Paula Wallis, TunnelTalk

Fig 1. East Side CSO alignment

The Kiewit-Bilfinger Berger (KBB) JV has completed the first 21,000ft (6.4km) drive of the Willamette River East Side CSO project in Portland, Oregon.

The 7.7m diameter Herrenknecht Mixshield arrived at the final Port Center Shaft on October 30, 2009 at 7:10pm to complete the north drive. The TBM will now be recovered and transported back to the central Opera Shaft by barge for relaunch in March 2010 for the 8,800ft (2.7km) drive south to the McLoughlin Shaft.

"The project is on schedule and under budget," said Tom Corry, Project Director for KBB. "So the TBM has performed as expected and KBB is happy with the overall performance of the Herrenknecht machine."

Corry said the TBM set its last ring of the North Tunnel (ring 4068) and was at its final position in the bottom of the shaft on October 31 around midnight. The shaft was backfilled with water to allow the Mixshield to breakthrough under pressure. Once dewatered, the TBM will be lifted from the shaft for its transfer back to the central Opera Shaft working site to complete tunneling operations on the $381 million contract.

The TBM started boring its first North Drive in May 2007, and in its 30 months of excavation, achieved a best day of 24 rings or 120ft (36.6m) and a best week of 561ft (171m).

References

Portland CSO closing in on breakthrough - TunnelTalk, Sept 2009
Portland progress - TunnelTalk, Aug 2008