CEDA DMC Visits the Anse du Portier Project in Monaco

CEDA Dredging Management Commission at a site visit in Monaco. (Credit: CEDA)
CEDA Dredging Management Commission at a site visit in Monaco. (Credit: CEDA)

In the past intermezzo, a lot of blog ideas past my mind. In due time, I will share some of them with you. Others already arrive by themselves naturally. e.g. Lately we’ve had another CEDA Dredging Management Commission meeting1. In preparation for the upcoming CEDA Dredging Days2, we discussed some publications that will be presented there3. Next to the meeting, we also did a site visit to a prestigious project. The Monaco extension project ‘Anse du Portier’ certainly demanded some serious management skills for the dredging works.

Overview of the Anse du Portier project
Overview of the Anse du Portier project

The extension project had already received a lot of attention in the press and in the dredging community. It certainly is a remarkable project, where a lot of disciplines are coming together. I would like to refer you from the excellent video on the Anse du Portier project itself4:

Extension en mer de Monaco – Techniques de construction (Credit: Anse du Portier Project)
Or, if you can hold your breath, to the presentation of Camille Kapella at the CEDA Dredging Days5, where she will elaborate on all the difficult challenges in the project. At the moment of our visit, the last caisson had just been placed in the construction6.

Last caisson in the constructed sea wall at Monaco
Last caisson in the constructed sea wall at Monaco

Caissons are a demanding construction in terms of dredging. Of course, there are examples, where location and placement were not so important, but usually the requirements are much stricter and the conditions much harsher. Caissons have to be placed next to each other in the first place. And joining them all together might end up in a big deviation as errors propagate through each misplacement. This has been recognised already for a long time. Even one of the first tunnels built of sunken caissons, the Maastunnel7, had specifications that are still in use today. So, how did they do this? There is a nice historic video available from the old Polygoon Journaal.

Building of the Maas Tunnel (Credit Polygoon Journaal)
In the case of the Maastunnel, they employed wires driving huge dials and sight line beacons. Under perfect conditions, enough time and an enormous amount of manpower, the objectives can be achieved. Nowadays, this approach would be too costly or can’t be used as the local circumstances prevent them. Waves, tides, difficult location or other factors are the edges of the envelope for modern caisson placement and all were present here in Monaco. Specifically, the challenges at the Anse du Portier site were the steep bedrock, the open coastline vulnerable to waves and environmental concerns. For each, of the challenges, appropriate solutions were chosen to manage the project.
The construction of the caissons to withstand the wave action during the lifetime is remarkable. The top of the caissons are equipped with so called patented Jarlan chambers8. This is a design concept known in the offshore construction to temper the wave action. Waves enter the construction through slots in the walls and enter a chamber with more columns for further dissipation of the wave energy. A similar approach is already discovered by nature itself: coastal mangrove forests.

Last caisson at the Anse du Portier with Jarlan chamber slots covered for transport
Last caisson at the Anse du Portier with Jarlan chamber slots covered for transport

References

  1. Dredging Management Commission discusses papers on contract-type selection and soil investigations, CEDA
  2. CEDA Dredging Days 2019, CEDA
  3. Effective contract selection: CEDA’s guide to optimised contracting methods, CEDA
  4. Anse Du Portier, Youtube
  5. Dredging in Monaco: challenges and solutions, CEDA
  6. Monaco Land Extension Project Reaches Milestone, Caissons Belt Completed, DredgingToday
  7. Maastunnel, Wikipedia
  8. Jarlan Chamber, Espacenet

See also