• For years, when the level of the canal is low, the Voltaire and Rousseau quays in Frontignan have been surrounded by the scent of hydrogen sulphide (H2S).

  • This is the fault of the groundwater from the old Mobil refinery, which has concentrations of H2S, due to the degradation of hydrocarbons in the subsoil.

  • Work is currently being carried out to eliminate these odors.

It (almost) no longer smells like rotten eggs, on the banks of the Rhône canal, in Frontignan (Hérault). It may be a detail for you, but for the locals, it is a small revolution. For years, when the level of the canal is low, the Voltaire and Jean-Jacques Rousseau quays have been surrounded by the scent of hydrogen sulphide (H2S), a toxic gas, and particularly smelly.

According to the force of the wind, or even, no doubt, the temperature, the perception by the inhabitants were not the same.

"It ranged from simple embarrassment, to the urge to vomit," says Céline Laurens, president of the Association of residents of the Rhône canal.

"It was a rotten egg smell, very recurring," adds Francis Herrera, member of France Nature Environment and former secretary of Action Risque Zéro Frontignan (ARZF), who reported these odors to the authorities in 2012. They had by have also been identified by the network of "noses"

(read here),

set up in the Thau basin by Atmo Occitanie, the regional body responsible for monitoring air quality.

Groundwater involved

But "after years of research and various works on the pipes", rejoices the municipality of Frontignan, the origin of these odors has finally been identified: it is the fault of groundwater, coming from the old refinery. Mobil, not far from there, which "have concentrations of H2S, due to the degradation of hydrocarbons in the subsoil", told residents of the affected neighborhoods Exxon Mobil, which owns the former industrial site. “They flow from the north of the site towards this section of the canal,” continues the oil group. When the level of the canal is low, the water inlets from the groundwater is very close to the surface of the water, the H2S dissolved in the water becomes oxygenated and odors are felt. When the channel level is high,the water inlets are submerged and there is no smell. "

To the delight of the inhabitants, who are finally able to drink an aperitif on the terrace without moving their noses, major work is currently being carried out to remedy this: divers are currently mapping the water inflows that pose a problem. , and redirect them, via pipes, to the bottom of the Rhône canal. If this redirection of water has considerably reduced the smell of hydrogen sulphide in the district, "we still felt some odors at the level of the quai Rousseau", continues Céline Laurens. But in the canal, work is continuing.

From 2022, the decontamination work of the old refinery, which is now closed, will also make it possible to further reduce the H2S concentrations.

Exxon Mobil has also planned, confides the group to

20 Minutes

, to set up its own network of "noses", which will be responsible for flushing out the smells that this rehabilitation of the place could bring to light.

Residents who wish are invited to participate.

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Planet

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  • Works

  • Water

  • Languedoc-Roussillon

  • Oil

  • Refinery

  • Montpellier

  • Sète