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February 28, 2023 G-5835 <br /> 3821 —Shore Ave Everett,WA Page 8 <br /> lesser than the optimum moisture content cannot be effectively compacted to an acceptable dense <br /> condition. <br /> If structural fills are required to achieve design site elevations, then we recommend the use of an <br /> imported granular fill material which may provide more uniformity and be easier to compact to <br /> the required structural fill specifications, especially during periods of wet weather. <br /> If desired, the sites sandy and gravelly soils may be used as structural fill, however, due to their <br /> fine-grained gradation and anticipated moisture content,additional effort should be anticipated to <br /> achieve the recommended soil moisture and compaction specifications. <br /> Structural and non-structural fill material should be placed in horizontal lifts not exceeding 12 <br /> inches in loose thickness. Each lift of structural fill material should be compacted to at least 92 <br /> percent of the material's maximum dry density,as determined by ASTM Test Designation D- <br /> 1557-91 (Modified Proctor Test), or as approved by the geotechnical engineer. Non-structural fill <br /> material should be compacted to a firm and unyielding condition, as approved by the <br /> geotechnical engineer. <br /> During wet weather conditions, an imported granular material containing no more than five(5) <br /> percent fines (i.e.,particles passing a U.S. No. 200 mesh sieve) is recommended for use as <br /> structural fill,because it will provide uniformity in character and be relatively easy to compact to <br /> structural specifications. We recommend that the geoteclinical engineer monitor the placement <br /> and compaction of structural fill in order to verify conformance with the above <br /> recommendations. <br /> Retaining Wall Support <br /> We recommend the retaining wall be supported on the soils suitable for supporting the retaining <br /> wall that were encountered at depths below approximately 2.0 feet bgs in boring HA-1 during <br /> our subsurface investigation. Soils suitable for supporting the retaining wall were not <br /> encountered in boring HA-2. Therefore, we recommend that soils underlying the southern <br /> (approximately 30 feet) extent of the retaining wall be amended and prepared to a suitable <br /> condition for supporting the retaining wall. our recommendations for structural fill compaction <br /> i <br /> specifications are provided in the Structural and Non-Structural Fill section of this report. <br /> f <br />�4f[ <br /> E <br /> GEO Group Northwest, Inc. <br />