New TBMs say Olá to Mexico City

Three TBMs have been assembled in Corpus Christi, Texas, USA before heading south of the border to work on a 62 kilometre long wastewater line to be constructed in Mexico City, as part of the Emisor Oriente project.

The three Robbins tunnel boring machines (TBMs) will be shipped to Veracruz before being trucked to three different shaft launching sites.

Project owner and director of the National Water Commission (CONAGUA) José Luís Luege Tamargo said “These machines are specially designed for the unique geology of Mexico.

“They have been engineered to handle a face of mostly clay with some basalt rock. Their flexible design is a great advantage to the project.”

Located in the Valley of Mexico City, the geology of the capital consists of a drained lake bed with clays, interspersed with volcanic rock and boulders from long dormant, buried volcanoes in the area. The TBMs will utilise clay spades and drag bits that can be changed out for 17-inch disc cutters depending on the geology.

Two-stage screw conveyors will help to regulate high water pressures of up to 10 bar, which are some of the highest pressures EPBs have ever operated under. An initial 900 mm diameter ribbon-type screw conveyor will accommodate expected boulders up to 600 mm in diameter. Contractor CARSO Infraestructura y Construcción, S.A. de C.V. will use the TBMs on lots 3, 4, and 5, each between 9.5 and 9.7 kilometres in length.

Construction of the project will use six TBMs in total. The remaining three TBMs have been provided to the project by Herrenknecht.

The Emisor Oriente project
The Emisor Oriente project is designed to prevent flooding and increase capacity by its completion in 2012. Upon completion of the project in 2012, the wastewater line will operate in parallel with the city’s aging main wastewater line, Emisor Central, adding about 150 cubic metres of water per second.
Since the central line was built in 1964, Mexico has sunk at the rate of 10 centimetres annually, causing the drainage system pipe to lose its slope. In addition, the Emisor Central’s concrete and rebar walls have been severely degraded by corrosive gases, leaving areas of the city at risk for flooding.
Superintendent of planning and control for the National Water Commission (CONAGUA) Jesús Medecigo Castañeda said “This project is very important for Mexico City.
“We will avoid flooding in the downtown area, increase capacity, and all the water once untreated will now be treated at a nearby plant and reused for irrigation.”

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