Sixth Street Viaduct

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The Sixth Street Viaduct (designated as City of Los Angeles Bridge No. 53C-1880 and California Department of Transportation [Caltrans] Bridge No. 53-0595)[1] is an elevated four lane road that leads to downtown Los Angeles. Built in 1932, it spans 3,500 feet (1070 m) and has a roadway 46 feet (14 m) wide, with sidewalks on either side. The viaduct is composed of three independent structures: the reinforced concrete west portion, the central steel arch section over the Los Angeles River, and the reinforced concrete east portion.

It is also known as Whittier Boulevard as it intersects South Boyle Avenue, a residential street. The road becomes elevated as it rises over the Santa Ana Freeway going east, and it is still referred to as Whittier Blvd. When the road goes over the LA river, it becomes Sixth Street East, and it goes back to ground level and intersects at Mateo Street, an industrial street in an area of warehouses.

It is an iconic bridge with its concrete columns, bent caps, girders, and abutments and carries traffic over the Los Angeles River, the Santa Ana Freeway, several railroad tracks, and surface streets.

In 1986, the Caltrans’ bridge survey found the 6th Street Viaduct eligible for inclusion in the National Register of Historic Places. [2]

It is also an extremely popular filming location.

[edit] Degradation

During the construction of the viaduct, an on-site plant was used to supply the concrete for construction. However, the quality of the concrete turned out to have a high alkali content and lead to an Alkali-Silica Reaction which creates cracks in the concrete and saps the strength of the structure.

Current estimates are that the viaduct has a 70% probability of collapse due to a major earthquake within 50 years. [3]

It is one of the only historic LA River bridges to suffer from ASR.