Anvil Crossing

Anvil crossing

Thank you: Robson Stollery

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3 Responses to Anvil Crossing

  1. yvrlutyens says:

    Howe Sound is very deep and with steep sides, so any bridge cannot practically have piers very far off shore. The Confederation Bridge, the Great Belt Bridge and the Oresund Bridge are not reasonable comparisons because they are all built in shallow water. More reasonable examples are the Lions Gate Bridge or the Golden Gate Bridge and even those do not cross bodies of water as deep or steep as in Howe Sound. They have central spans of 473m and 1280m respectively.

    Putting the piers right at the water line, the central spans of bridges to Anvil Island would be 1880m and 1560m. To put this in perspective, the longest span in the world is 1991m on the Akashi Kaikyo Bridge. If built, the Anvil Island spans would be the second and fifth largest spans in the world, just to save about an hour in traveling time.

    If we were willing to build such large bridges, it would make more sense to build directly from Horseshoe Bay to Bowen and then from Bowen to Keats. Both such bridges would have central spans of 2050m making them the largest spans in the world. Needless to say, however worthy a fixed link to the Sunshine Coast would be, I can’t see us building the worlds longest spans to do so.

    A floating bridge would doubtless be cheaper, but floating bridges are difficult to build in water with strong winds and tides and a floating bridge would not allow for ship traffic. To allow ocean-going ships to access Howe Sound, one of the spans would have to be a conventional high bridge or have a unique floating swing section or a floating submerged tunnel. Both solutions would be the world’s first and therefore risky.

    Some have also mooted the idea of a floating submerged tunnel for the whole length of the crossing; however, these tunnel concepts are still just concepts. None have ever been built, and their safety is not certain. Ships sinking is a low probability event, but if a ship sank on the tunnel it would probably mean catastrophic failure and loss of life. Of if the moorings holding the tunnel down broke, part of the tunnel would float toward the surface and potentially cause a rupture and thus catastrophic failure and loss of life.

    All that said, I think that the more realistic option is a road from Gibsons to Squamish. Such a road has already been costed at about one billion. Using a 3% interest rate such a road could be paid for in 30 years with annual tolls totaling $38,000,000. (These calculations also include a 2.18% annual toll increase for inflation and population gain, but they do not include maintenance or toll collection costs.) Current ferry revenues on this route are $26,000,000 per year, so users of the new road would be paying more for a more reliable service but not necessarily faster service. (But with more users, each individual trip might cost the same as a ferry trip.)

    If an alternative were to be investigated, I would suggest a subsea tunnel from Horseshoe Bay to Gibsons via Bowen and Keats Islands. The deepest part of this channel is 250m, so with 50m of cover, such a tunnel would be 300m below sea level. The current deepest road tunnel is the Eiksund Tunnel at 287m deep. That is 7.8km long and was built for 500,000,000 NOK or $80,000,000 CAD. A Sunshine Coast tunnel would be at least three times as long and deeper with mid tunnel stations, so we could expect a much higher price tag. And a tunnel could only be built if geology cooperated. The channel is 250m deep, but if the bottom is just another 50m of muck, the tunnel would have to go deeper still. And if there were fissures through the rock, the water pressure that deep under the ocean could be too great to deal with. So I would suggest that a subsea tunnel be looked at with a billion dollar budget in mind so see whether geology is willing to say yea or nay.

  2. Oddvin says:

    Thank you for a very good letter. I agree with almost everything. You have done excellent research. For the same reasons as you mention, my only choice for a crossing is at Porteau Cove area, where there is the only shallow in Hove Sound. Here any of the three solutions could be used: Tunnel, concrete pipe resting on the bottom, for the lenght of the deep sea lane, and/or a bridge combination. Starting at high elevation on the Sea to Sky side, a relative narrow shipping lane, and a causeway to the Potlatch Creek are.
    This will enable Woodfibre to tie in with a road and tunnel. (From there to Squamish is the difficult part, and crossing the Squamish delta would cost the same as a crossing at Porteau Cove).
    From this Connector the road to Port Mellon would be about 16km. with 3 tunnels and 2 bridges. Once connected the trip from Port Mellon to West Vancouver would be 35 min.
    To expand the deep sea port at PM, rail would be added for this part. The port facility would pay for much of the total cost, and create the jobs and tax base the Sunshine Coast depend on. Very valuable foreshore in Vancouver Harbour could be opened up.
    I expect that the ongoing study will compare alternaties and present us with a Fixed Link we all can live with.

    • yvrlutyens says:

      I looked at a Porteau Cove crossing, and bridge would still be a very complicated endeavour. The water depth is between 50 and 75m, but this is a submerged delta so it is likely that the bottom is unconsolidated muck. This might mean that the piles under the piers might have to go another 25m into the muck to find firmer ground. And to stay on the higher ridge, the bridge would have to be curved and about 5.7km long. With 500m cable stay spans that means ten full spans and two half spans between a total of eleven piers, ten in the water and one on Defence Island. Piers would be around 150m high with 500m spans, so the tallest pier would be 250m from top to bottom of the piles. That is a huge pier, and having the pier extend a total of 100m under the water level might be unprecedented. Most of the piers would still be in 50m of water so a total of 225m with the piles. As a comparison, the tallest building in Vancouver is 200m tall and probably 25m underground for an equivalent structural size. This would be a very expensive bridge.

      I wouldn’t put overly much stock in the the Port of Vancouver’s winging about industrial land. True land is tight in the lower mainland, but this is part of a campaign to get land released from the agricultural land reserve. The three biggest grain terminals, Viterra, Cargill and Richardson all have room to expand their storage facilities if they wanted to, and certainly both Richardson and Viterra could add berths at their facilities. And there is space next to both the Chevron and Shell terminals, right on the rail lines, to build new greenfield terminals if there was the motivation to do so.

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