Mandurah Bridge

Mandurah Bridge

Client: Georgiou Group

Location: Mandurah, WA

Duration: October 2017 – February 2018

Structure Overview

Constructed in 1953, the multi-tiered bridge structure over estuarine waters was an iconic landmark in the City of Mandurah. The 23-span bridge was supported by concrete piles and headstocks. The top tier consisted of a two lane road for vehicle traffic and a 1.8 metre pedestrian walkway, comprising of large 600mm diameter timber bearers, overlayed with timber stingers and a concrete pavement.

The lower tier was an underbridge fishing platform running the

entire length with a central opening for vessel passage, constructed of both steel and timber decking.

Scope of Works

Mainline was engaged by Georgiou Group to demolish the 192m concrete and timber composite Mandurah Bridge over estuary water.

The demolition scope included:

• Complete demolition of the existing bridge structure.
• Existing bridge piles not used in the permanent works removed at least 300mm below estuary bed level.
• The first 10 bays of the bridge were to have piles cut above water level for future transformation into a fishing platform; and
• Careful removal of timber, light poles and some concrete elements of the bridge for delivery to the City of Mandurah.

Equipment Deployed

The bridge demolition was a sensitive operation with limited work front space. Careful selection and design of the plant and machinery was required. Custom made specialised equipment included:

• Mainline Hold and Cut Saw
• Hydraulic Clamshell Grab
• Air Bags, for landing and floating
• Silt Curtain for Marine Environmental control

Plant:

• Hitachi 350LCH Excavator
• Hitachi 210LCH Excavator
• Sumitomo SH200LPC Telescopic Excavator
• JCB 220 Long Reach Excavator
• Komatsu WA320 Loader
• 5 Tonne Forklift
• 6 metre work boat
• 10 metre Boat Work Platform
• Various Concrete/Road Saws

Project Highlights

• Winner – 2018 World Demolition Award
• 2019 WA Work Health and Safety Excellence Award
• Minister for Planning commendation
• Proprietary FellnFloat system eliminating heavy lift crane and barge operations
• Greater than 99% of materials recycled or repurposed
• Zero impact on environment
• Completed on time with zero HSE incidences

Operational Challenges and Solutions

Whilst a challenging environment to operate in, we turned the water into an asset by:

• Introducing flotation devices for capture, transport, beaching and rolling of large concrete elements up to 60 tonnes, was the key driver, made possible by Mainline’s custom made roller flotation airbags.
• Developed a low speed, high torque, hold, rotate and cut machine, fitted to the 18m telescopic boom, capable of cutting piles 500mm+ below seabed level from bridge deck.

The brief was successfully executed over the four-month lead up to the start of works and ran smoothly, without any disruptions, from day one to completion.