The Millau Viaduct is a work of both engineering prowess and architectural grace. Spanning the River Tam, in the south of France, Millau is a massive piece of infrastructure that appears as light as the fog that puffs across the valley, despite the superlatives that might weigh it down: It's the tallest (1,122 feet) and longest (1.6 miles) multispan cable-stayed bridge in the world.
Its construction took only three years, thanks to a pre-fabrication process in which 2,000 sections of the steel roadway were manufactured off-site, lifted into place, and aligned with the help of a GPS. The technique also allowed for the minimum disruption of the surrounding environment -- echoing the bridge's overall goal of relieving the river valley of traffic while connecting the highway systems of France and Spain. Its remarkably slender profile and the way its graceful span emphasizes the drama of the landscape prove that cutting-edge building technology need not be at odds with the natural landscape.
Boston's Central Artery/Tunnel Project, better known as the Big Dig, constitutes the biggest construction project in U.S. history. It called for replacing an elevated six-lane highway through downtown Boston with an 8-to-10 lane underground highway directly beneath it. Engineers of this subterranean road had to navigate existing subway lines and innumerable pipes and utility lines. In addition, the project called for extending the Massachusetts Pike, which ended just south of downtown, across Boston Harbor to the airport. And of course, this massive construction -- on the scale of the Panama Canal or the Chunnel from Britain to France -- had to happen without disrupting the daily traffic flows and business life of the city.
The engineering and construction marvels of the Big Dig are many: some five miles of slurry walls, the biggest use of the construction technique in North America; three highway-sized jacked tunnels, the biggest use of this technique in the world; the widest cable-stayed bridge in the world and the first in the U.S. with an asymmetrical hybrid design; innovative soil-mixing and ground-freezing techniques to improve the quality of Boston's soft soil; the country's most advanced electronic traffic-management system, developed with the help of MIT; and more. For these breakthroughs -- as well as the project's infamous budget and scheduling woes -- it has become a case study for public works.
The idea of building a sea barrier to protect Venice from floods has been debated since 1966, when nearly 2 meters of water partially submerged the city. Last September, despite ongoing controversy regarding the environmental wisdom and technical feasibility of the project, Italian Prime Minister Silvio Berlusconi approved the second phase of the flood-barrier plan. Called Mose, the scheme calls for 78 hinged barriers, each approximately 6,500 square feet, to rise from the sea floor when the high tides of the Adriatic threaten the city.
Toshka Project - Mubarak Pumping Station
The $70 billion Toshka project is Egypt's effort to transform half a million acres of desert into arable land, creating what it calls a "second Nile Valley." The centerpiece of the project is the Mubarak Pumping Station, located in the middle of Lake Nasser. The station's 24 pumps will enable it to channel 1.2 million cubic meters/hour into the 72-km. system of canals that will carry the water to the country's arid regions.
While its throughput is impressive, the Mubarak Pumping Station is admired by engineers for two less obvious feats: the structural system of steel mini-piles (a cost-effective, earthquake-safe alternative to concrete supports) and the jointless design of its underwater portions (which ensures a watertight structure despite a temperature range of 0 to 50 degrees centigrade that would destroy standard joints). The Mubarak Pumping Station was recognized as one of the most outstanding civil-engineering achievements of 2005 by the American Society of Civil Engineers.