RESTORATION OF A LARGE URBAN LANDFILL IN HONG-KONG

Sai Tso Wan landfill which covers an area of approximately 9 ha and contains 1.6 x 10(6) t of refuse was completed in 1980. Intense building developments currently under construction will bring a population of 27 000 people and a busy railway station within 200 m of the landfill. The landfill is actively generating landfill gas (LFG) and leachate. A 65 m high landfill slope overlooks part of the development area and posed a risk of slope instability. An investigation was carried out to determine the extent of LFG generation and its directions of migration and to determine the landfill slope stability. A restoration works design concept based on entrapment of the LFG by a low permeability soil cover, a peripheral cut-off barrier and extraction of the LFG through suction wells, together with recompaction and flattening of the side slopes, was adopted. Detailed design paid particular attention to the effects of ongoing settlement on the drainage and LFG extraction systems, and to minimizing future maintenance. The landfill gas is flared off. This Paper describes the investigation, design approach and the construction of these restoration works.