Coombe mine water treatment scheme
Information about the Coombe mine water treatment scheme in Cornwall, England.
In the South West of England, monitoring by the Environment Agency shows that about 500km of rivers are polluted by metals from abandoned mines.
In the Fal catchment, a significant source of pollution is the Coombe Adit, an abandoned mine water drainage tunnel that pollutes about 14km of the Coombe Stream, Gwindra Stream and River Fal with zinc, copper and/or cadmium.
The Coombe Adit discharges into the Coombe Stream, approximately 800m east of the village of Coombe and 5km to the west of St Austell, in Cornwall.
Although the water is discharging from a former tin and copper mine, the water also contains high levels of other naturally occurring metals, such as iron and manganese, although these do not cause significant river pollution.
When mine water is released into a river, the iron that is present in the water settles on the bed of the river causing orange staining. Treating the Coombe Adit mine water discharge will significantly improve water quality in 14km of rivers for people and wildlife, and help to achieve the ‘good status’ target in the South West River Basin Management Plan.
The mine water treatment method
An innovative treatment technology will remove the metals from the Coombe Adit discharge.
This technology, known as a Vertical Flow Reactor (VFR), was developed by Cardiff University.
The mine water passes down through a bed of gravel that encourages the iron and manganese in the water to precipitate out and coat the gravel with iron hydroxide, also known as ochre. This coating is very effective at capturing the cadmium, copper and zinc in the mine water.
As this is a new technology, we are trialling a small scheme that will only treat a portion of the full mine water flow. This pilot treatment scheme will provide useful information about the technology, which has a relatively small footprint when compared to alternative methods of treatment, and will allow us to develop a full-scale scheme for the discharge over time.
This is a completely passive treatment technology which means we do not have to add any chemicals or use power to operate the scheme.
Planning permission for the pilot mine water treatment scheme was granted by Cornwall County Council in February 2020 and construction began in February 2022. You can look through the planning application on the Cornwall County Council website, using the reference: PA19/09690.
View the planning application decision on Cornwall County Council’s website
The pilot scheme will initially run for around 2 years. Depending on how it performs, we may need to extend the trial period and if we want to build a larger full-scale scheme we would need to submit a new planning application.
View past updates about the Coombe mine water treatment scheme.
This project is part of the Water and Abandoned Metal Mines programme that aims to tackle water pollution caused by historical metal mining.
Read more about the work of the Water and Abandoned Metal Mines programme
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Updates to this page
Last updated 6 July 2022 + show all updates
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Updated with when scheme construction began.
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First published.