3611 FEDERAL AVE 2018-01-02 MF Import

' (ienloYic Investigation and Gearechnical Engineering Report 98-08-10 Jones Residence ' 3611 Federal:I ve. E*verett. Washington 3.3 Site Stratieraahy Site stratigraphy has been interpreted from the soil information collected during our field investigation and correlated with the mapped geology of the area. Six-(6) test pits were excavated with a rubbe( tired backhoe in locations selected by GES, Inc. The locations of the test pits are shown on the Site Map in Appendix B of this report. These test pits were located around the project site in such a way so as to provide optimum information concerning the shallow subsurface soil conditions at the time of the site investigation work. The test pits were logged by an engineering geologist from GES, Inc. as they were being excavated. Soil descriptions were developed following the Unified Soil Classification (U.S.C.) format. Copies of the U.S.C. format and the Test Pit Logs are contained in Appendices D and E. respectively, located at the end of this report. According to the Geologic Map, the site lies in an area geol / mapped as Vashon Advanced Outwash (Ova) deposits. Advanced Outwash (Qro) deposits co, of dense to very dense, tine- to coarse -grained sands. Advance Outwash (Ova) deposits typically underlies Vashon Glacial Till (Orr). Glacial Till (Orl) is a compact mixture of sand, silt, and gravel that was laid down as a lodgment till beneath the advancing Vashon aged glaciers. Glacial Till (Ovl) and the underlying Advance Outwash (Ova) soil have been overridden by thousands of feet of glacial ice (overconsohdaled), creating very dense and stable soil formations. 1 Site stratigraphy based on the soil excavated in the test pits shows that silt and not the me- to coarse- , grained sands of the Advance Outwash (Qva) underlie this site. Very dense, massive gray silt was found between five and one-half (5-1 2) feet and eleven and one-half (11-1 2) feet below existing site grades at the test pit locations. Locally, this very dense silt took on a consistency similar to a siltstone. In many instances, exposed surfaces in materials dug up in the test pits were shinny or slightly polished, showing I signs of shearing or possible slickensides. The age of this distress is unknown, but no recent movements or landslides have been mapped in this area according to the Geologic Map. Weathered silt, with a slightly less dense consistency, was found in all locations overlying the basal very dense silts. The weathered silt was slightly mottled and was colored red brown to gray brown. It dug 5 . GES, Inc.