3322 KROMER AVE Geotech Report 2023-05-25

GeoTest Services, Inc.—Revision 1 April 10,2020 Kikuchi Retaining Wall, Everett,Washington Project No. 20-0344 • simow provided the material is properly moisture conditioned prior to placement and compaction, and the specified degree of compaction is obtained. Material containing topsoil,wood,trash, organic material, or construction debris is not suitable for reuse as structural fill and should be properly disposed offsite or placed in nonstructural areas. Soils containing more than approximately five percent fines are considered moisture sensitive and are difficult to compact to a firm and unyielding condition when over the optimum moisture content by more than approximately two percent. The optimum moisture content is that which allows the greatest dry density to be achieved at a given level of compactive effort. Reuse of On-Site Soil Reuse of existing, uncontrolled fill as structural fill may be feasible if the encountered soil is free of organics, debris, refuse, and similar unsuitable materials, and if the material is placed at or near optimum moisture contents as determined by ASTM D1557. If existing fill is not suitable for reuse, it should be removed from the site or used in non-structural applications. Reuse of the native transitional beds as structural fill may be feasible if properly moisture conditioned. It should be understood, however, that both existing fill soil and transitional bed materials have elevated silt contents and should be considered moisture sensitive. It should be expected that moisture conditioning will be required in order to reuse native soils in structural fill applications. The successful moisture conditioning of on-site soils is anticipated to be highly dependent on the season of construction, weather conditions, construction timeline, and the contractor's means and methods. Both the existing fill and native soils will exhibit in-place moisture contents above optimum moisture contents for compaction. Moisture conditioning programs typically require significant amounts of space, time, and extended dry conditions that allow for thin layers of soil to be tilled and dried to reduce soil moisture to a condition more optimum for compaction. Thus, there should be reasonable expectations that on-site soils may have challenges if they are to be used as structural fill materials,especially during prolonged periods of rainfall. If on-site soils are to be used as structural fill at the site,we recommend that GeoTest be involved with the planning and construction monitoring for fill placement activities. Imported Structural Fill GeoTest recommends that imported structural fill consist of clean, well-graded sandy gravel, gravelly sand, or other approved naturally occurring granular material (pit run) with at least 30 percent retained on the No.4 sieve, or a well-graded crushed rock. Structural fill for dry weather construction may contain up to 10 percent fines (that portion passing the U.S. No. 200 sieve) based on the portion passing the U.S. No. 4 sieve. The use of an imported fill having more than 14