Quote:
Originally Posted by DKaz
If they bore it all the way that'd be awesome. Except for station pits, no one would ever know that a line was being built. Any idea how much it cost to build the Olympic Village to Waterfront portion of the Canada Line?
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I don't think the TBMing is nessecarily as beneficial as one might initially imagine it to be, for three major reasons:
1) Obviously, there's the cost issue, TBMing is much more expensive, and that money could be better spent elsewhere.
2) TBM's are generally slower than cut and cover (longer construction time).
3) Then the issue of what street the line will travel under comes into play:
- Broadway has a lot of utilities under it, which means you'd need to tunnel very deep to avoid them. They'll still pose a problem when you dig your station boxes. Additionally, you're digging up 100m of Broadway (80m platforms, plus ventelation etc at each end) every kilometer or so; Broadway will be a traffic nightmare even if you dont cut and cover the tunnels.
- 10th Ave is a much narrower street. When you TBM, you have 2 options, 2 small tunnels, or one big one. If you do two smaller tunnels, they'll need some minimum amount of spacing between them so they dont collapse into each other. I'm not sure if 10th Ave can give this (unless you tunnel under buildings on either side, but I'm not sure about what manner (if any) of compensation you'd need to provide if you did that. Alternately, you can use a single big tunnel, but you'll end up excavating twice the amount of dirt as two smaller tunnels: pi*(2r^2), vs. 2*pi*(r^2), which is of course more expensive.
My prefered option would be what I've outlined below. As far as I can tell, its the cheapest and fastest way to do it without causing major traffic headaches and having major resistance from affected buissness (this time they'll be screaming right from the start, now that they've seen what happened on Cambie).
Anyways, here goes:
- Elevated from VCC-Clark, tunnel portal just before Finning stn.
- Underground station at Finning (as per those renderings someone posted back in the summer)
- TBM, with staiton at Main St and Broadway area, until the West side of Cambie (since I imagine they will need to TBM under the Canada Line, there's definately no space above the Canada Line tunnels). I'm assuming that its cheaper to simply keep the TBM running the extra distance rather than stopping it just West of Main and starting again just East of Cambie. Also, I'm assuming cut + cover under Cambie station is basically impossible, although if it was possible, perhaps they could built the Station right under the existing one rather than off to the West, the knockout panel on the EAST side of the Canada Line station could provide a second access point to the M-Line station.
- Otherwise, station on the West side of Cambie and 10th (to integrate with knockout panel on Broadway-City Hall station).
- Cut and cover a stacked tunnel from Cambie to Alma along 10th Avenue, with stacked stations with the platforms on the North side. Since 10th slopes down towards Broadway, you may be able to get away with less excavation than you'd otherwise need. There's no buissnesses along here, so you shouldnt have any bankruptcies. It will be noisy for residents, but hey, you cant make an omelet without cracking a few eggs.
- TBM from Alma to Blanca (to handle the grades just West of Alma, and protect buinessses along the strip just before Blanca. Not sure how they'd dig the station box at Sasamat though, unless they buy up a block of buissnesses and build it there. Otherwise you'd have a traffic/buissness nightmare anyways, and you might as well switch back to cut and cover after the grades sort themselves out.
- At grade along University Blvd as far as you can take it, before elevating or burying in order to inegrate with transit hub at U Blvd and East Mall.
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