If only I had enough time...... I havn't forgotten I said I'd post some info here on the so-called lost world - and that actually involves Oakeley's Back Vein - or rather Holland's. The story behind it is somewhat involved. Yes, I have plans - they are not small - which is one of the problems. No none of the Upper or Middle quarry workings are flooded, as you rightly say, they are too far up! Flooding is only possible from floor G downwards as that is the water tunnel floor at Pantyrafon, however as the floors rise towards the west the normal water level is somewhere between G and H in the far west. (Cwmorthin Old vein excepted, of course).

Regarding Lefel Ffrench, it was extended purely as a dewatering level many years after it was first started. The major problem facing the Oakeley was that the Great Fall of 1882-3 extended progressively over the years towards the west and Cwmorthin. The Back Vein workings which had extended from roughly half way along the main sink to the Cwmorthin boundary and from floor 1 (Middle quarry ex-Matthews) up to floor 15 (Upper Quarry ex-Hollands) in a roughly triangular form lay, of course, over the Old vein and as a result suffered from the collapse of the Old Vein beneath them. Thus although the Oakeley, would, I am sure, have liked to extend the Back Vein workings, the slate of which was considered good quality, to lower floors, the progressive collapses first of all destroyed the existing south to north access levels and the roofs were so far out of reach as to make new ones almost impossible without driving levels through the walls - a risky business unless the walls were particularly thick. Therefore the only way they could access the lower Back vein was to choose a spot clear of the falls and where the roofs were accessible to make the connecting levels - i.e. the far west end of the Old vein on DE around chambers 32-34 - and then work back towards the east. This was the intention towards the end of the 19th century. The purchase of Cwmorthin by Oakeley put a different complexion on matters and meant that it might be possible to extend westwards as well below the Cwmorthin Back Vein. However the decision to allow Cwmorthin to flood meant that any extensions in that direction would have to proceed very gingerly and well below Cwmorthin's bottom floor. This is why the next Back Vein floor is on G rather than F. It also limited the extent to which the G floor Back Vein chambers could be extended upward until the Cwmorthin Back vein was eventually dewatered.

These are the main falls, there were some earlier as well!
1882-83 "The Great Fall" Walls & chambers 1 to 9 Old vein above floor I and A to G Back Vein above floor 1
1900 Walls & chambers 10-15/16 Old Vein above floor I & H to O Back vein above floor 1
1907 Walls & chambers 16-22 Old Vein above floor I & O,P,Q,R Back Vein above floor 3
(The Back vein chambers were lettered rather than numbered)
1909 Walls & chambers R,S,T1,T2 Back Vein
1912 Walls & chambers 25 to 30 Old vein
Note that most of the Upper quarry Old and Back vein workings were considered almost inaccessible by 1920.

Cheers

Grahami

---

Many thanks for your interesting reply, Graham.

Visited the lost world last week. One can proceed through a series (3) of neat and fairly sizeable chambers roughly eastwards in what I have termed the "main section" These chambers, with the exception of the one we abbed into, appeared closed at the top. Unfortunately, and perhaps predictably, a collapse was met with further in the Oakeley direction, probably where the next chamber along had collapsed into the level.

A cross cut running approx. northward accesses what appears to be a separate area of workings. I don't think this cuts across the drop fault however, but appears to reach another vein, as the character of the rock is rather different here with much evidence of mineralisation, e.g. iron deposits etc. The chambers in this section are small, so one would guess the quarrymen weren't that pleased with rock they encountered here. From memory there is a long level back in the Cwm direction? but it comes to a blind end. Intriguingly, in the Oakeley direction one again meets a collapse in the level.

Note: details are from memory, so please take with a pinch of salt, (or is that slate?) as I left my pen and notepad at the top of the pitch by mistake

---

Looking at the Cwm/Oakeley boundary plan (1900 - 2) if the chamber we dropped into is Z6, as I''ve been lead to believe from other threads, photo albums etc, then we progressed eastwards through Z5 and Z4. Z4 itself is roughly indicated in black on the same plan. Then we went through the wall towards what must be Z3, where the collapse may indicate the presence of chamber Z3 itself. I think this collapse has been climbed over in the past, but we didn't attempt it as it looked a bit tight. According to reports, another section of level was encountered beyond, until a collapse possibly in chamber Z2 was found to be impassable.

A little way beyond this point, the plan shows what appears to be another (northward?) cross cut level in the vicinity of wall Z1, corresponding to what we found between the chambers (Z5 and Z4?) and suggests that the “other Vein” I previously referred to was accessed from this point as well. A collapse we encountered in the eastward heading level in this vein, suggests it extends for an unknown distance in the Oakeley direction, just as the “main section” which is defiantly back vein does. (Was wondering if the workings accessed by the cross cut is actually the North vein, as I can't think of anything else lying north of the back vein)

By the way, saw quite a few of Oakeley's survey marks in the area, including one marking where the “window” breaks into Cwm lake level, thus connecting the two quarries.


(Don't know if this info should actually be PU. please put here if more appropriate)

---

And of course, the progressive collapsing appears to be continuing with the recent fall over the 'front door' of the 'hidden caban' on Fl. G east of the QM caban'. With the stressed passage wall at the 'window' into the chamber at the 'back door' of the caban now threatening to come down anytime. 😞 (As I reported a few weeks ago)

Did you get a look down there, Siriol?

Clive

---

No, Clive, was meaning to, but never managed to get down there this time, as so many other things slate related, such as the lost World and also Corris quarries seemed to get in the way.

Will make a point of looking next time, that's if that area hasn't been obliterated by then 😞

---

Does anyone know what proportion of Oakley and the other Blaenau quarries are now flooded ?

Are we talking an enormous volume of water ?

The percentage for each quarry varies considerably from very little to almost 100%

Oakeley is very flooded! IIRC the workings (in some parts) went down to Floor R (or S?) and it's currently flooded to somewhere between G and H, so 10 floors (or thereabouts) are a bit damp.

That said, there are perhaps 15 floors above the water level - Graham will be better qualified than me to comment on what proportion is flooded, but my guesstimate would be that about half the workings are under water.

Cwmorthin is pretty much dry (because it drains through Oakeley), with the exception of the bottom floor of the Old Vein and the Oakeley workings under the Back Vein (although there is a bit of trapped water higher up, such as in some of the collapsed adits).

Croesor is flooded to adit level, perhaps 1/2 the workings. Rhosydd is similarly flooded to adit level and there's perhaps 1/3 of the workings below water.

Maenofferen continues to get wetter - not sure if it's finished filling up and access is pretty much lost due to the unstopping work. Foty/Bowydd and Llechwedd I've not got surveys for, but certainly have water in the lower levels.


It's basically about drainage. The ideal was to ensure that there was an adit at the bottom of the workings, which would be self-draining in order to avoid having to pay for pumping.

Even for a working halfway up a hill, the ease with which a drainage adit could be driven would often get increasingly difficult as the workings got deeper - witness the succession of deeper drainage levels at Oakeley, for example.

The wetter mines tend to be the larger ones, presumably because they were working better slate and could afford to pump.

In terms of volume of water, it depends what your reference is. If you're planning on draining one with a bucket, then it's an enormous volume!

I guess if you were bored, you could work out an average area for chambers, the height between floors, the number of chambers, add a bit for tunnels and so on - and that would give you an estimated figure.

---

Croesor is flooded to adit level, perhaps 1/2 the workings. Rhosydd is similarly flooded to adit level and there's perhaps 1/3 of the workings below water.

Something I've wondered over for a short while... Is it known why Croesor wasn't gravity drained across to the valley? Seems a relatively straight forward thing to do being low and not too far.

It was proposed and started but not completed.

IIRC from the other side of the valley you can make out the remains of the tip of the abortive dewatering tunnel, just under the main tip.

http://www.aditnow.co.uk/documents/Croesor-Slate-Mine/Croesor-Diagonal-Shaft.pdf 

(currently on hold on the phone with someone so not 100% concentrating!)

---

It was proposed and started but not completed.....

http://www.aditnow.co.uk/documents/Croesor-Slate-Mine/Croesor-Diagonal-Shaft.pdf 

That was the plan. :thumbup:

---

Flooding:
Llechwedd floors I,H,G,F,E,D,C; B is bottom tourist level, "natural" drainage floor is A
Oakeley floors R,Q,P,O,N,M,L,K,I,H, "natural" drainage floor is G
Votty & Bowydd floors M,L,K,I,H,G,F,E,D "natural" drainage floor is C
Maenofferen floors I,H,G,F,E, - drains into Votty


Hard to say what proportion of the whole is flooded in any case - the bottom floors at Llechwedd and Oakeley were relatively small in volume, you also have to take into account workings in more than one vein - normally two in Llechwedd, Votty and Maenofferen and three in some parts of Oakeley. Yes, Oakeley went up to floor 16, but again the topmost floor was relatively small, so it all depends on your definition of proportion!;D

Had Thomas Jones' Deep Level Drainage Scheme actually been instigated then the crippling cost of pumping etc. would have been avoided and who knows what might have been accessible today!

Grahami

---

I have the original (and there is only one in large scale) plan of the Deep Level Drainage Scheme, was given it for Christmas a few years ago ;D;D;D but did not have the literature to go with it...I do have it now though, (thanks Hymac), very interesting, gives ALL the facts and figures about EVERYTHING !!! There were two different tunnels proposed..

---

:o
We wait with baited breath for you to post it here for us to admire!

Pretty please :thumbup:

Yes, please, would like to see that and the text which goes with it :)

And those deepest levels of Oakeley could well be still mostly intact complete with cabans, inclines and stairways. The rock was supposed to have been very good there 😮

---

Sorry 😞 I don't have it here, Mochdre, it's back in Ffestiniog...will be there on Friday so will bring it back with me and upload it then !! :thumbsup:

---

I've only seen the 6-inch scale version, it would be very interesting to see a larger one. Sadly the scheme all fell apart due to inter quarry rivalries and who would benefit most and who would contribute most to the cost, and how it should be paid for etc. then of course there was the idea that electric power could solve everything.....

Edit: For those who can't wait for the gory details, I've uploaded a précis of the scheme which I wrote many years ago. (I though I'd already uploaded it at one time, but I can't find it...) I also did think that Hymac had uploaded the diagrams at one time, but I can't spot them at the moment either. So much for memory;(

Grahami

---

Thanks for that grahami, I believe there were six small copies made, mine is about 24ins square (ish), and the information is on disk...so will have to ask the mrs to do that for me :surrender: Yes, such a shame it never came about.... oh the possibilities....

---

So many times in mining that efforts have failed because people would not work with a neighbor!

:-[:-[:-[ sorry i'm late, but I haven't forgotten, I will do it next couple of day's, found the disk case but it wasn't inside :surrender::surrender::lol::lol: turned up in the side pocket of the lappy case >:(>:( duh

---