Hong Kong sewage plant to move into caverns in 11-year plan
Ambitious HK$30 billion project to vacate 28 hectares of land for housing or other community developments
Drainage officials will seek funding next year for the first phase of works to move a Sha Tin sewage treatment plant into a rock cavern in a massive project expected to last 11 years, according to Hong Kong authorities.
New details have also been revealed on the design of the facility, which is to be rehoused within Nui Po Shan of A Kung Kok, a hill across from the original site on the Shing Mun River.
The first phase is expected to cost about HK$1 billion out of a total of HK$30 billion, if not more, Drainage Services Department chief Edwin Tong Ka-hung said.
The 13 hectares of caverns will provide just half the space of its original footprint, but the project will be the largest sewage works relocated into a rock cavern in Asia.
“It will be like heart replacement surgery,” Tong said of the construction of various sewage networks. “We’re essentially building a new heart in a body and reconnecting the existing blood vessels, before disposing of the old heart.”
If all goes according to plan, the preliminary works are to commence as soon as 2019 and finish by 2022. The works range from building an access tunnel into the core to site preparation, diverting utilities and traffic as well as removing and preserving trees.
This will be followed by demolition works to enlarge the caverns, which could take another one to two years. Thereafter, efforts are to be made to move new waste treatment facilities into the caverns. Existing plumbing is to be diverted from the old plant.
The final phase will be to dismantle the old facility and test the soil for contamination. These steps will take another five to six years. Once this stage is completed, 28 hectares of waterfront Sha Tin land can be freed up for housing or other community developments.
The latest design of the cave plan involves blasting seven separate caverns in Nui Po Shan’s granite geology. Each one will be 32 metres wide – roughly the width of two basketball courts – and 25 metres tall – five double-decker buses stacked atop each other. The chambers will be 375 metres long.
Each individual area will house facilities – accessed by two tunnels – to handle 250,000 cubic metres of sewage produced by 650,000 Sha Tin and Ma On Shan residents. The caverns will be interconnected by 350-metre driveways and cooled by effluent.
Some of the high-quality granite blasted out of the cavern could be used for making concrete, Tong said.
“We will go to the Legislative Council in the second quarter of 2018 in the hopes of getting approval for the first stage of funding,” he added.
Asked if he was worried about delays and filibustering by lawmakers, Tong said he “expected it to take longer than normal” and was “cautiously optimistic”.
Sha Tin district councillor Siu Hin-hong said he hoped the move could be sped up as the construction works would be disruptive to residents.
“I support the move, but I hope the schedule can be shortened,” he said, expressing reservations about the time frame.
“They say 11 years, but so much can happen in the period. I don’t even know where I will be by then.”
Lo Wai-kwok, engineering sector lawmaker and chairman of Legco’s public works subcommittee, said delays were definitely a “worrying possibility” and would hold back the opening of a valuable piece of land.