September 4 - After a painstaking operation to repair the tunnel boring machine (TBM), Bertha, after damage was discovered to its seals in 2013, Mammoet has successfully lowered the front end of the unit back into the ground in Seattle.

The front end of the machine, which stopped 304 m into its underground operation for the Alaskan Way Viaduct Replacement Tunnel project, was recovered by Mammoet back in March 2015.

The bearing block section of the TBM has been repaired, with the inner and outer bearings replaced by ones with stiffer seals.

In the middle of August 2015, Mammoet lifted the 370-tonne bearing block onto the cutter head for reassembly, before 16 electric motors, each weighing 13 tonnes, were reattached to the machine.

Once the repair work was completed the entire section - weighing around 1,800 tonnes - was rotated and lowered into the 37 m deep access pit using a specially designed and constructed gantry and skid system. It will now be reconnected to the main body of the machine in preparation for the tunnel boring project to recommence.