Green Line LRT | ?m | ?s | Calgary Transit

[FCC1982]

Yeah - it’s too bad we lose the $5B if it’s not spent on this project that doesn’t justify the cost.
Better to spend it on the 8th Ave subway IMO (or about 10 other transportation priorities).

 

[whatchyyc]

IMO north leg > 8th ave subway > southeast leg
Sucks that it's going southeast first (even tho I live here lol) because the Centre St routes desperately need the capacity. At the moment, 7th Ave can handle both Red and Blue. 8th idea was partly born out of the assumption Green Line would use 7th Ave.

 

[darwink]

IMO north leg > 8th ave subway > southeast leg
Sucks that it's going southeast first (even tho I live here lol) because the Centre St routes desperately need the capacity. At the moment, 7th Ave can handle both Red and Blue. 8th idea was partly born out of the assumption Green Line would use 7th Ave.

So: many things.

The city decided the north didn’t need the capacity. That the system could cope with demand for many years. Having lots of parallel routes saves it there. Bus overloads are not a function of not having a corridor there—it is a service choice.

7th Ave in 2014 was straining under the red and blue.

At that point you can relieve 7th in two ways: move a line to 8th or reduce demand on red or blue (the MAX System are somewhat LRT relievers too).

In modelling it was a happy circumstance that building the green line diverts demand from red and blue, and that by providing alternatives long term let’s people allocate themselves better. Which pushes the red blue fail date out far enough that it becomes the one of the lowest priorities instead of the highest.

It was in the Bronconnier era 2006ish tunnel study that thought about the trade offs between the tunnels. As the 2nd St tunnel was much shorter; and had fewer underground stations; it is assumed the cost would be much less than the 8th Ave behemoth.

Believe it was the 1996 GO Plan which removed the SE LRT as a South LRT sour from Anderson. If have the exact year wrong, still save to say it was decades ago at the very least.

 

[accord1999]

It was in the Bronconnier era 2006ish tunnel study that thought about the trade offs between the tunnels. As the 2nd St tunnel was much shorter; and had fewer underground stations; it is assumed the cost would be much less than the 8th Ave behemoth.

I guess the planners of the mid-2000s didn't expect the planners of the mid-2010s to go hog wild with tunnels and plan a 4 km tunnel for the first version of the Green Line.

 

[lemongrab]

So: many things.

The city decided the north didn’t need the capacity. That the system could cope with demand for many years. Having lots of parallel routes saves it there. Bus overloads are not a function of not having a corridor there—it is a service choice.

Can you elaborate on this? It just doesn't make any sense to me concurrent with a phase 1 SE LRT plan that doesn't even reach the main population...

 

[darwink]

I guess the planners of the mid-2000s didn't expect the planners of the mid-2010s to go hog wild with tunnels and plan a 4 km tunnel for the first version of the Green Line.

Yup. To protect traffic volume flows either the train had to give up speed, or traffic had to give up volume. The problem was 'solved' by spending allocating more money.

 

[darwink]

Can you elaborate on this? It just doesn't make any sense to me concurrent with a phase 1 SE LRT plan that doesn't even reach the main population...

There is no need for the North Central LRT south of Beddington for many many years because there is more than enough capacity to add capacity with buses.

That we choose not to run enough buses does not mean there is a need for LRT. But once we have decided to run LRT, phasing is the concern.

And you miss what the greenline is, and may be skewing your thought process: it is about getting to massive bus interchange points at 64th Ave and Sheppard, and delivering those bus riders to 7th Ave SW. It isn't about the line going past single family homes.

For phasing what we have for segments is something like this (removing OMC and LRVs from the Greenline, and offsetting greenline operating costs with bus service reductions to get a like for like comparison):

Now since both segments need the downtown segment to be successful, lets break up the Green Line Phase 1 and 2 to 7th Ave and North, and 7th Ave and South, to reflect the minimum possible project extents.
Lets work with this split (and remember that for the decision making process the numbers we can quibble with and still be fine; what matters more is we agree the proportion of each:

You can see even without the more advanced modeling of the incremental segments, that going south makes sense to do, even with all the other things being equal (like assuming an OMC costs the same to go north).

Now: what would I rather happen than what we're doing now?

Just build to McKenzie Towne and 64th nearly simultaneously.

There is no needs for these fights.

 

[YYCguy]

We seem reluctant to tunnel under downtown and under the Bow, but a little populated group of islands in middle of the North Sea can build an underwater roadway complete with roundabouts! The Europeans surely must have deep pockets and highly skilled engineers at their disposal.

 

[darwink]

Sure we can. Doing it with stations though, major risks involved digging shafts and pits. And those risks cost big money.

 

[potatopizzafan]

Meanwhile Stockholm, a city of water and islands, has a maze of 100 subway sations, half of those undergroud, with routes tunneling under waterways and through miles of bedrock

 

[YourBoy007]

Build it and they will come. Build it and they will ditch the car.

 

[darwink]

Meanwhile Stockholm, a city of water and islands, has a maze of 100 subway sations, half of those undergroud, with routes tunneling under waterways and through miles of bedrock

Difference is bedrock versus water saturated gravel, silt and sand supported by clay. Yay unconsolidated glacial sediment! Even the more bedrocky parts are sandstone, siltstone and mudstone. Sandstone and silstone can be tough, while mudstone degrades into soil easily. With the layers being so thin for the most part, you can have very different soil types along a tbm cutter head, and as the tbm advances.

https://www.tunnelcanada.ca/document-load.php?dir=2012&file=tac2012Paper127.pdf

From another paper:

Due to the geological history of the Calgary region, the bedrock in Calgary is highly variable in nature, from relatively weak mudstones to competent sandstones. The rock units found within the region are significantly interfingered and laterally and vertically discontinuous. For each project within the region which passes through bedrock, it is important to complete a detailed site investigation, including geotechnical strength testing in order to gauge the degree of lithification at the specific site location.

For the mudstone units, a lower correlation value of less than 10 for PLT results is suggested. Slake testing using a Slake Index test is recommended for samples of the mudstone unit encountered in the site investigations. The Index test allows for better quantification of the tendency of the unit to degrade with exposure to air or water.

Due to the discontinuous nature of the bedrock, it is important to always factor in a fair amount of variability into the expected conditions during the excavation design process. As well, it is important for contractors to incorporate the information provided by the geotechnical reports in the selection of the type of TBM and cutting tools.

Challenges at recent tunnelling projects within the city have been strongly linked to inappropriate TBM cutterhead selection, unexpected ground conditions and the weak mudstone unit. From review of the past experiences, it is highly recommended that combination cutting tools are used when tunnelling through the Calgary bedrock, which is a highly heterogeneous yet tectonically undisturbed sedimentary rock. The use of combination cutting tools, will enable TBM micro-tunnelling through the majority of the Paskapoo units, whether expected or not, along a tunnel alignment.

Due to the adhesive properties of the mudstone unit during excavation, it is recommended that the use of polymers or additives at the excavation face be further investigated, in order to reduce adhesion of clay particles. The reduction of adhesion of the mudstone to the equipment will improve advance rates by reducing maintenance and operational delays.

As several projects were found to deviate from their designed alignment, and in many cases required significant realignment, continual alignment monitoring is suggested for use in the micro-tunnelling TBMs. Gripper size should also be reviewed, in order to ensure that grippers are wider than individual layers expected within the tunnel wall, to avoid grippers pressing into discrete weak layers within the wall when advancing

TBH I am not sure what conditions would be worse for tunneling.

 

[whatchyyc]

I mean there's no real reason to spend all the money trying to tunnel underneath the Bow, most I'd see happening is the bridge going into the side of the hill on the north end Edmonton style

 

[Surrealplaces]

I mean there's no real reason to spend all the money trying to tunnel underneath the Bow, most I'd see happening is the bridge going into the side of the hill on the north end Edmonton style

If it wasn't for the line running down 7th ave, they probably would have gone with the at grade path. They'll have to either tunnel under or go elevated....or bury the 7th ave line.

 

[FCC1982]

Build it and they will come. Build it and they will ditch the car.

I’m not sure they will.