The Røssåga, Norway Hydroelectric Project to initiate a new TBM-era in the country

The return of TBMs in Norway was celebrated with an enthousiastic ceremony in Røssåga, for the initiation of the reconstruction works of the hydroelectric facility in the area. The TMB technology is going to be applied again on Norwegian ground after more than 20years!

The Røssåga hydroelectric stations are located less than 100 km from the Arctic Circle and include Lower Røssåga with six units of 43.5 MW each and a head of 245 metres and Upper Røssåga with three units of 62.5 MW each and a drop of 135 metres. Both stations started producing over 5 decades ago using water from the Lake Røssvatn, which covers 219 km². 

The reconstruction works involve among others, the construction of a 450-m (1,500-ft) access tunnel and 7.40-km (4.6-mile) long headrace tunnel through hard rock. The" Drill & Blast" technique, traditionally applied in Norway was in the end replaced by the 7.3m TBM machine, after the project owner recognized the benefits of the method. 

The TBM is equiped with 19-in. back-loading cutters for excavation through the complex geologic conditions encountered in the area, which consist of limestone, mica schist, mica gneiss, and granitic rock. Also, the machine has a powerful probe drill, with the possibility of a second drill installation, while a high-end Measurement While Drilling (MWD) system offers visualization of probe drill data. Initial rock support during the tunneling process will be performed through two roof drills used for rock bolting and mesh installation, supplemented by the McNally roof support system based on steel slats and shotcrete systems. 

Contractor company LNS expects the tunnel to finish by 2016 and depending on the encountered rock conditions they may used the TBM for the excavation of the 4.30km tailrace tunnel in the facility of Upper Røssåga. According to LNS officials, "more project owners will consider the use of a TBM as interesting, after seeing that we've got the technology back in Norway again. We are already seeing it for upcoming projects in both infrastructure and hydropower. We think TBMs are here to stay in Norway".