J_2024 05 09_West Orange Stormwater Management Plan

PSE&G Mav 17.2011 Paee 10 adequate bearing materials are present. All foundations should extend to a depth of at least three feet below the adjacent finished exterior grade to provide frost protection. Uplift loads may be resisted by the weight of the foundation, structure and soil within a prism defined by extending a line up and out from the edge of the foundation at an angle of 20 degrees from vertical. A total unit weight of 125 pounds per cubic foot could be assumed for the natural granular soils, excavated sandy fill, or imported granular fill as previously specified to be used as backfill, provided the materials are compacted to at least 95 percent of their ASTM D-1557 maximum dry density. Horizontal loads may be resisted by friction between the concrete and soil, and passive pressure. An ultimate coefficient of friction of 0.35 for sliding may be assumed between the foundation concrete and the silts and clays and the clayey sand soils. The coefficient of friction could be increased to 0.55 if crushed stone is provided below the foundations. Assuming the backfill is compacted as recommended, passive pressures may be calculated assuming a friction angle of 32 degrees (Kp = 3.25) and unit weight of 125 pounds per cubic foot. The designer should account for potential loss of support from freeze-thaw effects or future adjacent excavation if relying on passive pressures for shallow foundations. As such, we recommend that passive pressures be discounted for the upper two feet of soils due to potential disturbance. A subgrade modulus of 150 pounds per cubic inch would be appropriate for design of slabs supported by the natural clayey sand soils while a subgrade modulus of 200 pci could be used for imported granular soils as previously specified which are compacted to at least 95 percent of their ASTM D-1557 maximum dry density. Post-construction foundation settlements were estimated using the loads provided to us which are attached as Plate 11 and estimating a footing size based on the recommended bearing pressure of 4,000 pounds per square foot. As the site soils consist primarily of granular materials,