6624 BROADWAY 2018-01-02 MF Import

observe the underlying surface, and to evaluate the removed material to determine if it is suitable for reuse. Structural Fill ' Structural fill will be necessary to establish desired grades. All references to structural fill in this letter -report refer to subgrade preparation, fill type, placement, and compaction of I materials as discussed in this section. If a percentage of compaction is specified under another section of this letter -report, the value given in that section should be used. It should be noted that the site contains a significant amount of loose, existing fill. Loose, existing fill has the potential to settle under the weight of new structural fill, structural loads, or other loads. The grading plan had not been iCrmulated at the time this letter -report was written. We recommend that we be allowed to review grading plans and utility plans when they are developed so that we can identify any areas with potential settlement concerns, and offer mitigation recommendations. Pill placement above existing slopes is not expected for this project. We should be allowed to review any fill planned over a slope before it is placed. After stripping, planned excavation, and any required overexcavation have been performed to the satisfaction of the geotechnical engineer, the upper 12 inches of exposed ground should be rccompacted to 90 percent of the modified Proctor maximum density using American Society for Testing and Materials (ASTM):D 1557 as the standard. If the subgrade contains too much moisture, adequate recompaction may be difficult or impossible to obtain and should probably not be attempted. In lieu of recompaction, the area to receive fill should be blanketed with washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the exposed ground remains soft and further overexcavation is impractical, placement of an engineering stabilization fabric may be necessary to prevent contamination of the free -draining layer by silt migration from below. After recompaction of the exposed ground is tested and approved, or a free -draining rock course is laid, structural fill may be placed to establish desired grades. Structural fill is defined as non -organic soil, acceptable to the geotechnical engineer, placed in maximum 8-inch loose lifts with each lift being compacted to 95 percent of the modified Proctor maximum density using ASTM:D 1557 as the standard. The top of the compacted fill should extend horizontally outward a minimum distance of 3 feet beyond the locations of the perimeter footings before sloping down at an angle no steeper than 2H:1V. The contractor should note that any proposed fill soils must be evaluated by AESI prior to their use in fills. This would require that we have a sample of the material 72 hours in advance to perform a Proctor test and determine its field compaction standard. Soils in which the amount of line -grained material (smaller than No. 200 sieve) is greater than approximately 5 percent (rneasmed on the minus No. 4 sieve size) should be considered moisture -sensitive. Use of 5