Surrounded by workers, Nik Pecci, project safety manager with PMCM Consulting Engineers for the $1.5-billion Gerald Desmond Bridge replacement project—which is revitalizing a 50-year-old link in Long Beach—gestured in several directions: “I’ve got all these [port] tenants here, I’ve got a massive bridge over here. I have to build this thing intertwined with one of the busiest ports in the world. I constantly have commuters, cargo trucks and trailers and trains.”
And that’s just what’s on the surface. The Port of Long Beach had to deal with a world of underground oil-related infrastructure before the design-build team of Shimmick Construction Inc., Spain’s FCC Construction and Italy’s Salini-Impregilo S.p.A. (SFI) could begin in earnest its approximately $650-million contract to build California’s first vehicular cable-stayed bridge.
The underground work—plus a California Dept. of Transportation requirement for more seismic reinforcement—delayed completion by about a year and added about $500 million to the original budget, which was nearly $1 billion.
The project, on course to be finished next year, has finally hit its stride: The 515-ft-tall towers are more than half built and two movable scaffolding systems (MSS), which officials say are in use for the first time in the state, are enabling crews to construct cast-in-place approach segments without falsework.
Work began in 2013 on the replacement for the through-truss span that connects Interstate 710 to the port’s Terminal Island over a channel. The new bridge, parallel to the old one, will have a 205-ft vertical clearance, making it high enough to accommodate the newest generation of cargo ships— supersized vessels that can carry up to 9,000 containers. It will also be the tallest of its kind in the U.S., say project officials.
About 85,000 vehicles use the old bridge on a daily basis. It has a total of five lanes with no shoulders, steep approach grades of up to 6% and a 155-ft underclearance. Moreover, spalling concrete prompted the installation of catch netting under the bridge deck.
The 8,400-ft-long replacement, with a 2,000-ft main span, will have three lanes in each direction, shoulders and a bike path. It has a 100-year design life, says Al Moro, project executive with the port.
Despite a federal government designation as a project of national significance, the project had to wait for funding until voters passed Proposition 1B in 2006. Various state agencies also pitched in with funding. In 2010, the California Transportation Commission approved the replacement project. That action launched a search for a design-build contractor.
The bridge, which crosses the Back Channel to Terminal Island, carries 15% of all container cargo traveling through the U.S. that arrives by water. Funding comes from multiple sources, including $500 million from state highway and transportation bond funds; $300 million from the federal government; $114 million from the port; and $28 million from the Los Angeles County Metropolitan Transportation Authority.
“Given the rise in cost of the project, we are working with our federal, state and local transportation agency partners and elected officials to discuss additional transportation funding sources,” says Lee Peterson, a port spokesman.
Port engineers discovered a problem they needed to literally unearth—scores of abandoned oil wells from extractions dating back to the 1930s. SFI’s test excavations also revealed geological conditions that vary so much that each bridge foundation requires its own design (ENR 10/21/13 p. 14).
The job calls for about 300 cast-in-drilled-hole piles to depths of 110 ft to 180 ft. Besides liquefiable soils and a high water table, the project sits in a seismic zone, says Moro. Lateral movement is a design consideration for the piles and reinforced-concrete main towers.
Moreover, numerous utilities—including a 600-ft-long network of transmission and telecommunication lines—stretched beneath the old bridge from a power plant to a substation, says Wayne D. Smith, the port’s senior civil engineer. That line was replaced by a new two-mile-long system, which was realigned.
“We could not release the site to SFI until we resolved the significant amount of utilities in conflict with the proposed construction,” says Smith. “SFI could not and would not perform construction near a 66-kv line. We had to protect it or relocate it.”
Moreover, SFI tweaked its design to accommodate some utilities, says Matt Carter, principal with Arup, the team’s designer. For example, “there was a sewer pipe fairly deep down beneath the end bents. [The port] asked us if we could design a bigger pile cap to span across the pipe.” Doing so eliminated the cost of removing and treating contaminated earth.
The conflicts weren’t just below the surface. Overhead systems had to be relocated out of the way of the higher elevation of the new bridge. “We made a collective effort working with [Southern California Edison] planners to say we don’t always need to go A to B to C and incur extra costs,” says the port’s Moro.
The agencies looked for redundancies that would allow some lines to be removed, and ways to re-route others, while not disrupting the needs of the bustling terminals at the second-largest port in the U.S.
Port crews had to locate all the abandoned wells and address which ones would interfere with the new bridge alignment. “Some were abandoned years and years ago when records were poor and protocols were crude,” the port’s Smith says.
Surveyors did identify locations some time ago, but earth movement made it challenging to locate the wells. “They had to be cleared before SFI got out there with heavy equipment,” Smith says.
That led to another joint effort, this time with the Long Beach Dept. of Gas and Oil. “We sat down and created oil set-aside areas,” says Moro. “We said, ‘Here’s our master plan. What works for you?’”
After extensive discussion with the California Dept. of Transportation, the port determined that a 50-ft separation between the top of any abandoned well and the new bridge substructure was necessary to prevent any potential influence of a leaky casing, says Smith.
After an interfering well was located, crews used a hollow drill to get down around the well, along with a clamshell excavator. “Once we contacted the well, we cut the casing down to the elevation we wanted,” says Smith. “We entered the casing and set 10-ft plugs at intervals.”
Crews treated 24 abandoned deep wells. They then had to deal with all the infrastructure that allows the current oil well system to work—including injection lines that carry seawater used to fill aquifers in order to treat land subsidence from old ways of extraction.
“There are water lines, collector lines from active wells to holding tanks that we had to relocate,” says Moro. “We spent quite a bit of time; it was a big part of the project.”
Onward and Upward
Almost all of the projects’s 351 piles, through dense sand and silt, are in place, as are 58 out of 77 pile caps, says Smith. The pile caps for the two main-span towers are 8 ft in diameter. They each contain 3,400 cu yd of concrete, says Butch Anderson, SFI superintendent.
The columns, spaced at 200 ft, are designed to bear the weight of each of the movable scaffolding system machines that are helping construct 2,800 ft of western approach spans and 3,600 ft of eastern approach spans. That weight totals about 5,000 tons—when combined with the cast-in-place concrete and rebar, says Smith. Project officials believe this is the first use of MSS in California.
The self-launching MSS machines have the “advantage of segmental construction where each span can be completed independently,” says Bill Corn, SFI project director. The MSS launches itself out 12 ft on either side. After a segment is cast, it moves to the next column and repeats the process.
The MSS consists of brackets, attached to the columns, to support the main girders. Transverse trusses are connected to the main girder and used to support the soffit. The final elements are the exterior concrete forms for the girder and overhang.
With the MSS, which eliminates falsework, crews can complete 200 ft of deck each month. With falsework, it would take six months, says Smith.
Also, the MSS provides safer working access for labor, equipment and material, while not obstructing access below the structure, adds Corn.
The systems, which cost about $12 million, weigh 1,500 tons each when empty, says Bob Schraeder, Shimmick’s director of design-build. “When we bid the job, we evaluated various types of structures for the approaches,” he adds. A precast option would have required more access underneath the bridge, he says. In the crowded site, hemmed in on all sides, that was not possible.
The main span, to be supported by 80 cables, will utilize conventional cantilevered construction of 50-ft-long steel beams topped by precast panels. The new bridge is designed for a seismic event with a 1,000-year return period. “We allowed the roadway deck to slope independently of the towers and columns,” Carter says. “When the ground’s shaking around, the columns shake too, but the deck slopes and relieves a lot of force off the structure.”
Though an independent panel of experts approved the design, the California Dept. of Transportation, which will own and operate the bridge, still asked for modifications. For example, the thickness of the main tower walls was increased by 25%. Moreover, the bridge will be packed with 37,000 tons of rebar.
“We now have a design we are all more comfortable with for the next 100 years,” says Moro.
Port officials are still mulling over multiple options for demolition of different parts of the old bridge, says Smith. For example, “Do we remove the pile caps totally?” he asks. Options include disconnecting the main span at its pivot point, lowering it onto a barge and floating it out. “Or we could disassemble it—remove the deck first, then put it on a traveler. Or remove it in big sections.”
The port hired T.Y. Lin International last summer, under a $7.7-million contract, to provide design support for the demolition. Engineers will present options to the port board this summer. The port’s Peterson says a contract should be let for the demolition in December of next year. The work is expected to take about a year and a half.