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Amazon cathedral

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A diamond-shaped cathedral of concrete and finely tuned steel, the Rio Negro Bridge rises from the Amazon jungle to span one of the world’s largest rivers.

Amassively complex project, the Rio Negro bridge measures 3500 meters (11,482 feet) in total length, and boasts a 400 meter long (1312 feet) cable-supported central section which will allow the Amazon’s significant shipping traffic to pass unimpeded.

When completed, the bridge over Rio Negro will be the second largest cable-stayed bridge over freshwater on the planet, second only to the crossing of the Orinoco in Venezuela at Ciudad Bolivar. The new bridge will reduce the trip from the regional capital, Manaus, to the interior of the Amazon by 30 minutes each way.

Crowning the Bridge

A Country Divided

Brazil is the largest country in South America in land mass and the fifth largest on Earth with a population of 190 million. Brazil has the seventh largest GDP and is, by most accounts, the fastest growing economy. Rich in natural and human resources, this massive land is divided by a complicated system of rivers with the Amazon at its heart, separating its territory into five distinctive regions. Travel in Brazil by anything other than air is difficult, if not nearly impossible, because of its massive river system which divides the country like great walls of water.

The Rio Negro bridge will connect the only urban center in the region, Manaus, across the Rio Negro to the city of Iranduba, which serves as the gateway to the interior of the Amazon, one of the most remote and untouched regions of the world.

Making that connection is costly. Originally projected at $570 million reals (or $359 million USD/Euro 290 million), the government decided to maximize competition for construction by breaking down the bids into stages of construction.

Every stage of the project was separately contracted by the government including primary surveying, pillar construction and insertion, spanning of the pillars with roadway, marine engineering, lighting, and nautical signaling.

The benefit of this plan, of course, is that government funds would be spread more broadly through smaller companies, none of which could take on the entire project alone. The downside, however, is that exact costs could not be predicted over the multi-year project, and particularly in a region where little massive construction had been attempted before.

Taming a River

he Amazon region is well known for its extremes in weather. In Manaus, the tropical monsoon climate means torrential rains which create huge floods that annually inundate the surrounding areas: factors which hinder mobility, especially considering that the primary means of transportation across the river is by ferry.

The Rio Negro bridge crew has to overcome these challenges as they attempted to span a portion of the river that experts knew very little about. In fact, so little was known about the span of river where the bridge was planned to cross that initial projections required significant surveying of the riverbed as well as monitoring of the river currents.

The task proved formidable. A work platform of 400 barges was needed on the river as well as a crane that could hold up to 300 tons to position the piles. But the economic impact was also significant. The bridge construction employed over 3,300 workers directly with an additional benefit of more than 8,000 workers tangentially involved with the project.

As Henrique Domingues, manager of Obras Consorcia Rio Negro, describes it, “We had big challenges. First, the Rio Negro is a big, fast-flowing river, so we chose the narrowest point where we could reasonably cross. Second, little was known about the geology of the region so we had to do surveys for the foundations. The foundations required large-scale metal skirts that we had to drive into the riverbed with incredible force. Also, we knew little about the currents below the surface of the river. All this makes the work a daily challenge and requires new technologies and techniques.” And special problems require special teams.

Crowning the Bridge

One of the special teams called in to complete the work on the diamond crown of the central span was Camargo Corrêa. Founded in 1939, Camargo Corrêa is now one of the largest construction companies in Brazil. Camargo Corrêa specializes in big projects such as energy and industrial facilities, mass transportation, and sanitation, so it was well placed to take charge of one of the most important and difficult pieces of the bridge, the cable span.

After assessing the challenges of the contract, Camargo Corrêa contacted Topcon dealer Santiago & Cintra to supply them with the equipment they needed to get the job done. But even then, the surveying teams met unique problems, such as the fact that moving water does not make for good reference points. As surveyor Rosivaldo Marques of Camargo Corrêa explains, “In the construction of a bridge we have only two fixed points, the river banks, essentially to the north and south. In this sense all the measurements with the equipment was made from a fixed point on the south side of the construction site. Without any total station this would not have been possible.”

The surveying teams, working from both the stable framing of the bridge and the constantly moving barges, had to adjust to constantly changing realities. Wind surge, torrential rains, flooding, all could change the playing field. Thankfully, good equipment makes for quality work. As Marques explains, “Santiago & Cintra delivered our Topcon total stations as requested and they were always perfectly calibrated and ready to go to work. Topcon’s local technical support was invaluable to our work on the bridge. We could always count on Topcon technical support from Santiago & Cintra.”

The final bill is expected to total $1 billon Brazilian Reals ($614 million USD/Euro 500 million): 60% over initial projections. But by reducing the 40 minute ferry ride to a 10 minute drive, and, perhaps most importantly, by increasing the speed of communications thanks to the fiber optic cable embedded in its infrastructure, the Rio Negro bridge will take this Amazonian region into the  21st Century.