Cutting edge science at Force Crag Mine
History of the mine
Force Crag Mine was worked for zinc, lead and barytes from 1835 until 1991 and was famously the last working mine in the Lake District. The mine is a major source of metal pollution in Coledale Beck, a tributary of Newlands Beck, and the River Derwent and Bassenthwaite Lake Special Area of Conservation. This results in high levels of metals, notably zinc, cadmium, lead and copper, entering the stream causing pollution and a failure to meet water quality standards.
The site is now owned by the National Trust and we run guided tours on six open days each year. It is also a Scheduled Ancient Monument, so obviously we want to stop the pollution.
To treat the metal-rich mine water we are constructing a pilot passive-mine-water remediation scheme which will reduce the quantity of metals entering the Coledale Beck to improve the aquatic environment and the quality of the downstream watercourses.
The pilot scheme is the first of its kind, at this scale, in England and will provide a better understanding of the passive method of removing metal contaminants from water. Passive treatment methods are ones which use only natural processes. The outcomes and results from this pilot scheme will significantly aid the future development of metal mine water treatment schemes nationally. The work is being funded by the Department for Environment, Food and Rural Affairs (DEFRA).
How it works
The proposed works consists of the diversion of the water from Level 1 mine entrance and routing it through an underground transfer pipe to two vertical flow ponds (VFP) for treatment. These ponds use the existing bunding of the former mine lagoon and will be lined and filled with a limestone and compost treatment mix. The water will be fed into the top of the VFPs and flow down through the compost mix in the ponds. This will then flow into a wetland vegetated with soft rushes, to provide filtration of any solids, prior to finally discharging into the Coledale Beck
This work is a partnership between the Coal Authority, the Environment Agency, National Trust and Newcastle University.