Danforth Line 2 Scarborough Subway Extension

[denfromoakvillemilton]

If they want a station, it would have to be a cut-and-cover line, so that there would be savings to offset the costs of the added station.
The question I have is, what to do with the 2 West Highland Creek crossings (Trudelle Park and Pringdale Ravine) south of Lawrence. The southerly crossing looks quite shallow, and likely the line would have to go under. The more northerly (Pringdale) crossing seems to be a somewhat deeper valley and it may be possible to build a bridge with subway below - but I suspect that even here you may have to go under.

100% you are going under.

I used to drive along Danforth there to get to work.

The dip is quite small, there is no way the tracks would exceed the floodplain w/o being at grade w/homes on either side.

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The real challenge for the line is the ravine crossing just north of Lawrence.

To cut under that, which is the assumption; based on where the water table sits, you have to be very deep, making the station, rather expensive.

Cutting above was ruled out, I'm not sure that its impossible, but it probably triggers lots of expropriation on the north side of the ravine as the train dives down again.

Was going above discussed in any official way?

I was thinking of raising the profile of McCowan by about 3.0 to 3.5 metres. Add to this the current bridge beams that are likely about 1.0m deep and you would keep the bridge soffit elevation roughly the same. With bridge girders of 4.5m deep, it could easily span twice the current bridge - so passing the Regional Storm should not be a problem.

No



Uh uh.

The current bridge sits very low over the creek.

You might be fine for regional storms; though w/increasing intensity, I don't think I'd want to bet on it.

The area below that bridge floods with some regularity. The ground is routinely saturated. Creekside erosion is a material issue.

The safe plan here would be, at minimum for the 100 year storm.

(which may soon be the 25-year storm, or less)

It wouldn't be impossible to situate the right height, but it would be expensive and challenging, unless you went over-grade. above Lawrence; but that comes with a different set of challenges, and likely no less expense.

This image from a City of Toronto presentation is of the Birkdale Ravine, after the August 2005 storm.

Its just upstream from the McCowan bridge over the Bendale Branch of Highland Creek.

View attachment 189357

ICLR Friday Forum: Reducing flood risk in Toronto (February 2016)

ICLR held a Friday Forum workshop February 19, 2016 entitled 'Reducing flood risk in Toronto', led by David Kellershohn with Toronto Water. Urban flooding cont…

www.slideshare.net

There is insufficient 'wiggle room' for a subway near the height of the existing bridge.

From a higher elevation, it may be do-able, but it would be destructive to greenspace, and costly.

I would only be surmising, but based on the low crossing of the East Don over Leslie, I think the TTC would look to build a fully sealed tunnel-bridge, rather than an open one.

I also imagine they considered it and ruled it out. Keep in mind the depth the tunnel would have to come from in the south, having gone under Highland Creek (different branches) twice before.

They should cut and cover for sure. This should be done as quickly as possible.

I'd suspect doubling the span of the bridge would help.

Maybe it's a similar argument to the Ontario Line crossing of the Lower Don.

If you are using TBM south of Highland, and also North to get into STC - then you would not even think about the idea of having the subway cross above this main branch of the river under the road. If you are using cut-and-cover both north and south, then it's a totally different story.

 

[BurlOak]

Why deviate from the current TBM design, that has the emergency exit near where the north end of the platform would be? (we are talking about Lawrence, right?)

Because the current 1 stop subway design seems incredibly costly and the plan to go under Highland Creek at Lawrence would require a very expensive station.
No doubt that some type of P3, while allowing the Contractor some leeway in construction method, could lead to large savings.

 

[nfitz]

Because the current 1 stop subway design seems incredibly costly and the plan to go under Highland Creek at Lawrence would require a very expensive station.
No doubt that some type of P3, while allowing the Contractor some leeway in construction method, could lead to large savings.

Elevating would lead to savings.

Shallow construction in the flood plain? The station is all on higher ground, and they'd just have to grout around the perimeter to dig down ... or tunnel the station. But if you do cut-and-cover you are digging through the creek - and it's still going to be relatively deep at Lawrence because of the topography. Plus, you have to deal with a lot more utilities. Also, there must be some pretty big sewer collectors around there somewhere ... I don't have a map though ... but something is ringing a bell about Highland Creek.

Would be interesting to see costs ... but I wouldn't necessarily assume that cut-and-cover would be much cheaper and quicker. Or even cheaper or quicker at all!

If you want cheaper and quicker, then escalate it north of Eglinton. And why not ...right-of-way looks wide enough to build columns down the centre of the street, to support an elevated structure.

 

[Rainforest]

If they are tampering with the design anyway, they should revisit the Brimley alignment option.

The Eglinton/Brimpley station won't be possible then (on the curve), but the Lawrence station might come cheaper if the subway runs under Brimley.

 

[OneCity]

If they are tampering with the design anyway, they should revisit the Brimley alignment option.

The Eglinton/Brimpley station won't be possible then (on the curve), but the Lawrence station might come cheaper if the subway runs under Brimley.

I believe the curve starts after Brimley.

Edit: I see you are suggesting a new route up Brimley. I would only consider that if it was the 1 stop as the McCowan stop locations are more central to feed into. While there may be some benefit it would also mean a complete gutting of the existing alignment design work and it still would not point towards Markham/Progress. IMO tha would be the only solid benefit worth changing alignment for, at this stage. Also would be inching too close to GO RER/Smarttrack

 

[Rainforest]

I believe the curve starts after Brimley.

View attachment 189516

Yes, the current design is for tunnel under McCowan, that makes the Brimley & Eglinton station possible.

My question is whether switching to a route under Brimley instead of under McCowan would help build the Lawrence station.

I understand the reluctance to redo the tunnel studies, however if the changes needed to accommodate 1 or 2 extra stations on the existing route are substantial, then there might be no time penalty for flipping to the Brimley route.

 

[OneCity]

Yes, the current design is for tunnel under McCowan, that makes the Brimley & Eglinton station possible.

My question is whether switching to a route under Brimley instead of under McCowan would help build the Lawrence station.

I understand the reluctance to redo the tunnel studies, however if the changes needed to accommodate 1 or 2 extra stations on the existing route are substantial, then there might be no time penalty for flipping to the Brimley route.

Sorry I edited the post once I realized.

See above.

I also love the addition of a Brimley/Danforth area stop and don't see the chaos of starting over worth the long term savings on Lawrence. Its time to fix the design for the missing stops and move forward.

 

[syn]

Elevating would lead to savings.

Shallow construction in the flood plain? The station is all on higher ground, and they'd just have to grout around the perimeter to dig down ... or tunnel the station. But if you do cut-and-cover you are digging through the creek - and it's still going to be relatively deep at Lawrence because of the topography. Plus, you have to deal with a lot more utilities. Also, there must be some pretty big sewer collectors around there somewhere ... I don't have a map though ... but something is ringing a bell about Highland Creek.

Would be interesting to see costs ... but I wouldn't necessarily assume that cut-and-cover would be much cheaper and quicker. Or even cheaper or quicker at all!

If you want cheaper and quicker, then escalate it north of Eglinton. And why not ...right-of-way looks wide enough to build columns down the centre of the street, to support an elevated structure.

The only way this extension makes any sense is if it's entirely above ground.

Digging is too costly.

 

[M II A II R II K]

Nobody suggested putting Old Mill station under its creek, so do the same at Lawrence.

 

[nfitz]

Nobody suggested putting Old Mill station under its creek, so do the same at Lawrence.

The bridge crossing of the Don River near Leslie station is similar. The topography is a bit different here.

If you look at Drawing SSE-G312 on page 103 of Volume 1 of the 2017 TPAP it says the regulatory flood level is 147.87 m AMSL. So if the bottom of your structure, at best at 148 m AMSL (or higher!).

Meanwhile the north edge of Lawrence East at McCowan is about 157 metres dropping. So you've only got 9 metres to play with, assuming you super-elevate a bit north of Lawrence (using the planned river) crossing location just west of McCowan.

It would be tight - but it might be doable - depending how much safety factor you want on the flood stage. They probably they should revisit if they add a station. Will it save money though?

 

[BurlOak]

Nobody suggested putting Old Mill station under its creek, so do the same at Lawrence.

Leslie Station (at Sheppard) is another, an newer, example.

The bridge crossing of the Don River near Leslie station is similar. The topography is a bit different here.

If you look at Drawing SSE-G312 on page 103 of Volume 1 of the 2017 TPAP it says the regulatory flood level is 147.87 m AMSL. So if the bottom of your structure, at best at 148 m AMSL (or higher!).

Meanwhile the north edge of Lawrence East at McCowan is about 157 metres dropping. So you've only got 9 metres to play with, assuming you super-elevate a bit north of Lawrence (using the planned river) crossing location just west of McCowan.

It would be tight - but it might be doable - depending how much safety factor you want on the flood stage. They probably they should revisit if they add a station. Will it save money though?

I thought the Leslie crossing at Don was actually above the Regulatory Flood and created some backwater.
I'd suspect a bridge would be - soffit to top - no more than 6m - likely 5.5m. 0.5m bottom slab (spanning transversely), 4.5m internal box dimension, and 0.250mm top slab. Add another 0.250 mm for crossfall.
It's maybe the elevation at the north (Benleigh Drive) that's more critical. The entrance to the hospital just south of the bridge would have to be reconfigured.

 

[nfitz]

It's maybe the elevation at the north (Benleigh Drive) that's more critical. The entrance to the hospital just south of the bridge would have to be reconfigured.

The elevation there is pretty low - but that's okay, as the current plan has the entire tunnel west of McCowan at this point - so presumably the bridge could be entirely west of McCowan, and a higher elevation than McCowan.

The entrance is indeed an issue. They'd have to change that entrance completely .... perhaps move it further south where the elevation is higher. But that's probably a lesser issue.

 

[BurlOak]

The elevation there is pretty low - but that's okay, as the current plan has the entire tunnel west of McCowan at this point - so presumably the bridge could be entirely west of McCowan, and a higher elevation than McCowan.

The entrance is indeed an issue. They'd have to change that entrance completely .... perhaps move it further south where the elevation is higher. But that's probably a lesser issue.

View attachment 189582

Is there a link to these drawings?

 

[nfitz]

Is there a link to these drawings?

I was hesitant to link it as we've discussed the drawings before, and it's a 150 MB file.

It's the "Environmental Project Report - Volume 1" on the TTC's website for the Line 2 Extension - https://www.ttc.ca/About_the_TTC/Projects/Scarborough_Subway_P

 

[W. K. Lis]

If the 504 KING streetcar has a ridership of 84,000 over its mixed-traffic length, a light rail line over a private right-of-way should have more. No!! MUST be heavy rail subway.