The state is preparing for the final phase of construction on State Route 520 in Seattle. But the remaining projects will span a decade.
Work on the first of the final projects will resume next year when crews start building the new Montlake interchange. The state will announce a contractor for the work in the coming weeks.
The Montlake project will replace the old west approach bridge with a seismically stronger bridge parallel to the completed West Approach Bridge North. A highway lid and transit hub on Montlake Boulevard East will be built, along with a new SR 520/Montlake Boulevard East interchange and bicycle-pedestrian bridge over SR 520. That work won't be finished until 2023 or 2024.
In 2020, crews will start building a new bus and carpool connection between SR 520 and South Lake Union via the I-5 express lanes.
Later on, the Montlake Cut Bascule Bridge Project is planned to add a second, parallel drawbridge across the Montlake Cut.
Finally, the state will replace the old Portage Bay Bridge with two new structures that will include an extension of the SR 520 Trail, a new Roanike lid, and a connection over I-5 for bicycles and pedestrians. That project won't be done until around 2029.
The remaining work will cost approximately $1.6 billion.
“We refined our delivery plan for upcoming construction to assure we keep traffic flowing while building multiple SR 520 corridor improvements,” said Denise Cieri, SR 520 Program administrator. “These improvements are needed to replace the aging and seismically vulnerable corridor structures west of the new floating bridge.”
Construction on SR 520 began in 2011. Since then, the state has rebuilt the highway on the Eastside between I-405 and Lake Washington. The old floating bridge was replaced and the first of two west approach bridges across Union Bay opened.
