An all-underground light rail extension of Seattle’s Northgate Link westwards to Ballard makes it to Sound Transit’s Candidate Project list for final study.

Following a month of public consultation on a variety of transportation projects for construction in the future, the Ballard to U-District Station tunnel option via Wallingford is preferred to both at grade and bus alternatives for this corridor (Fig 1). As well as a connection to the University District, the proposed link would offer Ballard residents onward underground connection south and east to downtown and across Lake Washington to Bellevue via the under construction Northgate Link and University Link. Both the 5.5km Northgate Link and 3.15km University Link were approved as part of ST1 in 2008.

The Ballard to U-District Station proposal, costed in a 2014 study at between US$1.4-1.9 billion, is one of a number of transportation corridors across the Seattle area that will now go forward for further study ahead of selection by the Sound Transit Board of a final list to be put to voters in the ST3 ballot in November 2016.

A number of other light rail transportation projects that are carried forward for final review have the potential for underground construction works – among them the possibility of a direct rail connection between existing and planned Ballard and West Seattle light rail extensions via a new downtown tunnel. A grade level alternative is also carried forward.

Elsewhere, extensive consultation over the last three years along eight corridors and alignments for a light rail connection between downtown Seattle and Ballard’s Market Street area have been whittled down to four options (which are broadly covered in Fig. 2, though the key to construction methods for each alignment is out of date). Three of these alignments retain the possibility of a tunnel crossing of the Washington ship canal, and include:

• A connection via Uptown, serving Seattle Center, which would include a movable bridge in exclusive lanes and at-grade light rail in exclusive lanes on 15th Ave NW and Elliott Avenue W (Fig 2, broadly red), with signal priority so trains would generally stop only at stations.
• An elevated light rail connection along 15th Ave NW and Elliott Ave W, with a movable bridge over the ship canal (Fig 1, broadly blue). A tunnel option is possible through Uptown, serving Seattle Center, and into downtown Seattle (Fig 2, broadly green).
• Elevated light rail along the west side of the Interbay corridor, also serving Uptown and the Seattle Center, crossing the Ship Canal via a tunnel [the alternative of a moveable bridge has been deleted from this alignment following the latest consultation].
• A grade level connection in exclusive lanes with signal priority via Westlake Avenue (Fig 2, broadly yellow), and serving South Lake Union and Fremont. The ship canal crossing would be either a movable bridge or via a tunnel.

Fig 1. Tunnel option (brown) preferred on Ballard to U-District corridor

The most popular alignment in the Downtown–Ballard corridor, as identified by residents during numerous consultations, was also the most expensive option at US$3.5 billion. This alignment, which doesn’t make it to the final list, involved construction of a long tunnel under Queen Anne Hill all the way from downtown to the ship canal. Other options also included greater lengths of tunnelling, but now there appears only the possibility of a ship canal crossing in this corridor.

Bruce Gray for Sound Transit told TunnelTalk: “Staff are investigating the early details of all the projects over the next several months and by the end of the year will come back to the board with cost ranges, ridership, potential impacts and slightly more detailed alignment options for all of them.”

He added: “All of the projects will essentially be put into ‘project templates’ that lay all of this out. The Draft Project List is therefore like a menu of options for the Board to pick and choose from as they move forward putting together a ballot measure for vote next November.”

Fig 2. Ballard to Downtown Seattle light rail options

Fig 3. Ballard study area in relation to existing LRT

Regarding funding, Gray said: “In summer 2015 the Washington State Legislature and Governor granted Sound Transit authority to ask regional voters to approve new local revenue sources that within 15 years can generate up to $15 billion in funding for mass transit expansions. The Sound Transit Board will determine how much of that funding authority to propose as it shapes a Sound Transit 3 (ST3) ballot measure for a vote in November 2016. New local tax revenues will be combined with revenues from bonds, federal grants, existing taxes, fares and other sources to pay for ST3.”

The timetable in the run-up to the ballot is as follows:

• Early 2016 – project templates completed, followed by a round of public consultation to measure public priorities.
• Late Spring 2016 – Board proposes draft ballot measure for public comment.
• Summer 2016 – Board adopts a final ballot measure.
• November 2016 – Public votes on ST3.

The next major Sound Transit project to be carried out in Seattle – as part of the 2011 ST2 ballot – is the East Link connection across Lake Washington to Bellevue. Procurement for the 1,985ft SEM/NATM tunnel under Downtown Bellevue is currently under way and early utility relocations are already taking place ahead of a 2016 construction start.