Galerie de Choully - Subterranean gallery for the transport of waste water

Countries: France, Switzerland
Border(s): France-Switzerland,
Lake Geneva Council (Conseil du Léman), Greater Geneva,
European programme(s):
Interreg IIIA - France-Switzerland
- Spatial planning and development
- The environment, resources and waste
- Legal instruments
- Public Services
- Watercourses

Lead partner: Communauté de Communes du Pays de Gex

The Association of local authorities of the Pays de Gex and the Canton of Geneva created, in January, 2006, the first Local Grouping of Cross-border Cooperation (GLCT), called "Galerie de Choully", on the French-Swiss border. The objective was to build and to run a subterranean gallery for the transport of waste water connecting French and Swiss sewer systems. Situated completely on the Swiss territory, the construction of the gallery is mainly taken care of the Association of local authorities of the Pays de Gex, by means of the Water agency, of the Region Rhône-Alpes, of Interreg and the General Council of Ain. The operation joins within the framework of the cross-border rivers contract ("Contrat de rivières transfrontalier") of the "Pays de Gex - Leman".


  • Communauté de communes du Pays de Gex (FR)
  • Canton de Genève (CH)
  • Agence de l’eau

Project goals

The objective was to operate a junction between the Swiss and French equipment to build and run a subterranean gallery for the transport of waste water. The project aims at replacing two water-treatment plants that have become obsolete due to the increase of the population and the fast urbanization of the Gessien basin.

Target group(s)

Local population

Project activities

A gallery, 2.7 km long, with an 80 meter depth, was built under the Genevan hillside of Choully between 2006 and 2008. This new equipment transport waste water of the central part of the Pays de Gex to Switzerland. It is then be handled in the water-treatment plant of Bois-de-Bay which has been built on the Genevan side.

Two water-treatment plants, those of Journans and Allondan in Pays de Gex releasing their partially treated waters in a natural environment, has been dismantled. A new purification collector has been  built and connected with the Swiss network through the new subterranean gallery.

Project duration

Depuis janvier 2006

Total cost

15 500 000 €

EU funding

764 000 €