3400 RIVERFRONT BLVD Geotech Report 2022-10-25

• • • • • Performed a laboratory testing program that consisted of the following laboratory tests: • • Fifteen moisture content determinations in general accordance with ASTM D 2216 ■ One consolidation test in general accordance with ASTM D 2435 • One density test in general accordance with ASTM D 7263 • • Three grain-size analyses in general accordance with ASTM C 117 and ASTM C 136 • • One particle-size analyses in general accordance with ASTM D 1140 • Maintained continuous logs of the borings, and collected soil samples at representative intervals. • • Provided recommendations for site development, including site preparation and grading, • subgrade preparation, demolition, excavations, temporary and permanent slopes, drainage, • retaining structures, shoring, fill placement criteria, suitability of on-site soil for fill, and recommendations for wet weather construction. • • Provided foundation support recommendations for the proposed buildings. Our • recommendations include allowable bearing pressure, lateral resistance parameters, and • settlement estimates. • • Provided an evaluation of groundwater conditions at the site, and provided general recommendations for dewatering during construction and subsurface drainage, if required. • • Provided retaining structure and pavement design recommendations. • • Provided seismic design recommendations in accordance with the procedures outlined in the • 2012 IBC. Provided estimates of liquefaction susceptibility, seismic settlement, and lateral . spreading. • Prepared this geotechnical engineering report that presents our findings, conclusions, and • recommendations. • 4.0 SITE CONDITIONS • 4.1 REGIONAL AND SITE GEOLOGY • The site is located in the Puget Lowland physiographic province of Washington, which consists of • a broad, low-lying region situated between the Cascade Range to the east and the Olympic • Mountains and Willapa Hills to the west. Starting in the early Pleistocene, the Puget Lowland province was subject to four periods of extensive glaciation. The region owes its present-day • geomorphic features to the last continental glacier that covered the region. The last ice sheet +1 retreated from the region approximately 10,000 years ago (Lasmanis, 1991). • The region is considered to be seismically active and more than 1,000 earthquakes are recorded • by seismographs each year. The epicenters for the last two major earthquakes were under • Olympia(1949) and Seattle-Tacoma(1965), with Richter magnitudes of 7.1 and 6.5, respectively. • These major earthquakes are attributed to the subduction of the oceanicJuan de Fuca plate • under the North American Plate (Lasmanis, 1991). Intraplate and shallow crustal source earthquakes can also affect the site. The closest mapped faults to the site are the Southern • Whidbey Island fault zone that is located approximately 6 miles southwest of the site (USGS, • 2015). • • According to geologic mapping, the surficial soil at the site consists of young alluvium that includes sand, gravel, silt, clay, and organic material (Holocene) (DNR, 2015). The adjacent • • • • G EO DESIGNS 3 Polygon-128-01:091615 •