6th Street Viaduct - from the LA Riverbed, 2016.01.25.04

6th Street Viaduct - from the LA Riverbed, 2016.01.25.04

The Sixth Street Viaduct: a brief history


Situated in the center of Los Angeles, California, the Sixth Street Viaduct (also known as the Sixth Street Bridge) was constructed in 1932 as part of a group of 10 bridges that cross the Los Angeles River. Under then chief city engineer Merrill Butler’s supervision and his “City Beautiful” movement, the bridges were constructed in the 1920’s and 30’s to all be unique, reflect the cultural history of Los Angeles, incorporate varied themes to resonate those cultures and connect the downtown Los Angeles area with the expanding areas and neighborhoods east of the Los Angeles River.

The Sixth Street Viaduct was designed by Louis Huot and was the most “Streamline Moderne” in design of the 10 bridges - with an Art Deco influence to its structure, lines and architectural embellishments. Comprised of three independent sections - a west side reinforced concrete raised causeway, the central steel arched segment over the river and the east side reinforced concrete raised causeway. The east and west segments of the viaduct were designed with 43 spans along the two outer sections. Each span would be supported by three towering concrete columns varying in height from 30 to 55 feet. The central segment over the river consisted of a central massive concrete pier with an arched opening flanked by two monumental concrete piers, also with arched openings, on both upper banks of the river. These three foundations supported dual, two span continuous asymmetrical steel tied arches, which in turn supported the roadway 61 feet above the Los Angeles River. The viaduct was conceived with the automobile in mind - as LA’s “car culture” was quickly replacing the cable car mass transit system that spanned nearly all of the greater Los Angeles area.


The Sixth Street Viaduct also served as a cultural bridge connecting downtown Los Angeles with the growing European, Asian and Latino immigrant communities of Boyle Heights and its surrounding areas - just east of the LA River. The viaduct spanned multiple railroad lines on both sides of the river, the 101 Freeway (built after its construction) and several local streets. At 3,500 feet in length and 46 feet wide to accommodate two lanes of traffic in both east and west bound directions including sidewalks for pedestrians, the bridge was the longest of the 10 bridges to span the Los Angeles River in the area.

The Los Angeles River was channelized and covered over in concrete in order to control and prevent erosion due to flooding nine years after the viaduct was built in 1932. The monumental structure of the viaduct included a concrete tunnel to the LA River on the west bank and provided easy access to the river’s eventual miles of concrete lined channel. Given this straight-forward access, directly under the bridge, and its close proximity to Hollywood and the Los Angeles film industry it became an ideal location, beginning the early 1950’s, for countless films, television, music videos, video gaming and advertising campaigns. The exposed and easily accessible concrete and structural elements of the bridge also provided temporary encampments for the homeless and the perfect urban graffiti “canvas” - despite continual efforts to cover over the inventive and imaginative tagging efforts of gangs and inner-city artists. Its monumental “Noir” aesthetic, graffiti layered towering support columns and massive steel arches became iconic in films such as Hot Rod Girl, Grease, Point Blank, Repo Man, Terminator 2 and 3, The Dark Knight Rises and Furious 7 - to name merely a few.

In addition to the film industry’s appropriation of the bridge, it’s accessible tunnel to the concrete river channel below the bridge evolved into a popular locus for Los Angeles area car clubs - especially American vintage mid-century “low rider” clubs, whose members would drive their “tricked-out” vehicles down into the concrete river bed for photo shoots directly under the monumental pier and arches.


During construction of the viaduct a state-of-the-art concrete factory was created on site to accommodate the thousands of tons of concrete it would take to build the bridge. Unfortunately, 20 years after the bridge was completed it began showing signs of Alkali-Silica Reaction or ASR - a chemical reaction that causes cured cement to slowly disintegrate when seeping rain water infiltrates it. Eventually ASR creates critical structural instability. A reactive aggregate incorporated into the concrete mix contributed to the elevated alkali content causing the ASR.  Remarkably, the Sixth Street Viaduct was the only one of the 10 bridges built at the time to develop ASR.

Repeated and costly efforts to correct the deterioration issues over many years proved unsuccessful in stopping the continued and irreversible chemical corrosion of the concrete. In 2004, as a result of seismic vulnerability studies, the viaduct was deemed unstable and highly vulnerable to collapse in the event of a major earthquake – which was compounded by safety and geometric design deficiencies. Eventually the significantly failing viaduct would need to be addressed in a more extensive plan than mere patches. Ultimately a decision was outlined in the 6th Street Viaduct Seismic Improvement Project report published in October 2011 by the City of Los Angeles and the California Department of Transportation. The report involved years of research engineering, environmental impact studies, public hearings, multiple considerations as to the viability of alternatives such as reinforcing and retrofitting the existing structure and the necessity to maintain the important transportation corridor between Boyle Heights and the burgeoning Arts District of Downtown Los Angeles.

Despite a 1968 Caltrans survey that deemed the Sixth Street Viaduct as eligible to qualify for the National Registry of Historic Places, its status as a Historic Cultural Monument, and efforts by the Los Angeles Conservancy to protect the bridge, the 2011 report determined and revealed that the Sixth Street Viaduct needed to be demolished and replaced.

In 2012 the Los Angeles City Council approved plans for the Sixth Street Viaduct demolition and the construction of a new viaduct; although a different design than what was outlined in the 2011 report was selected as the final choice to replace the viaduct. The demolition phase began in January 2016 - a complicated engineering project that would take approximately a year to complete. The bridge was closed to traffic in early 2016 and access to the LA River via the famous tunnel that ran under the viaduct was closed in the summer of 2016.

The replacement viaduct is a contemporary design that will echo and modernize the iconic steel arches that crossed the river section of the former viaduct along the entire length of the new bridge. Designed by architect Michael Maltzan and the HNTB Design-Build team, it is scheduled to be completed in 2019. In addition to an expanded and modernized transportation corridor, the new Sixth Street Viaduct will include access to the Los Angeles River, parks, permanent art installations, a soccer field and pedestrian thoroughfares. The design reflects the prevalent revitalizing, progressive development and urbanizing trends of Downtown Los Angeles and the Arts District on the west side of the LA River. But not everyone approves of the new and elegant design.

Change is inevitable.


6th Street Viaduct and vintage low-riders, 2015.11.15.01

6th Street Viaduct and vintage low-riders, 2015.11.15.01