Policy, Planning, & Major Projects

Improving Mercer Corridor: Environmental Studies

In November 2004, the City Council released funds to complete the Environmental Review of the Mercer Corridor Project and recommended the Two-way Mercer and Narrow Valley Alternative for study. SDOT is completing a federal Environmental Assessment (EA) and will adopt it as a state Environmental Impact Statement (EIS) or issue a Determination of Non-significance if appropriate. There is a comprehensive public involvement process that includes check-ins with City Council. To learn more about the federal and state requirements guiding environmental documentation and how the Mercer Corridor Project relates please read the Mercer Environmental Review Summary.

Alternatives Considered During the Scoping Phase

SDOT identified three alternatives before concluding that two-way Mercer is the best solution.








Screening the Alternatives

The Project Team identified a set of measures to evaluate how well each of the three alternatives would meet or advance the Project Objectives. The purpose of this first screening exercise is to identify which alternative or alternatives should be carried forward into the environmental documentation, the EA. (Description of Objectives and Measures)

The three alternatives were evaluated with and without the Alaskan Way Viaduct and Seawall Project (AWV/S) alternative (Widened Mercer Underpass).

After screening the alternatives, the Project Team hosted a stakeholder workshop to explain the screening process and share the project objectives, measurements used and screening results for each alternative. The measures and ratings were modified as a result of stakeholder input. Stakeholder Workshop Summary

Alternatives Screening Results The Project Team determined that the Two-way Mercer alternative is the only alternative that meets all of the project objectives, and therefore recommended that it be carried forward into the Environmental Assessment as the City's preferred alternative.

Coordination with the Alaskan Way Viaduct and Seawall Replacement Project (AWV)

The AWV project includes changes to Aurora Avenue North north of the Battery Street Tunnel that will reconnect Queen Anne and South Lake Union, including two-way Mercer across Aurora, and improve access to State Route 99.

The Mercer Corridor Project is compatible with the AWV preferred alternative, as well as the AWV No Build scenario. The Mercer Corridor EA will include an analysis of how the two projects work together, as well as look at the cumulative impacts of other projects in the area. For more information on the AWV project visit:

Alaskan Way Viaduct and Seawall Replacement Project Website