DART+ (DART Expansion)

murphaph

https://www.boards.ie/discussion/comment/119416489#Comment_119416489

This makes no sense. If the new station is essential to the expanded dart network then how could you simply "not terminate trains there while the TBM is being launched"? If the station is so essential then DU can't go ahead as planned because there's no way the expanded network can be "paused" in x years time when everyone is used to it.

Pete_Cavan

Is there any reason why they want to launch the TBM from the city centre? It makes no sense to me and was the source of a lot of objections first time round. Much easierto bring in materials and get rif of spoil from the western edge of the city than from the city centre. Surely it would be easier to tunnel from west to east, then Spencer Dock would be the extraction site and the final couple of hundred metres could be built with a relatively short closure of the station there.

brianc89

https://www.boards.ie/discussion/comment/119417739#Comment_119417739

It's not just about the TBM entrance. It's about the gradient required. Max gradient is about 1m fall in 50m distance. Therefore, to bring the DU tunnel from 25m depth to surface level requires a run of 1,250m.

With the proposed Spencer Dock station, the only space available to do that will be gone.

AngryLips

A future DU could look to also solve the problem of double-tracking the northern line by bringing the tunnel further north though...

brianc89

Do you mean this? Start the tunnel / cut&cover near the top of Ossory Road. You would have the full length of the line in red to go under the Drumcondra / Royal Canal lines, then keep descending into a tunnel under those apartments.

In this case, we'd have the 2x western lines terminating at Spencer Dock and the Northern Dart line continuing into DU?

brianc89

https://www.boards.ie/discussion/comment/119417802#Comment_119417802

@gjim I'm pretty certain the current DU plan doesn't work with the proposed Spencer Dock station. The DU tunnel enters just north of Sheriff Street and would not have enough gradient to descend into a tunnel under SD.

What about the image I just posted? Do you think this would work for a future DU?

murphaph

The beauty of DU was the relatively short length of tunnel linking up multiple existing alignments. If you start hobbling the project so that you have to start tunneling much earlier (and this means mining a station at Spencer Dock rather than a much cheaper cut and cover version) you are making DU less and less attractive financially. You'll then run into a "sure we could build a whole metro line for that money" argument.

If it was your own money you'd build the planned station to be usable by DU without the need to close it. They only plan stuff to destroy it later because it's politically expedient to do so. Again, I'm not blaming IE for this. Government knows all this. They could say to IE, "let's build the new station so it's DU compatible" but they won't. They want IE to spend as little as possible on DART+ today even if it costs the taxpayer of tomorrow a hundred million more for longer tunnels and a mined station adjacent to the one planned. That's a disgrace really. They just get away with it because it's too detailed foremost people to be informed about it.

gjim

https://www.boards.ie/discussion/comment/119417816#Comment_119417816

@brianc89, the docs have the tunnel starting further north than Sheriff Street - closer to Ossary Rd./Hawthorn Av/Terrace like in your diagram.

You can't have the tunnel start near Sheriff St - you wouldn't be able to get the tunnel deep enough to get under the Liffey in time. Roughly it's 300m from the quays to Sheriff St. Max gradient, according to the docs, will be 3% but remember the 180m of platforms in the DU station have to be level, so this would only gives you 120m of gradient to get the tunnels deeper - about 3.5m of a drop. Nowhere near enough.

Starting the tunnel near Hawthorn Avenue - like you've sketched - which is over 400m from Sheriff St, means you're down 12m by the time you get to Sheriff St, so even levelling out for the DU platforms just north of the Liffey, you'll have enough depth to get under the river.

@murphapph - Spencer Dock is absolutely vital to be able to run any sort of meaningful DART-like service as part of DART+ SW and W. Between the two, at the VERY LEAST, you'll be looking at 12 trains an hour peak heading into town and there's absolutely no way to send these trains into or through Connolly. Even terminating all DART SW trains in Hueston and forcing commuters onto allready-packed Luas trams - an unattractive solution - would leave at the most 4 slots per hour available for DART W into Connolly. The only alternative to Spencer Dock was a massive upgrade to Connolly involving CPOing neighbouring buildings, years of disruption to the busiest station in the country and an estimated price of 800m.

The advantage of Spencer Dock is zero disruption to Connolly while under construction, zero land acquisition costs, almost net zero capital cost - the air rights over this station would be valuable in this location and the land around the current Docklands station becomes available for sale to developers. Also from an operational perspective, the W and SW tracks going into Spencer Dock are grade separated from the Northern line so there is no crossings between Spencer Dock and Connolly trains.

Yes, if (big IF) DU is ever given the OK, we are looking at lots of disruption all round and not just at this location.

murphaph

That doesn't cut it as an answer. If the Spencer Dock station is "essential" for the expanded DART network then it will not be possible to close it for the weeks or months required to build DU at the originally planned location. An expensive workaround will be required come the time. Let's be honest about that aspect.

brianc89

https://www.boards.ie/discussion/comment/119417958#Comment_119417958

@gjim, so as you say by the time the DU tunnel reaches Sheriff Street, you're already 12m below ground. The new Spencer Dock station is 10m below ground. Where could the DU tunnel POSSIBLY go after Sheriff Street without digging up Spencer Dock?

Those apartments to the west have at least one level of basement so it can't go that way. ALSO, if you use the space on the eastern side of the site to bring the DU tunnel 12m below ground, where on earth do the western lines go? They can't possibly get to the new Spencer Dock station if the DU is in the way.

Why do you refuse to see this?

murphaph

In reality if you're going to start mining a station then you would be mad not to build it directly under the river with entrances on both banks, a la the original plan for metro North at O'Connell Bridge. That significantly increases the comfortable catchment area of the station. Still, adds a hundred million easy to the DU price tag instead of just building this station DU compatible from the beginning, which is clearly the cheaper option.

MyLove4Satan

Wasn't one of the cheapo options for the DU was that it terminated in Spencer Dock?

Do you think this is what they are up to with this carry on now? A Charlemont like 'solution'? Perhaps this is even being done on purpose to start a 'Should be a through station!' uproar as an excuse to delay it even more?

brianc89

https://www.boards.ie/discussion/comment/119418985#Comment_119418985

I don't think this is an excuse to delay anything related to Dart+, if that's what you mean. The plan for Dart+ makes total sense on its own.

The new Spencer Dock would be a fantastic station. You could have Dart trains from Maynooth, Kildare and Howth (for example) terminate at SD. If you want to continue to Dart Coastal South you can switch at Clontarf or take the Metro from Glasnevin to Tara and switch there.

They just haven't, admittedly in the DU feasibility document, considered the impact of Dart+ on DU. I think this should be made abundantly clear on the Dart+ application.

At this stage, I'd question if DU is still feasible given the new Metro, Luas and Dart+ lines which have been built or are currently planned. But that is a very different discussion.

AngryLips

https://www.boards.ie/discussion/comment/119419099#Comment_119419099

I don't think Dart Plus allows for interchange at Clontarf Road between Maynooth/PPT services with Dart coastal services, does it?

brianc89

https://www.boards.ie/discussion/comment/119419220#Comment_119419220

No sorry I wasn't clear. I just meant that Dart trains from Howth, as an example, could also terminate at Spencer Dock, as well as trains from Maynooth and Celbridge. This would make Spencer Dock a super busy and useful station.

The current coastal dart line could remain as-is with regular trains from Malahide and Drogheda, going directly to Connolly, as they currently do.

Pete_Cavan

I think people are getting a little over-excited. The new Spencer Dock station will likely be out of action when/if the tunnel happens but I dont think it is as bad as people make out. The retaining walls either side of the new Spencer Dock station parallel to the tracks will likely have to go down deep enough anyway to allow the level be reduced as required for the future tunnel connection (and the cross section drawings suggest this also). In that case, it is relatively straightforward to do that work later, although it would require an alternative terminus, possibly the existing Docklands station. In reality, the new Spencer Dock station will likely be in use for 20+ years and will have justified its cost by then and the retaining walls should still serve a purpose.

The big issue is the assumption that the tunnel portal is in the Docklands as this requires much more space for a much longer time. The DART+ Tunnel Route Options and Feasibility says "The Docklands location is in railway land and there could be potential to use the rail network for material supply and spoil removal". This doesn't make any sense, how is bringing all materials and spoil into the busy city centre a sensible thing to do? The railway network in this area is unlikely to have capacity for material supply and spoil removal anyway so hardly an advantage. If the future SD station location is the TBM extraction point, it should really reduce the works required in that area and allow this station operate for longer. Basically, I think all this station will do is force the future tunnel designers to reconsider the TBM launch site.

brianc89

https://www.boards.ie/discussion/comment/119419344#Comment_119419344

Look, I don't want to get too off topic on Dart+. I know this forum is not about DU.

But the impact of the Dart+ design should not be trivialised regarding its future impact for development on this site. You make a huge assumption above that the retaining walls of new Spencer Dock station are deep enough for future development. They absolutely are not. Period. They are not.

I haven't seen any realistic plausible solutions to facilitate DU in future. People just keep saying "ah it's grand", "we'll just tunnel over here instead", "sure it's not really in the way". It's not really good enough.

If the impact of this Dart+ design is that DU won't happen in its current form, then fine. Let's have a separate discussion about that. But let's not ignore that reality either.

Pete_Cavan

https://www.boards.ie/discussion/comment/119419702#Comment_119419702

The "realistic plausible solutions to facilitate DU in future" is obvious, relocate the terminus back to the existing Docklands station temporarily and do what is necessary. As stated before, the area in which the new SD station is located is going to have to change from a level station to a sloping approach to the future station regardless, there is no realistic plausible solution avoiding this.

It is not unreasonable to think that the retaining walls might be deep enough, they will go below the station level anyway. If not deep enough, sink a new row of secant piles to the required depth, without the platforms there should be space for them to move in to create a narrower channel for tracks only.

And dont be dismissing others with "ah it's grand" when nobody said that. You are the one with the overly dramatic "DU is (un)officially dead with this plan" and "Therefore the DU is not possible anymore" despite not having the proof you seem to expect from others.

brianc89

https://www.boards.ie/discussion/comment/119419795#Comment_119419795

Haha yes I'm definitely like a dog with a bone on this point. In my defence, I've really had to fight for people to see my point! And apologies for dismissing you or others.

Personally, I don't buy the argument that digging up this station in future is acceptable or in the least bit likely to happen. This was the very base for my argument. I simply don't believe this will ever happen, hence DU being (un)officially dead.

Pete_Cavan

https://www.boards.ie/discussion/comment/119419860#Comment_119419860

DU may not happen, but if that's the case, I think it is more likely to be due to the general refusal to invest in public transport here than disruption caused at the new Spencer Dock station. I still think there are solutions for the latter not sure about the former.

gjim

https://www.boards.ie/discussion/comment/119418001#Comment_119418001

We're talking about 15 or 20 years or so before they even consider starting DU. So, after 15 years of use, Spencer Dock (or any station in or with tracks in the area north of Sheriff St.) will have to be closed for a year say to accommodate DU works. I think it's a reasonable call.

Spencer Dock station is a relatively simple project. The Sheriff st bridgework exists and is currently used for coaches and up to 50 years ago was used for trains. The engineering involved in Spencer dock station is trivial compared to that for DU - lower the ground under the Sheriff St arches by a metre or so to accommodate catenaries and reinstate a couple of hundred meters of tracks plus platforms.

Given the need to accommodate up to 16 trains an hour from DART W and SW somewhere in the centre and Connolly doesn't have the capacity, then choices are a bit limited. Where else can these trains terminate? The advantage over building a "temporary Docklands Station 2" to support DARTs via Drumcondra is that this station will be fully integrated with Luas and will integrate both canal and Drumcondra paths. And keeping Docklands and adding a docklands 2 wouldn't solve the problem you raise - which is that service to these stations would be interrupted during DU construction anyway. Also Spencer Dock station's location is far better

https://www.boards.ie/discussion/comment/119418022#Comment_119418022

Spencer Dock station won't be 10m below ground? It's at slightly below ground level - Sheriff St is actually more 3m above ground level - the tracks will run under the arches you see below:

brianc89

https://www.boards.ie/discussion/comment/119420114#Comment_119420114

@gjim, after two days of insisting I was wrong and that I was imagining things in my head, it's nice of you to finally acknowledge I was right.

The new Spencer Dock will need to be "dug up" to facilitate DU in future.

In other words, we dig up version 2 of Spencer Dock and build a 'temporary' version 3 to use for a few years while the EPIC FINALE of version 4 is constructed. Not going to happen.

The RO docs show a level difference of 9m between Sheriff Street and the proposed platform which doesn't include foundations, so closer to 10m. But it's all relative to something so let's not fall out over this point!

specialbyte

At Spencer Dock station here's some information that might be helpful for a rough estimated guess. Unfortunately I can't find my copy of the original DU railway order application.

For the DART+ West RO the structures diagrams for Spencer Dock and the Zone B linear works diagrams give us some useful information to make some educated guesses.

The only reference I can find to the old portal for DU in this area is this render from one of the DART Underground promotional videos. The key part is that the DU portal is completely covered from roughly inline with Hawthorne Avenue in East Wall.

From the point where the old DU route was covered it is about 300m to Sheriff Street Bridge. In DART+ West RO at Sheriff Street Bridge are the new platforms. From the two linked docs above we know the track level will be a -3.3m and the foundations will stretch to roughly -6m. For DART+ West the Spencer Dock station is far below the water line so it will effectively be designed like a giant bathtub to keep the groundwater out. In section 5.1.3 of the DART+ Tunnel Options Report the max allowed gradient is 3.5% over short distances, which is 1:29m. Taking a rough guess in those 300m of distance the DART+ tunnel could drop another roughly 10m. With that kind of drop it is still possible that the TBM could be far enough below the proposed Spencer Dock station that you wouldn't need to rip it all out. It would likely mean you'll need to mine out the Spencer Dock Underground station, which might not even be possible without closing the train station and Luas line.

There is probably enough space to squeeze all of this in and include DART+ Tunnel / DART Underground in future, but it will be a tight enough squeeze. They are 100% painting themselves into a corner.

Anyway, the NTA is dead-set against doing DART+ Tunnel anytime soon, including removing it from the current transport strategy. Something that the Green Party transport minister is surprisingly okay with for some reason.

TBH I want them to build something. Anything. I'd rather they do this plan now rather than debate and study every possible option now, even if that makes DART+ Tunnel more complicated. I didn't hold that opinion 2-3 years ago. However, we need to get something done. Anything is better than nothing at this stage.

gjim

https://www.boards.ie/discussion/comment/119420512#Comment_119420512

I don't know how you've read that I've agreed that "The new Spencer Dock will need to be dug up to facilitate DU in future" from what I wrote? Maybe you should read it again because I neither said that or implied it? Or compare what I've been saying with what specialbyte has written which apparently you "like" - even though they re-iterate my claim the DU tunnel will start at Hawthorn Av and not at Sheriff St. as you claimed and that there is room for the DU tunnel to get under the proposed Spencer Dock station.

brianc89

https://www.boards.ie/discussion/comment/119421646#Comment_119421646

I like specialbyte's post because they address the points I've raised in a constructive manner. Rather than you telling me I'm imagining things.

At Hawthorne Avenue the wall either side of the railway is c. 3-4m high, therefore you're not actually below ground at that point. You've less room to drop the gradient than you're assuming.

It is not clear, at all, if there is enough space for a future DU tunnel to get under Spencer Dock. None of this is properly addressed in the Dart+ RO or DU docs.

You are being extremely rude at this stage refusing to acknowledge the issue.

Anyway it's clear we need to move on. Any plan is better than no plan, even if we're shooting ourselves in the foot for future development. But we'll never know because we're just going to ignore it and hope for the best....

MyLove4Satan

https://www.boards.ie/discussion/comment/119419099#Comment_119419099

Thanks and I agree. I never considered that the Howth service will function like a connecting shuttle to Spencer Dock.

brianc89

https://www.boards.ie/discussion/comment/119421176#Comment_119421176

Thanks for your helpful response yesterday.

Just to firm up some numbers, the Zone A document in the RO shows the height of the Northern line spur (around Ossory Road) to be +7m. It needs to drop to -6m just to clear the foundations of Spencer Dock line and then another 5m (?) for the actual height of the tunnel.

You actually need enough of a run to drop 18m (from +7m to -11m). It is far from certain if this is possible.

GerardKeating

https://www.boards.ie/discussion/comment/119422115#Comment_119422115

For the Howth Service, they should make it a seperate line, extending it under the Northern line and travel inland to link with Metro north, so we would have a line running from Howth to Santry, via Howth Junction, Coolock, Beaumont Hospital, Metro North, and DCU perhaps.

Pete_Cavan

I think it is almost certain that the new Spencer Dock station will need to close for a period to facilitate the tunnel. The biggest issue with that is providing an alternative terminus, if one is available (i.e. the current Docklands station), then I dont see the big issue. The excavation and retaining walls built for the new station will still be of benefit for the tunnel works, they will be starting from a lower level. They just need to strip out the escalators/stairs, the platforms and tracks/trackbed before digging down deeper plus any necessary retaining strucutres. The key things appear to me to be having an alternative location (any future uses of the Docklands station site should be temporary) and not launching the TBM from here as it would require much more space for a lot longer time.

I could even see the new station building itself being reused after the tunnel project. The future tunnel station would likely stretch back under Mayor Street anyway so the building from street level up could still be used as a northern entrance. The building will have a large void underneath so the new track alignments just have to avoid its strucutural elements. The new station wont be wasted money, much of the cost can be offset against reduced works later and the station will likely be use for 20+ years so will have justified its cost.

murphaph

How far away is DART+ for Hazel hatch etc? Surely the existing Docklands station provides enough city centre termination capacity for just the Maynooth line.