Requires that, as soon as practicable after the effective date of this act, the department shall hire a mediator, and appropriate planning staff, including urban, transportation, and neighborhood planners, to assist the department in developing a state route number 520 expansion impact plan for addressing the impacts of the state route number 520 bridge replacement and HOV project on Seattle neighborhoods, parks, and institutions of higher education, and the city of Seattle.

Requires the state route number 520 expansion impact plan to be submitted to the commission, which shall oversee the development of the plan. The commission shall approve the plan sixty days before the propositions required under RCW 36.120.070(2) and 81.112.030(10) are submitted to regional voters at the 2007 general election, or before the beginning of the 2008 regular legislative session.