1502 WALL ST IMAGINE CHILDRENS MUSEUM Geotech Report 2022-10-25

r � Imagine Children's Museum Building Addition Revised Geotechnical Engineering Report Everett, Washington Project and Site Conditions 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 Borings The exploration borings were completed by advancing a 4%-inch, inside-diameter, hollow-stem auger with a truck-mounted drill rig. During the drilling process, samples were obtained at generally 2%- to 5-foot-depth intervals. The exploration borings were continuously observed and logged by a geologist from our firm. The exploration logs presented in the Appendix are based on the field logs, drilling action, and inspection of the samples secured. Disturbed, but representative samples were obtained from the exploration borings by using the Standard Penetration Test procedure in accordance with American Society for Testing and Materials (ASTM) D-1586. This test and sampling method consists of driving a standard 2-inch, outside-diameter, split-barrel sampler a distance of 18 inches into the soil with a 140-pound hammer free-falling a distance of 30 inches. The number of blows for each 6-inch interval is recorded, and the number of blows required to drive the sampler the final 12 inches is known as the Standard Penetration Resistance ("N") or blow count. If a total of 50 is recorded within one 6-inch interval, the blow count is recorded as 50 blows for the corresponding number of inches of penetration. The resistance, or N-value, provides a measure of the relative density of granular soils or the relative consistency of cohesive soils; these values are plotted on the attached exploration boring logs. The samples obtained from the split-barrel sampler were classified in the field and representative portions placed in watertight containers. The samples were then transported to our laboratory for further visual classification and laboratory testing, as necessary. 4.0 SUBSURFACE CONDITIONS Subsurface conditions at the project site were inferred from the field explorations reviewed for this study, and review of selected geologic literature. As shown on the field logs and detailed below, the explorations encountered native sediments that consisted of dense to very dense silty sand with gravel interpreted as Vashon lodgement till. We reviewed published geologic mapping for the project area using the published geologic map titled Geologic Map of the Everett 7.5-Minute Quadrangle, by J.P. Minard, 1985, U.S. Geological Survey (USGS), Miscellaneous Field Studies Map MF-1748. The published map indicates that Vashon lodgement till sediments are expected at shallow depth on the site. Our observations and interpretations for this project are consistent with the referenced published geologic map. These soils are generally adequate for support of shallow foundations, but are not favorable for stormwater infiltration purposes, and are considered highly moisture- sensitive and easily disturbed when wet. March 28,2019;Revised April 16,2019 ASSOCIATED EARTH SCIENCES INC SGB/Id-190104E001-3-Projects\20190104\KE‘WP r'r Page 4