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Rock conditions slowing progress on hydro tunnel
Posted By COREY LAROCQUE
Big Becky was built for size, not for speed.
The world’s largest hard-rock boring machine has gone just one-third the distance it was expected to travel in the first year since work began on a third hydro tunnel under the city of Niagara Falls, officials involved in the Niagara Tunnel Project say.
Progress has been “slower than expected,” Ontario Power Generation said in the company’s quarterly report released recently.
But officials with OPG and Strabag AG, the Austrian company hired to build the $600-million tunnel say the pace is picking up.
“We have a big, dark hole down there and no one can exactly predict what’s going to happen,” said Ernst Gschnitzer, Strabag’s project manager.
Rock conditions in the first kilometre of the tunnel made the first year challenging.
As the tunnel-boring machine, nicknamed Big Becky, drilled away, rocks from the recently-cut tunnel roof fell on top of the back of the $35-million machine as it wormed into the ground.
In some cases, 20-tonne rocks, three metres around fell on the machine, Gschnitzer said. Rough spots in the tunnel will be smoothed when it is lined with concrete.
“We had encountered very difficult rock conditions in the transitions immediately underneath the Niagara sandstone,” Gschnitzer said. “We have mostly overcome that difficult ground.”
As of last week, Big Becky bored 1,350 metres, though Strabag expected to be more than 3,000 metres into the tunnel by now.
At the end of September, Big Becky had excavated 1,028 metres of the tunnel that will connect the Sir Adam Beck generating stations to the upper Niagara River. The entire length of the tunnel will be about 10,400 metres. At 14.4 metres in diameter, the tunnel is as wide as a school bus is long.
Strabag originally set the fall of 2009 as its target to complete the project, but Gschnitzer said it will “most likely” miss that. Ontario Power Generation’s board of directors approved a completion date of June 2010, a date Strabag said it can meet, Gschnitzer said. “I am confident we can keep the date of 2010. I am confident we can stay within OPG’s budget,” he said.
For Ontario Power Generation, the Crown corporation that owns the province’s generating stations, there is “considerable uncertainty” about the schedule until the tunnel-boring machine gets past the St. Davids gorge area, according to OPG’s third quarter report. The company plans to revisit the schedule issue once the machine gets past that critical point, the report states.
As the owner of the province’s public generators, Ontario Power Generation keeps a close eye on the project, but day-to-day work on the tunnel is Strabag’s responsibility.
“While they weren’t doing as much drilling as they hoped for during that quarter, there are a lot of quarters left,” said OPG spokesman John Earl.
Ontario taxpayers are protected from cost overruns because OPG gave Strabag a design-build contract. That makes it the contractor’s responsibility to complete the project within a budget and schedule set by OPG, Earl said.
Neither OPG nor Strabag would talk about the terms of their contract. But Gschnitzer said the “heavy penalties” for finishing late or over-budget are a “strong incentive” for the company.
When work started in September 2006, company officials estimated the machine would advance an average of about 15 metres a day. More than 430 days have already passed, making Big Becky’s pace closer to three metres a day.
That has improved even in the past week when they had a 70-metre day, Gschnitzer said.
Big Becky started digging at a point just west of the Sir Adam Beck generating stations on the city’s north end.
It will dig a tunnel under Stanley Avenue and connect to an intake near the Rapidsview area along the Niagara Parkway.
Diverting more water from the Niagara River to the Beck generators will allow Ontario Power Generation to add enough new electricity to power 160,000 homes, OPG says.
clarocque@nfreview.com
Article ID# 785035
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“When work started in September 2006, company officials estimated the machine would advance an average of about 15 metres a day. More than 430 days have already passed, making Big Becky’s pace closer to three metres a day.”
WHO IS PAYING FOR THRE INCOMPETENCE OF OPG AND the brilliant engineers that proposed this farce ??
Comment by kk — June 21, 2009 @ 6:51 pm