” Never again. » A little more than two weeks after the ban on the consumption of Arcachon oysters, which fell on December 27 due to norovirus contamination, oyster farmers and environmental associations want to understand how the marine park where the oysters rested found itself affected by wastewater from the sanitation network. Thousands of people who consumed the famous shellfish were struck by gastroenteritis the evening or the day after Christmas, leading to this ban on consumption, which is due to run until January 19.
“We will see how long it will take people to eat oysters again, after the ban is lifted, but this must not happen again,” warns Thierry Lafon, oyster farmer and president of the Defense Association waters of the Arcachon basin (Adeba). The man who is also former president of the Arcachon-Aquitaine regional shellfish farming committee has filed a complaint against X and against Siba, the intercommunal union of the Arcachon basin, responsible for sanitation.
Other complaints have been filed in recent days, in particular by the Regional Shellfish Farming Committee (CRC) of Pays-de-la-Loire, after the bans on the marketing of oysters in Vendée and Loire-Atlantique, for the same reasons. The vice-president of the CRC of Normandy, Patrice Rodes, indicated for his part that he was “in discussion with the inter-professional body” about a possible complaint, after bans in Calvados and in Manche.
“Human droppings were found in the natural environment”
Oyster farmers say they are in fact victims of pollution which is not their fault, the ban on the consumption of their shellfish falling at a crucial time of the year for them, namely just before the festivities of New Year. The loss would be of the order of seven million euros for the 300 oyster farmers in the Arcachon basin. They accuse the sanitation network of having overflowed and contaminated maritime waters. “To put it clearly, human droppings, loaded with norovirus, were found in the natural environment,” summarizes Thierry Lafon.
“I filed a complaint to denounce the overflow of the Lanton retention basin, where raw water flowed abundantly into nature after being invaded by rainwater, and I also filed a complaint against Siba in relation to its policy of “infiltration at the plot”,” explains Thierry Lafon. Plot infiltration consists of equipping each urbanized plot of the Arcachon basin with a drain to evacuate rainwater into the ground, which thus joins the water table. “It’s a very protective choice for water quality,” insists Sabine Jeandenand, the director of Siba. Except that in the months of November and December, the cumulative rainfall reached the ordinary rainfall of an entire year.
There is even talk of an episode of “hundred-year” rain. Rainwater therefore no longer infiltrated and caused flooding, even in the roads, and ended up “interfering in the wastewater collection network, before emerging loaded with contaminants, including noroviruses which are of human origin,” continues Sabine Jeandenand. The phenomenon has even been accentuated by the fact that “we are located on a watershed of more than 4,000 km2” and that with “the multiplication of flooded areas, the waters of this entire territory have flowed down to the watershed. ‘Arcachon, taking on all possible contaminants as it passes.’
“It’s not unusual to see residue on the road or in gardens…”
The director of Siba believes that the sanitation network cannot be held responsible for an exceptional climatic event, “knowing that this network is not made to transport runoff water”. For Thierry Lafon, this situation is proof that “the dogma of plot infiltration, defended since the 1980s by our local authorities, no longer holds”. If he recognizes that “80% of the time this solution does not generate a problem, because it rains little or not”, he recalls that “in the Arcachon basin the water tables are flush, and in this season, they are generally almost at ground level. Understand that there is no need for “100-year” rain to make them overflow.
“There have already been overflows in the past, and it is not exceptional to see residue with traces of toilet paper on the road, or in the garden of certain individuals,” denounces the oyster farmer. “What was new this time was that the gastroenteritis epidemic arrived, and ultimately this is what brought visibility to the overflow phenomenon, which is recurrent in the basin. »
The “insufficient” sanitation network in the face of galloping urbanization?
And the situation is unlikely to improve, if we are to believe several environmental associations which point the finger at the urbanization of the Arcachon basin. Sepanso (a federation of associations for the protection of nature and the environment) of Gironde denounced a few days ago “the frantic development of urban planning and the increase in population around the Arcachon basin (+1.9% per year).” She is concerned that the SCOT (Territorial Coherence Scheme) currently being approved provides for a continuation of this demographic growth of 1.1% per year over the next ten years, resulting in the production of 30,000 new housing units overall. of the period, even if the document insists on the “preservation of natural spaces”.
“Urbanization means that the sanitation network is in greater demand,” says Thierry Lafon, “and above all it is done in total denial of the very nature of this territory which was originally a marsh. » “The network is undersized,” says Bruno Hubert, of the Audenge Citoyenne association, “and we are paying for twenty years of denial regarding the consequences linked to town planning. » The latter is also worried about climatic events, “which will be more and more intense and more and more frequent” in the coming years, “which can only accentuate the phenomenon. » The director of Siba retorts: “Urbanization in the basin is absolutely not the subject. Proof of this is: when we changed the main collector which discharges the wastewater (into the ocean and after treatment) to the wharf of La Salie, we reduced its diameter. »
Thierry Lafon, for his part, does not budge: the salvation of the natural environments of the basin will require the rehabilitation of ditches and pits, which tend to disappear. “These networks dug in the past made it possible to evacuate rainwater and avoid these problems,” he maintains, even if he recognizes that it would be “a complicated job” to restore them. “But the phenomenon will happen again if we continue as is,” he warns.
The prefect of Gironde announced for his part that he was going to convene the communities to a meeting focusing in particular on the investments to be made in terms of sanitation and rainwater management.