10901 27TH AVE SE Geotech Report 2025-07-29

1 ' Subset face Exploration, Geologic Hazards, and Proposed James Monroe Elementary School Replacement Revised Geotechnical Engineering Report Everett, Washington Design Recommendations • ' components. Alternative) the frozen material could be stripped from the subgrade to reveal P Y, pp g unfrozen soil prior to placing subsequent lifts of fill or foundation components. The frozen ' soil should not be reused as structural fill until allowed to thaw and adjusted to the proper moisture content, which may not be possible during winter months. 10.0 STRUCTURAL FILL All references to structural fill in this report refer to subgrade preparation, fill type and 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, the upper 12 inches of exposed ground in areas to receive fill should be recompacted to 90 percent of the modified Proctor maximum density using ASTM:D 1557 as the standard. If the subgrade contains silty soils and 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 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 the modified Proctor maximum density using ASTM:D 1557 as the standard. In the case of roadway and utility trench filling, the ' backfill should be placed and compacted in accordance with current City of Everett codes and standards. The top of the compacted fill should extend horizontally outward a minimum distance of 3 feet beyond the locations of the roadway edges before sloping down at an angle ' of 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 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 conditions. The native and existing fill soils present on-site contained significant amounts of 1 silt and are considered highly moisture-sensitive. These on-site soils are expected to be suitable for reuse in structural fill applications during dry site and weather conditions when ' October 5, 2009 ASSOCIATED EARTH SCIENCES, INC. DWG/Id-KE090312A3-Projects1200903121KE1WP Page 15 1