Case study:River Nent: Abandoned Metal Mines

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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

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