Page 5 - TunnelTalk Annual Review 2011

Breakthrough ends challenging journey at Niagara
Severe overbreak led to alignment change
The world’s largest hard rock TBM received a hero’s welcome in March 2011, following a long and tortured drive that tested the resolve of all involved. No shortage of dignitaries, media and invited guests were present to witness the massive Robbins TBM’s breakthrough, marking the end of excavation on the 10.2km (6.3 mile) Niagara Tunnel for Ontario Power Generation (OPG).
Ontario Premier Dalton McGuinty, OPG CEO Tom Mitchell, Strabag CEO Dr Hans Peter Haselsteiner, and Robbins CEO Lok Home were among those present at the celebration as well as hundreds of workers.
“It is terrific for a civil engineer like me, having started out on such an ambitious project, to see the excavation come to a successful end,” said Rick Everdell who began his career with OPG’s predecessor, Ontario Hydro, and has remained with the project almost 30 years through its various incarnations, and rising to the position of Project Director for the client. “The project has certainly had its share of setbacks, including an economic downturn and reorganization of the power industry in the late 1990s. That forced the cancellation of an earlier tender process and reduced the project from its original two tunnels plus a new powerhouse, to the single tunnel. Then there were challenging ground conditions once we got into excavation. Still, after four and a half years of tunneling, the TBM is finally at the finish line.”
Strabag won the design-build contract in August 2005. Having successfully completed the previous largest ever hard rock TBM tunnel on the Manapouri
hydroscheme in New Zealand about six years earlier, the Austrian contractor was uniquely experienced. Strabag’s Project Manager in New Zealand, Ernst Gschnitzer, would also take the reins at Niagara. But almost from the start, the excavation was hijacked by extensive overbreak that slowedadvanceratestoacrawl.
Paula Wallis, TunnelTalk Dark days
“The most challenging days were in 2007 when the TBM entered the Queenston Formation before the St David Gorge and at a maximum depth of 140m (459ft),” said Everdell. “Significant overbreak, meter after meter, essentially blew out the schedule.”
John Tait, Project Manager for Hatch
Tunnel by the numbers
Tunnel
10.2km long (6.3 miles)
TBM
14.4m diameter TBM (47.2ft)
Excavated material
1.7 million m3 (5.6 million ft3)
Concrete for liner
400,000m3 (1.3 million ft3)
Tunnel capacity
500m3 (1,640ft3) of water per second
Power generation
1.6 billion kilowatt hours annually
Who’s who
Client
Ontario Power Generation (OPG)
Construction Management
Hatch Mott MacDonald (USA)
Contractor
Strabag (Austria)
Associated Companies
Tunnel Designers
ILF (Austria) and Morrison Hershfield (Canada)
TBM supplier
Robbins (USA)
TBM trailing gear
Rowa (Switzerland)
Concrete lining operations
Bystag (Germany)
Continuous conveyor system
H+E Logistics (Germany)
Ventilation system
Cogemacoustic (France)
Blasting operations
Castonguary Blasting (Canada)
Intake structure
McNally International (Canada)
Grouting gallery at intake site
Dufferin Construction (Canada)
Cofferdams
Bermingham Construction (Canada)
www.TunnelTalk.com TunnelTalk AnnuAl Review 2011
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