Case study:Gategill Beck: Abandoned Metal Mines: Difference between revisions

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|Partner organisations=The Coal Authority (UK),
|Partner organisations=The Coal Authority (UK),
|Multi-site=No
|Multi-site=No
|Project summary=The Threlkeld mine was worked for lead and zinc between 1661 and 1928. The mine has a long history of causing pollution and fish kills, and the owners were first prosecuted in 1890. The mine is a significant source of heavy metal pollution, particularly cadmium and zinc, in Gategill Beck and the River Glenderamackin, which fails to achieve 'Good' status for the Water Framework Directive. The metal pollution also affects the River Derwent and Bassenthwaite Lake Special Area of Conservation (SAC) and Site of Special Scientific Interest (SSSI). The main source of metals is the Woodend Low Level but there is also diffuse pollution from waste spoil heaps. Until March 2011, the Woodend Low Level drainage tunnel was partially blocked and mine water had built-up behind the entrance. We have now cleared this blockage to prevent an uncontrolled breakout that might have caused a significant pollution incident.
|Project picture=Gategill Beck.jpg
|Picture description=The Wood End low level adit
|Project summary=The Threlkeld mine was worked for lead and zinc between 1661 and 1928. The mine has a long history of causing pollution and fish kills, and the owners were first prosecuted in 1890. The mine is a significant source of heavy metal pollution, particularly cadmium and zinc, in Gategill Beck and the River Glenderamackin, which fails to achieve 'Good' status for the Water Framework Directive. The metal pollution also affects the River Derwent and Bassenthwaite Lake Special Area of Conservation (SAC) and Site of Special Scientific Interest (SSSI). The main source of metals is the Woodend Low Level but there is also diffuse pollution from waste spoil heaps.  


In 2010, we investigated the impacts from the mine with funding from Defra. Our monitoring confirmed that the Woodend Low Level is one of the most polluting mine waters in the UK. In April 2012 we started more detailed monitoring of pollution from the mine using new funding from Defra. To help us, the Coal Authority installed a weir at the Woodend Low Level so we can measure the flow more accurately. We have also built three temporary weirs in Gategill Beck to work out how much pollution comes from the spoil heaps. We are collecting samples monthly for a year to confirm the pollution caused by the mine. We will then work with the Coal Authority to identify what can be done to clean up the pollution.
Since 2010, we have been investigating the impacts from the mine with funding from Defra in partnership with the Coal Authority. Our monitoring confirms that the Woodend Low Level is one of the most polluting mine waters in the UK. Key findings from our monitoring are:
• Immediately downstream of the mine, metal concentrations in Gategill Beck are up to 1,770 times the zinc environmental quality standard (EQS) and 525 times the cadmium EQS. Two km downstream, after dilution in the River Glenderamackin, zinc and cadmium are still up to 30 and 10 times the EQS respectively.
• The mine discharges up to 29 tonnes of zinc, and 91 kg of cadmium each year.
• At higher river flows, the spoil heaps contribute additional metal pollution.
• Up to 16km of the River Glenderamackin, River Derwent and Bassenthwaite Lake fail the EQS for zinc and cadmium, so fail to achieve Good Status.


Key findings from the 2010 monitoring and the 2012 data are:
We're working with the Coal Authority to identify the best way to clean up the pollution with funding from Defra. Initial work has gathered information about how to capture the mine water, and during 2016 we have been reviewing suitable treatment technologies. The minewaters at Gategill are challenging due to their low pH and high metal concentrations which are different from water treated by other full, pilot and laboratory based passive systems in the UK. Passive treatment is still the preferred option but pilot testing may be required and operating costs may be higher than for other passive schemes. The Coal Authority will also investigate potential locations for a treatment system to be built. We will discuss the results of our recommended solution with local stakeholders. Cleaning up the mine water pollution is estimated to deliver environmental and economic benefits of up to £4m over 25 years.  
* Immediately downstream of the mine, metal concentrations in Gategill Beck are up to 1900 times the zinc environmental quality standard (EQS: 8 μg/l) and 375 times the cadmium EQS (0.08 μg/l). Even after dilution in the River Glenderamackin, two kilometres downstream, the zinc and cadmium concentrations are still up to 40 and 8 times the EQS respectively.
* The mine discharges up to 18 tonnes of zinc, and 70 kg of cadmium each year.
* At higher river flows, the spoil heaps contribute additional metal pollution.
* Up to 16km of the River Glenderamackin, River Derwent and Bassenthwaite Lake fail the EQS for zinc and cadmium, and therefore fail to achieve Good Status.


We are working with the Coal Authority to identify the best way to clean up the pollution. Initial work has gathered information about how to capture the mine water, and during 2015 we will be reviewing suitable treatment technologies. The metal concentrations are so high that finding a passive system with low operating costs is difficult. The Coal Authority will also investigate potential locations for a treatment plant to be built. We will discuss the results of our recommended solution with local stakeholders. The estimated economic benefit of cleaning up the mine water pollution is £5.8m over 25 years.
Until recently there was another problem in Gategill Beck. The ‘Yellow Dam’ was created in the 1880’s to provide a water supply and power for mining activities. It consists of a wall and a culvert with mining spoil placed on top to create a dam across the beck. The dam grew weaker with age and the culvert underneath was corroded by the acidic mine water. This meant water built up behind the dam after heavy rain, putting pressure on the structure and creating a small risk that it could collapse. If this happened, any water that had built up behind the dam could quickly flow downstream to flood local properties and part of the A66.  
 
The private owner of the dam was unable to resolve the issue so the Environment Agency worked with Cumbria County Council, Eden District Council, the Lake District National Park Authority and the Highways Agency to identify a solution and funding. During 2014 and 2015, the dam was made safe by lowering the crest height, sealing the culvert and installing a new overflow channel. The Coal Authority paid for the EA contractors to install a pipe through the dam to transfer mine water to a future treatment scheme.


There is another problem in Gategill Beck - flood risk. The Yellow Dam was created in the 1880’s to provide a water supply and power for mining activities. It consists of a wall and a culvert with mining spoil placed on top to create a dam across the beck. The dam has grown weaker with age and the culvert underneath has become defective. This means water builds up behind the dam after heavy rain, putting pressure on the structure and creating a small risk that it could collapse. If this happened, any water that had built up behind the dam could quickly flow downstream to flood local properties and part of the A66. The private owner of the dam is unable to resolve the issue so the Environment Agency is working with Cumbria County Council, Eden District Council, the Lake District National Park Authority and the Highways Agency to identify a solution. Work started in October 2014 to make the dam safe.


Mine water discharge summary
Mine water discharge summary

Revision as of 09:19, 5 January 2017

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Location: 54° 37' 15.38" N, 3° 2' 44.44" 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
The Wood End low level adit

Project summary

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The Threlkeld mine was worked for lead and zinc between 1661 and 1928. The mine has a long history of causing pollution and fish kills, and the owners were first prosecuted in 1890. The mine is a significant source of heavy metal pollution, particularly cadmium and zinc, in Gategill Beck and the River Glenderamackin, which fails to achieve 'Good' status for the Water Framework Directive. The metal pollution also affects the River Derwent and Bassenthwaite Lake Special Area of Conservation (SAC) and Site of Special Scientific Interest (SSSI). The main source of metals is the Woodend Low Level but there is also diffuse pollution from waste spoil heaps.

Since 2010, we have been investigating the impacts from the mine with funding from Defra in partnership with the Coal Authority. Our monitoring confirms that the Woodend Low Level is one of the most polluting mine waters in the UK. Key findings from our monitoring are: • Immediately downstream of the mine, metal concentrations in Gategill Beck are up to 1,770 times the zinc environmental quality standard (EQS) and 525 times the cadmium EQS. Two km downstream, after dilution in the River Glenderamackin, zinc and cadmium are still up to 30 and 10 times the EQS respectively. • The mine discharges up to 29 tonnes of zinc, and 91 kg of cadmium each year. • At higher river flows, the spoil heaps contribute additional metal pollution. • Up to 16km of the River Glenderamackin, River Derwent and Bassenthwaite Lake fail the EQS for zinc and cadmium, so fail to achieve Good Status.

We're working with the Coal Authority to identify the best way to clean up the pollution with funding from Defra. Initial work has gathered information about how to capture the mine water, and during 2016 we have been reviewing suitable treatment technologies. The minewaters at Gategill are challenging due to their low pH and high metal concentrations which are different from water treated by other full, pilot and laboratory based passive systems in the UK. Passive treatment is still the preferred option but pilot testing may be required and operating costs may be higher than for other passive schemes. The Coal Authority will also investigate potential locations for a treatment system to be built. We will discuss the results of our recommended solution with local stakeholders. Cleaning up the mine water pollution is estimated to deliver environmental and economic benefits of up to £4m over 25 years.

Until recently there was another problem in Gategill Beck. The ‘Yellow Dam’ was created in the 1880’s to provide a water supply and power for mining activities. It consists of a wall and a culvert with mining spoil placed on top to create a dam across the beck. The dam grew weaker with age and the culvert underneath was corroded by the acidic mine water. This meant water built up behind the dam after heavy rain, putting pressure on the structure and creating a small risk that it could collapse. If this happened, any water that had built up behind the dam could quickly flow downstream to flood local properties and part of the A66.

The private owner of the dam was unable to resolve the issue so the Environment Agency worked with Cumbria County Council, Eden District Council, the Lake District National Park Authority and the Highways Agency to identify a solution and funding. During 2014 and 2015, the dam was made safe by lowering the crest height, sealing the culvert and installing a new overflow channel. The Coal Authority paid for the EA contractors to install a pipe through the dam to transfer mine water to a future treatment scheme.


Mine water discharge summary

  • Length of watercourse affected: 16km
  • Average metal concentration: Zinc = ~37,500μg/l (up to 18tonnes/yr), Cadmium = 78μg/l (up to 69kg/yr), Lead = 470μg/l, Nickel = 270μg/l
  • Water body ecological status/potential: Moderate (River Glenderamackin, River Derwent) Flow = 6 l/s

Magnitude of impact:

  • Zinc: up to 1,900 times EQS
  • Cadmium: up to 375 times EQS

Benefits of remediation

  • Bassenthwaite Lake SSSI would be protected from a major pollution source
  • The river corridor in a Special Area of Conservation would be improved
  • Ecological improvements would be made to up to 16km of river (Glenderamackin, Derwent)
  • Local properties and infrastructure could be protected from a flooding and pollution event

Monitoring surveys and results

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Catchment and subcatchment

Catchment

River basin district North West
River basin Derwent (NW)

Subcatchment

River name Glenderamackin (Greta)
Area category 10 - 100 km²
Area (km2)
Maximum altitude category 500 - 1000 m
Maximum altitude (m) 863863 m <br />0.863 km <br />86,300 cm <br />
Dominant geology Siliceous
Ecoregion Great Britain
Dominant land cover Acid Grassland
Waterbody ID GB112075070460



Site

Name
WFD water body codes GB112075070460
WFD (national) typology
WFD water body name Glenderamackin (Greta)
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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Reasons for river restoration

Mitigation of a pressure
Hydromorphology
Biology
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Measures

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Monitoring

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