The 4.1 miles of light rail service known as the West Seattle Link Extension now has a final route plan that includes four stations and a new bridge, a key step in moving toward the start of construction on the $6.7-billion to $7.1-billion project in 2027. 

Sound Transit is the operator of light rail and transit in the greater Puget Sound region, which includes Seattle, Bellevue, Tacoma and Everett. It continues an effort to expand light rail service in all directions, part of a plan to form a 116-mile regional system in the coming decades. 

Now that the Sound Transit board has selected the final route and station locations for the West Seattle Link Extension, work can progress toward the final design phase ahead of a start of construction in 2027 with a planned service date of 2032. 

“Through the board-directed work plan, our action today allows Sound Transit to use the design process to address cost pressures, reduce impacts and prepare projects for construction,” Dow Constantine, Sound Transit board chair and King County Executive, said in a statement. 

The 4.1 miles of light rail track will feature three new stations at Delridge, Avalon and Alaska Junction after branching off the existing SoDo station. The three stations are located across the Duwamish Waterway, requiring a light-rail-only bridge. 

The project also features tunneling, with the new Avalon station in a lidded retained cut and the new Alaska Junction Station in a tunnel beneath 41st Avenue Southwest and Southwest Alaska Street. Other portions of the plan feature both at-grade and elevated track. 

Map courtesy Sound Transit

The project was approved by voters in 2016 as part of the ST3 plan, the largest infrastructure program in Seattle’s history. The rough new estimates for the project's cost represent a sharp increase from the $4 billion projection in 2023. 

Goran Sparrman, Sound Transit interim CEO, says that an amendment in the approval allows the agency to work to reduce project impacts and answer financial questions during the design phase. 

“As we begin to implement the work plan and address cost pressures, we will be engaging with the construction industry sooner to identify the best way to approach our projects and developing ways to create greater efficiencies once we enter construction," he says.

The final alignment incorporates tweaks requested by the board when it first identified the preferred alternative in 2022. The changes prioritize transfers between light rail and bus, improve station access and address concerns over undue displacements of organizations serving low-income residents. 

Sound Transit plans to return to the board as design progresses to authorize construction dollars.