“Follow the chains of the path, don't take off your ventilator mask and watch where you step, there are stones and there may be pieces of junk.
"
The instructions given to visitors by the teams of the Séché Environnement company, specializing in the treatment of hazardous waste, are those followed on a daily basis by the 40 people brought into the enormous confinement tents the size of "two and a half football pitches. », Compares Rémi Muth, the technical director.
Welcome to the location of the future Olympic aquatic center, in Saint-Denis.
Opposite the Stade de France, on the twelve hectares of former gas production grounds, it is very difficult to imagine that records will fall and that the most breathtaking choreographies will follow in 2024, in the heart of the ultramodern sports arena. built for the Olympics.
A site in the site
The artistic swimming, water polo and diving events are still a long way off: for the time being, it is wearing disposable wetsuits that the workers enter waterproof tents of 26,000 m2, secured by 90 stakes of 17 meters.
Under a covered metal frame, it is a site in the site that we discover then.
Saint-Denis, Thursday March 18.
Land decontamination is carried out under 26,000 m2 containment tents, from which the polluted air is extracted and filtered.
The teams work under assisted ventilation masks.
LP / CG
At a depth of ten meters, an excavator lifts contaminated soil to be evacuated.
Hydrocarbons, solvents, heavy metals are the main sources of pollution identified.
To control toxic fumes, the most contaminated areas that are between three and 14 meters deep are handled under containment tents.
The stale air is extracted and filtered there, the ventilation turns in a deafening din.
Inside, the personnel wear, in addition to their masks, an individual gas detector which continuously measures hydrocyanic acid, hydrogen sulphide, carbon monoxide and volatile organic compounds in the atmosphere.
The former site of a large gas plant
The twelve hectares to be cleaned up housed monumental gasometers, the highest of which reached 65 meters.
Created in 1882, the gas plant covered the needs of Paris in terms of lighting and heating.
The last screened tank disappeared from the Saint-Denis landscape in 1981. The research and development activities of Engie, a group heir to this history, moved from the site at the end of 2019 to join Stains.
The gasometers of Saint-Denis, in the years 1960-1970.
Saint-Denis municipal archives
The reconversion piloted by the Greater Paris Metropolis will make it possible to develop a new district around the aquatic center.
Arrived in October 2020, Séché Environnement teams have a total of fourteen months to excavate 165,000 m 3 of soil (i.e. the volume of 60 50-meter swimming pools) and remove 30,000 m 3 of polluted soil by truck or boat.
“It's a very tight schedule,” says Rémi Muth.
We are on a yield of 800 m 3 excavated per day.
"
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Polluted groundwater, which looks like a whitish liquid, is also pumped out.
However, they are filtered and reprocessed on site.
The whitish liquid is polluted water, pumped 14 meters deep, before its reprocessing and filtration.
LP / CG
The site must be completed at the end of the year.
“This is an exceptional-scale pollution control operation,” concludes Sébastien Amiot, from Séché Environnement.
Probably one of the most important currently in Seine-Saint-Denis.
The cost of decontamination work, excluding project management, amounts to 21 million euros.