MEXICO IS BUILDING THE WORLD'S LONGEST AND LARGEST SEWAGE TUNNEL

Mexico City is building the world’s longest sewage tunnel with the aim of preventing flooding during heavy rainfalls. This is because the gigantic metropolis that over 22 million people call home is subsiding.

Sigunit®, ViscoCrete® AND ViscoFlow® FOR 62 KM TUNNEL
At 62 kilometers, the «Tunel Emisor Oriente » TEO is not only the longest, but also the largest sewage tunnel in the world with a diameter of just under nine meters. Sika Mexico is involved in the construction work with the products Sika® Sigunit®, Sika® ViscoCrete® and Sika® ViscoFlow®. Construction of the new sewer began in 2009. This will transport sewage at a depth down to 150 meters below ground as far as an enormous sewage treatment plant that is still under construction. The facility is set to commence operation in 2015.

MEXICO CITY IS SINKING
Mexico City was originally situated on the island of a lake. There were often floods even at the time of conquest by the Spanish. The Spanish drained the lake as the city grew. The result: The growing population used more groundwater than could be replenished by rain. The sinking groundwater level means that parts of the city have subsided by up to 14 meters in the last 100 years – more than Venice, which has only sunk by 2.8 meters in the same period.

A THIRD OF THE DRINKING WATER IS LOST
The phenomenon is especially apparent in the center of the city at the "Monument to the Revolution", erected in 1934. At that time the city routed a water pipe below the square, which today is clearly visible 7.9 meters above the ground.

The ground movements are a vicious circle: As the ground subsides, drinking water pipes are damaged, a situation that frequently remains unnoticed. As a result, a third of the drinking water is lost from the pipe system – even though 40,000 leaks are repaired each year – and even more water has to be pumped out of the ground, which in turn leads to further subsidence of the ground.

BREAKTHROUGH WHEN CONCRETING WITH Sika® ViscoFlow®
Construction work is currently in progress on four construction lots with various consortiums. Four tunneling machines made by Herrenknecht and Robbins with mounted shotcrete equipment and robotic technology of the Sika brand Aliva from Widen are in service. More than 1 million cubic meters of concrete will be processed for the prefabricated lining segments in the four year construction period.

LONG CONCRETE WORKABILITY THANKS TO PCE TECHNOLOGY
To produce high-quality concrete, above all good aggregates (gravel/sand) are needed, as these make up over 75% of the recipe. But precisely this material is lacking in Mexico City, a conurbation located 2,300 meters above sea level at the foot of Popocatépetl, the second highest volcano in North America at 5,636 meters.

To produce the highest concrete quality economically is therefore the challenge confronting the team of Sika Mexico, Managing Director Rolf Manser and Target Market Manager Carlo Rocha every day. Thanks to the new polymers of the Sika® ViscoFlow® product family developed in Switzerland – it is now possible to successfully use the PCE technology in large construction projects on the Mexican market. The concrete’s long workability of over three hours, at a low water content below W/C = 0.45 is a new benchmark for Mexico City. Set by Sika!

TECHNICAL SUPPORT
Thanks to professional technical support for customers – from engineering consultancy through to quality monitoring with mobile concrete laboratories – Sika can provide the highest service quality in Mexico. Customers appreciate this, like Holcim Apasco Mexico, for whom Sika is the main supplier in infrastructure construction, a prime example being the largest dam currently in construction, the Zapotillo dam.