J_2024 05 09_West Orange Stormwater Management Plan

PSE&G Mav 17.2011 Page 6 The area of the test pits is a depressed area which appears to receive surface runoff from the higher areas of the site. At the test pits performed in the southwest portion of the site, a layer of topsoil on the order of ten to twelve inches in thickness was present typically underlain by sandy clay loam soils. In Test Pit 2, a layer of silty clay was observed at 11 to 13 feet followed by loamy sand/sandy loam. Groundwater seepage was observed in borings SBH-2, 4 and 5 at depths ranging from approximately 7 to 14 feet below grade at the completion of the drilling. Light seepage was observed in the test pits at depths of about 1 to 2.5 feet below grade with moderate to rapid seepage observed at depths of 11.5 and 13 feet. Soil mottling was observed in the test pits at depths on the order of one to one and one-half feet below grade. A subsurface profile depicting the generalized subsurface conditions is presented on Plate 9. Findings and Recommendations General: Based on the subsurface conditions encountered in the borings performed for this study, it is our opinion that the existing near surface fill where present is not suitable for direct support of new structures on spread foundations due to the unknown nature of the placement and compaction of the material. Further, the SPT blow counts indicate the fill to be loose in relative density to about eight feet in Boring SBH-5. Therefore, any existing fill extending below the foundations should be completely removed to the surface of the undisturbed natural soils and the foundations established directly on the natural soils, or the excavations could be backfilled to conventional foundation levels with clean crushed stone. The new structures could then be supported on conventional spread foundations that would derive their support from the undisturbed natural soil or crushed stone backfill and could be designed to impose maximum allowable net bearing pressures of up to 4,000 pounds per square foot.