XN000022-1995-10-18 — Page 65

48

At the strategic planning level, the cumulative hydrological and water quality impacts resulting from reclamation projects have been assessed in the context of the Territorial Development Strategy, Metroplan and Port and Airport Development Strategy. Engineering hydraulics studies have been undertaken to study the effects of reclamation projects and other harbour engineering works on tidal flows, wave propagation and sediment deposit. A large scale physical tidal model has been built to facilitate in-depth investigation of the hydraulic effects of such coastal developments.

At the project design level, detailed engineering studies and environmental impact assessments are conducted before the projects are implemented to ensure that the water quality impacts during and after construction do not exceed acceptable limits.

Careful construction programming and monitoring also ensure that any water quality problems caused by the reclamation works is kept to the minimum. Wherever necessary a seawall is first constructed at the perimeter of the reclamation. A carefully planned, controlled, and supervised dredging and in-filling operation then takes place behind the seawall to prevent floating refuse from reaching the harbour and minimise turbidity problems caused by siltation. Furthermore, a comprehensive monitoring programme for each reclamation is established with well defined action levels for key water quality indicators such as suspended solids, dissolved oxygen, turbidity, and temperature. If monitoring results should indicate action levels are in danger of being breached, the site staff would alert the contractor and require him to tighten the environmental mitigation measures in accordance with the contract specifications.

The main source of pollution in the Victoria Harbour is sewage discharges. This problem is being tackled by actions to declare the Harbour as a Water Control Zone and by the construction of Phase I of the Strategic Sewage Disposal Scheme which when completed in 1997 will improve the water quality of the Harbour by 70%.

End/Wednesday, October 18, 1995