To build the Grand Paris Express metro, 47 million tonnes of rubble to be evacuated or recycled

"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 (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 tonnes 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 Mr. 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. "The trucks are also weighed at the start on arrival", indicates Thomas Gaudron, responsible for the management of the cuttings and the valuation.

The company has pledged to reach "a recovery target of 70%", a threshold which has not yet been reached at this stage.

Avoid fraud

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-Damartin.

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 Mr. Cathelain.

In addition, to deal with possible fraud such as exists in the waste sector, 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.