Detailed design is underway on the Second Narrows Water Supply Tunnel Project in Vancouver, which will replace existing marine crossings of Burrard Inlet and ensure this infrastructure can withstand a major earthquake.
"Metro Vancouver and the water district is constantly striving to ensure that we have a resilient system that will survive major earthquakes, scour or any kind of natural disaster," said Frank Huber, director of major projects, management systems and utility services with Metro Vancouver.
"Our goal is to provide the equivalent of winter time demand water at any time of the year shortly after a major earthquake. By strengthening this crossing and actually placing it in a tunnel, is one step towards achieving this goal."
Jacobs Associates Canada Corporation was awarded a $9.7 million contract by the board of directors of the Greater Vancouver Water District for consulting engineering services on July 25, 2015. The contract includes detailed design, construction engineering and construction management.
"Going into the detailed design, we know where the shafts are located and where the tunnel is going, but we don't have a design for the support system or a design for the excavation method of the shafts," said Huber. "All of that will be sorted out during this process and then we will develop contract specifications, design drawings and tender documents. So, we are basically getting it ready to go out to tender."
The Second Narrows Water Supply Tunnel consists of deep, vertical shafts located on each side of Burrard Inlet, just east of the Ironworkers Memorial Bridge, which are connected by a five to six metre diameter, 1.1 km long tunnel.
The tunnel will be an integral part of the water transmission system and convey water from the Capilano and Seymour watersheds under Burrard Inlet to the cities of Burnaby and Vancouver. Huber said the detailed design will take about two years and should be completed by early fall 2017. This means the project will go to tender in the fall 2017 and the contract will be awarded at the end of 2017 or early 2018. The total cost of the project, which involves the construction of the tunnels, as well as its chambers and ancillary piping, is about $400 million. The existing Seymour Mains No. 1, 2 and 3, which cross Burrard Inlet between Beach Yard in North Vancouver and Montrose Park in Burnaby, were constructed in 1948, 1954 and 1978 respectively. The mains are buried in relatively shallow trenches and covered with riprap scour protection. A seismic vulnerability assessment study of the existing crossings was conducted by Thurber Engineering Ltd. in 1996-1997. A seismic vulnerability assessment study of Beach Yard facilities was conducted by Trow Consulting Engineers Ltd. in 2002-2004. Both the Beach Yard facilities and the submarine pipeline crossings were found to be vulnerable to damage during even a moderate earthquake. The new watermains will be connected to the existing mains on each side of the inlet through a system of concrete valve chambers. They will provide increased capacity to meet future demand and long term scour protection. A preliminary design of a new tunnel crossing was conducted by Hatch Mott MacDonald and was supported by several sub-consultants including CH2M Hill Inc., EBA Engineering Consultants Ltd. and GeoPentech, Inc. in 2009-2014.
"The preliminary design involved looking at different alignments, both horizontal and vertical, for a water supply tunnel crossing under Burrard Inlet," said Huber. "These are access shafts at both the north side and the south side of the inlet. We then looked at how deep we actually place the tunnel under the harbour and, where we place that is a function of a number of things, including ground conditions and availability of appropriate tunneling equipment for the size of the tunnel."
A conceptual study to design a new crossing of the Burrard Inlet by tunnelling was conducted by Golder Associates Ltd. between 2004 and 2008. The study focused on the shaft location on north side of the inlet and concluded that the preferred shaft location would be within Beach Yard. Metro Vancouver has a program underway to upgrade or replace five marine crossing within its water supply system to survive and provide water immediately after an earthquake. The new Port Mann Water Supply Tunnel is a one kilometre pipeline, which was completed earlier this year. It will deliver water from Coquitlam to municipalities south of the Fraser River.
Top 10 water projects in bidding/construction stage in western Canada
B.C.: Wastewater Treatment Plant: Lions Gate Secondary Wastewater Treatment Plant , corner of 1 St W & Pemberton Ave at McKeen Ave & Philip Ave., North Vancouver$700,000,000
B.C.: Waterway Tunnel: Second Narrows Water Supply Tunnel across Burrard Inlet from
North Vancouver to Burnaby$150,000,000
Alberta: Wastewater Treatment Facility: Mechanical Wastewater Treatment Facility, Lloydminster$50,000,000
Saskatchewan: Natural Gas Power Plant: Independent Power Producer Combine Cycle Gas Turbine Facilit, Swift Current$50,000,000
Saskatchewan: Waste Water Treatment Expansion: Martensville connection to Saskatoon, Saskatoon$50,000,000
Manitoba: Sewage Treatment Plant, Nelson Road,Thompson, Manitoba$36,000,000
B.C. Pumphouse: Sapperton Sewage Pump Station - Replacement, 230 Brunette Ave & Columbia StNew Westminster$30,000,000
B.C. Wastewater Treatment Plant Upgrades: Iona Island WWTP - Grit System Upgrade,
1000 Ferguson Rd., Richmond$23,000,000
Saskatchewan: Wastewater Treatment Plant, White City$20,000,000
Manitoba: Water Treatment Plant: Lake St Martin First Nation, Gypsumville Grahamdale LGD, Manitoba$17,600,000