The Malleco Viaduct was in its time considered the highest railroad bridge in the worid. It is one of the largest works of metal engineering in Chiie. It was built within the setting of an ambitious state program to extend the railroad network, which President José Manuel Balmaceda deemed fundamental for the economic future of the country.
The work was part of the construction of the railroad line between Angol and Traiguén, made by the Chilean State through a public bidding. The passage through the Malleco River valley presented the main problem for the layout, since the riverbed runs 110 meters below the level of the plains. This difficulty put the engineers in the dilemma of whether to get round it or to overcome it by means of a frontal attack. The latter approach was chosen. The bridge wouid be laid out over the Collipulli narrow defile.
In 1885, the Chilean government put its ambassador in France, Alberto Blest Gana, in charge of contacting the best renowned European firms and ask their advice for the construction of the viaduct, according to the designs made by the Chilean chief engineer of the Arauco railroad, Victorino Aurelio Lastarria. Three French companies presented projects: Gustave Eiffei, the Societé Anonyme des Anciens Establissements Cail, and Schneider et Cie. O Le Creusot. The work was awarded to the latter.
Between 1886 and 1888, the firm built in its workshops in Europe the ~ron frameworks, which were transported to its destination first by ship and then by railroad. The foundations were gradually ready, and the viaduct was completed between February 1889 and the middie of the following year. The work was formally opened by President José Manuel Balmaceda, the 26th. of October of 1890.
The total weight of the viaduct, measured section by section at the workshops, amounted to 1.401.344 kilograms. The bridge was assembled on a large 95 meters long wood platform. Each stage of the launching of the bridge over its bases lasted about ten hours, being necessary to increase the number of workers up to a hundred as the work progressed. Once the bridge was laid out, temporary resting on hydraulic jacks placed on the piers and stirrups (abulments), the assembly of the first headset was finished, and the bridge was lowered to its definitive position by means of the jacks till it rested on the large cast iron supports. In February 1890, the sliding of the beam took place after a very complex operation.
Today, just as yesterday, the work impresses for its magnitude. Its length is of 347.5 meters, divided in five equal sections of 69.5 meters each. The bridge rests on its two end stirrups (abutments) and four intermediate piers, all of them made of steel. The first and fourth piers are 43.7 meters high, the second 67.7, and the third 75.7. The rails are at a height of 102 meters above the bottom of the gorge. Later on, diagonal reinforcements were inserted between the beam and the towers for the structure to bear the weight of more modern locomotives. The viaduct can be fully appreciated from the bridge for vehicles that was built parallel to it.