Webuild: Fisia Italimpianti nearing completion of lot 2 of the Riachuelo System, one of the world’s largest and most complex environmentally sustainable projects

One of the largest and most advanced wastewater treatment plants in the world, designed to serve 14 municipalities and improve sanitation conditions for 4.3 million people in Buenos Aires, Argentina

Milan, 20 March 2025 – Work on Lot 2 of the Riachuelo System, a major infrastructure project aimed at reducing pollution in the Matanza-Riachuelo River in Buenos Aires, Argentina, is nearing completion. Lot 2 includes the construction of a major wastewater treatment plant, led by Fisia Italimpianti, a Webuild Group subsidiary specializing in water treatment and desalination, on behalf of AySA (Agua y Saneamientos Argentinos).

In recent weeks, technical testing has been completed, and with the project now 95% finished, full completion is expected by the end of May.

The Riachuelo System is the largest project of its kind in Latin America and has received support from the World Bank due to its significant social and environmental impact. This ambitious initiative will benefit 14 municipalities in Buenos Aires, improve sanitary conditions for over 4.3 million people, and eventually expand sewer access to an additional 1.5 million residents.

The Riachuelo System consists of a wastewater treatment plant and an extensive network of tunnels. These tunnels run approximately 27 meters below the Río de la Plata, the main waterway into which the Riachuelo River flows.

The project is divided into three sections. Webuild has already completed Lot 3 and, together with Fisia Italimpianti, is now finalizing Lot 2. Fisia Italimpianti leads the consortium with Acciona, holding a 65% stake.

Lot 2 involves the construction of a wastewater treatment plant that, once completed, will be among the largest of its kind in the world. It will be capable of treating up to 2.3 million cubic meters of wastewater per day.

The project includes an inlet pumping station with a capacity of 36 cubic meters per second, a pre-treatment facility designed for 27 cubic meters per second, and an outlet pumping station.

Lot 3, completed by a consortium led by Webuild, involved building 12 km of the main tunnel, which serves as the discharge conduit for the wastewater treatment plant. Excavated 40 meters beneath the riverbed, the tunnel has an internal diameter of 4.3 meters and is designed to channel treated water from the plant, dispersing it at a rate of 27 cubic meters per second. A key feature of this project is its advanced diffuser system, comprising 34 vertical steel pipes known as “risers.” Each riser, just under one meter in diameter, extends vertically to the riverbed, ensuring efficient dispersion of treated water. This complex engineering solution played a crucial role in the project's success and earned it the prestigious ITA International Tunneling Award in 2021.

For over a decade, Webuild has been a global leader in the water sector and continues to drive sustainable development through a series of major projects worldwide. In the U.S., the company is finalizing the Northeast Boundary Tunnel (NEBT) to strengthen Washington, D.C.’s sewer system against extreme weather events. It has also completed Lake Mead’s Hydraulic Tunnel No. 3, an advanced water intake and transport system designed to supply Las Vegas and surrounding areas. In Tajikistan, it is building the Rogun Dam, the tallest in the world, which will double the country’s energy production capacity. Similarly, in Ethiopia, Webuild is leading the construction of the Grand Ethiopian Renaissance Dam (GERD), the largest in Africa, to boost hydroelectric power generation and drive regional development. Meanwhile, in Australia, the company is working on Snowy 2.0, the country’s most ambitious hydroelectric project.

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Webuild is a global leader in the design and construction of large, complex infrastructure projects in sustainable mobility, hydropower, water treatment, and green buildings. A recognized leader in the water sector, it works in approximately 50 countries with over 92,000 people of 125 different nationalities. The Group boasts nearly 120 years of applied engineering on more than 3,700 completed projects, with a track record of 13,648 kilometres of railways, 891 kilometres of metro lines, 82,577 kilometres of roads and highways, 1,022 kilometres of bridges and viaducts, 3,462 kilometres of tunnels, and 318 dams and hydropower plants. Among its most famous projects: the expansion of the Panama Canal, the Long Beach International Gateway bridge in California, the Third Bosphorus Bridge in Turkey, the Sydney Metro Northwest skytrain viaduct and bridge, the Kingdom Centre skyscraper in Riyadh, Saudi Arabia, and numerous metro lines in Copenhagen, Paris, Rome, Milan, Naples, Doha, Thessaloniki, and Riyadh. Among the main ongoing projects, the following stand out: the New Genoa Breakwater, the Brenner Base Tunnel, Line C of Rome's metro network, the high-capacity railways between Genoa and Milan, the high-speed railway between Naples and Bari, the Palermo-Catania-Messina high-capacity railway, the Snowy 2.0 hydropower scheme in Australia, and the Trojena dam network in Saudi Arabia. As of December 31, 2024, the Webuild Group registered total revenues for €12 billion and a total backlog of €63 billion, with more than 90% of its construction backlog related to projects linked to the United Nations Sustainable Development Goals (SDGs). Webuild, subject to the direction and coordination of Salini Costruttori S.p.A., is headquartered in Italy, is listed on the Milan Stock Exchange, Borsa Italiana (WBD; WBD.MI; WBD:IM), and since 2021, it is included in the MIB ESG index of the Italian blue-chip companies with the best ESG practices.