DART+ (DART Expansion)

KrisW1001

If anyone's wondering why DART+ West is so expensive, remember that it has two major new station builds on it, at Glasnevin and Spencer Dock, the latter of which will be built underground.

Spencer Dock station will have four tracks at "basement" level (around 3 m below ground): IÉ are clearly not giving up on the idea of a DART Tunnel in future…

specialbyte

https://www.boards.ie/discussion/comment/122031784#Comment_122031784

Glasnevin is not part of the DART+ West RO. It is part of the MetroLink RO.

The other huge cost on DART+ West are structures like the underpass at Ashtown, bridges over the railway at Kellystown and most importantly the new depot that is designed to serve the DART+ fleet for all of the rail lines.

loco_scolo

https://www.boards.ie/discussion/comment/122031784#Comment_122031784

This has been discussed at length previously. The plans for Spencer Dock are not compatible with a Dart Underground tunnel. The new station, to be constructed with very deep foundations (to allow construction of a tall building over the station) are not deep enough for a tunnel extension.

The station would need to be demolished and dug deeper to enable DU as previously envisioned. These points are acknowledged in multiple reports. Just FYI.

cgcsb

https://www.boards.ie/discussion/comment/122031607#Comment_122031607

There's not a snowballs of DART+W opening in 4 years even if work started tomorrow. Current programmes have construction running till 2031

gjim

https://www.boards.ie/discussion/comment/122032227#Comment_122032227

It may have been discussed but what you've described isn't the conclusion of the discussion. And certainly the "tall building over the station and very deep foundations" thing is completely made up. The plans are here:

https://www.dartplus.ie/S3mvc/media/DART-West-Railway-Order/3%20Railway%20Order%20Drawings/Book%203%20Structures%20Plans/Specific%20Locations/01-Spencer-Dock.pdf

The station building will be 3 stories over basement (depending on whether you're looking from Sherrif St or Mayor St - Sherrif st is about 2.5m more elevated) - and the foundations are not "very deep" - again clearly documented.

There is plenty of distance between East Wall Rd and the site of Spenser Dock to accommodate an incline to bring tracks well under the foundations of the station - there's 800m of curve there.

"The station would need to be demolished" was just something made up by one of the more hysterical posters in that discussion and has no basis in anything official or unofficial.

loco_scolo

https://www.boards.ie/discussion/comment/122032531#Comment_122032531

You seem to be the only one who is in complete denial about what the various planning docs say, and indeed multiple reports which assessed the options for Spencer Dock and impact on DU.

Options Selection Report:

The 'Over Station Development' or 'Landmark Building' shown in planning docs. You can also see the Luas sub station at Spencer Dock at the same levels of the new Dart station.

2.5 to 3 meters thick 'Reinforced Concrete In-situ wall and slab".

Consonata

https://www.boards.ie/discussion/comment/122033000#Comment_122033000

Take a look at Point 3 under strengths. The Jury is still out on whether it'll be possible to avoid needing to lift the tracks

loco_scolo

https://www.boards.ie/discussion/comment/122033058#Comment_122033058

That point says "it might be possible to design...."

That's from the Options Selection Report in 2020. This is absolutely key, as they decided to go with Option B2 but haven't designed the station to be DU compatible. I absolutely guarantee you, if they took heed of that report and specifically designed the station to be Dart Underground friendly (as advised in the report), then we'd know about it.

But we don't. Cause it's not.

From the report:

It is not possible to construct the DU station once the Docklands Station is built because the soil does not have suitable characteristics to allow excavation of a cavern beneath the station.

The future proofing solution was to excavate the Dart station deeper and construct a tunnel section underneath the station. They haven't done this.

Annex-9-3-Docklands-Station-Options-Study-Summary-Report.pdf

KrisW1001

@loco_scolo Yes, the document does mention demolition of track and platforms, but that is stated as a worst-case scenario, not a prerequisite.

Also, some reports refer to Docklands, others to the new Spencer Dock station. Extension underground from Docklands is indeed nearly impossible.

I'm not trying to raise the corpse of the DU discussion, and if I were, I really wouldn't want to discuss it on this thread, but it was an interesting and pleasantly forward-looking decision to spend more money to build this station with four tracks below ground when there's no compelling reason to do so: the station will also take up the whole site at ground level, so it's not a matter of preserving valuable ground-level street frontage for development. It does however provide a nice straight route to bring tracks under the Liffey if that becomes desirable in future. Yes, cost of doing this would be very high... but now that the legacy rail lines in Dublin are nearly all back in use, any further provision of mass transport in Dublin city is going to be expensive.

loco_scolo

https://www.boards.ie/discussion/comment/122033552#Comment_122033552

Just to be clear, the proposed Dart Station is not underground. The platforms are only 5m below ground level. The substation under the Luas Station is also 5m below ground, and are directly in the way of extending the tracks. In any case, there isn't enough distance from the Luas Station to the river to get deep enough under the river.

A prerequisite to Option B2 (the chosen option in the Railway Order) was to construct a section of Dart Underground at the same time as Spencer Dock Dart station.

The report is very clear. Constructing DU afterwards is a non runner without demolishing the station.

cgcsb

I don't think DARTu is a runner now anyway at least not in its previous form because needs have shifted. If it were me I'd instead opt for a Lucan to Ringsend Metro line along with a Tallaght to Coolock metro line, that'd solve our big rail capacity issue permanently then just replace the core bus corridors with luas.

4 tracking the northern line will also further boost capacity. We can then abandon DARTu and the harebrained Lucan Luas

Pete_Cavan

"Demolishing" Spencer Dock station won't really be an issue. Services would have to be moved temporarily to the current Docklands station site but that wouldn't be a big issue.

The "demolition" would be removing platforms, tracks, track-bed formation, etc. but that wouldn't be such a big issue and would be more than worth it.

In any case, any future tunnel is outside the scope of this thread so not worth derailing the thread (again) over.

loco_scolo

https://www.boards.ie/discussion/comment/122036256#Comment_122036256

I would hardly label it not a big issue. The shiny new terminus of two new Dart Lines for the city closed for minimum 2-3 years, temporarily moved to Docklands 3.0, before moving back to the 4th incarnation of a Docklands station. Not to forget the over station Landmark building they are provisioning for, over the current proposal.

I'm not trying to derail this thread by bringing up the shelved DU, but people regularly refer to DU as a very likely certainty, which will happen at some point. If you actually read the various reports, it's abundantly clear the current proposal is a nail for the old DU.

gjim

You seem to be the only one who is in complete denial about what the various planning docs say, and indeed multiple reports which assessed the options for Spencer Dock and impact on DU.

No, I'm not the "only one".

KrisW1001

I'm sorry I mentioned it now...

loco_scolo

https://www.boards.ie/discussion/comment/122032531#Comment_122032531

@gjim I've addressed all your points by sharing diagrams, links and reports. Perhaps you can address those points?

Specifically the point that mining out a station under the Dart station being impossible due to soil condition. As others have acknowledged, this means the Dart station would need to be demolished.

There is plenty of distance between East Wall Rd and the site of Spenser Dock to accommodate an incline to bring tracks well under the foundations of the station - there's 800m of curve there.

There's only 500m of curve from Ossary road (+7m elevation) to the Spencer Dock site (-5m elevation). Assuming a tunnel height+clearance of 10m, you're suggesting 22m of incline (4.5%) along a curve. This is technically possible, but would make it one of the steepest curved inclines in the world. Such an incline would limit which trains could use the line.

Having the line in this location would also cut off freight access to Dublin Port. A point which you've ignored previously.

Pete_Cavan

Of course "the old DU" is dead, there isn't going to be a massive interchange with Metro under SSG for a start. If the DART tunnel project is eventually resurrected it will be very different to what was previously proposed for DU, that is abundantly clear and has been for years.

Under the Option 2B Weaknesses, the report says;

In the case that the clash with the DU TBM portal cannot be avoided, the current Docklands Station will be temporarily required when constructing the Dart Underground. Also, platforms and tracks would need to be demolished (still under study).

It is clearly saying that, unless a solution to avoid a clash is designed in, operations at the new station would have to be temporarily relocated, then you build the tunnel portal. The platforms and tracks would need to be demolished, that is not a big issue, most of the structure would remain. As a weakness, that is a fairly minimal one compared to the potential benefits. Yes it's not ideal to temporarily relocate the terminus but given the increase in heavy rail services the tunnel would allow, it's a small price to pay.

KrisW1001

The mitigation to avoid interference with a future tunnel was to basically excavate a box down to the depth of the tunnel and then build up: so you have a void where the tunnelled tracks would go, two floors of deep basement (strangely suggested as parking by the report writers; a usage that would never get planning), then at the top, the subsurface station level. The plans for the station in the RO application show that this is not being done.

The details of the mitigations and effects of tunnelling are from this document:

https://www.dartplus.ie/getattachment/6a87a772-a6fe-40f8-9504-0368b9e56e15/Annex-9-3-Docklands-Station-Options-Study-Summary-Report.pdf

(Thanks to @loco_scolo for the pointer).

So, either TII are happy to take the hit on building a station and then destroying it again within 20 years, or they're banking on future improvements to tunneling technology that will allow the tunnel to be bored, or they'll move the north portal to allow deeper excavation under. Experience with digging Metrolink nearby will probably decide what's planned.

My interest really was in seeing the impact that the possibility of a tunnel had had on the design of this station. I don't want the thread to get dragged into the tar pit of what DART Underground should, could or would be.

riddlinrussell

Is there no chance of them simply running Dart+ tunnel in so that it passes alongside the new station? That way it wouldn't need to be dug under the planned platforms, it could ascend to the same level and potentially end up with cross platform interchange. It doesn't need to go directly under the station at all?

bk

I hate to say it, it should probably be in it's own thread, but if you read the Dart+ Tunnel report it is pretty clear that Dart Underground or Dart+ Tunnel is dead.

The issue is, if I'm reading it correctly, is that Dart+ Tunnel would add just over 1% extra PT passengers versus DART+/Luas/Metrolink (Do Minimum Scenario).

The R01 route alignment option would increase the number of daily public transport trips by 10,250 (+0.99%) in 2035 and 13,680 (+1.12%) in 2050 compared to the Do Minimum scenario.

2050 Do Minimum: 1,212,411 (Daily PT Trips)
2050 Do Something - R01: 1,226,091 (Daily PT Trips)

Now the report doesn't go into a CBA, but they do say it would cost 5 to 6 Billion. The problem is that clearly spending 5-6 Billion just to increase passengers numbers by a relatively tiny 1% isn't going to pass any type of CBA.

Sorry, I'm sure it isn't what folks want to hear and I'll get shouted at, but it is all there in the DART+ Tunnel report.

DaBluBoi

https://www.boards.ie/discussion/comment/122037888#Comment_122037888

I thought the main point of Dart Underground was to decongest Connolly, no?

KrisW1001

The gradient would be impossible. You would need to drop 20 m down in just 200 m of track length (the distance between the buffers in the planned station, and the river's edge) in order to get the tunnel under the Liffey afterwards.

bk

https://www.boards.ie/discussion/comment/122037996#Comment_122037996

It would certainly help do that and also take pressure off the Red Luas line.

The question would be if that is enough to justify spending 5 - 6 Billion on? It would be a very hard sell I'd imagine.

loyatemu

the big argument for DU was that it "really tied the room together" by connecting all the other modes of transport in the city centre. But the redesigned Metro has removed a lot of that rationale by connecting with 3 Dart lines in 2 locations as well as the Luas.

AngryLips

Unless one of the options for Dart+ was to use it to alleviate the lack of 4 tracking on the northern line or to bring it along a different alignment northside and surface it elsewhere.

loco_scolo

A relatively simple solution to all of this is to have a Dart+ Tunnel emerge in Clontarf Golf Club instead of Spencer Dock. There are already plans to sell the Club for redevelopment - put forward by its owners.

At that location it could avoid tunnelling under the Port Tunnel (just skirts to the east of it), then emerge to join the Northern line. A longer tunnel but likely cheaper, as it wouldn't impact the Spencer Dock Dart station.

I fear this won't happen and that land will be built on. Hopefully Irish Rail can purchase the plot and preserve it for such.

bk

https://www.boards.ie/discussion/comment/122038210#Comment_122038210

I don't think that would solve much for the project. Yes, it helps resolve the issue at Spencer Dock, but longer tunnel would be more costly. It also wouldn't really resolve quad tracking, you'd need the tunnel to go all the way to Clongriffin to help with that, which would double the tunnels length and it starts to get silly expensive.

Sam Russell

Mod: If you want to discuss Dart Underground Tunnel (or whatever you want to call it) then please start a new thread.

It is not useful in this thread. There is so much more to say on other aspects.

Citizen Six

Busy new fit out of the wagon shop, ahead of the first delivery of new trains in September. This is where they'll be fitting the carriages with bogies, after road transfer from the port.

loyatemu

they're not being delivered with bogeys? Is this a new way of doing it - I seem to recall previous deliveries being put straight onto the rails in the port and hauled out.