The Miller Hull Partnership Proposes Turning a Defunct Seattle Tunnel Into a Landscaped Canyon
The tunnel's transformation is part of a wider proposal to create a new greenbelt for the city's downtown that would connect its parks and waterfront.
During the 20th century, it wasn’t uncommon for prominent architects to put forth bold visions for the future of cities. Frank Lloyd Wright presented his initial ideas for Broadacre City in 1932 and continued refining them until his death in 1959. During the postwar era, Buckminster Fuller proposed enclosing part of Manhattan under a geodesic dome, and Paul Rudolph famously proposed a Brutalist megastructure over the Lower Manhattan Expressway, still a glimmer in Robert Moses’s eye at that time.
Perhaps chastened by the reactions to such grandiose schemes, the architecture profession from the 1980s onward took a more conservative tack, generally preferring to pour its most ambitious efforts into corporate projects. At the same time, the automobile-oriented orthodoxy of postwar American urban planning began to be seriously questioned. Infrastructure that seemed visionary in the 1950s is now considered archaic and anti-urban.
In Seattle, the Alaskan Way Viaduct—built as part of a postwar expressway project that sliced the waterfront off from the rest of downtown in a manner that Robert Moses himself might have conjured up—is rapidly approaching the end of its life as a conduit for automobiles. The fate of one viaduct segment has been especially debated: The Battery Street Tunnel, which travels underneath six blocks of downtown Seattle.
While the Washington State Department of Transportation plans to fill the Battery Street Tunnel with rubble from the demolished viaduct, The Miller Hull Partnership has taken the lead in envisioning an alternative, innovative repurposing of the tunnel that would physically reconnect downtown Seattle with its waterfront and symbolically reunite the city with the stunning natural beauty of the Puget Sound region.
Miller Hull proposes removing the tunnel’s roof and creating an artificial canyon in the place of Battery Street that would connect Denny Park with Puget Sound. The bottom of the canyon, formerly the freeway road bed, would be excavated and converted into a creek with a salmon run. The creek’s shores would be lined with native vegetation (including towering Douglas-fir and western red cedar trees) and a variety of pathways and gathering spaces. The tunnel’s concrete ceiling beams would be removed and placed vertically into the ground, supporting a suspended pedestrian walkway through the new tree canopy.
The vision extends beyond Battery Street Tunnel: Miller Hull sees it as part of a larger push to create a continuous greenbelt around the downtown core. Existing natural amenities—Denny Park, the Lawrence Halprin–designed Freeway Park, and the in-progress James Corner Field Operations–planned waterfront—would be connected by pedestrianized streets such as the Battery Street Tunnel, University Street, and several avenues running north and south.
David Miller, the Miller Hull Partnership’s founding partner and professor of architecture at the University of Washington, explains that the project could be a game-changer for Seattle, putting the city on the map for urban design that’s rooted in the ecology of the larger bioregion. While pioneering projects like Miller Hull’s Bullitt Center may be familiar to architects and others in the design industry, a series of verdant artificial canyons in the heart of a major city’s downtown would catch the attention of the general public in much the same way the High Line, another piece of reimagined urban infrastructure, captured the imagination of New York.
The project’s biggest challenges aren’t technical, but political; it needs public leadership with the vision and determination to push it forward. A local advocacy group has formed to help that effort.
Miller was beginning his career in architecture while Buckminster Fuller and Paul Rudolph were proposing their own radical interventions in the urban environment. He says with a laugh, “My son is so sick of hearing me talking about the 1960s, but things like this remind me of those times. At the University, we’re trying to get students interested in thinking more about the city, being proponents of big ideas about the city, and about how to transform the city.”
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