Testimonio II: a technical worksite of high environmental quality

Key point: Springs and the sea

Two fresh water springs have an impact on the Testimonio II site.

One, the Testimonio spring, runs through it. The other, the Marie spring, runs alongside it.

Both are collected, to provide a significant share of the Principality’s freshwater supply, or else are discharged into the sea.

It was therefore essential for the works to have as little impact as possible on these water resources, without generating any discharge of mud or grout into the sea.

To preserve these environments, we therefore:

• Created a drainage gallery with the aim of collecting the Testimonio spring
• Pre-injected the ground prior to construction of the diaphragm walls and barrettes
• Installed pumps and turbidimeters in the valley into which the springs flow before reaching the sea, in order to recover and treat any water that could have become mixed with drilling mud.

Other actions:

• Installation of a compact worksite water treatment plant (up to 100m³/h)
• Installation on the worksite of retention tanks, selective sorting, anti-pollution kits, a Tribox, etc.
• Removal of trees (endemic olive trees) for subsequent replanting

Key point: Low-carbon concrete
The work carried out jointly by the materials laboratories of Soletanche Bachy, VINCI Construction and the concrete supplier (EMT) made it possible to define and implement ultra-low carbon concrete reducing CO2 emissions by more than 6,000 tonnes just for the concrete used for the diaphragm walls and barrettes (25,000m3 out of the project’s 100,000m3). To achieve this, fly ash from Gardanne and ground slag from Fos-sur-Mer were used as cement substitutes.

Key point: The development and installation of a compact electric Hydrofraise® with  grippers – the HC05GE

This is the most spectacular innovation implemented on the Testimonio II site. In fact, it is disruptive on two fronts.

1/ The move from the HF07 to the HC05 with grippers® in 2019 significantly reduced fuel consumption by reducing the power of the machine required for excavation.

The gripping impact was very effective as it maintained the level of efficiency with a much more compact machine.

2/ The move from the HC05G to the HC05GE. With further optimised efficiency (greater reliability of the power pack and more linear operation), this new innovation eliminated all CO₂ and combustion gas emissions while saving nearly 5,000 litres of fuel per week of work (more than 60,000 litres in the last phase of the works alone).

Other actions:

• Use of Hi’Drill® (Sonic) drilling: no compressor required, so reduced fuel consumption
• Use of hybrid high-capacity rotors running on bio-fuel: no CO₂ emissions during the concreting phases and fewer trucks on site.

Much remains to be done, but the Testimonio II site is seen by the construction industry and the authorities in Monaco as exemplary in terms of its performance and the concrete and particularly effective efforts that have been put in place to dramatically reduce the worksite’s impact on the environment and on local residents.

In order to succeed, it is essential to bring together the expectations of the public authorities and the project owner and the collective energies of all the partners in the operation in a relevant manner (VINCI Construction Monaco, GTM Sud et Soletanche SAM).

Nevertheless, credit where credit’s due: almost all of the solutions described above were due to the collective commitment of the Soletanche SAM and Soletanche Bachy teams.

The will to succeed was there, but it could not have happened without the complete commitment and pride of the teams on the ground. Thank you to them all.

We are convinced that these actions play a large part in restoring leadership to Soletanche SAM and, more broadly, to the VINCI Group in a very tough competitive environment.