Two proposed light rail extensions west of Seattle include major infrastructure needs. The West Seattle Link Extension, proposed for 2030, includes a new fixed bridge, while the 2035 Ballard Link Extension requires both a new downtown Seattle light rail tunnel and a movable bridge.

As both projects come into view, Sound Transit has started “early scoping” on the projects, providing a chance for the public to weigh in on route and station locations as the agency aims to reach a consensus preferred alternative route by early 2019.

Both extensions move light rail west of Seattle, with the West Seattle portion heading across the Duwamish River with a 4.7-mile track extension. The Ballard extension runs mostly northwest 7.1 miles and requires a 3.3-mile downtown tunnel.

As per the voter-approved Sound Transit 3 plan, the West Seattle Link Extension builds light rail from West Seattle’s Alaska Junction neighborhood to downtown Seattle primarily on an elevated guideway with a new rail-only fixed span crossing the Duwamish River south of Elliott Bay. Plans show the extension connecting with existing service, continuing north to Lynnwood and Everett.

Also part of the ST3 plan, the Ballard Link Extension includes the downtown Seattle Light Rail Tunnel and builds light rail from Ballard’s Market Street area through downtown Seattle with both tunneled and elevated alignments and a rail-only movable bridge over Salmon Bay near the Ballard Locks. This plan connects to existing service, continuing south to Tacoma.

Of the 7.1-mile Ballard extension, expect to see a new 3.3-mile rail-only tunnel from the International District/Chinatown to South Lake Union and Seattle Center/Uptown, an elevated guideway along 15th Avenue West and Elliott Avenue West and a rail-only movable bridge over Salmon Bay. The project includes three elevated stations and six tunnel stations.

Together, the projects total 10 new and four expanded stations.

During this public scoping portion of the project, staff will assess the projects and based on technical analysis and public comment, further refine the route, station locations and other project elements. The projects have already undergone multiple years of planning and public involvement, including transit studies.

Sound Transit says that by bringing the public into the process it will help identify the preferred alternative earlier in the Environmental Impact Statement process to “streamline” the process and reduce overall project delivery time by reaching early public consensus on the preferred alternative and reducing the risk of new alternatives being introduced late in the environmental review process or after the environmental process wraps up.

The Sound Transit Board will make a final decision on the project to build after completion of the environmental review.

Along with the plans to extend to West Seattle and Ballard, Sound Transit is working to expand north, south and east, opening new stations every few years to form a 116-mile regional system by 2041.

Sound Transit is on track to open extensions to Seattle’s University District, Roosevelt and Northgate in 2021, followed by service to Mercer Island, Bellevue and Redmond’s Overlake area in 2023. Extensions to Kent/Des Moines, Federal Way, Shoreline, Mountlake Terrace, Lynnwood and downtown Redmond are all scheduled for 2024. Tacoma is on the docket for 2030, Paine Field and Everett in 2036 and South Kirkland and Issaquah in 2041.

Follow Tim Newcomb on Twitter at @tdnewcomb