Trelewis Drift Mine

Overview

A drift driven into the hillside above Taff Merthyr in 1954 because the National Coal Board could not afford another Abernant, and which then out-produced almost everything in the South Wales coalfield. It held the coalfield productivity record, was closed anyway in 1989, and its buildings are now a climbing centre.

History

By the early 1950s the National Coal Board's great South Wales reconstruction schemes were disappointing it: Abernant and Cynheidre had not produced the coal expected of them. Drift mines cost a fraction of a deep-pit reconstruction, and the Board drove four of them in Glamorgan — Trelewis in 1954, Blaenant and Coedcae in 1963 and Treforgan in 1969 — into ground whose working life it could not guarantee. Trelewis was driven to take the Brithdir seam from near the surface at Taff Merthyr, and to absorb the men coming off the nearby Bedlinog drift as its reserves ran out. The Merthyr Express reported in 1952 that the new drift was expected to last thirty years and to work about 1,100 acres of the Brithdir at around 300 yards, a seam five to six feet thick with working reserves put at about 4.75 million tons. Far from being the short-term expedient the Board had in mind, the drift became one of the outstanding performers of the coalfield. By 1961 it was part of the most productive group in South Wales, Number 4 Area's group alongside Merthyr Vale, Deep Navigation and Taff Merthyr. In February 1971 it set a coalfield productivity record of 188 hundredweight per man shift. In 1975, when the South Wales coalfield as a whole lagged the rest of the country on mechanisation, Trelewis was almost wholly mechanised and managed 80.9 hundredweight per man shift. The Board put six million pounds into it in 1978, opening new levels and building the drift its own baths and offices; until then the men had walked over to Taff Merthyr's. The men worked wet. Enormous quantities of water were pumped out of the drift, and their bonus payments were noticeably better than those of the Taff Merthyr miners next door, in part because a drift with no shafts brings its coal out cheaply. The colliery was reported to be losing money in 1983; after the year-long strike of 1984 and 1985 the men brought it back into profit, and in 1988 some 280 men produced 470,000 tonnes of power-station coal.

Geology

The drift worked the Brithdir seam of the South Wales Coal Measures, five to six feet thick and lying close enough to the surface above Taff Merthyr to be reached by a drift rather than a shaft.

Workings

The main drift was driven about 340 yards at a gradient of one in four and stood fourteen feet high — big enough for the mechanised equipment the Board intended to put into it, and for the first continuous miner in South Wales, a sixteen-tonne machine installed within a month of production starting in 1955. Hydraulic mining was tried here in 1958, the coal cut from the seam by high-velocity water jets from a hose called a monitor. There were no winding shafts: coal came out on the drift, which is part of why the mine was cheap to run and its men well paid.

Closure

British Coal closed the drift in 1989, four years after the strike and with 296 men still employed; David Fox was the manager. The surface buildings were not demolished.

What remains

The buildings are in use. The Taff Bargoed Development Trust turned the site into an indoor climbing centre in 1997, part of the Millennium park laid out along the valley floor where Taff Merthyr and the drift had stood; the walls run to eighteen metres and there is an artificial cave system with a waterfall in it. It has been through financial trouble more than once, and now operates as an activity centre with a residential block. A commemorative stone stands at the old mine entrance.

The colliery buildings themselves, converted rather than cleared, and the commemorative stone at the entrance.

Redevelopment

An indoor climbing and caving centre from 1997, extended in 2019 with a hundred-bed residential activity centre.

Related mines

• Deep Navigation Colliery — Both were in the National Coal Board's Number 4 Area group, which by 1961 was the most productive in South Wales and turned out more than a million tons a year between Trelewis Drift, Deep Navigation, Taff Merthyr and Merthyr Vale.
• Taff Merthyr Colliery — The drift was driven in 1954 to take the Brithdir seam from near the surface at Taff Merthyr, shared its baths, canteen and washery for thirty years, and sent its coal through the Taff Merthyr washery to the end. The Royal Commission's record links the two sites directly.

Nearby mines

• Bedlinog Colliery — 2.1 km N
• Merthyr Vale Colliery — 2.9 km W, Rhondda Cynon Taf
• Taff Merthyr Colliery — 2.9 km SW
• Darran Colliery — 3.9 km E, Caerphilly
• Ogilvie Colliery — 3.9 km NE, Caerphilly

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.

• The National Coal Board drove four drift mines in Glamorgan — Trelewis in 1954, Blaenant and Coedcae in 1963, Treforgan in 1969 — because its big reconstruction schemes at Abernant and Cynheidre were producing less than hoped and a drift needed substantially less capital in ground whose working life could not be guaranteed. All four outlasted that reasoning. ¹
• Announcing the scheme in 1952, D. M. Rees of the Board's South Western Division said the new drift had an estimated life of thirty years and would work the Brithdir seam over about 1,100 acres at an average depth of some 300 yards, the seam five to six feet thick with working reserves of about 4.75 million tons. Saleable output was put at 455 tons a day, around 100,000 tons a year. ¹
• In February 1971 Trelewis Drift set a South Wales coalfield record of 188 hundredweight per man shift. In 1975, with the coalfield behind the rest of the country on mechanisation, the drift was almost fully mechanised and produced 80.9 hundredweight per man shift; by 1981 a face was advancing over four and a quarter metres a day at 17.67 tonnes per man shift, the highest in the coalfield, with 382 men employed. ¹
• In June 1958 the National Coal Board announced that its first experimental installation of hydraulic mining would be at Trelewis: the coal cut out of the seam by high-velocity water jets from a hose called a monitor, the same jet then used to clear the floor of the working place. ¹
• The Royal Commission's record describes the drift as disused with its buildings converted to a leisure centre, and links it to Taff Merthyr Colliery next door. ²
• Without warning the roof fell in a working place at the drift in August 1957, killing Thomas Walters, aged 41, of Company Row, Penfarnddu, Merthyr Tydfil, and injuring three others. A deputy told the Nelson inquest that Walters had been one of a gang of five erecting bars to support the roof, and that a hidden slant was found afterwards, a bell-shaped stone having fallen out of the cavity. The jury returned accidental death. ¹
• A highly productive drift mine opened at a cost of £408,000 by the National Coal Board in 1954 to work the Brithdir seam from the surface of Taff Merthyr Colliery. The main drift was driven 342 yards at a gradient of one in four, was fourteen feet high, and was expected to expose 4.75 million tons of reserves. ³
• The Brithdir was worked at a section of 1.78 metres, with coalface length varying between 135 and 200 metres. Coal cutting was by ranging drum shearer and the coalface supports were the self-advancing type. ³
• In January 1970 the drift broke its own South Wales output record with 188.4 hundredweight per manshift, twenty-six hundredweight above the old figure. Each man on the coalface was producing 57 tonnes a shift, for a weekly total of 8,779 tonnes — the highest output, with the lowest manpower, in the East Wales Area. Each man received eight pints of beer from the manager. ³
• In July 1979 the A12 face was the best performing retreat coalface in the South Wales coalfield, in a seam over 150 cm thick, producing 1,324 tonnes a day. During 1981 the B12 face advanced 4.26 metres a day at 17.67 tonnes per manshift, the highest in the coalfield. The saleable yield from the Brithdir seam, though, was only 50 to 70 per cent. ³
• In 1983 the National Coal Board reported the colliery as losing £14.30 on every tonne of coal it produced. After the strike of 1984 and 1985 it recovered to 87 per cent of expected output within a month. ³
• V. D. Savage managed the drift in 1954, when it employed 13 men at surface and 164 underground. D. M. J. Evans followed from 1969 to 1976, W. G. Cecil from 1977 to 1979, A. J. McGaw in 1980, D. Roberts in 1981 and D. Fox at the closure in 1989. ³

Photographs & further reading

Sources

1. (secondary) Trelewis Drift — Treharris District
2. (primary) Trelewis drift mine (NPRN 86979) — Royal Commission on the Ancient and Historical Monuments of Wales
3. (secondary) Trelewis Drift — Welsh Coal Mines

Record created: 9 September 2026 · Last researched: 11 September 2026