1515 132ND ST SE Geotech Report 2022-10-25

Proposal for Geotechnical Engineering Services Proposed Bank: 1515 132nd Street Southeast, Everett, Washington March 15, 2019 In our opinion, the predominately silty sand and silt soils underlying the site are not suitable for use as wall backfill. Wall backfill should be moisture conditioned to within about 3 percent of optimum moisture content, placed in loose, horizontal lifts less than 8 inches in thickness, and systematically compacted to a dense and relatively unyielding condition and to at least 95 percent of the maximum dry density, as determined using test method ASTM D-1557. Within 5 feet of the wall, the backfill should be compacted with hand -operated equipment to at least 90 percent of the maximum dry density. 5.5 PERMANENT CUT AND FILL SLOPES Based on the anticipated soil that will be exposed in the planned excavation, we recommend permanent cut and fill slopes be constructed no steeper than 2H:1 V (Horizontal: Vertical). 6.0 EARTHWORK CONSIDERATIONS 6.1 STRIPPING, CLEARING AND SUBGRADE PREPARATION Foundation and pavement areas, and areas to receive structural fill, should be stripped and cleared of surface vegetation, organic matter, existing pavements, and other deleterious materials. In no case should stripped materials be used as structural fill nor should they be mixed with materials to be used as structural fill. Outside of construction areas, the existing site pavement may be left in -place to provide an all-weather construction surface. In areas where existing foundations, slab -on -grade floors, and pavements are removed, it may be possible to crush the existing materials for re -use as structural fill. Materials reclaimed by crushing to be re -used as structural fill should have a maximum particle size of four inches and should be mixed with soil to provide a well -graded fill material. Existing underground utilities to be abandoned should be plugged or removed so they do not provide a conduit for water and cause soil saturation and stability problems. Following the stripping operation and excavations necessary to achieve construction subgrade elevations, the ground surface where structural fill, or pavements are to be placed should be observed by PanGEO. Proofrolling using a fully loaded dump truck should be performed to identify soft or unstable areas. 19-049 1515 132nd St SE Page 10 PanGEO, Inc.