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Tender description :
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Tenders are invited for: Vissoie-niouc gallery The project consists of building a new gallery loaded with load of 8 km between the vissoie compensation basin and the departure of the penstock in niouc for the vissoie-chippis level, of the chain of development of the driving forces of the gougra sa.
the majority of the route of the driven gallery (internal diameter 3.6 m) will be excavated with a tunnel boring machine (7705 ml) and the rest by conventional method in the soft ground (176 ml) and in the rock mass (70 ml) using screws. the project also includes the creation of an access gallery (600 ml) to niouc using the conventional method in the rock massif, the future balance chimney. the driven gallery excavated with a tunnel boring machine is lined with prefabricated reinforced concrete elements (voussoirs). the transport of excavation materials is planned by trucks.
In addition, the project includes the termination of a new water intake in the dike of the Vissoie basin as well as the installation of a new penstock (120 ml) connecting the driven gallery and the existing penstock to the navizence power plant.
To carry out the work, four installation sites are planned: three in the Niouc sector (balance chimney portal, pickling gallery portal and storage space) and one in the Vissoie sector (portal to the water intake).
approximately 400,000 TB (or 150,000 m3) in place of materials are produced during the execution of the project. the main quantities of excavation materials for the tunnel boring machine of the gallery between niouc and vissoie will be managed from the niouc site. the contractor will transport the sailor to places of his choice, where he will be recovered or put in a final landfill depending on his lithology.
a detailed description of the work to be carried out is given in chapter 137 of the special conditions. Submission of tender: 03/20/2026, 12:00
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