Bertha Tunnel Damage Widens, Repairs To Take Longer

Bertha Tunnel Damage Widens, Repairs To Take Longer
Day 7: Osaka Aapo Haapanen / Flickr CC BY 2.0
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Bertha’s tunnel damage is more than what was predicted, informed the Washington Department of Transportation, which said parts of Bertha, Seattle’s tunnel-boring machine will take more time to repair. The digging will not be carried out in August.


“Damage to the machine was more extensive in some areas than anticipated and some minor damage occurred during disassembly,” said WSDOT spokesperson Laura Newborn in a statement. “For example, the outer seals and the steel retainers that hold them in place were destroyed. There was also damage to the cutter drive motor pinions and the main bearing bull gear.”

After installation, the Bertha’s tunnel front end is disassembled and now the damage looks worse than what was assumed. Contractors will not able to resume digging in August as speculated because now the repairs will take a longer time.

The rubber-bearing seals were damaged, and the steel casings around the seals broke apart, sending wreckage into the drive gears. Some teeth of the giant bull gear also suffered cracks.

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Seattle Tunnel Partners and Hitachi are accountable for fixing the world’s biggest tunnel-boring machine, which ceased digging on Dec 6, 2013 after it was overheated. The machine got jammed near Pioneer Square, around 1,083 feet, 9,270-foot from Sodo to South Lake Union.

The highway tunnel was scheduled to start two years earlier but now the schedule is pushed back to early 2017. There has been some aggression in the discussion table regarding the proper testing of the tunnel.

“The frustration level at this table is rising significantly,” said city council member Sally Bagshaw.

“Why was this machine not fully tested?” asked Mike O’Brien.

Contractors said that Bertha hit underground due to leftover steel pipe stand, but the widespread damage suggests the machine may have suffered from intrinsic weaknesses.

“It was poorly understood, going that big in diameter, expecting that seal to work,” said Howard Handewith, a tunnel manager retired from the Robbins Co. “It was just that the structure was too big, and too flexible.”