Aurecon helps to expand the Tai Po Water Treatment Works for the people of Hong Kong

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• Site formation works and permanent works design
• 3D underground profiles for a thorough geological profile
• Awarded International Design for Safety Awards 2019 Bronze Award

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The expansion of the Tai Po Water Treatment Works project represents the vision of the Hong Kong Water Supplies Department (WSD), to enhance the reliability and flexibility of the water supply and distribution system in Hong Kong.

To provide reliable potable water supply to the people of Hong Kong, WSD expanded the treatment capacity of the Tai Po Water Treatment Works from 400,000 m³ per day to 800,000 m³ per day.

Upon completion of the project, the fresh water supply zone of Tai Po Water Treatment Works will cover Tai Po, West and Central Kowloon, and the Central and Western districts of the Hong Kong Island.

Aurecon provided design engineering services for all temporary works designs required for the site formation works, and parts of the permanent works design for expansion of the Tai Po Water Treatment Works. Aurecon’s ground engineering and structural engineering teams delivered smart, cost-effective solutions, with a constant focus on safety in design.

Ensuring safety in design

Safety in design is the integration of control measures early in the design process to eliminate or minimise risks to health and safety throughout the life of a structure being designed.

Aurecon is committed to providing cost-effective engineering design solutions by using a safety in design approach on projects.

This approach was used to design the temporary excavation and lateral support system for the challenging Dissolved Air Floatation II Building (DAF II) at the treatment works. The existing building was on a shallow foundation with sensitive utilities, including a water main, storm drain, chlorine pipe and water tunnels.

The confined spaces and the control of impacts on existing adjacent sensitive structures during the deep excavation works were the key challenges.

To address these challenges, Aurecon:

• generated a 3D underground profile of the excavation and lateral support works to gain a better understanding of the geological profile before works commenced.
• designed the steel elements of the deep excavation works to be prefabricated offsite to reduce the amount of onsite welding in confined spaces.
• used circular hollow sections as the main struts so that a smaller number of king posts were required for the building supports. This opened the amount of work space available to contractors which in turn reduced the risk of collision between people and multiple structures.

These achievements were recognised by the Lighthouse Club, with Aurecon awarded its International Design for Safety Awards 2019 Bronze Award.

Aurecon recognises that these achievements were made possible because of the collaborative relationship with WSD. In the excavation and lateral support works design, all potential hazards were identified and addressed early in the design stage which helped to reduce the whole lifecycle safety risk and the potential for injuries.

Robust yet economical solutions

The project involved upgrading the existing facilities and constructing additional water treatment facilities at the plant site. It also increased the pumping capacities of the raw water and fresh water pumping stations.

The new facilities were constructed close to the existing facilities and in some cases, were immediately adjacent to building structures. Care was taken to mitigate the ground movement risks to those existing buildings during the design and construction of the new structures.

This focus alleviated the two main ground engineering challenges:

• Ground movement and subsequent structure movement due to the excavations.
• Global stability of the existing structures due to unbalanced earth pressures on either side of the structures.

As part of the excavation and lateral support works, Aurecon designed the ground engineering to redistribute unbalanced earth pressure acting on existing buildings. Protection was also provided to the critical supporting points of the existing buildings.

Sharing the same vision and goal, the entire project team that contributed to the expansion of the Tai Po Water Treatment Works forged ahead with the substantial effort to collaborate and improve the infrastructure that will service residents of Hong Kong now and into the future.