Minera Los Frailes (MLF) – a company of Grupo México , as the majority shareholder, and Magtel, to which the Aznalcollar exploitation was awarded in 2015 – highlights that one of the singularities of the operation is the environmental requirements, by the Spanish legislation itself and the conditions of the contest, given the precedent of the toxic spill and the state of the deposit when Boliden left, in 2001. “This is an environmental restoration project supported by a mining operation ,” he defends.
Whether the concept is correct or not, the truth is that the situation of the complex is unsustainable in the medium term if it is not intervened in some way and has long entailed costly management. There are two open pit mines: Aznalcollar, where there is also the sludge from the discharge and waste that was generated in the years that Boliden continued to operate later, to which acidic water is pumped due to contact with dumps; and that of Los Frailes, where other runoffs go. There are two dumps (the East, which has 196 hectares, and the Northwest, with 240), mountains of material, most of which have not been restored, at the head of the Guadiamar Corridor, and the remains of the raft that exploded in 1998.
Maintaining this environmental liability already costs 2.5 million euros a year. The Board assumed it when Boliden left, but after the contest, it was passed on to the successful bidder. Hence, one of the keys to the project – again on public display for the Unified Environmental Authorization, until mid-December – is the Environmental Restoration Plan , once the useful life of the mine has ended, estimated at 17 years to which it would be necessary to add another three from the construction phase of the new complex.
Integrate more than 2,100 hectares in the Green Corridor
The goal, after all that and according to the available documentation, is to integrate more than 2,100 hectares of land into the Green Corridor. Although this restoration must also close a sad chapter in terms of the impact of mining in Andalusia and become a reference for other projects , when new mining technologies and methods open up the possibility of recovering other old exploitations in the Iberian Pyrite Belt.
The proposed MLF Restoration Plan will cost almost 30 million euros . It proposes to rehabilitate the area as a natural space with a predominance of forest land, which was the majority before the implementation of the mine in the 70s, with the possibility of a “controlled recreational use, linked to a rehabilitated mining space as a natural space”, turning the pits into “mining lakes”, “encapsulating” before the toxic remains that are in the Aznalcollar, according to what is collected.
It is expected that, with the new mining activity, one of the dumps, the Noroeste, will only grow by 5%. Because more than 90% of the waste, which has contact with the mineral, will be used this time mixed with cement and sludge from the water treatment plant to make the “paste” with which the underground chambers will be sealed as it is extracted. the ore and the Aznalcollar mine itself. That restoration will now run parallel to the advance of exploitation.
The dumpster restoration plan foresees that, also from the beginning, perimeter channels be created to redirect the water and other measures to reduce the contact of runoff with the material and the need to pump to the Aznalcollar cut or to treat the water before discharge.
Technosols to recover the soil
However, the most outstanding to act both in the soils of these dumps and in the future mining lakes are the “technosols”, a system developed by the University of Santiago de Compostela that was used in an initial phase in the recovery of the Guadiamar corridor.
These are “Ã la carte” or “intelligent” soils, made from organic and inorganic waste, to “emulate” the characteristics of the land necessary for an area, so that they adapt and work faster than they would otherwise. nature itself to correct and regenerate the space. They have been used in the Touro polymetallic sulphide mine in Corunna and, in Aznalcollar, they will be produced in a mobile plant within the same complex, using organic waste from the surrounding area, some 100 kilometers around.
“Everything that the most suitable natural soil for a specific function can do, a tecnosol can also do more efficiently and quickly, if it is properly designed and elaborated and with precise knowledge of the limitations of the system to be recovered”, it was stated. collect in the project.
There are seven types planned for Aznalcollar, depending on the area and the effects you want to counter.or enhance, such as neutralize acids, control the entry of oxidants, stimulate microorganisms, stop erosion or stimulate water retention. They will be used in the recovery of the vegetal cover and the slopes of the fellings, once stabilized and above the level of water. Revegetation will be carried out on them, with pine trees, holm oak, wild olive, mastic, broom or rosemary, among other species.
The solution will also be applied to the rehabilitation of the Northwest dump and the improvement of the East, as well as in areas of mining installations, in the biofilters (reactive wetlands that the restoration project also contemplates) and in lands that will be reforested in the old industrial area south of the A-477. With regard to revegetation, as a singular element, a “plant screen treatment” is planned, based on Aleppo pine and mastic, around the Gerena-Aznalcollar highway and the intermediate areas located north of the mining facilities, as well as in the area located to the south and southeast of the Aznalcollar cut.
The cut of the sludge
The Los Frailes Mining Project contemplates that the Aznalcollar quarry be used as a deposit for the “tails of the process” or waste, thus avoiding the construction of a pond like the one that burst in 1998 and gradually restoring the hole, which is tight and very deep. With the deposition of these sterile materials, already as a paste, the materials inside will be covered, isolated and compacted. It is estimated that once the exploitation is completed, it could be at a height of between 8 and 16 meters above sea level. The filling and the sheet of water are now authorized up to 20.
“The excess water will then be drained and encapsulated, in such a way that the sheet of water that is generated in the future can be isolated, in a context in which after acting on the Northwest dump, the entry of susceptible contact water will be deactivated. to contaminate”. The lake will be generated in this way.
With regard to the Corta de los Frailes –now flooded, although it will have to be emptied to begin underground extraction in a process that could last almost two years–, once the residual exploitation of the crown pillar (the current soil) has concluded, The bottom will be sealed and the slope areas likely to continue generating contact water will be isolated. With the revegetation of slopes and berms, “the final use of the environment occupied by the Los Frailes mine could be for leisure within the framework of a recreational use of a restored mining environment as a natural space.”
