The Management of Contaminated Sediment in Hong Kong

Abstract

Many years of uncontrolled discharge of sewage and industrial effluent have resulted in serious contamination of much of the sediments underlying inland and nearshore coastal waters in Hong Kong by potentially toxic heavy metal and trace organic pollutants. Much has been achieved to improve control of this pollution at the source and prevent further deterioration. Nevertheless, comprehensive environmental assessment and management measures are required to ensure that any unacceptably contaminated sediment that must be dredged to facilitate infrastructural development is safely handled and disposed of.It is estimated that some 50 Mm3 of sediment classified as unacceptably contaminated may require dredging and special management elsewhere over the coming 10-year period. To facilitate improved decision making about the most appropriate disposal options for dredged sediment Hong Kong has recently implemented a new sediment quality assessment framework under which information on the biological activity of contaminated material is considered in addition to data on chemical composition.Dredged sediment classified as unacceptably contaminated has been disposed of at a contained disposal facility at East Sha Chau since 1992. To date over 20 Mm3 of sediment has been placed into seabed pits that are subsequently capped with clay. The site is subject to a rigorous monitoring programme that has clearly demonstrated its environmental acceptability.