Structural improvement of sewers and drains, Hong Kong

NEC has been used for the complex task of structurally upgrading nearly 3 km of large diameter drains and sewers in Hong Kong. The Drainage Services Department (DSD) of the Government of the Hong Kong Special Administrative Region of China awarded the work to contractor Hing and Cheong in May 2021 under an NEC3 Engineering and Construction Contract (ECC) Option C (target contract with activity schedule). The project was successfully completed on programme and budget in May 2024.

The contract was part of a prioritised programme of replacement and rehabilitation works which DSD initiated in 2015 to enhance the operation and reliability of its 4,200 km network of public underground drains and sewers. It involved structural improvements to around 1.9 km of large diameter drains and 1 km of large diameter sewers in Hong Kong Island, Kwun Tong, Sai Kung and Tai Po. 

Mostly trenchless techniques were used, including ultra-violet-light cured-in-place pipe and slip-lining with glass-reinforced plastic (GRP) pipes. Innovative technologies to minimise confined-space working included the use of drones and laser scanning to survey the pipes remotely. A pipe-jacking system was adopted which required no manual handling for lowering GRP liners, adjusting alignment or jacking, and a wire-sawing machine was used for temporary removal of an access shaft. Any work that did require people to enter the pipes was continually monitored with real-time artificial-intelligence (AI) cameras and smart helmets.

The NEC project manager was the principal project coordinator of DSD’s Planning and Rehabilitation Division and the NEC supervisor was Binnies Hong Kong.

Risks and challenges

Saul Chan, principal project coordinator of DSD’s Planning and Rehabilitation Division, says the project faced numerous risks and challenges. ‘These included the presence of noxious gases such as hydrogen sulphide, high water levels and various safety hazards associated with working in underground confined spaces.’

He says there was also a significant amount of uncharted drainage as well as uncertainties as to pipe condition, such as intruding utility pipes. ‘Heavy silting and blockages were also found in many of the sewers and drains.’

Chan says other challenges included limited working space on the surface and restricted working hours for temporary traffic arrangements. ‘We also had to deal with tidal effects and difficulties in maintaining the existing flows, as well as global logistics issues and shortages of materials during the Covid-19 pandemic.’

Collaborative approach

He says the project team worked collaboratively and seamlessly to overcome the many risks and challenges in line with the NEC requirement to act in a ‘sprit of mutual trust and co-operation’. ‘The employer, project manager, supervisor and contractor agreed common project objectives in a joint partnering workshop. This led to adopting innovative solutions to complete the project quickly, cost-effectively and safely, as well as to minimise any environmental and public impacts.’

Chan says NEC-inspired collaboration and NEC early warning processes were vital in devising swift and effective solutions when problems were encountered during the works. ‘In addition to regular site progress meetings and risk reduction meetings, special task forces were set up to discuss problems encountered and drive for innovative solutions. This ensured issues were promptly resolved for smooth project delivery.’ 

He says good communications and co-operation also extended to all other stakeholders. ‘These included the traffic authorities, subcontractors, future maintenance agent, utility undertakings and adjacent residents. This was essential to streamline project delivery.’ 

Innovative technologies

Chan says the contractor deployed drone surveys and three-dimensional (3D) laser scanning for precise measurements of the internal dimensions and profiles of the existing pipes without needing in-person reconnaissance. ‘A 3D model with point cloud data was then created to confirm the precise pipe profile, which was vital for tailor-made liner fabrication.’ 

He says innovative techniques were also developed for pipe-jacking the GRP slip-liners. ‘A prefabricated steel working platform was erected for workers and a mechanical jacking system with a guide rail for installing the liners was used. This significantly minimised the need for confined-space working and manual handling, thus enhancing productivity and safety.’

Chan says a concrete wire-sawing machine was deployed for temporary demolition and removal of a concrete access shaft to create space for pipe rehabilitation. ‘This significantly reduced time and workers’ involvement and minimised environmental nuisance. The shaft was stored and replaced during reinstatement.’ 

He adds that real-time AI cameras and smart helmets were used for monitoring all confined space work on site and in the office via internet connections. ‘The innovative technologies adopted in this contract have become essential provisions in other pipe rehabilitation contracts.’

Excellent safety record

Chan concludes that the success of the project is a testament to the power of NEC-inspired collaboration and communication in achieving project outcomes. ‘Despite the many challenges, the rehabilitation works progressed well ahead of the programme, with zero accidents.’

He says the outstanding safety performance and innovative ideas led to the contractor winning four safety awards in the 21st Hong Kong Occupational Safety and Health Awards 2022, including the grand OSH Enhancement Program Awards – Silver Award. 

‘By adopting a collaborative approach and implementing NEC clause 10.1 on mutual trust and co-operation, the project team demonstrated a successful model in achieving project objectives in a safe, cost-effective and innovative manner while minimising environmental impact.’

Benefits of using NEC

• NEC requirement to act in a ‘spirit of mutual trust and co-operation’ resulted in the project team working collaboratively and seamlessly to overcome risks and challenges.
• NEC-inspired collaboration included co-operating to use advanced technologies and innovative solutions to minimise confined-space working and cope with the various site constraints.
• NEC early warning processes were indispensable in formulating swift and effective solutions when problems were encountered during the works.