The SR 99 Tunnel, Seattle Seawall & Waterfront Promenade

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Most Prominent Transportation Initiatives in Puget Sound

By William Hillis

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William Hillis

Broker & Research Editor, Realogics Sotheby's International Realty

"The viaduct's replacement now comprises a combination of mammoth earthworks and environmental enhancements that both compare and contrast with Seattle's historical public projects." 


Two catastrophic earthquakes sealed the fate of Seattle’s Alaskan Way Viaduct. The collapse of the similarly-designed I-880 in Oakland, California during the 1989 Loma Prieta quake spurred a move to retrofit the viaduct on Seattle’s essential north-south Route 99 corridor. But after the 2001 Nisqually earthquake, momentum for complete removal gathered steam. Since then, various other projects have been agglomerated onto the viaduct’s replacement, which now comprises a combination of mammoth earthworks and environmental enhancements that both compare and contrast with Seattle’s historical public projects.


The earthworks prominently include the 1.7-mile SR 99 tunnel under the Denny Regrade and Belltown areas, dug by what was briefly the largest tunnel-borer in history. This project is both by scope and location analogous to Seattle’s monumental reshaping of its landscape by the removal of Denny Hill, another of many such undertakings in the city’s history. The tunnel is scheduled to open to traffic in late 2018, after which the old viaduct will be demolished.

The tunnel is being partly financed by a projected $200 million in toll revenues. Tolls will be collected electronically based on the time of day, as on the SR 520 Bridge. An advisory committee recommended setting initial tolls at $1 all day, adding $1.25 (for a total of $2.25) during peak hours. They concluded that the planned off-peak toll of $1 would divert 38 percent of vehicles onto local streets, and recommended further study by the state Transportation Commission to resolve the diversion challenge.

Thereafter will come the reconstruction of the Seattle waterfront and the Elliot Bay Seawall, which are designed to correct Seattle’s less environmentally-sensitive legacy. The seawall project will replace the old wall’s 20,000 century-old timber pilings with a new structurally sound and seismically resilient seawall. The improvements, scheduled for completion by fall 2019, will add sea life habitat-enhancing features: cobbled surfaces and shelves along the face of the seawall; a cantilevered sidewalk; light-penetrating surfaces between the sidewalk and the roadway; and habitat benches below.

Concurrent improvements to the ferry terminal at Colman Dock will include a new passenger-only ferry facility on the south side, to be synchronously opened with the tunnel and before the viaduct is demolished in 2019. A new thoroughfare, Elliott Way, will rise along the route of the old viaduct, and the southernmost end of Alaskan Way will be replaced by an expanded Waterfront Park and a new city aquarium. By 2023, an extensive “Overlook Walk” will extend over the street-level traffic from an expanded Pike Place Market, featuring lawns, meadows and “bluffs” planted with quaking aspen.

Impact: The combination of projects replacing the Alaskan Way Viaduct and restoring Seattle's waterfront will improve the quality of life for downtown residents, raising property values in this already highly desirable area. The risk that the cumulative daily cost of tolls in the region will weigh heavily on lower income households is partly, but not fully, offset by Sound Transit bus and city bicycle-related improvements.