CME Associates Review 2

Ne ASSOCIATES Chairman and Members of the West Orange Township Planning Board duly 29, 2024 Re: West Essex Highlands, LLC (PB 24-01) Our File No. VWRP0179.01 Preliminary & Final Site Plan - Review #2 Page 12 45. The basin #10 section on Sheet SP-26 indicates that the replacement soil will have a 46. 47. 48. 49. 50. 51. 52. 53. 55. 56. permeability rate of 8 inches per hour, however, the hydrograph routings utilize an exfiltration rate of 10 inches per hour. This discrepancy must be resolved. Verify the size of pipes exiting outlet structure #10. Sheet SP-23 and the detail on Sheet SP-26 shall be revised accordingly. Per Chapter 9.8 of the NJ BMP Manual, a minimum of 2.0 ft of separation is required between the lowest elevation of the sand layer and the seasonal high-water table. While the sand layer thickness is not provided on the basin #10 section on Sheet SP-26, the minimum 6” sand layer would put the bottom of the sand layer at elevation 575.5, which is less than 2 feet from the seasonal high-water table. Design modifications appear to be required. Verify drainage areas ‘Basin 11 — Imp’ and ‘Basin 11 — Perv’ as same is inconsistent with the Post-Development Drainage Area Map. Verify the sizes of pipes connecting to outlet structure #11 and they are inconsistent between the plans and details. Sheet SP-24 and the details on sheet SP-26 must be revised accordingly. Sheet SP-24 must be revised to indicate the size and elevation of the orifice and or weir associated with outlet structure #11. The hydrograph routings for porous pavement system #11 utilize an exfiltration rate of 10 inches per hour. The Stormwater Management Report indicates that a design permeability rate of 4 inches per hour is utilized and the porous pavement #11 section detail indicates the soil replacement permeability will be 20 inches per hour. This discrepancy must be resolved. Verify the water surface elevations within the hydrograph routings and on the small-scale subsurface infiltration basin #12 detail on sheet SP-26 as they are inconsistent. Revise as necessary. Verify the invert elevations of the subsurface infiltration basin #12 as they are inconsistent between the plan and details. Sheet SP-24 and Sheet SP-26 shall be revised accordingly. . In accordance with Chapter 13 of the BMP Manual, calculations must be submitted supporting the duration of the

tween the plan and details. Sheet SP-24 and Sheet SP-26 shall be revised accordingly. . In accordance with Chapter 13 of the BMP Manual, calculations must be submitted supporting the duration of the infiltration period (‘t’ within the groundwater mounding calculations). The groundwater mounding calculations must be revised to correct the Kh values within each spreadsheet. Kh must be equal to the recharge rate for projects located outside of the coastal plain. The recharge rate within groundwater mounding calculations for small scale infiltration basin #2 must be verified. The hydrograph routings utilize an exfiltration rate of 10 inches :\West Orange\Planning Board\VWRPO179.01 - West Essex Highlands, Inc\Review #2 07-29-24.docx