Wemyss Lead & Zinc Mine

It is located at the head of the Cwmnewydion valley, a tributary of the River Magwr, which joins the River Ystwyth at Abermagwr.

The mine worked the Frongoch mineral lode alongside Frongoch and Graig Goch mines.

Wemyss became an integral part of the larger Frongoch Mine and cannot be considered in isolation from its more illustrious neighbour.

In the 1840s both mines came under the same ownership and the Wemyss drainage adit was extended to also serve the Frongoch workings, becoming the Frongoch Adit we know today.

The mines continued to be operated together with varying success throughout the latter half of the 19th century until they were acquired by the Belgian company ‘Société Anonyme Miniére’ in 1898.

The Belgians invested heavily in modernising and electrifying the mining operations, which included constructing a state-of-the-art hydro-electric power station at Pont Ceunant and a large ore dressing mill at Wemyss.

However, the venture was short-lived and by 1904 the company were in liquidation and all of the mine’s machinery and effects were sold at auction.

Today, the Wemyss site is dominated by the ruins of the dressing mill and its large spoil tips which are bordered to the south by the Cwmnewydion Stream and to the west by the smaller Mill Race Stream.

There are also the remains of the wheel pit for a 56-foot waterwheel, which was fed by a leat from Frongoch.

Wemyss is a significant source of metal pollution and is causing a chemical and ecological impact on downstream watercourses.

• Mine water treatment
• Surface water management e.g. Mine site drainage
• Sediment control
• Mine waste reprofiling
• Mine waste capping
• Watercourse management e.g. separation

Status:

Ongoing / In Construction

We are currently in the process of installing temporary scour protection at Wemyss.

Temporary scour protection at Wemyss will involve installing rock rolls on the spoil tips to reduce contaminated material from entering the watercourse.

Temporary scour protection will be installed at this location

Status:

Detailed Design

Over the past few years we have been gathering information to better understand the pollution risk from Wemyss Mine, Graig Goch Mine and Frongoch Adit to identify a list of potential mitigation solutions. Graig Goch Mine and Frongoch Adit are being progressed together under one project called Cwmnewydion, while Wemyss Mine is being progressed as a separate project within the overall Programme. The two project teams are working closely to seek efficiencies and maximise benefits. We have commissioned a Scoping Report that includes both Graig Goch Mine and Frongoch Adit and conducted archaeological and ecological assessments, in order to identify the problems that are causing pollution of the watercourse/ water quality issue and which need addressing.

At Wemyss Mine, a Feasibility Study identified that the primary pollution sources are the metal-rich spoil heaps that characterise the site. Erosion, mobilisation and leaching of metals is occurring where the watercourses and rainfall interact with this mine waste. We progressed a number of surface water management engineering interventions into the Outline Design stage. In early 2024, we then advanced this project to Detailed Design stage.

Detailed design means that we are now finalising our design ready for construction. We will continue to liaise with local landowners as we progress through this stage. In addition, we identified options to install temporary scour protection.

We are now progressing through our detailed design phase. Our teams will continue to monitor Wemyss during this period.

We will be finishing the installation temporary scour protection measures in spring 2025.

Below gives a timescale of our work for Wemyss. Please note that this timeframe is indicative and could change.

Spring 2025:

• Construction of temporary scour protection
• Progress detailed design
• Enter tender stage

Summer 2025: 

• Finalise detailed design
• Engagement with landowners and wider stakeholders
• Progress through tendering process

2026 onwards

• Anticipated construction phase

2023

Should you wish to request a specific information, please contact the team via cwmnewydion@metalmineswales.co.uk.

Website links

• Cwmnewydion metal mine project - Natural Resources Wales Citizen Space - Citizen Space

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