by Dale Menchhofer
tl;dr: This post proposes a new option for the Interbay – Ballard segment of the West Seattle – Ballard light rail project that is measurably and significantly better than any of the remaining official options. The major components are (1) an aerial bridge over the BNSF rail yard, (2) an optional station at Fisherman’s Terminal, (3) a shorter tunnel under Salmon Bay, and (4) a station at 20th Ave NW and NW Market St.
This option has the highest possible value—retaining the high quality of a tunnel, but with significantly higher ridership, and at a competitive cost. In fact, it has a lower capital cost per rider than any of the official options. It has opportunities to turn Port of Seattle and BNSF into 3rd party funding sources, instead of potential adversaries. In spite of its superior characteristics, the only hope it has of becoming the preferred alignment is if enough of you support it in ‘scoping’ comments submitted to Sound Transit. Find handy links to do that at the end of the post.
Intro: why this option is optimal
The best possible ridership puts the station location in the center of the urban village, at 20th Avenue and Market Street. This location is closest to all of the current density, and closest to potential future development.
This option uses the shortest tunnel possible for crossing the ship canal of any practical location. It is about 10-12 % shorter than the 14th or 15th Avenue tunnel options. It is 28% shorter than the “BNSF West/20th Tunnel” option rejected in Level 1 scoping. The shorter the tunnel, the less costly the option. The limiting factors preventing the tunnel from being even shorter are (1) a maximum 5% grade and (2) allowance of 25 feet between the top of the tunnel and the bottom of the ship canal.
In order to reach the shortest possible tunnel, it is necessary to bridge over the BNSF rail yard. I acknowledge that would generally be unwise, but in a later section, I explain why this route is different; why it is uniquely feasible.
There is no practical route using a high fixed bridge to reach a station on 20th Avenue, because of impacts on the legally protected Ballard Landmark District. A tunnel is the only way to do it that does not sacrifice quality.
This option has two additional advantages. It has a net reduction in properties taken, thereby reducing cost further. By eliminating a curve, the Interbay station can actually be at Dravus Street, a better location.[Read more…]