North Cornwall, Seaton, Looe and Fowey management catchment: baseline length of rivers and estuaries polluted by abandoned metal mines
Published 12 March 2025
Applies to England
© Crown copyright 2025
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This is one of 20 reports, one for each polluted management catchment, on the water quality monitoring undertaken by the Environment Agency to determine the baseline length of rivers and estuaries considered polluted by any of the Environment Act target substances from abandoned metal mines in 2022.
A length of river or estuary is considered polluted where the concentration of one or more of the 6 target substances (arsenic, cadmium, copper, lead, nickel and zinc) exceeds the relevant Environmental Quality Standard (EQS). EQS concentrations are based on ecotoxicology data and set by Government at a level that should prevent harmful environmental impacts. When the concentration of a substance in a water sample is higher than the EQS, adverse impacts on the aquatic ecosystem can be expected. The relevant EQS for each target substance is set out in The Water Framework Directive (Standards and Classification) Directions (England and Wales) 2015.
The purpose of calculating this baseline was to enable measurement of the statutory abandoned metal mines target set out in Part 4 of the Environmental Targets (Water) (England) Regulations 2023. This regulation requires that the combined length of English rivers and estuaries polluted by the target substances from abandoned metal mines is, by 31 December 2038, at least 50% lower than the baseline.
In the North Cornwall, Seaton, Looe and Fowey management catchment, the baseline length of polluted rivers for the abandoned metal water mines target is 49km. We will aim to identify the key sources of metal pollution in this management catchment by carrying out detailed monitoring investigations.
You can find further background and context on the Environment Act abandoned metal mines water target in the national baseline report which should be read together with this report.
The North Cornwall, Seaton, Looe and Fowey management catchment
The North Cornwall, Seaton, Looe and Fowey management catchment covers an area of approximately 1,326km2 and includes part of the Cornwall National Landscape and the Cornish Mining World Heritage Site. Please go to North Cornwall Seaton Looe and Fowey Management Catchment on the Catchment Data Explorer for an interactive map showing the 5 operational catchments that make up the management catchment. The boundary of the North Cornwall, Seaton, Looe and Fowey management catchment and all 5 operational catchments are highlighted in Figure 1.
Metal mining in the North Cornwall, Seaton, Looe and Fowey Management Catchment
There has been evidence of metal mining in this management catchment since pre-Roman times. The importance of tin mining in the region grew through the Middle Ages and Early Modern Era. In the 18th and early 19th centuries the mining of other metals such as copper and lead also increased, with peak ore production in the middle of the 19th century. To the west of the region, in the Gannel catchment, East Wheal Rose was a major lead, zinc and silver mine. In catchments to the south and west of Bodmin, there were relatively small-scale mining operations for tin and copper in the 19th century. In the Seaton catchment, the Caradon mining district was a key source of tin throughout the Middle Ages and copper during the 19th century, fuelling Britain’s industrial revolution. However, mining operations declined by the end of the 19th century, and mines closed across the region, leaving behind a legacy of pollution.
Figure 1 shows the locations of mineral veins, known mine water discharges, closed mine waste facilities known to be causing serious environmental harm, and recorded areas of abandoned mine wastes (mining spoil) in the North Cornwall, Seaton, Looe and Fowey management catchment.
This information has been gathered from various sources including:
- BGS Geological mapping - GeoIndex - British Geological Survey
- Prioritisation of abandoned non-coal mine impacts on the environment
- Inventory of closed mining waste facilities causing serious environmental impacts
- Defra-funded ‘Source apportionment of pollution from non-coal mines’ research project by Newcastle University and Hull University (unpublished)
- Environment Agency water quality data archive
As we can see in Figure 1, there are 3 main areas of historical mining activity in the North Cornwall, Seaton, Looe and Fowey management catchment: in the Gannel, Porth and Menalhyl operational catchment, in the Camel operational catchment to the south-west of Bodmin, and in the headwaters of the Seaton operational catchment.
Figure 1. Map showing the abandoned metal mines, mineral veins and baseline river monitoring sites in the North Cornwall, Seaton, Looe and Fowey management catchment
© Environment Agency
The tables below list the catchments (surface water bodies) that are polluted by target substances from abandoned metal mines in the North Cornwall, Seaton, Looe and Fowey management catchment. These tables highlight where there are known point sources (mine adits or mine drainage levels) and diffuse sources (mine wastes or spoil heaps) within the catchment. The Environment Agency is continuing to investigate point and diffuse sources within the management catchment by undertaking a series of catchment characterisation studies. These studies will help us identify which sources of metals need to be tackled to achieve the long-term statutory target
Seaton, Looe and Polperro operational catchment: sources of metal pollution
Table 1 summarises which type of pollution sources from abandoned metal mines have been identified within the catchments (surface water bodies) in the Seaton, Looe and Polperro operational catchment.
Table 1: Summary of metal pollution sources within the Seaton, Looe and Polperro operational catchment
| Catchment (Surface water body) | Point sources of pollution | Diffuse sources of pollution |
|---|---|---|
| Seaton | Yes | Yes |
Camel operational catchment: sources of metal pollution
Table 2 summarises which type of pollution sources from abandoned metal mines have been identified within the catchments (surface water bodies) in the Camel operational catchment.
Table 2: Summary of metal pollution sources within the Camel operational catchment
| Catchment (Surface water body) | Point sources of pollution | Diffuse sources of pollution |
|---|---|---|
| Lanivet Stream | Yes | Yes |
| St Lawrence Stream | Yes | Yes |
Gannel, Porth and Menalhyl catchment: sources of metal pollution
Table 3 summarises which type of pollution sources from abandoned metal mines have been identified within the catchments (surface water bodies) in the Gannel, Porth and Menalhyl operational catchment.
Table 3: Summary of metal pollution sources within the Gannel, Porth and Menalhyl operational catchment
| Catchment (Surface water body) | Point sources of pollution | Diffuse sources of pollution |
|---|---|---|
| Benny Stream | Yes | Yes |
Baseline monitoring
The objective of the baseline monitoring was to establish the upstream and downstream extent of surface waters polluted by the target substances from abandoned metal mines. We selected the baseline monitoring sites by first completing a desk study to review previous water quality data, maps and reports. We then made initial site visits to collect samples and to assess the suitability of the site for continued sampling. Generally, at least twelve water quality samples were then collected from each monitoring site.
Within the North Cornwall, Seaton, Looe and Fowey management catchment, water quality monitoring was undertaken in 4 out of the 5 operational catchments. These operational catchments are highlighted in Figure 1. We did not carry out monitoring in operational catchments where there is either no historical metal mining within the catchment or a combination of current and historical monitoring data shows that waterbodies within these catchments are not polluted by abandoned metal mines.
In total, 31 monitoring sites were selected across the North Cornwall, Seaton, Looe and Fowey management catchment to determine the baseline length of rivers polluted by target substances from abandoned metal mines. The locations of these monitoring sites are shown in Figure 1.
Water quality data collected between 1 January 2022 and 31 March 2024 have been used to determine and validate the baseline length of rivers and estuaries considered polluted in 2022. The length of rivers polluted by abandoned metal mines fluctuates in response to natural variation in rainfall and river flows. However, this length will not materially change unless remediation measures like mine water treatment schemes or diffuse interventions are installed to decrease inputs of metals. Therefore, data collected after 31 December 2022 are considered to be representative of rivers, provided no new remediation measures had been constructed since 2022. No new remediation measures have been constructed in the North Cornwall, Seaton, Looe and Fowey management catchment since 2022.
Water quality monitoring results
In the North Cornwall, Seaton, Looe and Fowey management catchment, the target substances measured were cadmium, copper, lead, nickel and zinc. We did not undertake testing for arsenic in this management catchment since historical monitoring data and knowledge of the local geology across the catchment indicated that no rivers are polluted by arsenic in this management catchment.
The baseline water quality data for all monitoring sites are available on the Environment Agency’s public water quality archive.
For a river water quality sample to be considered polluted, concentrations of one or more of the target substances must exceed the relevant EQS set by Government when assessed as an “annual average”. The EQS are set out in The Water Framework Directive (Standards and Classification) Directions (England and Wales) 2015.
The EQS are derived using ecotoxicology data and set at a level that should prevent harmful environmental impacts. When the concentration of a substance in a water sample is higher than the EQS, adverse impacts on the aquatic ecosystem can occur, and the sample is considered to be polluted.
To understand the severity of pollution, we calculated a numeric “pollution level” by dividing the measured concentration of the target substances by the EQS. If the pollution level is greater than 1, the monitoring site is considered polluted by that target substance. Therefore, the higher the numeric pollution level, the greater the likelihood of harm to aquatic life.
Baseline polluted river length: North Cornwall, Seaton, Looe and Fowey management catchment
Our detailed monitoring across a range of flow conditions between January 2022 and March 2024 shows that in the North Cornwall, Seaton, Looe and Fowey management catchment, the baseline length of polluted rivers for the abandoned metal mines target is 49km.
Figure 2 shows the rivers in the North Cornwall, Seaton, Looe and Fowey management catchment that are polluted by target substances from abandoned metal mines.
Figure 2. The baseline length of rivers polluted by target substances from abandoned metal mines in the North Cornwall, Seaton, Looe and Fowey management catchment is 49km
© Environment Agency
Table 4 shows the river length (in km) that are polluted by each of the target substances within the North Cornwall, Seaton, Looe and Fowey management catchment. In general, the most polluted rivers are impacted by more than one target substance.
Table 4. River length (in km) polluted by each of the target substances within the North Cornwall, Seaton, Looe and Fowey management catchment.
| Target substance | Polluted river length (km) | Pollution level: less than 3 times | Pollution level: 3 to 5 times | Pollution level: more than 5 times |
|---|---|---|---|---|
| Cadmium (Cd) | 27 | 13 | 1 | 13 |
| Lead (Pb) | 15 | 2 | 11 | 2 |
| Nickel (Ni) | 14 | 14 | 0 | 0 |
| Zinc (Zn) | 40 | 23 | 2 | 15 |
| Copper (Cu) | 25 | 9 | 11 | 5 |
Rivers polluted by abandoned metal mines: North Cornwall, Seaton, Looe and Fowey management catchment
Seaton, Looe and Polperro operational catchment: baseline polluted rivers
The River Seaton is polluted by copper along the length of the watercourse, except for the compliant Gonamena tributary in the headwaters.
Downstream of Caradon mine, the river is also polluted by zinc and cadmium, with particularly high copper concentrations present at Crow’s Nest. Jopes Adit, a mine water discharge that drains abandoned workings at South Caradon Mine, is a major source of copper, zinc and cadmium to the River Seaton.
Figure 3 shows the baseline polluted rivers in this operational catchment.
Figure 3. The baseline length of rivers polluted by target substances from abandoned metal mines in the Seaton Looe and Polperro operational catchment is 23km
© Environment Agency
It should be noted that due to close proximity of some of the sampling points to each other, some of the sampling point markers on this map (blue squares) may overlap
Camel operational catchment: baseline polluted rivers
The Lanivet Stream is polluted by zinc and cadmium in its lower stretches below Lamorrick to its confluence with the River Camel. The Mulberry tributary is also polluted by zinc and cadmium. The St Lawrence Stream is polluted by copper, nickel, zinc and cadmium from its headwaters to its confluence with the River Camel. However, the St Ingunger and Dragons Pit tributaries are compliant and are therefore not polluted.
Figure 4 shows the baseline polluted rivers in this operational catchment.
Figure 4. The baseline length of rivers polluted by target substances from abandoned metal mines in the Camel operational catchment is 11km
© Environment Agency
It should be noted that due to close proximity of some of the sampling points to each other, some of the sampling point markers on this map (blue squares) may overlap
Gannel, Porth and Menalhyl operational catchment: baseline polluted rivers
Benny Stream is polluted by nickel, zinc, lead, and cadmium below the East Wheal Rose Stream, which is also polluted by the same target substances. Upstream of the confluence of the East Wheal Rose Stream, the Benny Stream is not polluted by any of the target substances. The River Gannel is polluted with zinc, lead and cadmium, below the confluence of the Benny Stream down to its tidal limit.
Figure 5 shows the baseline polluted rivers in this operational catchment.
Figure 5. The baseline length of rivers polluted by target substances from abandoned metal mines in the Gannel Porth and Menalhyl operational catchment is 15km
© Environment Agency
It should be noted that due to close proximity of some of the sampling points to each other, some of the sampling point markers on this map (blue squares) may overlap.