3535 RIVERFRONT BLVD Geotech Report 2023-02-22

September 24, 2018 HWA Project No. 2015-061-21 Although previously considered in our report from 2017, we understand that shelter holdings may opt out of constructing a new foundation for the existing crane as well as completion of the viewing platform for the crane, and the gangway and floating dock; however, we have kept recommendations for these options in our report at this time. 2. FIELD INVESTIGATION AND LABORATORY TESTING 2.1 GEOTECHNICAL SUBSURFACE EXPLORATIONS A series of subsurface explorations were conducted in June 2010 and September 2011, as part of the preliminary geotechnical investigation for the Group 3 Public Amenities (HWA, 2011 a). For the 3-Acre Park portion of the project, the exploration work consisted of advancing seven borings, designated B-101 through B-107. The approximate locations of these explorations are indicated on Site and Exploration Plan, Figure 2. Each exploration was monitored and logged by an HWA geologist and/or geotechnical engineer. Representative soil samples were obtained from the explorations at selected intervals and taken to our laboratory in Bothell for further examination and testing. Field exploration methods described in detail and logs of explorations are presented in Appendix A. 2.2 LABORATORY TESTING Laboratory tests were conducted at HWA's laboratory in Bothell, Washington, on selected samples retrieved from the explorations to determine relevant index and engineering properties of the soils encountered at the site. The tests included visual classifications, natural moisture content determinations, grain size distribution analyses, determination of plasticity characteristics, consolidation analyses, shear strength properties, and organic content determination. The tests were conducted in general accordance with appropriate American Society of Testing and Materials (ASTM) standards. The test results and a discussion of laboratory test methodology are presented in Appendix B, and/or displayed on the exploration logs in Appendix A, as appropriate. 3. SITE CONDITIONS 3.1 SURFACE CONDITIONS The 3-Acre Park site is located northeast of the intersection of 36th Street and Eclipse Mill Road. This area was a former lumber mill (Eclipse Mill) operation. On termination of mill operations, the buildings were demolished and the land was rough graded. Currently, an old crane structure from this former mill site remains in place on the river bank. This site has been used for periodic temporary storage of miscellaneous construction debris, and stockpiles of concrete rubble occupied portions of this site at the time of our subsurface explorations. This concrete rubble Final Geotechnical Report-3-Acre Park.docx 2 HWA GeoSciences Inc.