3410 TERMINAL AVE 2018-03-09 - Laserfiche WebLink

I .' Estuarine Deposits [He]. The fill soils are underlain by about 10 feet of Holocene estuarine silt deposits. Estuarine deposits generally consist of very soft to stiff, low- plasticity silt and clayey silt to silty clay with minor amounts of fine sand. Interbeds of organic-rich soils may be present within this unit. • Alluvium Deposits [Ha] About 10 feet of Holocene alluvium were encountered below the fill and estuarine deposits in our boring. The alluvial deposits were likely deposited by the Snohomish River during formation of the Snohomish delta. These soils are generally granular and consist of sand, silty sand, and gravelly sand. In the borings, these deposits were very loose to loose near the top of the layer and increased to dense at the bottom of the layer. • Beach Deposits [Hb]. Beach deposits are typically located at or near the base of ' Holocene units and in our boring were approximately 15 feet thick. Beach deposits typically consist of medium dense to very dense sand and gravel and may also contain scattered cobbles and locally cohesive fines. Scattered to abundant shell fragments and wood debris are commonly observed in these soils. ■ Pre-Vashon(Glacially Overridden)Deposits. Pre-Vashon deposits were encountered to the lowest extent of our boring beneath the beach deposits. The soils were deposited before the last(Vashon) glaciation between and during the many other glaciations experienced in the Puget Sound region. This means that these soils have been overridden by glaciers and thus are highly overconsolidated. Subsets of these ' pre-Vashon deposits encountered in our boring include glaciolacustrine(Qpgl), glacial outwash(Qpgo), fluvial deposits (Qpnf), and lacustrine(Qpnl). Groundwater level measured in our boring was approximately 10 feet deep at the time of drilling. Given the close proximity to the Puget Sound, it is likely that the groundwater level is tidally influenced and will often differ from that measured in our boring. We would expect that the groundwater level near the boring is typically higher than the water level of the Puget Sound. ' 6.0 ENGINEERING STUDIES AND RECOMMENDATIONS 6.1 General Based on the subsurface conditions at the site described previously and our understanding of the project, engineering studies were performed to develop conclusions and recommendations for design of the wharf upgrade. We developed two idealized site profiles based on our boring, ' historical borings, and pile lengths of the existing wharf These profiles were assumed near rows A and H. For purposes of our analyses and recommendations, it was assumed that the site soils could be linearly interpreted between these two profiles. ' 21-1-21962-003-R2.docx/wp/cp 21-1-21962-003 7