The expansion of the largest industrial dump in Saguenay is causing an outcry. Millions of tons of red, corrosive mud will replace the Panoramic woodland, a small forest located in the center of the city, within a few years. Rio Tinto plans to convert this nature park into a tailings park to supply the region’s aluminum smelters. But the soil at the coveted site contains clay, and landslides are known to occur most frequently in clay soils, it has been learned. THE Duty. The multinational wants to be reassuring, but nearby citizens fear the worst.
A landslide in 2021 swept away the backyard of Pierre-Paul Legendre’s neighbor. “It demonstrates the fragility of the soil,” observes this Saguenéan, who lives in the heights of the Panoramique district, in the Chicoutimi district. The owners had cut down the trees on the sloping ground, then the ground collapsed shortly after, suddenly, on the home below, explains the retiree.
Worried, he points to the wooded hill visible from his living room. Thousands of trees will soon disappear from this mound because Rio Tinto plans to open its next bauxite residue park there (the main ore from which aluminum is made).
This industrial waste has been accumulating for nearly a century in Saguenay: nearly 40 million tons of this mixture already lie in a landfill in the center of the city. This red mud lake will reach its maximum capacity by 2030, and the mining company has decided to use the Panoramique woodland to dump its next 15 million cubic meters of waste (or more than 37 million tonnes, according to calculations of Duty).
Map showing the current red mud dump and the proposed expansion site (approximate outline)
Citizen pressures
The instability of the soil on the selected site causes great anxiety among certain residents, some of whom live 500 meters from the future slag heap. Three technical documents, including an inventory of wetland losses carried out by the firm WSP, confirm the presence of clay in the soil of the planned dump. This precise data was obtained thanks to the efforts of the Citizens’ Committee for a Sustainable Vaudreuil (CVD), of which Pierre-Paul Legendre is a member.
This clay is worrying because it is a determining risk factor regarding landslides. And such disasters occur regularly in Saguenay. The memory of the tragedy of Saint-Jean-Vianney is still vivid in the region: the village once established just opposite the Panoramique woodland, on the other side of the river, collapsed in 1971. Almost the The entire municipality and dozens of lives were lost in the disaster.
Rio Tinto is aware of this presence of clay. “We will not deposit residue on the clay, as this can lead to sliding. We will go to rock,” declared a representative of the company, according to the minutes of a citizen consultation. Bypassing these sensitive areas will reduce the initial plan for the Panoramique woodland residue park by 33%, according to this same document.
The company alleged in its initial request for an environmental authorization certificate that the Panoramique woodland site was “outside the landslide risk zone”. Questioned by THE Duty on the evolution of the file, a spokesperson for Rio Tinto responded by email that “several geotechnical analyzes were carried out with specialists to characterize the soil in order to obtain a much more precise definition of the constitution of the soil of the planned site “. The company did not want to show us these studies.
Despite this, “I understand citizens’ concerns,” says François Courchesne, expert in soil science at the University of Montreal. Four factors cause landslides: slope, the presence of clay, the presence of water and shocks in the ground.
The Panoramique woodland combines these four risk factors. Slopes in the sector can reach 15%, according to Rio Tinto analyses.
The jolts of a “rolling truck” can cause the shock necessary for a slide, Professor Courchesne also assures in an interview. This specialist in clay and ground movements cannot rule on the specific case of Saguenay due to a lack of detailed soil maps, but he remains of the opinion that “it is not the best idea” to install such a dump. on a hill. “The plan to put a mining deposit in an upper part of a city is as intelligent as installing a septic tank high up,” says the professor. Clay, not clay, gravity does its work. »
The choice of the Panoramique woodland remains for the mining company “the option that would make the most sense from an environmental, social, technical and economic point of view,” according to its spokesperson.
“We don’t want [l’usine de transformation de bauxite] farm. We don’t want to lose 1,000 jobs. We just want it to be [un projet] sustainable,” says Jean-Yves Langevin, another citizen member of the CVD not very reassured by the partial information from Rio Tinto. ” It’s not for me. It’s for my region. »
Approximately 6,200 homes are located near the planned mine tailings park.
A second and third site
A second potential site has been identified for the future red mud lake. This place called “Laterrière” is the property of the aluminum giant, and around ten thousand tonnes of bauxite residue has already been lying dormant there for decades.
But the invoice weighs in the decision, according to what we can read in the request for certification of authorization of the industrial project. Rehabilitating this abandoned site would cost $400 million, compared to $200 million to transform the Panoramique woodland, according to an estimate from Rio Tinto dated 2017. Choosing the Laterrière dump “involves the pumping of residue […] over a distance of more than 13 km, which greatly reduces its technical feasibility,” it is always specified in the documents produced by the mining company.
Rio Tinto also prioritizes the Panoramique woodland because there is “a significantly higher ecological value at the Laterrière site”. Despite everything, around ten wetlands were identified in the Panoramique woodland by teams commissioned by Rio Tinto.
The CVD suggested a third site to the mining engineers. Far from any habitation, the place is located “between Chicoutimi and Bagotville, near the railway line”. The CVD does not want to reveal its exact location so as not to lead to speculation. The Rio Tinto spokesperson told the Duty that this space was being “considered,” but she doesn’t expect a decision to be made until at least next year.
The City of Saguenay has not issued a construction permit for the conversion of the Panoramique woodland; the final decision therefore still remains pending.
This report is supported by the Local Journalism Initiative, funded by the Government of Canada.