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Ageing sewage plant set for overhaul

An environmental impact statement has been lodged with the ACT government to assess the impact of sewage discharge into Lake Burley Griffin as part of a major upgrade to Queanbeyan’s ageing sewage treatment plant.

The project involves the upgrade of the Queanbeyan sewage treatment plant at Jerrabomberra. The existing plant is currently over its initial capacity to service a population of 34,500. The proposed upgrade services a population of 75,000.

A scoping report prepared by Queanbeyan-Palerang Regional Council in July 2019 looked at a number of options for the plant, with a recommendation to upgrade the plant on its current site. The estimated cost to design and build the new plant is $140 million.

The NSW government previously awarded a $3 million grant towards development of a detailed business case for the upgrade.

The plant was constructed in the mid-1930s to treat sewage from Queanbeyan prior to discharge into the Molonglo River. The council upgraded it on a number of occasions, with the last upgrade taking place in the mid-1980s. While maintenance works are regularly undertaken, the plant is no longer fit-for-purpose. 

A significant works program is required to address issues including structural failure, equipment obsolescence, maintenance issues and work health and safety issues, as well as bring the treatment process in line with modern practices.

Queanbeyan-Palerang Regional Council said that the condition of the existing infrastructure has deteriorated, and there is little remaining useful life for the existing treatment plant. It is also becoming more difficult to operate the existing plant to meet licence conditions.

Additional contamination assessments will need to be undertaken on the site due to the burial of solids and screenings. This likely includes stockpiles of biosolids — which may contain metals — as well as wet and dry sludges, screens and grit, onsite material burial, and possibly asbestos material.

Queanbeyan-Palerang Regional Council CEO Peter Tegart said that the council is mindful of water quality and environmental flows into the Molonglo River and Lake Burley Griffin.

“Lodgement of the [environmental impact statement] allows us to begin to expand our community engagement activities — to get more people to understand the need for the upgrade, how we intend to deliver it, what the costs and benefits of the new plant will be, and gain stakeholder and community input into key project decisions,” he said.

The report also warned that lagoons within the plant may fail due to severe flooding, as occurred in 2010. In such an event, the discharge could make its way from the Molonglo River into Lake Burley Griffin.

Three sewage plants are above Lake Burley Griffin, along with significant contributions from rural and urban runoff, particularly during summer rainstorms, all have contributed to a long-term pollution problem in the lake.

The public consultation period for the draft environmental impact statement is 35 working days from 18 January 2021 and to 9 March 2021.