The Herrenknecht company specializes in tunnel-boring equipment. Three of its enormous drilling machines tare in Mexico to solve an equally massive problem: the inadequate drainage and wastewater system of Mexico City. The Mexican government is building what will be the world's longest wastewater tunnel, the 62-kilometer Tunél Emisor Oriente .In part three of our series, the tunnel diggers from Germany start work on the massive project to save Mexico City from its waste water, but immediately face the problem of water seepage. The machines have to be secured and repaired, and valuable time is lost. The deadline for completing the tunnel becomes more and more unrealistic.