[UPDATE (Adam here): I did a few calculations to put the debate about whether a tunnel through Beacon Hill was necessary to rest. Beacon Hill station is very roughly ~280 ft above sea level, and SODO is ~20 ft. Using ST's design specs of 4% this means that an elevated structure of ~6,500 ft would be needed to climb from SODO up over the hill. Another one of equal length would be needed on the other side as well. Pretty unrealistic isn't it?]
Although I’d obviously like to see Bellevue pay for a Link tunnel under Downtown Bellevue, as someone who isn’t going to pay the very large costs I’m leery of taking a really strong position on it. A common argument, however, is that Seattle is getting a very long tunnel from its downtown to Roosevelt on Sound Transit’s dime, so why not Bellevue? It’s a natural question to ask, but betrays a pretty shallow understanding of the underlying concerns. More after the jump.
First of all, there’s the issue of subarea equity. These projects are actually funded with different pots of money, so on some level Seattle and Shoreline are deciding how to spend their money and the Eastside is deciding how to spend theirs. On the west side of the lake the spending is a bit more concentrated, on the Eastside a bit more spread out. To some extent that’s an inevitable result of the Eastside being fractured into three large cities, rather than a single voice that more or less speaks for the subarea.
There’s also a capacity concern: you cannot run Downtown to Northgate on the surface and support the predicted demand – demand that will come from all over the region. That is simply not the case for East Link, particularly since at-grade segments both east and south of DT Bellevue will forever constrain the frequency at which trains can run.
As for the Beacon Hill tunnel, once you’re committed to serve both jobs in Sodo and people in the Rainier Valley there isn’t any choice but to go up, over, or through Beacon Hill. I’ve never seen a definitive technical document, but I’ve been told that only tunneling was practical for this problem, and that seems plausible enough to me.
Back to the issue at hand, although there’s some impact on travel time, in Bellevue the tunnel vs. surface argument is fundamentally one about traffic disruption. Traffic disruption is undeniably a negative impact of surface lines; it’s a question of whether light rail is worth the disruption or not. It’s not surprising to me that people who think light rail is worthless (e.g., Kemper Freeman) would think not, but I think most people would agree to take the trade.