Cwm Rheidol Mine

Overview

The Cwm Rheidol mining complex, in the hills above Ystumtuen east of Aberystwyth, was a group of four interconnected lead, zinc and silver mines — Ystumtuen, Penrhiw, Bwlchgwyn and Llwynteifi — worked intermittently from the late 17th century into the early 20th, whose acidic mine drainage remains an active water-quality problem in the Rheidol valley today.

History

The earliest definite record of mining at Ystumtuen dates from 1698; the mine was already active by 1705 and worked until 1727, before reopening in 1746 and being noted again in 1806, 1824 and 1839, under a succession of lessees. From 1844 attention shifted to a new adit mouth that became the Cwm Rheidol mine proper; by the late 19th century the four mines — Ystumtuen, Penrhiw, Bwlchgwyn and Llwynteifi — were all connected underground, with drainage carried out via the No. 6 and No. 9 adits into the River Rheidol. Ystumtuen itself appears to have closed around 1882, though later working centred on Cwm Rheidol continued to around 1917. A processing mill removed waste rock from the ore, which was then carried by aerial ropeway across the valley to the Vale of Rheidol Railway and on to Aberystwyth.

Geology

The mines exploit lead-zinc-silver veins typical of the Central Wales Orefield.

Workings

Four interconnected mines drained underground via the No. 6 and No. 9 adits into the River Rheidol; ore was processed at a mill and carried across the valley by aerial ropeway to the Vale of Rheidol Railway.

What remains

The old workings continue to drain from the adits today, and both discharges are highly acidic with significantly elevated concentrations of zinc, lead and cadmium; this contamination causes an 18km stretch of the River Rheidol downstream to fail Water Framework Directive standards for zinc and cadmium. Remediation work by Natural Resources Wales has included diverting surface streams away from mine shafts (2007), reducing drainage through the No. 9 adit to prevent a catastrophic release of stored mine water (2008), and installing capture piping to control erosion and metal mobilisation (2009), with ongoing work addressing adit collapses to keep drainage flowing in a controlled way.

Abandoned workings can be dangerous — unstable ground, uncapped shafts, flooding and bad air are common even where a site looks safe from the surface. This entry describes history and general location only; it is not an access guide.

Recorded claims

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

• The earliest definite record of mining at Ystumtuen dates from 1698; the site was worked until 1727, reopened in 1746, and recorded again in 1806, 1824 and 1839. ¹
• By the late 19th century, Ystumtuen, Penrhiw, Bwlchgwyn and Llwynteifi were all connected underground, draining via the No. 6 and No. 9 adits into the River Rheidol. ²
• Drainage from the old Cwm Rheidol workings remains highly acidic, with elevated concentrations of zinc, lead and cadmium causing an 18km stretch of the River Rheidol downstream to fail Water Framework Directive standards for zinc and cadmium. ²
• Remediation work since 2007 has included diverting surface streams away from mine shafts, reducing drainage through the No. 9 adit to prevent a catastrophic release of stored mine water, and installing capture piping to control erosion and metal mobilisation. ²

Photographs & further reading

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

Images

Sources

1. (secondary) Ystumtuen — Wikipedia
2. (primary) Cwm Rheidol Lead & Zinc Mine — case study — Natural Resources Wales

Record created: 19 August 2026 · Last researched: 20 August 2026