3.1.3 Mining

3.1.3 Mining

Overview

Mining has been undertaken in Europe for many hundreds of years. Today many mines have been closed but both recent and abandoned mines still affect the quantitative, chemical and ecological quality of water. This section covers both mining and extraction (gravel, peat) activities.  Main pressures and impacts include acidification caused by lowering pH and discharge of heavy metals, other chemical pollution or pollution resulting by saltwater intrusion, alteration in flow, or lowering water table caused by an excessive dewatering during mine operation or after mining activities have stopped. Recovery of affected aquatic ecosystems – including groundwater - may take decades.

In the 2^nd RBMP, 17 WFD countries reported mining as significant point and/or diffuse source pressure, affecting ca. 1 100 surface water bodies (less than 1 % out of all surface water bodies), and 7.5 % of the whole groundwater area. Countries with high shares of reported pressures from mining included the UK, Norway, Germany, Hungary, Bulgaria, Spain, and Italy.

Other analyses of mining pressures and their potential risks to water show a slightly different picture due to the use of other sources of data. In Figure 5 below, countries are scored based on mining activities (existing and abandoned mines) and Czechia, France, Germany, Poland, Romania, Sweden, Spain and United Kingdom are the Member States with the highest potential risk of mining pressures (WRc, 2012).

Figure 5             Potential risk of specific mining activities in European river basin districts

Notes: Data source: DECHMENUE, E-PRTR; source: European Commission – Eurostat/GISCO; ESRI, 2003; EEA data service based on various data providers.

Source: http://ec.europa.eu/environment/archives/water/implrep2007/pdf/techn_note_mining.pdf.

Mining activities include the extraction of coal and lignite, minerals mainly potassium, rock salt and magnesium-containing minerals, clay, peat, metals such as copper and gold as well as stones, gravel, or sand (aggregates). It is estimated that in EU more than 32 000 sites with mining activities exist, of which more than 25 000 are used for the extraction of aggregates, with the highest numbers of sites in Poland and Germany. The number of peat extraction is some 1 400 sites of which 75 % is located in Finland (EU, 2018).

On the number of abandoned mines, European-wide data are rare, e.g. (EC, 2017a), and the number of abandoned mines is likely to be much higher than of active ones based on available data on certain countries, like Slovakia and Hungary. Slovakia has registered more than 17 000 and Hungary has reported some 6 000 abandoned mining sites (UNCCD, 2000). The bulk of mine water problems in Europe are in fact associated with abandoned mining sites and in numerous catchments, the single greatest cause of freshwater pollution is pollution from abandoned mines (ERMITE-Consortium et al., 2004).

Impacts

Main impacts to aquatic ecosystems are changes in surface and groundwater hydrology, sediment load, water quality, acidification and alteration in stream habitat and morphology (Figure 6).

Figure 6 Impacts of mining activities on water 

Notes: Insert notes here

Source: http://ubclfs-wmc.landfood.ubc.ca/webapp/WID/course/land-use-impacts-on-water-3/mining-impacts-16/ .

All types of mining have the potential to directly disrupt groundwater hydrology, which in turn can affect surface waters that are in hydraulic continuity with the affected groundwater systems (ERMITE-Consortium et al., 2004). This is mainly due to dewatering resulting in a depression of the water table around the dewatered zone.

The water quality of mining activities is mainly affected by acidification or salinization. The acid runoff further dissolves heavy metals such as copper, lead, mercury into groundwater or surface water. Problems that can be associated with mine drainage include iron hydroxide precipitation during oxygenation of mining water, contaminated drinking water (e.g. with metals or sulphate), impacts on aquatic plants and animals, or the corroding effects of the acid on parts of infrastructures ([1]). Salinization is caused by the extraction of salts, e.g. potassium. High salt content altered aquatic communities and salt intrusion into the groundwater can endanger the quality of drinking water.

[1] Source: https://www.usgs.gov/special-topic/water-science-school/science/mining-and-water-quality?qt-science_center_objects=0#qt-science_center_objects; 14.05.2019

Placer mining or gravel extraction, and lead to increased sediment loading and decrease water clarity. Furthermore, hydromorphology is impacted by replacing coarse substrates such as gravels and boulders resulting in fewer invertebrate species.

Impacts of the removal of peat are increased sedimentation, increasing dissolved organic carbon (DOC) and phosphorus concentration, and decreasing pH values in the receiving waters (Lundin, et al., 2017; Ramchunder, et al., 2012). The leaching of phosphorus and nitrogen causes eutrophication problems into the watercourses or lakes and the load of solid peat particles causes silting of downstream water bodies.

Hydraulic fracturing to extract shale oil or shale gas potentially threatens drinking water resources (mainly groundwater) with the contamination with chemicals used in the hydraulic fracturing process. Surface water contamination can occur if the wastewater, containing the chemical additives as well as saline water and naturally occurring heavy metals and radioactive materials from the shale formations, is not properly managed and treated (Umweltbundesamt, 2012). Based on the shale gas information platform by EC, the UK is the only country in Europe, where companies pursue hydraulic fracturing (which is haltered since 2019)([2]), whereas a ban in France and Bulgaria and tests in Poland occur ([3]). In Estonia, mines cover ca. 1 % of the whole territory and about 16 million tonnes of shale oil were extracted in 2012 with high impacts on waters ([4]).  

Mining accidents can have tremendous impacts to the aquatic environment, for example the spill of cyanide rich waste water in Baia Mare, Romania in 2000. After a dam brake in the retreatment plant of gold mining company, large number of fish were killed in the Somes River, and also Tisza River and Danube. Furthermore, drinking water resources were contaminated (UNEP/OCHA, 2000).   

([2]) Source: https://www.theguardian.com/environment/2019/nov/02/fracking-banned-in-uk-as-government-makes-major-u-turn

([3]) Source: https://ec.europa.eu/energy/topics/oil-gas-and-coal/shale-gas_en

([4]) Source:  https://www.academia.edu/4412537/Poster_of_Analyses_of_Estonian_oil_shale_resources

Measures and management challenges

Measures to reduce pressures from mining activities for surface waters include re-use or recycling of excess water, diversion of run-off systems, or the use of reagents or chemicals with a low environmental impact, drainage systems, removal of suspended solids or liquid particles, or removal of dissolved substances by e.g. adsorption or nanofiltration. For groundwater, physical barriers, drainage systems techniques, or covering techniques are listed as effective measures to protect aquatic ecosystems (EU, 2018). These measures are part of the BAT (best available techniques) for the management of waste from extractive industries, which need to be implemented in EU Member States targeted by the Extractive Waste Directive (EWD) (2006/21/EC). According to Article 5 of the EWD, operators have to submit an extractive waste management plan (EWMP) as part of their permit applications.

After closure of mines, restoration is foreseen to rehabilitate impacts of former activities to soil and water. Many countries have national plans, like the rehabilitation for the Avoka river in Ireland ([5]) or  the Landscape Evaluation Tool for Open Pit Mine Design in Greece (Mavrommatis, and Menegaki, 2017). In Saxony, Germany, numerous post-mining lakes were created as part of the brown coal refurbishment. Most of these lakes are already being used for tourism purposes ([6]).

([5]) Source: http://www.mineralsireland.ie/MiningAndTheEnvironment/Rehabilitation.htm

([6]) Source: https://www.bergbau.sachsen.de/8193.html

Current mining activities are strongly regulated by Member States under National Laws. In most countries, Water Acts and Water Laws include protection of waters from mining activities. Additional legislations and regulations are implemented for the protection of groundwater, e.g. decree on activities that affect the quality of groundwater in Hungary or the Groundwater Exploration Act in Sweden (Endl, and Berger, 2016). The legislative instruments on international and national level regulating the current mining sector should ensure that the objectives of the Water Framework Directive (2000/60/EC) and Groundwater Directive (2006/118/EC) are achieved (WRc, 2012).

Measures under the WFD also aim at reducing water abstraction related to mining which is commonly used to control quantitative impacts from quarrying activities but could also be of use for deep mining (underground mining). Measures controlling substances are specific to individual substances, diffuse pollution or point source pollution. For example, to reduce diffuse discharge from saline waters into groundwater, K&S company in Germany covers the salt tailing piles and uses chemical transformation processes to treat the waste water. It is estimated, that this will reduce the proportion of saline wastewater by 20 % (^[7]).

Data on implemented measures under the WFD and under the EWD are rare. In the context of the WFD, information on mining is part of different reporting obligations, e.g. WFD emissions inventory, pressures characterisation of water bodies or the failing of Environmental Quality Standards for e.g. heavy metals caused by mining activities for chemical (priority substances) or ecological status assessment (river basin specific pollutants). If mining activities cause significant pressures putting at risk the achievement of WFD objectives for surface water or groundwater, measures need to be included in the RBMPs. In the context of the EWD, mining operators have to draw up an extractive management plan (EWMP) as part of permit applications. Among other issues, EMWPs should cover the monitoring of surface and groundwater quantity and quality and the management of excavated material as well as mining waste (EC 2019f). Due to the relevance of both Directives to the assessment and management of water risks due to mining, a more synergistic way of gathering information and developing management strategies and measures for mining activities would be beneficial. 

([7]) Source: https://www.kpluss.com/en-us/sustainability/environment/water/