At the Bigge valley reservoir dam in Sauerland, the "Ruhrverband" (association of Ruhr cities) was having the supply line system – in the form of the Biggerand sewer – completed for the Biggetal sewage treatment plant near Olpe, which came into service in 2000. This plant will make it possible for eleven older sewage treatment plants to be decommissioned. Centralized treatment of the sewage should bring about considerable cost benefits and improve the quality of the water in the Bigge valley reservoir.
For the new, 38-kilometer-long sewer system, a Herrenknecht AVN1600 drove two tunnelling sections of an overall 760-meter length. Faced with 80 to 200MPa rock strengths, the machine worked its way doggedly through the compact rock combination with a 400kNm torque and average tunnelling rates of up to 14 meters per day.
