J_2024 05 09_West Orange Stormwater Management Plan

PSE&G Mav 17.2011 Eagel Site Preparation and Earthwork: Site preparation activities within the area of the improvements should include the excavation of the existing fill materials to the surface of the natural soils. The fill materials observed in our recent explorations typically extended to depths of approximately two and one half feet in SBH-1 and 2 to nine feet below the surface in SBH-5. As such, it is likely that the fill would extend to below conventional foundation levels in some portions of the site and would have to be removed. However, variations in the depth to the bottom of the fill soils should be anticipated between the exploration locations. After removal of any existing fill below the new foundations, crushed stone backfill could be installed to reach the design bottom of footing levels. If crushed stone backfill is used, the excavation should be widened on all sides one foot laterally for each two foot depth of overexcavation. A graphic representation of the overexcavation limits is presented on the Suggested Foundation Overexcavation Detail shown on Plate 10. Groundwater was encountered in the borings at depths ranging from approximately 7 to 14 feet below grade at the time of our study. However, perched seepage was observed as shallow as one foot in the test pits and could also be present trapped within the fill or at the interface of the fill and natural soils. As such temporary control of seepage and surface runoff will likely be required during construction. It is anticipated that seepage could be controlled by pumping from a series of sumps. If deeper excavations extend below the observed groundwater levels, more formal dewatering methods could be necessary such as wellpoints or temporary wells. It should be the contractor’s responsibility to provide whatever labor and equipment is necessary to control seepage. If seepage is not properly controlled, the natural subgrade soils will likely become softened and disturbed, and additional overexcavation could be required. We also recommend that the site be graded during construction to prevent surface water from entering the site excavations.