In the past two decades the British
Columbia Ministry of Transportation has received a number of suggestions
regarding a potential link between Vancouver Island and our province’s
Lower Mainland. Although these ideas present major challenges, which
include engineering, environmental, socio-economic and financial
factors, it is possible that these problems may be overcome as new
technologies become available and innovative thinking provides new
solutions. The Province will continue to watch for new options as
they become available.
The 1980s saw a number of studies into
the fixed-link concept. They included:
These were initial studies only. At
this time, no comprehensive engineering studies have been done to confirm the technical feasibility of a fixed link.
The studies identified a number of
potential crossing locations, connecting the Lower Mainland to the
Nanaimo or Duncan areas of Vancouver Island.
The Georgia Strait area is vulnerable
to seismic activity. There were 13 major earthquakes in this area
between 1909 and the beginning of 2002. There were also hundreds
of smaller quakes measuring under 4.6 on the Richter scale in the
same time period. Seismic activity is an important concern; many
structures have collapsed when piers moved during an earthquake due to pier movement.
 |
 |
(Above) Thirteen major earthquakes have occurred since 1909. Hundreds of smaller quakes (magnituded <4.6) are not shown on this map. |
(Above) Showa Bridge collapsed when piers moved during 1964 earthquake in Japan. |
In addition to the possibility of earthquakes, there are other engineering challenges to any fixed link across Georgia Strait. These include:
- length of a crossing could be up to 26 kilometres
- water depths are up to 365 metres
- deep, soft sediments of up to 450 metres on the ocean bed
- potential marine slope instabilities along the eastern side of the Strait could result in future underwater landslides
- extreme wave conditions (4 to 7 metre waves, with 6 metre tides and 2 knot current)
- design wind speed of 115 kmh with gusts up to 180 kmh
- passage of major ships through the area; and
- the need to protect a crossing structure against ship impact (a floating bridge could not withstand the impact of a tanker vessel).
Fixed-link concepts brought forward so far include the following:
- a bored tunnel
- a submerged floating tunnel
- a floating pontoon bridge; and
- a series of cable-stayed bridges supported on floating anchored pier structures.
Each presents challenges.
The technology for boring a tunnel is expensive. Japan’s Seikan Tunnel, which is 54 kilometres in length, cost $7 billion U.S (1988 dollars) to construct and took 25 years to complete. The well-known 50-kilometre Chunnel between Great Britain and the European mainland cost $15 billion U.S. (1994 dollars) to construct and took 11 years to complete. At the Georgia Strait crossing, such construction would have to take place under deep water and deep sediments, creating extreme pressures during construction. The depth of both the water and the sediment would require a tunnel over 50 kilometres in length.
For these reasons, a bored tunnel is not considered a viable option for our province.
| (Below) Examples
of submerged floating tunnels
(Below) Floating Bridge
(Below) Example of Cable-Stayed
Bridge
|
A submerged floating tunnel would also be very expensive. The estimated cost would be two to three times more than a floating bridge. The technology is currently unproven. No submerged floating tunnels exist in the world today.
A submerged floating tunnel to Vancouver Island would require large gravity anchors, which would be complicated given the deep, soft soil on the ocean bed in this area. It would provide better passage for large vessels; however, safety is a critical concern. A submerged floating tunnel would be vulnerable to marine accidents and earthquake damage. A tunnel break would be catastrophic and could result in the loss of many lives. For these reasons, the existing technologies for this type of submerged floating tunnel do not make the option feasible at this time.
The third proposed solution is a floating bridge. Seven floating highway bridges exist worldwide at this time, but none is in water deeper than 100 metres or longer than 3,200 metres. A floating bridge to Vancouver Island would require large gravity and plow-type anchors with anchor cables over 1.2 kilometres long. This extreme length of anchor cable, coupled with the deep soft soil on the ocean bed, poses problems that are not easily solved. Again, as with submerged floating tunnels, safety is a concern. Two floating bridges sank during storms, and the waters between Vancouver Island and the British Columbia mainland are subject to wave forces more extreme than at any of the other existing floating bridge sites. The 2.4 kilometre Hood Canal Bridge, which is also subject to extreme wave conditions, has maximum water depths of only 95 metres with a rock bottom for anchoring. The west half sank in 1979 and was replaced. The east half is currently being replaced for an estimated $471 million U.S.
The other floating bridge option conceptualized a series of cable-stayed bridges, similar to the Alex Fraser Bridge, across the Strait. The tower piers would be supported on floating caissons tethered to the ocean bottom with cables and anchors, similar to an off-shore oil platform. This technology has not yet been applied to a fixed-bridge structure and would need considerable engineering in order to prove its feasibility.
There are no fixed bridges in existence
today that would meet the conditions present in Georgia Strait.
Prince Edward Island’s $1-billion Confederation Bridge is
only 12.9 kilometres long and is set in water 35 metres deep with a rock bottom. In comparison, a fixed
bridge across British Columbia’s Georgia Strait would be
26 kilometres in length and in water up to 365 metres deep.
The Tagus River Bridge in Lisbon has the deepest conventional bridge foundation in existence in water depths of only 79 metres. That is far shallower than what
would be required for a floating bridge between Vancouver Island
and British Columbia’s mainland. Greece’s Rion Antirion
Bridge, which was completed in 2004, faced challenges
quite similar to those in Georgia Strait. It too is in a high seismic
zone and must contend with an ocean bottom consisting of deep,
soft sediments. However, this structure is only 2.8 kilometres
long and sits in waters of only 65 metres. It cost an estimated
$1213 million to complete and each of four main pier structures
cost $146 million.
A fixed bridge across Georgia Strait
would also be subject to snow, ice and fog conditions that could
make driving hazardous.
Any fixed link across Georgia Strait
would pass through or over high use navigation channels. Currently
45,000 vessels pass through these waters each year, including
pleasure craft, commercial vessels and military vessels. A fixed
link would potentially require two channels, each a minimum of
200 metres wide by 65 metres high to accommodate current and future vessel needs.
The cost of building a fixed link
using the technologies available right now could not be borne
by government alone. Any private-sector interest undertaking such a
project would require a return of 12 to 20 per cent. This would
have to be raised through tariffs that would not only cover the
cost of construction, but also annual maintenance and rehabilitation
(estimated at $57 million per year) and insurance over the 100-year
expected service life of the structure. With these considerations
in mind, tariff structures for a fixed link using available
technologies would probably be based as follows:
|
Return Rate
|
Tariff
(One Way) for an
$8-billion project |
Tariff (One
Way) for a
$12-billion project
|
9% (Breakeven) |
$180 |
$260 |
12
% |
$260 |
$380 |
15
% |
$360 |
$525 |
20
% |
$555 |
$800 |
