2022 08 Drainage Report

VI. STORMWATER MANAGEMENT SYSTEM DESIGN & GREEN INFRASTRUCTURE COMPLIANCE As detailed above, in order to meet the stormwater runoff quantity requirements for the proposed development, the stormwater management system design includes four (4) proposed aboveground small-scale bioretention basins with underdrains. The proposed development is not subject to quality or groundwater recharge requirements — More information will be detailed in the following sections of this report. The stormwater management design utilizes four (4) small scale bioretention systems with underdrains. The systems will accept runoff via overland flow. The collected stormwater runoff will infiltrate through the planted vegetation in the soil bed to the underdrain and be released at a controlled rate through outlet control structures in order to satisfy the runoff peak rate reductions (quantity requirement). Although quality requirements are not required, the basins will also provide 80% TSS removal. The stormwater runoff from yard areas and impervious surfaces will be conveyed to the basins via overland flow and discharged at a controlled rate using outlet control structures. In accordance with the New Jersey Stormwater Best Management Practices Manual, the following design considerations have been satisfied: * Bottom of gravel layer must be a minimum of one (1) foot above Seasonal High-Water Table + System must fully drain volume within 72 hours * Bottom of system must be as level as possible * Construction of system must be done to avoid compaction of sub-grade soils + Minimum design permeability rate of 0.5 Inches/hour + — System must be designed to safely convey overflow volume + System may not be used where there is risk of basement flooding, etc. Green Infrastructure Design Standards Compliance — Small Scale Bioretention Basins BMP Criteria Requirement Basin A Basin B Basin C Basin D lear 2.5 Ac 0.669Ac | 0.831Ac | 0.821Ac } 0.422 Ac Drainage Area [1] Max. Drain Time 72 Hrs 25.95 Hrs | 26.30Hrs | 25.90Hrs | 25.50 Hrs Min. Subsoil Design : 7 . . , P ability Rate 0.5 in/hr 0.5 in/hr 0.5 in/hr 0.5 in/hr 0.5 in/hr Min. Separation between 1.0 FT with Additional | Additional | Additional | Additional SHWT & BMP Bottom ° F soils testing | soils testing | soils testing | soils testing underdrain Fi A : : A 7 . is required is required is required is required [1] Does not

al | Additional | Additional SHWT & BMP Bottom ° F soils testing | soils testing | soils testing | soils testing underdrain Fi A : : A 7 . is required is required is required is required [1] Does not include area of BMP SHI Builders August 2022 DEC# 4266-99-001 -5-