Designed to resolve Hong Kong's seasonal flooding issues, the West drainage tunnel collects water from heavy rainfall thanks to its 32 wells and linking tunnels which expel the water directly into the sea. To carry out this 10.5 km project, two of the largest hard rock tunnel boring machines ever used in Hong Kong were needed in order to dig out the granitic and volcanic land. This particularly technical project, carried out in a very urban area, won the best underground project prize in 2011 at the International Tunnelling Awards.