National Tunnels Strategy?

A1ACo · 23-10-2025 04:18PM #1

Not ignoring the existing Boards.ie forums regarding the Metrolink and Dart Underground topics etc., are there benefits to discussing Irish national infrastructure Tunnels collectively?

Such as to discuss lessons learned from previous tunnels built in Ireland (and abroad), to inform both potential difficulties and strategic opportunities with planned tunnels?

For example, the rubble mix that comes out of Tunnel Boring Machines (TBM) usually looks pretty finely graded, but could this be fine-tuned(?) or otherwise could the excavations be used as a fill, or stone gabions contents, or even extracted boulders from before TBM works (I doubt it) that could be used for coastal protection works?

Coastal protection works such as foreseen between Greystones and Wicklow. Could such excavations be used in Portrane/ Donabate for coastal protection?

Perhaps depending on the context, more old-fashioned drilling and blasting could be used e.g. Bray Head?!

Maybe the fill be used for filling-in or storing for later use in old quarries, or for new roads and residential schemes, drainage works, or filling-in new areas for ports and harbours?

Some future uses would no doubt also be dictated by the type and quality of the stone and/ or soil excavated.

I’m sure the use and or disposal of fill is mentioned in the various individual Engineering reports for the above planned schemes, but I’ll admit I’ve never looked (yet..).

But I wonder if a high-level national, and long-term overview of national tunnel schemes has ever been done, for potential inter-play and mutual support of these projects?

Maybe a future small project or co-ordination/ facilitation office could help things along?

For example, it has been queried before on these forums could ‘x’ tunnel TBMs be lifted out, and used for ‘y’ tunnel schemes, or the TBMs continue to dig to another new tunnel project location (i.e. in Dublin city centre area), and/ or the projects be aligned so that the project staff and other ancillary equipment can go seamlessly from one scheme to another?

A1ACo · 23-10-2025 04:21PM

Climate Change Adaptions etc.

The way things stand right now, could the Metrolink excavated material go to north County Dublin Coastal protection, and DART+ tunnel ‘pencilled in’ to commence during and just after MetroLink completion and excavations to go to Dublin Port infill and North Wicklow Coastal Protection,.. followed by a new Bray Head Tunnel and excavated materials for coastal protection right there at Bray Head?

Is the plan for the MetroLink excavations/ spoil removal anywhere online and easy to find?

Would a ‘holistic’, NDP (National Development Plan), NPF (National Planning Framework), Climate Action Plan, etc. anchored national strategy be useful?

Existing Tunnels (for comparison/ benchmark):

Dublin Port Tunnel (Road)

Jack Lynch Tunnel (Road)

Kent Station tunnel (Rail)

Phoenix Park Tunnel (Rail)

Bray Head Tunnels (Rail)

Killiney Tunnels (Rail)

Etc.s?

Proposed Tunnels:

MetroLink (Rail)

Dublin Airport (Road (internal operations))

DART+/ DART Underground /Interconnector Tunnel (I’m calling it the U-DART…)

Etc.s?

Problems and considerations that have arisen in the past have included - how wide to make the tunnels e.g. for what height/ type truck limits, fumes (entrance mouth and internally), noise at entrance mouths, etc.

There are a number of chats here under the heading of ‘Tunnels’ but most seem to be tunnel specific, with the most recent it looks like this one:

Luas Tunnels? — boards.ie - Now Ye're Talkin'

And another here that talks about a proposal to dump TBM spoil in Dublin Bay

Proposed dumping of 824,000 tons of Tunnel spoil in Dublin Bay — boards.ie - Now Ye're Talkin'

Where did the fill from the Dublin Port tunnel and Jack Lynch Tunnels go to - illustrate past tasks/ benefits?

plodder · 24-10-2025 08:53PM

Jack Lynch wasn't a bored tunnel. I think a trench was dredged in the river bed and prefabricated sections were just dropped into place.

I remember seeing some of the TBM spoil from the Dublin Port Tunnel. It didn't look anything like the kind of dangerous slurry described in that article. It looked like potentially useful fill that could be used somewhere else, though not so sure for coastal protection.

A1ACo · 25-10-2025 12:30PM

On the coastal protection end of things, I stumbled across an Irish Rail public consultation brochure yesterday sitting on the shelf of a public library, for the 'East Coast Railway Infrastructure Protection Projects: Preferred Scheme for - Bray Head to Greystones North Beach'.

From reading that, and not too sure how old it was, but I think I remember it was discussed in the the last couple of years only, that the works may already be finished for this section.

In that document it mentioned various details for construction, mostly of revetments it seems, and to include:

'Heavier rocks (6-10 tonnes)' and 0.3-1 tonne rocks underlayer, thin layer of gravel, and excavated beach material re-used.

It also mentions excavated debris at the cliff toe that I'm assuming was/is to be reused too.

I wonder could future tunnel projects, whether by TBM or Cut and Cover could provide some or all of these types of material, particularly the 'heavier rocks'…elements?

And not quite the same thing, but is the Shannon (River) to Dublin Water Scheme pipeline to be buried and to lead to lots of spoil?

end of the road · 25-10-2025 09:32PM

ultimately it depends on the geography of what is being bored out.

if it's pure hard rock then yes it could be used for coastal protection, but if it's chalk and soil then really it's not good for much most likely, certainly not coastal protection anyway.

really we will only know when any tunnel anywhere gets the go ahead and investigations of the geography are done, as to what if anything any spoil is good for.

National Tunnels Strategy?

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