Webuild: Riachuelo Outfall Tunnel

The Matanza-Riachuelo basin, Argentina’s most urbanized and industrialized area, is today alarmingly polluted after decades of sustained environmental malpractices. In order to mitigate such contamination, a massive rehabilitation programme, the Matanza-Riachuelo Basin Sustainable Development Scheme, is being implemented by AySA, the main concessionaire for water services in Buenos Aires. Such scheme will expand the sewage network of Buenos Aires and will benefit an area of 4,3mIlions inhabitants by intercepting several wastewater dicharges and conveying them to a new primary treatment plant for final discharge into the Rio de la Plata. Construction of the scheme has been subdivided into 3 Lots. Awarded in 2014 to a Joint Venture led by Italy’s Webuild SpA, Lot 3 foresees a 12km long segmentally lined tunnel entirely excavated underneath the riverbed of Río de la Plata, one of the largest estuaries worldwide, with a 5,2m cut diameter soft ground EPB type Tunnel Boring Machine. Its excavation faced successfully a variety of challenges, such as crossing waterbearing permeable cohesiveless soft ground formations and advancing at a face pressure in excess of 3,5bars for the entire route. It already ranks in the list of the longest TBM submarine / subfluvial tunnels constructed to date.

This award seeks to recognise excellence in delivery of a tunnelling project or tunnelling-related element of a project up to the value of $500M that was completed between July 2019 and July 2020 Judges will be looking to reward the project that best meets or exceeds the design brief and/or client expectation but that also have sought to advance industry best practice and have worked in a truly collaborative way.