An 8.93m diameter Robbins EPB machine was launched on July 13 on Mexico City’s Tunel Emisor Oriente (TEO) 62km-long wasterwater tunnel.

Six lots, using three Robbins TBMs and three Herrenknecht TBMs, were planned for the wastewater line, but problems with the first TBM on Lot 1 prompted the machine change. “A flood in shaft 0 delayed the Herrenknecht machine for six months,” said David Juarez, site manager for Lot 1 contractor Ingenieros Civiles Asociados (ICA). “In order to compensate for time lost, we began boring with the Robbins machine at shaft 5 of Lot 1.”

The TBM at Lot 1 has started excavation using umbilical cables connected to the surface and a sludge pump for muck removal. Once it has bored ahead 150m, a continuous conveyor system and vertical belt will be installed for the remainder of the drive in mainly lake clays and sand.

Once the machine reaches the end of its 5km drive to shaft 3A at Lot 1, it will be removed and readied for its original 8.6km long bore at Lot 5.

Expected to complete in 2014, TEO will add about 150 cubic meters of water per second to the city’s wastewater capacity.