PORR special civil engineering completes technically challenging construction pit near the Rhine in Düsseldorf

Special civil engineering

PORR special civil engineering completes technically challenging construction pit near the Rhine in Düsseldorf

Düsseldorf, 28.08.2025 / Construction pits / News / Press Release

An administrative centre for the state government of North Rhine-Westphalia is being built on the approximately 18,000 square metre site of the former Ministry of the Interior at Haroldstraße 5 in Düsseldorf's government district. NRW.BANK is constructing its new headquarters in the immediate vicinity. After winning a public tender from BLB NRW, a consortium consisting of the Düsseldorf branch of PORR special civil engineering and Becker Sanierungstechnik was awarded the contract for the dismantling of the existing buildings as well as the construction of a 17,500 square metre construction pit up to 19 metres deep.

Construction site with active building work: a worker in yellow protective clothing operates a concrete mixer in the foreground. A crane, an excavator and the striking Rhine Tower are visible in the background. — The complex excavation pit shoring forms the basis for a new administrative centre for the state government of North Rhine-Westphalia – in close proximity to the Rhine.

A total of around 170,000 cubic metres of enclosed space will be demolished between summer 2024 and spring 2025. The runtime for the watertight excavation pit shoring is estimated at one and a half years. 140,000 cubic metres of construction waste and excavated earth will have to be removed.

Technically challenging excavation pit shoring in an urban context

The special civil engineering package includes the construction of 18,650 square metres of diaphragm walls. These will be anchored up to five times and will be 42 metres deep with a wall thickness of 1 metre. In addition, measures will be taken to control the groundwater. The water table will be lowered below the level of the construction pit floor and the collected groundwater will be discharged into the Rhine via an elevated purification plant.

In the north of the construction pit, the existing outer wall of an underground car park will be used as construction pit shoring. To this end, it was planned to reinforce the existing outer wall with a back-anchored in-situ concrete facing. With the support of Porr special civil engineering Planung, a special proposal was implemented to secure the underground car park using a back-anchored steel frame construction, which leads to considerable savings in resources and also has financial benefits. At depth, below the outer wall of the underground car park, the construction pit is sealed using a freezing device. The ground freezing method – a state-of-the-art and minimally invasive process – temporarily stabilises the subsoil by artificially freezing the pore water. This method reduces vibrations, protects existing buildings and allows for natural regression after completion of the construction work.

A striking feature of the construction pit is the height difference of around 7.2 metres at the bottom of the pit, which results from the different foundation levels of the future building sections. The difference in level is compensated for by an overlapping bored pile wall, which divides the construction pit into two levels and provides structural stability. In the lower area, the existing underground car park wall is additionally underpinned and reinforced with a tangential, back-anchored bored pile wall.

The construction pit walls are monitored by surveying techniques during all construction phases.