Dolgarrog Dam Disaster - Conwy, North Wales, UK - Human Error on Waymarking.com

'Llyn Eigiau is on the edge of the Carneddau mountains in Snowdonia. The name Eigiau is thought to refer to the shoals of fish which once lived here. It is one of the few lakes in Wales to have its own natural brown trout. In 1911 a dam mile long and 35 foot high was built across part of its eastern side to supply water for the power station at Dolgarrog. The original contractor pulled out of the construction, alleging corner cutting, and indeed on 2nd November 1925, following 26 inches of rain in just five days, the dam broke.'

Wikipedia has some more details:
'The disaster was started by the failure of the Eigiau Dam, a gravity dam owned by the Aluminium Corporation. The water released from the reservoir flooded downstream, and overtopped the Coedty Dam, an embankment dam. This dam also subsequently failed, releasing the huge volume of water that flooded Dolgarrog.

The construction of Eigiau dam had been facilitated by the construction of the Eigiau Tramway, which largely followed the route of the Cedryn Quarry Tramway from Dolgarrog.'

Llyn Eigiau, the higher reservoir above Dolgarrog to the south west of the village, gave way when its dam burst at 8.45pm on Monday 2nd November 1925. The hundreds of gallons of water which gushed out of Llyn Eigiau rushed down the mountainside into Llyn Coedty below. This reservoir was already full and the force of this extra water caused Llyn Coedty's dam to burst too.

Now the water had a free path to thunder down the mountainside unrestricted. It hit Dolgarrog village with a fifty foot high flood taking Machno Terrace first followed by the church, church house, sweet shop, butcher's shop and water mains. The force of the water caused the furnaces at the aluminium works to explode and Reverend Williams Evans was hailed a hero for bringing rescue workers to them.

The only surviving building from the area hit by the flood is the old Porth Lwyd hotel. Sixteen people died which was very lucky as most of the villagers were attending the local theatre watching a film elsewhere in the village.

The disaster was the advent of the 1930 Reservoirs Act brought about by the government to prevent such an event happening again.

There is a wide road with parking by the side of the memorial. A slate plaque is fixed to a boulder which was one of many which crashed down the mountainside with the flood water. Next to this is an information board in Welsh and English and the Memorial Walk starts here leading you through the area.