Whether it is a question of creating and maintaining shipping channels and ports, or carrying out beach nourishment operations, dredging companies are regularly called in by contractors. These companies charge for their services on the basis of the volumes that are dredged. Hence the importance of having these quantities checked by a service provider external to the company carrying out the work.
This obvious deontological evidence masks the stakes and sometimes financial problems that it is worth recalling.
The cost of dredging work varies according to many parameters: the size of the project, the cost of mobilising resources on site, the working depth, the nature of the sediments or the hardness of the soil, environmental constraints, the distance to be covered from the disposal area, etc…
If, for the purposes of the demonstration, any dredging project is considered, which would consist of dredging from -10m to -12m LAT over an area of 25 hectares of moderately hard material (UCS = 20 Mpa).
This would represent approximately 500,000m3 of material to be extracted. For a price between 15 and 25 euros per cubic meter, this would represent a project of about 10 Million Euros and, let’s say, one month’s work.
At the same time, the hydrographer’s mission can be broken down into three stages. The bathymetric survey “IN SURVEY” with the multibeam echosounder for the estimation of volumes before start-up, the “CONTINUOUS MONITORING” during, and finally the “OUT SURVEY” after works, which allows to confirm the objectives, and possibly adjust the volumes payable to the contractor.
During these three stages, the hydrographer is the guarantor of the reality of the work and the fair remuneration of the contractor. He is responsible for controlling :
1. The respect of the perimeter of the borrowing zone (dredging) and sometimes of the dumping (disposal) zone.
2. The management of unreached dredging areas, i.e. areas that are insufficiently dredged because they are at a higher level than the objective level, and for which the company is asked to take them over without financial compensation.
3. The management of dredging spoil, i.e. dredged areas which are dredged at a lower level than the objective level and which are not taken into account in the calculation of the volume of dredged material for which remuneration is payable.
The bathymetric survey that accompanies a project of about 1 month of dredging has an average cost estimated at 100,000 Euros. For a project costing 10 million Euros, the cost of this service therefore represents approximately 1% of the total cost.
To these costs must be added the drafting of the technical specifications for the calls for tenders to consult the various dredging companies, which are prepared well in advance of the work. In order to do this, the contractors must do an assessment of the conditions, which in addition to bathymetry to calculate the volumes to be extracted, must sometimes include geotechnical investigations, sampling and measurements on site for Environmental and Social Impact Studies.
Of course, the requirements of the projects are always different. But for maintenance dredging for example, the cost of these preliminary studies usually does not exceed 50,000 Euros.
It is therefore understandable that our work is essential for an impartial management of dredging projects, and proportionally it represents a reasonable financial burden.
However, port operators or administrations sometimes face the problem of financing 1% of the control mission, which is not budgeted independently of the 99% that dredging works represent.
And so, unfortunately, there are still situations where the responsibility for the control mission is delegated to the contractor carrying out the dredging works. This is not always due to a lack of deontological rigour, but more often because the financing mechanisms of the project do not allow the contractor any other possibility.
To hope to see things evolve, all we have left is pedagogy, patience, and blogs.
Raphaël PACOT
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