For the extension of the Grésillons 2 sewage plant, Bouygues Travaux Publics was in charge of earthworks, civil works for the plant and buildings, roads and pavements, secondary works and landscaping. With the completion of phase 2, the plant capacity was multiplied by 3 to 300,000 m3 per day (of 1.5 to 2 million population equivalent).
In addition, Bouygues Travaux Publics, which had already built phase 1, provided assistance for operation.
The works comprise:
- construction of a dozen buildings (civil works), including wet and dry zones,
- construction of seven circular concrete tanks,
- pipeworks with diameters from 500 to 2800 mm linking the buildings,
- modification of existing offices and administrative buildings.