Central Subway breakthrough
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June 2, 2014: The second of two Robbins EPBMs broke through June 11 to complete its 2.7km drive on the twin tunnels of the Central Subway in San Francisco, USA. The second EPBM is set to breakthrough within days of the first. The Barnard/Impregilo/SA Healy JV saw average progress rates of 50-80ft/day with a best rate of 115ft/day in ground that was better than anticipated. The first TBM completed its drive within 10 months of its launch. The precast concrete lining segments from the Precast Management Company in Las Vegas included an embedded gasket. The owner, San Francisco Municipal Transportation Agency, is well pleased with the tunneling contractor which brought the project in on time and within budget and without any adjustments to either.

References

Closing in on Central Subway breakthroughTunnelTalk, April 2014
Central Subway bids open as first TBM arrives TunnelTalk, April 2013

Snapshot

Central Subway breakthrough

Paula Wallis reporting for TunnelCast
Location: San Francisco
Tunnel details: 2.7km long x 6.27m wide (1.67 miles x 20.5ft), five cross passages, three underground stations, one surface station
Type: Subway
Owner: San Francisco Municipal Transportation Agency (SFMTA)
Tunnel contract value: US$233.6 million
Tunnel contractor: Barnard/Impregilo/SA Healy JV
Stations contract value: US$852 million
Stations contractor: Tutor Perini
EPBM TBM manufacture: Robbins