[UPDATE: To be clear, ST is not dismissing Sounder ridership. The author is.] One unexpected contention point in the ST3 plan is the precise location of Chinatown Station. The reference alignment places the station under 5th Avenue, steps from the existing station. However, Chinatown business that have already suffered through streetcar construction have no interest in disrupting business access yet again, although in the long run the neighborhood would presumably benefit from a closer station. SDOT thinks a 4th Avenue alignment may fund some work they already do there. Sound Transit, reasonably, is most focused on the easiest and cheapest way to complete the project. As usual, no stakeholder is primarily interested in the convenience of future riders.
This convenience matters: seamless transfers encourage ridership, and thousands of people will be switching between Link lines at this station every day. Indeed, this will happen as early as 2023 when East Link opens, but Sound Transit has already added an unnecessary escalator and flight of stairs (or two slow elevators) to that transfer experience to avoid a minor capital project.
Another consideration is Sounder, though about an order of magnitude smaller in ridership than Link by the time ST3 opens. Amtrak is probably another order of magnitude below that. But what is the right answer for riders? Sound Transit has four concepts for how these transfers might work: under 4th or 5th Avenue, either cut-and-cover or mined.
The 5th Avenue cut-and-cover station (above) creates more disruption for the neighborhood than the mined option, but it drops riders much closer to the surface. Northbound and southbound riders at the new station would be the same distance from the old station, though the lower one would have a longer ride to the surface. Sounder transfers are not a priority in this alignment. ST says the upper platform would be the northbound line, because it “best facilitates northbound-to-northbound transfers between the West Seattle-Everett line and the Ballard-Tacoma line, which is generally expected to be the highest volume transfer during the highly-concentrated AM peak period.”
ST fears that a side-by-side alignment, given the constraints of foundations under 5th, might not have the needed platform capacity.
The mined station (at right) plunges riders about 200 feet below the road, but construction would be less visible on the surface. This is deeper than Beacon Hill and much deeper than UW, implying elevator-only service. This may not be suitable for a high-ridership station. Transferring riders wouldn’t have to go all the way to the surface, although the complexities of emptying half of a crowded elevator are probably worse than simply taking it to the surface.