Mexico City ready for the World’s biggest Wastewater System

The world’s biggest urban wastewater system with an investment volume of more than 650 mill. Euro is being created in Mexico City with the “Tunnel East” wastewater channel. In this way the Mexican government intends solving the massive wastewater problems faced by the Mexico City area with its more than 20 mill. inhabitants.
For this project Herrenknecht is supplying 3 tunnelling machines (EPB shields) with diameters of 8.70 and 8.89  m. They will be used for building the new Wastewater Tunnel East in Mexico City, which is more than 60  km long and up to 200  m deep. The first tunnel boring machine, the EPB shield S-497 (8.70  m Ø), was accepted by ICA Ingenieros Civiles Associodas at the factory in Schwanau/D in February 2009.
During a visit to the Schwanau factory the director-general of the Mexican water authority Conagua, José Luis Luege Tamargo, observed the completion of the first tunnel boring machine. “The Waste-water Tunnel East is one of the world’s most important water projects when one considers the investments, the length of the tunnel and the technology applied,” Tamargo explained. “The project will substantially reduce the risk of flooding for Mexico City and in turn improve the safety and the prosperity of the inhabitants and protect their property.”
 
The “Emisor Oriente” Project
Mexico City and its environs possess an inadequate drainage system for the more than
20 mill. people living there. On account of the pronounced over-utilization of groundwater reserves the metropolis finds itself confronted with an increasing more difficult water supply problem. The outcome is that the ground has sunk by around 10 m. As a result pumps have to be increasingly used to remove wastewater from the city.
Between 1975 and 2008 the outflow capacity of the drainage system in Mexico City has dropped by some 30  % from 280 to 195  m³/s. At peak periods as much as 315  m³/s has to be contended with. The Mexico Valley is threatened by serious flooding owing to a lack of discharge outlets and back-up facilities and extremely heavy rainfalls.
 
Programme to regenerate the Water Reserves
In order to solve the problems caused by wastewater the government of President Felipe Calderon initiated a programme intended to regenerate the water reserves in the basin of the Mexico Valley:
– reduction of the over-utilization of groundwater reserves
– treatment of all sewage
– opening up new sources of supply
– building of the Wastewater Tunnel East to avoid flooding.

Wastewater Tunnel East
The Wastewater Tunnel East is planned as an alternative drainage system to the Central Tunnel. It possesses 24 inflow channels, which are between 150 and 200  m deep. The Wastewater Tunnel East stretches over a length of 63  km in 6 part-sections and has a planned internal diameter of 7  m. It will have a run-off capacity of on average 150  m³/s. The investment volume amounts to more than 650 mill. Euro. The scheme is scheduled for completion in September 2012.