The Occupational Health and Safety Act states that a general contractor must provide a construction site that is load-bearing and passable for all work to be performed. At the design stage, the choice of machinery to be used should already take into account whether the bearing capacity of the ground is sufficient. A construction site certificate is not (yet) mandatory, but would help raise awareness, according to the experts at Aboma Inspections. Because in practice, attention to the condition of the construction site is still insufficient.
In the United Kingdom, no project begins without the construction site being demonstrably load-bearing, says Pieter Bakker, operations manager at Aboma Inspections. "Such a construction site certificate is not mandatory in the Netherlands, but you have to be able to show that the construction site meets the requirements. For that reason, we are called in to conduct site surveys, measurements and calculations to assess whether the ground is sufficiently load-bearing for the equipment that will be working on it. It often happens that the machine and method has already been chosen and then the calculation shows that this choice is not the right one. It would only raise awareness among clients if demonstrable bearing capacity were asked for more in advance."
Aboma is an accredited conformity assessment body (CBI) and among other things also inspects mobile cranes, tower cranes, passenger/goods building hoists and foundation machines in accordance with the Machinery (Commodities Act) Decree. "This includes inspections as well as foundation calculations for safe deployment on site," says Sander Cornelissen, operations manager at Aboma Inspections. "During an installation inspection of a tower crane, the foundation calculation often turns out to deviate from the practical situation. If not checked, this can have major consequences. Checking this requires the necessary expertise."
The NVAF has started a working group to revise the construction site certificate. Aboma contributes to this by sharing findings, because all other equipment also benefits from a load-bearing and passable construction site. The idea that it is only about large and heavy equipment is not correct; it is ultimately about ground pressure per m2. "Instruction manuals and the lifting and capacity tables of machines explicitly state that the ground must be load-bearing in order to work safely," states Pieter. "In fact, it is the first question you should ask your client: demonstrate that the subsoil is sufficiently load-bearing. The general contractor is responsible and liable for this."
If the calculations show that the subsoil is not sufficiently load-bearing, measures will have to be taken. This could be soil improvement, the installation of dragline bulkheads and/or the installation of drainage to drain away soil and rainwater, Pieter points out as an example. Sander: "So it is actually quite extraordinary that there is insufficient attention to the topic, because by already looking at it in the design process, you can make much better choices and you could even consider other methods or the use of other equipment. Often the machines are already on site and then it turns out that the bearing capacity is insufficient. So then you are much too late."