To build the Grand Paris metro, it is first necessary to excavate 47 million tonnes of rubble, “the equivalent of raising the capital by more than 20 cm”, according to the Société du Grand Paris, which has already evacuated half of it. . “Between 10 and 20% of the rubble in Île-de-France is rubble from the Grand Paris Express,” said Bernard Cathelain, member of the management board of the Société du Grand Paris (SGP), during a site visit open to the press in Saint-Denis, in Seine-Saint-Denis, Wednesday.
The figures are up to this sprawling 200 km public transport project around the capital, which includes four new automatic metro lines, as well as extensions of line 14. The work requires digging up to fifty meters deep. The 24.7 million tons of cuttings already excavated are of different natures (sand, gypsum) representative of the diversity of the basements of the Paris basin, notes the SGP, project owner of the sites. “98% of the land is unpolluted and non-hazardous so can be reused”, insists Bernard Cathelain, referring to the numerous analyzes carried out in the laboratory.
The tiny remaining portion, polluted by human activity (solvents, hydrocarbons), must be kept in dedicated storage facilities, he recalls. Property of the SGP, the cuttings are tracked thanks to a digital tracking system from the trucks to the final destinations. “Trucks are also weighed on departure on arrival,” says Thomas Gaudron, responsible for the management of cuttings and recovery. The company has pledged to achieve “a 70% recovery target”, a threshold which has not yet been reached at this stage.
In fact, the majority of recovered rubble is used as backfill in quarries, brownfield sites undergoing conversion or public spaces to be redeveloped. Transported mainly by trucks but also by train or barges on the Seine, they end their journey in Île-de-France (80%), mainly in Seine-et-Marne which hosts a major site in Villeneuve-sous-Dammartin. This is not without arousing the reprobation of residents, associations or local elected officials, who deplore the nuisances in territories which are not affected by the arrival of the supermetro. Finally, a small part (2.3%) of this waste is reused in eco-construction, via recycled materials. The overall management of all the excavated material requires a budget of around one billion euros, estimates Bernard Cathelain. In addition, to deal with possible fraud such as exists in the waste sector, the SGP announced that it had signed an agreement to “share information” with OCLAESP (central office for the fight against environment and public health), attached to the gendarmerie.
“We have not identified any fraud on the sites of the Grand Paris Express”, however assured Jean-François Monteils, the president of the SGP, praising the quality of the traceability. “Our stuff is solid.” After delays, the new automatic metro lines, numbered 15 to 18, are expected to gradually come into service from 2025. Seine-Saint-Denis today poorly served.
