Operation and Maintenance
The project does not seem to have an adverse effect on the surrounding area and ecology. Transplanted corals are in good condition, the settlements basis proved to work even better than expected due to voids and crevices in the ground. The effect of the silt screen on lowering the sediment concentration had only a small effect, but this did not cause any negative impact on the water quality.
After completion of the works, surveys have now been carried out at 3 month, 6 month and 12 month intervals and the evidence shows a high percentage of the transplanted specimens are in good condition, have grown larger and have attracted a thriving fish population. A program for longer term monitoring of the coral is currently being discussed between the port operator and the local diving community.
Settlement basins and sinker line
The settlement basins proved to work extremely well for a complete different reason than anticipated. Because during the first 7 months of dredging no excess water was discharged back to the sea, a large part of the excess water seeped into the many voids and crevices of the ground.
During the remaining 2 months some excess water was discharged into the sea via the pipeline. No adverse impact on the sea water quality was noted during this period near the exit of the discharge pipeline. No visible decolourisation was noted at surface level as well. The dredger was mainly involved in clean-up operations during the last two months. The amount of suspended solids that have been returned to the sea will have been minimal.
The settlement basin and pipeline discharge at 40m depth ensured that the impact of the excess water on the sea water quality was kept to an absolute minimum.
The silt screen was located 100m in front of the discharge point. No measurements were executed to study the difference in concentration levels inside and outside the silt screen. The decolourisation of the water at either side of the silt screen demonstrated the small effect it had on containing the suspended solids of the excess water from the reclamation along the inside of the breakwater.
Nonetheless,no adverse impact on the water quality was recorded at any station whilst reclaiming along the inside of the breakwater. The main reasons are:
- Reclamation only took place when a sufficient lead of breakwater was available;
- Currents inside the harbour basin were very weak.