The hard rock drive through the Austrian Alps, at steep gradients of up to 4.8%, was carried out by contractor Marti Tunnelbau, using a 3.83m diameter Herrenknecht hard rock gripper TBM. Best advance rates of 322m in a week and 72m in a single day were recorded by the contractor team, operating on behalf of client Salzburg AG. Rock conditions encountered included phyllite slate, quartzite, limestone mica slate and green slate with carboniferous banded limestone.
About 55% of Austria's electricity needs are met through hydropower generation compared to a global share for this form of electricity of just 16%. The latest improvements at Bärenwerk power plant, which first went into operation in 1924, will increase capacity by almost a third to 15MW, enabling operator Salzburg AG to supply 19,000 households with electricity from environmentally renewable sources.
Construction companies from around the world have now excavated more than 75km of tunnels and shafts for hydropower plants using Herrenknecht technology.
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