Near Rouen, are the Seveso factories preparing for the rising waters?
By Valentin Lebosse
Published on
The Seveso factories close to Rouen (Seine-Maritime) are they threatened by rising waters ? The question may seem incongruous at the end of a summer 2022 marked by drought and the alarming drop in the level of certain rivers.
However, the projections of the Intergovernmental Panel on Climate Change (IPCC) are clear and there is now a consensus: without a drastic drop in greenhouse gas emissions, sea levels could rise by one meter by 2100.
“More numerous and more intense floods”
In an estuary like that of the Seine, subject to the influence of the tide up to the dam of Poses (Eure) upstream of Rouen, this rise in sea level contributed, according to a summary by the Normandy IPCC, to “more numerous and more intense floods”.
In order to better characterize the evolution of flooding in the Seine estuary, the Seine-Aval public interest group (GIPSA) carried out a study published in February 2022. Using a numerical model, GIPSA a simulated multiple flood scenarios.
Floods of more than 10 meters?
“The most realistic” according to Jean-Philippe Lemoine, coordinator of the study, consists in “replaying” the flood of December 1999, that of the “storm of the century”. With the current sea level, the Seine would reach 9.82 meters in Rouen. That is 60 cm of water above the quays. Currently, such an event can occur once every 12 years.
But taking into account the rise in sea level anticipated by the IPCC (+ 1 meter in Le Havre), a typical 1999 flood exceeded 10 meters in the Norman capital (20 centimeters more than today).
In this simulation, the industrial zone between Petit-Quevilly and Grand-Couronne would be largely flooded, much more than today (map above). To the point of endangering the Fifteen Seveso sites (seven low threshold and eight high threshold) located in this sector?
Hazard study
The industrialists who accepted to answer the questions of 76news want to be reassuring. At the house of Ruby Terminal“we do not identify no major risk on our facilities”, assures Stephane Simon. The director of terminal products in Rouen is at the head of a site which has a storage capacity for liquid products (fuels, fertilizers, food, etc.) of 778,000 m³ – the equivalent of 311 Olympic swimming pools.
Due to its Seveso classification (high threshold), the company must produce a hazard study. This includes in particular the risk of flooding. “It’s an inventory, we identify potentially flooded facilities and those that are not,” says Stéphane Simon. By asking for measures (choice of location of sensitive installations, installation of protections) which, according to the prefecture of Seine-Maritime, “make it possible to reduce and control the risk of accident due to flooding”.
To carry out this hazard study, the industry must take into account the “reference flood water level”, indicated in the flood risk prevention plan (PPRI).
Two different floods are taken into account in the PPRI, that of 1999 downstream of Rouen and that of 1910 in Rouen and upstream.
“The height of the water rises upstream from Rouen”, reference threshold go of 9.58 meters at Grand-Couronne until 10 meters at Petit Quevilly. Belowtherefore, from the height what could a 1999 type flood by 2100.
Reinforced protections
However, “in order to take into account the uncertainties of the model”, the prefecture requests “a margin of 30 cm on urban planning projects”. At Rubis Terminal, “we have been building or upgrading our facilities (terminals, tanks, electrical rooms, etc.) for around ten years. 50 centimeters above the regulatory dimension. This is the only and best technique to ensure the sustainability of the site”, emphasizes its director.
The tanks are also surrounded by retention basins and walls “three meters high”, “whose primary function is to prevent the escape of products to the outside but which also prevents water from entering”.
Also asked about its flood protection features, Butagaz (Seveso upper threshold), at Small Crowndid not detail them but ensures that it invests “2.5 million euros each year to ensure the compliance and security of [ses] facilities “.
“It’s going faster and stronger than expected”
Is all this enough to guard against future overflows of the Seine? Guillaume Grima questioned. The representative of the association Greenhouse Effect Yourself points to the acceleration of the upheavals induced by climate change: “The IPCC is already telling us that things are going faster and stronger than what was predicted in the 1990s and 2000s.”
If the + 1 meter in Le Havre is ultimately 1.5 meters, we will not control it, the retention basins will be full everywhere!
The activist is also concerned about the potential difficulties of access to the industrial zone for relief in the event of flooding. In fact, the boulevard Stalingrad/maritime would be under water.
Move factories?
For Guillaume Grima, this is obvious: “These factories will have to be moved to a location further away from homes, without the risk of road congestion in the event of an accident. »
The idea also seems to be gaining ground in the Rouen Normandy Metropolis. son president Nicolas Mayer-Rossignol “not excluded[t] not the relocation of certain industrial sites”, according to proposals received by our colleagues from Paris Normandy. Solicited by 76newsthe mayor of Rouen did not wish to “comment” on his statements.
Guillaume Grima, he would like the Metropolis to take this subject head on. So that “the options for the development of the territory are better known to the inhabitants”, he proposes “participatory reflection”. “It is up to the Métropole to set up meetings between associations and manufacturers. But a move is not part of Stéphane Simon’s plans.
Proximity to the Seine is essential for an energy terminal. Moving the site further inland is utopian, we would be totally dependent on transport by pipeline, the network of which is currently undersized.
“The installation has to adapt,” continues the manager of Rubis Terminal in Rouen, who is watching “regulatory changes”. “We have not been required, for the moment, to carry out new hazard studies integrating IPCC consumers. »
A lack of anticipation?
On the side of the prefecture, we note that “the new data, which incorporates the effects of climate change, represent a perspective for the 2100 deadline. In the short term, in the first analysis, the likely risks are subject to Seveso sites decline little . »
“The revised PPRIs will be intended to regulate use for new constructions,” add the authorities. It should be noted that the PPRIs for the Rouen loop were approved in 2009 and partially modified in 2013.
We continue to prepare for the worst by starting from a past or present state of nature, while scientists tell us that phenomena of an intensity unknown today will occur more and more often.
The representative of Effect de Serre Toi-Même calls for “an evolution of the administrative culture”. So that “the adaptation of the territory is no longer based only on what has happened to us but on what can happen to us”.
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