2202 100TH ST SW Geotech Report 2022-10-25

4 Subsurface Exploration,Geologic Hazard,and Stephens Everett Property Preliminary Geotechnical Engineering Report Everett, Washington Project and Site Conditions explorations is necessary. It should be noted that differing subsurface conditions may sometimes be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this report and make appropriate changes. 3.1 Exploration Pits The exploration pits for this study were excavated using a steel-tracked 312DL CAT trackhoe, working under subcontract to AESI. The pits permitted direct, visual observation of subsurface conditions. Materials encountered in the pits were studied and classified in the field by a geologist from AESI. After logging the exposed soils, the exploration pits were backfilled with the excavated soil and lightly tamped with the excavator bucket.The various types of materials and sediments encountered in the explorations, as well as the depths where characteristics of these materials changed, are indicated on the exploration logs included in the Appendix. The depths indicated on the logs where conditions changed may represent gradational variations between sediment types in the field. 4.0 SUBSURFACE CONDITIONS Subsurface conditions at the project site were inferred from the field explorations accomplished for this study, visual reconnaissance of the site, and review of selected applicable geologic literature.The general distribution of geologic units is shown on the exploration logs. The explorations typically encountered shallow Vashon-age native sediments consisting of loose to medium dense recessional outwash overlaying dense grading to very dense lodgement till; some explorations did not encounter recessional outwash and lodgement till was present near the surface. Existing fill was not encountered in the explorations completed for this study, but may be present in unexplored areas. Review of a regional geologic map (Geologic Map of Poverty Bay Quadrangle 7.5', King and Pierce Counties, Washington, U.S. Geological Survey [USGS], prepared by Booth et al., 2004) indicates that the subject site is underlain by Vashon lodgement till. Our interpretation of the sediments encountered in our explorations is in partial agreement with the regional geologic mapping. Several of our exploration pits encountered Vashon lodgement till underlying a relatively thin sequence of Vashon recessional outwash. March 29,2019 ASSOCIATED EARTH SCIENCES,INC. TG/ms-180567E001-2-Projects1201805671 KE1 WP Page 3