6624 BROADWAY 2018-01-02 MF Import

and cut slopes may have to be adjusted in the field. In addition, WISHA/OSHA regulations should be followed at all times. If surface water or ground water seepage is encountered in temporary excavations, temporary excavation slope angles will need to be flatter than the maximum values estimated above. Permanent slopes composed of new structural fill should be made at inclinations no steeper than 2H:IV. The on -site soils contain a high percentage of fine-grained material that makes them moisture - sensitive and subject to disturbance when wet. The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs, the softened soils should be removed and the area brought to grade with structural fill. Existing Fill Once demolition and site preparation procedures have been completed, existing fill should br, addressed. Ideally, it will be possible to lay the site out in such a way that new buildings will not be underlain by existing fill. In areas of existing fill where paving is planned, we recommend that the upper 2 feet of existing fill be excavated to expose underlying materials. The underlying materials should be compacted to 95 percent of the modified Proctor maximum dry density and proof -rolled with a loaded dump truck or other suitable eq,lipment under the observation of Associated Earth Sciences, Inc. (AESI). Any soft or yielding areas may require further removal or other measures to provide a more stable surface for fill placement. Structural fill should then be placed to reach desired subgrade elevation for paving. If existing fill is encountered in areas where new buildings are planned, we recommend that the existing fill be completely removed to expose underlying native sediments and replaced with compacted structural fill. As an alternative to removal and replacement of existing fill below building areas, it would be possible to use a system of rock trenches for foundation support. Even if rock trenches are used, we recommend that any fill materials that are placed within the footprint of new buildings be placed as Structural Fill, as recommended in this report. If buildings will be constructed above existing fill and supported on rock trenches, areas of slab -on -grade floor could be supported by limited removal and replacement of the existing fill as described above for areas that will support paving. Limited removal and replacement of the existing fill below floor slabs is intended to be a cost effective approach to limiting the potential for future settlement of the floor; however, it should be noted that some risk of future settlement cannot be ruled out if this alternative is selected. If some small risk of future settlement of slab -on -grade floors is not acceptable, then the existing fill should be removed from below planned slab -on -grade floors and replaced with structural fill. We observed existing fill in one of the explorations, HA -I. The existing fill at that location contained organic debris and asphalt rubble. Such materials are not suitable for reuse in structural fill applications. If existing fill needs to be removed, we should be allowed to 4