3003 W CASINO RD BLDG 40-23 Geotech Report 2025-01-22

This report presents the results of our geotechnical engineering services in support of the proposed 777X Horizontal Build Line (HBL) Expansion project located within the 40-23 Building in the Boeing Everett Factory. Our project understanding is based on discussions with Sebastien Doucet and Brian Sayre with BRPH Architects Engineers, Inc. (BRPH), several site walks with the design team, existing as -built and proposed plans, design scope of work information provided by Boeing and BRPH, and our previous experience within the Boeing Everett Factory. The project site is shown relative to surrounding physical features on the Vicinity Map, Figure 1. Based on our project understanding, foundation improvements will generally include: Construction of new concrete foundations for HBL Positions 5 through 7 located south of existing HBL Positions 1 through 4. Design will consist of the removal of the existing segmented concrete flooring and replaced by a single contiguous concrete mat foundation. Each position will extend approximately 100 feet north -south by 158 feet east -west. The position layout is shown in the Site Plan, Figure 2. is Addition of two concrete foundation pads for HBL Position 4 to accommodate reverse robot bed extensions. The concrete foundation pads will be added to the east of existing foundation. Each concrete foundation pad will be approximately 10 feet by 12 feet. Construction of a new tooling scaffolding connector bridge between HBL Positions 4 and 5. The connector bridge will be constructed on the west end of HBL Positions 4 and 5. We understand that Boeing is currently considering two options for the connector bridge. The first option will have a 25-foot shift between HBL Positions 4 and 5. This option will require a new concrete foundation pad to meet seismic requirements. The second option will have no shift between HBL Positions 4 and 5. This option will require the new concrete foundation for HBL Position 5 be installed against the existing concrete foundation for HBL Position 4. Other improvements include the reroute of existing trenches and the addition of new utilities. The purpose of our services is to review existing subsurface information within the immediate area, to complete additional geotechnical borings to fill data gaps, and to complete laboratory testing and engineering analyses as a basis for providing geotechnical design recommendations for the proposed foundation improvements. We were also requested to complete numerical modeling analyses of the subgrade condition for the mat foundation. Our services were completed in general accordance with our scope and fee estimate dated April 18, 2022 and Purchase Order executed on May 2, 2022. 2.0 FIELD EXPLORATIONS AND LABORATORY TESTING The subsurface conditions at the site were evaluated by completing six hollow -stem auger borings (B-6 through B-11) to depths ranging from about 30 to 3014 feet below the existing slab elevation. The approximate locations of the explorations are shown in Figure 2. Descriptions of the field exploration program and the boring logs are presented in Appendix A. GEoENGINEERs June 1, 2 22 'age I Re Na. 0120-29a. 02