Barwon River Pipe Suspension Bridge & Pylon Removal – Fyansford

Digga Group was engaged by Barwon Asset Solutions, on behalf of Barwon Water, to safely dismantle and remove the deteriorated pipe-carrying suspension bridge spanning the Barwon River at Fyansford. With the structure in a compromised condition directly above the river, between a public walking trail and the Queens Park Golf Course, this was a highly engineered removal that relied on detailed planning, tandem crane lifts and continuous structural monitoring from start to finish.

Site history

The suspension bridge was built in 1961 to carry the Bell Post Hill 350 mm water main across the Barwon River, east of its junction with the Moorabool River, supplying parts of Geelong’s north-west. The structure was partly upgraded in the 1980s, but its load-bearing cables were never replaced. After more than six decades in service, a condition assessment identified significant structural issues and Barwon Water made the decision to take the main permanently out of service and remove the structure to protect the public and river users.

Project overview

Engineering and planning

The independent structural assessment confirmed the bridge was structurally compromised: the main suspension cables were operating below the required safety factor, the deck had deflected around 360 mm at midspan, the north pylon had tilted on its foundation and multiple hanger rods had distorted. With no reliable load path, the structure had to be treated as unpredictable throughout the works.

Digga Group developed a detailed demolition methodology, liaising closely with the client and the structural engineers at every stage and working through each engineering requirement before works began. The methodology was supported by a full lift study, geotechnical bearing assessment for the crane pads, a traffic management plan and a site-specific environmental plan. A survey-based monitoring program using total station measurements and terrestrial laser scanning was in place for every critical stage, with defined hold points and stop-work triggers if any component moved beyond tolerance.

Scope of works

• Site establishment – Access from both banks via the existing Barwon Water site and Queens Park Golf Club, crane pads constructed to the geotechnical design, exclusion zones and spotters in place for the trail and golf course.
• Hazardous materials – Division 6 asbestos audit of the water main joints and flanges from a crane-suspended work box before any cutting.
• Water main removal – The 393 mm cement-lined steel main was rigged, cut and lifted out in sections, with cut ends sealed to prevent any debris entering the river.
• Deck and cable removal – Using engineered temporary lifting beams, the aluminium deck was fully supported by cranes on both banks, separated and lowered in two halves before the suspension cables were cut and lowered one at a time.
• Pylon removal – The twin reinforced concrete pylons were stripped of remaining steelwork, then saw-cut and lifted out in sections by crane under water-suppressed cutting.
• Environmental controls – Floating containment booms, debris capture under every cut and a river-rescue plan in place each day.
• Processing and recycling – All steel, aluminium, wire rope and pipe sorted on the banks, sheared to size and sent to metal recyclers.

Trades engaged and coordinated by Digga Group

Digga Group acted as principal contractor, engaging and coordinating every specialist on the project so the client dealt with a single point of contact:

• Crane hire and lift engineering – four cranes, a crane-suspended work box and an engineered lift study
• Structural monitoring and survey – total station and terrestrial laser scanning with hold-point reporting
• Geotechnical engineering – bearing capacity assessment and crane pad design
• Structural engineers – methodology review and temporary lifting beam design
• Traffic and pedestrian management – control of the shared trail and site access
• Licensed occupational hygienist – Division 6 hazardous materials audit
• Electrical spotter – on site for the full duration due to adjacent overhead power lines
• EWP and access equipment hire – 60 ft knuckle-boom EWP
• Licensed wildlife handler – on call for snakes and riparian fauna
• Metal and concrete recyclers – processing of all steel, aluminium, wire rope, pipe and concrete

Safety and the community

Working above a river, beside an active walking trail and on a golf course called for tight coordination. Machinery was mobilised outside playing hours, spotters controlled the tee boxes and trail during every lift, an electrical spotter was on duty because of nearby overhead power lines, and a river-rescue plan was in place throughout. The project was completed within the programmed seven days on site with zero injuries and zero variations, and the river and surrounding paths were returned to the community.

Recycling and resource recovery

All structural materials removed from the bridge, including aluminium decking, steel wire ropes, hanger rods and the steel water main, were separated on site and delivered to approved metal recyclers, and the reinforced concrete from the pylons was taken to a concrete recycling facility.

Plant and equipment

Four cranes working from both riverbanks with a crane-suspended work box, a concrete demolition saw, a 60 ft knuckle-boom EWP, an 8-tonne excavator with shear attachment, a skid steer and pad-foot roller for crane pad construction, and hook trucks with bins.

The completed site