STP Prepares to Re-assemble SR 99 TBM

Seattle Tunnel Partners (STP) has begun preparing for its next big milestone: Lowering the repaired front end of the SR 99 tunneling machine back into the access pit.

Much of the repair and reassembly work is now complete. STP is awaiting the arrival of rollers and cages, parts of the machine’s new main bearing. STP chose to remanufacture some parts because of tight tolerances – measured in millimeters – that need to be met as the machine is reassembled. STP indicated the lowering of pieces into the pit will now occur two weeks later than the date shown on STP’s most recent schedule. STP has a plan in place to resume tunneling in late November as scheduled. The contractor’s monthly schedules are posted online.

Crews from Mammoet, the firm that built and operates the Modular Lift Tower, will begin running tests of the crane as soon as next week. Once the MLT and the machine are ready, Mammoet will use the crane to reassemble the machine’s front end at the surface. This will set the stage for the big lift into the pit, which will be similar to the retrieval lift that occurred in March.

The TBM – Bertha – launched in July 2013 and was halted in December 2013 after measuring increased temperatures in the tunneling machine. While investigating the cause of the high temperatures, STP discovered damage to the machine’s seal system and contamination within the main bearing.  About 1,000 ft of the two-mile drive has been completed.