Tirpentwys Colliery

Overview

The largest colliery in the Cwmffrwdoer valley, a mile and a half from Pontypool, originally known as Cwmffrwdoer Colliery or Gelli. It opened in 1877 and worked until 1969, and included a small level known as Black Vein. A steam-hauled 2 ft 8 in gauge tramway ran from the colliery to a landsale yard from 1901 to 1919. After it stopped producing coal it was kept on as a pumping station and to ventilate the underground coal-clearance route from Blaenserchan to Hafodyrynys.

History

Cwmffrwdoer Colliery — better known afterwards as Tirpentwys, and also recorded as Gelli — opened in 1877, and the incline that served the valley then terminated at Gellideg Sidings on the new Great Western branch line. It became the largest colliery in Cwmffrwdoer, working until 1969 and including a small level known as Black Vein. A steam-hauled tramway of 2 ft 8 in gauge ran from the colliery to a landsale yard from 1901 to 1919, and appears to have reached as far as Pen Tranch. The valley around it was crowded with smaller workings: Plas-y-coed Colliery a little way off from 1885 to 1923, and Ty-gwyn Llantwit overlooking Tirpentwys from the western side of the valley, working by 1881 and closed about 1904, with much of the ground below it tipped over. The colliery closed in 1969, but it was not finished with. It was retained as a pumping station and to provide ventilation for the coal-clearance system running underground from Blaenserchan to Hafodyrynys. The cages, ropes and winding equipment were taken out and submersible automatic pumps installed in the No. 1 downcast shaft; No. 2 pit was filled, and the pumping went on at Tirpentwys for some years before No. 1 was filled in its turn.

Geology

The eastern side of the South Wales coalfield, in one of the narrow valleys running down towards Pontypool. The colliery included a level known as Black Vein — the name of one of the best-known and most gassy seams of the Monmouthshire coalfield — and was deepened during its life to reach the steam-coal measures below the seams it started on.

Workings

Two shafts, a downcast No. 1 and an upcast No. 2, together with a small level known as Black Vein. A steam-hauled 2 ft 8 in gauge tramway ran to a landsale yard between 1901 and 1919. After 1969 the winding gear was stripped out, submersible automatic pumps were installed in the No. 1 downcast, and No. 2 was filled; the colliery went on serving the Blaenserchan to Hafodyrynys clearance route underground as a pumping and ventilation shaft until No. 1 was filled too.

Closure

Tirpentwys stopped producing coal in 1969 but was retained afterwards as a pumping station and as ventilation for the coal-clearance system from Blaenserchan to Hafodyrynys. The pumping continued for some years before the last shaft was filled.

What remains

After closure the whole area was cleared, used as a rubbish dump and then landscaped; part of it is now the Tirpentwys nature reserve. The remains of a large building stand beside a small quarry at SO 2465 0000, and the line of the tramway to the landsale yard can still be traced.

The remains of a large building beside a small quarry, and the course of the 2 ft 8 in gauge tramway to the landsale yard.

Related mines

• Blaenserchan Colliery — After Tirpentwys stopped producing coal in 1969 it was retained as a pumping station and to provide ventilation for the coal-clearance system that carried Blaenserchan’s coal underground to Hafodyrynys — the closed pit kept open to keep its neighbour working.
• Hafodyrynys Colliery — Tirpentwys was kept on after its own closure to pump and ventilate the underground route by which coal from Blaenserchan was cleared to Hafodyrynys.

Nearby mines

• Hafodyrynys Colliery — 1.8 km SW, Caerphilly
• Llanerch Colliery — 3.6 km NE
• Navigation Colliery — 3.7 km W, Caerphilly
• Blaenserchan Colliery — 4.1 km NE
• Six Bells Colliery — 4.3 km NW, Blaenau Gwent

Straight-line distance, within 15 km. Show on the map.

Recorded claims

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

• Tirpentwys Colliery, originally known as Cwmffrwdoer Colliery or Gelli, was the largest in Cwmffrwdoer, working from 1877 to 1969 and including a small level known as Black Vein. (disputed) ¹
• A steam-hauled tramway of 2 ft 8 in gauge ran from the colliery to a landsale yard from 1901 to 1919 and appears to have gone as far as Pen Tranch. ¹
• After closure the whole area was cleared, used as a rubbish dump and landscaped; the remains of a large building stand beside a small quarry at SO 2465 0000. ¹
• The BGS catalogue of abandoned mine plans holds records under both "Tirpentwys" and "Tirpentwys Group (Opencast)". ²

Photographs & further reading

Sources

1. (observational) Tirpentwys: the Cwmffrwdoer valley, its industrial archaeology and history — Industrial Gwent
2. (primary) BGS mine plans catalogue: TIRPENTWYS — British Geological Survey

Record created: 7 September 2026 · Last researched: 7 September 2026