2022 08 Drainage Report

Vil. RUNOFF RATES The following is a comparison of the existing and proposed conditions runoff rates: Existing and Proposed Conditions Peak Runoff Rates Results Si otal NIAC 7:8 EXISTING Bate ALLOWABLE | PROPOSED RUNOFF RATE REQUIRED RUNOFF BUNGEE REDUCTION RATE RATE 2 Year 2.33 cfs 50% LIT cfs 1.17 cfs 10 Year 5.58 cfs 25% 4.19 cfs 2.49 cfs 25 Year 8.06 of Meet or reduce 8.06 cfs 3.46 cfs existing 100 Year 12.84 cfs 20% 10.27 cfs 7.51 cfs VOI. WATER QUALITY As per NJAC 7:8-5.5 for Stormwater Runoff Quality Standards, stormwater runoff quality standards are applicable when a major development results in an increase of one-quarter acre or more of regulated motor vehicle surface. The subject development results in an increase of only approximately 0.14 acres of vehicular traveled surface and is therefore not subject to stormwater quality requirements. However, nonetheless each of the four (4) proposed small-scale bioretention basins with underdrains does infiltrate the full water quality storm through the bioretention media soil bed to achieve a TSS removal rate of 80% and would satisfy the water quality requirements aspect of NJAC 7:8 if it were required. IX. GROUNDWATER RECHARGE As pteviously noted, on-site review of the tract was initially performed by Dynamic Engineering Consultants, PC to verify existing site conditions and land cover characteristics. Furthermore, Dynamic Earth, LLC performed test pits within the site to establish the seasonal high-water table and soil permeability rates. Due to the shallow water table depth and low permeability rates observed, as per Chapter 12 of the New Jersey Best Practices Manual, the soil shall be considered a D rated soil due to the characteristics observed via soils testing. Therefore, as per NJAC 7:8-5.4 Groundwater Recharge Standards, groundwater recharge requirements are not applicable to the proposed development. SHI Builders August 2022 DEC# 4266-99-001 -6-