With a dual mission to restore King Street Station to its 1906 grandeur while adding modern structural and sustainable upgrades, the project team behind this $55-million renovation and modernization project delivered a transportation hub to Seattle that respects the city's history and reflects its modern sensibilities.
A landmark on the National Register of Historic Places, the team restored the original character of the multimodal train station, including the rehabilitation of the iconic 12-story clock tower as well as the repair and restoration of the main waiting room. Work within the waiting room included restoration of the original 45-ft-high ornamental plaster ceilings and halls, the terrazzo floors inlaid with mosaic tile and the historic operable windows.
In addition to the historic elements, the Seattle-based team, led by architectural firm ZGF Architects and general contractor Sellen Construction, installed seismic upgrades and met LEED-Platinum standards. "We took this historic structure and made it an outstanding sustainable building," says Tim Williams, associate partner and King Street Station project architect at ZGF. "A city that touts itself as being green now has a portal into the city that's a leader in sustainability."
As part of its green strategy, the team installed a geothermal well field and heat pumps, making it one of the first projects in downtown Seattle to do so. The geothermal system also allowed for a reduction in the size of the building's heating and cooling system. The wells allow the building to perform 40% above ASHRAE baseline.
While installing new utilities and the geothermal wells during the first phase of the project, the team came across granite boulders from an adjacent building's old foundation. The foundation granite was a perfect match for the exterior granite originally used in the walls, much of which was removed during previous modernizations. Utilizing the same means and methods used to create the original granite blocks 100 years ago, the reclaimed granite boulders were cut and fabricated into new wall panels for the exterior finishes.
In addition to restoring the building's windows, the team took the opportunity to incorporate them into its sustainability strategy. All of the sashes and trims from the original 1906 windows were removed, refinished and reinstalled using the remaining original glass. The team restored 74 window openings and 199 sashes and replicated 15 window openings and 33 sashes.
The original design included moveable windows that could be opened and closed with hand cranks. The team added motors to this existing system and tied them into the building's control system. To accomplish this, the team had to meet Buy America provisions because the project was funded in part with federal stimulus funds and TIGER grants. The only available actuator motors specified for moveable windows are manufactured in Germany. Following some investigations, the team devised and tested the use of fire damper motors as an alternative. The plan worked and shaved money from the budget.
"These are $100 motors that are a fraction of the cost of the German option," Williams says. "Plus, they are readily available in the U.S. if you need to replace one."
Other sustainable design strategies included use of photovoltaic panels—which were hidden from view to preserve the building's historic look—and energy-efficient lights and water fixtures.
Originally constructed as a steel-framed unreinforced masonry structure, the seismic retrofit required constructing a new steel structure inside the old one and anchoring the existing masonry to the new structure.
Using performance-based building design, the team analyzed seismic upgrades to ensure the new structural steel fit behind existing ornamental plaster sections.
In order to keep all of the historic elements in the main waiting room in their historical plane, 35-ft high slots were cut within the building's brick perimeter and steel was inserted and high-strength grouted to create the seismic reinforcing. Strategically designing the steel allowed the team to increase structural capacity of the building while maintaining the historic fabric and meeting historic preservation guidelines.
As part of its approach, the team planned to install 50-ft screw piles within isolated areas. Due to access and headroom limitations, the team was challenged to find and design a piece of equipment for pile installation. The team modeled and designed solutions that used hydraulic heads attached to small machinery that could fit in confined spaces. This allowed the facility to continue operations and avoid damage to the historic elements during the drilling of the helical piles.
In total, the team placed more than 1,400 tons of steel among the historic elements, requiring meticulous attention to detail, extreme quality-control measures and innovative design for steel bracing and drilling of the helical pile foundation to minimize impacts to the historic fabric.
"What is remarkable about this project is the amount of complexity and challenge that is invisible to the public," says Mike Morris, senior project manager and senior vice president at Sellen Construction. "We placed 1,400 tons of steel and significant structural elements with the goal that no one would see the work we did."
While structural work was under way, extensive efforts were required to protect the existing historic fabric, which included the original windows, doors, marble, ornamental plaster, terrazzo floors, mosaic tiles, brass elements, granite, terra-cotta and copper canopy fascia. The team cataloged, removed, stored and later reinstalled many historic elements in their exact location.
Among the most visible and striking aspects of the historic renovation were the restoration and re-creation of the ornamental plaster. Using the building's original ornate pieces and the methods originally employed, craftsmen created matching molds to cast new—and repair original—sections of the ornamental plaster. Using a first generation mold, the mold was filled with casting plaster and inlaid with hemp and burlap during the casting process to crease the final piece. The casting was then stripped out of the mold, reinstalled and attached to the structure.
All work was carried out in a building that serves more than 4 million passengers annually. To accommodate the operational requirements of the station, the team divided the project scope into three phases. The site was also separated into 20 different work areas and 90 individual steel zones to complete structural upgrades. In a facility that welcomes up to 10,000 people per day, the project had no OSHA recordable incidents.
"Undertaking numerous unique project challenges including the need for a seamless seismic upgrade, significant sustainable design goals, program reconfigurations within a constricted footprint, meeting contemporary building requirements all within a treasured landmark historic building, the design team succeeded in developing solutions that have been widely embraced and exceeded expectations all while allowing project priorities to be achieved," says Trevina Wang, King Street Station program manager with the Seattle Dept. of Transportation.