2320 106TH ST SW Geotech Report 2022-10-25

Geotechnical Report Proposed Storage Building 106th Street SW and Airport Road Everett, Washington 1.0 PROJECT DESCRIPTION The project consists of developing the site with an approximately 45,000 square-foot storage building, a stormwater detention vault, retaining wall, and associated paved access,parking, and utility improvements. Based on a preliminary grading, paving, and storm drainage plan prepared by Barghausen Consulting Engineers, dated June 23, 2015 the building will have a finish floor elevation of 554.0 feet. Grading to achieve the finish floor elevation and surrounding pavement elevations will involve cuts and fills from one to eight feet. The vertical grade transition on the west side of the site will be supported by a retaining wall. The plans indicate that stormwater runoff collected from the planned development area will be routed to a below- grade stormwater detention vault located in the southern portion of the site. The plan shows the stormwater vault is dimensioned at approximately 60 feet by 156 feet with the bottom of the vault at elevation 540.5. Excavation on the order of 9 to 19 feet will be required to reach the vault foundation elevation. We expect the structure will be constructed using perimeter precast concrete tilt-up wall panels with interior isolated columns spaced at 40-to 50-foot centers supporting a steel or wood truss roof system. Floor slabs will be =nstructed at grade. Structural loading is expected to be light to moderate, with isolated columns carrying loads =50 to 80 kips,and bearing walls carrying 4 to 8 kips per foot. The recommendations in the following sections of this report are based on our understanding of the preceding design features. We should review design drawings as they become available to verify that our recommendations have been properly interpreted and to supplement them, if required. 2.0 SCOPE OF WORK Our scope of work was completed in accordance with our authorized proposal, dated October 5, 2015. On October 13, 2015, we visited to the site to confirm the surface conditions are similar to when we first conducted our subsurface exploration. Based on our visual observations, the existing surface site conditions are similar to the conditions at the site when we conducted our subsurface exploration. Therefore, it is our opinion,that the soil conditions observed in 2007 are likely the same today. On August 21, 2007, we excavated 5 test pits to depths of 9 to 15 feet below existing surface grades. Using the information obtained from our subsurface exploration, we preformed analyses to develop geotechnical recommendations for project design and construction. Specifically, this report addresses the following: • Soil and groundwater conditions • Seismic considerations • Site preparation and grading • Excavation and shoring