Bertha may be on hold until summer for complicated repairs

The Seattle Times ^ | 2/10/2014 | Mike Lindblom

[steve86]

Seattle Tunnel Partners says it might repair Bertha’s damaged seals from the front end, which would require a digging deep hole along the waterfront and could delay the Highway 99 replacement project for months.

Workers might have to dig a hole up to 115 feet deep to reach and repair the damaged drive system of tunnel-boring machine Bertha, contractors now say.

Once the pit was dug, the 630-ton cutter head would be detached and lifted using a crane, supported by wide footings as if on duck feet, so it wouldn’t sink into the soft waterfront soils.

Chris Dixon, director for Seattle Tunnel Partners (STP), said Monday his team is weighing “four or five options” for a front-end mission, and coordinating the use of waterfront surface space with the city’s nearby Elliott Bay Seawall project.

[...]

The $80 million tunnel machine has damage to the seals that lubricate and protect the $5 million main bearing. This bearing enables the ring-shaped drive shaft to turn the cutter, at about one rotation per minute.

Sand was found in the seal grease, and high temperatures have occurred in the main bearing, according to WSDOT interviews and quality-inspection records.

[21twelve]

They knew that well-casing was there - although they may not have had the proper cutting heads installed at the time. But I guess that is pretty common do just drill through them. Some towns are filled with old oil and gas wells. (This one was a relatively small water well done to test the geology for the tunnel).

They had the over heating problem from very early on (before they hit the casing) - so I think there might be a bigger problem. This is the largest tunnel machine ever built. Although one would hope they did some test tunnels before they shipped it - but I doubt it.

[dynachrome]

5 years from now there will be a rusting hulk in a pit.