12 2026 02 12 Crestmont CC Stormwater Management Report

Table 8 – POA-1 Allowable Peak Discharges (Future) Design Storm Existing Peak Allowable Peak Event Discharge (CFS) Discharge (CFS) 2-Year 16.83 15.52 10-Year 29.21 27.85 100-Year 58.39 56.05 Note: Total Allowable Peak Discharges are calculated by hydraulically adding runoff hydrographs and may not reflect the direct addition of peak discharge rates. Refer to the hydrograph report calculations in Appendix A. • Point of Analysis 2 (POA-2): The proposed redevelopment within this watershed results in peak runoff rates increasing in the proposed condition, and quantity control BMPs are required to be implemented. Therefore, it shall be demonstrated in accordance with N.J.A.C. 7:8-5.6.(b).3 that the post-construction peak runoff rates for both the current and future 2-, 10-, and 100-year design storm events are 50, 75, and 80%, respectively, of the pre-construction runoff rates for the disturbed portions of the overall watershed. Table 9 – POA-2 Allowable Peak Discharges (Current) Design Storm Existing Peak Allowable Peak Event Discharge (CFS) Discharge (CFS) 2-Year 9.63 7.23 10-Year 17.05 14.95 100-Year 32.74 29.56 Note: Total Allowable Peak Discharges are calculated by hydraulically adding runoff hydrographs and may not reflect the direct addition of peak discharge rates. Refer to the hydrograph report calculations in Appendix A. Table 10 – POA-2 Allowable Peak Discharges (Future) Design Storm Existing Peak Allowable Peak Event Discharge (CFS) Discharge (CFS) 2-Year 11.97 9.00 10-Year 21.02 18.44

Discharge (CFS) 2-Year 11.97 9.00 10-Year 21.02 18.44 100-Year 42.47 38.36 Note: Total Allowable Peak Discharges are calculated by hydraulically adding runoff hydrographs and may not reflect the direct addition of peak discharge rates. Refer to the hydrograph report calculations in Appendix A. 10

3.1.6 Proposed Watersheds The proposed watersheds are depicted on Figure 5 – Proposed Watershed Map. Watershed PR-1A-DISTURBED is approximately 0.65± acres and consists of proposed parking and pervious landscape areas. Stormwater runoff is conveyed via overland flow and the proposed conveyance network to Small-Scale Bioretention Basin 1 (SSBB-1). From this point, runoff is conveyed via a proposed conveyance network and the existing conveyance network within Laurel Ave and Eagle Rock Ave to POA-1. Watershed PR-1A-UNDISTURBED is approximately 0.91± acres and consists predominately of existing parking areas, rooftop, and pervious wooded and grass areas. Stormwater runoff is conveyed via overland flow and the proposed conveyance network to Small-Scale Bioretention Basin 1 (SSBB-1). From this point, runoff is conveyed via a proposed conveyance network and the existing conveyance network within Laurel Ave and Eagle Rock Ave to POA-1. Watershed PR-1B-DISTURBED is approximately 0.35± acres and consists predominately of pervious landscape areas. Stormwater runoff is conveyed via overland flow to the proposed Swale 1. The watershed is then conveyed via a proposed conveyance network and the existing conveyance network within Eagle Rock Ave to POA-1. Watershed PR-1B-UNDISTURBED is approximately 2.09± acres and consists predominately of existing parking areas and pervious wooded and grass areas. Stormwater runoff is conveyed via overland flow to the proposed Swale 1. The watershed is then conveyed via a proposed conveyance network and the existing conveyance network within Eagle Rock Ave to POA-1. Watershed PR-1C-DISTURBED is approximately 0.42± acres and consists predominately of pervious landscape areas and portions of Eagle Rock Avenue. Stormwater runoff is conveyed via overland flow to the conveyance network in Laurel Ave and Eagle Rock Ave. From this point, water is conveyed to the existing manhole POA-1. Watershed PR-1C-UNDISTURBED is approximately 1.85± acres and consists of portions of Laurel Ave, Eagle Rock Ave, the existing driveway, parking areas, and pervious wooded and grass areas. Stormwater runoff is conveyed via overland flow to the conveyance network in Laurel Ave and Eagle Rock Ave. From this point, water is conveyed to the existing manhole POA-1. Watershed PR-2A-DISTURBED is approximately 1.22± acres and consists of portions of the proposed

ork in Laurel Ave and Eagle Rock Ave. From this point, water is conveyed to the existing manhole POA-1. Watershed PR-2A-DISTURBED is approximately 1.22± acres and consists of portions of the proposed driveway, parking areas, and pervious landscape areas. Stormwater runoff is conveyed via overland flow and the proposed conveyance network to Small-Scale Bioretention Basin 2 (SSBB-2). From this point, runoff is conveyed via a proposed conveyance network and the 11

existing conveyance network within Eagle Rock Ave to POA-2. Watershed PR-2A-UNDISTURBED is approximately 1.04± acres and consists predominately of existing parking areas and pervious wooded and grass areas. Stormwater runoff is conveyed via overland flow and the proposed conveyance network to Small-Scale Bioretention Basin 2 (SSBB- 2). From this point, runoff is conveyed via a proposed conveyance network and the existing conveyance network within Eagle Rock Ave to POA-2. Watershed PR-2B-DISTURBED is approximately 0.40± acres and consists predominately of proposed parking and pervious landscape areas. Stormwater runoff is conveyed via overland flow to Porous Asphalt Pavement System 1 (PAPS-1). From this point, the watershed is conveyed via a proposed conveyance network and the existing conveyance network within Eagle Rock Ave to POA-2. Watershed PR-2B-UNDISTURBED is approximately 0.04± acres and consists of existing parking areas and pervious landscape areas. Stormwater runoff is conveyed via overland flow to Porous Asphalt Pavement System 1 (PAPS-1). From this point, the watershed is conveyed via a proposed conveyance network and the existing conveyance network within Eagle Rock Ave to POA-2. Watershed PR-2C-DISTURBED is approximately 0.87± acres and consists of portions of the proposed driveway, Eagle Rock Avenue, sidewalk, and pervious landscape areas. Stormwater runoff is conveyed via overland flow to the proposed onsite conveyance network and conveyance network within Eagle Rock Ave. From this point, the watershed is conveyed to the existing catch basin in Eagle Rock Ave, POA-2. Watershed PR-2C-UNDISTURBED is approximately 2.01± acres and consists of portions of existing parking areas, Eagle Rock Avenue, rooftop, and pervious wooded and grass areas. Stormwater runoff is conveyed via overland flow to the proposed onsite conveyance network and the conveyance network within Eagle Rock Ave, where it is then conveyed to POA-2. Refer to Appendix B for weighted curve number (CN) calculation worksheets and supporting hydrologic calculations for the determination of peak runoff rates. 3.1.7 Proposed Detention Routing Two (2) small-scale bioretention basins and one (1) porous asphalt pavement system are proposed in order to meet the stormwater quantity control requirements. According to N.J.A.C. 7:8-5.2.(f), small-scale bioretention basins and porous

ins and one (1) porous asphalt pavement system are proposed in order to meet the stormwater quantity control requirements. According to N.J.A.C. 7:8-5.2.(f), small-scale bioretention basins and porous asphalt pavement systems qualify as green infrastructure BMP’s that may be utilized for stormwater quantity, stormwater runoff quality, and groundwater recharge requirements without a waiver or variance. 12

Routing calculations have been provided in order to demonstrate that the basins have adequate storage capacity to safely convey storm events up to the 100-year design storm for both the current and future rainfall events; refer to Appendix C for supporting calculations. The total proposed peak discharge rates for the identified points of analysis can then be calculated by adding together the peak outflow from the proposed small-scale bioretention basins and porous asphalt pavement systems, along with the peak discharges from the undetained and undisturbed watersheds. Table 11 – Total Current Storm Event Proposed Peak Discharges (CFS) Point of 2-Year Storm 10-Year Storm 25-Year Storm 100-Year Storm Analysis POA-1 11.32 19.76 26.22 38.87 POA-2 5.67 10.31 15.04 23.96 Note: Total Proposed Peak Discharges are calculated by hydraulically adding runoff hydrographs and may not reflect the direct addition of peak discharge rates. Refer to hydrograph report calculations in Appendix B. Table 12 – Total Future Storm Event Proposed Peak Discharges (CFS) Point of 2-Year Storm 10-Year Storm 25-Year Storm 100-Year Storm Analysis POA-1 14.07 24.77 33.09 53.61 POA-2 7.27 14.02 20.85 31.63 Note: Total Proposed Peak Discharges are calculated by hydraulically adding runoff hydrographs and may not reflect the direct addition of peak discharge rates. Refer to hydrograph report calculations in Appendix B. 3.1.8 Quantity Control BMP Design Summary For small-scale under-drained bioretention basins, the following parameters must be met as part of the system design as per Chapter 9.7 of the New Jersey BMP Manual; all design criteria have been met – refer to calculations in the appendices of this report as well as the design drawings: • Maximum contributory drainage area: 2.5 acres 13

• 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

Table 14 – Porous Asphalt Pavement System Design Summary Ratio of Groundwater Bottom of Highest BMP Additional Test Pits2 or Mottling BMP EL.3 Bedrock EL.4 Inflow Area1 EL. PAPS-1 1.89 TP-9, TP-13, TP-14 553.00 548.05 557.256 Notes: 1. The ratio of additional inflow area is the contributing watershed area to a porous pavement system in relationship to the surface area of the porous pavement. 2. Refer to the drainage plans, drawings 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 stone storage layer for a porous asphalt pavement system. 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 PAPS-1, the following test pits were performed and indicated the following elevations of groundwater or mottling: TP-9 did not encounter groundwater, TP-14 did not encounter groundwater, and TP-13 encountered groundwater at el. 548.0. 6. Within PAPS-1, the following test pits were performed and indicated the following elevations of bedrock: TP-9 encountered bedrock at el. 545.0, TP-13 encountered bedrock at el. 542.5, and TP-14 encountered bedrock at el. 557.25. Refer to Figure 10 – Test Pit Location Plan, for a map showing the locations of the test pits with respect to the proposed BMP footprints. 3.1.9 Stormwater Quantity Summary A summary for each point of analysis, detailing the existing, allowable, and proposed peak discharge rates, is outlined in the table below. Table 15 – POA-1 Peak Discharge Summary – Current Storm Events POA-1 Design Storm