High-quality raw water is becoming scarce in a city with a surface of 6,340 square kilometers and more than 20 million inhabitants. A network of water lines is plannend to compensate the deficit of six million cubic meters of raw water per day, including two parallel seven-kilometer-long tunnels crossing under the River Yangtze.
In Pudong the first TBM S-407 started tunnelling in April 2008 at a depth of 35.6 meters. Four months later the S-408 followed. The biggest challenge was to cope with the high water pressure. After 19 months the S-407 reached its target in Changxing followed by the S-408 that arrived at the target shaft in January 2010.