The fate of the tailings from the Mariana tragedy will be decided in 45 days.

Léo Rodrigues – Correspondent for Agência Brasil

The management plan for the mining tailings spilled after the Mariana (MG) tragedy began to be discussed this Wednesday (25) and should be delivered in 45 days to the Secretariat of Environment and Sustainable Development (Semad) of Minas Gerais. Researchers, consulting firms and representatives of environmental agencies participated in a seminar that started the discussions. The event was organized by the Renova Foundation, created by the mining company Samarco to manage the actions to repair the damage caused by the episode. New meetings will take place in the coming weeks.

The Department of the Environment will need to determine what will be done with all the dispersed mud. There will not be a single solution, and not all the tailings will be removed. Different measures will need to be adopted, taking into account that the affected region is composed of areas with distinct characteristics.

The Mariana tragedy occurred on November 5, 2015, when the collapse of the Fundão Dam, belonging to Samarco, devastated native vegetation and polluted the Rio Doce basin. Nineteen people died and communities were destroyed, including the districts of Bento Rodrigues and Paracatu. The event is considered the country's worst environmental disaster.

An agreement signed between Samarco, its shareholders Vale and BHP Billiton, the federal government, and the governments of Minas Gerais and Espírito Santo established that the entire impacted area must be rehabilitated by the companies. Among the defined obligations is the management of the tailings. Although this agreement has been challenged by the Federal Public Prosecutor's Office (MPF) and... even if it does not yet have legal validity.The signatory parties are fulfilling the agreement.

According to the Renova Foundation, 39 million cubic meters of tailings escaped the boundaries of the Samarco mining complex. Of these, 20 million are deposited in the stretch that extends to the Candonga Power Plant, in Santa Cruz do Escalvado (MG). As a result of the agreement, the Renova Foundation filed an official letter with environmental agencies committing to remove 11 million cubic meters of mud.

In the municipality of Barra Longa, 170 cubic meters were collected. In addition, dredging is underway at the Candonga Hydroelectric Plant. Approximately 500 cubic meters have already been removed, and the goal is to reach 10 million. In the coming months, work will also begin in the Bento Rodrigues region. The objective is to remove approximately 1 million cubic meters from the site. There is no estimated completion date for all the work, which is expected to take several years.

Given that a commitment has already been made to remove 11 million cubic meters of tailings, the management plan to be drawn up in the next 45 days should indicate what to do with the remaining 9 million cubic meters deposited between the Fundão Dam and the Candonga Power Plant, as well as the rest that flowed down the Rio Doce to the coast of Espírito Santo.

Thiago Marchese, manager of Socio-environmental Programs at the Renova Foundation, highlighted the importance of inviting people of recognized expertise, with multiple perspectives, to contribute to the plan's development. "Disagreement is indeed happening, and it's very healthy. If the goal wasn't to seek diverse opinions, the seminar wouldn't make sense. We need to exhaust all possibilities and discuss all points of view."

For Zuleika Torquetti, Superintendent of Environmental Management at Semad, the seminar is also a way to listen to society, represented there by the scientific community, specialists, and consultants. She also sees benefits for the process of processing the management plan. "Often, environmental agencies receive documents and studies to analyze that arrive with unsatisfactory information. This generates rework both for those who submitted them and for the analysts who end up having to do reassessments. This opportunity for prior discussion already reduces the possibility of gaps in the document that will be presented," she says.

Zuleika emphasizes that Semad's participation in the process does not exempt it from conducting a detailed analysis of the plan, which will be presented in 45 days. "Environmental agencies follow guidelines. The analysis of the final document will take into account legal requirements, and some additional demands may be made."

Peculiarities

The main challenge in developing the plan is taking into account the specific characteristics of the different affected areas. In this sense, there seems to be a consensus among experts that the tailings should not be removed entirely. Part of it would be managed in another way.

Researcher Luiz Eduardo Dias, an agronomist at the Federal University of Viçosa (UFV), believes that mobilizing specialists from different areas is the right path and that it is possible to arrive at a plan that can even serve as an international model for environmental recovery. "We are dealing with a new situation, so great care must be taken, because between the Fundão Dam and the Candonga Power Plant there is enormous geomorphological, spatial, and environmental diversity. Common measures cannot be applied to areas with distinct characteristics," he states.

According to the agricultural engineer, the decision to remove or not remove the tailings should take several factors into account. "What type of soil existed beneath the site where the deposition occurred? What is the thickness of the tailings above the original soil? These are questions to be considered. Depending on the type of land use, there is often no need for removal." He adds that there is no chemical impediment to keeping the tailings in place, since they are an inert material, meaning they do not interact with the environment and have low toxicity.

Luiz Eduardo Dias also points out that, in some places, it is preferable to stabilize the mud and allow it to receive organic matter and transform into new soil over the years. The planting of grasses and legumes, which has already been done in certain areas, has initiated this process. He also makes references to the peculiarities of small farmers' lands.

"The plan still needs to reconcile what, ideally, would be best from a technical and environmental standpoint with social issues. In other words, it needs to be attentive to what the affected population wants. For example, what socioeconomic options do small farmers whose lands were affected have to return to generating income?"

Agriculture

The impact of tailings removal on arable land is one of the biggest concerns for soil specialist Carlos Ernesto Schaefer, a researcher in pedology and morphology at UFV. He advocates using common sense to find simpler, more economically feasible solutions with faster practical results that primarily serve the interests of affected populations, such as farmers and riverside communities.

"The removal of tailings in arable areas near rivers generates problems that multiply the environmental impact. When the..." tsunami "With the mud, the river plain was decapitated, that is, it lost an enormous volume of material. And in place of that material, the tailings were deposited. When we observe the riverbanks, we even see that this tailings is not pure. It is a mixture with the soil that already existed in the area. Therefore, the old material is no longer there, and if you remove the tailings, what will remain will be practically at the river level. In the first rainy summer when the river level fluctuates, it will flood all these areas. It is possible to imagine even health problems, because lagoons will form that could facilitate the proliferation of mosquitoes."

Another issue raised by the researcher concerns the fate of the sludge. "Where are we going to put all this tailings? On top of hills? It will generate a huge environmental liability in an area that wasn't impacted. For what purpose? I don't understand that Samarco's obligation is to remove all the tailings. Their obligation is to ensure that all areas are restored to their environmental, human, and socioeconomic integrity. If we can achieve this without megalomaniacal solutions, all the better."

The proposal presented by Carlos Ernesto Schaefer is to cover the tailings with soil from the surrounding area, allowing farmers to immediately resume production in these areas adjacent to the Carmo River, the Gualaxo River, and the Doce River. According to him, these areas are generally the best available landowners have on their property.

"The problem with the tailings isn't chemical. They're inert. The problem is physical. Therefore, we just need to leave them down there, isolated from the roots of the plants. Farmers need to get back to their homes, orchards, subsistence farms, pasture for the cows, vegetable gardens, and crops. And this soil covering technique is already happening successfully in some areas, through the initiative of a few landowners," adds the researcher.

Carlos Ernesto Schaefer points out that his considerations apply to rural areas. In urban areas and those adjacent to cities and towns, the removal of tailings should occur by restoring characteristics as close as possible to the original state, since people in these locations do not depend on this soil for their livelihood.