Oops, a digger!
What is happening on the Charlottenbogen construction site and why – a brief insight into a major project.
On such a construction site, an incredible amount of coordination, agreement and preparation is required. At the very beginning, for example, before anything happens at all, professional explosive ordnance seekers must check whether there are any remnants of explosive ordnance from the Second World War in the ground. Not that the excavator might accidentally hit a remaining aircraft bomb weighing several tons with its heavy shovel. 25 suspected cases have been found in recent weeks and months. Nothing big or even dangerous among them: just a few cartridges and the remains of a hand grenade. They have recovered and disposed of them.
After that, the soil surveyors will come. They divided the 10,000 square meters of building area into small units and took soil samples from each of these units. Civil engineer Mario Wengert, 32, is the senior coordinator of the construction project and supervises the architects and the various construction companies. He is also responsible for ensuring that all arrangements with the authorities and neighbors work.
“The building site has an excellent location, in the middle of Berlin, directly on the Spree. But the construction site itself is very narrow, the access routes are narrow, so we must coordinate very well,” says Wengert about the challenges of the coming weeks, months and years.
Currently, at the beginning of April 2019, three to four excavators are jetting back and forth on the Charlottenbogen construction site. When they reverse, they beep so piercingly and penetratingly that it resounds far across the river. “This is mandatory occupational health and safety to warn the construction worker who may be standing in a pit with his shovel,” explains Wengert. It must be done, even if he feels sorry for the noise for the neighbors.
These excavators and the construction workers are just doing the excavation. Translated, that means all the earth must go. And now the soil surveyors come into play again. Every kind of contamination, be it oil, heavy metals or other, is packed into individual 500 cubic meter heaps of earth. These in turn are transported by trucks to various disposal facilities throughout Germany. Depending on which of the plants is specialized in which contamination. Before the trucks leave the construction site again, their tires are briefly rinsed with water so that they do not spread the dirt from the construction site in the streets of the neighborhood.
The ground is sloping towards the river. Therefore, the earth is not dug out to the same depth in all places. At the beginning of the construction site it even goes down 3.5 meters. The closer they get to the riverbank, the lower the excavation will be, in the end even only one meter. Once everything is smooth and straight, they will start the shell construction in mid-June 2019.
But even then, there will be a lot to coordinate for Mario Wengert. After all, the groundwater table is an issue, because it is very high in Berlin in general, and even near the river. To prevent the building from simply sinking or sinking again, they will have to drill a concrete pile up to 12 meters deep into the ground every 2.5 meters.
How does that work exactly? More on that when the time comes.