Toronto Ontario Line 3 | Metrolinx

hawc said:
China would to the whole thing in one night with 10,000 workers. I've seen the YouTube videos.
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Well, to be fair, concrete doesn’t cure overnight. The pilings needed to support that widened center pillar might have been extensive. The work, even if expedited, probably amounted to a couple months of lane closures and an overnight total closure or two.
If you look at the money that was spent to shorten the 2-lane restrictions on the Gardiner for the past couple of years… I bet any added cost incurred to build the pretty new bridge would have been seen as affordable and necessary. Imagine the reaction if, after finally relieving that constriction, the city announced a new one here.
I can live with whatever the incremental bill turns out to be.

- Paul
 
urbanclient said:
Let's be real here, for many other 𝖼̶𝗈̶𝗎̶𝗇̶𝗍̶𝗋̶𝗂̶𝖾̶𝗌̶ organizations, a rinkydink 120 metre slab bridge over a highway and a small river would not require a few months period. Much less a few months of lane closures.
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anything is possible. it just depends on how much money youre willing to dump into it.

CapitalSeven said:
As far as I can tell the new showy arch spans the parkway and river all in one go. The old railway bridge doesn't need an arch because it's a series of spans.
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Isnt the Don valley bridge an even longer span between piers? no fancy arches there as well... there are many ways to skin a cat when it comes to bridges. this is simply a case of the original bridges being utilitarian and current trend of needing to make everything a work of art (aka blowing the budget on aesthetics)

 
I read that the reason they went with the bridge they did is because it meant no supports were in the Don River, which is better from a ecological standpoint, possibly including flood protection.

If you look at the photo posted earlier, one of the piers is in the Don River and the new bridge won't have that once the trestle structure is removed.

cplchanb said:
this is simply a case of the original bridges being utilitarian and current trend of needing to make everything a work of art (aka blowing the budget on aesthetics)
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I think we're pretty far from making everything a work of art. The Don Valley Crossing+West Don Crossing and East Harbour Stations look to be very minimal.
 
max said:
There's no reason it HAS to be this way, but minimizing disruption to the parkway is likely a high priority on their list, and so tradeoffs were weighed and this design got picked.
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I'd also assume it would be cheaper to construct - unless a full closure of the DVP would be possible for months.

I'm not sure why a standard arch bridge "is for show". They've been building bridges this way for many years. Here's one that's about a century old in KW. There's (shorter) examples in Toronto as well.

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www.metrolinx.com

The story behind the three bridges of the future Ontario Line

These functional and elegant crossings will transform Toronto’s cityscape.
www.metrolinx.com

“They look very different, but there is a sound reason for that,” said John Potter, senior manager subways sponsor at Metrolinx. “The impulse driving the designs starts with the optimal structural solution for each bridge.”

The Don Valley Crossings​


The future Don Valley Crossing Bridge is a balanced cantilever design that will be about 34 to 38 metres tall at its highest point. The first significant new elevated crossing of the Don Valley since the Leaside Bridge was constructed in 1927, it will carry Ontario Line trains between the Minton Place tunnel portal and Thorncliffe Park.

The resulting designs are impactful and complement their location rather than compete with it. "The valley itself is the feature,” said Potter.


The Lower Don Bridge​

The Lower Don Bridge will have a steel network tied arch structure, which will allow it to clear span over both the Don River and the Don Valley Parkway, meaning that piers won’t have to be introduced either in the river or the parkway.

"Another benefit of this arched bridge design is that it's also quite a beautiful structure that can become a marker of the east side of downtown in much the same way that the Humber Bay Arch Bridge is a visual marker when you're approaching the downtown from the west,” said Potter.

"We also included an aesthetic lighting scheme so that you would see this bridge at night – the form would always be legible to people passing by and looking at it.”

Additionally, the materials and finishes for the Lower Don Bridge were chosen for their longevity and appropriateness for the site. To minimize corrosion and repel dirt, for example, a multi-layered, custom coating will be applied to all steel surfaces.

"The Don Valley Parkway, like all highways, kicks up a lot of salt spray or salt fog in the winter which is extremely corrosive,” said Potter.
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hawc said:
China would to the whole thing in one night with 10,000 workers. I've seen the YouTube videos.
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I wasn't even thinking of China specifically, but I did a cursory search and found examples in Canada and the USA where bridges were built much faster. So I edited it "other organizations".

At a minimum the Lower Don bridge will take ~3 years if counting from 2024. I understand the complexity of the situation, but clearly there are no laws of physics preventing a bridge with equivalent function from being built much faster.

hawc said:
Doesn't Metrolinx have a reputation for the exact opposite? Plane Jane utility?
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Blowing copious amounts of money just to achieve "dystopian" utilitarian results (e.g. Line 5). Dystopian according to some on UT.

Blowing copious amounts of money for aesthetics (mediocre IMO). As if Toronto hasn't seen a modern arch bridge before...

It all makes for little to no difference on the eventual riders of the Ontario Line. Wouldn't you rather the bridge and overall project be completed 2 years earlier?
 
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cplchanb said:
anything is possible. it just depends on how much money youre willing to dump into it.
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AFAIK, when you drag a project on, labour and soft costs can pile up. Not to mention the potential for cascading delays that affect the rest of the project and adjacent infrastructure (Lakeshore East).

Feb 28, 2024: "Starting in early April 2024, construction of the east abutment for the new Lower Don bridge will begin.

[...]

The new Lower Don bridge will span 120m over the Don Valley Parkway; construction of the new bridge will continue through 2028."

Here's hoping it's finished by 2027.

Jan 7, 2025: "Bridge construction began in April 2024, and is expected to be complete in 2027." https://www.toronto.ca/legdocs/mmis/2025/te/bgrd/backgroundfile-251979.pdf
urbanclient said:
At a minimum the Lower Don bridge will take ~3 years if counting from 2024.
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There have been a lot of good answers that help explain why the railway bridge is how it is, but there's one big reason that no one has touched on yet.

It wasn't built like that - but rather has been assembled piecemeal over the last 100 years.

The span over the river is part of this version of the "original" bridge (there was a bridge built in 1856 that was superseded by this one in the early 1900s - a portion of the eastern abutment still exists just over the shoulder and guardrail of the southbound DVP). The section over the DVP was built when the DVP was built in the 1950s. And the newest span was built in the early 2000s as one of the first parts of the Don River work.

Dan
 
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