2320 RAILWAY AVE Geotech Report 2023-02-01

Interwest Construction Co.-Everett Contractor Yard Site Improvements, Everett, WA March 12,2021 Geotechnical Engineering Report P2184-T20 implementation of final site grading to facilitate the functionality of the proposed drainage plan. As currently proposed, runoff waters will be collected along the perimeter of the site and treated before ultimately being discharged to the new stormwater system along Railway Avenue, immediately west of the project area. The introduction of stormwater filtration vaults and a ' sediment collection and concrete stormwater wet pond are incorporated into the proposed drainage plan. Heavy duty pavements will be introduced along the perimeter and southcentral portions of the site and adjacent to the new truck scales. 2.0 EXPLORATORY METHODS We explored surface and subsurface conditions at the project site on September 17, 2020. Our ' exploration and evaluation program comprised the following elements: • Surface reconnaissance of the site; • Four test pit explorations (designated TP-1 through TP-4), advanced September 17, 2020; • A review of published geologic and seismologic maps and literature. Table 1 summarizes the approximate functional locations and termination depths of our subsurface explorations, and Figure 2 depicts their approximate relative locations. The following sections describe the procedures used for excavation of the test pits. TABLE 1 APPROXIMATE LOCATIONS AND DEPTHS OF EXPLORATIONS Termination Exploration Functional Location Depth (feet) TP-1 Southeast corner of the site,east end of proposed scale pits 13 TP-2 South-central portion of the site,west end of proposed scale pits 14 TP-3 North end of proposed sediment collection and concrete stormwater wet pond 13 TP-4 South end of proposed sediment collection and concrete stormwater wet pond 13 The specific numbers and locationsofour explorationsw r t p were selected in relation to the existing site features, under the constraints of surface access, underground utility conflicts, and budget considerations. It should be realized that the explorations performed and utilized for this evaluation reveal subsurface conditions only at discrete locations across the project site and that actual conditions in other areas could vary. Furthermore, the nature and extent of any such variations would not become evident until additional explorations are performed or until construction activities have ' begun. If significant variations are observed at that time,we may need to modifyour conclusions and recommendations contained in this report to reflect the actual site conditions. 2.1 Test Pit Procedures Our exploratory test pits were excavated with a steel-tracked excavator operated by Interwest personnel. An engineering geologist from our firm observed the test pit excavations,collected soil samples, and logged the subsurface conditions. Migizi Group, Inc. Page 2 of 16 roGIZI