Milan, August 20, 2025 – Webuild Group subsidiary Fisia Italimpianti and its consortium partners have officially delivered to client Agua y Saneamientos Argentinos S.A. (AySA) Lot 2 of the Riachuelo System in Buenos Aires, Argentina, marking the completion of the largest and most technologically advanced wastewater treatment plant in Latin America.

Lot 2 is the latest example of the ability of Fisia Italimpianti and its parent Webuild to build large, strategic projects designed to have a significant social impact on the communities they serve.

The plant, which is already in operation, is part of a massive project supported by the World Bank to clean up the basin area of the Río de la Plata (River Plate), improving health safety for the more than four million residents of the Argentine capital. Serving 14 municipalities, the system can treat up to 2.3 million cubic metres of wastewater a day. It is also expanding the sewage system to reach 1.5 million residents.

The Riachuelo System is comprised of three lots. The first collects wastewater; the second, which has just been delivered, pretreats it; and the third, also recently delivered by Webuild, disperses it into the river by means of a subfluvial tunnel 12 kilometres long and 40 metres below the riverbed. 

Lot 2, which is central to the system, comprises an inlet pumping station with a capacity of 36 cubic metres per second, a pretreatment facility for 27 cubic metres per second, and an outlet pumping station.

The water flows down the tunnel with an internal diameter of 4.3 metres, then up through an innovative diffuser system consisting of 34 vertical steel pipes, or risers, along the ceiling of the tunnel that ensures a safe and uniform dispersion in the river. This highly complex engineering feat earned the project the prestigious ITA  International Tunneling Award in 2021.