The former Barneycraig lead mine at Carrshield is located within the North Pennines Area of Outstanding Natural Beauty, which itself is a UNESCO Global Geopark.
The mine operated primarily between c.1760-1920, and the mine tailings were deposited along the east bank of the River West Allen during that time. As a result, the river was the joint second worst in the Northumbria River Basin Management Plan in respect of mine water pollution, contributing around 20% of the total quantities of lead, zinc and cadmium found in the Tyne Estuary, over 40km downstream of the site.
The site was prioritised for remedial action as part of Defra’s Water and Abandoned Metal Mines programme, in partnership with the Coal Authority and the Environment Agency.
As part of the action plan for the site, the tailings storage facility required a permanent capping solution to prevent rainwater infiltration into the tailings, thus achieving the two key objectives for this part of the works, which were;
- To afford long term stability to the tailings dam, which had already begun to collapse into the River West Allen in several places;
- To mitigate the creation, and subsequent ingress, of an estimated 3,500kg of leached lead, zinc and cadmium into the river each year.
The original capping solution for this site included a separate flexible membrane liner (FML) and a geocomposite drainage layer (GDL). ABG simplified this by proposing Pozidrain 4SKL, which provides both functions in a rapidly installed single layer without compromising the integrity of the containment. ABG Pozidrain geocomposite requires no specialist contractors or equipment to install.
By using Pozidrain 4SKL geosomposite drainage capping solution, the contractor saved significant material costs compared to purchasing separate FML and GDL layers, as well as reducing the programme time for the installation works, whilst still fulfilling the key objectives of the project.
The ABG Service
ABG provided design assistance, including slope stability and flow capacity calculations.
Contact ABG today to discuss your capping, drainage and slope reinforcement project specific requirements and discover how ABG’s experience and innovative products can help on your project.