A stalled Metro Vancouver megaproject to drill a new $240-million drinking water tunnel under the Fraser River to serve Surrey and surrounding cities should get back on track by early April.
Work was halted last October when the tunnel boring machine ran into trouble about 800 metres into the planned one-kilometre Port Mann Water Supply Tunnel between Surrey and Coquitlam.
Repairs to the complex machine are nearly complete and tunnel cutting could resume in a few weeks, according to Metro Vancouver major projects director Frank Huber.
It hasn’t been easy to perform repairs to the cutting head 50 metres below the bottom of the river.
Contractors had to first freeze the ground near the bore head to hold back ground water and soil under significant pressure that far down That was done by constructing a platform in the middle of the river from which crews injected liquid nitrogen into the saturated soil.
Then they had to chip large amounts of frozen tunnel muck out of the excavation chamber before a fix could begin.
Once the remaining 200 metres of the tunnel is drilled, the actual 3.5-metre diameter water pipe will be installed to carry Coquitlam reservoir water to residents south of the Fraser.
It’s needed not just because of the region’s rapidly growing population, but also to ensure drinking water isn’t cut off in an earthquake.
River scouring damaged the existing tunnel under the river in 1997 and forced severe water restrictions until it could be repaired.
“When we have a major earthquake, this crossing will survive,” Huber said. “It will allow us to feed water south of the Fraser River.”
The delays have put the project behind schedule – the drilling that began a year ago was supposed to wrap up by late 2014 and project completion has been pushed back into 2016.
But Huber said no cost overruns are expected because of a sizable contingency put in the budget.
“Everyone knows it’s risky business, it’s underground work and things can happen that are unforeseeable.”
Metro officials know well the trouble they can run into drilling water tunnels.
They are finally commissioning long-delayed twin tunnels between the Capilano Reservoir and the new Seymour filtration plant 10 years after the work first began.
That $820-million project first hit trouble when the original tunneling contractor halted work, citing unstable rock. A lawsuit for breach of contract launched by the regional district is still before the courts.