• In Toulouse, the excavation of future tunnels and stations on the line will generate 2.8 million cubic meters of excavated material.

  • Forced by law, Tisséo is looking for ideas to best evacuate and enhance these mountains of earth.

  • Agricultural tracks or quarry backfilling are classic but engineers hope to blow away more innovative ones.

The third line of the Toulouse metro, announced for the end of 2028, will be non-standard: 27 kilometers long, as much as the first two combined, and with a wider tunnel, it will generate, according to Tisséo Engineering calculations, some “2, 8 million cubic meters of cuttings ”as the five tunnel boring machines advance. So of course, the giant moles will not land before 2024. But rather than finding themselves at the foot of a mountain when the time comes, the delegated contracting authority has decided to anticipate and explore the avenues for storing and then to dispose of these hundreds of thousands of tonnes of “molasses, rather good quality soil”.

Tisséo Ingénierie therefore officially launched a call for expressions of interest (AMI) in August inviting innovative companies to offer solutions for the recovery of this bulky site waste. The idea is more to shake the jar of ideas. Because its proposals will not be directly the subject of any public contract. "We will use it to draft the specifications for the calls for tenders that will be launched at the end of 2022 on the structural work of the site", explains Jean Michel Lattes, president of Tisséo Collectivités, convinced that "small structures sometimes have much more imaginative capacity than large groups ”. Thus the probable behemoths wishing to dig the Toulouse metro will be challenged and, perhaps, decided upon, on their proposals concerning the recycling of rubble.

Careers or fields to be filled, or new materials

Especially since the question of excavation is not just a question of posting.

Since the excavation of line A, thirty years ago, the law has changed at the same time as attitudes.

"The Environmental Code obliges us to be attentive to the management of these embankments", specifies Jean-Michel Lattes.

In particular, it sets the objective of recovering 70% of waste from the public works sector.

There are obvious tracks for this, already activated for previous metro lines: "Quarry backfilling or the agricultural sector with fields that need to be covered", lists the elected official.

More original, and pending the results of the AMI, it mentions a "use for the manufacture of construction materials".

Let's be crazy, maybe a candidate will have the idea of ​​creating a wicket with a few wheelbarrows of molasses for Toulouse people who garden.

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Figures

Metro line 3 will link Colomiers to Labège via Matabiau station.

It will include 21 stations including 17 underground for an estimated capacity of 200,000 travelers per day.

It must cost 2.6 billion euros.

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