01-40_WC_149_JUL-AUG26_PT - Flipbook - Page 18
The Annacis Water Supply Tunnel project started in 2022 and is expected to be
completed by the end of 2028. It is one of 昀椀ve new regional water supply tunnels
designed by Metro Vancouver to ensure delivery of drinking water in the event of
a major earthquake.
The Annacis Water Supply Tunnel project and its six
counterparts carry a powerful urgency. “A study in the 1990s
demonstrated that our major marine crossings would not
perform well during a major earthquake,” Annacis project
manager Keith Threadkell says. “Not only would these
marine crossings be unable to withstand a one-in-10,000-year
earthquake, they would actually fail in the event of a one-in-475year earthquake.”
Metro Vancouver manages services for 21 member
municipalities, one electoral area, and one treaty First Nation,
and Threadkell confirms its population is projected to increase
from three million to four million by 2050. If a major
earthquake were to occur, much of the region would lose access
to drinking water. “These projects are both for population
demand and for seismic resiliency,” he says.
To achieve the degree of resiliency needed to maintain service
through a powerful earthquake, project planners recognized that
bedrock and soils experience considerably less shift underground
than they do closer to the surface. So, for the Annacis project,
they settled on 50 metres as a suitable yet sufficiently accessible
depth. “The project has been specifically engineered to meet
current seismic design standards, which are more rigorous than
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WATER C AN ADA • JULY/AUGUS T 2026
those used during the design and
construction of the existing marine
crossing,” Threadkell says, describing
years spent reviewing engineering
models in order to design tunnel
structures and plan for density and
thickness of pipe, concrete, and steel
rebar. “It’s all part of the engineering
process and translates to the different
loads and behaviours that the
completed product has to be built
to withstand.” Threadkell adds that
planners also want to ensure new
marine crossings can be isolated for
maintenance and repair should any
damage occur due to seismic activity
or other factors.
With seismic standards (ACI
350.3-06, Seismic Design of LiquidContaining Concrete Structures)
and measures mapped out and
stakeholder engagement and
archeological and environmental
assessment processes completed for
the Annacis tunnel, Metro Vancouver retained Traylor-Aecon
General Partnership as general contractor, and by 2022 crews
were working at the two project shaft sites and breaking
ground on the tunnel’s entry point at the south side of the
Fraser River in Surrey. The sheer size of that shaft, 15 metres
in diameter and reaching 50 metres in depth, is testament to
the dimensions of the 4.7-metre-diameter, 18,145-kilogram
tunnel boring machine it would soon accept. But first things
first. The shaft took nearly two years to build, starting with the
construction of slurry wall ground replacement panels along its
perimeter to allow the bulk excavation of the shaft interior to
proceed.
In 2024, with the entry shaft fully opened and secure, a
specialized team initiated a year-long journey underneath
the Fraser River, complete with a tunnel boring machine,
built in Germany by Herrenknecht, and nicknamed Anna,
after Annacis. “Only a handful of manufacturers are capable
of supplying this type of equipment,” Threadkell says.
“This is very specialized work, so we needed very specialized
equipment.” Anna underwent factory acceptance testing
to determine fitness for service and was shipped up the
Rhine River by barge to a port in northern Germany for
transport across the Atlantic, through the Panama Canal,
and northwards to DP World’s Fraser Surrey Terminal. “It’s
a significant process just to procure one of these machines,”
Threadkell says, adding that a mobile crane helped lower Anna
into the shaft and position it to begin its journey.
WATERCANADA.NE T
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