Riachuelo environmental restoration system

Name of Project:

“Riachuelo environmental restoration system


AySA (Agua y Saneamientos Argentinos S.A.)

Total value:
$ 450 million

The hydraulic tunnel is part of Argentina's biggest public works project to clean up the Riachuelo River, one of the most polluted in the world near the capital, Buenos Aires.

The tunnel will flush into the River Plate waste water that will be pre-treated by a plant being built nearby, by means of a deep sub-river outlet about 12 km in length, with the promise of helping improve the quality of life along the banks of the river.​

The outlet comprises the following structures: a load shaft, about 50 meters deep; a tunnel, 10.5 km long with an internal diameter of 3.8 m, excavated using a double shield TBM; a return shaft located at the far end of the tunnel in the River Plata; and a diffuser system anchored in the river bed, 1.5 km long with an internal diameter ranging from 1.7 m to 3.8 m, equipped with 31 raisers for dispersing treated water into the river. 

The Project has a considerable environmental and social value as it enables the decontamination of the Riachuelo river basin affected by industrial activities (paper mills and tanneries) that dump process by-products into the river and by a sharp increase in the city's urban development. It is the first part of a broader programme, funded by the World Bank, for the sustainable development of the Matanza-Riachuelo catchment basin, aimed at its environmental restoration, and of the areas it passes through, considered among the most polluted in the world.

Load shaft 

This is an underground structure built with the support of the excavation walls, with retaining walls made with a hydro milling machine to a depth of 50-55 cm and 1.2 m thick. The walls intercept an impermeable layer of clay, allowing excavation of the chamber below the water table and the construction of the opening of the outlet tunnel. 

Sub-River Tunnel

A tunnel dug to a depth of 40 m in the bed of the River Plata, using a double-shielded TBM, with an internal diameter of 4.1 m including lining rings. A final structural lining in reinforced concrete is envisaged, ensuring an internal diameter of 3.8 m.

Return Shaft 

This is a structure located at the far end of the tunnel, built into the bed of the River Plata and used to input treated water into the diffuser. The structure comprises a steel jacket, 8 m in diameter, embedded at a depth of 40 m and with an internal lining of reinforced concrete. 

Diffuser System 

The diffuser system consists of a pipe dug into the riverbed resting on deep piles and support capitals, made of prefabricated tubes of diameters ranging between 3.8, 2.4 and 1.7 m. A total of 31 raisers are installed into the pipe for returning treated water to the River Plata.

Area cleaning: 112,500 m³
Earth moving: 550,000 m³
Concrete: 100,000 m³
river cleaning project

Last update: 30/05/2019