Buenos Aires water project continues to make progress

Italian contractor CMC di Ravenna has deployed the 4.66m diameter Terratec machine for the final 5km of the tunnel. Named Juana, the EPBM has advanced 88 rings, excavating 123.2m in one week.

The 13.5km Ri´o Subterra´neo a Lomas tunnel is a part of the multi-billion dollar Agua Sur system being built by Argentina’s national water and sanitation company AySA. It is the country’s most extensive water infrastructure project in four decades, providing fresh water access to 2.5 million inhabitants in the southern metropolitan area of Buenos Aires.

The first 4.66m diameter EPBM, named Eva, was launched in September 2020. It completed the first drive of 8km at the end of 2022.

To launch Eva during the Covid-19 pandemic, CMC di Ravenna and Terratec secured permission from Argentina embassies in different countries to send a team of international technicians to Argentina.

The Terratec EPBMs have been designed to handle the diverse soft ground geology along the project alignment, encompassing silts, sandy silts, and some cobbles. Equipped with high-torque soft ground cutterheads featuring a spoke-style design boasting a 49% opening ratio, the TBMs incorporate cutting tools comprising multiple fixed and back-loading knife bits. This configuration ensures not only rapid advancement but also minimises the need for interventions.

Both EPBMs were launched and received from shafts. The tunnel excavation is at an average depth of 25m, commencing with an approximately 400m radius curve before continuing along a predominantly straight alignment, with a maximum slope of +/- 2.0%. As the machines progress, a precast concrete lining ring will be installed comprising six segments (four parallelograms and two keys), each measuring 250mm thick and 1400mm wide.

The first launch shaft has four interconnected circular sectors at the bottom area. The shaft is 45m in length, 12m in width, and 25m in height.

The Agua Sur System includes several major components. These include establishing a raw water intake, and expanding the General Belgrano Water Treatment Plant to increase its production capacity from a maximum of 1.95 million m³ per day to 2.95 million m³ per day. It also involves the construction of a 23km water conveyance tunnel, built in two stages, and the creation of two pump stations and a 46km network of pipe connections.