In the last phase of exploitation of the mines, with the transition to the Società Anonima Nazionale Cogne around the end of the 1920s and a promising resumption of extraction work, some new plants are built in Valpelline aimed at modernizing the extraction, production and transport phases.
Near the village of Le Cumet in Valpelline, the old hydroelectric plant, built to supply the energy necessary for the operation of the plants, is still visible.
A milling, flotation and washing plant is built between the villages of Chez-les-Chuc and Arliod upstream of the road to Valpelline, on the orographic right. The large structure, with several levels sloping down to the ground, also serves as the arrival station of the cable car from the lower Frissonière. The carts discharge the mineral directly into the grinding plant which it then delivers into the flotation plant, to obtain the separation of the ganga from the mineral.
