The environmental impact of abandoned metal mines in the UK

In this post, Anna discusses the environmental impact of abandoned metal mines in the UK, the ramifications this may have on site or property developments, and how Groundsure reports can help you to uncover potential issues and risk.

If you have any questions or comments about this article you can contact the commercial consultancy team at commercial@groundsure.com.

An environmental desktop study of a property identifies the potential environmental liability that may be associated with a property prior to acquiring it. The investigation of historical land uses of a site is an essential part of a desktop study in order to understand possible contaminative features that may have occurred on site, for example, the site could have been used previously as a metal mine.

The UK has carried out extensive mining activity for over 2,000 years. A significant portion of this mining activity has been for the extraction of metalliferous minerals such as lead, zinc, tin, copper and arsenic. Consequently, there are thousands of abandoned metal mines in the UK, some dating back as far as  500 BC [2]. Many different parts of the country are rich in different metals – for example gold mines are usually found in Scotland, copper mines in Wales, and tin mines in Cornwall [1].

Figure 1. Frank Mills mine in Teign Valley region. Small chimney besides a building was probably a crushed plant. (Picture taken on 18/02/2013)

Mine tailings or dump deposits are generated during the mining processes and contain the waste material left over when the valuable metals have been extracted from the ground. Mine tailings can lead to contamination of an area in many ways, but one of the most common is through a process known as acid mine drainage which refers to the acidic water that is created from a mining site.

Pollution due to mining activity lasts for a very long time, and a long defunct mine can still have negative implications for soil/water quality,or the health of plants, animals and humans in the UK today. Nine percent of rivers in England and Wales and two percent in Scotland are at risk of failing to meet their Water Framework Directive targets of good chemical and ecological status due to abandoned metal mines [3].

The most significant pollution threats in the UK from mining are the abandoned mines that have left a legacy of heavy metal contamination of surface water [3]. As the Mining Waste Directive does not cover mining sites closed before 1999, it is difficult to find the organisations “responsible” for pollution caused by these historic metal mines, and therefore attribute liability [4]. Many abandoned metal mines are protected – they are an important reserve of biodiversity and part of our national heritage. Some of these mines have been declared as Sites of Special Scientific Interest or Scheduled Ancient Monuments which makes remediation  difficult [5]. For instance, tin and copper mining areas in Cornwall and West Devon have been designated as a World Heritage Site by UNESCO [6].

So, who is reclaiming and remediating mining sites closed before 1999 and since left abandoned? Currently, the Environment Agency, Scottish Environment Protection Agency (SEPA) and the Coal Authority are working on a solution for this problem, but there is still a lot of work to do [5]. As the mining legislation does not cover issues with historic mining sites, legislation such as the Water Framework Directive and the Part 2A Contaminated Land Regime could be used to remediate these abandoned mining sites [4].

Remediation of mining sites

Remediation strategies for abandoned mining sites are varied and specific to each mine.They can be based on detection of different contaminant sources and minimisation of water movement through source areas and treatment of residual contamination. Remediation of contaminated land processes include three main categories, [9]:

• Physical methods include; removing any hazardous materials, reshaping the land and restoring topsoil.
• Chemical methods with the aim to degrade the pollutants accumulated in the soil or alter their physical-chemical properties.
• Biological methods which consist of using the biological activity of microorganisms and planting native trees or native grasses.

Regarding biological methods, phytoremediation is increasingly important when remediating contaminated land. This method uses plants (trees, shrubs, grasses and aquatic plants) and associated microorganisms to remove, stabilise, and destroy contaminants in the soil and groundwater [8]. To find out more about that topic, visit the blog posted on our website: “Phytoremediation: plants are (always) good to us”.

Case study: The benefits of natural remediation (phytoremediation) in metal mining sites.

Some studies state that the use of vegetation cover in derelict mines could reduce environmental impact and give a cost-effective and environmentally sustainable method of stabilising and reclaiming historical mines [8].

A study I carried out in 2013 looked at the remediation success at the  Frank Mills mine in order to understand the benefits of natural remediation in abandoned metal mines [10]. The Frank Mills mine was one of the richest lead silver mines in the Teign Valley of Devon during the 19^th century and due to past mining activity the area was affected with extensive soil damage, land contamination with heavy metals and visual impact. In 1920, the Lord of Exmouth requested the restoration and revegetation of mine spoil with clean topsoil over a part of the mine which was facing the Lord Exmouth’s private residence in order to improve the view from his private residence (see figure 2).

Figure 2. The area of the study: established woodland (to the north) and the mine spoil (to the south)

Figure 3. Frank Mills mine. South part of vegetated area, which is connected with mine spoil. (Picture taken on 27/07/2013)

Figure 4. Frank Mills established woodland on the part of the spoil heap where soil was added (Picture taken on 27/07/2013)

As we can see in figures 3 and 4, the area which was revegetated 90 years ago has led to self-sustaining vegetation growth and increased biodiversity. Nowadays, the site appears to have been restored in general terms with a reduction of visual impact and a reduction of metal pollution into the environment.

By contrast, the non-revegetated area (see figure 5) still shows: elevated concentration of heavy metals in mine waste which are released into the environment, water contamination and health risk due to exposure to heavy metal concentrations.

Figure 5.  Non-revegetated mine spoil

The study concluded that the revegetated area in Frank Mills mine is an example of successful reclamation technique because a reduction of visual impact and improvement of landscape value were observed at the site. Achieving a successful reclamation is not an easy task and needs time and different techniques according to the site [10].

Groundsure produces a number of reports and insights that can help identify and advise on the level risk related to historical mining activity, click here for more information.

Bibliography

1. (2016) Mining in the United Kingdom in Wikipedia. Available at: https://en.wikipedia.org/wiki/Mining_in_the_United_Kingdom. ( Accessed 19 September 2016)
2. Bowell, R. (2016). The United Kingdom has thousands of Abandoned Metal Mines. Available at: http://www.srk.co.uk/en/newsletter/focus-waste-geochemistry/united-kingdom-has-thousands-abandoned-metal-mines (Accessed 23 September 2016)
3. Environment Agency (2008). Abandoned mines and the water environment. Available at : https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/291482/LIT_8879_df7d5c.pdf . (Accessed on 21 September 2016)
4. Environment Agency, 2013. Closed mining waste facilities causing serious environmental impact: frequently asked question. Available at: http://webarchive.nationalarchives.gov.uk/20140328084622/http://www.environment-agency.gov.uk/homeandleisure/139299.aspx (Accessed on 19 September 2016).
5. The Geological Society of London (2012). Metal mining who pays for the clean up? Available at: Shttps://www.geolsoc.org.uk/Geoscientist/Archive/July-2011/Metal-mining-who-pays-for-the-cleanup (Accessed 22 September 2016)
6. UNESCO World Heritage Centre (1992-2016).Cornwall and West Devon Mining Landscape. Available at: http://whc.unesco.org/en/list/1215 (Accessed 23 September 2016)
7. Tordoff, G.M, Baker, A.J.M, Willis, A.J. (2000) Current approaches to the re vegetation and reclamation of metalliferous mine wastes. Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK. Chemosphere 41 219: 228
8. Environment Agency (2012). Mitigation of pollution from abandoned metal mine drainage. Available at : https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/291553/SCHO1111BUVN_E_E_e40f62.pdf (Accessed 23 September 2016)
9. Hamby, D.M. (1996). Remediation Techniques Supporting Environmental Restoration Activities: A Review. Department of Environmental and Industrial Health. School of Public Health. University of Michigan. Available at: http://www.sciencedirect.com/science/article/pii/S0048969796052643 (Accessed 27 September 2016)
10. Gallart Serral, A.M (2013). Revegetation on mines, learning from 90 years example (Frank Mills mine). Plymouth University. (Thesis submitted to Plymouth University in partial fulfilment of the requirements for degree of MSc Environmental Consultancy). http://primo.plymouth.ac.uk/primo_library/libweb/action/dlSearch.do?institution=44PLY&vid=PLY_VU1&search_scope=44PLY_ALL%2BPC&mode=Basic&displayMode=full&bulkSize=10&highlight=true&dum=true&