Wings Over Washington Pier 57 Development
Shoreline geotechnical services for a state-of-the-art flying theater.
Pier 57 is at the core of Seattle’s historic Puget Sound waterfront. It’s home to the Seattle Great Wheel, restaurants, tourist attractions, and now a state state-of-the-art flying theater that simulates the feeling of soaring with a bald eagle over the Washington State landscape. The multisensory experience is part of Miner’s Landing. It includes a 33-foot-tall screen and dynamically moving seats that give guests a realistic flying sensation. GeoEngineers provided geotechnical services for this unique and challenging shoreline development project, completed in 2016.
From the start, the project faced space and geologic data limitations. Pier 57 is only 140 feet wide and 470 feet long, leaving little room for staging and operations. Because of the pier’s importance to Seattle tourism, businesses also had to remain open to foot traffic during construction. Unfortunately, borings along the pier would have meant closing the pier and raising costs for the client significantly, so geotechnical investigation wasn’t possible.
The team also had to work around and with existing structures. The theater was designed to fit under the Miner’s Landing roofline and within the original roof trusses, and everything had to be supported by 100-year-old timber piles.
The theater and state-of-the-art equipment within meant a large and unique set of loads. In addition to large dead loads, like the 70,000 lbs. screen, Geoengineers had to plan for an unusual amount of dynamic loading on the foundation. The hydraulic seat system moves guests quickly in all directions during a show, and to maintain the illusion of flight the foundation needed to remain completely stationary during dynamic loads of approximately 18,000 lbs. Just an inch or two of movement would dampen the effect and ruin the flight simulation.
Building a complex project like this is challenging even under perfect conditions—but these conditions included a historic pier above 50 feet of water. To meet these challenges, the owners assembled a team that included GeoEngineers (Geotechnical Engineers), Jackson Main (Architect), Berger/ABAM (Structural Engineers), Manson Construction (Overwater Construction Contractor), W.G. Clark Construction (Building Construction Contractor), and Dynamic Attractions (Flying Theater Designers).
Planning, Design and Risk Management
Because of space limitations geotechnical borings were not possible for this project, so the GeoEngineers team had to get creative. Over the past century pile timbers have been replaced when necessary with lightly loaded 16-inch pipe piles. Fortunately, these replacements were treated as test piles during installation. By looking at several years of repair records the GeoEngineers team developed a relatively detailed understanding of subsurface geology beneath the pier—but making geotechnical recommendations without more rigorous subsurface data is still risky.
To further reduce risk, GeoEngineers recommended piles with a longer corrosion coating. This meant piles could be driven deeper, compensating for any slight variance between GeoEngineers’ subsurface predictions and real geologic contours. By working closely with the client, we were able to balance risk and project cost to find a solution that was acceptable to everyone.
To support the theater’s large and dynamic load, the team first considered batter piles for lateral stiffness. But teaming members pointed out space limitations that made this infeasible. GeoEngineers examined several possible approaches to the challenge of adding lateral stiffness without interfering with the existing pier and Miner’s Landing before finally deciding to connect the theater to the existing structure. The extra mass was enough to dampen the quick dynamic loads created by the hydraulic seat system.
Load Testing Piles
Several support beams from the existing pier had to be removed during theater construction. This, combined with increased live loads from larger crowds of guests, meant some piles were pushed past recommended working loads. These piles needed to be replaced, but this was a challenge thanks to their position near the center of the pier. GeoEngineers considered several standard approaches to this kind of pile replacement, but each would have added significant project costs.
Instead, the team took another look at the load capacity of the original timber piles. The documentation for this estimate consisted of nothing more than a note on the plans stating a design capacity of 20 tons. Based on previous work in the area, the GeoEngineers team thought this number seemed extremely conservative—but they had to prove it.
GeoEngineers incorporated pile load tests into the previously planned construction of stub piles with minimal changes to the construction schedule or budget. Data from the load tests confirmed that the piles could support the additional loads within acceptable deformation limits. Thanks to this approach, the team avoided the need for a large new steel beam system to transfer increased loads across several piles.
The completed Wings Over Washington is one of the most technically advanced theaters in the world, but few would guess that behind the 5K cameras and laser projection is another layer of technical wonders. Supporting such a large and dynamic structure on an aging wooden pier was no easy task, but GeoEngineers and project partners worked together to help this project soar.