J_2024 05 09_West Orange Stormwater Management Plan

August 8, 2022 File No. 26.0092704.00 PSE&G – West Orange, NJ Page 13 Proactive by Design Lateral Earth Pressures: If required, excavation support systems, below grade structures or site retaining walls should be designed to resist lateral earth pressures imposed by the adjacent soils, as well as surcharge loads due to adjacent equipment, traffic, floor slabs or foundation loads, etc. We estimate that the following soil parameters could be used to design these systems: Total Active Earth Unit Weight (pcf) Angle of Internal Friction (degrees) Cohesion (psf) Existing sandy and clayey fill materials 120 30 0 0.333 Clean ¾” crushed stone backfill 105 38 0 0.238 Natural silty and clayey sands or imported granular controlled compacted fill 125 34 0 Natural sandy silts and clays 120 26 2,000 Soil Type Pressure Coefficient (Ka) 0.282 0.390 We do not recommend that any silty or clayey soil be used as backfill adjacent to below-grade walls as they are relatively poorly draining and may impose higher lateral pressures. Excavated sands, silty sand or imported granular materials as previously specified would be better suited for this use. Stormwater Management Design: As part of our work, we were requested to perform three test pits and permeability tests. The logs of the test pits (TP-101 through TP-103) have been provided in USDA format for stormwater design purposes. In addition, single ring field infiltration tests were initiated at An Equal Opportunity Employer M/F/V/H