1343 MADRONA AVE Geotech Report 2022-10-25

Geotechnical Engineering Report Stark Residence Addition 1343 Madrona Avenue Everett, Washington December 8, 2014 RN File No. 2902-001A Page 3 Explorations We explored subsurface conditions within the site on November 13, 2014, by drilling two borings with a portable hollow stem auger drill rig and advancing one hand augered boring with hand-held equipment. The borings were drilled to depths ranging from 5.0 to 21.0 feet below the ground surface. Samples were obtained from the drilled borings at 2.5 and 5-foot intervals by driving a split spoon sampler with a 140-pound hammer dropping 30 inches. The number of blows required for penetration of three 6-inch intervals was recorded. To determine the standard penetration number at that depth the number of blows required for the lower two intervals are summed. If the number of blows reached 50 before the sampler was driven through any 6-inch interval, the sampler was not driven further and the blow count is recorded as 50 for the actual penetration distance. Samples were obtained from the hand-augered exploration at 1.0 to 1.5-foot intervals. The borings were located in the field by an engineer from this firm who also examined the soils and geologic conditions encountered, and maintained logs of the borings. The approximate locations of the borings are shown on the Site Plan in Figure 2. The soils were visually classified in general accordance with the Unified Soil Classification System, a copy of which is presented as Figure 3. The logs of the borings are presented in Figures 4 through 6. Subsurface Conditions A brief description of the conditions encountered in our explorations is included below. For a more detailed description of the soils encountered, review the Boring Logs in Figures 4 and 5, and the Hand Auger Log in Figure 6. Our drilled explorations generally encountered a surficial layer of topsoil that was less than 1.5 feet in thickness. The topsoil consisted of loose, dark brown silty fine sand with grass roots. Underlying the topsoil we encountered medium dense to very dense silty sand with varying amounts of gravel and silt interbeds to the depths explored. In the hand augered bore hole we encountered stiff gray silt with varying amounts of sand and gravel. The silt appeared disturbed and blocky at a depth of 4.5 feet below ground surface. This material extended to the depth explored. Hydrologic Conditions Groundwater was encountered in Boring 1 at 12.0 feet, Boring 2 at 8.0 feet and Hand Auger 1 at 4.5 feet. The seepage appears to be interflow within the sand seams and likely does not represent the regional groundwater table. Volumes of groundwater vary depending upon the time of year and the upslope recharge conditions. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion that the site is compatible with the planned development. The underlying medium dense to very dense transitional bed deposits are capable of supporting the planned structure. We recommend that the foundations for the structure extend through any fill, topsoil, Robinson Noble, Inc