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DART underground - options

gjim

I hadn't seen it mentioned here but the original DART underground route selection has been revised in line with the current plans for DART+, ML and other PT improvements. The document is quite interesting as it covers a range of options for DU (including the fetish for a College Green stop promoted endlessly by one particular poster). The document was published last year: https://www.nationaltransport.ie/wp-content/uploads/2021/11/DART-Tunnel-Route-Options-and-Feasibility.pdf

TLDR; the preferred route is very similar to the the previous (2014) one with a few minor changes. No surprise really. The western tunnel portal would be moved a bit further east. The TBM would be started at the Eastern (docklands) tie in. The positioning of the underground stations have been moved a little bit but in ways that all seem like improvements to me. Hueston underground would be directly below the existing building rather than further east. The docklands underground station will be directly below the planned DART+ docklands station although the platforms will start and end further south than the overground platforms allowing an entrance at the quays.

It also evaluates a bunch of fairly crazy looking alternatives - including linking the Kildare line to the Northern by swinging under the Liffey just east of Hueston, and linking the Kildare line to the Southern coastal line without crossing the Liffey at all (from page 24):

There is a lot of interesting stuff about demand modelling, geology, avoiding historical monuments/sewers/etc, station access and design and the like - the sort of thing the crayon experts generally don't consider. For example a station at Tara is more or less ruled out because of a large sewer which Irish Water say would be very difficult to move.

I know this stuff is all fantasy for now but apparently the preferred route will be "protected" in some way although I don't know what this means in practice.

There was a previous thread (https://www.boards.ie/discussion/2057289979/dart-underground-alternative-routes) which I would have liked to post to but it's been closed/re-opened/closed a few times and is currently closed. Mods - feel free to move this discussion to the older thread. I think it might make sense to do so as this is quite relevant.

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loco_scolo

https://www.boards.ie/discussion/comment/122441889#Comment_122441889

Yeah this is spot on. The city is sorely missing a solid infrastructural development plan. All this prime land which could be utilised so well, but unfortunately is likely to be developed on. If a line could extend around that area, it could include an additional Docklands station and enable v.high density housing.

Clontarf Golf Club is another example of this. Huge potential there to have a rail tunnel portal - as a DU alternative or a fully separate future line - but alas this is also likely to be developed.

At Spencer Dock, the Dart plans include provisions for an 'over station development' of a tall landmark building. If that is built without first doing the prep work for a tunnel, it may not be possible to do it without also knocking the tall building. The Railway Order for Dart West does not address the whole topic sufficiently enough, which is very poor.

Looking at the DART Tunnel options report, there is one interesting option that wasn't short listed, but if you didn't want to move Spencer Dock station, could work well as a Plan B.

I think it is S1 R08 and goes Heuston – Christchurch – St. Stephen’s Green – Pearse – Grand Canal Dock (new Station) – Docklands

Though in this case Docklands isn't under Spencer Dock, but instead at North Wall, near the end of the Red Luas line. And then the tunnel portal is I think in the railway freight yard. Plenty of space in the railway yard for a tunnel to emerge.

The report doesn't go into details on why it wasn't short listed, I think they preferred Spencer Dock, but if that isn't a runner, this looks like a good workaround. No need to close or move or impact the operations of Spencer Dock while building it.

In some ways it even has a more interesting selection of interchanges and stops on the route.

If you wanted a cheaper version of this you could do:

Heuston – Christchurch – Tara St - Grand Canal Dock - Docklands (North Wall)

Or even drop Grand Canal Dock to save more money.

KrisW1001

the reason, I suspect, is that a station at North Wall isn't very useful unless Dublin Port is going to move all operations out of the city; plus this routing would turn the Docklands/ Spencer Dock station (which is in a useful place) into a one - stop spur off the "main" line, which would have a negative impact on services both to there and on the rest of the line.

https://www.boards.ie/discussion/comment/122443371#Comment_122443371

Yep, but I wouldn't say it wouldn't be useful, what with the 3arena right next to it, but I do agree less useful with the port to the East of it, of course unless Dublin Port allowed just that sections of the port and the car import terminal to be developed, which would then make it very useful. Who knows over the next 30 years!

I'd also argue that a stop at Grand Canal Dock would greatly enhance it's usefulness.

I get what you are saying about Spencer Dock, though the counter argument is that is could add extra flexibility to the network with some services terminating at Spencer Dock, while others pass through North Wall Docklands.

The nice thing about it is no disturbance to Spencer Dock, no need to close it and move it, no impact to DART+ services while the tunnel is constructed. Just tie in the tracks once the tunnel is complete.

To be honest, I'm not really strongly arguing in favour of this, I'm fine with Plan A of temporarily moving Spencer Dock.

But if others are suggesting that is too hard/expensive, then this seems like a good plan B, at least compared to the ideas of using Clontarf Road, etc.

AngryLips

https://www.boards.ie/discussion/comment/122443371#Comment_122443371

Spencer Dock wouldn't exactly be rendered useless, it will still provide a better interchange with the Luas network.

KrisW1001

https://www.boards.ie/discussion/comment/122444759#Comment_122444759

As a single-stop spur on a through-route, it would very likely suffer the fate of Aldwych on London's Piccadilly Line: despite its central location, the overhead of providing trains to serve just this one stop, plus low ridership eventually caused the station to be closed. (Today, it is primarily used as a film location when a production needs a "Tube Station" location)

CatInABox

Regardless of which route is chosen, Dart Underground won't truly relieve the constraints for intercity termination. Spencer Dock could easily become an intercity only station.

Pete_Cavan

https://www.boards.ie/discussion/comment/122440119#Comment_122440119

I can't see how your 11m above the DPT can be accurate. Looking at several different mapping websites, they give ground level above DPT ~8m. The only planning application I can find from the area is the aviation fuel pipeline (DCC Ref 2552/15), it contains a section for the DPT crossing which shows ground level at 8.79m (on ABR). It also shows Crown of Tunnel Structure as 2.86m below ABR, therefore just below 6m. The DART+ Coastal drawings for Fairview Depot show spot levels from approx 8 to 8.5m. This ties in with the tunnel being 3m below the rail line (as per your link).

With 140m from DPT to the Tolka and a gradient of 3.5% (max gradient stated in DART+ Tunnel Options & Feasibility report), you can drop almost 5m. If at 7m at the DPT (1m or more above), you could be down to 2m before the Tolka, or 4m below ground. The portal would impinge upon the Tolka but not overly so (there's green space between the Tolka and East Wall Road if the river needs more space). It would seem to be possible on that basis.

I find your opposition here strange given you the other routes you are talking about. Going GCD and North Wall could add about 2km to the tunnel given the cuurves involved. Plus you'd need a several hundred metre long elevated section across the Tolka/ABR which would be very expensive and face planning difficulties.

Returning to the old DU plan and temporarily moving the DART+ Spencer Dock station isn't that simple and probably isn't even possible. That plan had a big impact on SSG which may not be acceptable after Metrolink has already taken a slice. The proposed Pearse station likely isn't possible already with no obvious alternatives available. Both stations require mining under the city's historic core.

Rather than the two interchange station plan (SSG and Pearse), I think Tara will have to be seriously looked at. The sewer is the issue there but if only building one station instead of two, you have a lot of budget to solve that issue. Also, a Victorian sewer is going to need major works at some stage and having that as a single point of failure on the city's sewage network isn't good. Going to Tara also reduces the tunnelled distance.

If at Tara, you can't connect to the Northern Line at Docklands as previously planned. That isn't a bad thing as then there's no fecking about relocating the Spencer Dock station, another plus. Just put an underground station south of Mayor Street and tunnel on to Fairview.

loco_scolo

https://www.boards.ie/discussion/comment/122446516#Comment_122446516

I think the line needs to drop more than you think. The line around Clontarf Road is +8m (based on comments above), then the rail tunnel itself would need to be 6-7m, plus you need clearance above the DPT and below the Tolka, let's say 1m minimum but probably a lot more in reality. So realistically, the tracks need to drop by a minimum of 16m.

16m drop at 3.5% gradient requires 450m distance.

KrisW1001

We can play with the crayons for a bit of fun, but the depressing reality is that the reason why the portal was planned where it was planned is because it's almost the only option.

https://www.boards.ie/discussion/comment/122446516#Comment_122446516

Pete, I just looked at DCC Ref 2552/15 and I don't know how you could look at those cross sections and think any of this is possible!

First of all on why my measurements are different from the plans, it is because they are measuring different things, Altitude using GPS versus AOD or above ordance datum. However it is the relative difference that matters and they are remarkably similar, my readings show it going from 6m to 11m, a 5m rise, while the plans show it going from 4.21m A.O.D to 8.76m A.O.D over the tunnel, a 4.5m rise, remarkably close.

BTW I also took readings over at Clontarf Dart Station, one up on the platform and one an the entrance door of the station, so you can see the relative difference:

Now, lets look at the cross sections:

https://webapps.dublincity.ie/AnitePublicDocs/00497800.pdf

https://webapps.dublincity.ie/AnitePublicDocs/00497799.pdf

So let me get this straight, you want to smash through the Diaghram walls of the Port Tunnel and basically put a heavy rail line almost on the roof of the tunnel!

What the above shows is that the Port Tunnel is 6 meters above ground level.

But if you look at how deep below the tolka they put the pipe, it is a good indication of depth of the roof of the rail tunnel, at least 2m below the tolka. So -2.84m AOD to 8.76m AOD. So it would need to rise 11.6 meter, but that is from the roof of the train tunnel. Say add another 5 or 6 meters from track level and you are looking at 16.6 to 17.6 meter rise in less then 140 meters!

Spot of with your guess there loco!

So you need 450 to 500 meters, completely impossible at this location!

Of course a major disadvantage of even trying Clontarf Road, is that it would then only connect to the Northern Line. Where if you go via Docklands station you can not only connect to the Northern Line, but also both the Western lines, giving you much more flexibility and routing options.

This would also be true of a plan B North Wall Docklands station and link via the rail freight yard. Far more flexibilty then going to Clontarf or beyond, if it was even possible.

murphaph

Tunnels lie directly atop other tunnels all over the world. In many metro stations in London, Paris etc. the upper tunnel actually slices through the top of the lower tunnel and these upper tunnels are clearly visible from the platforms below.

I have no idea of what's feasible at the port tunnel location but tunnels certainly can lie virtually on top of each other. Dublin Clay is not known for subsidence AFAIK.

I also think that in general people underestimate how steep the grades can be for EMU stock, even though Dublin already has some quite steep grades on the two Luas lines and internationally we see lines that actually do feel somewhat like roller coasters. In Berlin we've got both hauled stock and EMU's shooting up out from the subterranean platforms at Hauptbahnhof northwards up over the Ringbahn and back down into Gesundbrunnen Station. Here's a side image of two of the flyovers. The upper one carries regional and intercity trains, the lower one S Bahn multiple units:

AngryLips

https://www.boards.ie/discussion/comment/122447254#Comment_122447254

What would the advantage of connecting it to Dart West be? Weren't the original service patterns for Dart Underground envisioned services from Hazelhatch northwards towards Malahide rather than Maynooth? Interchange would be provided at Pearse either way.

KrisW1001

@AngryLips It was the 2015 review, rather than the 2010 DU proposal. The proposed services were to run on two “lines” in an X pattern, with Hazelhatch-Malahide and Maynooth-Bray as the two arms, crossing at an interchange at Pearse

taken from the 2015 DART Expansion review presentation, here: https://view.officeapps.live.com/op/view.aspx?src=https%3A%2F%2Fwww.nationaltransport.ie%2Fwp-content%2Fuploads%2F2015%2F09%2FDART_Underground_Expansion_September_20151.pptx&wdOrigin=BROWSELINK

The way the tracks actually are today, with Western services connecting directly to Spencer Dock, there would be nothing to prevent any arm of this X pattern serving any other arm (e.g., Drogheda-Maynooth, Bray-Hazelhatch would also be possible ).

The advantage of including the West line mostly applies to services through Heuston. With Dart Underground in place, and using the Glasnevin-Docklands stretch via the Park Tunnel, you can have Heuston DARTs make an orbit of the city centre before heading back toward Hazelhatch. The necessary links aren’t there for Maynooth services to do the same thing, but Maynooth services could do that same city tour then go on to Hazelhatch.

Basically, connecting Western line to the tunnel allows all of the city-centre stations to become through-stations, and through-stations always have higher ridership than a terminus in the same place.

https://www.boards.ie/discussion/comment/122447345#Comment_122447345

Sure, but in this case there simply isn't enough space for the tracks to rise up from under the Tolka to a bridge like the above over the DPT. At most we are talking about 140m's of space, when given the gradients you'd need 400 to 500m.

Given the gradient, the only way you could do it would be to literally drill straight through the Port Tunnel!

Honestly the park Pete is talking about here is absolutely tiny. Google Maps can be deceiving sometimes. If you went and stood in this little bit of park, you'd realise how silly the idea that you could fit a train tunnel in this little section of land, along with a bridge over the DPT and actually be able to rise between the two!

https://www.boards.ie/discussion/comment/122447539#Comment_122447539

Sure, that was the original plan for Dart Underground, but DU is dead. DART+ didn't exist as even a plan when this DU plan was envisioned.

A new DART+ Tunnel might have a very different service pattern. It will need to take into account DART+.

Now I'm not saying it will do this, but you could leave DART Coastal line as it is and us the tunnel as a semi circle line:

Hazelhatch - Hueston - Tara St - Docklands (Spencer or North Wall) - Glasnevin - Maynooth

Eventually if they connect the Western and South West line as planned by the AIRR, you could even have a fully circular line around the city.

To be clear, I'm not saying we should do this, I haven't thought about it enough, but flexibility to change how the tunnel is used as the city grows would be attractive one. Choosing a route that is longer, more expensive, physically impossible and precludes that flexibility seems silly to me when the cheaper, easier and possible options allow for that flexibility.

riddlinrussell

I think some form of station "near" Spencer Dock (with internal pedestrian tunnels linking to it, travelators/escalators etc.) Avoid having to expensively mine out under the station, lines come above ground at current Docklands.

Hell, drain the canal there and cut and cover it under that!

Additional entrances towards Mayor Square direction as well.

If you've experienced the London underground, people don't often really psychogically consider that inter-mode travel to be 'real' because its all inside the system.

Then end up with the tunnel linked in well to the western line, and the currently poor link to the northern line there becomes a 'no-brainer' to upgrade to some sort of flying junction (expensive but assuming we already have the tunnel built at this stage it would probably become the biggest value add project for rail in the whole country...

https://www.boards.ie/discussion/comment/122449160#Comment_122449160

Yes, that is a very interesting idea, I know they have built stations in canals like that in Amsterdam.

Another possible option is to just put the tunnel portal North West of Spencer Dock, basically north of the block west of Spencer Dock rather then Spencer Dock itself. Basically along the coach park parallel to Docklands.

Connect it into the Western lines, looks like you have about 450m's there to play with. No disturbance to Spencer Dock and it continues as a terminus for northern line services before and after.

Alternatively it could connect into the Northern line, just more disruptive to Spencer Dock during construction.

Create an underground passage between this new Docklands Station and Spencer Dock.

riddlinrussell

I'd basically treat it as one homogeneous "Spencer Dock" station, with a few terminating lines in the "main building" and then the tunnel through lines under the canal. It would be somewhat akin to the distances involved in Bank/Monument station (with a considerably less convoluted layout) so it would be a "Connoly-esque" station with terminating and through services

bennyineire

Point to point distance from the end of the platforms between the 2 stations is just over 500 metres, easily walked that in NYC, London and Paris in underground passenger tunnels

https://www.boards.ie/discussion/comment/122449298#Comment_122449298

Yeah, it is a brilliant idea, I really like it, it gives a lot of operational flexibility and wouldn't impact the operations of "Spencer Dock" during construction.

You could even add platforms East of the current Docklands station to add termination capacity and integrate the three parts, station under the Canal, extended Docklands platforms, Spencer Dock.

Picture a wide underground walk way (ideally with shops, cafes, etc.), between the three locations. Stairs/lifts up to the platforms at the old Docklands platforms and into the Spencer Dock station and platforms. A very common design in large European city center stations.

Frankly that whole "Spencer Dock" complex you are talking about could replace Connolly as the main station in the area (obviously still keep Connolly).

Once you are all done building the platforms/lines/station, build tall office/apartment buildings over the site, integrated into the station.

Pete_Cavan

https://www.boards.ie/discussion/comment/122447245#Comment_122447245

Hmm the Tolka is deeper there than I thought. I knew a tunnel there would have to impact the bottom of the Tolka but it looks like doing so more than I expected. I still think it would be possible from an engineering perspective but the impacts on the Tolka would probably be too great in terms of environment and planning and wouldn't get approval.

And you don't just "smash through the Diaghram walls of the Port Tunnel" any more than the portal at Docklands would smash through the structure of the DART+ Spencer Dock station. Any work is designed to be carried out in a suitable manner based on the conditions and constraints present. The rail line would span over the DPT, NRA at the time gave a limit for imposed loads on the tunnel, a solution is designed within those parameters and methodology agreed.

Doing such works above the DPT would be a lot easier than mining out stations more than 20+m under the city centre, as would need to be done twice with the original route. The main benefit I see of going to Fairview is how it reduces the curvature of the alignment. It may allow connection to DART/Metro at Tara Street which avoids the need for two city centre stations. It also shortens the tunnel length. Plus you wouldn't have to relocate and excavate under the DART+ Spencer Dock station. A station at Tara Street should be a key consideration for the next review and look for solutions either side of that.

Pete_Cavan

https://www.boards.ie/discussion/comment/122449160#Comment_122449160

If coming above ground at current Docklands, that would severe access to Spencer Dock.

riddlinrussell

How exactly would it sever access to Spencer Dock? Does the current Docklands prevent trains from accessing the rails near the proposed Spencer Dock location?

I would imagine the extremely significant amount of works required to build the tunnel portal might stretch to a rearrangement of the existing track layouts in the Docklands Yards and approaches to achieve the correct setup for keeping both operating?

Pete_Cavan

https://www.boards.ie/discussion/comment/122451349#Comment_122451349

When you said "come above ground at current Docklands", I assume you are talking about the existing Docklands station. A tunnel portal there and the change in levels required would have to sever access to Spencer Dock from any line the tunnel connects with. The tunnel might be able to connect to the line along the canal but I doubt levels would work for the other lines. The other lines might still be able to access the Spencer Dock station.

loco_scolo

I think the suggestions above are a serious contender for a future tunnel. Rather than the previous plans to create an X shape network (crossing at Pearse), instead create two distinct lines 1) Dart Coastal and 2) Maynooth to Hazelhatch. With Grand Canal Dock as a main interchange.

The requirement to connect the elevated Northern line into a tunnel will hobble Spencer Dock Dart Station and be extremely expensive. It makes more sense to connect the Royal Canal line into a tunnel, since it's already much lower and creates far less conflict.

You'd maintain Spencer Dock Dart as additional terminating capacity for Maynooth and Drogheda Dart, Commuter trains and maybe even some IC services (extra services on busy weekends etc.).

spillit67

https://www.boards.ie/discussion/comment/122443371#Comment_122443371

I’m not so sure about that. 3Arena integration and a lot of development there. Dublin Port taking a lot of space but they still have things like the Flour Mill Masterplan. Also near Red Line integration would be good.

Down the road a bit from East Point but I imagine city bike and transit would he attractive for a lot of workers there.

spillit67

https://www.boards.ie/discussion/comment/122451608#Comment_122451608

I would think that the “old” (not yet built) Spencer Dock station would be more popular than Connolly for DART Coastal North passengers. Interchange there to get to GCD and St Stephens Green based on your map.

Down the road a bit from East Point but I imagine city bike and transit would he attractive for a lot of workers there.

East point already has a free shuttle bus service operating to the Red Luas line at the Point and also they have free electric bikes operating between the Point (and Clontarf Road) and the business park.

When they fix the pedestrian and cyclist access via Bond Road (happening as part of the Greenway project) it would make it extremely attractive.

Also the possibility of IR developing property in the freight yard.

OisinCooke

While I love the idea of draining the canal, I’m afraid that Waterways Ireland and the dreaded environmentalists will have something to say about it…

Would a potential solution be to build the station beneath the canal basin (not very deep at all at this location) and rise the line up the couple of metres in the site of the current Docklands station? (350 metres or so to do this…)

A connection to the Royal Canal Line looks like it could be made here along with a northern line and Drumcondra line connection. Along with linking (through clever placement of entrance and exit escalators) with the planned Spencer Dock DART and Luas station…?