Blaenclydach Colliery dam burst, 1910

On the afternoon of Friday 11 March 1910 water dammed in the abandoned Blaenclydach No. 2 level on the mountainside above Clydach Vale burst out as men drove a borehole through the barrier. Some 800,000 gallons of water and slurry swept down onto the school in Oak Street and the houses and shops around it, killing a mother and five children.

Cause

A dam across the mouth of the abandoned Blaenclydach No. 2 coal level held back mine water; when the men working at the level drove a borehole through the barrier the water trickled, increased, and about half an hour later burst out with tremendous force.

What happened

The old Blaenclydach No. 2 coal level, partly on Ffynondwyn Farm on the mountainside above Clydach Vale, had been dammed across its mouth, holding back mine water. Contractors' men were at work there on Friday 11 March 1910. John Davies said that when they drove the borehole through the barrier the water trickled out quietly, then increased, and in about half an hour there was 'a tremendous pounce' from inside; he and John Lloyd heard a big report and ran.

An estimated 800,000 gallons of water and slurry came down the hillside onto the school at Oak Street and the dwellings and shops around it. The headmaster, R. R. Williams, and the schoolmistresses kept their heads and saved many children. Mrs Elizabeth Ann Williams was found in her wrecked house in Adam Street and her baby later; George Tranter, waist-deep in the schoolyard, pulled out Enid Howells, who died on the way home; Moses Blake dived into twelve feet of water to save Gwendoline James and recovered two of the dead; and Arthur Jones reached the Brindles' bedroom by ladder, but lost his grip on the baby Haydn when the water carried them both away.

The six were buried at Trealaw cemetery on Wednesday 16 March, in what the Cambrian called the largest funeral ever seen in the Rhondda, with thousands lining the route. A dispute over the colliers' attendance at the funeral kept the local colliery idle until the Saturday.

Rescue & recovery

Teachers led children to safety; colliers and neighbours waded and dived into the flood to pull out survivors and recover the dead.

Investigation & inquiry

The coroner, R. J. Rhys, adjourned the inquest several times while the level was cleared and inspected and the ownership of the land, held by several parties including Miss Clara Thomas as tenant for life, was established; counsel appeared for the estate owners, the Rhondda District Council and the contractors, Messrs Thomas and Pugh. At the final hearing in May the jury returned a verdict of accidental death, agreeing that reasonable precautions had been taken on the evidence.

Legal & regulatory aftermath

Miss Clara Thomas paid the funeral expenses and agreed in May that damages to property would be paid from her estate.

Memorials & commemoration

The six were buried at Trealaw cemetery on 16 March 1910.

Recorded claims

Individual factual claims, each attached to the source(s) that support it below. Where sources disagree, both are kept.

• On 11 March 1910 a burst of water from the abandoned Blaenclydach No. 2 level killed six people at Clydach Vale, a woman and five children. ^1,2
• The water burst out when men drove a borehole through the barrier dammed across the mouth of the old level. ^1,3
• The coroner R. J. Rhys adjourned the inquiry several times while engineers investigated the old level and the ownership of the land was established. ^1,3,4
• The jury returned a verdict of accidental death, agreeing that reasonable precautions had been taken. ¹
• The six victims were buried at Trealaw cemetery amid great crowds. ²

Related terminology

Mining terms this disaster is structurally linked to, with the nature of the relationship.

• Coal (contextual relationship)
  Named twice in this record, first in the cause: “A dam across the mouth of the abandoned Blaenclydach No. 2 coal level held back mine water; when the men working at the level drove…”
• Colliery (contextual relationship)
  Named in this record’s narrative: “…dispute over the colliers' attendance at the funeral kept the local colliery idle until the Saturday.”
• Level (contextual relationship)
  Named 5 times in this record, first in the summary: “…11 March 1910 water dammed in the abandoned Blaenclydach No. 2 level on the mountainside above Clydach Vale burst out as men drove a…”

Photographs & further reading

This page doesn't try to reproduce everything — these are the best original sources found for this disaster.

Sources

1. (secondary) Welsh Coal Mines fatalities, 1910 — Welsh Coal Mines
2. (primary) 'Clydach Vale disaster: the funeral', The Cambrian, 19 March 1910 — Welsh Newspapers Online (National Library of Wales)
3. (primary) 'Clydach Vale disaster: inquest opened', The Cardiff Times, 26 March 1910 — Welsh Newspapers Online (National Library of Wales)
4. (primary) 'Clydach Vale disaster' (adjourned inquiry), Evening Express, 26 April 1910 — Welsh Newspapers Online (National Library of Wales)

Record created: 11 October 2026 · Last researched: 11 October 2026