11831 AIRPORT RD WHOLE SITE FILE Geotech Report 2022-10-25

Laboratory Testing Soil samples were obtained during drilling and taken to GeoEngineers' laboratory for further evaluation. Selected samples were tested for the determination of moisture content, grain size distribution, and Atterberg limits (plasticity characteristics). A description of the laboratory testing and the test results are presented in Appendix B, Laboratory Testing. PREVIOUS STUDIES In addition to the explorations completed for this study, we reviewed available logs of explorations completed as part of previous studies in the project vicinity.The existing information was obtained largely through the Pacific Northwest Center for Geologic Mapping Studies(GeoMapNW), which is a collaborative effort to develop a database of geologic information that is being compiled by the United States Geological Survey(USGS),the University of Washington,and others. The previous studies reviewed include: ■ logs of borings completed by the Washington State Department of Transportation (WSDOT) for the SR 527 widening project; ■ logs of borings and test pits completed by Terra Associates for intersection improvements at 128th Street SE and Elgin/Dumas Way project;and ■ logs of test pits completed by Snohomish County for a project along Airport Road and 128th Street SE. The approximate locations of useful explorations in the immediate vicinity of the project corridor are shown on Figures 2A through 2R. The corresponding exploration logs are included in Appendix D, Previous Explorations. We reviewed additional reports and logs from nearby projects in our files, which are not included in this report. SITE CONDITIONS Setting The project is located from Bothell to Everett, starting at the Canyon Park Park-and-Ride, and extending to the north along both sides of SR 527, 132nd Street SE, 128th Street SE, and Airport Road. Most of the roadways along the alignment are four lanes or more in width, and have a mixture of residential and commercial developed properties along most of the alignment. Many of the new stations will require retaining walls which will often be located on existing embankments, or cut slightly into existing embankment slopes.Other areas of note include the following: ■ the planned new station on the south side of 132nd Street SE is situated close to the east edge of the former Emander Landfill; ■ a proposed new retaining wall along the entrance to north-bound 1-5 ramp, referred to as Wall 2, will require removal of an existing block wall situated along the existing right of way.This new wall will be 4 feet to more than 12 feet in height, depending on the final alignment selected; GEOENGINEERS_O April 14,2017 Page 2 File No.2095-032-00