Case study:River Nent: Abandoned Metal Mines

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Location: 54° 47' 51.71" N, 2° 23' 11.86" 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

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Project summary

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There have been lead mines in the Nent valley since Roman times, and over 90 mine entries have been recorded throughout the area. As technology advanced in the 1700s and 1800s and longer tunnels and drainage levels could be constructed, the centres of activity became concentrated around Nenthead and Nentsberry. The Nent Force drainage Level was constructed in the 1800s and runs over 7 miles from the Nenthead mines to discharge in Alston. By the 1920s mining had ceased, but during the second world war spoil heaps were reworked for lead and zinc, leaving behind large tailings dams downstream of Nenthead village. In 1998 these were capped and stabilised by Cumbria County Council.

The history and extent of mining here has left large areas of contaminated spoil with little vegetation cover - as a result, spoil is being eroded by the high rainfall and washed into the River Nent. Two sites in the catchment are listed on the MINING WASTE DIRECTIVE INVENTORY since they cause serious pollution. Many of the spoil heaps are protected as Scheduled Ancient Monuments for industrial heritage and/or Sites of Special Scientific Interest (SSSI), as the high metal levels allow unusual calaminarian grasslands to flourish. There are four major mine water discharges which pollute the river with cadmium, zinc and lead, and several smaller discharges in the valley.

The many inputs of metals into the River Nent cause average concentrations of 1,500 ug/l zinc, 3 ug/l cadmium (exceeding the Environmental Quality Standard (EQS) by over 30 times) and 15 ug/l lead (twice the EQS). Due to this very high pollution, very little invertebrate life can live in a 10km+ stretch of the river. The River Nent joins the River South Tyne at Alston, causing it to also fail EQS for zinc and cadmium for 50 km downstream.

Investigations by Newcastle University indicate that the River Nent contributes over 50% of the total load of metals (lead and zinc) reaching the Tyne estuary every year. Reducing the inputs from mines in the River Nent would improve the water quality of the River South Tyne and help reduce the risks to sediment quality in the Tyne estuary. The Environment Agency have teamed up with other partners to look at ways to reduce the polluting effects of the mines on the River Nent, with funding from Defra. We're working with the Coal Authority and Newcastle University to find ways of passively removing zinc from mine water discharges at Nenthead. We're also working with the Tyne Rivers Trust and North Pennines AONB Partnership to stabilise the spoil using metal tolerant plants. This will help reduce the amounts of metal-rich sediments being washed into the river. The Nenthead mines site is a Scheduled Ancient Monument and a SSSI, and we are working with Natural England to monitor spoil erosion and minimise the deterioration of the heritage.

There are so many point and diffuse sources of zinc, cadmium and lead in the area that we're unlikely to be able to achieve EQS in the River Nent itself. However, we hope to be able significantly improve water quality and therefore achieve good status in around 50 km of the River South Tyne.

Impact of mine water discharges in the River Nent (four discharges): • Length of watercourse affected=50km (five water bodies) • Average metal concentration: Zinc = 1.5-6.8 mg/l; Cadmium = 3-12 ug/l • Average flow = 2-14 l/sec • Load of zinc discharged per annum = 25 Tonnes • Water body ecological status = Moderate

Benefits of remediation • The River Tyne will be protected from a major pollution source • A scheduled ancient monument is prevented from being damaged by water erosion • We're developing partnerships with important stakeholders and using our position as an influential advisor to secure shared environmental outcomes • Contribute towards achieving Good Ecological and Chemical status • 25 Tonnes of zinc would be prevented from entering R Tyne every year

Monitoring surveys and results

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Significant water quality monitoring of the River Nent and the point sources discharges from the abandoned metal mines has been carried out by the Environment Agency in recent years.

Lessons learnt

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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 Northumbria River basin Tyne Subcatchment River name Nent from Source to South Tyne Area category 10 - 100 km² Area (km2) Maximum altitude category 500 - 1000 m Maximum altitude (m) 672672 m <br />0.672 km <br />67,200 cm <br /> Dominant geology Siliceous Ecoregion Great Britain Dominant land cover Acid Grassland Waterbody ID GB103023075420 Site Edit site Name WFD water body codes GB103023075420 WFD (national) typology WFD water body name Nent from Source to South Tyne 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) Project started 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 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 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