CCFWA Earth Awards 2018

Category 1 Finalist

CCF EARTH AWARDS – Excellence in Civil Construction

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Client: Department of Biodiversity, Conservation and Attractions

Woodbridge Riverside Park is a popular recreation site for the local community. The existing dilapidated platform at Riverside Park, constructed from asbestos and concrete, had been assessed as high-risk to public safety and the area had been fenced off for over two years. The Swan River or “Derbal Yerrigan” in Nyoongar language is one of the most significant Aboriginal Cultural Sites in the Perth region. The project would require Cultural Monitors to be present during the excavation stages to look for uncovered artefacts and to ensure that the construction techniques would be conducted with minimal impact to the Swan River and its spiritual and environmental values. The project required a contractor experienced in working around the Swan River. MMM (WA) has been repairing, rebuilding and creating erosion control to degraded sections of river foreshore around the Swan & Canning Rivers for approximately 18 years. MMM (WA) supplied a team of highly skilled, qualified and experienced personnel, who have had many years working together on similar projects. The site had various restrictions due to exclusion zones from high voltage power and tree protection. High risk tasks, including removal of asbestos piling from the river and the excavation and treatment of acid sulphate soil, were carried out before the rebuilding tasks could be completed. The works included stormwater drainage, construction of 110 metres of laterite revetment, installation of a piled viewing deck, beach, gabion walls and landscaping of the 2500m2 area.

The Department of Biodiversity, Conservation and Attractions’ highest priority on this project was to declare the site asbestos-free. The past practice of encapsulating the material was no longer acceptable, so the requirement to completely remove and dispose of 30m x 1.8m sheets of asbestos bedded into the river required meticulous management. The scheduling of events and subcontractors was the key to this project. The Principal gave permission to store the drainage components on the site from the last date of delivery before Christmas Closure. The works were able to commence on site possession, being 2 January 2018. Another crucial scheduling event was the installation of the armour rock toe protection for the revetment, which had to completed before the piling was installed. The excavation for the toe scour protection required meticulous operator skill and execution. The entire toe scour had to be built extremely accurately to the design to enable the piling to be installed to the lines and levels required to support the viewing deck. Working around trees on the riverbank required attention to care and detail. Some hand excavation was required where there were overhanging trees. MMM (WA) has an 8 tonne Mecalac excavator in the fleet, which has a boom that folds down to approximately the height of the cab. This excavator has proven invaluable on these types of works in the past. On one section the design was modified slightly due to the high volume of tree roots that would have been disturbed to achieve the revetment height. The site also had a significant amount of Tree Protection Zone set up with 1.8m fencing. These areas were mulched and watered regularly in accordance with the arborist’s recommendations. This also had an impact on the movement of the machinery into the areas of construction of the revetment. Scheduling due to tidal movements was paramount. Some elements of the works required staging around low tide, however due to the scope of the project and time constraints this was not always possible, and work carried on with varying tide levels wherever possible.

“The requirement to completely remove and dispose of 30m x 1.8m sheets of asbestos bedded into the river required meticulous management.”

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