(5:12 PM UPDATE: Just added archived video of meeting – briefing starts about 1 hour, 9 minutes in)
10:38 AM: Click the “play” button to watch, live, as the City Council gets briefed on the Highway 99 tunnel project. Today’s big focus – as previewed in our morning traffic/transportation-news watch – is on how much settling is happening with the Alaskan Way Viaduct and vicinity. The briefing is accompanied by a sheaf of technical information, from the state and the city, which has done its own analysis (and has already issued a news release declaring that the AWV is safe to use). More to come – we’re adding toplines below, as this continues.
SETTLING:
*WSDOT project lead Todd Trepanier reiterates that the Viaduct is safe and that if any information indicated it weren’t, they would shut it down ASAP. But, he later says, data underscores that “this structure needs to be replaced.”
*Daily “automatic surveys” are “recording information all the time”
*So what would trigger a declaration of “this is unsafe”? Councilmember Bruce Harrell asked. Trepanier insisted there is no numerical answer to that, no “x” cracks or “x” inches, but that they keep monitoring and if something looks close to a trigger, they fix it. “It’s complex,” he insists. OK, says Councilmember Mike O’Brien, but “what are they comparing it to?” No numerical answer results. Trepanier mentions “demand and capacity.”
*WSDOT briefer Dave Sowers goes through the slide deck we’ve added below. Says that as long as a specific building, specific water line, etc., settles at same overall rate, it’s OK. Discussion also underscores that multiple entities are monitoring multiple points and not always finding exactly the same thing in (nearly the) same place; Sowers says they’re not yet sure why.
*March 28th inspection for which the Viaduct was closed: WSDOT says quarter-to-half inch of settlement at monitoring spots in Seneca Street vicinity, since last October. CM Sally Bagshaw asks why that area, since not near tunnel pit; WSDOT says they haven’t figured it out yet – it’s not the area where they’ve had settling near Seneca in the past. “Bent 76” (monitoring point) is where some cracks showed movement, they add, and new gauges have been installed. CM O’Brien asks, is the deterioration getting to any certain point such as, the Viaduct could have survived an X quake a month ago but not now? WSDOT’s very technical answer does not hit a certain magnitude but does mention that despite the “large cracks” they believe it would be OK in a “108-year event” quake.
*Water main on Western in Pioneer Square to be replaced ASAP – design 90% done – will take about 8 weeks
*City’s technical analysis (second slide deck below): Bottom line, the city wants another analysis before tunneling resumes, since some parts of the Viaduct have already hit the inch-or-so of settling that it was expected to be able to withstand. They also would like to know what magnitude of quake the Viaduct is expected to be able to handle, currently, and whether more strengthening might be in order. Are we approaching a point at which the Viaduct would have to be closed? Councilmember Tom Rasmussen asks. Not necessarily, says SDOT.
SLIDE DECKS:
*Here’s the WSDOT presentation:
*Here’s the city’s technical-analysis presentation:
*Here’s the Seattle Public Utilities presentation (including the water-main-replacement plan):
OTHER PROJECT-RELATED POINTS:
*Seattle Tunnel Partners is making progress on machine-repairing project, says WSDOT, but “still too soon” to set or guess at dates for resumption of tunneling. Won’t be the “budget-breaking project” (some have feared), Trepanier says
*No rescheduling yet for the sign-related work that WAS going to shut down 99 lanes north of the Battery Street Tunnel for a while
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