Transforming a nuclear fallout shelter into a data center in Paris

Kevin Messy
5 min read

From nuclear fallout shelter to data center
Scaleway celebrated its 21st birthday, and what a journey it has been! From Online Dedibox to Scaleway, we have been disrupting the hosting world for more than two decades, making Scaleway the fastest growing cloud provider worldwide.

We are now taking things up a gear by making Paris the first multi-AZ region. This is a huge step toward our goal of offering true, world-class, resilience. And, to really make our multi-AZ pack a punch, we are relying on fr-par-3, an exclusive AZ located in a former nuclear fallout bunker, built to meet extraordinary infrastructure requirements.

Discover how Scaleway is able to leverage its decades-long excellence, transforming a nuclear fallout shelter into a data center.

The former nuclear fallout shelter

Originally called “Abri Lefebvre”, fr-par-3 was a passive defense shelter built between 1937 and 1939 under the Ponts et Chaussées laboratory. The laboratory is located on top of an empty quarry, dating back to the 17th century. The quarry is 26 meters deep and protected by a 10 meters thick limestone deposit.

The construction started in 1937 and was completed in 1939. At this time, the facility was designed to shelter up to 90 persons with a floor space of 650 square meters. A large part of the construction work consisted in reinforcing the empty quarry and making the shelter accessible via an unusual double-spiral staircase.

In April 1964, during the Cold War, the department of Civil Aviation took over the management of the shelter and undertook a massive project: transforming the bunker into a nuclear fallout shelter.

The goal was to increase the shelter surface to 950 square meters and expand the capacity to 300 people. The extension works were planned to last 4 to 6 months and were focused on the southern side of the empty quarry.

Additionally, we made a few improvements: a closed-vent system, a diesel generator-backed power supply, several blast doors, an autonomous telephone exchange connected with the other Parisian nuclear fallout shelters, and a water supply system.

The shelter was operational, and classified confidential until 1991 before being discontinued. A publication by Cabu in satirical newspaper Charlie Hebdo drove the French government to stop maintaining the shelter.

The shelter was abandoned for 20 years. It quickly became a mythical spot of the catacombs of Paris and suffered degradations and theft.

The building transformation by Scaleway

In 2011, the French government, which owned the building at the time, decided to move the Ponts et Chaussées' central laboratory to the Parisian suburbs. Its buildings were revamped and divided into multiple units to be sold and transformed into multi-unit housing.

The main building and the shelter were sold separately via a public invitation to tender. Online SAS (now Scaleway SAS), which had a project to build a data center in its place, landed the deal in September 2012. The project’s codename was DC4.

A short period after acquiring the building, we set ourselves a challenge: transforming the site into a high-end data center. The unique character of this nuclear fallout shelter was due to its location, in the Paris city center, to its warlike history, and to its quasi impenetrability. Furthermore, we were constrained by our insurance and certifications to stay true to its nuclear fallout shelter characteristics and to reinforce it so that it could sustain a total demolition of the building at ground level.

The project challenges were monumental and required our teams to show creativity and skill.

The first step of the construction consisted of removing the existing equipment inside the shelter and preparing the floors, ceiling and walls for the upcoming equipment. This first phase lasted approximately one year.

Then, a 25 meter deep hopper was created from the surface to install a freight elevator. During this period, more than 360 tons of equipment and backfill were removed from the shelter, offering a totally clear space to start the second step of the project, that is the underpinning and structural works.

The project required an ultra resistant slab to support power supply and IT equipment. Each C14 rack weighed over one ton supported by less than one square meter of floor. It created four punctures of 400Kgs per square centimeter.

In addition, to make the shelter completely autonomous, we had to install more than a hundred tons of electrical distribution equipment including batteries, UPS and transformers. Finally, achieving complete shelter impermeability was an amazing challenge.

We had to fix this issue with advanced technical methods. We worked with SOTEM, a company specializing in waterproofing operations and known for building and maintaining the impermeability of the Métropolitain of Paris.

We fixed the residual seepage issues by injecting an expansive resin. We created drains in each vault. Then we applied watertight lining made of resin to the walls of each vault to make them totally waterproof. The resin was applied in three overlapping layers. For the last one, we mixed the resin with silica to prepare the surface for the next step, which was the laying of the tiles for the métro. For this operation, over 3,000 square meters of tiles were required!

In 2016, we deployed our first product in DC4: C14, our cold storage offer that will later become "Scaleway Cold Storage".

In 2021, we are upgrading our Data Bunker to a full-fledged AZ. Making Paris better than ever: our first Full Region !

12 years of expertise and excellence

We hope that you liked this little tour around the often overlooked treasures of Paris. If you want to learn more about the amazing things that Scaleway is doing everyday, here are some articles we recommend:

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