Case study:West Allen: Abandoned Metal Mines: Difference between revisions

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Latest revision as of 10:37, 24 May 2017

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Location: 54° 48' 3.64" N, 2° 18' 40.08" 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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The upper reaches of the West Allen have been mined for mainly lead, but also zinc and barium, with the main sites at Coalcleugh at the head of the river and Barney Craig and Scraithole mines at Carrshields about 2kms downstream. Most mining activity took place between the late 1700s and 1920, although a small amount of mineral was extracted from Scraithole mine in the 1980s.

An extensive legacy of mining remains in the West Allen valley. At Coalcleugh there are wide areas of spoil which have become vegetated but still pollute the river and are listed on the MINING WASTE DIRECTIVE INVENTORY. At Carrshields, the west side of the river is bounded by steep spoil heaps from Scraithole mine and these are being gradually eroded by the river. The east side of the river has the retaining wall for the Barney Craig tailings dam as its boundary, and this wall is gradually collapsing into the river. It is only a matter of time before large volumes of metal rich fine material enter the watercourse.

The tailings dam is a Scheduled Ancient Monument that English Heritage have identified as being "At Risk". All three mines have adit discharges with water containing high levels of cadmium, lead and zinc entering the West Allen. The Barney Craig discharge causes the most significant pollution in the river.

A number of studies have been carried out on metal pollution in the West Allen. In 1997, a report by ENTEC for the Environment Agency recommended stabilisation of the spoil heaps at Barney Craig and Scraithole mines; no action was taken due to lack of funds. A PhD study by Emma Gozzard (Newcastle University) in 2008 showed how the mines, particularly the Barney Craig discharge, impacted the whole West Allen, River Allen and South Tyne. This study showed that in higher flows the diffuse sources of metals such as run-off from the tailings dam and re-suspension of contaminated sediments become much more significant in the overall metal loading to the river.

The Environment Agency are working with the Coal Authority and North Pennines Area of Outstanding Beauty to look at options for remediation and reduction of metal pollution in the West Allen. This work is funded by Defra. The first priority is stabilising the Barney Craig tailings dam to prevent a catastrophic collapse. If it happened, this would deposit up to 48,000 cubic metres of spoil into the river, containing an estimated 47 tonnes of lead and 62 tonnes of zinc. At the same time, work will be carried out to limit water ingress to the mine workings - making treatment of the adit discharge easier. This mine is a Scheduled Ancient Monument and we're working closely with English Heritage to preserve the integrity of the site as well as reducing the pollution risk.

Investigations by Newcastle University indicate that the West Allen catchment alone contributes about 20% of the total load of metals reaching the Tyne estuary every year. Reducing the inputs from mines in the West Allen would improve the water quality of the River Allen and help reduce the risks sediment quality in the Tyne estuary.

Impact of the Barney Craig discharge: • Length of watercourse affected = 20km (three water bodies) • Average metal concentration: Zinc = 2.0 mg/l; Cadmium = 3 ug/l • Average flow = 25 l/sec • Load of zinc discharged per annum = 3.5 Tonnes • Water body ecological status = Moderate

Benefits of remediation • The River Tyne will be protected from a major pollution source • A scheduled ancient monument will be prevented from being damaged by high river levels • Risk of a catastrophic collapse of a tailings dam is reduced, preventing 47 tonnes of lead and 62 tonnes of zinc entering the river. • 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 • 3.5 tonnes of zinc would be prevented from entering R Tyne every year

Monitoring surveys and results

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Catchment and subcatchment

Catchment

River basin district Northumbria
River basin Tyne

Subcatchment

River name West Allen from Source to Wellhope Burn
Area category 10 - 100 km²
Area (km2)
Maximum altitude category 500 - 1000 m
Maximum altitude (m) 671671 m <br />0.671 km <br />67,100 cm <br />
Dominant geology Siliceous
Ecoregion Great Britain
Dominant land cover Heather grassland
Waterbody ID GB103023074680



Site

Name
WFD water body codes GB103023074680
WFD (national) typology
WFD water body name West Allen from Source to Wellhope Burn
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
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Average bankfull channel depth category
Average bankfull channel depth (m)
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Project background

Reach length directly affected (m) 20km20,000 m <br />2,000,000 cm <br />
Project started 2008
Works started
Works completed
Project completed
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Benefit to cost ratio
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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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Works and works supervision
Post-project management and maintenance
Monitoring



Reasons for river restoration

Mitigation of a pressure Pollution incident, Mine drainage metal concentrations
Hydromorphology
Biology
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications
Floodplain / River corridor
Planform / Channel pattern
Other Reduce pollution risk
Non-structural measures
Management interventions Remediation Treatment
Social measures (incl. engagement)
Other Improving water quality


Monitoring

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Biological quality elements

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Physico-chemical quality elements

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Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative


Monitoring documents



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Supplementary Information

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