 24-Hour Rainfall Frequency Data for Essex County as published by the USDA NRCS utilizing a Type D rainfall distribution. Pervious and impervious areas were modeled separately as per the NJ Stormwater Management Best Practices (BMP) Manual. Altera 769, LLC 6 Revised August 2022 DECPC #2530-99-006