Sound Transit Shares Complete Level 3 Alternative Concepts for West Seattle and Ballard Extensions


Sound Transit has developed two complete alternative concepts for the West Seattle and Ballard light rail extensions. The alternatives marry together remaining segment alternatives that the Elected Leadership Group had winnowed down in October. When sharing the alternatives, Sound Transit had not released cost differences and ridership numbers, but using earlier numbers of comparative segment alternatives, it is possible to piece together how these may perform comparatively to the ST3 Representative Project alternative. On the basis of ridership and cost, it is not clear that the alternatives are more productive than the baseline alternative, but there may still be merit to the options that they present.

ST3 Representative Project Alternative

ST3 Representative Project alternative alignment. (Sound Transit)
ST3 Representative Project alternative alignments. (Sound Transit)

The ST3 Representative Project alternative is the baseline option and used as a comparative to measure other alternatives. If built, the two corridor alignments of the alternative are projected to generate 232,100 daily riders by 2040.

For the West Seattle extension, the alignment would consist of an elevated line from Alaska Junction through SoDo before transitioning to the surface and eventually a tunnel in Chinatown-International District. The West Seattle line would have a high-level fixed bridge over the Duwamish River and directly tie into the existing light rail line headed toward Capitol Hill and University of Washington, continuing onward to Lynnwood.

From Ballard, the alternative provides for a mostly elevated alignment across Salmon Bay and through Interbay. The line would would start at 15th Ave NW and NW Market St. The line would transition to a tunnel as it approaches Uptown, running under Republican Street. The line would remain underground through South Lake Union and turn on Westlake Ave N to head toward Downtown. The line would then turn onto Fifth Avenue, providing a connection to the existing Westlake Station and continue to Chinatown-International District. A new cut-and-cover tunnel would be created immediately to the east of the existing one in Chinatown-International District.

West Seattle Elevated / C-ID 5th Ave / Downtown 6th Ave / Ballard Elevated Alternative

West Seattle Elevated/C-ID 5th Ave/Downtown 6th Ave/Ballard Elevated alternative alignments. (Sound Transit)
West Seattle Elevated/C-ID 5th Ave/Downtown 6th Ave/Ballard Elevated alternative alignments. (Sound Transit)

As the name suggests, the West Seattle Elevated / C-ID 5th Ave / Downtown 6th Ave / Ballard Elevated alternative would generally consist of an elevated line from West Seattle before transitioning to at-grade in SoDo to connect with the existing Central Link line using the E3 Busway. The line would start at elevated station centered on 41st Ave SW and SW Alaska St. To cross the Duwamish River, Sound Transit would use a high-level bridge. New roadway overpasses would be constructed at S Holgate St and S Lander St to improve train speeds and reduce conflicts.

Meanwhile, the line to Ballard would enter a tunnel just east of the Stadium Station and run under 6th Ave S using either mined or cut-and-cover methods. The line would swerve over to the 5th Ave S as it approaches Chinatown-International District and remain under Fifth Avenue until eventually turning onto Terry Avenue to reach South Lake Union. The line would provide a direct transfer point at Westlake Station. To reach Uptown, the line would continue underground along Mercer Street and then daylight near Smith Cove at the surface, just north of the Helix Bridge. Once reaching the Interbay Golf Course, the line would transition to using elevated track and use a fixed bridge to cross Salmon Bay to the east of the existing Ballard Bridge. The line would terminate with an elevated station at NW Market St and 14th Ave NW.

Gleaning from the analysis of earlier work during the Level 2 process, this alternative would cost at least $200 million more than the ST Representative Project alternative. It would also generate approximately 240,000 daily riders, a full 8,000 more than that the baseline alternative.

The biggest issues of this alternative are likely to be the fact that it would include a fixed bridge over Salmon Bay and its terminal location in Ballard. With a high fixed bridge over Salmon Bay, there will undoubtedly be environmental issues with in-water construction and concerns over views that the bridge would obstruct. The alternative also presents mobility and access challenges with a Ballard station on 14th Ave NW instead of a station straddling the heart of the neighborhood on 15th Ave NW, similar the tunnel alternative.

West Seattle Tunnel / C-ID 4th Ave / Downtown 5th Ave / Ballard Tunnel Alternative

West Seattle Tunnel/C-ID 4th Ave/Downtown 5th Ave/Ballard Tunnel alternative alignments. (Sound Transit)
West Seattle Tunnel/C-ID 4th Ave/Downtown 5th Ave/Ballard Tunnel alternative alignments. (Sound Transit)

The West Seattle Tunnel / C-ID 4th Ave / Downtown 5th Ave / Ballard Tunnel alternative consists of several small alternatives for tails in West Seattle and Ballard as well as tunnel transitions near SoDo and Chinatown-International District. In West Seattle, Sound Transit has identified three possible tunnel station locations on 41st Ave SW, 42nd Ave SW, and 44th Ave SW that would form the end of the line. All of these stations would be centered on SW Alaska St. The line would then continue as a tunnel until daylighting as an elevated line at SW Avalon Way. To cross the Duwamish River, the line would use a high-level bridge.

At S Forest St, the West Seattle line would transition to surface to connect with the existing Central Link line using the E3 Busway. Two new roadway overpasses would be constructed at S Holgate St and S Lander St to improve train speeds and reduce conflicts.

For the Ballard line, trains would enter a new tunnel just south of the existing Stadium Station. The tunnel would either be constructed using a cut-and-cover or mined technique under 4th Ave S. Riders would be able to connect with existing services at International District/Chinatown Station and King Street Station. The underground line would continue up Fifth Avenue and include another transfer point to light rail directly at Westlake Station. The underground line would eventually turn onto Westlake Avenue to reach South Lake Union. As the line moves westward toward and through Uptown, it would slink along Harrison Street and Republican. This would provide very direct access to Seattle Center and Key Arena.

Eventually, the Ballard line would daylight in Smith Cove, near W Prospect St. A surface station would be located immediately after at W Prospect St and Elliott Ave W to serve Interbay. The line would then continue until transitioning to elevated guideway near 15th Ave W to make the crossover toward the BNSF railway. The line would return to at-grade for a retained-cut station W Bertona St and Thorndyke Ave W and then dive underground to pass beneath Salmon Bay. The alternative consists of two terminal station in Ballard: one on 15th Ave NW and another on 14th Ave NW at NW Market St.

Basing estimates on earlier analysis at the Level 2 stage, this alternative would likely cost at least $1.5 billion more than the ST Representative Project alternative. The alternative would also generate approximately 227,500 daily riders, which is 4,600 fewer than the baseline alternative. However, the station locations on 15th Ave NW and alternative locations in Alaska Junction could improve those ridership numbers for similar cost. The tunnel options in Chinatown-International District and under Salmon Bay could also tilt the costs, either increasing or decreasing the from the $1.5 billion overage estimate.

The station locations in Ballard and West Seattle have various tradeoffs with proximity to neighborhood cores and other frequent transit connections. A 15th Ave NW station location would save riders additional walking to bus stops on NW Market St and 15th Ave NW. It would also help ensure that people living and working in the heart of Ballard — which is generally considered to be west of 15th Ave NW — do not have to cross a very busy thoroughfare. Light rail, however, does present an opportunity to tame local arterials and even trim them down. Regardless of which avenue (15th Ave NW or 14th Ave NW) is chosen in Ballard, a station will invariably open up discussions about expansion of the neighborhood Urban Village and zoning changes within walking distance.

For West Seattle, the station location in Alaska Junction is not necessarily faced with the same traffic challenges as Ballard. Nevertheless, where to put the station does make a difference in how close many riders might live. It could also impact how the Urban Village there should develop in the future. Put a station near the near 44th Ave SW, and Urban Village expansions further west might be practical. Put the station near 41st Ave SW, and higher density zoning changes north and south may be worth consideration.

Perhaps the most fundamental issue of this alternative is the cost of tunnels, which come with higher financing requirements and time to construct. If chosen, Sound Transit and its partners will need to identify extra financing and determine tunnel construction methods. For instance, the alternative Chinatown-International District has two different paths for tunnels, each with its own constructibility issues. Putting a tunnel under 4th Ave S also has engineering challenges and will require reinforcement or replacement of other structures above.

More alternatives analysis to come, getting it right is critical

The bottomline is that the two competing alternatives would appear to deliver similar ridership numbers for higher cost to the ST3 Representative Project alternative, but there may be real justification for paying a bit more to achieve better long-term results.

The ST3 Representative Project alternative may hamstring the light rail system in the future as it expands, suppressing future ridership. Building the wrong type of crossing in Ballard may slow down trains in perpetuity. Building a cut-and-cover tunnel on 4th Ave S could heavily disrupt the community in Chinatown-International District and greatly impact businesses. And building a substandard light rail segment in SoDo could risk collisions and delays forever.

Ballard and West Seattle will not be the end of line for all time, they are just temporary stopping points. Expansions to the north, south, and east are inevitable. Getting the investments right in those areas is critically important, and that should be something heavily considered in the final Level 3 alternatives analysis.

In the next two months, the Stakeholder Advisory Group and Elected Leadership Group are both due to release final recommendations on the Level 3 Alternatives. A preferred alternative is then scheduled to be identified sometime in April.

We hope you loved this article. If so, please consider subscribing or donating. The Urbanist is a 501(c)(4) nonprofit that depends on donations from readers like you.

Stephen is an urban planner with a passion for sustainable, livable, and diverse cities. He is especially interested in how policies, regulations, and programs can promote positive outcomes for communities. Stephen lives in Kenmore and primarily covers land use and transportation issues for The Urbanist.

Inline Feedbacks
View all comments

I can’t help but notice ST put all the tunnel options together in one package as a way to create sticker shock to kill those options. Even though every tunnel option is completely independent of each other and can be mixed and matched with any of the alignment options. Again its obvious to me that ST is going to force a bridge crossing with a station at 14th in Ballard. If they want to save money that bad they should just cancel the Ballard crossing/station and terminate in Interbay. 14th is a stupid location.

Stephen Fesler

I don’t think the intention was sticker shock to avoid doing tunnels. I think the point was to show the baseline, middle of the road, and high-end options for comparison. Most of the cost is built into the West Seattle tunnels which would exceed $700 million for absolutely no benefit beyond aesthetics. It would be helpful in the next stage to show the ELG that West Seattle concept is absolutely unnecessary whereas the debates surrounding the C-ID and Ballard tunnels have more merit.

If I were a betting man, I would say that ST will build the station at 15th Ave NW, as feedback has been very insistent on this point in absence of a more central location in Ballard. But hey, it never hurts to reiterate that point by contacting the ELG and Sound Transit to avoid bungling this.

Owen Wagenhals

How is there any other alternative to the Ballard Station other than: “Underneath 15th & Market, with 4 exits: one on each corner”?


If Ballard doesn’t get a station on 15th, can we get an ST3 revote? 14th Ave is just a completely ridiculous spot for Ballard’s only station compared to where people actually live in Ballard and provides essentially no ability for northward expansion. I would have voted no if that was in the package at the time.