Rising Costs and Delays in Seattle Area Wastewater Plant and Tunnels

Seattle’s Pier 57 will soon be home to a 175-foot tall Ferris wheel with 41 air-conditioned gondolas. The foundations for this soon-to-be-landmark consist of 150-ft long, 30-36" steel pipe piles driven through glacial till. The […]

WSDOT released an update on February 7 with some conclusions regarding the blockage that has stopped the Alaska Way Viaduct Tunnel Boring Machine, Bertha’s progress since December 6. Now they don’t think it was necessarily the well casing after all.

They cite two factors that contributed to the blockage. First, the cutterhead was clogged with material. You can see an cool short video of a worker unclogging the cutterhead. Not terribly dramatic, but still cool. The second factor was increased temperatures inside the equipment. STP discovered damage to a seal that protects the machine’s main bearing. They are still determining how the repairs will be done.

If you want to follow the chronology of this issue, read below for summaries and links to previous updates from WSDOT. And Check out the videos too! [Source: WSDOT]

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From ENR:

In the mountains of Peru a tunnel-boring machine named “Pacha Mama” is grinding through the heart of the Andes under rock as deep as 6,890 ft. It is carving away at a 20.2-kilometer-long tunnel through the South American Continental Divide to deliver water to arid coastal farmland.

This is a really interesting project, known as the Los Olmos project, and a nice little article. Normally for a civil tunnel project you drill geotechnical holes beforehand to know what kind of material you’re dealing with. In this case, because of the depth, they don’t have that luxury, so all decisions will be made on the fly. The depth of the tunnel creates some very challenging rock mechanics and logistics problems as well! (Illustration by Odebrecht)

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