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.
A new downtown tunnel as part of the prioritized Ballard-Downtown light rail link is accelerated by three years following the final round of consultations over Seattle’s third phase of transit plans (ST3).
The final list of ST3 projects – which will go to ballot later this year – will see the addition of 100km of new light rail and 37 stations. In earlier phases voters have approved construction of the 7km-long all-underground Northgate Link, which is nearing final TBM breakthrough, and the recently opened 5km U-Link between the University of Washington and Downtown. A short tunnel under Bellevue is also under construction as part of the East Link LRT across Lake Washington.
This time around, however, there is only a single underground project – for the Downtown part of the Ballard-Downtown connection. Studies did consider significantly more tunnelling along the corridor – but in the end a bridge solution across the ship canal, and an elevated guideway along 15th Avenue (Fig 2), were favored in the northern section of the alignment.
The total US$54 billion worth of projects will take Seattle’s transit extension program through to 2035, with the new Ballard-Downtown Link moved forward to a 2032 completion. ST3 also supports further studies of the currently preferred underground solution for a planned Ballard-University of Washington link.
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:
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.”
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:
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.