Extension of the University Link tunnels to expand Sound Transit’s light rail system in Seattle, US is fully underway with launch of the second tunnel boring machine (TBM).
Main contractor JCM North Link announced the launch of the Robbins earth pressure balance TBM this week to drive the second of the twin 5.8km tunnels. The first TBM – a Hitachi Zosen TMB – was launched in summer 2014.
The light rail extension will link the North Link district in the north with Roosevelt station near the University of Washington campus in the south. The route is expected to be operational by 2021 and the overall project is aimed at relieving pressure on surface transport systems.
The twin 6.65m internal diameter tunnels will be bored through glacial tills and sands.
According to JCM, both TBMs are refurbished machines and were specially selected to deal with the ground conditions and to minimise noise and vibration impact on the university campus.