DART+ (DART Expansion)

gjim

@murphaph - not sure how this would help? The TBM was planned to go into the ground about a half a kilometre north of the Spencer dock buffer stops?

DoctorPan

https://www.boards.ie/discussion/comment/119427402#Comment_119427402

https://www.dartplus.ie/en-ie/projects/dart-north/public-consultation-round-1/dart-coastal-north-emerging-preferred-options#howth

Current plan is an extension to platform 2 to allow trains to terminate and turn around with a doubling of trains per hour on the branch.

murphaph

https://www.boards.ie/discussion/comment/119431865#Comment_119431865

It doesn't have to though? It can be inserted through the active station during night time possessions if stubs are provided to assemble it.

murphaph

https://www.boards.ie/discussion/comment/119431946#Comment_119431946

If they could eliminate the Sutton level crossing it would make an excellent test bed for fully automated DART running.

spacetweek

https://www.boards.ie/discussion/comment/119426164#Comment_119426164

You see "isolated stations" but I see high quality public transport that can be used as the nuclei for future large-scale housing development - transport and housing are strongly connected concepts. Solving the housing crisis is partly a case of solving the public transport crisis!

However I agree 100% that particularly Inchicore and to a lesser extent Cabra West stations should be built at this time, not later. Cabra West (indicated as the white line below) could be located at the southern end of the new Hamilton Gardens development to reduce overlap with the catchment of Broombridge DART station and the new path marked in yellow would reduce walking time to areas further to the south. This would even allow the station to serve the north end of Stonybatter.

L1011

https://www.boards.ie/discussion/comment/119432010#Comment_119432010

This station / platforms are not going to be the platforms used for DU. This is a terminus, DU will be through. The terminal platforms will still be required.

murphaph

For terminating what though? Surely a DU station with 4 platforms (two or three for through running, one or two for terminating trains) would be more than sufficient, given the whole point of DU is to link up lines and allow through running. If DU was built as planned, Connolly Shed would be much more easily reached from Sligo/Longford and sure the existing Docklands station could just be left if needs be.

Sam Russell

https://www.boards.ie/discussion/comment/119432023#Comment_119432023

That is a very good point. If it was fully automated, it could do a turnaround in minutes, and with a slight speed increase do a ten minute service with just two trains providing the service. Fully separate, they could perhaps even re gauge it and use metro rolling stock - and use it as a testbed for the Metrolink.

gjim

https://www.boards.ie/discussion/comment/119432010#Comment_119432010

There continues to be confusion about the fact that DART+West Spencer Dock station has almost nothing to do with the proposed DU station (which is called "docklands" in the current documentation).

They are in different locations, are at vastly different depths and serve different purposes. The "DU docklands" station will have 2 through platforms only - no terminal platforms at all - and will be a fully underground station with the platforms at least 15m underground and will be located between Mayor St and the Quays. Spencer Dock will have 4 terminal platforms at "sub-surface" level - i.e. the catenaries will be at street level and will be located between Sheriff St. and Major St. The idea is that the two stations are near enough that they can be linked via escalators and tunnels - like you see with a lot of stations in London.

It seems you're suggesting that they come up with a design to combine the two stations into one which seems to introduce a huge degree of complexity and expense for little benefit. And it's at odds with the highest scoring option (i.e. "preferred route") identified in the Jacob's study on DART underground options which has the TBM underground 350m north of Sheriff St. passing under the foundations of Spencer Dock on it's way south under the Liffey.

L1011

https://www.boards.ie/discussion/comment/119434517#Comment_119434517

Its going to be the terminating station for a substantial volume of West and South West trains (the others will go to Bray, or Heuston). Those trains will not be routed through DU. There is no need to have them drop to tunnel level

AngryLips

https://www.boards.ie/discussion/comment/119435422#Comment_119435422

Sorry, but if they build two stations down the road from each other instead of one then that's even less foresight and joined up thinking than I give them credit for. But I also think you're wrong - there's no plan for DU so there's no certainty of station location. We know they'll build a station in Docklands, but exactly where is something we'll only find out when plans are made and there's no doubt such a station would be located where there's an existing station ...such as Spencer Dock

highdef

https://www.boards.ie/discussion/comment/119434805#Comment_119434805

What about the other three level crossings on the Howth to Howth Junction branch line?

gjim

https://www.boards.ie/discussion/comment/119435936#Comment_119435936

You “think” incorrectly. Please read the Jacob’s report commissioned by the NTA which provides a reevaluation of DART underground options in light of the results of the transport 2016-2035 plan.

Weird to claim (falsely) that there is no plan for a future station and at the same time claim with certainty that you know where (incorrectly) this station is going to be located.

More reading and less bluster please.

murphaph

There's no misunderstanding on my part. I am indeed claiming that a country with more than an ounce of foresight would come up with a unified station design now that could serve both the medium term need to terminate large numbers of electric trains in the city centre and also serve the long term need to allow through running under DU.

It's not rocket science. Westland Row Station was originally built as a terminus but it isn't today. They knocked a hole in the back wall and continued the line over the Liffey. In essence the Victorians did overground what some here claim (albeit underground) would be impossible to do. Why are there not two stations at Pearse today?

You just build a single station on the planned DU alignment but using cut and cover, leaving stubs south of the temporary buffer stops, hidden by a false wall, to insert the TBM then continue boring if and when DU is given the go ahead. It's really not as complicated as is being made out here. What it requires is to fix the DU alignment now and then commit to it.

Berlin has loads of stubs and extra platforms and whatnot for stuff that will eventually be built. We are completely overcomplicating things here.

Pete_Cavan

https://www.boards.ie/discussion/comment/119436777#Comment_119436777

Despite your opening line, your post shows a clear misunderstanding of the situation. Your reference to Westland Row Station and knocking a whole in the back wall supports this.

To get to the required depth at North Wall Quay, the track has to be getting deeper from north of Sheriff Street. An intermediate level station ~200m long means you need a much steeper gradient before and/or after the station. That's not "overcomplicating things", it's geometry which is extremely important for rail alignments.

Tracks were extended from Westland Row Station at same/similar level so entirely different situation to here.

murphaph

I'm not an idiot Pete. I know it's different but it's also the same in many respects. The DU alignment will have to get down to that level anyway. There's nothing stopping us creating that alignment now and creating the future DU station now.

I am pretty sure it's a station of convenience we are getting because otherwise you need to commit to DU and spend more money up front on a more expensive structure and you also have disruption to Luas up front (as you'd need to sever the red line during construction of a station slightly further south). To avoid these (relatively minor) problems a path of least resistance (for now) has been chosen.

By the way I think a lot of people overestimate how shallow a gradient electric multiple units need, especially in a tunnel where rain is not a concern. Take a look at Newcomen Curve, which is to be electrified to allow access to Connolly P7 for DARTs. That is the sort of gradient the DART can handle. And that's outdoors.

Pete_Cavan

https://www.boards.ie/discussion/comment/119437419#Comment_119437419

As I said before, you could build a station at North Wall Quay at the required depth to later pass under the Liffey. That would involve much more heavy civil works (the works area would be longer and much deeper), much more design work (for the tunnel and it's alignment) and much more disruption.

Talk of stubs sounds nice but in reality they would likely have to be mined out under the old station and/or quay (where digging down directly isn't possible) and be extremely expensive, more so than the TBM simply boring through there. And you'd need a huge space down there if you want to dismantle and extract a beast of a TBM without impacting on the station.

There are no benefits to this additional cost, disruption and effort now, and potentially no benefits ever if a different solution is chosen in the future. It would impact the cost side of the DART+ West Business Case for no corresponding gains on the other side. You also assume that it would be cheaper to do that extra work now )at a time of high fuel costs, labour shortages and rampant inflation), than in the future which is not necessarily the case. And that's before considering the opportunity cost of spending money now for no benefit v putting that same money into productive use now.

murphaph

The stubs wouldn't need to be that huge now in fairness. They also wouldn't need to be mined, the station box could simply be built larger to accommodate the TBM's assembly. You could even use the space temporarily as retail until DU is actually begun. If you still didn't believe in all that, you could leave the stubs off altogether for now and just leave a void big enough to allow the stubs to be mined out (in fact you'd only need the departure stub, the other TBM would arrive directly into the void from the Heuston end).

It all comes down to cost. Do we build the DU station now and temporarily use it to terminate trains or build a station that cannot be used by DU for less money. The latter definitely complicates DU later, to such an extent I believe an alternative to the originally planned scheme will be required. If you think mining a single stub tunnel is expensive, you should accept that mining an entire station partially under the planned SD one (as would quite likely be required if the SD station goes ahead, at least partially) would be enormously expensive compared to excavating a station box from the top down. So let's maybe talk about that aspect? Let's talk about the expense of "temporarily relocating SD station during DU works". That's a euphemism for building a third disposable station in the Docklands.

Construction isn't even starting right away. There could well be a recession this winter. Costs might well be lower than now. In all seriousness, hoping that construction costs fall as a justification for taking an easier option now that results in a significantly more complicated set of works later is folly.

Like I said before, if it was your own money you'd build the DU station up front. It's politically expedient to build the (not massively) cheaper station north of Mayor St. to suppress the cost of DART+ and to not interfere (for now) with red line services.

What is proposed is the equivalent of wanting a basement at some stage but building the house without one first and "retrofitting" it later. In practice you tear the house down, find somewhere else to live for a while then build a basement and a new house on top.

AngryLips

https://www.boards.ie/discussion/comment/119436164#Comment_119436164

You seem to be of the impression that there's a plan for DU ...there isn't. There's just a general notion that it'll be planned for one day.

murphaph

https://www.boards.ie/discussion/comment/119439815#Comment_119439815

That's exactly what's wrong though isn't it. There should be a plan already. DU is not some vague aspirational thing. Significant effort has already been undertaken including site investigation work and test bores and a route could and should have been selected and protected by now, including purchasing any required land as it comes up for sale. Building major infrastructure in a disjointed and uncoordinated way is a sure fire way to blow way more money than is needed. Ultimately it means less infrastructure will be built. That we are even talking about building a station that will (according to the available documentation!) require demolition or abandonment (temporary relocation is a euphemism for demolition and or abandonment in this case) is an indictment of infrastructure planning in Ireland.

VeryOwl

https://www.boards.ie/discussion/comment/119426164#Comment_119426164

This is probably the more urgent correction that needs made to these plans. A step in the right direction was taken when Heuston West was integrated into DART SW+. I don't know if it's possible at this stage for the plans to be amended to include the additional stations but it would enhance the project.

Pete_Cavan

https://www.boards.ie/discussion/comment/119439693#Comment_119439693

If you build stubs or a void or whatever without mining, it can't be under the old North Wall Quay station building. This pushes the station and everything further north. I don't know how much space you need to accommodate and dismantle a TBM but I'd think 50m wouldn't seem unreasonable. That would push the northern end of tunnel station platforms back to mid way between Mayor St and Sheriff St and impact the gradient on approach. And even in its dismantled form, there will still be large heavy elements which will have to be craned out so some parts of any building there would have to be opened up.

It would be a significant extra cost now, maybe as much as €100m, purely in the hope that it is off use in a few decades time. It makes more sense to put that money into something which returns value immediately and for the intervening decades. The tunnel will be extremely expensive and the station at NWQ would be a relatively small but expected cost in it. Tying money up in it for decades for no benefit would be crazy and make very little difference to the cost of the tunnel project.

I think you are over-playing the issue of temporarily relocating SD station. Much of the cost of creating the station will still be beneficial later, i.e. starting digging at -3m with retaining walls either side rather than ground level. I also think you down play the difficulty of connecting bored tunnels into a live station and getting rid of a TBM. This would be disruptive and any potential saving from building the station box now would be negated by designing it around future connection to the bored tunnels and removing TBMs.

CatInABox

I'd hazard a guess that when it comes time to design the new dart underground, they'll double the frequency but half the length of the trains. That'll make the station box significantly shorter while maintaining capacity.

They could then build the station box in between the old north wall station and the new Spencer dock station relatively easily. Doesn't solve all the problems of course, but it solves a good few of the them.

murphaph

https://www.boards.ie/discussion/comment/119443400#Comment_119443400

As I said, you could just leave enough of a void to enable mining a stub departure tunnel under the North Wall station building later. You don't actually need to mine anything or build any void large enough to set a TBM off from today. You just need to build the station on the DU alignment and provide a small space behind a false wall behind the buffer stops to enable a single departure stub to be mined out (while the station remains open) so a TBM can be inserted there from one of the station running lines during weekend possessions.

In reality you have no idea if the retaining walls are deep enough for the DU station Pete. You're just guessing that they might be. If they aren't (and there is no reason to think that they are as DU is not being considered at all in the plans as far as I can see) then the entire station will be for the bin. You're also guessing at the 100m extra figure. Where on earth does this come from if you don't mind me asking? Why would building the station slightly further south and slightly deeper and providing a false wall and small void beyond the buffer stops cost 100m more than what's actually planned? Even if it does, it would be 100m well spent IMO because not doing it means building another new station for DU which would need to be mined partially under the planned station and then you're into very large sums. Why not build the damn DU station now then it's done and offices can be built on top of it. The lost rent in keeping the DU station area clear for decades would more than pay for the TBM's extraction and disposal. TBMs are often just abandoned underground anyway if it's easier. You just drive them off to the side and finish the last bit manually. If you don't want to do that then break through behind the false wall and cut up the cutting head (the rest of the TBM can be disassembled and removed in parts the way it went in), removing the scrap via the rail network during weekend closures. The rail network could be used to remove larger components.

I don't follow your line of argument about the DU station cost either. You have claimed that mining even a single stub for a tunnel would be enormously expensive but at the same time argue that the entire DU station would be "small beer" later on. The DU station could be built relatively cheaply now, later it will be significantly more expensive and disruptive as DART+ will be live. Build the DU station now while the area is a wasteland and you genuinely will save a hundred million and much disruption later.

D.L.R.

https://www.boards.ie/discussion/comment/119439624#Comment_119439624

A different solution in the future? That's a weak argument after two separate consultations a decade apart have come to the same conclusion. How many do you need?

Keeping your options open forever is a bad way to go. There comes a point when you have to have the confidence to commit. There are huge benefits to constructing this underground now, but sadly they are long term benefits, and the Irish state doesn't do long term benefits.

Building an underground station from top down now rather than mining it out later would also be better value for money. It would set up DU perfectly for a future govt, and it would also commit the state to this routing of DU, which is the best solution.

No benefits, that's a laugh. No benefits in this electoral cycle you mean. The surface station plan hasn't got much benefit, moving the station one block south and complicating DU in the process. The juice isn't worth the squeeze.

gjim

I don't get this desire to turn a reasonably straightforward terminus station into something that would require huge expense and disruption.

DART+ is basically the earlier DU/Interconnector project without the tunnel.

The problem that Spencer Dock addresses is that there is no city centre capacity for DART S and SW. The options were: upgrade Connolly or build a new terminus in the docklands. The former was examined and estimated to cost at least 800m and involve huge disruption.

So you're looking at the docklands for new terminal capacity.

Spencer Dock station is a relatively simple terminus from an engineering and cost perspective. To provide clearance under the Sheriff St arches, the ground needs to be lowered by a little under 3m. The only engineering needed is managing the phreatic surface (waterline) but it's no more a complex task as that faced by the apartment buildings in the immediate area.

The rest of the work is to provide the track work connecting both the canal and Drumcondra lines to the 4 platforms. The main entrance will be right at the Spencer Dock Luas stop, providing decent onward options for passengers. Also the immediate vicinity has/is densifying rapidly so it's a destination in it's own

I just can't see what it buys anyone to build an entire deep underground station for these four terminal platforms at a depth matching the expected depth of the the future DU platforms? You're talking an order of magnitude more engineering, time, cost and disruption. And for what? There would be no immediate benefit to passengers and there would be no future value given that very few, if any, DART S or SW trains will terminate here if DU is ever build.

Combining two separate projects (linked by escalators) into a single complex mega-project which will deliver zero extra utility just goes against every instinct I have as an engineer. There is no reason at all that these terminal platforms need to be integrated into the DU station at North Wall Quay.

MyLove4Satan

https://www.boards.ie/discussion/comment/119435422#Comment_119435422

Thanks for clearing this up as I was confused myself but his makes perfect sense.

murphaph

The future value would be in allowing DU to actually proceed. Building a station in the alignment is a surefire way to make sure DU doesn't happen to be honest. Were would DART+ trains be terminated during the euphemistically named "temporary relocation" of SD station?

murphaph

Oh and a 4 platform underground terminus can easily be converted to a 2 platform through station with very high footfall retail opportunities. Nobody says the 4 platforms have to remain forever.

As DLR sums up... it's massively cheaper to build the station from the top down now than mine it out later.

It also brings station construction in the area to a close and the air rights above these huge plots can finally be realised. Every year that an office block is not built over them tens of millions in rent are lost.

gjim

The DU "alignment" will be 10m underground by the time it gets to Sheriff St. This is the entire reason for using a TBM - the fact that there is a building overhead - even if it's a station - doesn't "block" the alignment or DU, otherwise we'd be talking about demolishing half of the south inner city to accommodate DU.

I don't even know what you're proposing exactly could be done instead which would avoid disruption if/when DU were to be built? It seems you're suggesting that as part of DART+ W, they cut n' cover to a depth of over 15m for the three alignments (canal & Drumcondra lines and the northern line spur). This would have to start at Ossary Road given the 3% gradient limit and would sever Mayor St and the Red Luas for a year or more. Then build a large 4 platform underground station between Mayor St and the Quays only to later "convert" it to a 2 platform through-station and accommodating a TBM at the site while somehow continuing to use the 4 platforms as a terminus without disruption?