Antofagasta pioneers forestation of Quillayes tailings facility
20 May 2022
Planting 300 hectares of native and feral plants on the tailings facility will control dust emissions and help blend it into the natural environment
Antofagasta's Los Pelambres mine is planting bushes and trees on 300 hectares of its partially closed Los Quillayes tailings storage facility (TSF) in a pioneering initiative that aims to address the facility's environmental impact over the long-term.
Eleven species have been selected for planting based on their low water needs and resistance to extreme climatic conditions. They are all either native or already firmly established in north-central Chile's Coquimbo Region, where Los Pelambres is located.
"These species will form a vegetation cover that will control dust emissions, prevent soil erosion and contribute to the creation of an ecosystem that will mimic the surrounding areas," says Francisco Riestra, superintendent of Regulatory Risk Management at Los Pelambres.
The initiative responds to concerns about dust from the TSF raised by the Cuncumén and Batuco communities located further down the valley and has been approved by Chile's national geological service Sernageomin.
The phytostabilisation project (a project that uses plants to restore the environment) began in 2013 as a pilot on 30 hectares of the TSF's surface. It was officially launched in 2019, when another 30 hectares were planted and once the current programme to plant 48,000 plants on a further 60 hectares is completed in mid-2022, a total of 120 hectares will have been planted.
Tests were done in 2021 on plants that could adapt to the TSF retaining wall's steeper gradient and different sun exposure where planting is expected to start next year, says Francisco González, the head of Los Pelambres' Vegetation Project.
The project ultimately aims to cover 300 hectares of the TSF with vegetation, of which 200 hectares will be on the facility's surface and 100 hectares on its wall. "The goal is to complete planting of the TSF surface and wall by the end of 2024," he says.
Quillayes was the original TSF at Los Pelambres and a small section of 30 hectares will continue to be available as backup to the main El Mauro TSF in case of operational needs or emergencies.
Preserving local species
The project involves improving the quality of granular material taken from nearby barren hillsides with fertilisers and hydrogel (a compound that retains water) to create a topsoil of approximately 30 centimetres on the TSF's surface.
In parallel, local seeds are collected and germinated in nurseries until the seedlings are ready to be planted in the prepared soil. Plants are spaced in a way that reflects and blends into the natural environment with an average density of 800 plants per hectare.
"The seeds and plants have a local character and we are strengthening and preserving the germplasm of local species," explains González.
Careful maintenance of the newly-planted bushes and saplings is required to protect the plants against pests and, using careful irrigation, to ensure efficient water-use. The most mature trees have an average height of about two metres and are providing fruit and seeds, says González.
Initial intensive irrigation of this older growth was 20 litres per month (l/m) per plant has now been reduced to 2.5 l/m per plant. "We are now testing whether these plants can survive naturally without any irrigation," he says.
This experience has allowed Los Pelambres to begin irrigating its new plantations with 5 l/m of water per plant with a view to reducing to 2.5 l/m when plants become established and finally to stop watering them at all.
Creating local jobs
In line with Los Pelambres' commitment to hire locally, more than 70% of the people working on the project come from the Choapa Province where the mine is located.
The local Sustainable Development Cooperative of Valle Alto in the Salamanca municipal district produces around a quarter of the plants, while the rest are provided by a national contractor which recruits over 90% of its workforce locally. Another contractor helps to provide the granular material for the topsoil.
"This is a project that uses plant species from the area and mainly employs local people," says Riestra. "It is valued by local communities because they see that it will benefit future generations."
The project is in addition to Los Pelambres' broader forestation programme to compensate for vegetation loss caused by the operation, which is a condition of the mine's Resolution of Environmental Approval (RCA). As part of its commitment, Los Pelambres has so far reforested almost 1,000 hectares out of a total of 1,500 hectares, according to Riestra.
"The Quillayes Phytostabilization Project is helping to establish mine closure techniques that are more in tune with the environment," says René Aguilar, Antofagasta's Vice President of Sustainability and Corporate Affairs. "These innovative techniques reduce the dispersion of particulate matter, improve the containment of tailings and manage rainfall better as it is absorbed by the plants. It's a sustainable solution to TSF management and mine closures," Aguilar added.
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