Environmental surveys throughout the mine’s life cycle
Text: Timo Hämäläinen
GTK makes its fi rst surveys on a mining environment when the mine is in its planning stage and its involvement only ends when the mine is closed down.
– The first surveys are already made when the mining company is preparing plans for the mine and is applying for the environmental permit, explains Päivi Kauppila, Senior Scientist at GTK.
GTK maps the soil and the geochemical baseline of groundwater and surface water, examines the characteristics of the mining waste generated by the operations and prepares reports on the environmental impacts of the mining operations. The information will be used in the environmental permit application.
For the environmental impact assessment, scientists at GTK determine how the waters and waste of the mining area can be managed so that the operations are in accordance with the principle of sustainable development.
– We determine how the waste should be handled and what would be its best location, what would be the suitable disposal method and could the waste be used in some way, says Kauppila.
The environmental surveys will continue when the mine is already operational. The aim is to develop processes that are more effi cient and less polluting.
The closure of the mine and the time after the closure are also considered in the plans. For example, the aim is to ensure that the waste is disposed and processed so that it will not cause any environmental damage after the closure. GTK is also actively involved in the development of other tools and methods for mine closure. Mine Closure Wiki, a wikisite on mine closure was launched last year.
Broad range of different research
The environmental impacts of a mine largely depend on which ore is extracted and how well the waters and waste of the mine are managed.
– There is now more emphasis on water management and active water treatment methods are under development. We have been cooperating with the University of Eastern Finland in the development of methods in which uranium and sulphate are removed from mine water.
Experts at GTK are also examining whether natural processes could be used in water treatment. For example, wetlands could be used to supplement active water treatment methods.
The aim in the KaiHaMe project is to develop waste management methods. The project is funded by the European Regional Development Fund (ERDF), GTK, Kemira Oyj, FQM Kevitsa Mining Oy and Endomines Oy.
The aim is to reduce the amount of waste generated by the operations and their environmental impacts and to increase waste utilization. Benefi ciation tests and lysimeter tests are under way.
The beneficiation tests are carried out at GTK Mintec, GTK´s pilot-scale test plant located in Outokumpu.
Reduction of arsenic content in tailings is one area under investigation in the benefi ciation tests. This would help to reduce the amount of hazardous arsenic waste. One idea is to use tailings to cover other mining waste.
– The smaller the amount of environmentally hazardous waste, the lower the costs arising from processing and disposal of the waste. More effi cient recovery of valuable substances from side streams and wastewater and efficient use of raw materials contained in the ores would help to make production more profi table.
GTK, the National Institute for Health and Welfare and the University of Eastern Finland have jointly developed an integrated risk assessment model for assessing both ecological and health risks.
GTK’s services are also available to customers outside Finland. For example, in Namibia, GTK was preparing a national uranium policy, while in Peru and Tanzania, it has developed environmental management practices for small-scale mining projects.
Cooperating with partners
GTK plans the research requirements in cooperation with its customers (mining companies and consultancies). The areas concerned usually require in-depth research expertise.
Most of the projects are joint undertakings receiving funding from more than one source. In these projects, GTK is co-operating with research institutes, universities, mining companies and consultancies.
GTK is also involved in the development of environmental impact management in a number of major EU projects, such as ProMine and EuRARE.
Tools for sustainable gold mining
The partners in SUSMIN project have investigated and developed tools to support environmentally, socially and economically sustainable gold mining in EU.
The cooperation project, which is coordinated by GTK, involves seven research institutes and universities in different parts of Europe and nine international mining and technology companies.
Gold provides an opportunity for more economic prosperity in Europe. However, there are problems: the low content of gold in ores, the cyanide solutions used in their extraction and the fact that gold often occurs in combination with arsenopyrite. Arsenic is a toxic substance and must not be allowed to spread into the environment.
In the SUSMIN project, GTK has focused on the development of mining environments and enrichment technologies.
– We have developed risk-assessment tools that the mines and authorities can use in quantifying the risks caused by discharge waters, explains Antti Pasanen, Chief Scientist at GTK.
GTK has also developed measuring methods based on electrical conductivity, which allow estimation of mixing in such environments as rivers to be determined.
The method based on the monitoring of stable isotopes provides a tool for determining the sources of the water occurring in a mine.
GTK and its SUSMIN partners will present the results in more detail in the fi nal seminar, which will be held in Finland in October 2016. The reports will be used as a basis for recommendations for the mining industry, environmental authorities and consultancies.
Detecting leaks by means of fibre optic measurements
The DTS method detects weak points in dams through which liquids can penetrate the structure.
GTK applies the DTS method (Distributed Temperature Sensing) to such purposes as the monitoring of temperatures in energy wells and mine dams.
The condition of a dam can be monitored using an arrangement in which an optical fibre cable inside the structure receives laser pulses from a measuring instrument. If the temperature of the measurement point differs from what is normal, liquid has probably penetrated the structure.
Based on the backscattering of the laser pulses, the temperatures can be measured every metre and with an accuracy of 0.1 degrees Celsius. The length of the cable can be several kilometres.
– The method is low-cost with good accuracy. The temperatures can be measured for the whole length of the cable simultaneously, explains Ilkka Martinkauppi, Research Assistant at GTK.
If the temperature of the dam and the liquid are the same, the structure can be monitored by means of the active A-DTS method.
In the A-DTS method, as the temperature is being measured, the fibre cable is heated and the effective thermal conductivity of the structure is determined. Changes in thermal conductivity of the structure give an indication of changes in liquid content.
Depending on the site, seismic signals can also be determined by means of the acoustic DAS method or the DTSS (strain) method, which measures strain and pressure inside the structure.
The broad range of different fibre measurement methods are extremely well suited to continuous and longterm monitoring in urban and natural environments. The contract with the GTK may only include the planning and supply of technology or it may also cover the monitoring of the dam.
– We can also train the customer’s personnel to use the equipment. Monitoring of temperatures can be on the site or by means of remote monitoring. We will provide the customers with monitoring reports, Martinkauppi adds.