The Herrenknecht TBM, named Micaela, is one of two machines Webuild is using on the project. The 148m-long TBM has a 10.27m diameter and is designed for the groundwater soils in the area. It has excavated around 1,000m3 of soil and rock per day and made an average daily advance of 15-20m.

The second TBM, Delia, is 120m long and designed to excavate in dry ground.

The breakthrough comes a year after Delia completed the first section of the project, breaking through at Circunvalación Station.

The US$3bn project involves the excavation of a 27km tunnel to connect the ATE and Callao districts, and the construction of an 8km branch-off to Jorge Chávez International Airport, forming the first phase of Line 4. It also includes 37 stations, 36 ventilation and emergency shafts and two train depots.

So far Webuild and its partners Dragados, FCC and Cosapi have completed 14km of tunnel. The first 9km from Municipalidad de Ate Station to San Juan de Dios Station were built using the NATM. Delia has excavated and built 3km of tunnel from San Juan de Dios Station to 28 de Julio Station in the eastern part of Lima, and will continue excavating to Parque Murillo station in the city centre. Its last station will be Insurgentes, in Callao.

Micaela has excavated and built the 2km from Insurgentes Station to Buenos Aires Station. The TBM has now started boring towards Puerto del Callao Station. Webuild expects the TBM to arrive at the station at the end of May, marking the project’s next major milestone.

On completing this route, Micaela will be transferred to Gambetta Station to excavate and build the 8km of the branch line.

Micaela is named after Micaela Bastidas, an important figure in Peru’s independence, while Delia honours the first Peruvian woman to gain a degree in mining engineering at the National University of Engineering.