Case study:River Seaton: Abandoned Metal Mines

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Location: 50° 30' 50", -4° 27' 14"
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Project overview

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Status In progress
Project web site
Themes Environmental flows and water resources, Habitat and biodiversity, Monitoring, Water quality
Country England
Main contact forename Hugh
Main contact surname Potter
Main contact user ID
Contact organisation Environment Agency
Contact organisation web site
Partner organisations The Coal Authority (UK)
Parent multi-site project
This is a parent project
encompassing the following
projects
No
Waste tips at South Caradon mine

Project summary

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The Seaton catchment is heavily impacted by historic mining activity throughout its entire length, but especially in the upper reaches around South Caradon mine. The mine is located on the South Eastern edge of Bodmin Moor in South East Cornwall. It is cut through by the River Seaton which is fed by groundwater as well as surface runoff during heavy rain events. Ore processing at South Caradon mine started in 1838, at which time the mine covered most of the south side of Caradon Hill, and finished in 1890. When South Caradon finally closed it left miners with no prospects of work anywhere else in the Duchy. Many went to England to find work in factories or coal mines, but large numbers emigrated to work metal mines all around the world. From the remains on the site and documented history, it is known that the processing of material from the mine shafts was carried out within the River Seaton valley. River water from the Seaton was used in the separation process, and waste water with a high concentration of metal solutes, sand, and silt-sized particles, was discharged directly into the River Seaton. Processing of Cu bearing ore at South Caradon mine involved the heating, pulverizing and dissolving of metals and their compounds, resulting in release of Cu and Zn into the surrounding environment. The legacy of these processes is a proliferation of tips, disused shafts and 3 adit discharges which between them contribute high levels of Zinc, Copper and Cadmium to the river. When water quality and flow data are combined, it is evident that the most important sources of Cu, Cd and Zn contamination in the River Seaton are Jopes Adit, and the ‘3 Adit Streams’ . Although the 3 Adit Streams discharge from beneath a rock tip, the chemistry results indicate that the 3 Adit Streams and Jopes Adit discharges are related in terms of source. Tip run-off is an additional significant source of Cu, Cd and Zn entering the main stream, particularly in prolonged heavy rain conditions. The site is listed on the MINING WASTE DIRECTIVE INVENTORY (http://apps.environment-agency.gov.uk/wiyby/139297.aspx) since the wastes cause more than 500 metres of the river to be polluted. Most of the mine site is designated as a Site of Special Scientific Interest (SSSI) since the high metal concentrations in the soil support specialised flora of rare mosses and liverworts. This is one of two sites in the world where the Cornish path-moss occurs. The Caradon Mining District is part of the CORNISH MINING WORLD HERITAGE site (http://www.cornish-mining.org.uk/areas-places-activities/caradon-mining-district). IMPACT OF THE JOPES ADIT DISCHARGE Length of watercourse affected - 17km. Average metal concentration in the mine water: Zinc 510ug/l; Copper 1180ug/l; Cadmium 1.5ug/l. Average flow - 56 l/sec. Load of Zinc discharged per day - 2.5 kg. Load of Copper discharged per day - 5.8 kg. Water body ecological status Poor. WFD Compliance The whole river length from headwaters to tidal limit is non-compliant with Water Framework Directive Standards for copper. For zinc and cadmium at least 4.5km of river are non-compliant with the WFD standards. The WFD monitoring site at Hendra Bridge is below all the main impacts and most recent mean levels here are: Cd 0.185ug/l (EQS = 0.08); Cu 75ug/l (EQS =1); Zn 67ug/l (EQS = 8). All these are non-compliant with copper being approximately 75 times the standard for good status, whilst cadmium (a Priority Hazardous Substance under the WFD) concentrations are double the amount needed to achieve good status. BENEFITS OF REMEDIATION The River Seaton will be protected from a major pollution source. Contribute towards achieving Good Ecological and Chemical status. 912 kg of Zinc and 2,100 kg of Copper would be prevented from entering the River Seaton every year. The Environment Agency is working with the Coal Authority to develop remedial options to address the pollution and return the river to good status. At the current time (August 2014), we are not able to say when we will be able to start work on cleaning up the river.

Monitoring surveys and results

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Lessons learnt

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Image gallery


Jopes Adit, South Caradon mine
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Catchment and subcatchment

Catchment

River basin district South West
River basin North Cornwall, Seaton, Looe and Fowey

Subcatchment

River name River Seaton
Area category 10 - 100 km²
Area (km2)
Maximum altitude category 200 - 500 m
Maximum altitude (m) 365
365 m
0.365 km
36,500 cm
Dominant geology Siliceous
Ecoregion Great Britain
Dominant land cover Arable and Horticulture
Waterbody ID GB108048002320



Site

Name
WFD water body codes GB108048002320
WFD (national) typology
WFD water body name River Seaton
Pre-project morphology
Reference morphology
Desired post project morphology
Heavily modified water body No
National/international site designation
Local/regional site designations
Protected species present No
Invasive species present No
Species of interest
Dominant hydrology
Dominant substrate
River corridor land use
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Average bankfull channel depth (m)
Mean discharge category
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Average unit stream power (W/m2)


Project background

Reach length directly affected (m) 17km
17,000 m
1,700,000 cm
Project started
Works started
Works completed
Project completed
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Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design
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Monitoring



Reasons for river restoration

Mitigation of a pressure Pollution incident, Mine drainage metal concentrations, Not meeting WFD standards for Copper
Hydromorphology
Biology
Physico-chemical Nutrient concentrations
Other reasons for the project


Measures

Structural measures
Bank/bed modifications
Floodplain / River corridor Water treatment methods
Planform / Channel pattern
Other Improving water quality
Non-structural measures
Management interventions
Social measures (incl. engagement)
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Monitoring

Hydromorphological quality elements

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Physico-chemical quality elements

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Any other monitoring, e.g. social, economic

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Monitoring documents



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Supplementary Information

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