From its experimental lightweight aggregate concrete to its role as California’s first toll plaza that allows commuters to pass through without slowing down, the new Benicia-Martinez is way ahead of its time.
Unfortunately, the new Interstate 680 crossing over the Carquinez Strait also is way behind its schedule and way over its budget.
In 1999, Caltrans predicted the $385 million project would be open to traffic by June 2003. The new estimate is $1.2 billion and Caltrans expects completion by fall 2007.
The bridge is now complete structurally, with a summer worth of deck and finish work ahead. The five-lane toll bridge is more than 82-ft. (24 m) wide and crosses the Carquinez Strait between the City of Benicia in Solano County and the city of Martinez in Contra Costa County.
The view from the new 8,790-ft. (2,679 m) long bridge consists of an oil refinery, strip malls and a ghostly flotilla of decommissioned massive World War II Navy ships. In addition, the bridge has a view that includes the existing span and a cast iron 1929 Union Pacific Railroad bridge.
The new box girder bridge was composed of 335 concrete segments. The segments were cast in place individually using VSL travelers.
Four sets of the giant, paired robotic VSL travelers worked the job. Two VSL travelers started on opposite sides of the pier table and cast cantilevered segments with each moving outward away from each other.
The concrete boxes were linked together like Legos pieces and were supported by pier columns. Caltrans workers can go into the bridge’s guts — where the ceiling is between 15 and 40 ft. (4.5 and 12 m) high— to do maintenance because the decks were thicker at the base of the bridge and thinned out over the open water.
With room for light rail on the west side, Benicia-Martinez was built with SLC, steel hinges and deep foundations to help withstand a 2,000 year frequency earthquake.
The bridge would allow for all southbound traffic to be handled by the old bridge, where a two-way bike lane is being added. A nearby 23-acre (9.3 ha) tidal marsh also has been restored.
The Benicia-Martinez Bridge innovations brought national recognition in engineering, scholarly and construction journals.
However, the Oakland Tribune reported failure by the Golden State’s transportation agency to construct scale models prior to construction and several agencies faulted Caltrans.
Unexpected engineering and environmental challenges provided more problems during construction. Kiewit Pacific, the general contractor, and Caltrans attempted to solve those challenges at a high cost to taxpayers.
CH2M Hill and T.Y. Lin International designed the bridge. Parsons Engineering was the construction engineer and Steel Deck Institute, SDI was the post-tensioning supplier.
Problems emerged early in the project. For instance, the bridge site had to be moved from the plans. Then, when the drilling into the bedrock started, contractors found that the rock was too crumbly and holes collapsed in some places.
“The material caved in as we drilled thus rendering the drill useless,” said Keith Wayne, public information officer of Caltrans.
Concrete was poured into oversized holes, which was then drilled and piles set.
“We changed methods using the rotator,” Wayne said. “This machine rotates a steel shell slightly smaller in diameter than the pile itself with teeth on the leading end all the way to the tip of the rock socket. Then the rock socket can be excavated while being protected by the steel shell. Once excavated, the rebar and concrete are placed while the shell is extracted by the rotator, thus leaving the concrete pile [rock socket] in place. To our knowledge this had never been done before in open water.”
The bridge was set on 17 piers, 12 in the waters of the Bay, which consist primarily of 61,200 cu. yds. (46,790 cu m) of concrete. These piers were placed on 130 steel piles, 8 ft. (2.4 m) in diameter sunk 250 ft. (76 m) into the bedrock.
Wayne indicated that fixing the crumbling bedrock was much harder than expected. Machines used to bang into those rocks created sound waves; that noise killed migratory fish- including endangered Delta Smelt and Chinook and Coho salmon. According to published reports, pile driving caused the internal organs of the fish to rupture in large numbers.
The solution was to use air curtains. This technique had been used by the military to deflect prop noise from ships and submarines, which injured whales and other sea mammals. The idea was borrowed from the most expensive bridge project in California history — the new Bay Bridge.
“We worked with the contractor to build ’Bubble Trees’ that would surround the pile during the driving of it, the ’Bubble Trees’ were hooked to very large air compressors that literally boiled the water about 3 feet high around the pile,” Wayne said.
The team created a 71-ft. (21.6 m) long floating device, a steel backbone beam with smaller ribs. This covered the pilings with a steel tube that had foam and air bubbles shielding the fish from the noise and resulting damage. Dubbed the “Jacuzzi effect,” this technique added nearly $165 million to the project cost.
The innovated technique went hand-in-hand with cost overruns.
In December 2005, a state auditor’s report criticized Caltrans for failing to foresee cost problems. State lawmakers formed an oversight committee comprised of Caltrans and two local transportation commissions, to avoid multimillion dollar surprises.
Caltrans’ most innovative, costly and problematic effort was its use of pre-stressed CIP segmental cantilever sand lightweight concrete. The innovation consisted of using concrete that was made with rotary kiln expanded shale, clay or slate to create more earthquake-safe piers. Several trade journals heralded the bold move.
The American Segmental Bridge Institute called the new Benicia Bridge the largest bridge ever to use the lightweight concrete.
The new bridge is said to be the state’s first major lightweight aggregate concrete bridge since the completion of the Parrot’s Ferry Bridge near Vallecito, Calif. That bridge, completed in 1979, experienced a large mid-span deflection after approximately 12 years of service, according to a UC Davis study. The large mid-span deflection affected the general appearance of the bridge as well as the sight distance of vehicles traveling on the bridge. The report raised concerns regarding the bridge’s structural integrity.
In addition, the study revealed that the unexpected time-dependent deformation of the bridge “hampered the general acceptance of lightweight aggregate concrete as a suitable structural material for long-span bridge construction in California for many years.”
To compensate, Caltrans implemented an extensive process to study the concrete and required a 10,000-psi (690 bar) compressed strength. One report said 100 formulas were tested.
It was the simplicity and cost effectiveness of the original bridge plans that specified oversized segmental box girders, necessitating lightweight concrete because of the length of the roadway on each massive cast-in place segment. Regular concrete would have been too heavy.
But the lightweight concrete was temperamental, especially in the area of temperature.
A Bechtel investigation found that the fast setting, high strength concrete got very hot and dry during placement, creating problems with temperature control and pumping that could lead to cracking. The mix had to be cooled to near freezing, using ice and liquid nitrogen, all while shutting mixers onto barges for pours.
The contract specified that concrete be kept below 160 F (71 C) but the lightweight aggregate was heating up to 195 F (90 C), Wayne said.
“In order to meet the specifications and make sure we had the same high strength concrete we began using ice as a replacement for 30 percent of the water in the mix, the water that was used in the mix was chilled and then the mix was placed into the concrete trucks,” Wayne said.
When the last of the concrete was poured in December, it created the illusion of an impossibly slick, seamless bridge. The additional cost of the cooling was more than $100 million. Caltrans officials said the cooling work was outside the scope of the contract and thus the responsibility of the state to foot the bill and not the contractor.
Another cost overrun came because progress had moved beyond the original bid specifications. A toll plaza, was built and now is being partly torn down to create the Bay Area debut of open-road tolling. The area would allow vehicles equipped with FasTrak electronic toll tags to bypass the toll booths altogether and cross the span without slowing down.
To make way for the installation of open-road tolling equipment, the Bay Area Toll Authority is currently demolishing a portion of the toll plaza on the Martinez side of the new bridge. Demolition and reconstruction work will be completed in time for the opening of the new bridge fall or winter 2007.
“When the new bridge and the toll plaza were designed back in the 1990s, FasTrak was still in its infancy and open-road tolling was not a consideration,” Rod McMillan, the Bay Area Transportation Agency’s director of Bridge Oversight and Operations, said. “Now FasTrak use is skyrocketing. And if open-road tolling proves to be as popular as we expect, we could end up someday doing partial demolitions of toll plazas all around the Bay Area.”
Equipment used in the project included a massive barge.
Kiewit designed and built the floating pontoon, with two 200-ft. (60.9 m) long barges supporting the work in the water on a gang tree, according to Ron Rattai of Kiewit Pacific.
The bridge project saw one death, of painter Bill Calloway on April 7, 2004, Calloway climbed down from a painting scaffold and reached to hold onto a pipe. He lost his grip, tumbling backwards, then falling 130 ft. to the base of the concrete pier below. An OSHA investigation resulted in a $25,000 fine for Caltrans for failing to better require use of harnesses.
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