2025 12 16_ZB 24 15_42 Eagle Ridge Way_Engineering Review 3

F:\2023\23-1345 West Orange 2024 Municipal Engineering Services\010 - ZB-24-15, Waystone Realty - 42 Eagle Ridge Way\Correspondence\Letters\2025-12-16_ZB-24-15_42 Eagle Ridge Way_Engineering Review 3.Docx 4 analysis for the “Current Rainfall” should also be provided to ensure reductions are met for these storms as well. 4.4. The approval by the West Orange Planning Board for the adjoining parcel at 40 Eagle Ridge Way included some drainage improvements on this parcel. These plans now reflect these improvements. 4.5. The Applicant’s engineer shall explain the reason for offsetting the proposed impervious area by the amount of impervious area and regulated motor vehicle surfaces that existed under the prior use. At the time of this application the remnants of the prior use were removed. The application form does not indicate any impervious areas on the parcel. Under recent guidance from the NJDEP for the review of stormwater designs, the “existing conditions” are the conditions that exist today. The Demolition Plan shows structures and driveway area that were previously removed. These pre-existing improvements must be excluded from the “existing conditions” as it relates to the impervious coverage on the parcel. 4.6. The Applicant’s engineer shall provide results of a geotechnical investigation to ensure the infiltration system meets the requirements of Chapter 12 of the NJ Stormwater Best Management Practices (BMP) Manual. Verification of the depth of bedrock and seasonal high- water table shall be submitted to the Municipal Engineer and confirmed prior to the issuance of a building permit. Test pits shall be made in accordance with NJDEP BMP manual and regulations for groundwater table location. Groundwater mounding calculations for the proposed infiltration basin should be provided in accordance with Chapter 13 of the NJDEP BMP. 4.7. The Times of Concentration were provided along with the method in which they were calculated. The proposed Time of Concentration calculations shall utilize the McCuen-Speiss limitation for determining the length of sheet flow. 4.8. The Applicant’s Engineer provided calculations on the Drywell overflow for both capacity and discharge velocity and offsite stability calculations as per NJ Soil Erosion and Sediment Control Standards. 4.9. Since pervious pavers are not part of the stormwater management system, the Engineer does not

ge velocity and offsite stability calculations as per NJ Soil Erosion and Sediment Control Standards. 4.9. Since pervious pavers are not part of the stormwater management system, the Engineer does not need to verify from their manufacturer that there is sufficient storage as specified. 4.10 The Engineer provided documentation from the manufacturer of the storage chambers that the storage volume per chamber is as specified. 4.11 Conveyance system calculations were submitted. However, the series of proposed inlets that collect runoff from the driveway and pathway areas and route directly into an underground basin require pretreatment in accordance with NJDEP Chapter 5. 5. Landscaping Plan 5.1 Matrix has no comment on the landscaping plan. 6. Soil Erosion & Sediment Control 6.1. The Applicant shall obtain a soil erosion and sediment control permit from the Hudson-Essex- Passaic Soil Conservation District. Matrix reserves the right to review the certification and approved plans from the district.