Brunei Temburong Bridge

Brunei Darussalam occupies two districts, Brunei–Muara and Temburong on either side of Inner Brunei Bay. The Brunei Government plans to construct a road and bridge link between the two districts to support the country’s development. The fast-track nature of the project meant that the project EIA and the writing of tender documents occurred at the same time.

The bridge construction is likely to require dredging a 120 m wide trench along the route of the bridge to three metres below Chart Datum to allow piling vessel and barge access. Smaller dredged channels will also be needed to access concrete casting yards for the bridge elements. The quantity of dredged material to be removed has been provisionally estimated at 7,000,000 m³. There are numerous protected areas including several forested islands in the vicinity of the bridge crossing and areas of mangrove and peat swamps, especially along the southern side of the inner Brunei Bay. There are also areas of intertidal mudflat. The intertidal mudflats, mangroves and swamp areas attract migratory birds. There is a range of fishing activity within the bay.

We used a suite of 3D area numerical models to characterise the hydrodynamic and sediment transport regimes of the study area, including all of Brunei Bay and nearby areas of the South China Sea and demonstrate the potential for the bridge construction to have adverse effects. Our findings were used to develop a dredging and disposal mitigation and monitoring plan to track any impacts of the works and hence manage the proposed dredging works to minimise any impacts. This plan was documented within the Dredging and Disposal Management Plan.

The fast-track nature of the project meant, in parallel to the EIA, documents for the tendering process also had to be prepared. HR Wallingford wrote the Dredging and Disposal Management Plan (DDMP) which described the responsibility on the contractor to ensure the execution of the marine dredging and disposal works in an environmentally responsible manner including complying with all relevant permits and licences. Measures were specified within the DDMP to:

• minimise the impacts of dredging and disposal on water quality;
• minimise damage of adjacent mangrove and sub-tidal habitats either directly or by sedimentation;
• avoid impacts upon marine fauna;
• prevent the introduction of alien species;
• minimise interference with fishing activity.