8417 EVERGREEN WAY Geotech Report 2022-10-25

Geotechnical Engineering Report-Revised lrerracon Proposed CFT Retail • Everett,Washington February 1, 2018 ■Terracon Project No. 81185002 If the risk of unforeseen conditions and possible unsuitable or compressible fill is deemed too great by the owner, several options exist for reducing or eliminating the risk. Removal of the existing fill and replacement with structural fill is a typical measure for mitigating adverse effects of unsuitable fill soil. For purposes of this report, we assume complete removal of the upper 1 to 7 feet of fill. Because the fill coverage is variable throughout the site, we recommend removal of unsuitable material be performed under the observation of a Terracon field engineer. The lateral extent of existing fill removal beyond the building pad should be at least two-thirds of the depth of excavation at the perimeter footing location. 4.2 Earthwork The following text presents recommendations for site preparation, excavation, subgrade improvements, and placement of structural fills for the project. The recommendations presented for design and construction of earth-supported elements, including foundations, slabs, and pavements, are contingent upon following the recommendations outlined in this section. Earthwork on the project should be observed and evaluated by Terracon. The evaluation of earthwork should include observation and testing of structural fill, subgrade preparation, foundation bearing soil, and other geotechnical conditions exposed during the construction of the project. 4.2.1 Site Preparation We anticipate construction will be initiated by demolition and removal of existing buildings, sidewalks, asphalt, fencing, and landscaped areas. All vegetation, organic debris, and elements of existing structures, including footings, stemwalls, and floor slabs, should be removed completely from the site. Excavations associated with removing existing site elements should be backfilled with structural fill placed and compacted in accordance with the recommendations presented in this report. Existing underground utilities, such as storm sewer, sanitary sewer pipe, fuel lines, grease traps, and water line, that will not be used as part of the new development should either be removed completely or filled with Controlled-Density Fill (CDF) conforming to WSDOT section 2-09.3(1)E, Backfilling. In the event that existing utilities are abandoned in place, we recommend density testing of the trench backfill in order to verify that it is compacted to the density recommendations provided herein. The silty sand soil encountered in the borings will be sensitive to disturbance from construction activity and increased moisture. If precipitation occurs prior to or during construction, the near- surface soil could increase in moisture content and become more susceptible to disturbance. Construction activity should be monitored, and should be curtailed if the construction activity is Responsive ■ Resourceful ■ Reliable 5