1707 SCENIC DR SNO CO PUD Geotech Report 2022-10-25

engineering services were completed in accordance with our agreement with the Snohomish County Public Utility District(PUD), dated September 24, 2013. FIELD EXPLORATION AND LABORATORY TESTING Field Explorations The subsurface conditions at the site were evaluated by drilling nine borings, B-1 through B-9, and excavating seventeen test pits, TP-1 through TP-17. Borings B-1 through B-5 and test pits TP-1 through TP-11s were completed in 2009 and supplemental borings B-6 through B-9 and test pits TP-12 through TP-17 were completed in 2014. The borings and test pits were completed to depths up to 281/z feet and 14 feet below grades, respectively. Pilot infiltration tests (PIT) were conducted within test pits TP-12 and TP-17. The approximate locations of the explorations are shown on the Site Plan, Figure 2. A detailed description of the field exploration program is presented in Appendix A. Laboratory Te�ting Soil samples were collected from the explorations, taken to our laboratory and examined to confirm or modify field classifications, as well as to evaluate engineering properties of the soil. Representative samples were selected for laboratory testing consisting of determination of moisture content and grain size distribution. A description of the laboratory testing and the test results are presented in Appendix B. Previous Studies We reviewed a previous geotechnical study(Zipper Zeman Associates, Inc., 2003)that was completed for some of the existing dead end structures at the substation. The report includes the log of borings B-1, B-2, and B-3 that were drilled for the dead end towers. The approximate locations of borings are shown on the Site Plan, Figure 2. The boring logs are included in Appendix C. SITE CONDITIONS Surface Condition� The southwestern portion of the site is currently developed with the existing 115kV substation. The existing substation yard is roughly 450 feet by 150 feet and has a relatively level grade at about Elevation 429 feet. The yard is enclosed by a security fence and is surfaced with crushed rock. The undeveloped portion of the property is located east of the existing 115kV yard and is overgrown with blackberry bushes and small shrubs. The site is relatively flat to the north about 100 feet beyond the security fence and then slopes down to the north at approximately 3H:1V (horizontal:vertical). The site also slopes down to the east beyond the east security fence at approximately 3H:1V. Portions of the existing slopes have been mapped as steep slopes based on interpretation of topographic drawings. Wetlands have also been mapped east of the planned expansion. The locations of existing site features with respect to the proposed improvements are shown on the Site Plan, Figure 2. GEOENGINEER� October24,2014 Page2 Fie raa.aasz-oz�-oz