Line 9 is a part of the Barcelona Metronetwork that is currently under construction, with five stations open in the Santa Coloma de Gramenet suburb since December 2009. Upon completion, it will be the longest automatic metro line in Europe.
The total system will have a length of 29 mi (47.8 km), 27 mi (43.71 km) underground and 3 mi (4.09 km) of viaducts. L9 will be the deepest line in the Barcelona network.
The project consists of the extension of the Barcelona Metro L9 Viaduct over the “Pratenc” Industrial Park. The structure crosses the ancient Llobregat riverbed, an area that is under deep transformation and is related with the Barcelona Port railway links.
The viaduct is about 3000 ft (914 m) long, composed of different structural types, according to the clearance demands of the Port Authority. The first stretch follows the structural layout of the existing one, with 80 ft (24 m) long precast concrete beams. In order to cross the ancient riverbed of the Llobregat River, an extradosed 220 ft (67 m) maximum span bridge was designed, with a total length of 1300 ft (396 m). The rest of the viaduct consists of a sequence of simply-supported precast beams.
The deck has been designed as a succession of simply supported spans 108 ft (33 m) long to minimize interferences with existing utilities and the heavy traffic in the industrial area. Economy has been a major requirement governing the design that has been combined with the aesthetic criteria defined by the architects of the Municipality of Barcelona.