Reading the tea leaves of the Sound Transit Board, serving Ballard is a clear priority for Sound Transit 3 (ST3). But the Board evidently favors a Ballard-Downtown line via Interbay (I’ll just refer to this as Interbay henceforth for brevity). Ballard-University District (Ballard Spur) light rail might offer greater benefits and also leave enough money for the Metro 8 Subway. In combination, the Ballard Spur and the Metro 8 Subway will serve Seattle better than the Interbay line on its own.
I made the case for building a Lake Union Loop by completing the Ballard Spur, the Metro 8 Subway, and Ballard-Downtown (via Interbay) light rail. Building those three lines might be too expensive for ST3, especially if the scope isn’t increased beyond 15 or 20 years. Even if we did have enough money, we’d still have to determine the order in which to build the lines. I’d argue the Ballard Spur and the Metro 8 Subway should be first because they are more beneficial than Interbay light rail alone.
The latest study indicates that the elevated Interbay option with a new movable ship canal bridge would cost between $4.4 billion and $4.7 billion while the tunnel option would cost between $5 billion and $5.3 billion. Either option would operate best with a new Downtown transit tunnel, which would add another estimated $2 billion to the total project cost. Meanwhile, Sound Transit has pegged the Ballard-University District line around $3 billion.
Through-routing the Spur?
Metro 8 Subway
One of the biggest things the Interbay alignment brings to the table is a station in Uptown and either Belltown or South Lake Union (perhaps both with a somewhat squiggly alignment). The Metro 8 Subway could do the same thing for less money. The most important stretch connecting Uptown to Madison Street would be about 3 miles. It takes another 0.8 miles to reach Cherry Street and 23rd Avenue closer to the heart of the Central District. Since the length is about the same as the Ballard Spur, the cost should be similar.
However, since I’m gunning for at least 6 stations (two more than in the Ballard Spur study), the price would rise. Underground stations cost an average of $175 million for the University Link project. Sound Transit seems to be estimating higher costs in ST3 studies; although, this may be a function of their over-designed stations with oversized mezzanines. So, let’s add about $400 million to the cost for two more hopefully modestly-designed stations. Thus, it would seem a $3 billion Ballard Spur and a $3.5 billion Metro 8 Subway would still cost about the same as a Ballard-Downtown line with a new transit tunnel.
Given how much these two short lines would improve mobility in Seattle’s densest neighborhoods, it seems a more judicious use of funds than building an Interbay-routed light rail line alone. The Metro 8 Subway hasn’t been officially studied, so it seems that Sound Transit doubts its significance; the regional significance, however, is clear to me.
Long Term Plans
Building the Metro 8 Subway would set the stage for the Ballard-Downtown line since it would take care of one mile of tunnel work and two underground stations. I’d wager that would shave almost a billion dollars off the price tag if Sound Transit was to build the Interbay route later on. Building the Ballard station of the Ballard Spur would also knock off the cost of another underground station ($200 million give or take) on the Interbay light rail budget.
Doug Trumm is publisher of The Urbanist. An Urbanist writer since 2015, he dreams of pedestrianizing streets, blanketing the city in bus lanes, and unleashing a mass timber building spree to end the affordable housing shortage and avert our coming climate catastrophe. He graduated from the Evans School of Public Policy and Governance at the University of Washington in 2019. He lives in East Fremont and loves to explore the city on his bike.