8102 EVERGREEN WAY Geotech Report 2025-08-04

DevCo, Inc. ES-6516 April 1, 2019 Page 3 Subsurface An ESNW representative observed, logged, and sampled five borings, advanced within accessible locations of the property boundaries, on January 24, 2019, using a truck-mounted drill rig and operators retained by our firm. The borings were completed for purposes of assessment and classification of site soil and groundwater conditions. The approximate locations of the borings are depicted on Plate 2 (Boring Location Plan). Please refer to the boring logs provided in Appendix A for a more detailed description of subsurface conditions. Representative soil samples collected at the boring locations were evaluated in accordance with both Unified Soil Classification System (USCS) and United States Department of Agriculture (USDA) methods and procedures. Topsoil and Fill A topsoil horizon was not encountered during our January 2019 subsurface exploration. Given the current level of development, we do not anticipate a uniform topsoil horizon will be encountered during site earthwork activities. Silty sand fill was encountered at B-2 and B-5, extending to depths of about eight and three feet, respectively, below the existing ground surface elevation (bgs). The fill was generally observed in a medium dense and moist condition. We interpret the high Standard Penetration Test values in fill at B-2 to be representative of an obstruction during drilling. Native Soil Underlying topsoil, native soils were encountered primarily as silty sand with gravel (USCS: SM). Well-graded sand was observed at shallow depths within B-4 but appears to be isolated in extent. As such, silty sand with gravel should be considered the primary underlying soil type. In general, the silty sand was encountered in a very dense and moist condition. Native soils were observed extending to the maximum exploration depth of about 20.5 feet bgs. Geologic Setting The referenced geologic map resource identifies Vashon glacial till (Qvt) as underlying the site and surrounding area. According to the geologic map resource, the till is a nonsorted mixture of mud, sand, pebbles, cobbles, and boulders. Locally referred to as "hardpan", glacial till is overconsolidated and typically very compact due to the weight of the overriding ice during previous glaciation events. The referenced WSS resource identifies Alderwood-Urban land complex and Urban land designations (Map Unit Symbols: 5 and 78, respectively) as underlying the site and immediately adjacent areas. The Alderwood series is associated with glacial till plains. Designations of urban land indicates the area has been subject to historic grading modifications. Based on our field observations, native soils are consistent with local geologic mapping and soil survey designations of glacial till. Earth Solutions NW, LLC