The Sixth Street Viaduct was built in 1932. Spanning nearly 3,500 ft (1,067 m), it connects the Arts District on the west side of the Los Angeles River with Boyle Heights on the east side. According to the Sixth Street Viaduct Replacement Project (SSVRP), however, the structure began deteriorating just 20 years after its construction as a result of a chemical reaction in the cement known as Alkali Silica Reaction.
Various restorative methods are said to have been tried over the years without success. As a result, the bridge's lack of structural strength, coupled with a high vulnerability to failure in the event of a major earthquake, led to the decision to rebuild it. The US$449 million project is said to be LA's biggest ever bridge project.
In 2012, an international design competition was run to select a design for the new bridge. The four-month process saw a design by HNTB and Michael Maltzan Architecture chosen. It features ten pairs of white concrete arches with varying heights and angled outward nine degrees, which the SSVRP says is an industry first. The deck of the bridge is cradled between the pairs of arches and supported by cables.
The new Sixth Street Viaduct will boast wider sidewalks, dedicated bicycle lanes and dedicated pedestrian and bicycle ramps on either side. Large open areas will be created below the bridge, which will be made into recreational green spaces and a new rail station nearby has also been proposed.
The new Sixth Street Viaduct is expected to be completed by 2019 and to be in use for 100 years.
The video below provides an insight into the project.