Selective withdrawal is special and unique

Jos den Hollander is technical manager design phase at VHB. He is responsible for everything that happens during the design process of the salt dam and is happy to tell us more about this. From the planning to the budget and the quality of the design.

The design team at VHB prepares the construction and makes drawings and calculations. He ensures that ‘everyone is on the same page’ in the design phase.

We looked at what and how we wanted to build it.

Josh the Dutchman

The project in mini form

Den Hollander explains that the design process starts in the tender phase. This is the phase where VHB prepares a tender design in order to submit a reasoned offer to Rijkswaterstaat. In order to arrive at a plan and price, VHB reviews the entire project in miniature form.

The Dutchman: ‘In this 1e phase we have already made a conceptual elaboration of the design. We looked at what and how we wanted to build it. How much time will it take and how will we deliver the work.

In order to determine the price justification correctly, we needed to know, for example, how much concrete and steel we need. But also how many people we need for the design and for the construction site itself.’ After we awarded them the job, the contractor could really get down to business with the design.

From system design to implementation design

Within the design process, VHB goes through 4 phases. Starting with the system design phase. The Dutchman: ‘In this phase we sat down with Rijkswaterstaat to discuss the contract and requirements. In this way, we are sure that we are designing what Rijkswaterstaat really wants.’ Then the preliminary design phase takes place.

The Dutchman: ‘We make the first drawings and calculations at a high level of abstraction. Where should we build what? How big? And what does this look like? In this phase, we also take the first steps to coordinate design and landscape integration.’

After going through these first 2 phases, the contractor was able to go deeper into the final design. Den Hollander explains what kind of questions were investigated: ‘What are the exact dimensions of various parts? How big and how long is the tubular pile to be driven into the ground? How thick are the walls exactly? And how much reinforcement should be placed in the concrete?

From this, the salt dam is built step by step.

Josh the Dutchman

Once this is clear, the design can proceed to the final phase, also known as the implementation design phase. In this phase, according to Den Hollander, VHB is really looking at the salt dam at ‘bolts and nuts level’.

For example, we look at how the reinforcement of a concrete part, technical installations, lighting and other facilities look in detail, and how these things should be mounted.

The Dutchman: ‘When we have all such questions ready, I transfer all documents per component to the technical manager for the implementation phase. From this, the salt dam is built step by step.’

A 3D design to bring it all together

According to Den Hollander, what VHB is building for the salt dam has a unique design and construction. To do it as well as possible, VHB used 3D design when designing the salt dam.

The Dutchman: ‘We actually make everything in 3D and so do our subcontractors. As the main contractor, we collect all 3D models in 1 3D coordination model. All models are interchangeable and collectable. In this way, the various interfaces can be properly coordinated with each other. Another advantage of the 3D design is that you can easily determine certain quantities.’

VHB has also delivered the 3D design to us in the various design phases. In this way, the client could see exactly how the construction works in the 3D model.

The Dutchman: ‘We are used to only delivering drawings. Then you sometimes miss crucial information. Via 3D, you can rotate the design and see it from any angle. This makes it transparent and easier to understand for everyone.

Safety first

VHB works together with several subcontractors such as Spie, Vialis and Van den Herik. As a result, around 180 people work on the salt dam. Safety is a topic that has been discussed a lot during the design process.

The Dutchman: ‘Safety is an important guideline in our work. It is important to always consider whether our design can be built safely by all involved. We are constantly discussing this with each other and with Rijkswaterstaat. A project is by definition a failure if an accident occurs.’

We therefore look carefully at safety inside and outside the design phase. That way, we know we’ve done everything we can to prevent something serious from happening.’

Leave a Comment