Although not strictly a mine, the Penrhyn Quarry did have many tunnels joining the two main sections of the workings together, but also tunnels joining the water balance shafts to the open quarry. I've uploaded part of the 1912 OS 1:2500 map of the quarry so you can see the complexity of the tramways and working faces, but also the newly installed aerial cableways as well as the many tunnel mouths (not always indicated clearly). Two of the vertical balances, George and Douglas can be found towards the left hand side of the sheet, with close by them the inclined water balance up from Red Lion to Twlldyndwr.
I've also added the names of some of the floors.

Enjoy!

Graham

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Sounds interesting... presumably many of these 'tunnels' were quite long since penrhyn is more of a phuge pit with terraces, than a open hillside with terrices.

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I guess so - the longest was the 1840's drainage adit, it's mentioned in Boyd's book. Inside the quarry most were very short. Not clear on the map, but logically present there had to be a connecting level between the Princess May sinc at the top and the Alice sinc near the bottom, since only Princess May had a water balance. With the expansion of the blondins, even depper floors were possible, as long as they lay under the cableways.

Graham

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Interesting... it seems that all these "sincs" have now become one massive pit!
Do you have any similar info about Dinorwig?

Linden

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I presume you mean maps ? Yes, I have a set of the same era for Dinorwic. Floor names there are much more difficult due to the more fragmented nature of the whole operation. And before you ask, no they don't show everything!

Graham

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May I point out the differance between Dinorwig and Penrhyn.

When Penrhyn was astablished the workiers immediatly employed the gallery system, had goo tipping space, + the vein was at an easy angle up the mountainside, so they didn't really have to remove rock or build cuttings etc to get to different floors. They were always very efficiant in removing waste, + new ways to quarry.
Dinorwig started in a similar way, though Dinorwig would appear to have a lot more dykes of hard volcanic rock that Penrhyn, so there was sometimes a need to abandon the gallery system and work the quarry in deep pits, as to work around the harder rock. This meant that many tunnel had to be dug, linking pits etc.. Unfortunatly Dinorwig seemed to run out of tipping space, there by allowing several thousand tonnes of waste slate to slide freely about the side, falling into sincs etc.. blocking off tunnels.
We still haven't got why there is a chamber at Dinorwig (trust me there is, or at least we can't think what else it could be), though no historian I've spoke to has heard of it...

Are there,were there any chambers in Penrhyn... I doubt it, though if a workable deposit was struck whilst digging a tunnel..

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Interesting... it seems that all these "sincs" have now become one massive pit!

Linden

Until working in the pits stopped due to instability of the higher face on one side in late 80s (or very early 90s) there were still 2 pits. In fact there was still a tunnel in between the two which had been enlarged so that large dumper trucks could drive through. As far as I know there are still two pits but the dividing wall has also now become submerged. In the same way as the "one" flooded pit at Dorothea is in fact two in reality.

May I point out the differance between Dinorwig and Penrhyn.

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LAP, may I point out that the person you are conversing with (GrahamI) is one of the most knowledgeable and respected persons on the archaeology and history of the North Wales slate industry. He is probably the most knowledgeable on this site re that area/industry. He has written several books on the subject and is currenttly preparing another (that has become so large it has had to be split into more than one volume).

Yes, I'm aware of that, I've seen some of the books ("Slate o Blaunae"?) for instance. But others visiting this forum may not know it, being not yet posted on this website.
Sorry if the tone sounded a little vigerous!
On a different note...
I wouldn't have thought there'd be any need for underground workings, as unlike Dinorwig.. Penrhyn didn't desperatly need money! Dinorwig being so unsafe to work in by the late 60s that it had to close, where as Penrhyn survived...
I wonder if it'd ever be possible again to reopen Dinorwig on some of the highter evivations. + there's plently of waste in there, a lot could be made of that... I looking into the distant future though.

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I wouldn't have thought there'd be any need for underground workings, as unlike Dinorwig.. Penrhyn didn't desperatly need money! Dinorwig being so unsafe to work in by the late 60s that it had to close, where as Penrhyn survived...
I wonder if it'd ever be possible again to reopen Dinorwig on some of the highter evivations. + there's plently of waste in there, a lot could be made of that... I looking into the distant future though.

That is NOT the reason it closed, it closed because it carried out a massive modernisation scheme (I believe costing over £1M) and basically in so doing overstretched themselves finacially.

I doubt very much it would be allowed to be reopened at all. For two reasons, firstly the presence of the power station (and especially the high pressure water pipes going down not THAT far behind the faces) plus, do not forget that planning restrictions for national parks cover areas that "are overlooked by a national park" now. I think you can safely say Dinorwic is very much overlooked from a national park.

I think you can safely say Dinorwic is very much overlooked from a national park.

Er, yes!

I thought the massive rock fall in 68/69 contributed to Dinorwig's closure? I.e. the cost of that on top of their already stretched finances?

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I wouldn't have thought there'd be any need for underground workings, as unlike Dinorwig.. Penrhyn didn't desperatly need money! Dinorwig being so unsafe to work in by the late 60s that it had to close, where as Penrhyn survived...
I wonder if it'd ever be possible again to reopen Dinorwig on some of the highter evivations. + there's plently of waste in there, a lot could be made of that... I looking into the distant future though.

That is NOT the reason it closed, it closed because it carried out a massive modernisation scheme (I believe costing over £1M) and basically in so doing overstretched themselves finacially.

I doubt very much it would be allowed to be reopened at all. For two reasons, firstly the presence of the power station (and especially the high pressure water pipes going down not THAT far behind the faces) plus, do not forget that planning restrictions for national parks cover areas that "are overlooked by a national park" now. I think you can safely say Dinorwic is very much overlooked from a national park.

Yes, I heard they had to sell a lot of their junk in order to pay their debts!
Though the safety of the sincs did have a major affect, i.e the Garret fall in the late 60s. Something similar happened in Sinc braich bach which has a tip cascading into it, though some parts were still safe to work!
Oddly "Sinch Braich Bach" is one of the bigger sincs (the one described as a bottomless pit) yet bach means small. Presuambly started as a small operation, and got much bigger???
Also.. the chances of the actual quarry being worked again are more or less zereo, though what I meant was the crushing of waste...

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Yes, but it was the finances that closed it ultimately.

Incidentally, I have heard, don't know if it was true, that Dinorwic was (somehow) kept open for a few months more than it would have done due to the impending Prince of Wales Investiture. It being thought that the closure happening before the investiture would have been very bad for publicity, especially as the slate dias and royal chairs were made at the quarry. Does anyone know if this true, or just an "urban myth"

I've heard that!
I believe McAlpines took over in 1969 for a few months. Some locals believe however that McAlpines took over 'just for a short while - in order to let the prise of the land go down, so that the power company could buy it cheaper!
Though this seems a bit silly!

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Yes, I heard they had to sell a lot of their junk in order to pay their debts!
Also.. the chances of the actual quarry being worked again are more or less zereo, though what I meant was the crushing of waste...

Yes, they had a massive scrap drive in mid to late 60s.

I doubt even crushing would be allowed, there is another quarry (sorry, name escapes me, near Waunfawr) just within SNP that had great difficulty getting permission to crush tips even though the tips were very low and mainly hidden behind trees!

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Don't know the exact quarry but it's very near Cilgwyn isn't it?

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I've heard that!
I believe McAlpines took over in 1969 for a few months. Some locals believe however that McAlpines took over 'just for a short while - in order to let the prise of the land go down, so that the power company could buy it cheaper!
Though this seems a bit silly!

Err no, The land was auctioned McAlpines purchased most of it (I heard so no one else could! and be any kind of compeditor for Penrhyn). Subsequently some of the land was leased/sold to CEGB for the power station. As I understand it (and it was the Head of the power station that told me this) that McAlpines still own some of the quarry either side of the central arae through which the power station runs.

You clearly know more than me!
Tell me, did anything actually happen for the time in which McAlpines owned the site? I heard they tried to clear the Garret Fall?

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Don't know the exact quarry but it's very near Cilgwyn isn't it?

There is a quarry near Cilgwyn that is crushing slate. The one I am thinking of is near Waunfawr, in fact south of there near Betws Garmon. I will dig the name out later. It is kind of opposite the Silurian Iron mines.

Now you are getting into the sketchy area of my knowledge. I understood that McAlpines did work under contract to Dinorwic Co. This was for the modernisation plan. Maybe as part of that they did some attempted clearance work. I am reasonably certain they didn't do any work after they bought it though.

Something that has always struck me as odd though. The timing. The quarry closed July 1969. The quarry was auctioned I think in June 1970. Then all of a sudden plans were drawn up they decided on Dinorwic(in fact the CEGB were looking at 4 sites one of which was Cwm Croesor), the plans were submitted to Parliament, and it it was authorised under the "Dinorwic Power Station Act 1974". That all seems very very quick to me! Especially seeing as parliament were involved!