Nant y Mwyn Lead Mine

Overview

The Nant y Mwyn mine is located close to the village of Rhandirmwyn in Carmarthenshire; approximately 10 km to the north of Llandovery.

There is evidence of ancient mining (pre-Roman) at the site however most of the workings date from the 16th through to the 20th centuries.

Mining activity at Nant y Mwyn mine during the early 20th century was intermittent and the site was abandoned during the early 1930s.

The workings can be divided into two main areas; the Upper Mine and the Lower Mine workings.

The Upper Mine workings are the more extensive and are found along the valley of the Nant y Bai to the north of Rhandirmwyn. They constitute the collapsed Upper Boat Level portal (or ‘mine entrance’), settlement ponds, dressing floors, engine house & chimney and substantial spoil tips.

The Lower Mine workings are situated adjacent to the southwest of Rhandirmwyn in the valley of the Nant y Mwyn watercourse, although workings extend up the length of the valley to the northeast. These workings comprise spoil deposits and a former mine process area, Pannau Adit portal and Deep Boat Level portal. The Deep Boat Level is the main discharge point for the Nant y Mwyn Mine and is located in the grounds of a residential property. The portal has collapsed causing the discharge water to issue from a shaft approximately 50m back from the original portal before entering the Nant y Mwyn via Church Terrace tributary.

Both Nant y Mwyn and Nant y Bai streams are heavily contaminated and contribute approximately 13 tonnes of zinc, 2 tonnes of lead and 40 kg of cadmium to the environment each year.

They are a significant source of metals to the Afon Tywi, causing the river to fail standards for zinc and cadmium, with zinc remaining elevated for approximately 25km downstream of the mine.