City Tunnel’s Internal Condition Assessment 

Introduction

Managing critical infrastructure like water supply pipes requires proactive maintenance to ensure reliability and longevity. This case study examines the processes and technology we implemented to gain access and inspect the City Tunnel, a crucial component of Sydney’s water distribution network.  

The assessment aimed to pre-emptively manage infrastructure, prevent failures, enhance operational efficiency and comply with evolving regulatory standards. 

Solution 

A comprehensive solution was implemented to address these challenges. 

The project began with the isolation of 16 kilometres of pipeline by strategically closing valves. This isolation allowed for controlled access, crucial for conducting thorough assessments and executing necessary maintenance activities.  

Dewatering techniques, including the use of wellpoints and deep wells, were employed to remove water from the isolated sections. This step was essential to create a safe working environment inside the pipe, enabling personnel to perform inspections and repairs effectively. 

A detailed ventilation plan was developed and executed to ensure a safe working environment within the confined space of the pipe. A forced air ventilation system was installed, with ducts and mechanical equipment that served to regulate air quality and mitigate potential hazards such as airborne contaminants.  

The system included provisions for push-pull ventilation, which effectively circulated air to maintain safe atmospheric conditions. Special attention was given to controlling hazardous chemicals and implementing regular maintenance procedures to uphold operational safety and manage air quality effectively. 

To facilitate safe entry and exit for maintenance personnel, custom-made swinging stages or personnel lifts were designed, built and installed. These bespoke platforms were suspended from multiple points within the pipe, equipped with necessary safety features. We also wrote a comprehensive rescue procedure to manage emergencies effectively. The design and implementation of this access equipment ensured that previously inaccessible sections of the pipe could be safely accessed and inspected. 

Finally, a robust communication network spanning the 16-kilometre length of the pipe was established to facilitate seamless information exchange. Two-way radios or wireless headsets enabled communication among team members, allowing real-time updates on work progress and safety concerns.  

Externally, radio or phone connections were utilised with standby personnel to ensure continuous support and coordination. An integrated communication hub served as a central control point, managing all communications and enabling swift responses to emergencies through an established alert system.