Tuen Mun is one of a series of large new towns being developed in Hong Kong's New Territories as part of the Government's strategy of decentralization from the highly congested urban areas of Kowloon and Hong Kong Island. It is located in and around Castle Peak Bay in the west of the Territory, about 30 km from Kowloon.
In order to obtain the necessary land to accommodate the town and much of its infrastructure, an extensive reclamation was required in Castle Peak Bay. Additional land was provided by raising fiat low-lying areas and by excavating large terraces into the surrounding mountains and hills. These operations have resulted in more than 1200 ha of new land being formed for the town. More than 30 million cubic metres of dredged and land-won material were used during the reclamation work.
The solid geology of the Tuen Mun area is dominated by Mesozoic volcanic and intrusive igneous rocks, mainly comprising andesitic lavas and tufts and fine-medium grained granites. The valley is also underlain in part by Palaeozoic sedimentary rocks. A mantle of weathered material typically overlies the bedrock in most of the area. Superficial deposits occur onshore and offshore and comprise alluvial and marine sequences together with debris flow deposits, which are common in valleys and also as large fans in downslope areas. Debris flow deposits can also occur offshore beneath the recent marine sediments.
Numerous land and marine ground investigations have been carried out throughout the development area over a number of years