1 Tunnelling under the Fraser River at 6 bar Design and Construction of the Port Mann Main Water Supply Tunnel Stephanie Fekete McMillen Jacobs Associates Steve Skelhorn McNally Construction Inc. Tim Langmaid Hatch Mott MacDonald Allen Mitchell Metro Vancouver Abstract. The Port Mann Main Water Supply Tunnel project provides a critical water main crossing of the Fraser River for the owner, Greater Vancouver Water District (Metro Vancouver). The project consists of two 60-metre-deep slurry panel shafts and a 1-kilometre-long, 3.5-metre excavated diameter tunnel located near Vancouver, British Columbia, Canada. The initial tunnel lining is a precast steel fiber reinforced segmental lining. The final lining is a 2.1-metre-diameter welded steel pipe. This paper describes the challenges encountered during tunnel construction and the solutions implemented. Key challenges include earth pressure balance tunnelling at up to 6 bar pressure—the highest to date in Canada—a water-crossing without surface access for the majority of the tunnel drive, ground freezing from a river platform for a critical TBM intervention, and boring through cobbles and boulders in dense glacial till. INTRODUCTION Metro Vancouver supplies drinking water to 18 municipalities, one electoral district and one treaty first nation, serving a population of more than 2.4 million residents. Water is collected in three mountainous watersheds to the north of the Greater Vancouver area, in southwestern British Columbia, Canada. To supply the growing demands of Metro Vancouver’s customers, treated water must be conveyed across two significant water bodies: the Burrard Inlet and the Fraser River. The existing Port Mann water main is one of several key links between the watersheds north of Vancouver and the municipalities south of the Fraser River. The Port Mann Main Water Supply Tunnel (PMMWST) is the first of a series of upgrades, to increase capacity, enhance scour protection, and improve seismic resilience. The new tunnel is 3.5 metres (11.5 ft) in diameter and 1 kilometre (0.6 mi) long. When completed, it will contain a new 2.1 metre (7 ft) diameter steel water main that will help ensure the continued, reliable delivery of drinking water to these municipalities, and will more than double the capacity of the existing 1.2 metre diameter main. Construction of the PMMWST began in the spring of 2011, with ground being broken for the construction of the south shaft. A significant milestone was achieved on June 26, 2015, when “Squirrel,”
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Tunnelling under the Fraser River at 6 bar...Tunnelling under the Fraser River at 6 bar Design and Construction of the Port Mann Main Water Supply Tunnel ... The initial tunnel lining
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Tunnelling under the Fraser River at 6 bar Design and Construction of the Port Mann Main Water Supply Tunnel
Stephanie Fekete
McMillen Jacobs Associates
Steve Skelhorn
McNally Construction Inc.
Tim Langmaid
Hatch Mott MacDonald
Allen Mitchell
Metro Vancouver
Abstract. The Port Mann Main Water Supply Tunnel project provides a critical water main crossing of
the Fraser River for the owner, Greater Vancouver Water District (Metro Vancouver). The project
consists of two 60-metre-deep slurry panel shafts and a 1-kilometre-long, 3.5-metre excavated diameter
tunnel located near Vancouver, British Columbia, Canada. The initial tunnel lining is a precast steel fiber
reinforced segmental lining. The final lining is a 2.1-metre-diameter welded steel pipe. This paper
describes the challenges encountered during tunnel construction and the solutions implemented. Key
challenges include earth pressure balance tunnelling at up to 6 bar pressure—the highest to date in
Canada—a water-crossing without surface access for the majority of the tunnel drive, ground freezing
from a river platform for a critical TBM intervention, and boring through cobbles and boulders in dense
glacial till.
INTRODUCTION Metro Vancouver supplies drinking water to 18 municipalities, one electoral district and one treaty first
nation, serving a population of more than 2.4 million residents. Water is collected in three mountainous
watersheds to the north of the Greater Vancouver area, in southwestern British Columbia, Canada. To
supply the growing demands of Metro Vancouver’s customers, treated water must be conveyed across
two significant water bodies: the Burrard Inlet and the Fraser River. The existing Port Mann water main
is one of several key links between the watersheds north of Vancouver and the municipalities south of
the Fraser River. The Port Mann Main Water Supply Tunnel (PMMWST) is the first of a series of
upgrades, to increase capacity, enhance scour protection, and improve seismic resilience. The new
tunnel is 3.5 metres (11.5 ft) in diameter and 1 kilometre (0.6 mi) long. When completed, it will contain
a new 2.1 metre (7 ft) diameter steel water main that will help ensure the continued, reliable delivery of
drinking water to these municipalities, and will more than double the capacity of the existing 1.2 metre
diameter main.
Construction of the PMMWST began in the spring of 2011, with ground being broken for the
construction of the south shaft. A significant milestone was achieved on June 26, 2015, when “Squirrel,”
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an earth pressure balance tunnel boring machine (EPB TBM), completed the final advance of the tunnel
drive. This paper focuses on the tunnel portion of the work and highlights some of the unique challenges
that had to be addressed during design and construction.
Project Team The PMMWST project is being constructed by the McNally Construction Inc. – Aecon Constructors Joint
Venture (MAJV). Construction management is being provided by Hatch Mott MacDonald. The design for
the permanent structures as well as engineering services during construction are provided by the Fraser
River Tunnel Group (FRTG), a team comprising Ausenco, McMillen Jacobs Associates, and Golder
Associates.
Project Overview The tunnel was driven between shafts sunk on either bank of the Fraser River, see Figure 1. The launch
shaft on the south bank in Surrey is 11 metres internal diameter; the reception shaft in Coquitlam has a
5 metre internal diameter. The two 60 metres deep shafts were constructed using unreinforced slurry
diaphragm walls for temporary support. A tremie slab plug was placed before the permanent, cast-in-
place, reinforced concrete liners were installed. At both the North and South sites, a valve chamber was
constructed integral to the shafts to control water flows through the tunnel pipe.
The tunnel is 1 kilometre long with a 3.5 m excavated diameter. The tunnel is located approximately
30 m below the bottom of the Fraser River. The initial tunnel support (precast concrete segments)
provided ground support during mining and steel pipe installation. The final lining consists of a 2.1 m
diameter steel pipe, which will be the final conduit for drinking water. The tunnel is located below the
depth of riverbed scour and is designed to remain functional following a major earthquake. The annulus
around the steel pipe is backfilled with cellular (foamed) concrete.