The work in question covers shaft construction at the Piora portal site, located some 1,847m above sea level. Other works are ongoing.
The Ritom project is an upgrade to the existing facility, which dates from 1920, to improve capacity and turn it into a pumped storage facility. The project will notably require:
- A new pressure tunnel excavated in three sections: upper and lower drill-and-blast tunnels of 150 and 650m respectively, and a 1,500m middle section to be excavated as an inclined tunnel by a 3.23m-diameter gripper TBM
- A new power station equipped with two Pelton turbines each with a capacity of 60 MW
- An equalising reservoir with a capacity of 100,000m3.
Geology consists of Paragneisses and Orthogneisses. Works are due to complete in spring 2022.