Work begins on Second Narrows water tunnel

Brent Richter - North Shore News

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Crews work on Metro Vancouver’s Port Mann water tunnel project, one similar to the project now beginning under the Second Narrows. photo supplied, Metro Vancouver

Work is underway, way under. (Or it will be soon).

Metro Vancouver has begun pre-construction on a $430-million, five-metre wide tunnel under the Second Narrows to supply drinking water to much of the Lower Mainland.

“It’s a pretty honkin’ big pipe,” said Darrell Mussatto, chairman of Metro Vancouver’s utilities committee and Mayor of the City of North Vancouver.

The new tunnel will replace two older mains installed in 1948 and 1978, both of which would be at risk of collapse in even a moderate earthquake, cutting off the fresh water supply to Burnaby, New Westminster and Surrey.

“When they built them back in the day, they weren’t built to the seismic standards that we have today,” Mussato said.

image supplied, Metro Vancouver

Starting this year, crews will be drilling a shaft 68 metres down through Metro’s works yard on Harbour Road in Maplewood. At the bottom, they’ll use a tunnel boring machine to punch through 1.1 kilometres of sedimentary rock and soil under the inlet just to the east of the Ironworkers Memorial Second Narrows Crossing. On the Burnaby side, they’ll grind away 108 metres of rock straight upward from the bottom of the tunnel into Montrose Park.

“It’s significantly deeper than the current water crossing. It will be very deep so even if you did dredging, you won’t get anywhere near it,” Mussatto said.

At its deepest point, the Second Narrows goes about 24 metres down.

Some municipal permits will be required and the public will be consulted on matters like a trucking plan for 60,000 cubic metres of rock and soil being removed. It will likely be sent to a licensed disposal site in the Fraser Valley.

“But they’re really hoping it will be very minimal impact to the community,” Mussatto said.

The Second Narrows tunnel plan was floated in 2005 but detailed designs weren’t completed until 2015. Construction is expected to last until 2022.

Metro recently built a similar tunnel under the Fraser River along the Port Mann Bridge and another project is underway to replace some of the water pipe through Stanley Park.

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