Older buildings in Amsterdam are resting on wooden piles, while more recent buildings have been built on piles of concrete. The piles in the city centre are approximately 15 metres long and are supported by the first layer of sand, which is strong enough to hold them.

Quite a bit deeper – 20 to 30 metres below the surface – there is a second layer of sand. And that is where the metro tunnel is being built. There is no danger of the boring machine coming into contact with the wooden foundation piles.

Metre for metre, the soil conditions along the entire route of the Noord/Zuidlijn have been identified. That was a big job, and it was undertaken with great attention to detail. But despite all the care that went into the preparations, the chance that some of the buildings along the route may settle cannot be ruled out entirely.

That is why precautionary measures are being taken at vulnerable locations. These measures primarily have to do with reinforcing the soil and improving the foundations.

Examples of places where the foundations have been improved include the Beurs van Berlage building on Damrak and the French Consulate on Vijzelgracht. Places where the soil is being reinforced include the ‘Industria’ building on Rokin, the department store ‘De Bijenkorf’ on Dam Square and the Munttoren at Muntplein.

Groundwater
The groundwater level is important for the condition of the wooden foundation piles in Amsterdam. Those piles will begin to rot if they are only partially underwater.

When they are either completely dry or fully underwater, there is no problem. It is therefore necessary that the groundwater level always be taken into account during the construction activities.

No water is being removed from or added to the soil in connection with the construction of the Noord/Zuidlijn. Since watertight constructions are being used during the tunnel-boring process and in the construction pits, the city’s foundations are in no danger.