607 RIVERSIDE RD Geotech Report 2022-10-25 (2)

I March 22,2016 Project No. T-7388 It should be noted that the recommendations outlined in this report regarding drainage are associated with soil strength, erosion, and stability. Design and performance issues with respect to moisture as it relates to the structure environment(i.e.,humidity,mildew,mold)are beyond Terra Associates' purview. A building envelope specialist or contractor should be consulted to address these issues,as needed. 3.0 SITE CONDITIONS 3.1 Surface The undeveloped site consists of 2 tax parcels, Lots 5 and 6, having a combined area of 13.62 acres. The site is bounded to the north and east by adjoining parcels within Riverside Business Park. A Port of Everett access road and Riverside Road bound the site to the south and west, respectively. The approximate location of the site is shown on Figure 1. The site's southern area and western margin approximately match the adjacent access road and Riverside Road grades, respectively. From these areas, grades rise three to five feet to a fill pad covering the majority of both Lots 5 and 6. At the time of our visit, the relatively level fill pad's surface predominantly consisted of exposed soil, with vegetation consisting of sparse grasses and weeds. Areas of ponded water on the fill pad were observed during our visit. 3.2 Soils The site soils generally consist of 4 Y2 feet to 8 1/2 feet of fill overlying native alluvium. Test Pit TP-9 was terminated within rubble fill from a depth of 9 to 11 feet. The fills mainly consist of medium dense silty sand with few cobbles, and variable gravel and organics contents. The alluvial soils consist of medium dense sand to silty sand to the majority of the test pit's total depths, with TP-11 showing soft organic silt beneath the alluvial sands to its total depth. Caving of test pit walls was noted at varying depths in several of the test pits. Large obstructions consisting of a boulder and construction rubble were encountered in four of our test pits, and in explorations at the site previously completed by others. Test Pit TP-12 was moved 5 feet to the north after encountering wood boards and planks at a depth of 4 1/2 feet. The obstructions and rubble were primarily found within the lower fills. The soil types and strengths indicated on the CPT logs generally correlate with soils noted in the test pits. The CPT logs show the fills in a predominantly medium dense condition underlain by loose/soft silt and clay zones. The soft silt and clay is underlain by medium dense to dense alluvial sands found to the total depths of the CPTs. Test Boring B-1, completed by Landau Associates, Inc. in the Riverside Road right-of-way showed sand to a depth of four feet overlying a 12-foot thick layer of very soft silt with organics. Medium dense alluvial soils were found beneath the very soft silt. Landau Associates' Test Borings B-9 and B-10, advanced on the present fill pad, showed loose to medium dense fill to a depth of seven feet overlying the loose to medium dense alluvial sands. I Page No. 2 I