3003 W CASINO RD BLDG 45-06 Geotech Report 2025-03-03

Geotechnical Engineering Report Proposed Flight Line Steam Line Project lierracon Boeing Everett Facility • Everett, Washington January 17, 2012 • Terracon Project No.: 81115085 111 4.2 Earthwork The following sections present recommendations for earthwork on the project. The recommendations presented in this report for design and construction of the utilidor are contingent upon following the recommendations outlined in this section. Earthwork on the project should be observed and evaluated by Terracon. Evaluation of earthwork should include observation and testing of engineered fill, subgrade preparation, foundation bearing soils, and other geotechnical conditions exposed during the construction of the project. ' 4.2.1 Site Preparation Preparation for construction should begin with procedures intended to control surface water runoff. It will be difficult to maintain temporary cuts, protect subgrade soils, and successfully utilize on-site soils as "engineered fill" if drainage is not controlled during construction. Concentrated runoff should not be allowed to enter excavations. Sand bags and asphalt berms are some methods that could be considered to divert surface water away from excavations given the paved nature of the surrounding area. 4.2.2 Excavation We expect that conventional trackhoes and excavators will be able to excavate the soils along the utilidor alignments. It may be necessary to rip dense to very dense glacial till soil in portions of the alignment to facilitate excavation. Cobbles and boulders may be encountered in the glacial till deposits due to the depositional environments associated with this soil type. The contractor should be prepared to deal with cobbles and boulders. 4.2.3 Temporary Slopes The stability of temporary cut slopes made during site work is a function of many factors, including, but not limited to, the following considerations: ■ the presence and abundance of groundwater; • the type and density of the various soil strata; I . the depth of the cut; • surcharge loadings adjacent to the excavations; and I . the length of time the excavation remains open. 1 Consequently, it is exceedingly difficult to establish a safe and maintenance-free cut slope angle in advance of construction. Cut slope stability should, therefore, be the responsibility of the contractor, since the contractor is continuously at the job site, able to observe the nature and condition of the subsurface materials encountered, monitor the cut performance, and control the scheduling of site activities. 111 I Responsive • Resourceful • Reliable 5