I've only had a chance to glance over the Washington State Department of Transportation workgroup's 28-page report and 16 attached white papers released today about the 520 Bridge—which will be replaced with a wider, safer span across Lake Washington—but you can go over and check out the report for yourself.
The stuff that stands out is a debate over whether the bridge will ever accommodate light-rail. This issue was a source of intense friction between the state, mayor, and city council—many arguing that transit advocates should shut their rail-sucking pie-holes so the state could get on with building a bridge 14 years in the planning. But there seems to be some benefit for hollering about light-rail. From one of the report's appendices called "Light rail transit accommodation" (.pdf):
It is clear that there will be a need for construction and additional costs to add light rail to the SR 520 corridor, but the costs and risks associated with such an addition have been minimized by the design elements included in the preferred alternative. WSDOT designers have remained within the boundaries of the project scope for the preferred alternative, yet there has been a concerted effort to accommodate future light rail transit. WSDOT designers are incorporating light rail options under several future bridge configurations.
The design is such that light rail transit (LRT) can be brought to the corridor both as a substitute for the HOV lanes (4 general purpose lanes plus 2-way LRT) and as an addition to the bridge described in the preferred alternative (4 general purpose lanes plus 2 HOV lanes plus 2-way LRT). Without a specific LRT alignment and service plan for the SR 520 corridor, the multiple design options accommodate a number of potential configurations.
- WSDOT — Click for larger image
- The 520 interchange at Montlake (key: gray are general freeway lanes, yellow are general purpose local streets, blue are transit/HOV lanes, orange are on and off ramps, turquoise are bike and pedestrian paths)
However, Mayor Mike McGinn, in a September 13 letter included in the main report, says light rail remains unfeasible:
If this project were built according to the current specifications, adding light rail to the SR 520 corridor at a future time will be financially and/or environmentally infeasible. The detailed study needed to truly ensure that light rail is easily accommodated has not occurred. [...]
While the SR 520 design team has made a strong effort to ensure LRT accommodation, I am concerned that the future cost of adding pontoons, retrofitting portions of the bridge and approaches, and new construction—as well as potential environmental impacts associated with doing this work in the future—do not truly accommodate light rail on the corridor and render implementation of LRT nearly impossible.
Transit nerds, what do you say? Is light rail still unfeasible, totally workable?