This project was completed mainly through the use of questionnaire sent to sub- contractors in almost each country of the EU. To assess this information and to extrapolate to the next twenty years, this approach has been reinforced using published estimators1 on the waste quantity from the knowledge of produced metals.
Mining-selected waste (or simply mining waste) can be defined as a part of materials that result from the exploration, mining and concentration of substances governed by legislation on mines and quarries.
Identification of the environmental risks associated with such waste requires the characterisation and quantification of their different types but also an assessment of the vulnerability of the specific environments contingent upon the geological and hydrogeological conditions and peripheral targets.
1. - Characterisation and quantification of the different types of waste.
This report is based on country-by-country inventory, within the European Union, of sites associated with the management of mining, quarrying and ore-processing waste. It represents the first overview of the current situation in Europe as regards mining waste and presents the current regulatory and management measures specific to each country.
The survey involved two approaches:
- a questionnaire related to the quantities of existing waste, associated with the typology of the mined substance(s), waste deposit(s) and mining systems and ore- processing method(s)
- an estimation, on the basis of the different processes employed throughout the production chain in mining operations and their management at each level, of the main types of waste generated over the last five or ten years.
Comparison between the estimated data with the data obtained from the questionnaires reveals differences in the results that are due mainly to different national regulatory approaches to fill in the questionnaire. Furthermore, legal definitions concerning the types of mining waste, from both the exploitation and processing standpoints may differ in spite of a common glossary defined at the beginning of the study.
For example, certain materials have an important recycling potential within a given environmental and economic framework and are not always considered locally as waste despite the legal definition of waste.
2. - Assessment of risks linked to mining waste.
The notion of environmental impact of mining activities is only fully meaningful if it includes a change in the initial environmental parameters, due to such activities. These parameters, which govern the 'quality of the environment', may have several components: chemical composition of the waters, soils, etc.; biological diversity; visual aesthetic qualities, etc.
The major risks linked to mining waste for the environment are twofold:
Risks associated with not only potential pollutant source (e.g. acidity and heavy metals in non-ferrous metallic ore) but also the specific environmental context and the presence of targets in the event of liberation. The possible risks from the potential pollutant source (such as acidity and heavy metals) in waste is dependent not only on the mineral characterisation of the solid but also on the quality of the potential leachates, the direct environment (soil, groundwater, surface water, air) and the potential targets (human, fauna and flora). The realisation of a Geographic Information System (GIS) specific to mining waste quantities and their pollution potential in different environmental contexts would thus constitute a tool in the assessment of risks linked of such materials. At the moment, such systems are used by some regional governments for the information management on land planning. The risk management with a GIS system in mining requires a considerable collection of specific data and additional series of external analyses. This system should be well defined and studied before to be developed. Then, results can be visualised successfully in the GIS system.
Risks associated with the stability of the tailings dam, as indicated by the recent spectacular accidents in Spain (Aznalcollar) and Romania (Baia Mare). As regards the potential risk from tailings dams, it will be necessary to evaluate on each site the stability of tailings dam. Particular parameters such as exceptional climatological conditions should be carefully taken into consideration during the evaluation. In addition, common minimum safety standards for the design, construction, operation and monitoring should be developed and applied. These minimum safety standards could be built on the know-how of the profession.
3. - Improvement of management of waste.
Mines in all European Union countries are governed by a set of laws, generally combined in a Mining Code. The numerous regulatory texts, laws and standards, reveal that mines are a matter of concern to the national administrations. Mining waste are governed by general waste laws and texts. The extent, to which environmental concerns are addressed in these national laws, varies from Member States to Member States.
According to the contract.s tasks, this report refers superficially to some technical processes, the amounts and types of wastes as well as a short description of the national legislation of the various Member States.
According to the returned questionnaires, a distinction can be made between the following three types of mine and related generated waste:
Operating mines based substantially on old operating methods
Operating mines based on new design.
For abandoned mines, it is important:
- to undertake site monitoring (including land form(s), geology, soil type(s), hydrogeology, flora and fauna, land use, heritage, overburden and waste characterisation, recycling potential, etc.) to obtain a clear picture of the situation
- to establish treatment objectives according to required future land use (for example, pollutant level in soil after treatment to be fixed depending on the proposed land use).
For operating mines based substantially on old operating methods, it is essential to evaluate the control routine as regards pollution risks and the stability of the tailings dams, and to take all necessary measures to limit risks (for example, installing leachate collection tanks, etc.). Substantial changes in the operation and monitoring phases are likely to be necessary to ensure a sufficient level of environmental protection.
For operating mines based on new design, it should be evaluated whether these installations as well as their control routine are sufficient to prevent risks of pollution or accident. Additional measures could be considered if necessary.
The performance of old and new installations in terms of emissions and discharges have to be evaluated in order to see if differences in methods have an impact.
All management of mining waste disposal facilities must taken into consideration long term environmental issues, because these structures will more than likely survive both the mine and the mining company. This raises a legal problem as regards the responsibility for maintenance and repair of these facilities since liability, under most laws, cannot be endless. Even where the facility becomes a permanent structure, it is still necessary to fit the site with a permanent analytical and inspection system. Closure and after care operations are therefore of paramount importance to lower, as far as possible, the long term environmental risks.
Research and development programs should continue around sets of themes specific to the various methods of mining-waste management. Today.s decisions and future research and development must be based on current knowledge (for example results from foreign countries) but detailed further knowledge should be developed on:
- the reactivity of specific mining waste; this could be approached in different ways such as leaching tests, long-term column tests and normalised tests as being developed in the context of the Landfill Directive. Even if there are no international standard, there exist a number of normalised test protocols for static and kinetic tests of acid drainage potential, which is a key characteristic with regards to waste originating from sulphidic minerals
- the behaviour of metallic molecules (originating from mining waste) in the subjacent geologic layers and prediction of their fate using tools such as geochemical and solute-transport modelling, Their behaviour within the waste deposit is also important (adsorption and other attenuation processes)
- the discrimination between geochemical background and mine-impacted soils and waters, • the long term stability of dams
- the improvement of recycling practice related to the characteristics of mining waste
- the potential risks raised by certain covering techniques of tailing ponds (e.g. water cover)
- the process management and protection measures during operation and their subsequent impact on the closure phase.
This report presents the methodology employed, the obtained results and the current status of mining waste in the European Union. The attached CD-ROM presents the replies to the questionnaires filled in by the partners of the study. It also presents the legislation set up in each partner country of the European Union.
The above-mentioned considerations support the initiatives launched by the European Commission to set up an appropriate Community framework to ensure the safe and environmentally sound disposal of mining waste. Needs for coordination, information and specific actions on hot spot are necessary.