2102 ROSS AVE 2018-02-23 - Laserfiche WebLink

McClean Iron Works Pier Project NGA File No. 7903B16 2102 Ross Avenue October 28,2016 Everett,Washington Page 2/ f; Subsurface Conditions Geology: The geologic units for this area are shown on the "Geologic Map of the Marysville Quadrangle, Snohomish County, Washington," by James P. Minard (U.S.G.S., 1985). The site is mapped as Younger Alluvium (Qyal). Younger alluvium is described as stream-laid stratified sediment consisting of sand, silt, and clay with considerable amounts of organic matter. Explorations performed by others within the site generally encountered undocumented fill underlain by peat and interbedded silt and sand consistent with the description of the younger alluvium. Explorations by Others: The subsurface conditions within the site were explored by others by excavating six test pits and by drilling two borings to a depth of 49 feet below the existing ground surface. The borings were drilled using a trailer-mounted drill rig. We reviewed the exploration logs of the previously performed explorations and present a brief interpretation of the subsurface conditions as described in those logs in the following paragraph. The test pits encountered loose to medium dense, fine to coarse sand that was interpreted as undocumented fill. The test pits were terminated within the undocumented fill at depths between approximately 8 and 9 feet below the existing ground surface. The two borings (EB-1 and EB-2) encountered approximately 9 to 12 feet of very loose to medium dense,medium sand with varying amounts of gravel that was interpreted as undocumented fill. Underlying the fill, the borings encountered approximately 12 to 14 feet of very soft, peat, clay/silt, and varying amounts of sand overlying medium dense to dense fine to medium sand with varying amounts of silt. These soils described in the exploration logs appear to be consistent with the description of younger alluvium deposits. Hydrologic Conditions Groundwater was encountered at approximately 7 to 8 feet below the ground surface in the explorations. The groundwater is most likely part of the regional groundwater regime for the area and may be associated with the river stage in the Snohomish River. Test Pin Piles In 2008, NGA observed the installation of two Schedule 40, galvanized steel pipe piles with nominal diameters of 4 inches and 6 inches. The 4-inch and 6-inch piles were driven to refusal to approximately 47 and 54 feet below the existing ground surface,respectively. The refusal criterion was less than 3 inches of penetration per minute of continuous driving with a hydraulic hammer with an energy rating of 2,000 foot- pounds. The 4-inch diameter pile was successfully load tested to 22 tons(44,000 pounds or 44 kips),which was 200 percent of the design capacity of 11 tons(22 kips) per pile. The 6-inch pile was tested to 26 tons NELSON GEOTECHNICAL ASSOCIATES, INC.