back to article The Eigiau Dam Disaster: Deluges and deceit at the dawn of hydroelectric power

They say that it is the history on one's doorstep which is most often overlooked. So it is with my latest piece for El Reg's Geek's Guide to Britain which concerns events in a quiet Welsh village that I called home between the ages of five and 18. My father started work at the Aluminium Corporation Ltd plant in Dolgarrog in …

  1. Korev Silver badge

    Fascinating and sad.

    Thanks for the article Alun -->

    1. Red Ted

      Yes, very good.

      It was the last dam failure in the UK, I think, although the Canal and River Trust nearly changed that in 2019 with the Toddbrook Reservoir!

      I have come across Henry Jack in other bits of history of North Wales and he seems to have been a thoroughly unpleasant man.

      The North Wales Power and Traction Co. Ltd. has an entertainingly turbulent history of its own. Originally they started out as promoters of a electric railway and are responsible for the "Bridge to nowhere" over the road when you enter Beddgelert from the south.

      1. EvilDrSmith Silver badge

        Good Article!

        Not the last dam failure in the UK, though - though might be the last with fatalities.

        Defra / the Environment Agency have published a lessons from Historical dam incidents document:

        Which is quite an interesting read, if you like this sort of thing.

      2. PRR Bronze badge

        In the US, the Johnstown Flood of 1889 would seem to be a similar warning. Thousands killed, town destroyed. It is very well known in US culture, and the site is well marked and preserved as the Johnstown Flood National Memorial.

        > "The Dolgarrog flood and the failure of the Skelmorlie dam ..., provided the impetus for the 1930 Reservoirs...Act, ...a qualified civil engineer ....any large dam ... 22.7 million litres a thorough inspection..."

        At Johnstown the dam owners were well insulated from responsibility, and certainly were not at-fault. This was such an outrage that US courts looked to Rylands v. Fletcher, a British common-law precedent supporting liability, still a debated doctrine.

        > "It was the last dam failure in the UK..."

        The logistics of design and inspection encouraged large numbers of dams and impoundments just small enough to avoid design and inspection requirements, yet large enough to do some damage when (not really "if") they fail. The dam at Austin Texas failed twice. One at Austin Pennsylvania failed. As late as 1972 the Canyon Lake Dam and Buffalo Creek Flood failures killed hundreds. 1977 a different dam near Johnstown failed killing 40. 13,000 head of cattle died at Teton Dam.

    2. Tom 7 Silver badge

      Water is devastating stuff. I lived near a village called Wray which suffered a devastating flood in 1967 purely from an angry rainstorm. Where I lived we had a river ran through the bottom of our garden that shared the hilltops that fed the Wray flood and swelled from a 1' deep 10' wide stream to a raging 60' wide and 20' deep torrent of full grown trees and massive rocks in a matter of a couple of hours and re-wrote the river landscape for miles. No-one died here though, many sheep met their doom and a cat and kittens survived in car engine bay that was swept 5 miles down stream. If you've never seen anything like this its almost impossible to envisage the power and destruction water can wreak. All I can say is those people at the cinema that night were lucky a couple of rocks didnt jam in the wrong place and re-direct the flow to their detriment. Just down stream from our house the 60' wide river valley was moved a hundred yards to the left due to the bank collapsing (we think - it wasn't there in the morning) and at other points thousands of tons of rock had simply been brushed away.

    3. Dave559 Silver badge

      Yes, a really interesting article. I know about the aluminium smelter + hydro schemes at Kinlochleven and Fort William in Scotland, but never knew there was similar in Wales. It makes sense when you think of it, though, similar landscapes and rainfall!

  2. Bogbody

    Fantastic article. I was bought up just to the West of that area - in sight of Yr Wyddfa.

  3. Anonymous Coward
    Anonymous Coward

    Terrific article

    Thank-you, I had never heard of this disaster so thank you for the piece.

  4. Franco Silver badge

    I never knew until recently just how many hydroelectric schemes in the UK were originally for aluminium production.

    I'm planning to do the West Highland Way this year and there's a very similar setup near Kinlochleven, the owners were in a bit of trouble lately over broken promises to the local community. It's the last remaining smelter in the UK apparently

    1. Tom 7 Silver badge

      The broken promises are familiar. Its far too easy in this country to avoid your responsibilities - want to dig an open cast mine, sure just make sure you re-wild it afterwards. 30 years later the re-wilding responsibility is owned by a shell company and no-one can remember who allowed this shit to happen.

      1. Martin an gof Silver badge

        Sometimes it works, but you do have to be patient. The Ffos y Fran opencast near Merthyr has made a positive long-term difference to that part of the industrially-devastated landscape, but in the short and medium term while the extraction is being carried out there is a lot of disruption.

        Around here we had a lot more deep mines than opencast, but even they have a lot of effect at ground level. Penallta colliery, a few miles down the railway line from Ffos y Fran, is now a country park.


    2. Binraider Silver badge

      The former Wylfa Nuclear power station's output was majority used for aluminium production too. The nuke outlived the aluminium foundry of course, offshore production and shipping it back here became cheaper than making it local.

  5. Eclectic Man Silver badge


    I hope that the geology and science of dam building has improved greatly since then.

    When I worked with the UK's Ordnance Survey, the man I worked for remembered the staff who had found the old maps of the mountains by Aberfan, showing where all the mountainside streams had been. When the spoil from the local mine was piled against the hillside, it effectively blocked or buried these streams, so when there was heavy rain (an inevitable event in Wales), the pile of spoil was undermined and unstable and crashed down on the village, including the junior school.

    It is all very well to blame the contractors, but he people who plan these major geological structures are responsible too.


    In the Jack Nicholson film 'Chinatown' I recall that the eventual plot is about a geologist objecting to a dam being built due to the porous rock of the lake bed which would mean the dam would be undermined and fail.


    1. Snake Silver badge

      Re: Jack Nicholson

      "In the Jack Nicholson film 'Chinatown' I recall that the eventual plot is about a geologist objecting to a dam being built due to the porous rock of the lake bed which would mean the dam would be undermined and fail."

      Too late, it happened in real life a long time ago

    2. Martin an gof Silver badge

      Re: Geology

      The coal tips of Wales, particularly of the South Wales valleys - though many have been "landscaped" or even moved in their entireties over the years - are still a problem. This last wet winter has been a particular problem and money needs to be spent to sort many similar issues out.

      Regarding Aberfan, people remember the death and destruction (and a visit to the cemetery is sobering) but may not be aware that the government of the day refused to remove the remaining waste from above the village - apparently it was now safe - unless a contribution of £150,000 was made from the money sent in by well-wishers to help support the community.

      As for Dolgarrog, it is a disaster little remembered outside that part of North Wales, but there have been major stories over the years, for example this and this from 2015 and this from 2017.

      I'm pretty certain a very recent (earlier this year) edition of Heno (S4C's equivalent of The One Show) covered the topic too, but I can't find reference to it now.


      1. gryphon

        Re: Geology

        Aberfan cemetery. Yes, you get a very strange feeling there. My mother took us in 83 I think it was when we happened to be on holiday in Wales. Am I right in remembering that there were pictures of the children on the graves in the Russian manner?

        Another strange place, although not for such sad reasons, is Glastonbury Tor. Was up there with nobody else around, could see for miles obviously and there was a bank of cloud about 10 miles away in a complete circle around it. Somewhat eery even though it was right in the middle of a bright summer day.

  6. karlkarl Silver badge

    A really interesting article. Thanks for that!

  7. J.G.Harston Silver badge

    Where is it?

    lat&long is ok, but it's grid references that are more useful.

    1. John Brown (no body) Silver badge

      Re: Where is it?

      If you put the name of the village into Google or your search engine of choice, there a pretty good chance there will be a link to the one and only place in the world by that name. Or. better yet, put the name into a mapping programme or SatNav.

      It's possible that by using Google from a UK IP address, that I only saw the village of Dolgarrog as results on the first page, but I suspect it's because, like Tigger (or the Highlander), there is only one.

  8. Snake Silver badge

    Interesting article!

    Thank you for, not only the article, but the beautiful high-quality photos that accompanied it.

    From both the description and the photos, in the United States we wouldn't call the project so much of a "dam" but a "levee". And that, in a nutshell, is the source of the problem: they treated the design, development and construction of the project as a locally-sourced levee, with little to no thought of flood control, foundational strength and long-term stability under extreme conditions. Just put up the 'wall', the levee, and, seeing that it would be described as a "low head dam" (a water construct with a minimal vertical change between surfaces, which the U.S. has now identified as full of potential dangers that were discounted for decades), nobody gave the possibility of massive carnage if things went wrong much thought.

    And when that happens, when people dismiss risks and dangers, you are almost certain to see the worst sometime in the future. It just seems to be a natural law - entropy has its way and, when you mock it, it turns into a bitter Greek god, it seems. :p

    I will see if I can visit the site when I get over to that side of the pond in the coming future. I have already witnessed Johnstown, Pennsylvania with my own eyes after reading its history, disasters are (sadly?) my personal history highlights.

    1. martinusher Silver badge

      Re: Interesting article!

      Its a product of its time. The 1920s was a time where people had the technology to build decent sized dams but they didn't necessarily have the know-how to site them correctly. We had a local dam built during this period fail in March, 1928 that sent a wall of water down to the ocean killing at least 500 people. (See ).

      1. Snake Silver badge

        Re: Interesting article!

        Yes, I linked to that same article a few hours ago (see my comment higher on the page). The St. Francis has to rank as one of the greatest dam disasters in history, after say Johnstown and Vijont, if not for loss of life but also environmental and technical damage.

      2. Mooseman Silver badge

        Re: Interesting article!

        "people had the technology to build decent sized dams but they didn't necessarily have the know-how to site them correctly"

        I would argue that engineers knew perfectly well where to site dams, but pesky things like science and experience are often over ruled by corporate greed.

    2. Ace2 Silver badge

      Re: Interesting article!

      Johnstown - where when someone mentions “the flood” or “the dam break,” you need to use context to figure out which incident they’re referring to.

      1. Snake Silver badge

        Re: Johnstown

        Lol, very true. Because the break of South Fork Dam led to the Johnstown Flood, but they decided to promote the town's [destruction] and minimize the dam's name.

        And I have a feeling that Carnegie, et al's ownership of the South Fork Hunting and Fishing Club has something directly involved with that...

  9. JWLong

    I learned

    What a leat is today.

    And, this stupid spell check kept changing it to "lead".

    Ah technology, what is there to do with it all.

    Good article tho.

  10. Neil Barnes Silver badge

    Surely at that time the Great Sheffield Flood was in living memory?

    You'd think someone might have remembered it...

  11. Gene Cash Silver badge

    Related to author?

    Looks like the Taylor and Evans families suffered quite a bit. Are the Taylors on the memorial related to the article author?

    Absolutely amazing photography. I feel like I actually walked it myself now.

    1. Martin an gof Silver badge

      Re: Related to author?

      Taylor, as an occupational surname, probably has many unrelated origins. Only Alun could tell us for certain, but as he states that he came to the village aged 5 it's unlikely*, though if he came from not too far away he may well have been related.

      The same is unlikely to be the case with other common anglo-Welsh surnames such as Williams (son of William), Jones, Evans and suchlike. These are merely anglicised versions of the traditional patronymic system where children would often be called after their father's given name, thus farmer John (or more likely in those days, Ioan) might have children known as Ioan ap Ioan and Pedr ap Ioan (for example) which became anglicised to John Jones and Peter Jones when some government official needed to take a census and didn't like the fact that families essentially didn't have surnames.

      "an Gof" is a Cornish occupational surname. You will not find many "Angof", "Engough", "Angove", "Angrove" (or other variants) in the telephone directory, even in Cornwall, but when you do, even they might not be related as just about every village would have had someone trading as "an gof" or in Welsh, "y gof", that is "the (black)smith". This is why the name "Smith" is so common in England.

      One famous an Gof, Myghal (Michael) was a leader of the Cornish rebellion in 1497, but he was hanged for his troubles and there is no record of direct descendants, at least, none that my mother has found, though she does have some tentative evidence to link our branch to one of Myghal's siblings.

      Another famous Angove, Thomas, invented wine-in-a-box in Australia in the 1960s.


      *of course, ultimately we are all related to whichever hominid decided to move out of Africa or, if you prefer, to Adam and Eve

  12. Lars Silver badge

    "Built in 1905 by the North Wales Power and Traction Co. Ltd. it was the largest hydroelectric power station in Britain at the time and is commonly regarded as the oldest grid-connected hydroelectric station in the world."

    Perhaps, it should rather read "and is believed to be one of the oldest Grid-connected hydro-electric stations in the world."

  13. Richard Pennington 1

    Getting there

    B1506 should read B5106.

  14. Martin an gof Silver badge

    Missed a trick

    Excellent article (though I'd be interested to know how those photos were created - they look like heavily sharpened framegrabs from a widescreen video) but at the risk of making it even longer (I love a good long read), it might have been enlightening to some of our non Welsh-speaking colleagues to have explained one or two of those difficult-to-pronounce place names.

    I believe that "Dolgarrog" itself probably refers to a "rocky valley", while "Carnedd" is Welsh for cairn or mound, so alongside a name probably refers to an ancient burial. "Moel" (Foel in the article) means "bare" and is often part of the name of a hill or mountain.

    The really fun one though - and one I've not spotted previously for some unknown reason - is Pen Llithrig y Gwrach. "Pen" has several related meanings but probably simply means "hill" in this context. "Llithrig" means "slippery" or "smooth" (though as this is a mountain we're talking about, could it be a corruption of "Llethrig"; "steep"?). The most common modern use of "Gwrach" is "witch", but I am told (by my dictionary) that it can also refer to many other things, from particular birds, to woodlice, to a respiratory illness (presumably because it made you cough like an old hag), to the "lid" of reed or bracken put on top of a hayrick. Which is it in this case I wonder? "The Witch's Slippery Hill"?

    And what is the origin of "Eigiau"?

    Sorry, somewhat OT, but this sort of thing interests me :-)


    1. virtual insanity

      Re: Missed a trick

      Pen Llithrig y Gwrach I believe roughly translates as peak of the witches hat. If you have seen it, this would make sense as it is a kind of wonky cone shape.

  15. The commentard formerly known as Mister_C


    Have on of these for explaining the leats better than I'd been told previously --->

    I'd only ever been told "they're feeders for the old hydro" when I described them whilst speculating that using an inner tube to float the length might be a relaxing way of filling a sunny day...

  16. skeptical i

    Some more contemporaneous footage

    Thank you for this article and the accompanying photos. In addition to the link included, this one also has contemporaneous footage --

    As noted above, it's stupid dumb luck that the damage wasn't much worse.

  17. Fursty Ferret

    The Register could just write articles like this every day and I'd be happy.

    Waiting for the book.

  18. Man inna barrel

    Unregulated free enterprise at its worst

    These days, people moan about "health and safety gone mad", and various regulations that restrict free enterprise. Stories like this make you realise what it was like for ordinary folks before we had all these rules and regulations. Speaking as an electronic design engineer, I don't mind at all that the products I design have to meet standards for electrical safety. I certainly would not want to live with the thought that I had electrocuted somebody because I did not do my job properly.

    I recently watched a documentary on PBS America, about the building of Grand Central terminal in New York. The original terminal was built by the Vanderbilts, who were the richest family in the USA at the time, based on monopolising railroads over large parts of the USA. The safety record for the first version of the terminal and its adjoining railyard was appalling. As New York grew up around the terminal, people had to cross the tracks with no bridges to help, and were frequently run over. Cornelius Vanderbilt had not the slightest inclination to remedy this situation, because it would cost money with no return on the investment. Eventually, the tracks were rebuilt under the streets, and a magnificent cathedral-like edifice was built over the platforms.

    1. SImon Hobson

      Re: Unregulated free enterprise at its worst

      Indeed. And of course, if the electrical safety standards weren't in place, you (or your employer) would be competing with vendors who had no qualms about shipping poor quality products - though these days it's arguable that such a situation does now exist with "cheap tat" from China.

  19. anothercynic Silver badge

    Ahhh, this disaster!

    I watched the story of this on one of the many engineering shows one finds everywhere these days. It was fascinating. Apparently the concrete/cement used in the Eigiau dam was absolute rubbish, and it was a complete mess. Of course it then had disastrous consequences.

    There are other dams in the world that have had similar consequences, one that I had heard of before is Vajont in Italy where the entire mountain-side collapsed into it, causing a massive tsunami to overspill the dam and cause colossal damage downstream (yet the dam remained intact!), the other is Gleno, where poor working practices caused it to collapse (although some 'revolutionaries' who wanted to sabotage the dam claimed credit with a bomb).

    Anyway, the story was very interesting from an engineering perspective, and thank you very much for popping it into the Geek's Guide! :-)

  20. andy gibson

    Rhiw Bach

    If you're into abandoned stuff, nearby Rhiwbach village and quarry buildings is well worth a look

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