A note to plan accordingly. No point in getting stuck waiting for a barge to cross as you try to get the start line. From Washington DOT:
Attention cyclists and Seattle to Portland participants:
The I-90 bike and pedestrian path on the floating bridge will close after 9 p.m. Friday, July 10 to all bicycle and pedestrian traffic and scheduled to reopen by 6 a.m. Saturday, July 11, to allow crews to set the expansion joint. Make backup plans for crossing Lake Washington.
The SR 520 bridge will be temporarily closed to traffic sometime between 3-6 a.m. Saturday, July 11, to allow a construction barge to pass. The closure will last at least 30 minutes. Those driving to the Seattle-To-Portland start line Saturday morning should allow extra time for this closure or take I-90 to UW.