Produced during the First World War in the former national powder factory of Toulouse, in Braqueville near the current Oncopole, since then, under water in four ballast tanks, 5,000 tonnes of nitrocellulose, a propellant powder then used in the armament, can still wait. Since the 2000s, before, but especially after the explosion of AZF in 2001, the environmentalists of Friends of the Earth, then the successive mayors of the Pink City, have been increasing the number of alerts to ask for the depollution of these artificial lakes.

The State, owner via the Ministry of Defense, then fenced off the site and organized the control of the water level. He also undertook, from those years, to eliminate Toulouse of these deposits of powder B, neutralized under water but flammable in the open air.

Twenty years later, when the first ballast tank will be overflown by the cable car and at 800 meters, the buildings of the Oncopole have grown, and despite many feasibility studies already carried out, pollution control has still not started. .

120,000 tonnes to be treated

On the eve of the 2017 presidential election, Prime Minister Bernard Cazeneuve, in Toulouse, exhumed the file and made the promise, declared ineffective, “to start work by 2022”. After a new request from Mayor Jean-Luc Moudenc, Jean Castex, the Prime Minister, asked in November 2020 for the establishment of a monitoring committee.

This new chapter was opened on January 25, 2021 with a meeting taken over by the prefect Etienne Guyot in the presence of the State services, the Ministry of Defense and François Chollet, vice-president of Toulouse Métropole in charge of ecology. . If the State has reiterated its commitment, it has also announced the launch of new preparatory studies for two years. End of 2022: here is the new objective ticked on the agenda.

And yet, on July 1, 2013, during the meeting of the information body which took place among the residents, the Permanent Secretariat for the Prevention of Industrial Pollution, almost all of the studies had been unveiled. And in 2014, the choice of a depollution method had to be stopped.

Several hypotheses were on the table: biodegradation, incineration on site or after transport to another site. Today, this choice, subject to ongoing studies, does not always seem to be made. It also depends on the environmental constraints of a Natura 2000 classified site that has become, over the years, a nature reserve.

“It is going in the right direction”, reacts however François Chollet who promises to remain “vigilant” and wishes information of the population. Even acquired, the depollution will involve a long project: 5,000 tons of powder have to be treated but 120,000 with the debris of the crates and the silt, according to an estimate. The duration and cost of the operation thus remain to be determined.