Victoria’s State Emergency Service (VICSES) gave the alert for West Wodonga, just off the Victorian/New South Wales state border, on 6 October after news broke of a potential pit capture at a nearby sand quarry.
Its message read: “A section of the sand quarry in Wodonga West … has breached leading to extensive flooding into the quarry and potentially into the surrounding area.”
Nearby residents moved to safer areas, access to the site was restricted and three local roads were closed.
The message noted: “Emergency Services do not know exactly what may occur due to the flooding. Technical specialists are working towards making the site safe and reduce further damage.
Potential damage to “buildings and infrastructure” as a result of the flooding or further collapse was also identified.
VICSES spokesman Brian Wright told the Border Mail rising water had posed a threat to a gas pipe and powerlines attached to transmission towers bordering the quarry.
However, Hugo Armstrong, a spokesman for power company AusNet was quoted as saying: “Even if for safety reasons we had to turn off the power that runs through those towers it doesn’t mean Wodonga would go black.”
Danger of “pit capture”
Natural resource management body Goulburn Broken Catchment Management Authority (CMA) oversees efforts to protect water resources in an area of northern Victoria.
Although Wodonga West does not fall into its catchment area, in the past it has investigated risks posed by large-scale quarrying in the event of a deluge.
When asked by Quarry for advice on managing flood risks to infrastructure, a Goulburn Broken CMA spokesperson said such matters are the responsibility of the Department of Economic Development, Jobs, Transport and Resources’ Earth Resources Regulation branch.
The spokesperson cited a 2014 review of floodplain mining risks, based on a large body of national and international case studies and research, which stated: “Major floodplain mining impacts can occur if, during flooding, the stream creates a new channel through the pit.
“If this (known as pit capture) happens, physical impacts can include river bed degradation, bank erosion and river channel widening.”
Pit capture can also lead to rivers changing their courses and infrastructure in the surrounding area may be damaged as the water changes its route.
The likelihood of pit capture is increased by factors such as flow velocity, proximity of the pit to a waterway and the depth of the pit relative to the river, according to the review.
Quarry approached Wodonga Quarries, where it is understood the flooding occurred, for comment but no one from the business had responded at the time of publication.