DART underground - options

CatInABox · 16-06-2026 09:16AM

Been a while since there's been a post in here, but there was some news that's possibly interesting for Dart Underground, only in a speculative sense mind you, but I thought that I'd put it in here anyway.

Clontarf Golf Club have recently voted to agree a sale to Cairn Homes, subject to DCC rezoning the 70ish acres of land to residential. Paywalled article here:

https://www.businesspost.ie/companies/clontarf-golf-course-members-vote-to-relocate-in-cairn-homes-deal/

From my perspective, the Clontarf Golf Club lands, right next to the Northern Line tracks, would be an ideal location for a tunnel portal for Dart Underground. This would also avoid the need to alter two bridges, one over the Howth Road, and one over Clontarf Road, where the current bridge is a protected structure, which would greatly help the Four North project.

Downsides of course, what with the extra tunneling, and the fact that the route from there into the city and out the other side isn't as obvious as the tunnel portal being at Docklands, but there's enough upsides that I wonder will the Four North consultation raise it as an option to consider.

Of course, this is a bit moot anyway, what with the current plan being totally up in the air since the Rail Report has seemingly decided that any tunnel should now also include intercity trains….

loco_scolo · 16-06-2026 09:37AM

https://www.boards.ie/discussion/comment/124554259#Comment_124554259

Thanks for sharing. That's been on the cards for a while.

It has always been my biggest concern that without a proper assessment of the previous DU plan, and a definitive conclusion about feasibility at Spencer Dock (post Dart+), we could end up needing those lands.

Meanwhile Irish Rail are walking blind, and allowed apartments to be constructed. This may lead to an even more expensive solution for a tunnel.

bk · 16-06-2026 09:39AM

https://www.boards.ie/discussion/comment/124554259#Comment_124554259

It is deferred until post 2042. Though who knows when after 2042 it would happen and what it might look like.

I don’t think Cairn homes will wait around until then for it to be built. What will be perhaps more interesting is how this residential development might impact potential quad tracking.

CatInABox · 16-06-2026 10:31AM

https://www.boards.ie/discussion/comment/124554326#Comment_124554326

Cairn homes will want to fire ahead with it as soon as possible, but there's a load of issues still to face.

DCC have a lot of power with this land, as first they'd have to rezone it, and then they'd actually need to agree to give over the land itself, as DCC own 60 of the 72 acres.

Plenty of ways in which that leverage could be brought to bear to get a deal that includes an area reserved for a tunnel portal.

murphaph · 16-06-2026 10:43AM

https://www.boards.ie/discussion/comment/124554459#Comment_124554459

Only if Irish Rail/TII etc. are not asleep at the wheel and insist on protecting the alignment and a possible tunnel portal area. History suggests that is an optimistic outlook :-(

I feel this development should make quad tracking and a tunnel much easier but given our track record (pun intended), it will do the opposite. At least as a golf course it is de facto protected. Cairn Homes will want to maximise every square metre of development land.

bk · 16-06-2026 11:51AM

Fun fact, most of the Golf Course is actually owned by DCC and just leased to the club!

Irish Rail also own 2 acres of it, I believe mostly along the track and also North at the site of the old railway station. I think there is plenty of space for quad tracking without being impacted by the development. Though hopefully IR are looking at this carefully.

As an aside, I’d love to see them move Killester station, back South of Collins Avenue or at least under it. Would also make for a great place to integrate with the Cairns Home development and would much better integrate with the N4 and H bus routes.

However as a DU portal, I think they would struggle legally from blocking the development, given that DU is currently suspended, likely decades from happening and this site has never been considered as a location for DU, the DART+ Tunnel report had dozens of options, but non of them included this site.

I doubt a judge would allow you to block such a development for decades based on such shaky plans.

Personally I don’t think this location makes much sense, it would add greatly to the cost with a much longer tunnel and you would miss Clontarf Road station. Having recently looked at the options near by Spencer Dock, I believe there are still much easier and cheaper options to build it around there, without needing to go all the way to Clontarf Golf Course.

CatInABox · 16-06-2026 12:20PM

https://www.boards.ie/discussion/comment/124554694#Comment_124554694

I do think that this isn't the most likely outcome, but it's an interesting thought experiment. I can pretty easily think of ways in which to justify a CGC tunnel portal rather than a docklands tunnel portal, but even with that, I do think that it's a bit far fetched myself.

murphaph · 16-06-2026 02:25PM

Probably right. What I really liked about CGC as a portal location was the ability to serve Connolly with an underground station.

CatInABox · 16-06-2026 03:11PM

https://www.boards.ie/discussion/comment/124555184#Comment_124555184

Yes, it'd be a lot easier to do a Connolly>Pearse>SSG>Houston route, but it would increase the cost significantly.

Would the Cost/Benefit ratio actually increase afterwards, despite the extra cost? I think it'd be possible to make that argument.

Perhaps, post Mertolink and post Dart+, the Irish people would see it as necessary, and worth the cost.

murphaph · 16-06-2026 05:33PM

https://www.boards.ie/discussion/comment/124555308#Comment_124555308

We always do infrastructure for slow learners don't we? It's tiresome at this stage. DU will be built some day for all the obvious reasons that folks around here are only too aware of. We will end up building the most expensive version of it possible though, because we will wait until all the best land for launching TBMs is developed and end up buying apartment blocks to level to make way for them, just like with MetroLink at Tara. Crazy not to have a 30+ year masterplan and just CPO the land now for anything in it.

PlatformNine · 18-06-2026 10:17PM

I've been a fan of a CGC portal for a while now and I think there are some advantages to a CGC portal over an SD portal.

First for FourNorth, with the space constraints, I would be surprised if the plan is for four platform stations like on the Kildare line. I am expecting station designed very similar to Kylemore with the two fast lines not having platforms, or if the space is really a problem maybe even just a single island platform for both up and down DARTs. A CGC platform I think would work better with this as the DART lines would be the two western tracks which works better given the position of the through platforms at Connolly (which is important with the current timelines for 4N and DU). An SD portal would either need the DART lines to be the eastern two tracks or would need a complicated grade separated junction that there probably just isn't the space around Connolly for. (though, there are still advantage to the eastern two lines being DART lines, such as Howth branch access and SD being a DART terminus).

Then for DU itself, I think there is some advantages to the possible routes. Most importantly I think a CGC portal allows for a Connolly DU station, which means DU would connect Dublin's two main terminal stations. While this connection doesn't have to be served by DU (a second metro could also work), I think it is an important connection and DU is a good way to do it. I also don't think it has to be longer/more expensive, a Heuston - Christ Church - Tara - Connolly - CGC Route I think would be similar in length because it is more direct and still maintain many of the same connections.

Now that's not to say an SD portal is a bad choice (at least ignoring any complications from the D+W SD station), just that there are at least some good reasons to consider a CGC portal.

bk · 19-06-2026 12:32PM

https://www.boards.ie/discussion/comment/124561800#Comment_124561800

if you really want to serve Connolly Station, one of the options that the DART+ Tunnel report looked at was two different lines that terminate under Connolly!

As in there is no connection or portal up to the Northern line. So DART+ SW trains would stop underground under Heuston and then also stop under Connolly, but then turn back under Connolly.

Interestingly one of the lines went North of the Liffey with a stop on O’Connell St near Metrolink. It had the advantage of being one of the shortest tunnel options.

I know this wouldn’t have all of the operational advantages of the original DU, but it could still work well, it would certainly be the cheapest option, get you your Connelly Station and avoids the SD issues.

As an aside, you could put this underground station between Connolly and Spencer Dock, so you could potentially link the two stations with underground passages. That would be very nice.

I’m not saying we should do this, but just an interesting thought.

PlatformNine · 19-06-2026 03:19PM

https://www.boards.ie/discussion/comment/124563136#Comment_124563136

The terminating station option is interesting but part of me feels like it would somewhat defeat the purpose of DU?

I should give the D+Tunnel report a proper read through, I have read bits an pieces but not the option selection stage. I didn't realise how many different options were considered, and on a quick glance some of them a quite interesting.

I will also be curious to see if/when they do another route selection what options wil be considered and how many of them will be re-evaluated. Especially if they keep trying to push it as a mixed use tunnel.

OisinCooke · 19-06-2026 04:54PM

I agree with @PlatformNine , I am also quite favourably disposed toward an eastern tunnel portal at Clontarf Golf Club. I think it is an easy place to do it, and is also independent of which side of the railway the two slow lines end up post-FourNorth.

In terms of Clontarf Road, it could be added to the tunnel line as a cut and cover station, built in the car park of the existing station (with only small and temporary land take required from the Clontarf Sports Grounds, which I believe are Dublin City Council owned anyway.

When it comes to serving Connolly instead of Spencer Dock, I don’t mind this idea, and definitely think it serves a great purpose of a through-running DART tunnel while also very helpfully linking our two main termini. I would strongly believe though that a direct Metrolink connection is still required, be that at Tara, Stephen’s Green, or even O’Connell Street.

The original DART Underground route was simply too perfect to not at least be strongly considered for the CDCT. Connections at Stephen’s Green to Metro and Luas, Pearse to the other DART line (a perfect location for this type of connection in my opinion), and Spencer Dock for Luas, the IFSC, and outer commuter services are just brilliant assets to have.

Speaking of stations, I believe Heuston, and maybe St Stephen’s Green (purely from a technical standpoint - it would be veeeery hard to get this through planning without objections) are the only stations that are doable as cut-and-cover. The rest will have to be mined, although Spencer Dock could be done as a mix to save costs, depending on where it was built. Again Clontarf Road (if included) could also be cut-and-cover built.

Now a portal at Clontarf Golf Club would make the tunnel longer than the selected route from the most recent options report, but not longer than the original plan, which put the western portal all the way out at Inchicore. I believe the new plan was for the western portal to be placed in Heuston (very tricky and unlikely) or along the Con Colbert Road (with a slewing of that road to the north slightly) saving 2km off the tunnel length. This 2km would then cover nearly all of the extra distance between Spencer Dock and the CGC lands, making the tunnel length not a huge issue. Besides once the machine is in the ground, it’s not as expensive as you’d think to keep it tunnelling longer.

The only issue then price wise would be the mined stations. Is there a world where maybe the line opens with stations only at Heuston, Stephen’s Green, and Pearse, but with provision (and an actual pipeline for construction) for stations to be added at Christchurch and Spencer Dock as infill?

At the end of the day, this is one of the most critical infrastructure project on the rail network, and I’d argue in this country, so we should be prepared to go the whole hog and get the most benefit we can. No half-arsing the job this time. If it costs as much as Metrolink, then so be it, it’ll give us the effectively 2 metro-frequency lines through the city and I think that’s is worth the price.

KrisW1001 · 19-06-2026 06:30PM

I believe it was @bk who suggested having the tunnel connect to the Western line rather than the Northern in order to avoid the problems of height differences in the docklands. If that were done, here’s what I think you’d be able to do in terms of services, with MetroLink included: There’s still an X, but it‘s formed by an Eastern line (current) and Western line (W-tunnel-SW):

“Docklands” is a new deep station. “Spencer Dock” is the DART+ West station. These would be close enough for a walking connection.

(I’m not filling in every station - you get the idea. Boldface indicates a terminal station for some service or other)

CatInABox · 19-06-2026 07:14PM

https://www.boards.ie/discussion/comment/124563861#Comment_124563861

Just FYI, any station that would be developed near an existing tunnel, like at SSG would be a mined out station due to the required depth.

Outside of those stations that must be deep due to the Mertolink line, realistically, most dart stations within Dublin city centre will be mined out, as the length of the platforms really restrict where you can fit a cut and cover site.

Also, a station at Clontarf would also be a deep mined station, as it's right next to the Dublin port tunnel.

OisinCooke · 19-06-2026 08:41PM

https://www.boards.ie/discussion/comment/124564144#Comment_124564144

Yes ok that’s a very good point, I hadn’t considered that… I suppose then Heuston is the only one that could be done cut and cover. Even then though proximity to the Liffey could cause drainage issues depending on the exact site of the station so maybe that’s moot too.

This might be very expensive…

I still think it’s worth it.

CatInABox · 19-06-2026 09:07PM

https://www.boards.ie/discussion/comment/124564397#Comment_124564397

Yes, the cost of this is going to be massive, but on the other side of the ledger, the potential benefits dwarf the costs.

The sticker price is what people are going to talk about though, although hopefully a successful Mertolink project changes people's minds

thosewhoknow · 19-06-2026 10:11PM

Not including the Spencer Dock site, Church Road Jct/Docklands station site is ~14 acres. That should be plenty of room for a DU portal, and it doesn't have the Port Tunnel in the way like at Clontarf.

DART underground - options

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