1528 GRAND AVE Geotech Report 2022-10-25

GeoTest Services, Inc. Report Date 7/17/2019 Anderson Residence- Everett, Washington GTS Project No.19-0384 err- ni:g0 Surface Conditions The existing residence shares an asphalt-paved driveway with the house to the north. The house has a "walk-out" style basement that opens in the back of the house to a paved carport covered by an elevated wooden deck. A short rockery wall retains a thickly vegetated mound along the southern property boundary, and a concrete wall with a metal fence separates the backyard from a steep slope down to Marine View Drive approximately 70 feet below. The slope is densely vegetated with blackberry bushes and deciduous trees.The backyard beyond the carport and deck is covered in landscaped grass with a small gravel bed and some shrubs. Subsurface Soil Conditions Subsurface conditions were explored on June 24, 2019 by advancing four hand-auger test holes and dynamic cone penetrometer (DCP) tests at the approximate locations shown on Figure 2.The hand-auger explorations were advanced to depths of up to 13 feet; DCPs were advanced up to approximately 10 feet deep. Two of the explorations (HA/DCP-2 and HA/DCP-3) were located in the backyard near the crest of the steep slope,and the remaining two (HA/DCP-1 and HA/DCP-4)were advanced inside sawcut areas in the existing residence basement slab. Soils encountered near the top-of-slope condition generally consisted of slightly silty to silty sand that was loose to very loose to a depth of about 6 to 8 feet below ground surface (BGS). The density of the soil and proximity to the slope suggests that this material is historic fill that was placed during initial lot construction. Underlying the fill to the depths of our explorations was loose, medium grained sand with low silt contents that were interpreted to be representative of Recessjonal Outwash. Soils underlying the existing residence consisted of variable-density sand with relatively low silt and gravel content. These soils were interpreted to be representative of Recessional Outwash. General Geologic Conditions Geologic mapping of the project area was obtained from the Geologic Map of the Everett 75-Minute Quadrangle (Minard, 1985). The property is mapped as a unit of glacial outwash (Qva) described as clean,gray, unconsolidated sand with pebbles and some cobbles that is locally silty and oxidized to shades of brown. These soils were deposited by seasonal meltwaters from the advancing Vashon glacier. They lie conformably atop the downslope, adjacent mapped unit of transitional beds (Qtb), described as clay, silt, and very fine to fine sand with local vertical jointing. The 2