8615 7TH AVE SE Geotech Report 2018-01-02 MF Import

Subsurface Exploration, Geologic Hazard, and St. Mar), Magdalen Sport Court Preliminary Geotechnical Engineering Report Everett Washington Preliminnry Design Recommendations disturbance occurs, the softened soils should be removed and the area brought to grade with structural fill. 9.0 STRUCTURAL FI_LL Structural fill may be necessary to establish desired grades, particularly beneath slab areas. All references to structural fill in this report refer to subgrade preparation, fill type, placement, and compaction of materials as discussed in this section. If a percentage of compaction is specified under another section of this report, the value given in that section should be used. After stripping, planned excavation, and any required overexcavation have been performed to the satisfaction of the geotechnical engineer/engineering geologist, the upper 12 inches of exposed ground should be recompacted to a firm and unyielding condition. 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 subgr de. 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 attain 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 modified maximum dry den_•:ty, as determined by American Society for Testing and Materials (ASTM):D-1557. In the case of roadway and utility trench filling, the backfill should be placed and compacted in accordance with city or county codes and standards. The top of the compacted fill should extend horizontally outward a minimum distance of 3 feet beyond the locations of the perimeter footings or roadway edges before sloping down at a maximum angle of 2H:1V. The contractor should note that any proposed fill soils must be evaluated by Associated Earth Sciences, Inc. (AESI) prior to their use as structural fills. This would require that we have a sample of the material at least 72 hours in advance to perform a Proctor test and determine its field compaction standard. Soils in which the amount of fine-grained material (smaller than the No. 200 sieve) is greater than approximately 5 percent (measured on the minus No. 4 sieve size) should be considered moisture -sensitive. Use of moisture -sensitive soil in structural fills should be limited to favorable dry weather and dry subgrade conditions. The on -site soils contain substantial amounts of silt and fine sand and are considered moisture -sensitive when excavated and used as fill materials. We anticipate that all excavated site soils may require April24, 2006 IS.SOCI.4TED EARTH SCIENCES, INC. RAPisn—KOW2sat- ftjec1A2W2601WWP Page 9