The Perama gold deposit and Project
The oxidized gold deposit at Perama consists a typical deposit of low sulfidation which is located in sedimentary rocks of Eocene to Oligocene age. It is located in Northeastern Greece, on the border of the Evros and Rodopi prefectures. The mineralization of gold has been supplied through a tectonically controlled system of fractures in andesites, to the highly porous arenaceous caprocks. Eighty percent of the mineralization is located in sandstones and the rest is connected with andesite breccias and conglomerates. The deposit of Perama does not contain As (arsenic), Pb (lead) or other heavy metals.
The project is located in a non-residential area, of a low agricultural and forestry production value in the prefecture of Evros in Thrace. It lies at approximately 5km from the sea, 28km from the port of Alexandroupoli, 15 km from Makri, 7 km from Mesti and 0.5km from the village of Perama. The intervention area of the project does not exceed 0.742 square kilometers in total making it one of the smallest mines in the world.
Its design is in full compliance with the Directives of the European Union on Best Available Techniques and Mine Waste Disposal, which are based on the principle of “zero discharge” to the environment (deposition of solid filter cake residues, dust elimination, water recycling), and, of course, with the Greek legislation.
During the operation of the Project, the ore will be transported from the open-pit mine to the ore collection area of the plant. There it will be crushed and pulverized – through a closed system of dust retention – at a percentage of 80% in particles of a size of 100 microns (0.01 centimeter) and will be mixed with water. Τhe extraction of the ore will follow, with the use of a sodium cyanide solution within tanks and the collection of gold. After this process, which is called cyanide leaching, the destruction of cyanides of the tailings follows (tailings are named the residues of the above process) with the INCOTM method (SO2/oxygen), as well as the densification and dehumidification of the slurry in filter presses and finally its deposition to the Tailings Impoundment Site.
The phases of the Project’s implementation
The implementation schedule of the project consists of 3 phases.
The first phase is the construction of the project and its duration will be 18 months at least.
The second phase, the duration of which is estimated to 8 years, includes the process of exploitation of the gold deposit with open-pit excavation, and the “extraction” of precious metals (gold and silver) with a hydrometallurgical method in the presence of activated carbon. The operating specifications of the project that are provided for by the legislation ensure the total elimination of dust, with water spraying at the points of excavation and of transport of the ore. At this stage this ore is processed in a sodium cyanide solution that has the property of separating gold and silver from the rest of the rock. Afterwards, the gold deposit goes to the extraction circuit with electrolysis for the production of a gold and silver alloy (Doré). The rest of the material is subjected to a process of cyanide neutralization, with the use of the INCOΤΜ method, after which the final cyanide content is less than 1ppm, that is less than 1 gram per ton, 10 times less than what is required by the European legislation. The material, which is now pure, passes through filter presses, is compressed, dehumidified and a dehumidified solid residue with a humidity of 15%, the so-called filter cake, remains. Water from the filter press is recycled back to the production process, offering high water consumption savings, since 93% of the required water quantity comes from recycling. The filter cake is transported to the sealed repository. In a former design of the project there was the provision of a tailings pond which would cover an area almost double than the one of the present repository, but with the actual design, this is avoided. The commitment of the company that not even a cubic meter of water that is useful for irrigation or drinking of the villages and the entire area will be used, must be pointed out.
The third and last phase of the life of the project will have a duration of 1.5 years and will include the safe closure of the mine as well as the environmental rehabilitation of the activity areas with the dismantling of the gold plant infrastructure and of all the auxiliary installations and the parallel plant cover of the area with suitable endemic flora species. The final form of the rehabilitation plan will be agreed with the local authorities, however, the afforestation of a large part of the intervention area is certain, as well as the development of innovative agricultural cultivation. For this purpose, the construction of a nursery at Perama has already began in cooperation with the Democritus University of Thrace, where a large number of Black Pine trees of the area as well as many other species will be produced.
The proposed eight year exploitation regards the oxidized part of the Perama gold deposit. During the second phase, exploration works in the non-oxidized part of the gold deposit will be performed, which will extend the lifetime of the mine for many more years, after the appropriate environmental authorization.
In the period of the project’s infrastructure construction, up to 350 people will be employed, the largest part of which will be employed at the mine’s operation phase. Greek as well as foreign experts will undertake to train the personnel.
The permanent personnel during the operation of the mine is estimated to 200 persons. The company is committed regarding the maximum utilization of the local workforce, either through direct or through indirect employment. At least 90% of the recruited people will come from the workforce of the local area with the parallel training of the staff during the construction of the project.
Training will be continuous, throughout the project, depending on staff specialty, emphasizing the environmental education and first aid provision.
The continuous development and improvement of the technical skills of the employees will be useful to them after the completion of the Project also.
The Project will create jobs in the area with the development of parallel supporting activities such as maintenance works, fuel supply, the provision of services, supplies, catering and accommodation services, transports, the supply of spare parts, etc., in the areas of Sapes, Komotini and Alexandroupoli. It is estimated that the operation of the Project will create a turnover of approximately 105 million euros at a local level.
The company will spend, during the lifetime of the project, almost 6 million euros for the support of the local community. Additional resources will be available for the development of the socially useful infrastructures of the area, of education and research.
The revenues from the Perama Gold Mining Project are estimated to 660 million euros. Furthermore, it must be remarked that the taxes (40%) from the operation of the Project are estimated to 260 million euros and consist a reasonably significant contribution of the Project to the national economy (the estimation has been made using a gold price of 1,400 dollars per ounce). It is also quite important to remark that it is estimated that approximately 70% of the capital investment and 100% of the operation cost will remain in Greece, and more particularly in the area of Thrace, in the form of salaries, services, supplies, engineering works, transports, power supply, etc.
The Perama Gold Mining Project, according to the social cost-benefit analysis study that has been prepared by the National Technical University of Athens (2003, prof. K. Panagopoulos, D. Kaliabakos), is considered socially beneficial in economic terms. The environmental dimension has been also taken into account in the analysis. The two economic figures, the Social IRR (Internal Rate of Return) and the Social NPV (Net Present Value), which have been measured on a social basis, are positive in all evaluation scenarios.
Mining and Processing
Due to the surface position and the geometry of the deposit, a closed-type open-pit mining method has been planned. The excavation will be performed in 26 five-meter benches and the total slope angle will be 37.5°- 32° for the east slope and 31°- 35° for the west slope. The hydrometallurgical processing of the ore which will be based on the principle of zero discharge to the environment will take place. The main processing features are the following:
- Processing of 3,288 ore tonnes per day, 24 hours a day, 365 days a year.
- Crushing and milling of the ore in a closed circuit, to a size less than 100 microns.
- Gold is dissolved with the use of a Sodium Cyanide (ΝaCΝ) solution in thickener tanks.
- Gold is absorbed on the surface of the activated carbon chips.
- Sodium cyanide is used in a closed circuit and reused in the production process.
- Detoxification of tailings with the INCOTM (SO2/oxygen) method at content levels < 1ppm CN.
- Thickening of the slurry and dehumidification in filter presses.
- Recycling of water from the filter presses and reuse in the production process (closed circuit).
- Deposition of the dehumidified tailing (filter cake) (85% solid residues content by weight) at a specially designed watertight area.
- Recovery of 90% of the gold and 60% of the silver.