Mina Mirador shows the state of its tailings dams and denies a possible environmental disaster

Barely eight kilometers separate the Mirador mining concession, located in the province of Zamora Chinchipe and managed by the Chinese company Ecuacorriente, from the northern border with Peru. In this remote sector, with high rainfall and lush vegetation, a copper mining camp, a mine pit, two tailings dams and a plant were built, occupying at least 1,400 hectares, out of a total of 6,600 hectares of land.

The Mirador mine opened its doors this Thursday and Friday to the media to show the condition of the two tailings dams that exist in its concession: Quimi (North) and Tundayme (South). The first is already in the process of technical closure, and the second has a useful life of several years and is predicted to be one of the highest in the world.

The structure and management of both tailings ponds were in the public spotlight after environmental and human rights organizations presented a study that showed – according to the agency EFE— that there would be a possible “risk of collapsing and bursting the tailings dams of the Mirador copper mine, the largest in Ecuador.” If this were to happen, it would be an environmental disaster comparable to what happened in Brumadinho (Brazil) in 2019. These groups spoke of a wave of toxic materials that would destroy everything in its path for several kilometers, including several indigenous communities.

According to the study, the risks in these tailings dams are related to the fact that they are located in an area with high rainfall, close proximity to surface water, high dam height and large amounts of tailings.

However, Mirador technicians categorically rule out the possibility of a disaster similar to the one in Brazil. César Vásquez, manager of Mirador’s tailings management department, explains that the Tundayme tailings dam has a “downstream construction methodology, and the material used to build the dams is sterile rock dust from the mine.” This is the exact opposite of what happened in Brazil, where the method was upstream and the dam material was sand from the tailings itself.

At Mirador, the tailings dump – a working system that enables waste and water management – receives metallurgical waste obtained after rock crushing and ore extraction. They arrive through a lane system. From the viewpoint you can see two tailings dams. The first is Quimi, with 11 million cubic meters of capacity and built according to the central axis model, which, according to Andrés Vásquez Ponce, deputy manager of the same department, already closed in August 2021 and entered the process two weeks ago. closing technician. That’s because it was only designed to receive test waste when it began operations in 2019. It now holds just under a million cubic meters. “The evidence shows that it’s dry,” he assures, explaining that although looking at the lagoon you might think it’s deep, it’s only about 60 cm.

A little further south, you can also see the Tundayme dam, with a capacity of 370 m³, which will reach a height of 260 meters. It is a mega-project built in the valley through which the Tundayme River used to flow. Here you can currently see the lagoon, as well as the construction of the first dam and the platforms on which the next dams will continue to be built, at increasingly higher altitudes, using the downstream method. The river has been diverted from its bed (about 500 m) to prevent it from coming into contact with polluting material and now passes through a tunnel under the mountain. According to the technicians, at Tundayme, a layer of clay, a layer of geotextile, then a geomembrane and finally another geotextile were used as a coating to prevent seepage.

In addition, there are works on drainage (five wells) and water transport to the treatment basin, so that the water will then be recirculated back to the processing plant. There is a geodetic control, a laser scanner and a surveyor to monitor the events at this place. 700 surveillance cameras have been installed in the mine, and 45 of them are directed towards tailings dams.

Referring to the case of Tundayma, Vásquez Ponce assures: “We know how important structures are and we want to give them more stability, more robustness.” In this sense, he assures that international standards have been implemented for the construction of both tailings ponds. 55 engineering and service contracts were concluded. The price of this process was 15 million dollars. This included 7,000 meters of geotechnical drilling, 8,000 laboratory tests in soil mechanics, as well as 20 km of geophysical surveys.

It also indicates that three seismic surveys were conducted and that it was determined that all of Ecuador is in the seismic zone, but it must be emphasized that Tundayme and the entire eastern region are in the area of ​​moderate seismic activity; the greatest risk is on the coast.

Among the participating companies are KCB, as the main consultant, and for the designs and studies of the Peruvian Andes, Letis from the USA and several national suppliers.

The Tundayme tailings dam has the potential to rise about 60 meters above the current limit of 260 meters, when the Mirador Norte stage becomes operational.