Case study:Gunnerside Gill: Abandoned metal mines
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Project overview
| 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 | |
| Parent multi-site project | |
| This is a parent project encompassing the following projects |
No |
Project summary
Gunnerside Gill, in the Humber River Basin District, is located to the west of Richmond, North Yorkshire in upper Swaledale. The area was mined for lead, zinc and barium between 1700 and 1900. Cadmium occurs as a significant impurity in the lead-zinc minerals. The mineralisation occurs along vertical faults in the Carboniferous Limestone and Millstone Grit rocks at Gunnerside Gill and adjoining areas of Swaledale in Yorkshire, and forms part of the North Pennine Orefield.
There is an extensive legacy of metal mining at Gunnerside Gill including many shafts, adits and drainage levels with several smelters and associated ore dressing floors. There are large areas of unvegetated spoil and bare rock exposed in deep hushes. Some spoil tips, such as at Dolly Mine, have steep unstable slopes that are being constantly eroded at the base by Gunnerside Gill, which also cuts through spoil in dressing floors situated in the valley bottom. Gunnerside Gill catchment (13sq.lm) is entirely within the Yorkshire Dales National Park and almost all of the catchment is co-designated as SSSI, SAC and SPA with some scheduled Ancient Woodland in the valley bottom above Gunnerside village. All of the mine site buildings are derelict, but there are 9 Scheduled Ancient Monuments including parts of the Blakethwaite, Lownathwaite, Bunton, Dolly, Barbara and Sir Francis mines. Bunton Lead Mine is listed on the MINING WASTE DIRECTIVE INVENTORY.
There are 19 adits/levels identified in the catchment, and 2 of these, Bunton Level and Sir Francis Level, were purposely constructed as drainage levels and still have permanent discharge flows, with water containing high concentrations of lead, zinc and cadmium entering Gunnerside Gill. Chemical sampling of the tributary that flows from Kining Level indicates that there may be consistent flows here also. A number of single sampling events to investigate metal pollution of Gunnerside Gill and to establish the Mining Waste Directive inventory were carried out by the Environment Agency and Hull University in 2010 and 2011. These studies all showed concentrations of Pb, Zn and Cd above their respective EQS values of 7.2, 50, and 0.09ug/L (Zn and Cd are hardness based), while Cu, Fe and Mn concentrations were acceptable.
Based on the above findings, a catchment characterisation programme was implemented in 2012-2013 using Defra funding, provided to investigate water pollution from abandoned metal mines. This project comprised monthly water quality sampling and simultaneous spot flow gauging at 6 locations, including the Bunton and Sir Francis Level discharges. An extra location was later added to investigate potential contribution of metal loading from Kining Level. The water quality results showed that the discharges from Bunton Level and Sir Francis Level contained the highest metal concentrations as follows:
Bunton Level average concentrations (ug/L): Pb = 50 Zn = 800 Cd = 8 Sir Francis Level average concentrations (ug/L): Pb = 25 Zn = 1650 Cd = 14
Metal loading was calculated from the concentration and flow data. When metal loadings were examined under different flow conditions, the contribution from the point source adit discharges were more significant during low flows, but less so in high flow conditions, when diffuse sources from spoil tips and re-suspension of contaminated sediments become more significant in the overall metal loading to Gunnerside Gill and entering the River Swale.
The Environment Agency has collaborated with the Yorkshire Dales National Park Authority and funded a heritage survey report, to look at options for remediation and reduction of metal pollution of Gunnerside Gill that do not adversely affect the integrity of the Scheduled Ancient Monuments.
Impacts of metal mining at Gunnerside Gill
Length of watercourse affected 6km to confluence with River Swale Average flow at the Swale confluence 150L/s Average metal concentrations (ug/L): Pb = 30 Zn = 170 Cd = 1.6 Average metal loading (kg/year): Pb = 140 Zn = 800 Cd = 8 Water body WFD status in 2009: Ecology = Good Chemistry = DNRA
Benefits of remediation:
The River Swale will be protected from major metal pollution sources Scheduled Ancient Monuments will not be damaged by any remedial actions Developing partnerships with important stakeholders (YDNPA and Coal Authority) and using our
position as an influential advisor to deliver shared environmental outcomes
Contribute towards achieving Good Ecological and Chemical Status under WFD
Monitoring surveys and results
An ecological monitoring programme was also undertaken to complement the water quality study and
investigate the effects of metal pollution on macrophytes, invertebrates and diatoms. The ecological
surveys were carried out in 3 seasonal sampling events over 2 years. Preliminary results show little
adverse effects on invertebrates and macrophytes, but distortion of diatom valves in some species.
Lessons learnt
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