Topographical Feature
The unique terrain of the construction site was a challenge for the project. Most tunnel excavation projects are carried out in flat terrain or from higher ground to lower ground to optimize efficiency. However, the narrow access road to the Kowloon Byewash Reservoir, where located on high ground, could not accommodate large construction vehicles and served as the starting point for the excavation work. As a result, the starting point of the project had to be relocated to the Lower Shing Mun Reservoir. This meant that the tunnel boring machine had to excavate from lower ground to higher ground. Furthermore, the endpoint of the tunnel boring machine was located inside the Kowloon Byewash Reservoir, and if the machine was to exit through this point, it would inevitably affect the water quality of the reservoir.
To protect the water quality of the reservoir, the project team opted for a compromise solution: When the TBM reached the closest possible point to the Kowloon Byewash Reservoir, excavation was stopped, and the TBM was dissembled and retracted along the 2.8-kilometer tunnel to the Lower Shing Mun Reservoir. Small machinery was then used at the Kowloon Byewash Reservoir to complete the final excavation work and connect the entire tunnel.