Third metro line in Toulouse: a polluting construction site?
As part of the public environmental inquiry into the 3rd metro line in Toulouse, the political party Place Publique is concerned about the techniques for digging the tunnels that will be chosen because one of them is polluting.
Unaccustomed to intervening in local public debate, the “citizen” political movement created by Raphaël Glucksmann in 2018, Place Publique, which includes elected members of the departmental council, is stepping up to the plate on the 3rd metro line, as part of the environmental public inquiry. “It is not a question of calling into question a project that we support, specifies Hugo Sajhau, but of being vigilant. Place Publique says it has been alerted by sympathizers to possible pollution of the earth that will be extracted during the construction site.
The digging of the tunnels on the 22 km underground of a 27 km route, the stations and the evacuation shafts will generate an enormous quantity of rubble supplied to 2.6 million m3 in total by Tisséo Collectivités, project owner of the 3rd line. For the tunnels alone, this represents 1.5 million m3, i.e., indicates Place Publique, “the equivalent of a 42-storey building occupying the entire space of rue Alsace-Lorraine from place Jeanne-D’ Arch to Place Esquirol. It is in these last rubble that the political formation is interested, which, in fact on the subject, points to the risk of a polluting technique, that known as “earth pressure” because the tunnel boring machines then use chemicals. Conversely, it recommends the “mud pressure” technique, which is “without adjuvant”. “The project does not clearly say that it imposes this (last) technique, which seems essential to us”, regrets the formation.
Round trips of trucks
In the process, Place Publique looks at the thousands of round trips of trucks that will be necessary to evacuate the earth. And it suggests the use of river shuttles and trains to limit road traffic which promises to be substantial. It also opposes the use of gravel pits filled with water to store soil. And finally, the political formation wonders, once the metro is integrated, about the future of the infiltration water which will have to be permanently evacuated.
Asked yesterday, the president of Tisséo Collectivités, Jean-Michel Lattes, made it known that he would not speak during the public inquiry. But the file submitted by the project owner contains elements of response that the contribution of Place Publique mentioned. On the choice of technology for the five future tunnel boring machines, Tisséo indicates that it is up to the companies that will be selected. And specify that “these adjuvants do not however present any environmental risk (because) they are biodegradable. »
For the transport of the cuttings, Tisséo asked the SNCF and, for reasons of saturation of the tracks, the contracting authority affirms that it is impossible to use the sites of Colomiers station, La Vache, Matabiau and Montaudran station. But a study continues for Raynal. Similarly, in connection with VNF, the use of the Canal du Midi was deemed incompatible. That of the lateral channel remains to be specified. For quarries, Tisséo says he wants to favor the use of dry sites but without excluding others. On each of the four points raised, Place Publique’s contribution takes up the recommendations of the Regional Environmental Authority Mission.
Tisséo will have to position itself more precisely in the context of future discussions with the investigating commissioners. Spoil management is one of the key points of the environmental investigation. A subject on which the regulations have changed a lot since the construction of lines A and B.
The environmental investigation until Friday
Started on December 15, the public inquiry into the environmental aspect of the third metro line will continue until Friday January 28 inclusive. On the website www.registre-numerique.fr/enquete-metro-toulouse, you can read the investigation file and also read the contributions already submitted by individuals or associations. If the opportunity of the project is regularly mentioned in these speeches, the survey does not aim to question this point: the third metro line was declared of public utility on February 7, 2020. This public survey aims to measure the environmental impact of the construction of this 27 km line to see if it has been limited as much as possible and if compensation measures have been taken. For opponents of the project, this remains an opportunity to put the 3rd line back on the hot seat.