Aberfan disaster – lessons learned

Accepting there were failures and making sure it never happens again

The Aberfan disaster was the collapse of a National Coal Board (NCB) spoil tip near the village of Aberfan on the morning of 21 October 1966. A spoil tip is a pile of waste rock and soil removed during coal mining.

Seeing the words 'Aberfan disaster' in this bicentenary collection of civil engineering projects may seem inappropriate. But it is the lessons learned from the disaster and the human errors in the months and years that preceded the tip failure that are explained here.

A fundamental principle for civil engineering to progress is the need to ensure that lessons are learned for future projects.

The first shaft for the Merthyr Vale Colliery was started in 1869 and the first coal produced in 1875. By 1916 the colliery had run out of space to tip the waste on the valley floor and began tipping on the mountainside above the village of Aberfan.

Tipping continued until 1966 by which time 7 tips had been constructed containing 2.7m cubic yards of colliery spoil.

Throughout this time there was a total absence of UK laws and regulations governing mine and quarry waste tips and spoil heaps and the NCB had no tipping policy that would have enforced the need for appropriate design and management of tips.

The steep hillside above Aberfan was riddled with springs and no effort was made to enclose the streams that would eventually be buried beneath the tips.

A large failure of Tip 4 in 1944 was not even a reportable incident because nobody from the colliery was injured – so many who should have heard about this or other similar events never did. The professionals in charge were inappropriately qualified and lacked appropriate experience and direction.

Concerns were raised that this represented a disaster waiting to happen but clear warnings went unheeded and no action was taken to address the situation. Until it was too late.

Tip 7 covered material which had previously slipped in 1944 – the very same watercourse that had caused earlier failures. Its catastrophic failure on 21 October 1966 was the result of a build-up of water in the tip.

When a small slip occurred the disturbance caused the saturated, fine material of the tip to liquefy and flow down the mountain.

140,000 cubic yards of black slurry avalanched down the mountainside wiping out everything in its path and continued down to the village. It destroyed a farmhouse, cottages, 18 houses, Pant Glas Junior and part of the neighbouring County Secondary School – before finally coming to rest.

At 9.20am the hooter at the colliery, which had never suffered a major disaster, broke its long silence. In total 144 lives were lost, 116 of them children. The loss comprised half the youth of Aberfan.