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Come, let’s go swimming

Come, let’s go swimming
Photo: © Paulina Grebenstein

Paulina Grebenstein has a simple vision: she wants to turn city rivers into bathing rivers, the Spree for example. In order to achieve this the industrial and product designer has come up with something quite original. We wanted to know from her: What does the river of the future look like? To what extent can a sophisticated design help to solve problems of this kind?

Text Boris Messing


On the banks of the Kreuzberg Landwehrkanal the houses nestle close together as if they wanted to warm themselves. A cold and nasty wind is blowing on the Admiralsbrücke, as Paulina Grebenstein strides towards it with buoyancy. In the distance, the Urban Hospital rises out of the fog - as bleak and gloomy as the weather. Grebenstein, dainty, agile, and bright-eyed, has big plans for this place. But she prefers to talk about it in a warmer place, in the Café Isabel just around the corner. The coffee machine hisses a high I and off we go.

Paulina Grebenstein has a pretty clear idea of an urban paradise: no cars in the city center, greenery where possible, and the possibility to bathe in the Spree without getting a rash. In order to come a small step closer to this vision, she has come up with a concept for which she was awarded the Federal Ecodesign Prize in the category "young talent" last year. Her project urban:eden is a design concept for a climate adaptation system for rapidly growing cities. For metropolises like Berlin. Grebenstein's central idea here is to use a sophisticated rainwater management system to relieve the burden on the sewerage system so that rivers are not polluted by it when wastewater overflows into them during heavy rainfall; with the help of filter systems, rainwater is to be stored decentrally and evaporate in hot weather to cool the city.

Shit – Quo vadis?

The 28-year-old Berlinerin with the blonded hair studied four terms of industrial design at the HTW Berlin and afterwards product design at the art college Weißensee, urban:eden was her Bachelor project. The idea came to her after an internship in Taiwan, she says. There she worked for a start-up company that modifies recycled microplastics into various products and textiles. Her original plan was to fish plastic from the sea herself and process it into new products. But Berlin, as we all know, is not located by the sea, so she transferred her idea to the Spree. She asked herself: How can the water quality of the Spree be improved so that you can swim in it? How do you make a city greener and cooler in summer? How do you create an urban Eden? In just four months she created her design concept, which in principle can be applied to any large city. Berlin chose Grebenstein as the basis for her analysis because she knows the city like the back of her hand. Like the Landwehrkanal, for example, which she would like to turn into a bathing resort. But the water quality of the Spree is not suitable for bathing. There are reasons for this, and they are hidden in the city's invisible network of canals.

This is the inventor: Paulina Grebenstein. Above: floating filter system with promenade. Below: street concept with water storage and evaporation. Photos: Paulina Grebenstein (picture 1 and 2)/Melissa Ludkowski (picture 3)

Grebenstein pulls her laptop out of her bag, puts it on the table, takes a sip of coffee and starts lecturing. The Berlin sewer system was designed and built in the middle of the 19th century. The system is based on two types of sewer. The combined sewer system, which for the most part runs within the S-Bahn ring, would channel the sewage from the houses and rainwater into a common sewer, which would then lead all the soup to the nearest sewage treatment plant. The separate sewerage system in the other parts of the city, on the other hand, would discharge rainwater and sewage in separate sewers: the sewage would go to the treatment plant, and the rainwater would be discharged into the river. Although there are more than twice as many dirty water sewers than combined sewers in the Berlin sewer system, measured in kilometers, the latter are the decisive problem. This is because during heavy rainfall, the combined sewer system runs over and into the Spree. The result: germs, bacteria and other pollutants pollute the river and its channels. In the words of Paulina Grebenstein: "Our sewerage system is simply too small, and that's why all the shit flows into the river." However, expanding the sewer system or building larger water reservoirs is costly and technically only partially feasible. 

Shored and sealed

This is where Grebenstein's concept comes into play, which she illustrates with pictures and graphics on her laptop. Floating filter systems, for example on the Landwehrkanal, which are connected to the shore by a footbridge, are intended to clean the water. Microorganisms that feed on the dirt particles in the water would do this, she says. But to prevent too much rainwater from running into the sewer system in the first place, her concept goes one step further: the rainwater should be managed decentrally. The reason why it flows into the sewer system at all is because the city is too sealed to be able to store it in the ground. Grebenstein therefore wants to build green spaces throughout the city to store the rainwater and release it again when it gets hot, thus also providing cooling. Reeds are particularly suitable for this purpose. Greening roofs and facades could also contribute to a cooler environment in the summer months. So-called flood water cycle paths made of drain concrete could store or drain water. The open-pored drain concrete is already frequently used for freeways to prevent aquaplaning.

But how do you finance such a project? Anyone can have good ideas. How do you finance a good idea? And why doesn't something like that exist yet? Grebenstein is working with two environmental engineering companies that are closely linked to the Berlin water distribution companies - and who already carried out a research project on urban rainwater management a few years ago. Many of Grebenstein's ideas coincide with the research results of KURAS of the environmental engineers. But to convince the senate of her vision seems to be a Kafkaesque undertaking. She approached the realization of her project with very naive eyes, summarizes Grebenstein. "At university you have the luxury of being able to dream." A ponderous bureaucracy did not appear in her dreams. She regards the for two decades ongoing pilot project of the Flussbad Berlin, where an 800-meter long section for bathing pleasure is to be built along the Museum Island, as a warning example. In any case, Grebenstein regards the pilot project as nothing more than "symptom relief". She would like to see a complete end to shipping tourism on the Spree and build many such bathing places along with the filter systems she has designed. But who owns the river? From a legal point of view, her concept meets with many hurdles. The river and canals belong to the State Shipping Office and thus to the federal government; the individual sections of the riverbank fall under the jurisdiction of the districts; the streets belong to the state of Berlin. You have to "get an incredible number of people around the table" to reach a consensus, says Grebenstein. And that takes time.

But the young visionary does not let this get her down and is preparing for a longer odyssey. The spirit of the times is on her side after all. For years, scientists have been writing one book after another about sustainable or socially responsible design: Claudia Banz, art historian now at the Berlin Museum of Decorative Arts, speaks of social design, Friedrich von Borries even of survival design. Niko Peach, an economist who is also convinced of the importance of post-growth, calls it post-growth design, which must be the issue today, namely responsible design strategies for the future. Paulina Grebenstein is ultimately only the practical implementation of much-cited theory. However, like so many others, she cannot live on it. That's why she also makes a living from service design and conceptual projects as a freelancer. For example, she is currently working for the cooperative "Am Ostseeplatz" in Prenzlauer Berg on how to green and jointly use the five-meter-wide bridges that connect the houses. Every bud is a small step towards a green city, says Grebenstein smiling With that she empties her cup of coffee.

Category: Innovation & Vision


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