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Hong Kong transfers the Sha Tin sewage treatment plant to a cave complex in Nui Po Shan, where tunnels, pumping networks, and colossal underground structures will allow the release of an extensive urban area without interrupting an essential service for hundreds of thousands of residents.
Hong Kong is transferring one of the main sanitation structures from Sha Tin to a set of caves excavated in Nui Po Shan, inside a mountain near the current complex, where a new underground sewage treatment plant will be installed.
With about 14 hectares and an internal volume of approximately 2.3 million cubic meters, the project was designed to house facilities responsible for regional treatment, maintaining essential operations under the rock and freeing up an extensive area currently occupied on the surface.
According to the Hong Kong Drainage Services Department, responsible for the project, the transfer will allow the release of approximately 28 hectares of the current station, space that can be allocated for housing and other public uses after the completion of the planned stages.
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Underground station reorganizes Sha Tin sanitation
More than just opening large cavities and moving equipment, the intervention reorganizes the entire sewage route, from the Sha Tin and Ma On Shan pumping stations to the final treatment and discharge of the effluent through the existing infrastructure.
Technical materials released by the agency indicate that the station serves an area with about 700,000 residents and has a design capacity of 340,000 cubic meters per day, in a densely urbanized region near the mouth of the Shing Mun River.
Inside Nui Po Shan, the core of the new system will be formed by the main cave complex, whose underground area will reach approximately 14 hectares and whose total volume will reach 2.3 million cubic meters, according to official project data.
Only after the completion of the civil structures and necessary connections will the treatment equipment be installed in the caves, following a planned sequence to preserve service continuity while the new unit is prepared to replace the current complex.
Access and ventilation tunnels cross the mountain
Connected to Mui Tsz Lam Road, a secondary tunnel of approximately 260 meters will provide access to the interior of the mountain and support the movement required during construction and future operation, without relying solely on the land occupied by the existing station.
To maintain suitable conditions within the underground environment, the project also includes a ventilation shaft about 70 meters deep and a gallery of approximately 660 meters connecting this structure to the main caverns.
As the facility will operate under the rock, these components will play a central role in air circulation and control of operational conditions, integrating an industrial system that needs to function continuously, safely, and in coordination with other structures.
After treatment, the water will flow through two discharge pipes, each about 2.2 meters in diameter and 320 meters in length, responsible for connecting the future underground station to the already existing effluent tunnel.
This connection will allow preserving the integration with the network used to conduct the treated material out of the complex, avoiding the need to rebuild the entire discharge infrastructure and taking advantage of systems that already serve the region.
Pressurized network will connect Sha Tin and Ma On Shan
Before reaching the caverns, the sewage will pass through a new intermediate pumping station, positioned at the southwest end of the current unit and connected to pressurized lines that will form the main link to the underground complex.
In total, these lines will be approximately 4.6 kilometers long and have diameters between 0.8 and 1.2 meter, creating a network capable of connecting pumping stations, the new intermediate system, and the main entrance of the future plant.
Six stations that already serve Sha Tin and Ma On Shan will also be modified, including the main Sha Tin pumping station and the units at A Kung Kok, Ma On Shan, Kau To Area 56A, Chinese University, and Pak Shek Kok number 3.
The scale of the project is evident not only in the size of the caverns but in the number of structures that need to operate in sequence, conducting sewage from different points in the region to treatment and, subsequently, to the discharge pipes.
Phased construction will prevent service interruptions
To avoid interruptions in sanitation, the transfer was divided into stages that include site preparation, access construction, cavern excavation, upstream network execution, equipment installation, and gradual deactivation of the currently operating station.
Only after the underground unit becomes operational can the existing complex be deactivated and demolished, freeing up the 28 hectares on the surface without compromising a service that serves hundreds of thousands of residents daily.
In addition to engineering structures, the official scope includes environmental mitigation measures, monitoring, and auditing, with interventions at tunnel entrances, containment works, and actions aimed at reducing risks associated with the natural terrain.
Special attention will be given to the points where the accesses meet the slope, areas where soil stability and the safety of the structures require continuous technical monitoring during the different phases of construction.
Billion-dollar project expected to be completed in 2031
According to the Drainage Services Department’s register, the main works began on July 5, 2021, and are expected to be completed by the end of 2031, following a schedule that matches the complexity of the excavations and underground connections.
Officially estimated at 14.0765 billion Hong Kong dollars, the investment covers caverns, tunnels, pipelines, pumping stations, and other necessary interventions to fully and safely operate the new underground system.
By relocating the station inside the mountain, Hong Kong preserves treatment capacity without maintaining a large facility on a contested urban land, creating space for new uses only after the complete removal of the current unit.
In this model, the rock itself becomes part of the city’s infrastructure, housing an industrial plant connected to the sanitation network while the surface is reserved for activities that directly depend on open and accessible areas.
How many other metropolises could transfer essential facilities underground, maintain high-capacity services in continuous operation, and simultaneously recover valuable urban areas currently occupied by structures indispensable to the daily life of cities?
