18 May 2021
An exceptional decontamination operation in Saint-Denis’ Plaine Saulnier development zone
Since October 2020, Séché Environnement has been tackling a sizeable challenge in the Plaine Saulnier development zone of Saint-Denis, north of Paris, cleaning up the future site for a new watersports complex. The immense worksite is entirely contained within vast tents to protect local residents.
One of the largest ongoing decontamination projects in France
The activity on site is impressive to witness, with some 40 operators hard at work each day on a 26,000m2 site covered by vast white tenting. For the past six months, the challenge that has been on everyone’s mind has been excavating nearly 165,000m3 of earth, including 30,000m3 of polluted soil, to prepare the site for upcoming developments.
To clean up this vast space spanning nearly 12 hectares, the Métropole du Grand Paris (Greater Paris) has hired a consortium made up of:
- Séché Environnement, through its specialist site decontamination and rehabilitation business;
- Antea Group, the prime contractor;
- Keller, the firm responsible for the tent foundations;
- Charier, the firm responsible for the earthworks.
14 months of decontamination for 150 years of gas industry activities
The site previously housed three huge gas holders, and the soil continues to bear the marks of 150 years of gas industry activities: hydrocarbons, solvents, metals, etc. When the excavated soil comes into contact with the air, some of the hydrocarbons it contains evaporate. To avoid any atmospheric pollution during the clean-up work, the operations are being conducted inside huge tents, erected on 90 stakes planted to a depth of 17m. The air inside is constantly treated and renewed, while the operators work wearing gas masks.
The groundwater, meanwhile, is pumped and treated on site, before being discharged into the rainwater drainage system.
Trucks and diggers are engaged in a meticulous and perfectly choreographed ballet, clearing, filling, and optimizing the available area. The polluted soil that cannot be reused on site is transported to specialized processing sites by land or water.
“We are particularly proud of this flagship project. Its scale and specific challenges call for extremely specialist expertise. Everyone is working flat-out to get the utmost value out of this industrial land, restore the environment and protect the health of local residents.”
Rémi Muth, Technical Director, Séché Environnement
The teams have just 14 months to complete the project, and they face no shortage of challenges. Not only is the site close to the Stade de France and the intersection of two freeways and several rail links, but the team also have to reckon with an underground metro line. The geotechnical and topographic constraints do not make things any easier.
The aims: exemplary environmental and safety performance
Whatever the difficulties faced and the deadlines to be met, safety remains the priority. The containment of the works within tents protects the local population. The Séché Environnement teams perform daily monitoring of air quality, soil quality, sound levels and water before and after treatment.
The staff working on site wear highly specific Personal Protective Equipment (PPE): gas masks with filters, multigas detectors, full-body suits, gloves, etc. They have changing rooms equipped with a decontamination area by the exit and a series of airlocks enabling them to undress safely. The vehicle cabins are pressurized and equipped with specific filtration systems.
The project is scheduled for completion in December 2021.
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