Appendix J 95% Geotechnical Engineering Design Study - Port Of Seattle

2 Terminal 5 Deepening and Crane Rail Upgrade B. Appendix C presents relevant exploration logs from earlier geotechnical studies at the site. Appendix D includes results of our slope stability analyses. PURPOSE, SCOPE, AND USE OF THIS REPORT The purpose of our work is to provide the Port of Seattle with subsurface information and interpretation and geotechnical engineering design recommendations. Our work supports the Port’s design and cost estimate for deepening the berth and upgrading the crane rail at Terminal 5. Our scope of work for this project included: Assessing subsurface conditions using explorations, laboratory tests, and historical geotechnical reports and explorations; Performing geotechnical design and analysis; Providing geotechnical engineering recommendations; and Producing a geotechnical engineering design report. This report addresses each of our scope items. We prepared this report for the exclusive use of the Port of Seattle, Moffatt & Nichol Engineers, and their design and construction consultants for specific application to the Terminal 5 Dock Upgrade Project and site location. Within the limitations of scope, schedule, and budget, we completed the work according to generally accepted geotechnical practices in the same or similar localities, related to the nature of the work accomplished, at the time the services were accomplished. We make no warranty, expressed or implied. PROJECT UNDERSTANDING The project site is located along the west shore of the West Waterway at the mouth of the Duwamish River at the Port of Seattle (Figure 1). 19094‐01 June 14, 2016

Terminal 5 Deepening and Crane Rail Upgrade 3 Figure 1. Vicinity Map The site is occupied by a pile‐supported wharf structure and a paved shipping container storage area constructed and improved over many decades. The paved upland area of the site is generally level, with a surface elevation of approximately 20 feet MLLW. (Unless stated otherwise, elevations in this study correspond to the vertical datum MLLW.) The ground under the wharf slopes down from the upland area to the bottom of the waterway at approximately elevation 40 feet. This under‐pier slope is inclined at approximately 1.5 to 1.75 horizontal to 1 vertical. The southern end of the project area has already been deepened from 40 to 45 feet with closely spaced H‐piles supporting the cut. The middle of the site has already been deepened from 40 to 50 feet with a cantilevered AZ‐48 sheet pile toe wall. The northern end of the site has not been deepened and was designed to 50 feet at the toe of the slope with timber pinch piles already installed along the slope. The Port of Seattle is updating Terminal 5 to service container ships as large as the Maersk EEE that entered service in July 2013, which has a capacity of 18,000 twenty‐foot‐equivalent units (TEU). To support this type of vessel the Port wants to deepen up to 2,900 linear feet of Terminal 5 to design 19094‐01 June 14, 2016

4 Terminal 5 Deepening and Crane Rail Upgrade elevation 55 feet (including 1 foot of maintenance dredge and 2 feet of overdredge results in a new toe of slope up to 58 feet). In addition, larger and heavier cranes are required, which will produce crane loads of approximately 85 kips per foot on each rail. Our study limits extend from Station 2 00 to 29 00 (Bent 25s to 114). To facilitate additional berth deepening, a new, stronger, king‐pile toe wall will be required with supplemental structural reinforcement (pinch piles) required along some or all of the stations. SUBSURFACE CONDITIONS Our understanding of the subsurface conditions at Terminal 5 is based on numerous existing soil explorations, the materials encountered in 12 new mud rotary borings, laboratory testing of soil samples, shear wave testing (Attachment 2), and our experience in the area. Figure 2 shows the location of the existing and new soil explorations. Figures 3a and 3b illustrate the interpreted subsurface conditions along the wharf. Details of the conditions observed at the new boring locations are shown on the logs included in Appendix A and should be referred to for specific information. Subsurface soil conditions are based on explorations accomplished at discrete locations at the site. Soil properties inferred from the field and laboratory tests formed the basis for developing our geotechnical recommendations contained in this report. The nature and extent of variations between the explorations may not become evident until construction. If variations appear, it may be necessary to reevaluate the recommendations in this report. Soil Conditions The soil conditions can be generalized as follows: A surficial veneer of riprap of varying size and depth was on the under‐pier slopes. A layer of asphalt over gravel and sand fill was encountered in the upland areas. Very loose to dense Sand to very silty Sand with layers of Silt and Clay was observed throughout the site. For our analyses this is referred to as engineering soil unit (ESU) 1. Very soft Silt and Clay layers were observed, typically located just above the bearing layer. This layer is referred to as ESU 2. Very dense glacially overridden soils were observed at depth in the new and the historical explorations. This bearing layer is at elevation 120 to 90 feet at the south end of Terminal 5 and gradually deepens to elevation 135 feet in the borings at the north end of the terminal. Our most southern upland boring (HC‐5) encountered this layer at approximately elevation –90 feet. Very dense till and till‐like materials are referred to as ESU 3, while glacially overridden silts and clays are labeled ESU 4. 19094‐01 June 14, 2016

Terminal 5 Deepening and Crane Rail Upgrade 5 Groundwater Groundwater at the site is influenced by tidal fluctuations in Elliott Bay. We did not observe the groundwater table in the upland soil borings because of the drilling method that was used. Tidal influence is typically limited to a short distance behind the top of the slope. Typical groundwater levels in the backland throughout Terminal 5 are at around elevation 9 to 10 feet. SEISMIC CONSIDERATIONS The site is in a seismically active area. In this section, we describe the seismic setting at the project site, identify the seismic basis of design, provide our recommended preliminary design response spectra, and discuss the seismic hazards at the site. Seismic Setting The seismicity of Western Washington is dominated by the Cascadia Subduction Zone, in which the offshore Juan de Fuca Plate is subducting beneath the continental North American Plate (Figure 4). Three types of earthquakes are associated with subduction zones: intraslab subduction, interface subduction, and crustal earthquakes. 19094‐01 June 14, 2016

6 Terminal 5 Deepening and Crane Rail Upgrade Figure 4. Cascadia Subduction Zone Earthquake Sources Subduction Zone Sources. The offshore Juan de Fuca Plate is subducting below the North American Plate. This causes two distinct types of events. Large‐magnitude interface earthquakes occur at shallow depths near the Washington coast at the interface between the two plates (e.g., the 1700 earthquake, which had a magnitude of approximately 9). A deeper zone of seismicity is associated with bending of the Juan de Fuca Plate below the Puget Sound Region that produces intraslab earthquakes at depths of 40 to 70 kilometers (e.g., the 1949, 1965, and 2001 earthquakes). Figure 4 depicts the Cascadia Subduction Zone and the various types of earthquakes it can produce. Crustal Sources. Recent fault trenching and seismic records in the Puget Sound area indicate a distinct shallow zone of crustal seismicity, the Seattle Fault, which may have surficial expressions and can extend 25 to 30 kilometers deep. The project site is within the Seattle Fault Zone, with the northern splay of the Seattle Fault mapped through the southern end of Terminal 5 (Figure 5). 19094‐01 June 14, 2016

Terminal 5 Deepening and Crane Rail Upgrade 7 Figure 5. Site Proximity to the Seattle Fault Zone Seismic Basis of Design We developed design response spectra at the ground surface using code‐based methods. We have referred to ASCE 61‐14 Seismic Design of Piers and Wharves for this design as appropriate. The seismic basis of design for this project is different than for a new construction project. The Port of Seattle and City of Seattle have entered into an agreement of understanding that states that the Port may redevelop existing facilities to current codes for static conditions, but the agreement requires not making the seismic hazard worse than it was before the improvements. Therefore, we evaluated the seismic hazard at the typical hazard levels, with our seismic analyses primarily comparative rather than absolute. We considered four seismic hazard levels in our analysis (OLE, CLE, DE, and MCE, defined below). The basis of design for the 2012 International Building Code (IBC) is two‐thirds of the hazard associated with the Risk‐Targeted Maximum Considered Earthquake (MCER). The IBC event is referred to as the Design Event (DE). The ASCE Piers and Wharves standard requires the consideration of two additional seismic events: the Operating Level Event (OLE) and the Contingency Level Event (CLE). The OLE has a 19094‐01 June 14, 2016

8 Terminal 5 Deepening and Crane Rail Upgrade 50 percent probability of exceedance in 50 years, which corresponds with a return period of 72 years. The CLE has a 10 percent probability of exceedance in 50 years, which corresponds with a return period of 475 years. Slope performance was evaluated for the OLE, CLE, and DE. Liquefaction hazard was evaluated for the OLE, CLE, DE, and Maximum Considered Earthquake (MCE). The MCE has a 2 percent probability of exceedance in 50 years, which corresponds with a return period of 2,475 years. Design Response Spectra and PGA We determined the site class in accordance with 2012 IBC based on Standard Penetration Test (SPT) data collected from our explorations at the project site. The site contains liquefiable soil corresponding to a classification of Site Class F. The code requires a site‐specific analysis for Site Class F, if the period of the structure is greater than 0.5 seconds. Because this structure will have a period greater than 0.5 seconds, we typically recommend that a site‐specific analysis be performed as part of final design. As the seismic structural design for this project is comparison‐based, and we understand a site‐response analysis is not needed, the project team decided a site‐specific response analysis was unnecessary. For miscellaneous design, and for buildings with a period less than 0.5 seconds, we used the site class definition without considering liquefaction‐susceptibility, which corresponds to Site Class E. We obtained the seismic hazard parameters from the United States Geologic Survey 2008 National Seismic Hazard Maps (USGS 2008) for the site location at latitude 47.577 and longitude 122.362. Code‐based design response spectra and seismic design parameters for the MCER, DE, OLE, and CLE are provided on Figure 6. The recommended peak ground acceleration (PGA) values for the MCER, OLE, and the CLE hazards are also shown on the bottom left of Figure 6. Table 1 includes spectral accelerations at periods of 0.2 and 1 seconds (Ss and S1 respectively) for all three hazard levels. These spectral accelerations, along with the site classification, may be used to develop a code‐based response spectrum. Table 1 – Ss and S1 Values for MCER, OLE, and CLE Hazard Level Rock Ss in g Rock S1 in g OLE 0.239 0.070 CLE 0.691 0.228 MCER 1.456 0.564 Liquefaction Potential Liquefaction is a phenomenon caused by a rapid increase in pore water pressure that reduces the effective stress between soil particles, resulting in the sudden loss of shear strength in the soil. Granular soils that rely on interparticle friction for strength are susceptible to liquefaction until the excess pore pressures can dissipate. Sand boils and flows observed at the ground surface after an earthquake are the result of excess pore pressures dissipating upward, carrying soil particles with the draining water. In general, loose, saturated sandy soils with low silt and clay contents are the most susceptible to liquefaction. Silty soils with low plasticity are moderately susceptible to liquefaction under relatively higher levels of ground shaking. For any soil type, the soil must be saturated for liquefaction to occur. 19094‐01 June 14, 2016

Terminal 5 Deepening and Crane Rail Upgrade 9 We used empirical methods to estimate liquefaction potential based on the standard penetration test (SPT) data obtained at the site. Procedures after Idriss and Boulanger (2008) were used for the SPT data. For the OLE and MCE hazard levels we used earthquake magnitudes of 6.53 and 6.8 and peak ground surface horizontal acceleration (PGA) of 0.26 and 0.545 g in our analysis, respectively. According to our analysis, the site is very susceptible to liquefaction in soil units below the water table down to glacial soils. The potential for liquefaction in the alluvial soils is relatively consistent across the site. The results of our analyses are presented on Figures 7 through 18 for each of our new borings. Occasional interbedded layers of non‐liquefiable soil may be present throughout the profile; however, the vast majority of submerged soils within 80 feet of the ground surface are susceptible to liquefaction in the MCE event. Site‐specific dynamic laboratory testing resistance to liquefaction have been completed. Results of these tests are included in Appendix B. Sandy soils tests likely had the liquefaction resistance reduced during the process of sampling. When completed on sandy soils, the tests were generally completed to verify that they did not have a higher liquefaction resistance than empirical methods estimated. Post-Liquefaction Vertical Settlement Post‐liquefaction settlement results from densification and redistribution of liquefiable soils following an earthquake. The ground surface settlement is not typically uniform across the area, and can result in significant differential settlement. We estimated liquefaction‐induced ground surface settlement using the Idriss and Boulanger (2008) method based on SPT data. The results of our analysis indicate that liquefaction‐induced settlement will be slightly greater at the south end of the terminal in upland crane rail areas. MCE settlement is predicted to range up to 38 inches and 49 inches at the north and south ends of the terminal, respectively. Assuming a stable slope, the pile‐supported crane rail structure is not expected to settle more than a couple of inches. Although, many of the wharf piles could see more settlement because they do not all extend to the bearing layer. This could lead to significant differential settlement within the wharf structure and between the structure and surrounding ground surface. Ground Motions We selected and scaled a single ground motion for two hazard levels for input to our finite element analysis using PLAXIS. We used response spectra based on the deaggregated hazard from the USGS (2008) probabilistic seismic hazard analysis for the 72‐year and 2,475‐year return periods with a corresponding shear wave velocity of 2,500 feet per second. These response spectra correspond to the OLE and the MCE hazards, respectively. The MCE hazard was then scaled by two‐thirds to obtain the design‐level event. We selected and scaled multiple ground motions to obtain a single motion that was a close match to the target response spectra. For the OLE and MCE hazards, we selected intraslab subduction record and a crustal record, respectively. These earthquake mechanisms were chosen based on the deaggregated data from USGS. The data show that approximately 50 percent of OLE hazard corresponds with an intraplate subduction event and that nearly 50 percent of the MCE hazard corresponds with a Seattle Fault type 19094‐01 June 14, 2016

10 Terminal 5 Deepening and Crane Rail Upgrade of event (crustal fault). The OLE was chosen out of a suite of 30 intraslab ground motions and the MCE from a suite of over 100 crustal motions. These suites of motions are part of a Hart Crowser database. The selection was based on the smallest least squares error in combination with a modest scaling factor. For the OLE hazard, we chose a ground motion from the 1965 Puget Sound earthquake, and for the design level earthquake (2/3 MCE) we selected one from the 1999 Chi‐Chi earthquake. The target and ground motion response spectra for the selected ground motions are presented on Figure 19. The spectral accelerations in this figure are lower than the code‐based spectra on Figure 6 for equivalent hazard levels. This is because the Figure 6 spectra are developed to represent soil conditions at the base of the PLAXIS model, which is equivalent to the Site Class B/C boundary. Fault Surface Rupture As mentioned previously, the southern end of Terminal 5 is within the northern portion of the Seattle Fault Zone (Figure 5). Therefore, there is potential for surface rupture at the site in the case of a Seattle Fault event. Even if there is not surface rupture due to the deep, loose‐to‐soft soil, it is possible for significant differential movement of piles embedded in the dense bearing layer. Design for this type of rupture is cost‐prohibitive and difficult due to uncertainty about where fault rupture could occur. Fortunately, because of the relatively long return periods of the Seattle Fault, the uncertainty about where fault rupture could occur within the Seattle Fault Zone, and the low potential for fault surface rupture during the design life of the structure, the overall hazard associated with fault surface rupture is low. Tsunami Hazard The tsunami hazard within Puget Sound is controlled by crustal faults. According to the Elliott Bay Area Tsunami Hazard Map prepared by the Washington State Department of Natural Resources (2003), a tsunami originating from a Seattle Fault earthquake is predicted to cause widespread inundation ranging from 0.5 to 2 meters deep across the project site. In addition, inundation could be 2 to 5 meters in localized areas. The Tsunami Hazard Map is included as Attachment 1. Because of the relatively long return period of the Seattle Fault, the tsunami hazard during the design life of the structure is also low, but is larger than the potential for fault surface rupture. GEOTECHNICAL ENGINEERING CONCLUSIONS AND RECOMMENDATIONS This section of the report presents our conclusions and recommendations for the geotechnical aspects of design and construction on the project site. We have developed our recommendations based on our current understanding of the project and the subsurface conditions encountered by our explorations. If the nature or location of the development is different than we have assumed, we should be notified so we can change or confirm our recommendations. 19094‐01 June 14, 2016

Terminal 5 Deepening and Crane Rail Upgrade 11 Slope Stability The focus of the geotechnical engineering assessment of the berth deepening to elevation 58 feet was two‐fold: (1) to assess the static condition to determine if the project meets the local standard of practice for slope stability, and (2) to assess the seismic condition

Lateral Earth Pressures for King‐Pile Toe Wall Design 17 Vertical Pile Capacity 18 Landside Crane Rail: Steel Pipe Piles 20 Waterside Crane Rail: Concrete Piles 20 Lateral Pile Fixity 20 Upland Crane Rail Piles Near Outfalls 21 Light Pole Foundation 21 Substation Design Recommendations 21