Note that the depth of the access shaft is 180m -
Falling rock stops work on tunnels
Contractors delay water project after encountering 'weak' granite
Kelly Sinoski, Vancouver Sun
Published: Wednesday, March 05, 2008
NORTH VANCOUVER - Contractors building a $600-million water filtration plant in North Vancouver have stopped work on the twin tunnels for more than a month over fears workers could be struck by falling rock.
The project is already a year behind schedule and work is not expected to resume for at least another two weeks, said Doug Neden, Metro Vancouver's division manager for the project.
"There was some concern over worker safety and the contractor stopped work," he said. "It's all on hold at this point."
Germany-based contractor Bilfinger Bergen advised Metro Vancouver in early January that it was halting work on the $200-million twin tunnels after encountering "weak" granite and other stressors midway into the 7.2-kilometre tunnels.
The decision has led to the temporary layoff of 30 workers, many of whom were brought in from overseas.
It's not known how much it will cost to fix the problem, Neden added, nor how much it will delay the entire project. The project is already a year behind schedule after Bilfinger Bergen experienced difficulties developing the 180-metre deep shaft at the Seymour end and had some breakdowns with its tunnel boring equipment.
The project, known as the Seymour-Capilano filtration project, is now expected to be completed in 2010.
Neden said Metro Vancouver engineers provided a work plan with a series of remedies to Bilfinger Berger in January and was told by the company "it would be difficult to work with that." Another report was issued by Metro Vancouver last week and it is still waiting for a response.
Suggestions included more extensive rock bolting -- securing the weaker rock -- as well as more steel mesh. If the problem persists or gets worse, he said, engineers are suggesting using steel sets, or a steel ring beam, around the diameter of the tunnel.
Bilfinger Berger could not be reached.
Neden said both the company and Metro Vancouver are in touch with WorkSafeBC.
"We're keeping them in the loop because safety is of utmost concern, especially in tunnels where there's potential rockfall," Neden said.
He said experts have been called in and there is no worry the tunnels are at risk of collapse. "There's no danger of [them] collapsing," he said. "It's really more around the details of protecting workers. The contractors are just taking precautions before moving forward."
Vancouver Coun. Tim Stevenson, chair of Metro Vancouver's water committee, also said there are no concerns about the tunnel collapsing. "I haven't heard anything remotely suggesting that," he said. "It's just soft [rock] and chunks are just falling off the side of the walls."
Stevenson said Metro Vancouver was not aware that type of rock was in the tunnel site until it was informed by Bilfinger Berger in January. "This is a problem that wasn't anticipated," he said.
The tunnels are an integral part of the filtration plant, as they will allow water from the Seymour and Capilano reservoirs to be filtered, purified and treated with chlorine at a single treatment plant, located in the Lower Seymour Conservation Reserve at the north end of Lillooet Road.
ksinoski@png.canwest.com
© The Vancouver Sun 2008