Case study:The Red River: Abandoned Metal Mines

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Location: 50° 13' 49.07" N, 5° 18' 18.66" W

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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

Dolcoath Mine circa. 1890

Project summary

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The Red River catchment is made up of three waterbodies - the Upper and Lower Red River and the Roseworthy Stream. The river drains a relatively small but intensively mined area of south-west Cornwall. Unlike many of the rivers impacted by metal mines in Cornwall, the Red River is affected not only by the legacy of historic mining throughout the catchment, but also, in the lower catchment, by more recent workings from South Crofty Tin Mine. Whereas most metal mines in Cornwall had ceased working by the early 1900's, 'Crofty' didn't close until 1998 and the site owner, Western United Mines' went into administration in June 2013. However, in July 2016 the Canadian firm Strongbow Exploration Inc acquired the rights to South Crofty, carrying out water treatment tests over winter as the mine will need de-watering.

Historic water quality data shows that Red River waters were severely affected by local mining activities between 1980 and 1998. In particular, waters arising from the South Crofty site during this period contained very high levels of particulate metal pollutants such as iron, zinc, copper and cadmium. The closure of South Crofty mine in 1998 resulted in a significant decrease in total metal concentrations downstream from the working site, although elevated levels of metals continue to arise from waters draining through historic mine workings such as the Treskillard Stream and Dolcoath deep adit discharge. In contrast to these improvements in river water quality, the closure and flooding of South Crofty mine (1998-2000) resulted in significant deterioration in the quality of Red River waters flowing downstream past Roscroggan portal (the Dolcoath adit discharge). Water quality data for the discharge, via Roscroggan portal, show that very high peaks in metal contaminant concentrations (along with additional flows) coincided with the decant of South Crofty mine waters in early November 2000.

More recent work has shown that the upper catchment is dominated by elevated copper from the Treskillard stream which drains abandoned mines from the south east of Camborne, and that under wet weather conditions there are additional inputs from tips and spoil heaps. In terms of impacts, in the Treskillard stream concentrations of Zn, Cu and Cd have been found to be 163ug/L, 363ug/L and 0.42ug/L respectively, with annual load of Zn of 230kg and Cu of 442kg. For the Dolcoath Adit the concentrations of Zn, Cu and Cd are 766ug/L, 23ug/L and 1.42ug/L respectively. The annual load of Zn is 3,400kg, and 106kg Cu.

Waterbody ecological status is Moderate
Length of watercourse affected is 12km
Water quality at WFD point (Gwithian) (ug/l): Zn = 196 (EQS = 75); Cu = 11.8 (EQS = 10); Cd = 0.28 (EQS = 0.15)
Likely bioavailable EQS at Gwithian (ug/l): Zn = 16; Cu = 7

Monitoring surveys and results

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Image gallery

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Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this subcatchment) Catchment River basin district South West River basin West Cornwall and the Fal Subcatchment River name Red River (Upper) Area category 10 - 100 km² Area (km2) Maximum altitude category 200 - 500 m Maximum altitude (m) 241241 m <br />0.241 km <br />24,100 cm <br /> Dominant geology Siliceous Ecoregion Great Britain Dominant land cover Arable and Horticulture Waterbody ID GB108049000600 Site Edit site Name WFD water body codes GB108049000600 WFD (national) typology WFD water body name Red River (Upper) 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 Average bankfull channel width category Average bankfull channel width (m) Average bankfull channel depth category Average bankfull channel depth (m) Mean discharge category Mean annual discharge (m3/s) Average channel gradient category Average channel gradient Average unit stream power (W/m2) Project background Edit project background Reach length directly affected (m) 12km12,000 m <br />1,200,000 cm <br /> Project started 2016/07/01 Works started Works completed Project completed Total cost category Total cost (k€) Benefit to cost ratio Funding sources Cost for project phases Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname Investigation and design Stakeholder engagement and communication Works and works supervision Post-project management and maintenance Monitoring Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Pollution incident, Mine drainage metal concentrations Hydromorphology Biology Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications Floodplain / River corridor Planform / Channel pattern Other Non-structural measures Management interventions Social measures (incl. engagement) Other Improving water quality Monitoring Hydromorphological quality elements Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Physico-chemical quality elements Edit Physico-chemical quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Any other monitoring, e.g. social, economic Edit Other responses Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description Supplementary Information Edit Supplementary Information