In Viaduct Design Competition, A Remake Is Poised To Trump The Original

The 6^th Street Viaduct in Los Angeles is not the city’s best-known icon. But it’s been featured in as many movies and TV shows as City Hall, the Hollywood Sign, and Capitol Records. Spanning the Los Angeles River, two sets of railroad tracks, a warren of warehouses and light industry, and the 101 and 5 freeways, the 3,500-foot-long viaduct east of downtown has presided over dozens of key scenes, if only as a backdrop and not a focal point. Scrambling over the concrete walls of the mostly-dry riverbed, car chases in Grease, and Repo Man passed under it. Music videos for INXS, Kanye West and Limp Bizkit have included it. (A surprising and glaring omission: the viaduct is not featured in the video for “Under the Bridge,” the Red Hot Chili Peppers’ paean to the City of Angels and heroin addiction).

If the 6^th St Viaduct has historically been a recurring bit player in the city’s cinematic history, three teams of architects now vie to turn the structure into a much more significant participant in the life of the city, and something much more than a bridge. Like a rarely seen but influential film from generations ago, the 6^th St. Viaduct is set to be replaced and rebooted with a spectacular remake.

Cracked Actor

The bridge is one of 14 built between 1909 and 1934 on the stretch of the Los Angeles River closest to downtown. Though their styles vary from Beaux-Arts to Italianate to Art-Deco, all are built of reinforced concrete. The 1932 6^th Street bridge is unique in that it is has a double steel arch span over the river itself, and more importantly, is the only one of the group to have sourced rock for its mixing plant from a different quarry. This turned out to be a fatal choice: the bridge has alkali-silica reaction (ASR) syndrome, or “concrete cancer,” a chemical reaction that creates cracks in the concrete and increases the risk of collapse in a major earthquake to unacceptable levels. Despite its eligibility to be included on the National Register of Historic Places, and numerous attempts at fixing the problem, the Los Angeles Bureau of Engineering determined that the bridge would ultimately have to be replaced for safety’s sake.

An Ambitious Plan

In an unusual and refreshing development, the authorities have elected to capitalize on the opportunity of replacing the bridge to create an asset that will form the basis of urban revitalization, serve multiple modes, and become a centerpiece of civic life. The City has assembled a Design Aesthetic Advisory Committee (DAAC) comprised of academics, architects, community and business leaders, including Eric Owen Moss, director of the Southern California Institute of Architects (SCI-ARC) and Lewis MacAdamas, the president of Friends of the Los Angeles River (FoLAR)downtown. The DAAC will submit its recommendation to the Bureau of Engineering, which has final say.

At MacAdams’ behest, an international design competition was held, and three finalists emerged, each led by a global architecture-engineering firm: AECOM, HNTB and Parsons Brinckerhoff (P-B). The city will select a designer in October and the design is to be completed by summer 2014, with construction concluding by the end of 2018. The finalists presented their designs at a series of community meetings in mid-September.

The City is clearly concerned with the potential of the bridge to become a catalyst for development and a multi-modal piece of connective tissue between the on-the-make Arts District and the historic, densely populated Latino neighborhood of Boyle Heights. Specific design responses to this challenge varied widely among the three teams.

“Here is Your New Landmark”

The AECOM team, which reminded us that its lead firm is the “only Fortune 500 corporation headquartered in downtown Los Angeles,” packs perhaps the strongest resume of prior bridge experience, having designed more than 40 sizable spans throughout the world, from Sutong, China to Lisbon, Portugal. Closer to home, AECOM led the joint-venture construction team for the Metro Gold Line East Side Extension, and is materially involved with at least nine projects in a five-mile radius of the bridge. These include the Metro Regional Connector subway project, the development of a Clean-Tech Corridor for environmentally progressive businesses (which the viaduct itself will pass over), and Park 101, a proposal to bridge the 101 Freeway with a new park connecting the historic Pueblo de Los Angeles area and Chinatown with downtown.

Despite all these credentials, the AECOM proposal seemed the least graceful and appropriate. The central concept of the main river span is a flared pylon representing an abstraction of an angel’s wings, from which cable stays would extend to support the the bridge. The proposal does include some tidy gestures, such as a stairless, universal design approach to a suspended pedestrian ramp beneath the bridge, and the elimination of light standards along the deck in favor of isolating lighting within the tower itself and within the pedestrian handrails. The pedestrian walks are separated from roadways by a planted verge. But the overall effect of the iconic central span is ungainly, largely due to the thickness of the decking, which seems overbuilt for the relatively short spans and low clearances required. The technique of creating a strong truss effect through shallow cable stays is called “extradosing,” and here it seems particularly apropos.

Despite being inspired by the “City of Angels,” there is something about the imposing design of the tower that is reminiscent of the brobdingnagian ambitions of authoritarian despots in Asia or the Middle East, for whom AECOM has designed some fairly spectacular bridges in the past. The gold plating of the towers in the renderings seems more characteristic of a nouveau riche sultanate than a connector between working-class and artistically avant-garde neighborhoods in a major U.S. city. It’s as if someone in Seoul was asked to design a bridge based on his experience of Los Angeles as a themed casino replica in Macau.

AECOM’s presentation was also an odd mix of self-assurance and insecurity. The massive corporation with hometown roots advertised that 75 percent of the design work would take place in Los Angeles, and rolled out its community outreach team, which promised to engage with the citizenry using every means available, including going “door to door with old-fashioned shoe leather,” according to outreach leader Kermin Mattucks.

The delivery was alternately grandiose – “Here is your new landmark!” – and withholding – “what you see is what you get.” For its initial design, the AECOM team declined to build ramps down to the edges of the river, which is slated for a substantial de-channelization project and revitalization master plan that will bring occupiable park space to the water’s edge, because currently, “there is nothing to go down to.”

The presenters stressed that everything shown in the renderings was included within the bridge’s $190 million construction budget, implying that other proposals might be doing some wishful thinking. The total project budget, including demolition of the current bridge, is $401 million.

The “High Line” Effect

Recent urban history has shown that wishful thinking does have a way of turning into willful creation, when all the right ingredients – chief among them monetary and leadership commitments – are in place. As the viaduct is situated in a gritty but tentatively resurgent area of Los Angeles, it’s clear that the city fathers, business leaders and designers alike are hoping that 6^th Street Viaduct Version 2.0 will have the transformative effect of New York’s High Line, where a derelict elevated rail line has been turned into a linear park, festooned with native plantings, street furniture, food vendors, and most importantly, new real-estate development. Nowhere was the hoped-for “High Line effect” in as much evidence as the HNTB team proposal, which showed people walking along some rusted rail tracks and highly familiar-looking paving blocks, between cafes and open shop windows revealing artisans spot-welding their creations.

Kansas City-based HNTB augmented its considerable bridge experience, including the “Big Dig” cable-stayed Leonard Zakim Bunker Hill Memorial Bridge in Boston, the second Tacoma Narrows span and the Delaware Memorial Bridge, with an exemplary array of international and local firepower. Dissing + Weitling, a Danish firm responsible for many of Scandinavia’s overseas crossings, brings structural economy and simplicity to the design. A.C. Martin is the architect of City Hall, the Department of Water and Power building, the May Department Store (now LACMA’s administration building) and more recently, the Hollenbeck Police Station. Michael Maltzan has impeccable instincts for urban regeneration and arts projects, including the Inner City Arts campus, the New Carver Apartments affordable housing project, a serrated circular building in the crook of the I-10 / 110 interchange, and a large-scale urban plan for the re-use of the Union Pacific Mission Yards, just across the river from downtown. The team also includes San Francisco-based urban planners and landscape architects Hargreaves Associates, whose credits include the Sydney 2000 Olympics and the 2012 London Olympic Park. Not surprisingly, the ground plane across the entire length of the bridge is highly programmed and developed.

The HNTB team had what appeared to be the most fully developed and visually exciting proposal. Its graphical style and narratives revealed Maltzan’s hand.

“Infrastructure is part of our iconography,” Maltzan says. “But it stopped being as productive as it once was. Too often, it divides the city. We’d rather capture what it means to the city.”

Combining a nod to the current bridge’s arch structure and the City’s desire for a cable-stayed span, HNTB’s scheme consists of a series of ultra-thin decks suspended by cable from pre-stressed concrete arches. The arches bow out laterally from the roadway and take broad leaps over the rail lines, then duck under the high-tension wires on both sides of the river. Like the other schemes, HNTB suspends a walkway below the vehicular deck, but instead of dangling via steel rods, the walkway is a smooth inverted reflection of the main concrete arch above. The tops of some arches would be climbable via stairs.

Also different is the scheme’s elimination of a center pier in the water, and its devotion of the longest and highest arches to passages over active rail and road lines. The balanced arches on either side of the river unite the utilitarian rail lines, future riparian eastern banks, and pedestrian activity on both sides, and are intended “to show this is not just a bridge over the river,” Maltzan says.

This move partly has to do with complex seismic calculations and the desire for a thin, diaphanous deck. But the team also intends to create what Maltzan calls “urban rooms” and “grand halls” beneath the bridge, which renderings show as venues for gatherings and painted and projected murals.

The scheme reveals a total commitment to the parabolic arch shape – the ADA-accessible ramp is a double loop in plan, concrete paving patterns echo the arches above, and holes in the deck and the arch itself are stretched ovals.

The gentle curve of the bridge – a design requirement of the project brief – in this scheme shifts the arches slightly out of plane, affording unique tessellations of light and shadow on members that are largely (and cost-effectively) identical.

Of Allées, Ramblas and Nests

In many ways the Parsons-Brinckerhoff (P-B) scheme splits the difference between the other two proposals. Its center span is a steel double arch with a mid-river pier, like its predecessor, but it uses a wing- or harp-like symmetry of cables and arches for its “angelic” gesture.

While the overland spans are not visually stunning as HNTB’s, they are relatively unobtrusive and neatly accommodate pedestrians in the center, rather than at the edges, creating more opportunities for interaction between people moving in both directions. The pedestrian right-of-way is dotted with ramps and inclines that parry with the road deck, splitting to dip below for the “nest” observatory and rising slightly above the road in the main span. Numerous shelters and segmented colored decking break up the monotony.

As did the HNTB team, P-B pulls together a well established transportation engineering giant with several design architects. P-B is the main consultant for the nearly $100 billion California High-Speed Rail project, the new Hoover Dam bridge, Florida’s Sunshine Skyway, and is the offspring of the firm responsible for the first New York City subway, where it continues to work on the Second Avenue Subway. The lead design architect is Ricardo Rabines, one half of the Safdie-Rabines partnership out of San Diego, which designed the Baldwin Hills Scenic Overlook south of Culver City and several expressive pedestrian bridges in California. Wilkinson Eyre joins from the UK, where it designed the reconfigured Channel Tunnel Rail Link’s 100-plus bridges, as well as numerous other spans in the UK and Europe.

P-B’s approach is to create an “iconic destination, place for celebration and a new spark for economic development,” says project manager Juan Murillo. The bridge should also be seen as a “vertical and horizontal connection,” says Rabines, who says the main span’s shape is based on the spread wings of an egret. Fundamentally, Rabines views the project as a “place for people,” not just a thoroughfare for cars to bypass obstructions.

The plan emphasizes living streets with bioswales, proposes semi-permanent shipping-container modules for a “Clean-Tech Allée” beneath the viaduct, and a network of active streets and parks radiating from the project. Characterizing the paseo as a series of “ramblas,” as the avenues of Barcelona that turn into pedestrian parade grounds are called, Rabines asserts that the viaduct will become a place for celebrations, and noted that his team’s budget includes changes of color for the lighting to commemorate holidays. Wisely, the P-B presentation included a slide that implied the vision would not be fully realized until 2040.

From Skid Row to Sky Park?

Given the area’s grit and the potentially long stretches of isolated walkway, security was a top concern at a SCI-ARC Q & A earlier this month. The AECOM team responded that its unique lighting scheme could be augmented by security cameras and call boxes if needed. P-B referred to its wide walkway design and ample sightlines, with Rabines adding, “Security is all of our responsibility.” On behalf of HNTB, Maltzan responded, “It’s not so much about mechanical safety. Having worked in Skid Row, I can say that if the bridge is successful, if it is used intensely and there are people around, it will be much safer than if it is void of activity.”

Los Angeles has shown too-little-seen forethought by capitalizing on the need to replace a piece of failing infrastructure by advocating for a true civic asset that will figure into larger plans for the region, including turning the Los Angeles River into a true waterfront, not just a concrete ditch. For areas of the city that have been sliced and scarred by “critical infrastructure” for the better part of 100 years, a green vein running along and intersecting with neighborhood revitalization efforts will hopefully have some catalytic effect. Architects often believe that their designs will have impacts on the human condition that extend far beyond the borders of the project. But just because something gets built doesn’t mean people will come. In this case, even a truly iconic and beloved bridge might end up being just that, if other economic and civic forces well out of the architects’ realm are not brought to bear with the same level of intent and support as the design and construction work. Still, it’s tempting to think about what new roles the rebooted Sixth Street Viaduct might play in the coming decades. It may just be the case that the remake outshines the original.

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