The Grand Paris Express: a non-standard construction site 

Considered the “project of the century”, the Grand Paris Express is a new public transport network. Comprised of four metro lines on the outskirts of Paris with 200 km of new tracks, it will profoundly transform the mobility of Parisians and reshape the entire geography of Greater Paris. 


The Grand Paris Express: a non-standard construction site 

Under the responsibility of the Société du Grand Paris (SGP), the Grand Paris Express is the largest urban project in Europe. Although 2019 is far from over, it has already been characterized by the acceleration of activities related to the Grand Paris Express.Fifteen tunnel boring machines have been deployed and many preparatory work sites are turning into civil engineering project sites. The awarding of the 2024 Olympic Games to the capital has clarified the planned investments and determined the schedule.  

In total, at least 21 tunnel boring machines will work simultaneously to dig at an average depth of 30 to 40 meters (compared with the Paris metro which is just 10 meters below ground level). The first tunnel boring machine started creating the network’s future line 15 back in January in Champigny-sur-Marne, with completion expected in 2020. 

In addition to this new automated metro system, the Grand Paris will provide: 

  • 4 new metro lines 
  • 68 new stations 
  • 4 extensions to existing lines  
  • 200,000 m2 of shops and businesses  
  • 70,000 new housing units per year 


On average, the size of a construction site for a station on one of these new metro lines is equivalent to that of a 10-story building dug into the ground, at around 100 meters long and 70 meters wide.  

A construction project of such a scale is inevitably a source of all kinds of risks and disputes. In this context, it is obviously essential to be familiar with the various technical issues that may arise, but this alone is not enough: damage surveys must also be based on a perfect understanding of the functioning of public and private works contracts. This knowledge is essential for the proper handling of an amicable or court-ordered appraisal assignment, which may be initiated in the context of a claim or dispute between several parties. 


Varied and highly technical claims 

Public liability claims do not concern the construction sites themselves but essentially relate to damage to what is there already. This has been the case for many third parties residing outside the Grand Paris sites who have been reporting issues such as those linked to vibration phenomena caused by the work, such as cracks. Particle velocities are not usually likely to threaten the integrity of the neighboring buildings, but that doesn’t make them any less noticeable, and they may be seen as a nuisance by those living in the vicinity of the construction site. It is up to the loss adjuster to determine for each case if the vibrations caused by the work are responsible for the cracks. To do this, they analyze particle velocity measurements at the construction sites and then consider their distance from the affected structure. 

There are multiple risks for the project owners and companies; they exist during construction, but also after acceptance of the work. In effect, the 10-year warranty covers damage to construction for up to 10 years. Therefore, the public liability of project owners can be engaged long after the work is complete.  

The Grand Paris Express project is expected to continue until at least 2030. In the long term, it will help to create at least 115,000 jobs, and the Grand Paris Express will bring France an additional €10 to €20 billion of GDP per year.The risks are likely to evolve with the development of this colossal project and as time goes on. Therefore, insurance companies, as well as loss adjusting firms, will have an important role to play to ensure good risk management.


Nicolas CHAUVET, Construction Loss adjuster

TGS | Stelliant group

Find out more about his are of expertise