The viaduct in the Bietschtal valley was completed in 1913 as a steel construction. A possible enlargement of the Lötschberg route to double track was already taken into account. Therefore the responsible engineers constructed the main arc already for a double track rail system, which was finally realized in 1987. Due to various recalculations and signs of wear particular reinforcement were necessary. Between 1979 and 1987 more than 23’000 dowel screws, 2000 rivets and 150 tons of steel were installed.