Minera Mine Complex
Overview
Background
Minera mine complex is recognised as one of the most important in North East Wales, during the peak production years between 1860 and 1880 it was one of the largest lead and zinc ore producer in the British Isles. In total, the mine produced over 135,000 tons of lead concentrates and 180,000 tons of zinc concentrates.
The mining infrastructure was extensive, featuring a network of shafts, adits, and tunnels that also utilised natural limestone caverns. Most of this network is now submerged due to flooding after the mine’s closure. During the mining operation the water inflow through natural limestone cavities was a constant challenge, with the construction of a drainage tunnel known as the Deep Day Level completed in the 1850’s where the water entered the Afon Clywedog near Nant Mill. In 1965 part of the Deep Day Level collapsed, this resulted in the majority of the adit water flowing into the Stryt y Scweiar Dingle.
Minera forms part of the Wales Metal Mines Programme (WMMP), delivered in partnership between Natural Resources Wales (NRW) and the Mining Remediation Authority (MRA). The programme focuses on reducing pollution from abandoned metal mines across Wales.
Stryt Y Scweiar Project
Mine water discharges into the Stryt Y Scweiar channel before flowing into the Afon Clywedog.
Through our investigation, we have established that the existing culvert on this channel is undersized, which restricts water flow and contributes to localised issues. The project will install a new culvert to better manage these flows and facilitate flow measurements of the mine water.
Measuring the flow will enable us to assess the impact of the mine water on the Afon Clywedog, this will also provide vital information if any remediation/intervention measures are planned in the future.
Culvert at Stryt Y Scweiar
Project Progress
- Site investigations and surveys, including topographical survey work, have been completed.
- Environmental considerations have been assessed, including ecology, hydrology and heritage.
- An Environmental Action Plan (EAP) has been developed
- Planning requirements have been reviewed, with no full planning permission anticipated, however, consent for works in an ordinary watercourse is expected.
Benefits of the Works
- Improved water flow management – the new culvert will better accommodate mine water and surface flows, reducing pressure on the current system
- Increased resilience – upgraded infrastructure will help prevent blockages and localised flooding issues
- Problem definition – flow monitoring will enable collection of vital data to assess the mine water contamination
- Environmental protection – supports the wider WMMP objective of improving water quality across historic mining areas
- Safer and more reliable infrastructure – replacing an undersized culvert reduces risk of failure and ongoing maintenance issues
Next Steps
- Finalise design and construction approach for the culvert replacement
- Secure required consents, including Ordinary Watercourse Consent
- Confirm contractor responsibilities, including site management, environmental controls and utility coordination
- Issue the final Environmental Action Plan once construction methods are agreed
- Progress to site mobilisation and construction
Current Timeline
- 2024 – Topographical survey completed
- Early 2026 – Site information and tender documentation prepared
- 2026 (planned) – Culvert replacement works expected to take place, subject to final consents and contractor mobilisation
Upcoming Culvert Works – Stryt y Scweiar
We will shortly be carrying out essential culvert improvement works at Stryt y Scweiar as part of the Wales Metal Mines Programme.
Why these works are needed
The Minera mine system has been identified as a priority area due to historic mine water affecting local streams and rivers. These works will help us better understand and manage water flows in the area, supporting future efforts to reduce pollution and improve the environment.
To support this, we need to replace an existing surface water culvert and install a flow monitoring structure. This will:
- Enable more accurate monitoring of water flows
- Support the development of future pollution reduction solutions
- Help protect the channel from ongoing damage caused by overflows and erosion
What the works involve
The works will be carried out by Evans Construction and will include replacing the existing culvert and installing equipment to measure water flow.
- Start date: 24/08/2026 (to be confirmed)
- Duration: Approximately three weeks
- Working hours: 8:00am – 5:00pm, Monday to Friday
Road access
To carry out the works safely, there will be a temporary road closure on the lane west of the ford at Stryt y Scweiar. A Temporary Traffic Regulation Order (TTRO) will be put in place for this.
We will work closely with the contractor to minimise disruption and appreciate your patience while this work takes place.
What to expect
During the works, you may notice:
- Construction activity, including plant and machinery
- Some temporary increases in noise
- Additional vehicle movements in the area
All works will be undertaken with care and consideration for the local community and environment.
(last updated 15/07/2026)
Keeping in touch and how to get involved
If you’d like to share your views, be added to an email mailing list, or have any questions please get in touch on the details below:
enquiries@metalmineswales.co.uk
Areas
- All Areas
Audiences
- Metal mines
Interests
- Metal mines
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