3620 W MUKILTEO BLVD Geotech Report 2025-08-13

Geotechnical Engineering Evaluation • Mukilteo Boulevard Development Everett,Washington March 31,2003 NGA File No. 366503 Page 4 outwash. Fill material was encountered in one of the explorations. Explorations: The subsurface conditions were explored at the site on March 19, 2003 by excavating eleven test pits to depths of 4.2 to 14.2 feet below the existing ground surface using a backhoe. The explorations were located in the field by an NGA engineer who also examined the soils and geologic conditions encountered and maintained logs of the test pits. The approximate locations of our explorations are shown on the Site Plan in Figure 2. The soils were visually classified in general accordance with the Unified Soil Classification System,presented as Figure 3. The logs of our explorations are presented as Figures 4 through 6. We present a brief summary of the subsurface conditions in the following paragraphs. For a more detailed description of the site soils, the test pit logs should be reviewed. Our subsurface explorations encountered a surficial layer of topsoil 0.9 to 2.1 feet thick. The subsurface soils were highly variable,not only between different test pit locations but also in individual explorations. Typically, the test pits encountered several different layers of soil approximately each layer was two to four feet in thickness. The different soil types included: silty fine to medium sand with fine gravel, silt, silty fine to medium sand, silty fine sand, silty fine sand with occasional gravel pockets, silt with fine sand, silt with fine to medium sand, silty fine to coarse sand with fine gravel, silty fine sand/sandy silt, fine sand, medium to coarse sand, silty fine to coarse sand with gravel, and medium to coarse sand with gravel and cobbles. We have interpreted these materials as glacial drift and recessional outwash. In Test Pit 11, the topsoil was underlain by loose silty fine to medium sand, evaluated as fill, which extended to a depth of 2.8 feet. A layer of buried topsoil, 0.2 feet thick,was observed below the fill soils. The materials we observed beneath the buried topsoil were generally more granular and less moisture- sensitive than the soils encountered in the other explorations. These included: silty fine to medium sand, silty fine to coarse sand with gravel,medium to coarse sand with gravel and cobbles, and fine sand. Hydrologic Conditions:,Slight ground water seepage was encountered in Test Pits 2,3,4,5,and 9. This seepage was encountered above relatively impermeable materials,and is interpreted to be perched ground water. Perched ground water occurs when surface water infiltrates through more permeable, near-surface soils, NELSON GEOTECHNICAL ASSOCIATES,INC. EXHIBIT # l J PAGE 7OF Z4