The desalination plant is a strategic infrastructure by the Water Supplies Department of the Hong Kong Special Administrative Region Government. By adopting reverse osmosis technology for seawater desalination, the plant aims to diversify the water supply resources and provide reliable, adequate supply of potable water for Hong Kong. The plant site, located at Tseung Kwan O Area 137, has lower turbidity and suspended solids levels in the offshore waters with relatively stable water quality and salinity levels, making it a preferable site for a seawater desalination plant. Since it is located approximately 2.5 kilometres away from the nearest residential area, the impact to the nearby communities during construction is minimal.
Upon commissioning of the first stage of the project, the production capacity of potable water will be around 135,000 cubic metres per day, equivalent to 5 per cent of daily freshwater consumption. The ultimate capacity of the plant will reach 270,000 cubic metres per day following future expansion.
Reverse Osmosis Building—the heart of Tseung Kwan O Desalination Plant
TECHNICAL CHALLENGES
For construction, one of the major marine works is the installation of two underwater pipes: one to extract seawater for desalination—the intake pipe extending approximately 330 metres from the shore; and the other to discharge brine back into the sea—the outfall pipe extending approximately 270 metres from the shore. A 1.65-metre diameter outfall tunnel was constructed in rock while a 2.5-metre diameter intake tunnel was constructed in mixed ground. Instead of building two separate launching pits on land for the two tunnels, a common wall that combines the intake and outfall shafts was constructed to serve as the thrust wall of the outfall tunnel boring machine (TBM). This enabled the two TBMs in their respective directions to launch concurrently, and a reduction in the required footprint, construction time and cost.
Retrieval of tunnel boring machine at outfall cofferdam
The biggest challenge faced during the marine construction was to successfully retrieve the intake and outfall TBMs from deep under the sea. Apart from the main drive, steering cylinder and powerpack commonly used for TBMs, a subsea recovery module and an airlock chamber for hyperbaric intervention were also installed to facilitate the retrieval.
PROJECT DATA
Project Name
Design, Built and Operate First Stage of Tseung Kwan O Desalination Plant
Location
Tseung Kwan O Area 137, Hong Kong
Status of Construction
In progress
Expected Completion
December 2023
Site Area
5.6 hectares
Gross Floor Area
28,571 square metres
Building Height
The Administration Building: 5 storeys; other blocks: 1–2 storeys
Number of Blocks
15
Client/Owner/Developer
Water Supplies Department of the Hong Kong Special Administrative Region Government
Consulting Engineer
Binnies Hong Kong Limited (formerly known as Black & Veatch Hong Kong Limited)
Design Engineer
WSP (ASIA) Limited
Design Checker
Asia Infrastructure Solutions (formerly known as Arcadis Hong Kong Limited)
Main Contractor
AJC Joint Venture (Acciona, S.A., Spain; Jardine Engineering Co. Ltd, Hong Kong; and China State Construction Engineering (Hong Kong) Limited, Hong Kong)
Images
Water Supplies Department
This is an excerpt. The original article is published in
Construction+ Q2 2023 Issue: Infrastructure & Transport.
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