DART underground - options

blanch152

How about a bridge instead, across the Liffey to tie in Docklands Station with Grand Canal dock station? Is that feasible?

That would provide interchangeability between DART West and Dart South.

gjim

A second parallel loop-line bridge requiring the demolition of a swathe of modern docklands buildings? No fecking way. What would it achieve?

We have one high-quality, high-capacity, grade-separated alignment capable of supporting metro-heavy rail in Dublin - the Kildare route out of Hueston (or will have, once 4 tracking is finished). Any tunnel that doesn't extend/build on this alignment would be massively wasteful.

The 2nd best alignment into Dublin is the Northern line - significantly worse than the SW route given the sharing tracks with intercities and other services but at least it's grade-separated with no level crossings unlike the southern coastal and western alignments.

Every few years, we get a report on how to fix core capacity bottlenecks in the DART system and they examine all sorts of crazy connections/alignments. And in the end, they all come up with something like the original Interconnector.

scrabtom

You're surely losing an awful lot of the value of Dart Underground if you put the tie in in Clontarf instead of Spencer Dock.

You're losing the station in the centre of Dublin on the north quays and the tie in with Dart West. If all trains coming through the tunnel have to go north is that not a major lose, you're going from a potential inner orbital that could go all the way from Heuston through the Pearse and then around Drumcondra and Phibbsbrough back to Heuston, or a line that can just go from Heuston through Pearse and then North.

I think if they're doing it they should do it properly and just deal with the disruption and the pain of having to close Spencer Dock for a couple of years, and get the full benefit of the project if it's going to cost 10ish billion as it probably will.

The best solution seems to be to have designed the new Spencer Dock station now to accommodate Dart Underground and paid the extra money now, but they haven't done that.

Am I missing something here?

OisinCooke

https://www.boards.ie/discussion/comment/122422993#Comment_122422993

I would wholeheartedly agree, it’s very much a bite the bullet situation. I wonder though could the tunnel be brought above ground on the site of the current Docklands station… to the east of the new proposed station? A quick dive into the tunnel may not be achievable though in the short length of space.

Could the plans for Spencer Dock station be amended to include two diving platforms in the plans…? Even before the plans for DU are confirmed, the station could still operate with two of its 4 platforms being lower than the other two. Could this be done…?

gjim

Am I missing something here?

I wasn't suggesting losing Spencer Dock Underground? The TBM portal was to be about 300m North of the underground station in the old plans. I'm suggesting moving it further north by about 600m. Having no station between Clontarf and Pease would be daft.

I think if they're doing it they should do it properly and just deal with the disruption and the pain of having to close Spencer Dock for a couple of years, and get the full benefit of the project if it's going to cost 10ish billion as it probably will.

I agree with your attitude. If the country and Dublin in particular is to have decent PT infrastructure, then the general attitude towards disruption needs to change. With ML, two years of Luas disruption would have been a small price to pay for 100+ years of benefits.

I mentioned "less disruption to Spencer Dock" very last and qualified it by saying it might be important for some. I'm more concerned about the suitability of the original portal site given how the North Docklands has been developed over the few decades since the original plans. And having a proper grade-separated/non-crossing tie-in with the northern coastal.

Pete_Cavan

I do see the logic in the tunnel connecting to the above ground network at Clontarf Road. It has operational benefits (both during and post tunnelling) and should be much easier to construct.

The tunnel portal would have to be immediately north of the bridge of Alfie Byrne Road over the Tolka. Not sure why people are talking about EastPoint or looping round anywhere, there's an obvious route there. It would give ~250m of space to work with to accommodate the necessary change in levels. The problem is there are two limiting factors, the DPT and the Tolka. The question is, how deep could the cutting be about the DPT and is that deep enough to then get under the Tolka in the 100m available?

Questions about the vertical alignment aside, Clontarf Road would make sense from the horizontal alignment pov. With the original DU plan, after passing through the new Docklands station going east, the tracks had to swing back slightly west to meet the existing alignment to the Northern Line which again goes east. That S curve in the horizontal alignment, combined with the vertical level change (from under the Liffey to the elevated Northern Line, both fixed levels) made everything very difficult.

If the tunnel goes to Clontarf Road instead, you eliminate that S curve and instead have a more natural alignment. The station box at Docklands (yes there'd still be a station there) wouldn't have to align north/south, it could be rotated slightly (the northern end slightly east, southern end slightly west). This would then help with the alignment south of the Liffey and potentially open up other route options.

Th original DU station at SSG is off the table now (Metrolink will build a standalone station, not like the combined station planned under MN). Also, the owners of a part of the proposed DU station box won a court case allowing them to develop the lands. Alternative station locations can be looked at for a new tunnel plan with a potential different alignment. Ideally, a DART tunnel station would be built at Tara Street which would link two DART lines and Metrolink and become the defacto Dublin Central station. The difficulty with this is the large sewer line but the benefits of such a plan would likely outweigh the additional costs (you save on the cost of an underground station and shorten the tunnel).

bk

The tunnel portal would have to be immediately north of the bridge of
Alfie Byrne Road over the Tolka. Not sure why people are talking about
EastPoint or looping round anywhere, there's an obvious route there. It
would give ~250m of space to work with to accommodate the necessary
change in levels. The problem is there are two limiting factors, the DPT
and the Tolka. The question is, how deep could the cutting be about the
DPT and is that deep enough to then get under the Tolka in the 100m
available?

Well you'd have to go deep under the port tunnel to avoid it, maybe as much as 50 meters down and then only to start immediately coming back up within the space of 200 meters or so after the tunnel! I doubt that would be a possible gradient.

I could be wrong, but I find it quiet telling that the recent DART route options report didn't even consider it. And yes, that report does include one option that runs North of Fairview Park and connects North of Clontarf Road Dart Station.

Pete_Cavan

https://www.boards.ie/discussion/comment/122425217#Comment_122425217

I see now that predictive text gave "about the DPT" instead of "above" which I intended. It would have to be a cutting from around the Clasac building to just before the Tolka and then go underground. Maybe dropping 2.5m below ground level as it crosses the DPT and a further 5m by reaching the Tolka, something like that. That’s just by way of an example, not saying that is definitely possible.

Are you referring to the DART+ Route Options & Feasibility by Jacobs? I only see R21 Heuston – North King Street (King’s Inns Park) – Parnell – Croke Park – Fairview which is rejected early due to poor travel demand, which is hardly surprising given it misses most of the city centre and has poor interconnection opportunities. That high level route is the only reference to Fairview in the report.

The report recommends basically the original DU route, mostly because it says SSG and Pearse stations will be as previous design without further assessment. We know that a SSG station taking a chunk of SSG park (far more required than for Metrolink) is going to face major objections which could kill it. The Pearse proposal is a mined station with cut and cover shafts on sites which have been partially developed recently. Basically the Pearse station as proposed can't be built any more.

By the time Metrolink and DART+ are completed, that report will be more than 10 years old. The city centre will also continue to see development which will affect any potential options. Basically, everything will need to be looked at again but in the context of what sites are available at the time.

bk

https://www.boards.ie/discussion/comment/122426494#Comment_122426494

I see now that predictive text gave "about the DPT" instead of "above"
which I intended. It would have to be a cutting from around the Clasac
building to just before the Tolka and then go underground. Maybe
dropping 2.5m below ground level as it crosses the DPT and a further 5m
by reaching the Tolka, something like that. That’s just by way of an
example, not saying that is definitely possible.

Oh, that would be completely impossible!

The Port Tunnel is barely below the ground there. The portal to the Port Tunnel is just south of Alfie Byrne Road, that is the site where the TBM was turned around. You'd be cutting into the roof of the port tunnel!

You can clearly see it on Google Maps:

And yes, that is the report I'm referring to. What I'm suggesting is the fact that they didn't even list any option in Fairview Park would indicate that the engineers know it isn't possible to do anything at this location because of the port tunnel.

Pete_Cavan

https://www.boards.ie/discussion/comment/122426820#Comment_122426820

The DPT emerges 150m from where I suggested the tracks might be able to go. The tunnel is continuously getting deeper is obviously sufficiently deep under ABR and it's build up. Further back by the rail tracks it is deeper again. The entire section from Fairview Park to where the road emerges was cut and cover, it wasn't done with TBM.

Like I said, its a question of geometry; whether its possible to get to the above ground point to deep enough to pass under the Tolka without interfering with the DPT. You or I don't have the answer to that. There might be sufficient depth available where it crosses the tunnel.

The route options in that report cross the Metrolink tunnel at depth in the city centre with multiple buildings with basements in the vicinity, crossing the DPT close to surface level isn't that big of an issue. That report recommends a route with at least one station location which can't be built now (a very important station as it is the connection to the existing DART line). Other options will have to be looked at.

As I said, the report mentions one route to Fairview and in the matrix it is one of the better performing routes on the Environment and Cost criteria. It is however the worst performing on Travel Demand, which isn't surprising when you consider the proposed route and central stations. There is no indication that they ruled out Fairview due to the DPT.

scrabtom

Sounds like another feasibility study of the possible routes is needed, especially once Metrolink has got through planning.

They shouldn't do it until they actually want to action the results of it, otherwise it'll just be something to make it look like we're making progress on the project. With the pace of development in Dublin City Centre any report will be out of date within a decade or two and have to be done again.

bk

There is no indication that they ruled out Fairview due to the DPT.

The fact that they didn’t include this location, even though it would be a very obvious one, clearly means that the engineers know it isn’t possible due to the DPT. As in it was ruled out from even considering it as it is technically not feasible.

And R21 clearly shows there were considering longer tunnel options and options in the area. This is pretty simple logic!

I worked at East Point when they were building the port tunnel, I can assure you it barely goes under AB road and the rail tracks. There is zero space to cut and cover there!

For the love of god, don’t make me go look up the port tunnel cross sections from the planning application to show you!

bk

As I thought, the DPT was constructed as cut and cover from just north of East Point Businnes Park through the width of Fairview Park and under both Alfie Byrne Road (which was actually raised up) and under the train tracks.

The picture is low quality unfortunately, but you can just about see it here, the one on the left:

picture from this site:

https://www.geocaching.com/geocache/GC4177X

You are not going to be able to cut and cover through that!

Only option would be to go deep under it, but I don’t see how you could come back up before Clontarf Road dart station.

loco_scolo

The entire area in yellow below is undeveloped. A large chunk of that was being kept for future development/completion of the Orbital M50, however that has now been shelved.

There should be plenty of room there for a tunnel to emerge and connect with the Dart Northern Line at Clontarf. The fact it was being kept for a road tunnel would suggest it's technically feasible, despite being on reclaimed land.

L1011

https://www.boards.ie/discussion/comment/122428900#Comment_122428900

You're now just making the rail line have to rollercoaster overground rather than underground

loco_scolo

https://www.boards.ie/discussion/comment/122428990#Comment_122428990

Rollercoaster is a tab dramatic, no?!

Look at a rail map of Paris or London, you'll find plenty examples of "Rollercoasting" lines, mostly where they connect with or traverse above/below other lines.

L1011

https://www.boards.ie/discussion/comment/122429046#Comment_122429046

No, because you appear to have no idea of the vertical scale required here.

Underground third rail lines using [comparatively] light rail stock do not require as much height to cross as a motorway does; and can also handle inclines better.

loco_scolo

https://www.boards.ie/discussion/comment/122429052#Comment_122429052

I have an extremely good understanding of that thanks. I've posted many times on the difficulties the proposed surface Dart Station at Spencer Dock poses for the previous DU plans. Describing at length the various elevations of the Northern Line, proposed Dart Station, Spencer Dock Luas etc and required gradients.

My crayon drawing above is simply that - a crayon drawing for discussion. There is an enormous amount of undeveloped land available there, which was been kept for a Motorway Tunnel. There is, in fact, more space available there (to achieve appropriate gradients and curves) than there is at the Spencer Dock site. The less direct routing is not ideal, but it's only 250-300m longer than the previous plans.

L1011

https://www.boards.ie/discussion/comment/122429363#Comment_122429363

I remember that thread and was basing my claim on that also…

The motorway there was not going to have to rise over the existing motorway and come back down to meet the railway line in a relatively short distance. A railway line would.

You are proposing a rollercoaster unsuitable for conventional trains.

Pete_Cavan

https://www.boards.ie/discussion/comment/122428724#Comment_122428724

As already pointed out to you, the one Fairview route in that report is one of the better performing routes on the Environment and Cost criteria. It was ruled out as it is the worst performing on Travel Demand (hardly surprising when "Parnell" is the only city centre station and it doesn't connect with the existing heavy rail lines in the city centre or with Metrolink).

There is absolutely nothing in the report to indicate that Fairview was ruled out due to the DPT. By your logic, the fact that it was considered at all would indicate that there is some possibility. Also, several of the route options looked at then are likely not possible now (development on part of proposed Pearse shaft site), nevermind in 10+ years time so everything will have to be looked at again, including other possible route options more carefully considered.

bk

https://www.boards.ie/discussion/comment/122429497#Comment_122429497

Err… go look at my next post, DPT is cut and cover right across Fairview Park!

Pete_Cavan

https://www.boards.ie/discussion/comment/122428822#Comment_122428822

That shows the cut and cover through Fairview Park, which I already said was the case. What you see are temporary supports, not the tunnel itself. The excavation there is 20m deep. The top of tunnel is several metres below the surface level we now see.

And I never suggested cut and cover anything through there. I suggested the rail tracks might be able to drop a couple of metres below the existing surface level beside Fairview depot.

Going under the DPT there isn't an option.

bk

https://www.boards.ie/discussion/comment/122429595#Comment_122429595

No it isn't! The top of the tunnel is very close to the ground between Alfie Byrne Road and the train tracks. ABR was raised up 2m's over the tunnel! The tunnel is almost directly below the train tracks.

TII literally have this area as a restricted zone for developments. There is absolutely no way you could cut and cover into the top of the port tunnel 2.5 meters like you claim.

It is a wild and crazy idea!

Going under the DPT there isn't an option.

Yes, that is my point, I don't think connecting at Fairview Park and before Clontarf Road is technically possible at all, above or below, which is why no such option is given in the options report!

Paul2019

Hard to say but it doesn't look like there's much wriggle room there, unfortunately.

bk

The top of the tunnel is just 3 meters under the tracks:

https://www.newcivilengineer.com/archive/subsidence-shuts-track-by-dublin-tunnel-02-01-2003/

The arch roof is just 3m below the track bed, which sits on an embankment of sandy clays and silt material.

https://www.lba.london/projects/dublin-port-tunnel/

The completion of the pipe-jack canopy, lying only 3.5m beneath the mainline & local railway system within poor ground conditions and exposed to large tidal influenced, water-table fluctuations was attained with no detrimental effects on the railway system itself.

I've been looking for the planning documents, but can't find them!

I watched the DPT being built, I distinctly remember ABR and parts of Fairview Park being built up over the tunnel, which is just there. If you have been to Fairview Park, their is a small hill in the middle of the park, this is basically built over the tunnel.

loco_scolo

https://www.boards.ie/discussion/comment/122429378#Comment_122429378

There's potentially 1100m to work with for a rail line to clear over the tunnel and descend below the new buildings on Sheriff Street. That's a 2.5% gradient which is more than doable for any train, even considering the curve. The trains will be electrified so handling a gradient won't be an issue.

I don't know enough about this site to claim this is doable, but I think it's worth considering.

L1011

https://www.boards.ie/discussion/comment/122430165#Comment_122430165

Thats not your proposed rollercoaster alignment or height change, though, is it?

loco_scolo

https://www.boards.ie/discussion/comment/122430194#Comment_122430194

I don't think my images are all that different to be honest - it's just to show the general idea of looping a line around this undeveloped part of the Docklands.

As a general idea, do you, or anyone else, have an opinion whether this could be workable?

blanch152

https://www.boards.ie/discussion/comment/122422333#Comment_122422333

From the existing Spencer Dock, take it above canal, cross the Liffey and then elevated along Macken Street to Grand Canal Dock station. Interchange there for Dart South.

No need to demolish any building.

L1011

https://www.boards.ie/discussion/comment/122430276#Comment_122430276

Spencer Dock will be underground. This would be another rollercoaster, and a second loop line bridge will never happen anyway

It would also have no useful connections to the North