3000 41ST ST Geotech Report 2025-12-31

PNW Home Builders, LLC ES-2598.03 May 2, 2013 Page 7 Imported Soils Imported soil intended for use as structural fill should consist of a well-graded granular soil with a moisture content that is at or near the optimum level. During wet weather conditions, imported soil intended for use as structural fill should consist of a well-graded granular soil with a fines content. of five percent or less defined as the percent passing, the Number 200 sieve, based on the minus three-quarter inch fraction. Building and Pavement Subgrade Preparation Subgrade conditions expected to be exposed throughout the proposed building and pavement areas will likely be comprised of silty sand and sandy silt (SM and SP). The soils exposed throughout subgrade areas should be compacted to structural fill specifications prior to constructing the foundation, slab, and pavement elements. The subgrade throughout new pavement areas should be compacted as necessary to exhibit a firm and unyielding condition when subjected to proofrolling with a loaded dump truck. Structural fill soils placed throughout foundation, slab, and pavement areas should be placed over a firm_ base. Loose or otherwise unsuitable areas of native soil exposed at subgrade elevations should be compacted to structural fill requirements or overexcavated and replaced with a suitable structural fill material. Where structural fill soils are used to construct foundation subgrade areas, the soil should be compacted to the requirements of structural fill described in the following section. Foundation subgrade areas should be protected from disturbance, construction traffic, and excessive moisture. Where instability develops below structural fill areas, use of a woven geotextile below the structural fill areas may be required. A representative of ESNW should observe structural fill placement in foundation, slab, and pavement areas.. Structural Fill Structural fill is defined as compacted soil placed in foundation, slab-on-grade, and roadway areas. Fills placed to construct permanent slopes and throughout retaining wall and utility trench backfill areas are also considered structural fill. Soil placed in structural areas should be placed in loose lifts of 12 inches or less and compacted to a relative compaction of 90 percent, based on the laboratory maximum dry density as determined by the Modified Proctor Method (ASTM D1557). Soil placed in the upper 12 inches of slab-on-grade, utility trench, and pavement areas should be compacted to a relative compaction of at least 95 percent. Additionally, more stringent compaction specifications may be required for utility trench backfill zones, depending on the responsible utility district or jurisdiction. Foundations Based on the results of our evaluation, the proposed residential buildings should be supported on a conventional foundation system achieving bearing on at least two feet of structural fill following the successful completion of a surcharge or preload program. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with structural fill may be necessary. Earth Solutions NW,LLC