For this area of 126 hectares, situated outside the dikes and representing a realistic flood risk, the decision was made to realise a secondary partial infrastructure for pedestrians, at a height of 7.5 metres above NN (Normalnull, the German term for the Amsterdam Ordnance Datum). That higher level can also be used for emergency services in the case of high water. The existing ground level in HafenCity is 3.5-5.5 metres above NN, which is not high enough. The level of 7.5 metres is higher than the highest flood level on record. The ground floors of all buildings are also sealed up to that level, with the exception of entrances and similar openings. All openings (doors, windows, etcetera) can be closed in accordance with special guidelines.
The owners/developers are responsible for the costs associated with raising the buildings. The bases of most buildings are used as parking garages. The advantage is that this renders ground-level parking unnecessary and that a relatively large proportion of the land can be issued. The raised infrastructure, over which the district can be evacuated safely and quickly even in the case of high water, was funded by the Hamburg municipal authorities. HafenCity Hamburg, 2011