NE 130th station advances
Preliminary design of NE 130th station (image: Sound Transit)Sound Transit's System Expansion Committee unanimously approved a motion on Thursday to advance work on a Link station at NE 130th. If adopted by the full Board later this month, as seems likely, Sound Transit will proceed with design work and the first of the construction required to avoid serious disruptions to riders if the station were built entirely after Lynnwood Link has opened.
The motion defers to next year a second decision: whether to continue toward an early partial build or early full build. The early partial build would construct enough of the station to avoid an extended window of single-tracking trains through the construction zone after 2024, but would open the station for service much later. The early full build would complete the station so it could open in 2025 soon after the rest of the line.
As we reported last month, the station construction can be thought of as three "packages". Absent any Board action, the ST3 schedule is to proceed with the Lynnwood Link guideway and add the station platform on a separate foundation later. The first package for an integrated design builds the structural elements for both the station and guideway on a single foundation. Because Lynnwood Link construction is already advancing, this decision was urgent. The committee recommended proceeding with the integrated support structures, keeping open options for an early station opening.
The motion defers the less urgent decision on construction packages two and three until after the completion of design in the second quarter of 2021. With a finalized design and firmer financial analysis, the Board will be better placed to decide whether to build package 2 alone (the platform and canopy), or also package 3 (the plaza and finishes to the station). Package 2 alone is enough to avoid most impacts to riders on trains passing through the area, but package 3 is also needed if the station is to open by 2025.
The adopted motion (which differs from an earlier document online) reads:
Advance progressively: Advance the schedule for completing final design and complete construction of the first construction package for an integrated station (station foundation and structural support). In Q2 2021 after final design is complete, staff would return with all financial, operational and construction information necessary so the Board can determine whether to authorize the second or both the second and third construction packages.
Opening the station earlier reduces the capital cost, mostly by simplifying the structure and construction mobilization. However, suburban board members have been concerned about debt implications, and the consequent impacts to other projects down the queue. At the January meeting, staff presented the provocative estimate of $51 million in added debt service cost, more than offsetting the $30 million capital cost reduction of an early opening.
As explained in last month's piece, the accounting expense is the wrong metric to focus on. What really matters for other projects is whether construction at NE 130th would push Sound Transit's borrowing close to the statutory cap. (Their debt may not exceed 1.5% of the assessed value of property within the RTA). Last month, this blog wrote it was "unlikely the ST3 schedule of late 2020s construction has any advantage in avoiding the debt cap vs a less expensive construction in the early 2020s. Either schedule places the outlays before the most critical window for the debt cap, and the early opening schedule reduces the total capital outlays."
Slide from Thursday's meeting highlighting the tiny impact to Sound Transit debt of an early full build (image: screenshot from Sound Transit livestream)Yesterday, we learned that the effect of an early opening on the level of debt would be only $6 million at the critical pinch point in 2032. That's a mere 0.2% of the expected spare debt capacity then. The suburban alarm about debt expenses has been unnecessary, and could have been avoided if the de minimis debt capacity implications had been clearly disclosed earlier.