MEXICO CITY – The world’s longest deep-drainage wastewater treatment tunnel is ready for operations in Mexico, marking a breakthrough in a prolonged construction process that lasted 11 years and generated massive cost overruns.
The Emisor Oriente (eastern emission) tunnel is over 62-kilometer (39-mile) long and would cater to more than 20 million people in the Mexican capital and its suburbs, according to national water commission, Conagua.
“The tunnel is now ready to operate. Only the operation protocol is to be finalized,” Patricia Ramirez, the deputy director of drinking water, drainage and sanitation at Conagua, said during a press tour.
Ramirez said the inauguration date depended on President Andres Manuel Lopez Obrador’s schedule.
The tunnel stretches 62.4 kilometers between the capital’s Gustavo A district and the city of El Salto in the state of Hidalgo, reaching a maximum depth of 150 meters at its lowest point.
The main function of the tunnel, built at a cost of 33.8 billion pesos ($1.7 billion), is to resolve the recurring problems of sewage and water-logging and flooding in the area.
The construction took seven years longer than the original deadline, which was set for the end of 2011, with the delay resulting in overruns worth 20 billion pesos.
“The construction stretched because the geology of the area has been variable,” Luis Manuel Garcia, the engineer in charge of the project, told EFE, emphasizing the problems in managing the tunneling machines.
The tunnel has 24 manholes apart from a floodgate for the exit of water which is connected to the outlet of the Emisor Central (central emission) tunnel before the waters reach the Tula river.
Around 35 percent of the water coming out of the tunnel would never reach the river, as it would be diverted to the Atotonilco wastewater treatment plant, from where the treated water would be supplied to farmers of the Mezquital Valley.
The new tunnel would help reduce the load on the Emisor Central, which has been operating for 44 years without being examined or repaired.
“One of the main benefits which the Emisor Oriental can provide is that operations in Emisor Central can be stopped to carry out its maintenance and inspection,” Rivera said.
The eastern tunnel is capable of carrying 150 cubic meters of water per second, equivalent to 15 tanker trucks, thanks to its seven-meter diameter.
The massive drainage capacity explains to a large extent why the tunnel has been designed to descend continuously until its outlet so that it doesn’t require any pumps.
The first section of the tunnel between Gustavo A district and the city of Ecatepec, bordering the Mexican capital, has been operational since 2013, servicing around 1.5 million people.