This morning the Council got a briefing on the Alaskan Way Viaduct replacement project, including Bertha’s status and the planning around digging under the viaduct.
Representatives from WSDOT, SDOT, and King County Metro all showed up to deliver their update. They started with a recap of what happened earlier this year: Seattle Tunnel Partners (STP), the contractor on the project, tipped a barge used for hauling dirt away and damaged the pier. Then later that same day, a sinkhole appeared above the tunnel that Bertha had dug. WSDOT took action, and suspended STP for cause. STP’s response was to modify their quality oversight program, and change their oversight management team. Based on those changes, WSODT conditionally lifted the suspension to allow STP to tunnel to “safe haven 3,” a planned maintenance stop. Councilmember O’Brien commented that he was “flabbergasted” that given the size and complexity of the project — and that Bertha is the largest digging machine in the world — STP didn’t have it’s “A team” on the project until now.
That went without a hitch, and STP is now midway through several weeks of maintenance on Bertha before it begins the next stage of tunneling: under the viaduct. The first stage involved inspecting and repairing the front of the cutter head; to do that, they back up Bertha a few feet (which is all it’s capable of backing up, because Bertha installs concrete rings behind it) to create a space. But the space fills up with water, so it needs to be pressurized to force the water out — to 2.4 atmospheres. And that means that all the workers need to go through a pressure chamber to get in and out of the work area. They pressurize, they work for 2 hours, they depressurize in the chamber for another 2 hours, they get their vital signs checked for a while longer to ensure they or ok, and then they can’t do anything for the rest of that day if they are scheduled to work the next day. Yow. As of last Saturday they had completed 99 crew shifts through that entire cycle.
They hope to begin tunneling under the viaduct in the next month. They haven’t worked out the start date yet since the maintenance inspection work isn’t complete (they don’t know how much repair work there will be until they are done inspecting) but will give two weeks notice.
Much has gone into ensuring that nothing bad will happen to the viaduct when they tunnel under it. STP has reinforced the underground foundation with steel micropiles to spread the load, and wrapped sections of the superstructure with carbon fiber to strengthen them. Last month the viaduct’s semi-annual inspection showed no new cracks and no modifications were needed. They have installed additional instrumentation along the viaduct which will detect movement and stress.
But despite all that work, out of an abundance of caution the powers that be have decided to close the viaduct during the dig — approximately two weeks (though cars and pedestrians will still be able to travel underneath it at ground level). Since the viaduct carries 60,000 cars and 30,000 transit riders on a typical weekday, this will obviously be a major disruption to traffic for those two weeks. So WSDOT, SDOT, Metro, Sound Transit and the Port of Seattle are coordinating carefully and have set up a central command center which will run 24×7 to make decisions on traffic operations throughout the region.
SDOT Director Scott Kubly listed several actions his organization will be taking to ease the traffic issues, including:
- activating a new signal timing plan, based upon traffic patterns the last time the viaduct was closed;
- digital messaging signs at 14 locations, plus 7 additional portable signs;
- uniformed police officers at 11 intersections at the AM peak commute time, and at 12 intersections at the PM peak: key traffic choke points.
- eliminating street parking in select locations downtown to ensure that key arterials stay clear;
- three incident response teams will be on duty from 4am to 8:30pm;
- increased water taxi service to Vashon Island and West Seattle, with improved access to the water taxi terminals;
- working with Uber and Lyft to create more capacity in their carpooling programs — though Council President Harrell reminded them that they can’t show preferential treatment to those companies over “legacy” providers such as taxi companies;
- increasing the street closure moratorium on private construction projects to 6-10am (usually it’s 6-9am);
- working with public utilities to minimize the work in right-of-ways down to just emergencies.
- having a traffic signal engineer in the Traffic Operations Center to allow for changes in traffic signals — in real-time, if necessary.
Metro is rerouting twelve bus routes that go downtown: 4 in the south end, and 8 serving West Seattle. In the north end, transit-only lanes will be temporarily added on Lenora and Blanchard. Metro also will add another 22 service runs with 11 buses, in places yet to be determined when they see overflow and/or delays.
The presenters are working hard to get the word out, including through social media. You can check out http://www.99closure.org and get updates on Twitter by following the hashtag #99closure, or you can install the WSDOT app on your mobile phone.
It’s going to be a crazy two weeks, but hopefully the viaduct will still be standing when they are done. WSDOT pointed out that the reason the tunnel project is happening at all is because the Viaduct is old and starting to fail, so some of the extraordinary measures are in the nature of the job. Fair point, but we should all keep our fingers crossed.
UPDATE 4/15/16: WSDOT announced today that the Viaduct closure will begin on April 29th.