A PLAN to build a sewerage network across the Southern Moreton Bay Islands could cost close to $1 billion — with potential rate hikes of thousands of dollars a year — according to new analysis by Redland City councillor Shane Rendalls.
Cr Rendalls has released a discussion paper examining the potential cost of installing a wastewater system across the islands, warning the scale of the project could make it politically and financially difficult to deliver.
“Based on an estimated base cost of $66,000 per lot for sewerage on the mainland, the indicative cost of sewering Southern Moreton Bay Islands (SMBI) is calculated at approaching $1billion,” the report states.
The estimate equates to roughly $92,000 per residential lot across the islands.
Cr Rendalls stressed the figures were high-level estimates only and were intended to highlight the scale of the challenge and start a community conversation about whether sewering the islands is even realistic.
Currently, most island homes rely on onsite septic and wastewater systems, unlike mainland suburbs connected to the city’s sewer network.
But installing a centralised wastewater system would require new treatment plants, extensive pipe networks and possibly multiple facilities across the islands.
Cr Rendalls said even proposals to pump wastewater to the mainland would not solve the problem.
“Firstly, building a bridge to transfer wastewater to the mainland will only add more costs as mainland wastewater treatment plants are running at capacity,” the report states.
“The wastewater still needs to be treated somewhere, and this somewhere will require a new and expensive wastewater treatment facility.”
The analysis outlines several funding scenarios — including borrowing money, government grants or spreading the cost across all Redlands ratepayers.
Under a loan-funded model, mainland ratepayers could face increases of about $1,300 per year, while island residents could see additional costs exceeding $9,000 annually, plus a $5,501 connection fee.
Cr Rendalls said such costs were unlikely to gain support.
“Clearly, the cost of sewering SMBI without grant funding is unaffordable, even if the cost is distributed across all Redlands ratepayers,” he wrote.
“Redland ratepayers on the mainland would not accept a $1300+ increase in their rates to pay for sewerage on SMBI.
“SMBI residents would not be able to do it alone at an annual cost of $9,000+ and a one-off connection fee of $5,501.”
Even if the state or federal government funded the construction, ongoing costs would remain.
Under a grant-funded model, island residents could still face around $1,217 in additional annual charges, along with the connection fee.
Cr Rendalls said depreciation costs for new infrastructure were unavoidable.
“The cost of depreciation is unavoidable. It is a legislative requirement that all councils in Queensland make cash allocations for the depreciation of their capital assets,” he said.
The councillor said the discussion paper was not an official council study and had not been endorsed by Redland City Council, but was intended to start a broader conversation with island residents.
“This analysis has been undertaken by me on the information readily available to me; it is solely the result of my work,” he said.
“It is the commencement of a journey.”
Cr Rendalls said the next step would be community consultation across the islands to gauge whether residents support sewering the islands — and if they are willing to pay for it.
If there is support, council could then lobby state and federal governments to fund a full feasibility study.
“Put simply, if there is strong local opposition to funding a wastewater system for SMBI from local residents, why take the issue any further,” he said.
