Ballard Link Mode Selection

A decade ago, Sound Transit hired experts to review transit modes to select the best mode for the Spine which could accommodate at-grade, elevated, and tunneled sections. It reconfirmed the decision to proceed with building a light rail network. At the time modes such as monorail and the Vancouver, BC SkyTrain were dropped as they do not work well for at-grade alignments. However, for many of the modes they considered at the time, the experts pointed out that other options may have advantages in other circumstances.

As Sound Transit is restarting the Environmental Impact Statement work for the Ballard Link Extension, it would be great if they would also update their mode selection. If the Ballard line would be kept separate from the Rainier Line as suggested in the past, there would not be any at-grade portion. The requirements for such urban line would be quite different from the more regional Spine. Technology has also evolved since: most recent rail projects have been fully automated lines with shorter and more frequent trains such as Vancouver's SkyTrain, Honolulu's Skyline, Montreal REM, Milan M4. Some consider it a worldwide standard by now. It allows for smaller stations which are easier to locate and construct.

Modern guideway systems such as used by the TSB maglev, promise simpler and faster construction. Prefabricated modules are constructed offsite and hoisted in place at night or over a weekend. This reduces construction-related detours and inconveniences. Such problems were cited by Amazon to push the station off the Westlake & Denny intersection and by Interbay residents to keep the line off of 15th Ave W. Linear induction motors (LIM), such as the SkyTrain's Canada Line uses, allow for steeper gradients; e.g., TSB allows for 10% gradient. While light rail trains have to descend gradually under the ship canal, LIMs allow for steeper gradients allowing stations and tunnel entrances be located closer to the canal. This allows for higher flexibility to locate the stations, for example north of Dravus. As the power supply is integrated into the guideway, no overhead wires are necessary, which not only simplifies construction but also reduces maintenance, allows for smaller tunnel diameter, and reduces visual clutter. While light rail guideways with their typical noise-reduction side panels are just as imposing as a road bridge, modern guideway systems such as TSB maglev are even less obtrusive (4ft high instead of 5ft) than monorail systems (though two guideways rather than one) allowing sunlight to penetrate in between. While the Seattle Center Monorail posts are 70 feet apart making it difficult for cars to maneuver underneath, TSB supports spans of up to 120 feet therefore allowing street crossings including turn lanes underneath.

Ballard Alignment

While Sound Transit plans 3 stations in West Seattle, for Ballard it has focused on a single station either along 15th or 14th Ave NW. During public meetings many have complained that 14th Ave is too far from the historic center (Ballard Ave) and they would rather have a station along 20th or 22nd Ave. A smaller station size may allow a station along 15th Ave NW and then the line could turn west along NW 56th St with another station east of the public library (between 20th and 22nd). A smaller station size would also allow the line to turn north again and continue along 24th Ave NW in the future.

To avoid the cost of a long tunnel, a TSB line could be elevated instead. As TSB lines only needs about 400 feet to come up from a tunnel to an elevated line, it would allow a train to go under the ship canal but instead of continuing underground, surface north of Leary Way, then turn west along NW 50th St and Russell Ave, and continue along 22nd Ave NW. This would allow a station on NW 50th St and one by the library or Ballard Commons Park.

Interbay Alignment

Originally Sound Transit had planned a line along Elliott Ave W and 15th Ave NW with a bridge over the ship canal. Residents were concerned about traffic impacts caused by the line crossing Elliott Ave. The Port was concerned about losing a corner of Fisherman's Terminal. When a tunnel under the ship canal was prioritized, Sound Transit had to find space to surface the trains which is difficult along 15th Ave NW. Instead, a line parallel to Thorndyke Ave W with a station under W Dravus St and by Galer was selected as the preferred alignment. With reduced station and guideway size and related construction impact, reduced visual impact, and improved climbing out of the ship canal tunnel, Sound Transit may be able to revive the original alignment and require far less property acquisitions and provide better connections with existing bus lines.

Seattle Center/SLU Alignment

Several businesses have voiced concerns about the planned light rail construction around Seattle Center and South Lake Union. Sound Transit has made several adjustments to reduce such impact, but often that has created other issues. Smaller station size could not only reduce the construction and therefore impact time, but it could also limit the construction to a single block. The Denny Station box construction may fit within the South Lake Union Discovery Center site which would eliminate the impact to both Westlake Ave and Denny Way and still allow a turn towards a (smaller) station on Harrison St without disturbing the 7th Ave onramp.

If the tunnel turns out to be too expensive and the SLU streetcar gets shut down, it might even be an option to build the line as an elevated TSB line. It could go up from Elliott Ave W along W Mercer St and continue on Westlake Ave N (instead of the streetcar) to meet the 1 Line at Westlake Center. In the future it could be extended along 6th Ave, Spring St, and Boren towards Judkins Park and Mt Baker Station, quite similar to the tunnel proposed earlier.

Comments Due

Please contact Sound Transit with your input by December 9th.