The Águas Livres (Free Water) Aqueduct. Built between 1732 and 1834 by order of King João V of Portugal as part of the effort to convey water from the Águas Livres spring to Lisbon and solve the city’s supply problems, it is 58 km long, including its branches. Among other structures, it includes the Mãe d’Água das Amoreiras Reservoir, which was used to store and distribute water in the Portuguese capital until 1967. It is one of the largest systems of its kind in the world.

The Lisbon Beltway (CRIL), a high-speed ring road that connects all the main routes into Lisbon, removes light and heavy vehicle traffic from the main roadways. Included in national roadway plans and local transportation proposals since 1980, it just needed a 3.7-km stretch to be completed. That stretch has been under construction since December 2007. An apparently simple project, it involves numerous works along its route, and runs through a densely populated urban area.

The CRIL passes through three counties and 10 parishes. The services it impacts include the area’s water and natural gas supply, power, telecoms, sewage treatment, military communications, the Lisbon-Sintra railway line and a subway tunnel. It also affects 130 m of the facilities of the Águas Livres and Francesas aqueducts, both of which are national heritage sites.

Little more than one of the Águas Livres Aqueduct’s 58 kilometers is visible above ground. The best-known section is one of Lisbon’s main landmarks: the 35 arches extending across Alcântara Valley, with the longest span stone arch in the world. The aqueduct was built to reflect the monumental spirit of the time when King João V ruled Portugal. “Like the other aqueducts, it is made up of underground galleries and is no longer used, and the idea of demolishing the pipes where the CRIL would pass through was actually suggested, but that would be wrong,” argues archeologist Margarida Monteiro, who has kept track of the works from the start. After all, that structure was the most important work of hydraulic engineering built in the eighteenth century.

“Bento Pedroso Construções (BPC, Odebrecht’s subsidiary in Portugal) presented the seventh-lowest bid among the companies competing in the tender. However, its technical bid included a solution that did not put the aqueducts at risk,” observes Project Director José Joaquim Martins. “We put all our engineering expertise at the disposal of our client, Estradas de Portugal, both for the conception and execution of the project.”

The stretches of the CRIL that intersect with the aqueducts were built underground. This solution was also adopted in other areas, resulting in the construction of tunnels in the middle of the 3.7-km stretch of the beltway. The historic structures now hang from the roof of the underground passageways, and micro-piles were used as containment structures and act as buffers, particularly where the masonry structures called Mães de Águas (literally “Mothers of the Waters”) are found (they were used as entryways into the aqueducts and ensured that they were well ventilated). First, micro-piles were positioned horizontally, with prefabricated concrete structures on the side walls. The excavation works and installation of the tunnel only got fully under way when they were in place.

“Technically speaking, that was the most complex stage of the project, because it involved directly impacting a national heritage site,” explains Pedro Quintas, the Technical officer responsible for the project. A team of 11 experts in archeology, conservation and restoration carried out a field survey on the state of the aqueducts and produced monthly reports that were sent to the Institute for the Management of Architectural and Archeological Heritage (IGESPAR).

Main numbers for the project

The aqueduct runs through several towns whose growth in the twentieth century has resulted in many disastrous attempts at renovation. “The pipes had to be replaced due to water pollution, for example, which led to large breaches, and they used a type of cement that was incompatible with the materials utilized when the structure was built,” says Margarida. “None of the works previously carried out in the vicinity of the Águas Livres Aqueduct took these factors into account. The laws were laxer then. It was a different mind-set.”

Once the aqueducts have been fixed in place, the restoration will begin, which includes cleaning, biological pest control, the removal of limestone accretions and stalactites, and the treatment of joints and metal parts. The project is scheduled for completion by the end of 2010.

The Águas Livres Aqueduct, the Mãe d’Água Reservoir, the Barbadinhos Steam Pumping Plant and the Patriarcal Reservoir are hubs of the Water Museum, managed by the Empresa Portuguesa das Águas Livres. For more information, visit the Odebrecht Informa blog.

The completion of the CRIL is a complex undertaking, so it was only natural for the project to have been shelved for nearly two decades. “The risks BPC has taken on, and the sheer magnitude of this project have firmly established us as a highly respected company, repositioning us and enabling us to stand out in the Portuguese market,” says José Joaquim.