5816 25TH AVE W Geotech Report 2025-06-25

Kierstein Residence Retaining Wall Everett Washington Geotechnical Engineering Report Structural Fill All fill placed beneath or behind the SierraScape wall shall be considered structural fill. All references to structural fill in this letter-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 letter-report, the value given in that section should be used. Any existing site soils containing organics or debris should be stripped from all areas to receive structural fill. The existing grade should then be compacted to a firm and non-yielding condition. After recompaction or remediation of the exposed ground is approved, structural fill may be placed as required 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 at least 95 percent of the modified Proctor maximum density using ASTM D-1557 as the 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 fill and pre-Fraser sand contain low to moderate amounts of silt and are considered slightly to moderately moisture-sensitive. Based on the field moisture contents, the near-surface native soils appear to be near optimum moisture content for compaction. If structural fill is to be placed during wet weather and proper compaction cannot be obtained with the on-site soils, a select material consisting of a clean, free-draining gravel and/or sand should be used. Free-draining fill consists of non-organic soil with the amount of fine-grained material limited to 5 percent by weight when measured on the minus No. 4 sieve fraction. A representative from AESI should observe the stripped subgrade and be present during placement of structural fill to observe the work and perform a representative number of in-place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses and problem areas may be corrected at that time. Our field technicians and engineers are available to aid the owner in developing a suitable monitoring and testing program, such that quality control is adequately provided. Wall Drainage It is imperative that proper drainage be provided so that hydrostatic pressures do not develop behind the wall. The wall should be provided with a minimum 1-foot-wide blanket drain for within 8 inches of the full wall height and a chimney drain behind the geogrid reinforced zone using imported, washed crushed gravel and a drain pipe consisting of rigid, perforated, polyvinyl chloride (PVC) pipe surrounded by washed crushed gravel. The drains should be July 1, 2022 ASSOCIATED EARTH SCIENCES,INC. SASlih-20180614EO01-002 Page 7