Emisor Oriente, Contract Section 1-6

With the building of the 'Emisor Oriente' sewer in Mexico City currently one of the world's biggest waste water projects is actually developed. The reason for this project is the poor state of the existing sewer system in this metropolis of 20 million inhabitants, which is increasingly overloaded. Six shield machines operating according to the EPB principle are being used to construct ·the sewage tunnel. The tunnel is altogether some 62 km long making it one of the longest tunnelling projects being executed at present. Apart from the tunnel route 24 shafts are also being produced to connect inflowing lines. The overburden for the tunnel lies between 15 and 160 m. The shafts reach depths extending to 150 m. During the course of the driving operations these shafts serve to service the tunnelling machines as well as to remove the excavated material. The tunnel is to be supported by means of a two-shell structure consisting of reinforced concrete segments and a reinforced inner shell. The thicknesses of the inner and outer shells vary from 35 to 40 cm according to the overburden and the subsoil conditions. This results in tunnel diameters of 8.40 and 8.60 m. The internal diameter amounts to 7.00 m throughout. In keeping with the predicted subsoil conditions the tunnel route by and large runs through the following ground Formations:

clayey-sandy lake deposits (approx. 50%)
consolidated lake clays (approx. 25%)
sands and clays, alluvial fans consisting of tuffs and alluvial material (approx. 25 %).

The free groundwater level can be up to 120 m above the tunnel roof, however frequently in the tunnel zone as well combined with low subsoil permeability coefficients. Extremely high loads both on the tunnel support as well as on the tunnelling machines result from the prevailing subsoil conditions. Following completion the 'Emisor Oriente' Tunnel will facilitate an average throughput of 150 m³/s. This corresponds to a capacity of almost 50% of the total volume of sewage, which has to be discharged in Mexico City at current peak times.

Country: Mexico
Region: Mexico City
Tunnel utilization: Utility
Type of utilization: Tunnel for Draining Sewage and Protection against Flooding
Client: Comisión Nacional del Agua (CONAGUA)
Consulting Engineer: Tunnelbautechnische Fachplanung/IMM Ingenieurbüro/Prof. Dr.-Ing. B. MaidI - Dipl.-Ing. R. MaidI GmbH & Co. KG
Contractor: ICE lngenieros Civiles Asociados
Main construction method: Trenchless
Type of excavation: Shield machine (SM)
No. of tubes: 1
Tunnel total length: 62 km
Cross-section: 7.00 m (internall diameter), 8.70/8.89 m (shield diameters)
Contract Volume: approx. 650 mill. euros
Construction start/end: 2009 till 2012
Opening: 2012