When the Washington State Dept. of Transportation opened the world’s longest floating bridge to much fanfare in 2016, it marked the most impressive portion of the $4.5-billion reconstruction of State Route 520.

But by no means did it signify the completion of the project.

The first of the four final projects to complete the SR 520 reconstruction in Seattle will resume in 2019 when crews break ground on the Montlake Project, a new SR 520-Montlake Boulevard interchange near the University of Washington. Project owner WSDOT expects to announce a contractor in October.

Then, in 2020, crews will begin building a new bus and carpool connection between SR 520 and South Lake Union via the Interstate 5 express lanes. The remaining projects (all four have been dubbed the “Rest of the West”) include two bridges and will complete the reconstruction of a highway that connects Seattle to points east such as Bellevue.

“We refined our delivery plan for upcoming construction to assure we keep traffic flowing while building multiple SR 520 corridor improvements,” says Denise Cieri, SR 520 Program administrator, in a statement. “These improvements are needed to replace the aging and seismically vulnerable corridor structures west of the new floating bridge.”

Overall, all four projects will take about 10 years to complete.

The Montlake Project includes a landscaped lid over SR 520 with regional transit stops, a bicycle/pedestrian land bridge with green space east of the lid and a west approach bridge south for eastbound traffic between Montlake and the floating bridge.

The project replaces a 1960s-era approach bridge and eases high-capacity congestion in the area. WSDOT is still working through legal issues regarding acquiring the property where a market and gas station are located. The $400-million project should begin construction in early 2019 and wrap sometime in 2024.

The I-5 Express Lanes Connection Project adds a new reversible transit/HOV ramp between SR 520 and the I-5 express lanes, providing enhanced service between areas east of Seattle and South Lake Union. WSDOT expects the project to begin construction in 2020 and complete no earlier than 2023.

For the Montlake Cut Bascule Bridge Project, WSDOT plans to build a second, parallel drawbridge across the Montlake Cut near the University of Washington. The project is currently in the planning phase.

A new Portage Bay Bridge and Roanoke Lid Project, expected to start in 2023 and wrap up no earlier than 2029, will replace the 1960s-era Portage Bay Bridge, currently supported by hollow concrete columns. The new bridge will replace the old structure with more security while extending SR 520’s transit/HOV system and cross-lake bicycle and pedestrian trail.

To replace the current four-lane bridge, WSDOT plans two parallel three-lane bridges, one for eastbound traffic and one for westbound traffic.

A landscaped Roanoke lid over SR 520 is included in the project, along with a 30-ft-wide bicycle and pedestrian crossing over I-5.

Follow Tim Newcomb on Twitter at @tdnewcomb