Coffs Harbour Bypass Drainage

Trazlbat is delivering the longitudinal and transverse stormwater drainage infrastructure for a 14-kilometre section of the new Coffs Harbour Bypass, forming part of a major highway upgrade being delivered by the Ferrovial Gamuda Joint Venture for Transport for NSW. The works involve the installation of reinforced concrete pipe (RCP) and high-density polypropylene (HDPP) drainage systems, along with a wide range of precast pits, culverts, and headwalls.

The drainage scope supports the broader construction of a new four-lane highway designed to bypass Coffs Harbour CBD, improving regional traffic flow, safety, and long-term transport efficiency.

Scope of Works

• Installation of approximately 1,320 metres of stormwater pipeline, including RCP and HDPP pipework in varying diameters.
• Supply and installation of precast concrete pits ranging from DN375 to DN2100.
• Construction and installation of transverse and longitudinal culverts and associated headwalls.
• Earthworks including excavation, trenching, bedding, backfilling, and compaction for drainage infrastructure.
• Installation of stormwater drainage systems integrated with the new highway alignment.
• Construction of reinforced concrete drainage structures, including pit bases and headwall transitions.
• Protection and management of existing underground utilities throughout construction.
• Quality assurance testing and inspection of installed drainage infrastructure.
• Site reinstatement and environmental management of all disturbed areas.

Project Challenges

• Managing construction activities in periods of heavy rainfall and wet weather conditions.
• Undertaking deep excavations requiring robust shoring, staging, and safety controls.
• Excavation in rock conditions, requiring specialised equipment and methodologies.
• Working in proximity to live underground services, including electrical conduits and existing utilities.
• Coordinating drainage installation within a large-scale, active highway construction environment.
• Maintaining programme efficiency while working across multiple work fronts and interfaces.