7000 HARDESON RD Geotech Report 2022-10-25

• Geotechnical Engineering Report Community Transit Merrill Creek Operating Base 7100 Hardeson Road Everett, Washington February 28, 2018 RN File No. 3224-002A Page 3 summed. These numbers are then converted to a hammer energy transfer standard which is 60 percent, N60. 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. 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 21. We explored the possibility of either a clogged drain system or a beak in a water line contributing to the surface water. The drain system was flushed out so a video camera could inspect the lines to determine if any breaks were visible. However, the camera was unable to clearly 'see' through the water in the drain line. CT then closed the valve on the water line and observed the meter to determine if there was a break in that system. The water meter did not move during the shut off period, indicating no break in the line. 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 through 21. Our explorations generally encountered a surficial layer of fill ranging in thickness from approximately 10 to 29 feet. The fill varied in composition and density from loose to very dense silty sand with gravel and sand with silt and gravel to stiff silt with sand and wood. Traces of clay and wood debris were noted within the fill in Borings 6 through 12. The fill extended to the depths of the explorations in the shallow Borings 1 through 5 and to depths ranging from 14 to 29 feet in the remaining borings. Below the fill we generally encountered medium dense to very dense fine to coarse sand with varying amounts of silt and gravel interpreted as Advance Outwash. In these explorations this material extended to the depth explored. Laboratory Testing We completed grain size and moisture content testing on selected samples from our explorations. The moisture contents are shown on the boring logs. The grain size results are presented as Figures 23 and 24. Hydrologic Conditions Groundwater seepage has been observed throughout the asphalt paved areas of the site. Shallow groundwater seepage was encountered directly below the asphalt while drilling Borings 6 and 7 and at depths ranging from 8 feet in Boring 9 to 14 and 15 feet, respectively, in Borings 6 and 7. We installed groundwater monitoring wells in four of the borings to determine if groundwater was contributing to the water expressed on the surface of the pavement. We also installed pressure transducers in three of the standpipes (Borings 6, 7 and 9) where we Robinson Noble, Inc.