(The Center Square) – Sound Transit is unlikely to route three future light rail lines through the Downtown Seattle Transit Tunnel as the agency faces a projected $34.5 billion funding shortfall.
The agency examined two alternatives for using the existing tunnel to determine whether costs could be reduced while maintaining operations as the system expands to Seattle’s Ballard and West Seattle neighborhoods, as well as the Cities of Everett, Tacoma, and Redmond.
Under the interline concept, the planned Ballard extension would merge into the existing Downtown Seattle Transit Tunnel, allowing all three lines to share the tunnel. The analysis found this option would require closing the downtown tunnel for potentially years and shutting down 3rd Avenue for up to a year or more, causing widespread disruption to transit and traffic downtown.
The stub-end concept would terminate the Ballard line at the downtown station, requiring passengers to transfer to other lines. While it would avoid shutting down existing light rail service, the option would require construction of a new maintenance facility and additional review, along with substantial permitting and property acquisition risks.
The analysis found that both alternatives would delay the overall project schedule by at least two years and require extensive near-term infrastructure upgrades to the existing downtown Seattle transit tunnel.
Board members voiced opposition to the concepts, citing added delays to completion of the regional light rail “spine.”
However, King County Councilmember Claudia Balducci noted that upgrades to the downtown tunnel will be needed regardless.
“We’re looking at the risk of shutting down service to upgrade the downtown transit tunnel in a scenario where we defer or don’t build a second tunnel – we’re going to have to upgrade that tunnel anyway,” Balducci said during the board meeting on Thursday. “We don’t know when, we don’t know for how much. It’s not planned until the 2040s and it may be needed well before that.”
Preliminary estimates show potential cost savings of up to $4.5 billion for the interlining concept or $4 billion for the stub-end. Both figures are in 2025 dollars and not “year of expenditure” dollars.
In September, Sound Transit was provided with updated cost estimates for eight of its voter-approved Sound Transit 3 capital projects that increased additional costs by approximately $14 billion to $20 billion. This led to a visible divide among King, Pierce and Snohomish County leaders regarding what capital projects the agency should prioritize amid the $34.5 billion shortfall.
Sound Transit board members representing the City of Seattle have pushed for the agency to prioritize the West Seattle and Ballard light rail expansion projects. This includes Seattle Mayor Bruce Harrell who said those two projects will deliver to denser neighborhoods and increase ridership on the Link light rail.
Seattle City Councilmember Dan Strauss, who represents the Ballard neighborhood, argued that Seattle and King County taxpayers have already paid a disproportionate share of the downtown transit infrastructure and should not be expected to do so again without changes to how costs are allocated.
“If the region makes the decision that this second tunnel is needed for regional liability, then the cost-sharing percentage needs to change,” Strauss said. “The region is already using the tunnel that, in 1990, King County taxpayers paid for – we are being asked to shoulder region-wide asset needs while we’re being asked to put our own sub-area priorities on the back burner.”
