12 2026 02 12 Crestmont CC Stormwater Management Report

• Minimum distance between basin bottom and seasonal high groundwater/bedrock: 1 foot • Maximum water quality design storm event water depth: 12 inches • Maximum design storm drain time: 72 hours Table 13 – Small-Scale Bioretention Basin Design Summary Contributory Groundwater WQDS Water Bottom of Highest BMP Drainage Test Pits2 or Mottling Depth (FT) BMP EL.3 Bedrock EL.4 Area1 (AC) EL. SSBB-1 1.41 0.52 TP-1, TP-2 530.50 529.05 534.006 TP-3, TP-4, TP- SSBB-2 1.91 0.39 533.50 N/E 540.57 11, TP-12 Notes: 1. Contributory drainage area is the inflow drainage area to a BMP that excludes the area of the BMP itself in the case of a surface BMP. 2. Refer to the drainage plans, drawing CG103 & CG104, for BMP locations. Refer to Appendix F for supporting geotechnical investigation information including test pit logs. 3. The bottom of BMP elevation is the bottom of the underdrain gravel layer for an under-drained bioretention basin. 4. If groundwater and soil mottling were not encountered, the limiting design feature is bedrock. In this case, rock will be excavated to be a minimum of one foot below the bottom BMP elevation. 5. Within SSBB-1, the following test pits were performed and indicated the following elevations of groundwater or mottling: TP-1 did not encounter groundwater, and TP-2 encountered groundwater at el. 529.0. 6. Within SSBB-1, the following test pits were performed and indicated the following elevations of bedrock: TP-1 encountered bedrock at el. 524.0, and TP-2 encountered bedrock at el. 528.0. 7. Within SSBB-2, the following test

erformed and indicated the following elevations of bedrock: TP-1 encountered bedrock at el. 524.0, and TP-2 encountered bedrock at el. 528.0. 7. Within SSBB-2, the following test pits were performed and indicated the following elevations of bedrock: TP-3 encountered bedrock at el. 534.0, TP-4 encountered bedrock at el. 533.0, TP-11 encountered bedrock at el. 536.0, and TP-12 encountered bedrock at el. 540.5. A porous asphalt pavement system is proposed to meet the stormwater quantity requirements. The underlying stone storage bed has been sized in order to attenuate the 2-, 10-, and 100-year design storm events. The following parameters must be met as part of the system design as per Chapter 9.6 of the New Jersey BMP Manual; all design criteria has been met – refer to calculations in the appendices of this report as well as the design drawings: • Maximum area of additional inflow: 3 times the porous pavement area • Minimum distance between basin bottom and seasonal high groundwater/bedrock (under-drained systems): 1 foot • Maximum design storm drain time: 72 hours 14