WSDOT and the City of Seattle consider a list of 76 replacement concepts and narrow the list to five alternatives for further consideration.

• The Federal Highway Administration (FHWA), WSDOT and the City of Seattle release a Draft Environmental Impact Statement (EIS) that includes evaluations of five alternatives: a rebuilt viaduct, a new aerial structure, a single-level cut-and-cover tunnel, a bypass cut-and-cover tunnel, and a six-lane surface boulevard.
• The three agencies identify a cut-and-cover tunnel as the preferred alternative. The rebuild alternative is carried forward as an alternate option, if it is determined there is not enough funding for the tunnel.

Engineers complete further design work on the tunnel and rebuild alternatives.

• The “rebuild alternative” is renamed the “elevated structure alternative” to better represent changes made to the design since the Draft EIS was published.
• The State Legislature requires an expert review panel to study the feasibility of both alternatives.
• As a result of the panel’s report, WSDOT updates cost estimates for both alternatives to adjust for rising inflation rates and worldwide increases in construction material costs.
• The Legislature directs the Seattle City Council to adopt an ordinance stating their preferred option. The Council reaffirms its support of a tunnel.
• FHWA, WSDOT and the City of Seattle release a Supplemental Draft EIS to provide more detailed information on the two alternatives and potential construction plans.
• Governor Gregoire calls for a vote by the citizens of Seattle.

• An advisory vote is held in Seattle, calling for an up-down vote on a surface-tunnel hybrid and an elevated structure. Both receive a majority “no” vote.
• WSDOT, King County and the City of Seattle move forward with critical safety and mobility improvements to the Alaskan Way Viaduct. These projects will replace about half of the viaduct, and will fit with any chosen design for replacing the downtown waterfront section.
• WSDOT begins a collaborative process with Seattle and King County officials to determine the replacement for the central waterfront section of the viaduct.

• In April crews finish reinforcing four viaduct columns between Columbia Street and Yesler Way, where the structure had settled several inches since the 2001 Nisqually earthquake.
• FHWA and WSDOT release an Environmental Assessment for replacing the viaduct's south end between South Holgate and South King streets.
• In September crews begin relocating electrical lines that are attached to the viaduct's south end.
• WSDOT, King County and the City of Seattle work together to find a solution for the viaduct's central waterfront section. The agencies develop and evaluate eight draft scenarios, or comprehensive solutions, which cover a range of options, from a smaller road along the central waterfront and significant investments in transit and surface streets, to bypass roadways with fewer transit and surface street investments.
• These options are narrowed down to two hybrid scenarios - an “I-5, surface and transit" alternative and an “SR 99 elevated bypass” alternative. The hybrids package together elements from the previous eight scenarios, including improvements to I-5, surface streets and transit. Stakeholders express concerns about how surface and elevated options would affect the waterfront and maintain mobility both during and after construction and press for further analysis of a bored tunnel option.

• In January Governor Gregoire, King County Executive Sims, Seattle Mayor Nickels and Port of Seattle CEO Yoshitani recommend replacing the central waterfront section of the Alaskan Way Viaduct with a bored tunnel beneath downtown, a new waterfront surface street, transit investments, and downtown city street and waterfront improvements.
• The State Legislature endorses the bored tunnel in April and provides the budget authority necessary for its construction. Governor Gregoire signs the bill into law in May.
• In July crews begin relocating utilities in preparation for road and bridge construction to replace the viaduct between South Holgate and South King streets.
• The Governor and Seattle Mayor sign a memorandum of agreement in October that outlines the State and City's responsibilities for the viaduct replacement program.
• At the end of the year, crews finish relocating electrical lines from the viaduct's south end.

• WSDOT releases an updated cost estimate and tolling study for the Alaskan Way Viaduct replacement in January. This report, requested by the Legislature, shows that the viaduct replacement's cost estimate remains within its $3.1 billion budget, and that it is feasible to generate $400 million in toll funding for the replacement.
• Road and bridge construction to replace the viaduct between South Holgate and South King streets begins in June.
• Governor Gregoire announces that both bids submitted in October to design and build the SR 99 bored tunnel are at or below the contract price limit. The submittals are from two teams of national and international tunneling firms.
• In October FHWA, WSDOT and the City of Seattle release a second Supplemental Draft EIS, which examines potential environmental effects of the proposed bored tunnel.

• WSDOT signs a contract in January with Seattle Tunnel Partners to design and build the SR 99 bored tunnel. The agency directs the design-build team to continue preliminary design work. If tunnel plans are approved at the conclusion of the project’s environmental review, Seattle Tunnel Partners will begin final design and construction of the bored tunnel.
• On Feb. 18, crews demolish part of the northbound SR 99 on-ramp from First Avenue South. The ramp demolition is the first piece of viaduct removed since the structure was built in the 1950s. This work is part of building an SR 99 construction bypass to keep the highway open and traffic moving as crews demolish the viaduct's south end.
• FHWA, WSDOT and the City of Seattle release the Alaskan Way Viaduct Replacement Project Final EIS in July. The document compares three build alternatives (bored tunnel, cut-and-cover tunnel and elevated structure) for the viaduct's central waterfront replacement and explains why a bored tunnel is the preferred alternative.
• FHWA in August signs a record of decision approving a bored tunnel beneath downtown Seattle as the replacement for the viaduct's central waterfront section.
• Following issuance of the record of decision, WSDOT directs Seattle Tunnel Partners to begin work on the second phase of their design-build contract - final design and construction of the SR 99 tunnel.
• At the end of October, during a week-long closure of the viaduct, crews demolish most of the structure's south end in SODO and complete a bypass connecting a new SR 99 bridge with the viaduct along the downtown waterfront. Removal of the structure's south end allows crews to begin building a second SR 99 bridge in the footprint of the demolished viaduct.