High temperatures triggered a warning light in the giant Highway 99 drill this week, causing Seattle Tunnel Partners to stop mining again as a precaution.
By Mike Lindblom, January 31, 2014
After spending weeks searching for what might be blocking the Highway
99 tunneling machine, officials say there’s another problem: Bertha is
Adding to the trouble, project managers say they don’t know why.
High temperatures near the machine’s cutting face prompted
contractors to stop mining after the drill advanced a total of 4 feet in
test runs Tuesday and Wednesday. And that ended Bertha’s attempt to
resume mining after an eight-week layoff.
A warning light was triggered in the control room, Todd
Trepanier, tunnel-project administrator for the state Department of
Transportation (DOT), said Friday.
Outside experts will confer with the state and tunnel contractors over the next week to figure out what to do next.
This unexplained stoppage is a setback for the world’s widest
single-bore tunnel. Since its July 30 start, the machine has mined just
1,023 feet of the 9,270-foot route from Sodo to South Lake Union.
A similar temperature spike occurred in early December, and the rate
of dirt removal plummeted. Bertha advanced only 4.4 feet in three hours
just before operators shut it down Dec. 6.
It took weeks for Seattle Tunnel Partners (STP) to pump away enough
groundwater to safely allow an 11-day inspection of the front end, which
found a concrete chunk and some steel pieces from a pipe Bertha struck
Dec. 3, but no major obstacles.
With steel pieces out of the way, the continued overheating suggests a
deeper challenge than, say, taking a fork out of the kitchen
“Although their (STP’s) investigations to date have provided a great
deal of information, we will not be able to definitively identify the
issue or issues facing the machine until tunneling experts complete
their review,” DOT announced Friday.
Trepanier said he still has confidence in the STP construction team,
led by Dragados of Spain, Tutor-Perini of California and engineering
firm HNTB based in Kansas City, Mo., as well as the $80 million Hitachi
“There’s a lot of complexity with the machine, a lot of complexity
with the mining,” Trepanier said. “We’ve had a lot of conversations
with STP about this, and the first thing that they like to tell us,
particularly the side that has experience with tunneling, is this
should not be alarming. ... When you’re using TBM (tunnel-boring)
machines ... issues like this occur throughout the drive.”
Bertha restarted Tuesday and drilled a planned 2 feet, as an experiment after the long outage.
The 2 feet is significant because it allowed workers in back to
fasten the 149th of the tunnel’s 6½ -foot-wide concrete rings that will
form the highway tube. With the ring in place, STP could then spray
concrete grout into the 7-inch space between the ring and the soil, and
troubleshoot the grout jets and other components. (The 571
3-foot-diameter rotary cutting face is necessarily wider than the tunnel
being assembled behind it.)
Temperatures near the cutter reached 140 degrees, at least 1½ times the standard level, DOT managers said.
The contractors made several adjustments, trying to reduce friction
and heat, then mined another 2 feet on Wednesday. Temperatures spiked
again. The sensors are in the mixing chamber, where soil falls through
the spinning face and enters the conveyor system to exit the back of the
STP hasn’t noted any extreme heat or damage in the cutter’s
drive-shaft motor or bearings, according to Trepanier. STP has been
referring questions this week to the state.
Trepanier said the first 1,500 feet between Sodo and the Alaskan Way
Viaduct are a break-in phase, and interruptions are expected.
Colin Lawrence, a New York-based tunneling veteran leading the new
DOT technical team, said in a message it would be unprofessional for
him to discuss the analysis until it’s done.
The project’s financial risk-review team has also reconvened, but
chairwoman Patricia Galloway, of Cle Elum, Kittitas County, declined to
comment this week.
The $2 billion tunnel budget currently includes $120 million in
contingency funds. Trepanier said Friday he won’t speculate about costs
of delays, or how much money STP might seek in claims or lawsuits.