Following the traces of the Second World War: unexploded ordnance survey for the safe construction of an operational center & a technical systems center in Nuremberg
Before the construction of the new digital operational centers and technical systems centers in the Tullnau district of Nuremberg can really get underway, our Digitale Schiene Deutschland (DSD) project team has one more important task to complete: the geotechnical investigation. In order to make the subsoil safe and accessible at certain points for the subsequent construction work, the horrors of the past – the explosive ordnance from the Second World War – must first be identified. For this not entirely harmless task, the project team is working with explosive ordnance and explosives specialists.
A new operational center (BSO) and a new technical systems center (TSO) are being built in the Tullnau district of Nuremberg as part of the DSD. Both buildings are part of the Operations Control Strategy (BSS), according to which 94 BSO and 52 TSO are being planned and built nationwide in order to be able to control train traffic in a more modern, decentralised and flexible way in future.
Before construction of the BSO and TSO in Nuremberg's Tullnau district begins, the project team faces an important challenge: following the precise selection of the site, the first step in recent weeks has been to thoroughly examine and extensively secure the site. The transport infrastructure – especially in the vicinity of the railway station – was repeatedly the target of heavy attacks during the Second World War. Nuremberg was particularly targeted by the Allies due to its ideological importance for the National Socialists and its strategic location. For the Nuremberg Tullnau site, this means that dangers such as unexploded ordnance, bombs, artillery and ammunition may still be present underground.
The explosive ordnance experts carefully drill their way underground
In practice, this is done as follows: the specialist company commissioned examines the ground on the site at predetermined points. The experts use old aerial photographs from 1945 as a basis, which show bomb craters that can provide information about potentially dangerous areas on the site. The explosives specialists work the first one to two metres with georadar and excavations before the drill penetrates further underground.
"The explosives specialists test to a depth of six metres during progressive drilling. The starting point is the upper edge of the terrain after the bombing in 1945, and a probe is used to search for possible aerial bombs with a radius of 0.75 metres, which reliably assesses electromagnetic influences. If a drilling point is located in the area of a bomb funnel, we have also had further measurements carried out within this funnel," explains Patrick Marbach, the project management engineer responsible.
Exploded ordnance surveys are not without danger, but the trained personnel of the specialised company on site know exactly what to do and how to deal with the risk properly. No aerial bombs have been found during the drilling so far.
"The findings are later incorporated into the implementation planning. We are trying to integrate the secured and measured areas from the current geotechnical investigation into a grid in the best possible way so that we can then safely search the entire construction area for explosive ordnance," Patrick Marbach continues.
Thanks to the explosive ordnance survey, the project team can examine the subsoil in the next step. Among other things, the soil conditions will be analysed in more detail: How stable is the subsoil? What about the groundwater? Is there any chemical contamination or pollution of the soil? All of this will be scrutinised more closely. Another large drill penetrates to depths of up to 26 metres and extracts appropriate soil samples, which are then examined in depth in the laboratory. Sometimes the laboratory analysis has a direct impact on the planning of the construction project: perhaps the originally planned construction method does not match the soil conditions and adjustments need to be made. This can change the construction process, but is an important realisation for the project team. After all, only those who know the ground correctly can erect a safe and stable building. The Nuremberg project team is already in the middle of this process and is now awaiting the laboratory results, which were requested after the work to date was completed. This brings the start of construction closer step by step.
