The Medellín River runs right through the heart of the city of the same name in Colombia. Much of the sewage generated in the second largest economic center in the country is discharged untreated into the river and negatively affects not only the water but also the quality of life of local residents. For a clean future, therefore, the project "Medellín River Sanitation Program" is being carried out to clean up the Medellín River: a large-scale restoration project as part of which a new sewage treatment plant is being built in the neighboring municipality of Bello. Around 120 tonnes of contaminants which are transported by sewage from industry, commerce and households will be treated there daily in future. The burden on the Medellín River will thus be significantly reduced and 95 percent of the sewage discharged into the river, purified.
For the implementation of the new treatment plant sewage collectors and corresponding connecting channels had to be bored. Three Herrenknecht AVN Machines were used for this purpose in the complex project, which ran through subsoil containing groundwater and involved 27 drives with lengths ranging between 200 and 750 meters. Excavation of the tunnel with a total length of over 8 kilometers began in August 2012 in Moravia, a suburb of Medellín. The second AVN Machine began its work in October in the municipality of Bello. Toward the end of the project, the third AVN Machine with a diameter of 2,425 millimeters was used for smaller water collectors. Section by section the geology allrounders progressed with their tunnelling with overburdens of 3.3 to 21 meters. In doing so they successfully and without causing interferences crossed under both railway and metro lines, i.e., important avenues of passenger and cargo traffic, as well as the Medellín River itself. The top performances were 30 meters per day and 108 meters per week.
In October 2015 the last of the Herrenknecht machines reached its destination. With the commissioning of the new sewage treatment plant the sewage from more than three million people in the area can be purified and discharged clean into the river: an important step for the revitalization of the river and the region along its banks.