Remediation works on the Mortlock Bridge in Northam were completed by Arc Infrastructure’s Major Projects team, alongside contractors Rosscorp and Duratec, in late March.
As the works were located within a registered Aboriginal cultural heritage site, Arc was required to seek approval from local Traditional Owners to complete the works. Approval conditions included a requirement for two monitors to be present during any ground disturbing works.
Two monitors from the Ballardong people were onsite at a time, accompanied by an archaeologist from cultural heritage service provider Archae-aus. In total 12 different monitors were involved in the completion of the project over a period of six days.
Arc Infrastructure Aboriginal Heritage Advisor Craig Deetlefs said the successful conclusion of the project was an example of how we are working respectfully together with the Traditional Owners on whose land our infrastructure is located.
“Our team welcomed the opportunity to work with the onsite monitors during the works. The positive feedback we received from the Traditional Owners at the end of the project reinforced the value of having them involved,” Mr Deetlefs said.
One of the main concerns for the work needed to be undertaken was the requirement for the construction of a temporary causeway. Causeways are similar to a temporary road and are used by a construction team in areas where there is unsuitable land (such as a muddy riverbed) to create a strong and stable foundation during works. A causeway is constructed by initially laying down a geofabric, followed by a geogrid mesh which then holds in place rocks and gravel which are compacted to form a firm surface.
Three pipes were featured in this causeway to allow continued flow of the river during the works period. The monitors were required to be onsite during both the construction and removal of the temporary causeway, as potentially ground disturbing activities.
The remediation works were required to repair the natural degradation of the bridge’s concrete piers. The process for the remediation works could commence following the causeway construction. Initially the bridge was propped up to take the weight of the structure and as an operational line, customer’s trains, to allow works on the damaged pier to continue.
A high-pressure water blast was then used to remove the old concrete from the damaged pier, so the team and supporting contractors could cut away a damaged metal reinforcement from within the concrete pier, and then weld on the new reinforcements. Once welded, the team could form up and pour the new concrete. These steps were completed twice so the pier was only ever partially deconstructed.
General Manager of Works Delivery Dan Ellis said he was pleased with the project outcomes, both in terms of the scope of works completed as well as the engagement with the Ballardong people.
“Building trust and positive relationships with local Traditional Owners is a priority for Arc,” Mr Ellis said.
“We have a dedicated Aboriginal Engagement initiative identifying ways to create connections and work collaboratively.
“Working with monitors on projects like this allows us to complete our critical works, while preserving our rich cultural heritage.”
We would like to acknowledge the Ballardong people who are the Traditional Custodians of the land on which we worked to complete this project.
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