The contractor is a joint venture of Aldesem, Proacon and Resca. The TBM is an 8.7m Robbins Crossover XRE (rock and EPB) machine.
Overburden along the alignment ranges from 8m to 170m. Much of the tunnel is in andesite with bands of tuff, as well as softer rock in fault zones. An 874m stretch of soft ground is also expected towards the end of the tunnel.
The TBM was launched in August 2015 and final breakthrough is expected in autumn 2016. Once complete, the tunnel will supplement an existing and overtaxed wastewater line built in the 1970s. The deep drainage tunnel will serve to prevent recurrent flooding in Valle Dorado, and will benefit an area with a total population of 2.1 million inhabitants.
