Following a public referendum, the town chose to build a natural swimming pool based on biological water treatment in order to stand out from the conventional swimming pools in the area.
The pool is divided into two sections, one incorporating the actual pool, the other a functional area serving ancillary uses and accommodating the water treatment plant.
The pool is surrounded by aquatic plants and subdivided into a 25m pool with four lanes, a recreational area with a grassy beach section and a waterslide; and a diving pool with a one-metre board and a three-metre platform. The different pool areas are linked with each other by a system of footbridges, ladders and stairs. A disability access lift is included, and there is also a children’s pool furnished with a number of play features.
The biological water treatment basins are embedded cascade-like in the green sloping landscape on the opposite side of the road. This area also offers various, all-season recreational and sports facilities as well as parking facilities for bicycles and cars.
This is strictly a natural pool, using aquatic plants and reeds as a biofilter with the addition of plankton in the regeneration zone, and gravity-fed sand and gravel filtration with a fine-grain substrate. There is no ozone or any other additional disinfection. The water is filtered daily.
The planted shallow waters surrounding the main pool and the 1200sqm external filter basins help to speed up the water heating process.
The pool is geared to nominal load of 1000 visitors per day and maximum load of 2000 visitors per day.
In its first season in 2014, the Riehen Natural Swimming Pool drew an attendance of 42,622 visitors, surpassing expectations and figures of the old facility.
It appears that after only one year in business, the Riehen Natural Swimming Pool is quickly becoming one of the most popular recreational and sports facilities in the area, and in 2015 it played host to 68,400 visitors.
Architects: Herzog & de Meuron
Commissioning: March 2014
Construction costs: €8 million
Client/Operator: Gemeinde Riehen Abteilung Kultur, Freizeit und Sport
Operating costs in 2014: 250,000 €
Contacts: www.naturbadriehen.ch; www.herzogdemeuron.com; www.riehen.ch
Photography: Aerial shot of the site by Christoph Junck, all other photography by Helene Schneider.