This month, Sound Transit is hosting a series of three open houses, providing information about the progress of the North Link project, which will extend Link Light Rail from the University Link terminus near Husky Stadium to Northgate TC. Because the designs of the three stations are at different stages, the prior open house at Roosevelt and the upcoming Brooklyn open house are primarily intended for neighboring residents and businesses, providing information about construction impacts and ST’s mitigation plans; whereas last Wednesday’s meeting was a presentation of ST’s 30% design for the Northgate station and tunnel portal.
STB covered the Northgate 15% design open house in May, and I’d suggest that readers who aren’t already familiar with the Northgate station design should start reading there, as in this post I’ll only cover information that’s new or different since then. I also recommend the slides from the open house, along with the other material available from the North Link document library.
The biggest change is the potential relocation of the north portal from 85th St to 94th St. Long-time followers of the North Link project will recall that the original project called for a bored tunnel to 75th, a cut’n’cover tunnel to 85th, then retained cut to 94th St before transitioning to elevated. By 15% design, the cut’n’cover section had been scrapped in favor of a longer bore, which reduced costs and dramatically reduced construction impacts. The additional extension of the bore to 94th is roughly budget-neutral, but further reduces the duration and extent of ST’s construction impact on the neighborhood. The additional cost of the longer tunnel will be offset by less work on the surface, and in streamlining construction activity.
The only other significant engineering change is in relocating the entire elevated station 27′ to the west of the previously-planned location, which helps optimize track curvature in the southern approach, and provides more contiguous space for the desired redevelopment of King County Metro’s Northgate TC property. Not much seems to have changed with respect to Metro’s plans for bus integration or TOD at this facility; similarly, a pedestrian bridge across I-5 to North Seattle Community College remains widely-desired and completely unfunded, but ST’s station will be designed to accommodate such a bridge should it ever be built.
The station is starting to come together architecturally, in particular the roof design. Primary attributes the architect desires for this station are protection from the elements, good natural light, insulation from freeway noise, landmark prominence, and low life-cycle cost. The somewhat-surprising (to me) result arising from this is a platform design with glass surroundings, and a “tensile roof” — essentially a very thick, tough, semitransparent multilayer canvas pulled taut over metal supports. Denver Airport is perhaps the best-known large-scale use of this type of design in a transport facility.
In two possible design alternatives, the supports could be arranged either as a series of curved horizontal ribs, or several vertical poles, the latter creating a marquee-like appearance from the inside. According to the architect, these roofs actually last longer on average than a conventional roof (30 versus 20 years), leading to lower total cost over the 100-year design life of this station; they are also extremely quick to construct. One possibly-desirable design element that’s not yet in the plan is to have “NORTHGATE” written in illuminated block letters on the west side of the station, to further enhance its prominence.
Out of the presentation and Q&A, only one potentially controversial issue emerged: replacement parking. During the construction process, ST will displace much of the surface park & ride capacity at Northgate (both on the WSDOT lot west of 1st Ave, and surrounding the current transit center). P&R capacity at Northgate is nearly exhausted, and it’s unclear whether it would be possible to replace that capacity by leasing more space in the adjacent parking lots, or by providing more bus service to remote lots.
In the absence of other workable alternatives, the possibility exists that ST may construct a parking structure in the area to replace that P&R capacity. Building a parking structure in the heart of an area slated for high-density urban redevelopment adjacent to the region’s only high-capacity transit system strikes me — and, I suspect, most readers — as the height of madness. Sound Transit is soliciting ideas for solving the replacement P&R capacity problem, and if you have any thoughts on the matter, I suggest you send them to the community outreach contact for Northgate, Ellen Blair.