• On Tuesday 20 April on the Esplanade des Invalides in Paris, the RATP launched a full-scale exercise aimed at verifying the effectiveness of its Flood Risk Prevention Plan.

  • Maintenance workers have built structures to protect the ventilation grilles against a possible overflow of the Seine.

  • Two techniques were used: masonry protection in concrete blocks and mortar, which is more solid, and aluminum cofferdams, which are much quicker to put in place.

In the film

Pluie d'enfer

, Christian Slater is struggling with a band of thugs in the middle of the flood to try to save a formidable hoard.

And in the film

PPRI

*, the RATP tries to save its metro stations from an out-of-control Seine.

This Wednesday morning, a dress rehearsal was held near the Invalides metro.

There are no Hollywood stars here, we preferred RATP maintenance workers – it's more authentic, ask Bruno Dumont –, and in the production, we find David Courteille, general coordinator of the PPRI RATP.

As in

Pluie d'enfer

, the scenario is simple, the Seine is in flood and it threatens to spread over the Esplanade des Invalides, so the ventilation grilles of the underground metro station must be protected.

There are two methods for this: a masonry structure with concrete blocks and mortar and a structure with cofferdams, aluminum slats that stack up.

On the masonry dam, there are about ten agents working with construction helmets or green caps and green and black outfits bearing the RATP logo.

On the cofferdams, half as much.

The mortar in action

“We are trying to move from masonry to cofferdams, explains David Courteille.

It's faster and easier to set up, it doesn't require masonry skills, it's reusable, easily stored and it takes up less space.

On the downside, it costs more, which is why even today, in the RATP's flood control plan, 70% of the works are planned in masonry.

The latter are essential “in areas where the water pressure is likely to be high and where the cofferdams could give way”, specifies the PPRI coordinator.

In addition, the installation of cofferdams requires preparatory work upstream to fix their supports to the ground, but sometimes there is not the necessary depth.

The concrete mixer is running at full speed and spits out its mortar with regularity, while the agents make wooden templates and others stack the 30 kg concrete blocks.

They have for 8 to 9 hours of work before finishing this mini-speaker of 1.20 m in height.

50 meters away, around another gate, three workers erect the cofferdams and the work, more than two meters high, is completed in less than two hours.

Other RATP agents wearing blue "PPRI 2022" caps take notes for the most precise feedback possible.

“This exercise allows us to test what works or not.

Do we have all the materials?

The staff needed?

For example, you have to check that the agents are well trained and live in areas that are accessible in the event of a flood,” explains David Courteille.

The famous flood of 1910

So far, there has never been a flood on the Esplanade des Invalides, but the essence of risk prevention is to predict what has never happened.

Even if we still rely on the past.

"We are working with very precise mapping of the 1910 flood, updated to take into account new urban developments," explains David Courteille.

And the trend is towards increasing floods.

Even if it rains less often, it rains harder.

And with the asphalting of the soil, the water goes more towards the rivers, like the Seine.

»

David Courteille therefore closely monitors the height of the water at the Pont d'Austerlitz: “Building begins at 6.60 m.

» Four successive phases can be triggered depending on the rising waters.

At the final stage, approximately 800 RATP agents would be hard at work building 429 protective structures.

“In 2016, the Seine did not rise high enough for us to need to start construction, but since then we have extended the risk period from mid-November to June 1.

And every year, the RATP implements an exercise of this type to avoid a bad disaster movie.

*

Flood risk prevention plan

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A card gives you the answer

  • Paris

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  • Flood

  • Seine

  • Ile-de-France

  • flood