Eigiau Dam - unintentional there and back (10.6km / 6.59 miles)
Today was a reminder that not all walks go to plan. I had heard about the Eigiau (Ayg ee ai) Dam from my Taid a few weeks ago and it instantly grabbed me. I researched, studied maps and satellite pictures and thought I had a circular route planned, with a shorter, back up circular route in the bag if I needed it. After it took us 1 hour to drive the first 15 mins of the way there (due to an accident on the A55), I knew that we would be going for the shorter route before we even found the car park. Unfortunately, that was not to be either, as I will explain later on.
Our bad luck really doesn’t take away from this walk as long as you are happy to do either a very long, hilly circular route or a shorter there-and-back. The walking is easy and flat in the section that we completed today (by the time you’ve parked you’ve covered all the height you need to and so you can enjoy a walk in the mountains with minimal effort!) The paths are wide and clear so easy and safe with small children. Mostly though, the location is just incredible. The scenery is beautiful and dramatic with a tragic tale that heightens the atmosphere.
Distance: 10.6km / 6.59 miles (according to the OS map app)
Time taken: 3hrs 1min
Total ascent: 220.80m (OS Map app)
Parking: Yes- free parking up a long, narrow track.
Facilities: None.
Walkers: myself (33 yrs, fat and unfit), Megan (4 years) and Anwen (14 months, in the rucksack).
Map showing the road from Tal Y Bont to the parking area.
To start the walk just head for the dam! You basically follow the same road that you have just driven down. There is a locked gate at the end of the parking area, but there is a style next to it which is always fun when you’re carrying a baby in a rucksack. After crossing the style you have no choice but to follow the track down the hill.
Eigiau Dam.
I suppose this would be a good point to explain the story behind the Eigiau Dam and it’s connection to the Dolgarrog disaster.
Dolgarrog and the Eigiau Dam
In 1907, with aluminium selling for £120 a ton, a new company called the Aluminium Corporation Ltd (ACL) decided that the ideal place for a processing plant was in the Conwy Valley, in the small village of Dolgarrog. Llyn Eigiau, which lies 370m above the valley floor, would be dammed with a 990m long, 8m high concrete wall and a 396m long earth embankment designed to hold 4 million cubic metres of water which would be directed along the Afon Porth Llwyd (Av on Porth Tloo id), a leat, and a pipeline into turbines in the new factory.
Initial success was short-lived. By the end of 1908 aluminium was selling for less than £60 a ton. The undercapitalised ACL promptly failed, as did the contractors building the Eigiau dam, which was only 2/3rds completed. The enterprise was revived in short order by Scottish businessman Kenneth McKenzie Clark with the new ACL being formed in 1909. But it was not until February 1910 that work on the dam at Eigiau restarted, finally finishing in November 1911.
The next 15 years were ones of rapid development for the ACL plant in Dolgarrog and the new model village that sprung up next to it. To keep up with the demand for electricity – public supply started in 1922 to Colwyn Bay, Conwy, and Llandudno, and was later extended to Wrexham and Hawarden near Chester – a new power station, the one you see today, was built next to the aluminium works and another reservoir was built downstream from Eigiau at Coedty (Coidtee) to ensure a steady and reliable source of water. By the mid 1920s the mountains behind Dolgarrog were crisscrossed by a network of leats and tunnels connecting the reservoirs at Eigiau, Cowlyd, Coedty, Dulyn, and Llugwy. All these interconnectors were necessary because although the physical geography of the Carneddau was ideal for hydroelectric schemes, and though North Wales has a reputation for being wet, local rainfall is both too seasonal and too irregular to be relied upon to keep individual reservoirs topped up.
Of course, irregularity can work both ways. The weeks leading up to the night of 2nd November 1925 had seen heavy rain throughout the Carneddau. 25 inches fell in Cwm Eigiau in the five days before the 2nd November. Ten days before, villagers in Dolgarrog had already reported flooding. The ACL said it was down to the Coedty leat overflowing, but the leat into Coedty entered the reservoir at the high watermark - if it overtopped, the reservoir was already full.
When the Eigiau dam failed on 2nd November it was through a blowout at the bottom of the dam, at the place where the first and second phases of construction joined. The blowout started to feed more and more water into the Coedty dam. The floodwaters then overtopped the dam at Coedty and started to wash away the exposed earth embankment on the outside of the dam. Strong winds blowing the length of the valley and forcing water over the dam had done the same at Cowlyd the previous year, and only frantic reinforcing with sandbags had prevented a failure.
The blowout at Eigiau become serious at around 20:45 on 25th November and released some 1.4 million cubic metres of water over the following hour. The torrent scored a channel 20m wide and 3m deep into the ground. 200m from the breach the flood joined the Afon Porth Llwyd which flowed into Llyn Coedty reservoir, 2.5miles downstream.
The overflow at Coedty soon became catastrophic and swept away the last of the earth embankment. This caused the now unsupported concrete core membrane to collapse, leaving a breach 60m wide at the top and 18m wide at the bottom. The resultant wall of water, mud, rock and concrete (estimated at some 1.35 million cubic metres) hit the Northern end of Dolgarrog village sometime between 21:15 and 21:35. Witnesses describe the wall of water as being “50ft wide and quite as high”. Some of the rocks swept down the course weighed more than 500 tonnes.
A large part of the village was swept away including houses on the Machno terrace, the church, church house, sweet shop, butchers and water mains. The water then inundated the aluminium works causing both furnaces to explode, which was witnessed by the local vicar who raised the alarm. He managed to save every man at the works, entering the deep water to save the remaining few who were stranded. If he had not been a man of significant stature at 6ft 7, the death toll could have been many more. A total of 16 people lost their lives that night- 10 adults and 6 children. More people would have died but for the fact it was film night at the village cinema, which was full and, due to being on higher ground, left undamaged by the flood. The last body, that of Mrs Sinott, was not recovered until 10 months after the flood when she was discovered washed up on the mudflats at nearby Tal-Y-Cefn.
“The flow of water from the dams did not cease until mid-morning the following day,” said Gwilym Wyn Roberts, whose mother survived the disaster. “Cows were seen hanging from the trees and the aluminium works were submerged under 5ft of mud,” he added. Fred Brown was the last remaining survivor of the flood but passed away several years ago. He was 14 when the waters came crashing down, claiming the lives of his mother and younger sister. “I heard that my mother had drowned, as well as my 4 year old sister. My father and my elder sister were washed down with the flood and they rescued themselves by crawling over coke wagons.”
2. When we got to the next gate, which wasn’t locked this time although did have a style next to it so I assume it sometimes is, I decided to turn right and head towards the far end of the dam rather that continuing on the track. There was no path at this point and parts were quite muddy and uneven which took some negotiating. I suspect that this area gets pretty boggy in parts after prolonged wet weather. I was determined to walk the length of the dam though and bless her, Megan followed doggedly behind.
Looking down the Eigiau Dam.
Llyn Eigiau in the background.
Foxgloves.
She puts up with a lot!
The channel scored by the water, which joins the river further down the valley.
We did managed to walk along the imposing structure, but it was pretty tough going for a 4 year old and the foliage was taller than her at some points! Our legs did get pretty wet and there was a bit of moaning! The next point of interest was the original breach, which led to the tragedy of 1925.
The breach.
The breach.
What we see today doesn’t reflect the full picture of what happened on that fateful night, but rather is a picture created by the ACL in order to shift the blame away from themselves.
The aftermath
The ACL and it’s managing director Henry “Harry” Jack swung into damage control by suggesting the disaster was caused by a catastrophic but wholly unforeseeable failure of the dam wall at Eigiau that was entirely the fault of the contractors who built it rather than the ACL itself.
Reports showed the dam wall was filled with both large boulders and junk such as sections of cut-up railway line. There were also large voids and sections that had not been built far enough into the glacial clay that formed the valley floor. Those reports were right. You can see the poor quality of the concrete for yourself today. You can also see with the naked eye that the phase-two dam wall to the east of the breach is narrower than the phase-one wall to the west. Where the two phases of the dam wall and the two phases of foundation construction met (when construction halted in 1908 the latter had extended further than the former) was obviously a potential weak spot.
Following an inquest, the blame was unceremoniously dumped on the deceased overseer of concrete mixing called Mr Wilson and his nameless underlings employed by the company Bott & Stennett, the original contractors who had gone bankrupt in December 1908.
Two days after the disaster, a local village policeman, PC Jones, walked across the top of the dam over the blow out and describe the hole as being 72 feet long and 15 feet high. Giving evidence at the inquest, PC Jones also noted that in previous years seepage from the dam had been so bad that the road up the valley was sometimes ankle-deep in water. In other words, it was common knowledge that the dam leaked. On top of this, the water management system which tied the reservoirs at Eigiau and Coedty together and drew in water from Dulyn and Melynllyn was a disaster waiting to happen. The system was designed to ensure that abundant water was always available for the hydroelectric turbines in Dolgarrog, not to deal with too much water. There were no contingencies to close the various sluice gates that controlled the flow of water into the reservoirs in case of an emergency. Finally, the spillways at Eigiau and Coedty were both far too small, and there was also the question of how the dam at Coedty had been built. If a concrete or stone facing had been applied to the outside of the dam to prevent overlapping washing away the supporting earth bank, disaster could have been avoided.
As seen today, the breach in the Eigiau dam reinforces the impression the ACL wished to give that it was the direct cause of the flood that swept down the valley. However, the gap now is the work of the ACL men who in the weeks following the disaster tidied up the breach, demolished the “arch” over which PC Jones walked, and covered the exposed ends of the dam foundation to conceal its depth. The idea was to give the impression that a large section of the Eigiau dam wall had suddenly collapsed.
The disaster had one benefit. The Dolgarrog flood and the failure of the Skelmorlie dam in Scotland, which had killed five earlier in the same year, provided the impetus for the 1930 Reservoirs (Safety Provisions) Act, which laid down such basic rules as the requirement that a qualified civil engineer must supervise the construction of any large dam and that any dam holding back more than 22.7 million litres of water should be subjected to a through inspection once every ten years by an expert in dam design. The disaster at Dolgarrog may have saved lives elsewhere.
After we had a look at the breach itself and took in the scene, imagining what must have happened on that night in 1925, we joined back onto the road. We crossed the “ford”, which was dry today and only exists because the water from the breach carved its way through the land, before joining the river further down, and made our way to the bigger gap in the dam through which the Afon Porth Llwyd passes.
Track towards the larger gap.
3. The large gap in the short leg of the L shaped dam was to be a revised spillway if the dam was ever put back into use. We turned right here and took a short walk through the gap (still on a track) to have a look at the now much smaller Llyn Eigiau.
Looking back at the bigger gap from the Llyn Eigiau side of the dam.
Llyn Eigiau. The dam is out of shot on the right.
Megan in Cwm Eigiau.
Llyn Eigiau
The name Eigiau is thought to refer to the shoals of fish which once lived here. Early maps refer to it as Llynyga. It is thought that a small number of Arctic char exist in the lake (as they do in neighbouring Llyn Cowlyd) after they were transferred here from Llyn Peris, and certainly it is one of the few lakes in Wales to have its own natural brown trout. The lake is surrounded by mountains including Pen Llithrig Y Wrach.
Today the lake covers an area of about 120 acres, and has a depth of about 32 foot. After the construction of the dam its area would have been twice this.
Water is fed into the lake by a tunnel from the stream below Llyn Dulyn, and another larger tunnel takes water from Llyn Eigiau to Llyn Cowlyd. The main feeder of Llyn Eigiau is Afon Eigiau, a small river which flows down the cwm. The outflow from the lake is called Afon Porth Llwyd, and this flows via Coedty reservoir before passing under Pont Newydd in Dolgarrog and into the Afon Conwy.
We headed back towards the dam, and unfortunately due to my lack of attention (we were singing a song, probably about unicorns) I slipped on the uneven track and fell over! I managed to pull poor Megan down with me and land on top of her. Luckily I landed on my front and other than being shaken about a bit, Anwen was fine and didn’t make a peep. Megan had a little cry, told me off, then got distracted. Thank goodness for the attention span of 4 year olds. Pretty embarrassing falling over on a bloody road though!
Anyway, once back through the gap we turned right over the little bridge which crossed Afon Porth Llwyd.
Looking back towards Cwm Eigiau from the bridge.
Looking down the valley towards Dolgarrog.
We followed the track up a short way towards the end of the dam, until we go to a left turn.
Looking back at the Eigiau dam.
Looking back at the dam.
4. At this point we turned left, heading down the valley in the direction of Dolgarrog.
Heading down the valley with Afon Porth Llwyd on our left.
Looking back at the dam, the breach, and the channel which joins with the river.
The track we follow at this point is all that remains of the Eigiau Tramway. There is no evidence of any rails or sleepers of any kind, but we do pass some bridges, cuttings and minor embankments which clearly set this route apart from an ordinary road.
Eigiau Tramway
The Eigiau Quarry Tramway was a 2 foot narrow gauge, mile-long, horse-powered tramway which operated from c.1863 to c.1888 and served the Cwm Eigiau quarry, near Llyn Eigiau. The tramway was an extension of the 4 mile Cedryn Quarry Tramway, and linked these two quarries to Dolgarrog.
The Eigiau Reservoir Tramway was an industrial railway, built to standard gauge from about 1907 to aid the construction of the dam at Eigiau Reservoir. It largely followed the course of the Cedryn Tramway, including the inclines down to Dolgarrog. After the reservoir was completed the tramway continued in use to aid in maintenance of the reservoir and its associated feed pipes.
The breach of the dam effectively spelt the end of the tramway, although a small extension was built in that year to aid the reconstruction of the Coedty Dam.
Evidence of the former tramway.
Bridge.
Bridge.
The walking here is pretty straightforward but a little monotonous. The views are stunning but it does feel like an awfully long section. If you look across the valley you can see where your car is parked in the distance, which probably makes the whole thing feel longer than it actually is. The weather was a bit changeable today too, varying from just cloudy to drizzle to ominously black! I’m always aware of the dangers of the weather up in the mountains, and although we were on a really straightforward path which would be easily followed home, the moments where the sky blackened made me quite uneasy.
Looking back the way we’ve come with the dam in the far distance.
Evidence of former buildings.
Evidence of former buildings.
We kept on though, with my plan b (the longer route being totally out of the question at this point) firmly in my sights. We did pass numerous remains of old buildings and sheepfolds on our way, but there wasn’t much left to explore.
5. It was at the remains of one of these buildings that the map showed me that the path I had planned to take, to cut across the valley, was located. I surveyed the scene for a moment. There were ruins, trees, thick undergrowth, but as far as I could see, no path. Still, my OS tracker said we were in the right place so off we set. Mistake. The path on the app followed the line of a fence so we made our way to the fence with poor Megan hanging on to Anwen’s rucksack. It was at this point that we had out second fall when I put my foot in a boggy section of ground and my legs went from under me. We reached the fence and followed it, with difficulty, to the river. It was at this point that I realised the “path“ we were on, and the path on the other side of the river didn’t actually meet at any point! To be fair... the map doesn’t show them meeting. I had assumed (silly me) that they would due to their proximity to each other.
My planned route, highlighted in yellow. If there is a way to join the two paths... I didn’t find it!
Path? What path?
It was with a thoroughly sinking heart, a fed up four year old, and very wet feet that I realised we would need to go back the same way we had come. We struggled back through to the road and trudged home. It’s been a few years since I carried Megan on a walk but I did today. We made an agreement that if I would carry her for a while, she would walk without whinging. Anwen thoroughly enjoyed having her big sister making faces at her over my shoulder... my back did not! The weather cleared up a little bit on the way back which was a relief and made things slightly cheerier. Once we arrived back at the dam, we knew it wasn’t too far to go then and that also perked us up.
Back on the ford looking at the breach.
Looking at the channel cut by the floodwater.
She managed a smile for me!
The road back to the car felt very long!
Tired... but not so tired that she couldn’t investigate a fat slug.
#sheep
We got back to the car absolutely exhausted and a bit muddy and bedraggled (not Anwen... she had a lovely time!) I made sure to buy the genod a chocolate bar on the way home as a treat. They really deserved it after today’s trek!
Today was definitely a learning curve for me. It doesn’t matter how much you study maps or satellite pictures, nothing can really prepare you for the conditions on the ground. It really is a case of being as prepared as you possibly can be and not being afraid to turn back if you have to, rather than taking risks and getting yourself into a dangerous position.
Despite not being our most successful walk, I will definitely be back to Cwm Eigiau with it’s diminished lake, looming broken dam, and incredible views. I’d like to walk from the Eigiau dam down to the Coedty dam (only a short way from where we turned back today) and maybe on then to Dolgarrog so that we could follow the full route of the disaster. I don’t think I’ll suggest that to Megan though. For now she’s happy wandering down the road to the local playground!
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