The City of Muttenz, Switzerland, commissioned Oppenheim Architecture Europe to design the city’s new municipal water purification plant. The plant is a model of sustainability and extremely sensitive to its contrasting setting near the Rhine riverfront. Nestled between the protected forest and the nearby industrial parks, the project also holds an exhibition and educational area that explains the complex purification process.

The function of the drinking water treatment plant is to create a new landmark for the town of Muttenz and the Basel area. The architecture expresses the unique and state-of-the-art technology held within and emphasizes the importance of the purification process.

The building sits inside a lush green forest next to the river Rhein. This contrasting context - the natural and the industrial - is expressed in the architectural concept. The drinking water purification plant houses a state of the art 3-phased process that ensures the highest quality of water for the citizens of Muttenz. The engineering-driven arrangement of the interior defines the form and the size of the building. Like a tight dress, the skin presses against it and represents the technical inner life to the outside. Pipelines, filters, and apparatuses can be read through the façade abstractly. The result is an expressive building, acting as an ‘objet trouvé’ in its natural context and reduced to its materiality and form.

A public area allows the population to appreciate the complex process transparently and will celebrate water with all senses — a pedagogical spatial narrative guides visitors through the different building areas and process phases. A central open platform serves as a collection area and as a stage for the presentations. This alcove-like room is pure, open to the outside and sits on a pool of water – reflecting the daylight and collecting the rainwater pouring in from the roof. Depending on the time and season, the space can be moist, cold and mystical. Water is experienced throughout all senses.

The surrounding landscape context is playfully implemented into the façade material – soft in expression, crude and hard in its texture. Shotcrete mixed with local clay creates the striking façade and is treated in a way to allow a porous surface. Rainwater flows from the roof over the façade, leaving a patina and allowing moss growth, continuously changing the appearance of the treatment plant. Maintenance work on the façade will be low. The coarse-grained shotcrete will be given a green patina, merging the façade will with its context. The building is in dialogue with the landscape; built with nature, not on top of nature.