— News — Testimonio II: a technical worksite of high environmental quality

Since 2017, the scale and complexity of the work being carried out on the Testimonio II worksite in Monaco have become legendary.

This project has been an opportunity to implement, accelerate and even develop in synergy with the owner (Marzocco Group and VINCI Immobilier) and VINCI Construction, a large number of actions falling within the scope of objectives defined by the Soletanche Bachy group’s environmental action plan.

Here we review – thematically, from the most spectacular to the most common – all the actions which have contributed to the virtuous transition currently being adopted on our worksites.

 

1/ ENVIRONMENTAL PRESERVATION

• 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

 

 

2/ PRESERVATION OF RESOURCES

• Key point: Incorporated supplies (concrete/cement/steel)

 

The human and technical resources adopted to monitor methods and technical studies made it possible to optimise adjustments to the project phases while allowing strict monitoring of the observational method, in order to optimise or even eliminate certain unnecessary structures, including:

• Removal of a 450m³ supporting wall in the main excavation site
• Removal of a bed of anchors (750 linear metres of 12 T15 anchors)
• Use of Starsol® piles for the foundations of the International School (410m³ of concrete saved (-30%)

 

Other actions:

• Use of unused water from the springs and pumping wells for drilling and washing.
• Closed-circuit recycling of drilling water
• Use of crushed concrete for some work platforms (recovery of waste)
• Servo control of the lights in the communal areas of the worksite amenities
• Servo control of the air-conditioning, dependent on windows being closed
• Still to come:
  • Use of spring water for irrigation of a shared garden
  • Use of spring water to supply the sanitary facilities

 

 

3/ REDUCED CARBON FOOTPRINT

• 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.

 

 

4/ REDUCTION OF WORKSITE NUISANCE

• Key point: The reduction at source of noise pollution from our construction equipment.

 

Worksites in dense urban areas, and in Monaco in particular, can cause a lot of disturbance to local residents. This subject is now a vital issue for current and future work.

Following actions by the authorities to adjust working hours and large-scale but often inefficient deployment of noise-barrier tarps, we decided take much more efficient action by tackling the problem as close as possible to its source:

• Use of less noisy methods
• Modification of machinery to reduce their noise impact.

 

At Testimonio II, for example, the Soletanche Bachy technical and equipment teams have developed and implemented:

 

• The Compact Electric Hydrofraise with Grippers® – HC05GE (a first in France and Monaco).

The improvement recorded by Bureau Veritas, appointed by the Monegasque authorities, is 5 to 6 dB (A) compared with competitor’s compact machines, corresponding to a four-fold reduction in noise impact. In fact, since the grippers add more power to our compact Hydrofraise®, it can be compared to the most powerful machines on the market, against which Bureau Veritas records a difference of up to 15 dB (A) in favour of our HC05GE.

 

• Widespread use of Hi’Drill® (Sonic) drilling instead of down-the-hole hammer (DTH). Once again, Bureau Veritas indicates a 10 to 20 dB (A) improved performance by the Hi’Drill® technique compared with the DTH hammer.

 

These two innovations, particularly the HC05GE, have made a profound impression on the technical services in Monaco since nuisance reduction is an important topic in the Principality.

 

Other points:

• The use of gripper on the Hydrofraise® greatly reduces vibrations when drilling in blocks and therefore reduces disturbance to local residents
• Installation of acoustic protection for the vibrating sections of the drilling mud treatment plant

 

• Removal of the wall rubble collection hopper
• Cladding of drill rigs (head and engine)

• Protection of the Starsol® F2800 rig’s drilling head using noise-barrier tarps

• Use of a special tool to empty pile rigs’ buckets
• Systematic installation of the “Lynx call” alternative reversing signal on equipment
• Installation of very high and very effective noise-barrier fences and tarps wherever possible around the perimeter of the project by the VINCI Construction teams

 

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.

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Some key figures

 

• An average reduction of 6,400 tonnes of CO₂ emissions
• Almost 5,000 litres of fuel saved per working week
• A four-fold reduction in noise impact thanks to the electric Hydrofraise® and even more for the Hi’Drill® (Sonic) drill
• 5,000m³ to 10,000m³ of water saved