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hundreds of dead fish in the Durance, after a hydraulic dam was emptied

The Hautes-Alpes fishing federation is indignant against an emptying of the Pont Baldy dam on April 1st. The opening of the valves would have poured mud into the waters of the Cerveyrette and the Durance, thus asphyxiating many wild fish. The fishermen denounce an ecological disaster.

It is a mythical river for trout fishermen. The Durance, which crosses Provence to the Rhône, has just suffered a “real ecological disaster”, according to the Hautes Alpes Fishing Federation.

Indeed, since the beginning of April, significant fish mortality has been observed. Thousands of Mediterranean Fario trout, an entirely wild species, died, asphyxiated in the bed of the Durance.

In question, the emptying of the hydraulic power station of Pont Baldy, located east of Briançon (Hautes-Alpes). The maneuver was carried out on April 1, and this for seven days by the company Energie Développement Services du Briançonnais (EDSB). It is the concessionaire of the hydraulic dam, producer of electricity.

For the plant, it was a question of evacuating sludge and sediment accumulated in the lake for 11 years. This decennial emptying would be a necessity for the safety of the work, but it has been denounced by the fishermen for several months.

The Federation (…) has always expressed its total disagreement with an emptying from April 1, a period when this year, the flow of the Durance is very low”explains the federation.

David Doucende, project manager for the federation is also a hydrobiologist engineer. For months, he has been warning about the dangers of this maneuver: “in view of the low flows of the Durance, we knew that it was going to cause this disaster”.

The fishermen wanted the operation to take place in May, when the melting snow increases the flow of the river. “This would have made it possible to dilute the quantities of Suspended Matter (SS)”explains David Doucende.

The sludge first poured into the watercourse of the Cerveyrette. The latter flows into the Durance, near the town of Briançon.

And for several days, the fishermen can only note the disaster: carcasses of fish by the hundreds, along the Durance, to Argentière-la-Bessée, float in a marshy river. David Doucende believes that the consequences can be felt as far as Embrun.

There are the fish that we see, and those that we do not see. The reproduction of the year, these are hundreds of thousands of fry. We know they are lost“, laments the engineer.

This emptying of the Pont Baldy dam is strictly supervised by the authorities.

Reached by telephone, the Hautes-Alpes prefecture confirms that the operation was indeed authorized on April 1, given the dealer’s commitments.

Given the low flow of the Durance and the risks to the ecosystem, the State services asked the concession holder for additional information before the operation could start. In particular, it was a question of adapting, or even stopping, the emptying maneuvers in the event of exceeding the physico-chemical thresholds (materials in suspension)”, she specifies.

Also contacted, EDSB management explains in a press release that this ten-year oil change is “necessary to carry out major works, validated by the granting authority. These are intended to guarantee the safety of the structure and third parties and cannot be done without ensuring that the reservoir is emptied to access organs that are usually submerged.”

The dealer adds that “Ihe emptying was subject to continuous monitoring, 24 hours a day, of the physico-chemical parameters in the environment (rate of suspended matter, level of oxygen, ammonia, ammonium, etc.). A team of operators was mobilized and the valve operations were adapted according to the values ​​observed and the alert thresholds, in accordance with the provisions of the prefectural decree.

EDSB concludes by stating that “all available means have been implemented by EDSB to minimize the impact of this operation on the environment, while taking care to preserve the integrity of the structure and guaranteeing the safety of goods and people downstream. “.

The Hautes-Alpes fishing federation has filed a complaint. The Hautes-Alpes public prosecutor has also opened a judicial investigation for pollution.

According to this article L432-2 of the Environment Code, “Ithe act of throwing, pouring or letting it flow into the waters (…)directly or indirectly, any substances the action or reactions of which have destroyed the fish or impaired its nutrition, reproduction or nutritional value“constitutes a criminal offense punishable by two years’ imprisonment and a fine of 18,000 euros.

An investigation that will last for many months, during which the prosecution will have to determine whether the alert thresholds, provided for by the prefectural decree, have been respected by the operator when opening the valves.

Many months too, but above all years, before the Durance regains its ecological balance. The fishing federation estimates that it will take at least four years before finding an equivalent brown trout population.

We have been investing in the preservation of this species for years, all our work was wiped out in a few dayss”, concludes David Doucende.

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