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Proposed replacement of the Alaskan Way Viaduct: Wikis


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The Alaskan Way Viaduct was damaged in the 2001 Nisqually earthquake but remains open to traffic.

The Alaskan Way Viaduct is a viaduct bridge in the city of Seattle, Washington, that carries Washington State Route 99 over the Elliott Bay waterfront between the city's Industrial District and Belltown. Originally opened in 1953, the structure was damaged in the 2001 Nisqually earthquake and has been proposed to be replaced by an underground tunnel.

Since 2001, the proposed replacement has been the source of much political consternation. Options for the structure – which carries 110,000 vehicles per day – have included replacing the viaduct with either a cut-and-cover or deep-bore tunnel, another elevated highway, or a surface highway; retrofitting the existing structure to improve its capability to withstand earthquakes; or outright eliminating the viaduct and making traffic-flow improvements to other north-south arterials to compensate.


Tunnel selection

On January 12, 2009, the state of Washington, King County, the city of Seattle, and the Port of Seattle revealed that they had agreed to replace the viaduct with a four-lane, 2-mile (3.2 km) long bored underground tunnel.[1] The tunnel would have a south portal in SoDo, near Qwest Field, and a north portal in South Lake Union.[2] On March 4, 2009, the state senate passed a bill endorsing the tunnel option.[3]

The project is estimated to cost US$4.25 billion, with $2.8 billion coming from the state and federal governments to cover the tunnel boring and a new interchange in SoDo.[2] The replacement project also includes the following projects and funding sources:

  • The city of Seattle will fund surface street improvements, utility relocation, and repairs to the Alaskan Way Seawall, which was also damaged in the Nisqually earthquake.[2]
  • Since the proposed tunnel will contain two lanes in each direction as opposed to the viaduct's three, and no Western Avenue exit to serve the Belltown, Interbay, and Ballard areas, King County will fund transit improvements to offset the loss.[2]
  • The Port of Seattle is considering funding part of the project in SoDo.[2]
  • The state senate's bill calls for a study regarding $400 million being collected through tolls.

The announcement did little to quell the heated debate over the viaduct's replacement, with several factions expressing their criticism over the tunnel decision.[1][2] Construction is proposed to begin in 2011, with the proposed tunnel opening in 2015 [2] Some of the criticisms include:

  • Restrictions on flammable and hazardous cargo through tunnels would restrict movement of freight through downtown.[2]
  • Lack of a Western Avenue exit would place an additional traffic burden on surface streets in the Queen Anne area.[2]

Earthquake concerns over existing structure

The 1989 Loma Prieta earthquake destroyed the similarly designed Cypress Street Viaduct in Oakland, California with considerable loss of life. The 2001 Nisqually earthquake damaged the viaduct and its supporting Alaskan Way Seawall and required the Washington State Department of Transportation (WSDOT) to invest US$14.5 million in emergency repairs. Experts give a 1-in-20 chance that the viaduct could be shut down by an earthquake within the next decade.[4] Since the Nisqually Earthquake occurred, the viaduct has been closed semi-annually for WSDOT to conduct inspections of the structure. Those inspections have discovered continuing settlement damage.

The Alaskan Way Viaduct seen from Elliott Bay
The view beneath the viaduct, facing south

Due to damage from continuing settlement, a group of researchers and faculty from the University of Washington urged the mayor of Seattle (in 2007) to close the viaduct within a four-year timeframe.[5]

Past proposals

Governor Christine Gregoire stated "no action" is not an option for the viaduct.[6] However, she dismisses the idea of building a tunnel, and has not proposed any other plans or move towards repairs. There is consensus that some action needs to be taken with the viaduct and the seawall that supports the viaduct in the near future.[7] However, there is no consensus on whether to remove, replace, or rebuild the viaduct.

Many Seattle leaders, including Mayor Greg Nickels and state and city transportation officials, favor building a tunnel. Plans for a six-lane, "cut-and-cover" double-decker tunnel were developed.[8 ] The tunnel was envisioned as a solution to not only the viaduct's traffic limitations and safety problems, but also to allow better uses for the waterfront real estate, including parks, housing, and retail developments. While future development of the Alaskan Way real estate corridor may provide tax revenue for the city, many state lawmakers claimed the originally proposed six-lane tunnel project was too costly. In response to concerns about the cost of the originally proposed tunnel construction, the city council created a scaled-down four-lane hybrid tunnel option.

On September 7, 2004, WSDOT announced that the alternatives had been narrowed down to two:

  1. Rebuilding the viaduct (estimated cost, $3.2 to $3.5 billion; estimated time, 6–8 years)
  2. Replacing the viaduct with a six-lane tunnel (estimated cost, $3.6 to $4.1 billion; estimated time, 7–9 years)

However, due to the costs and scope of the project, other options were still being discussed in the local media. Seattle City Council member Peter Steinbrueck noted that "While the mayor's first choice is the tunnel, he supports the City Council's resolution that designates a surface and transit alternative as a backup."[9]

In mid-December 2006, Governor Gregoire stated the decision was at a stalemate and called for an advisory ballot on March 13 for Seattle residents.

Tunnel option

  • Tunnel would be four lanes: two lanes each direction, in a stacked formation.
  • The tunnel’s 14-foot (4.3 m) shoulders would be used as an extra travel lane each way during periods of high demand.
  • Transit service would be increased during peak commuter periods.
  • Cars entering and exiting from Elliott and Western Avenues would each have a dedicated lane.
  • Third Avenue would become a permanent transit corridor.
  • Cost estimate for the four-lane tunnel: $3.4 billion[8 ]

On February 13, 2007, Governor Christine Gregoire rejected the scaled-down four-lane tunnel hybrid option, saying that the recent WSDOT review showed the tunnel proposal "does not meet state and federal safety standards." Of particular concern is that the use of shoulders as traffic lanes during peak traffic times would leave no additional lanes for emergency access.[10] However, several of the viaduct "stakeholders committee" brought on board to advise the city have since indicated that the tunnel option should remain on the table.[11]

Elevated structure

  • Replace current viaduct with updated seismic standards.
  • The new viaduct would be on average 71 percent larger than the current viaduct. The size increase would put more of the waterfront in shadow.[12]
  • Lanes on new structure would be 12 feet (3.7 m) wide, with new shoulders on each side for a total width of 75 feet (23 m) across. The current structure has no shoulders and lanes are less than 10 feet (3.0 m) wide in some areas.
  • Current on and off ramps at the northern and southern portion of the viaduct in Seattle would remain the same with an additional full intersection at South Atlantic Street and South Royal Brougham Way. The First Street off ramp would be removed.
  • Plan would include a complete replacement of the sea wall.
  • Cost estimates elevated structure: $2.4-2.8 billion.
  • Construction duration: 10 to 11 years [8 ][13]

Many prominent leaders and organizations are against an elevated structure and believe this is a unique opportunity to remove the viaduct and connect downtown Seattle to the waterfront. Former Governors Dan Evans and Gary Locke, former U.S. Senator Slade Gorton, and the American Institute of Architects recommend against rebuilding the viaduct.[14]

Surface option

This option was strongly backed by King County Executive Ron Sims,[15] the People's Waterfront Coalition,[16] and the Congress for the New Urbanism.[17] This option was not on the March 13th ballot, but a rejection of the other two proposals could have indicated support for this alternative. The state and county currently have experts exploring the proposal and will report back to leaders when their assessment is complete.

Proponents offer examples of successes in other cities and outline the plan and its potential benefits as follows:

  • Remove the viaduct completely and replace it with a surface street and transit improvements.
  • Proponents envision the waterfront becoming a pedestrian-friendly neighborhood that mixes commercial, retail, and public park spaces.
  • Traffic needs would be addressed through improvements to existing streets, I-5, and public transit.
    • Similar improvements will be necessary for the other proposals as well, due to closure of the viaduct during construction (estimated at 6–12 years).
  • The total cost of removal of the viaduct, repairing the seawall, and improvements to I-5 and existing streets is unofficially estimated to be $1.6 billion.
  • Highway removal or downsizing has worked in other cities.
  • Opportunity to improve connectivity in the street grid and improve public transit offerings.
  • Potential to improve the tourist economy, create jobs, and encourage a denser and more residential downtown through the offering of a generous waterfront park.

Due to removal, construction, or earthquake, there will be a multi-year period when the viaduct is closed. During this time, the city of Seattle could move forward with improvements to the downtown traffic grid and public transportation, while collecting information on whether additional transit capacity is needed.[18] This approach would allow Seattle to determine whether it can replicate the success of The Embarcadero in San Francisco, despite Seattle's comparative lack of light rail and trolley transit.

2007 Advisory Ballot

On March 13, 2007, an advisory ballot allowed citizens to vote on whether they supported a surface-tunnel hybrid and whether they supported an elevated structure alternative.[19] Voters rejected the surface-tunnel hybrid option 70% to 30% and rejected the elevated structure (rebuild) option 57% to 43%.[20]

It was unclear what it would have meant if voters approved both options.[21] Rejecting both options might have indicated a preference to earthquake-proof the existing viaduct or removal of the viaduct without replacing it.

Bored Tunnel Approved

In January 2008, as debate on its replacement continued, Governor Gregoire stated the State of Washington would take down the viaduct in 2012.[22] On May 12, 2009, Governor Chris Gregoire signed Senate Bill 5758, authorizing $2.8 billion in state funds for a deep-bore tunnel. As of January 12, 2009, the state, county, and city governments along with the Port of Seattle have settled on the tunnel option.


Excavation for the cut-and-cover tunnel option would have involved both excavation along the waterfront and a re-excavation of the existing Battery Street Tunnel, which is level with the viaduct. Critics frequently mention Boston's Big Dig project, which among other work included a viaduct's conversion into an underground tunnel, as illustrating the schedule and budget challenges of such a large project. However, proponents have pointed out that Seattle's bored-tunnel proposal would not be close to the scale of even the cut-and-cover segment of Boston's I-93 tunnel project, which also included significant bolstering or relocation of rail, roads, utilities and subway tunnels above and adjacent to the work.[23]

Current funding

  • $2 Billion - 2005 Gas Tax (Partnership Funding)
  • $177 Million - Transportation 2003 Account (Nickels Funding)
  • $207.5 Million - 2005 Federal Earmark Funds
  • $19 Million - Other Funds
  • $2.4 Billion - Total Funding Available From All Sources

Mayor Greg Nickels is attempting to attract $1 billion of funding from the federal government; his department has also outlined a financial plan which adds additional sources of funding which potentially total $2.6 billion.[24] With the termination of the Seattle Monorail Project, the Downtown Seattle Association is arguing for funding source used for the monorail project be used to replace the viaduct. The source for the monorail project was an excise tax based on tables approximating the value of vehicles registered within Seattle. The valuation tables have generated their own controversy, which resulted in the state wide tax vehicle excise being repealed.

See also


  1. ^ a b Garber, Andrew (January 13, 2009). "Tunnel in place of viaduct: A deal, but how to pay?". The Seattle Times. Retrieved January 13, 2009.  
  2. ^ a b c d e f g h i Lindblom, Mike (January 13, 2009). "Gregoire announces tunnel plans; car-tab taxes might help pay for it". The Seattle Times. Retrieved January 13, 2009.  
  3. ^
  4. ^ WSDOT Projects: Alaskan Way Viaduct and Seawall Replacement
  5. ^ Seattle Times:Shut down the viaduct (March 2, 2006)
  6. ^ Tunnel option off table for viaduct replacement
  7. ^ WSDOT - Project - SR 99 - Alaskan Way Viaduct and Seawall Replacement
  8. ^ a b c Seattle Channel -- News Room -- Alaskan Way Viaduct In-depth
  9. ^ Seattle Times: Climate's Right For Fresh Viaduct Plan (Oct 10, 2006)
  10. ^ Gov, lawmakers reject tunnel option to replace Seattle viaduct
  11. ^ Seattle Times: City, county, state agree on tunnel to replace viaduct (Jan 12, 2009)
  12. ^ No and Hell No, The Stranger
  13. ^ WSDOT Viaduct Alternatives Information
  14. ^ Open Letter to Governor Chris Gregoire
  15. ^ KNDO/KNDU: WA gov nixes `surface option' on Seattle waterfront; Sims furious
  16. ^ People's Waterfront Coalition
  17. ^ Congress for the New Urbanism
  18. ^ The Seattle Times: Shut down the viaduct.
  19. ^ official ballot - King County, WA Special Election, MARCH 13, 2007 (pdf)
  20. ^ King County Election Results
  21. ^ The Seattle Times: Politics: Viaduct vote set; state may ignore it
  22. ^ Seattle P-I: "Gregoire: 'Watch me' tear down the viaduct" (January 3, 2008)
  23. ^ Seattle Weekly: Seattle's Little Dig (April 19, 2006)
  24. ^ Seattle Times: Mayor finds $2.6 billion more to pay for viaduct tunnel plan (June 23, 2006).

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