Hobart's largest wastewater treatment plant — next to the site of the proposed AFL stadium — has regularly breached environmental standards for discharging chemicals into the River Derwent, creating a "high risk" of toxicity.
The ongoing environmental problems with the Macquarie Point Sewage Treatment Plant were detailed in TasWater's business case for the plant's proposed relocation to Selfs Point, further up the Derwent, with more modern infrastructure.
Infrastructure Minister Michael Ferguson described the plant's relocation as "vital" for Macquarie Point's development — which includes the stadium — to give investors confidence in the project.
He said 2025 would be "a perfect timeframe".
Its relocation has long been proposed, but was delayed due to a funding dispute between TasWater and the state government, which has since been resolved.
The relocation business case — obtained by the ABC under Right to Information — outlines how TasWater failed to meet a 2016 regulatory commitment it made to the Environment Protection Authority (EPA) to improve environmental compliance for the state's larger wastewater treatment plants.
The Macquarie Point plant — Hobart's largest, treating waste from 16,000 properties — has regular breaches of environmental protection notices and is among the TasWater sites contributing to the government-owned business failing to meet its 2016 commitment.
Chlorine, nitrogen levels fail to meet compliance
In 2020-21, the plant failed to meet EPA compliance for residual chlorine entering the Derwent under Macquarie Wharf in 28.8 per cent of tests.
This improved in the next financial year after an upgrade, but total nitrogen levels significantly worsened, failing to meet compliance in 61.5 per cent of tests in 2021-22.
The business case highlighted the site's various flaws.
"In addition, there is insufficient mixing at the outfall to meet dilution requirements for total nitrogen, total ammonia (ecosystem health) and total phosphorus," the business case reads.
Plant move cost expected to grow
TasWater was given a staged $100 million grant from the state government, starting in 2019, for the plant to be relocated after years of disputes over who would fund it.
This was in the context of upcoming development at Macquarie Point — which was initially residential before a new proposal for an AFL stadium — and the Hobart City Deal.
But the plant's relocation is yet to be guaranteed, with TasWater highlighting the risk that the cost could be greater than expected, resulting in the need to find more funding, which could cause "substantial delays".
In November, TasWater chief executive officer George Theo confirmed the cost of the relocation will exceed the $140 million estimate from 2016, but said the exact figure was commercial in confidence.
TasWater also redacted the project costs in the business case, again citing commercial in confidence. The state government could be required to chip in 71 per cent of the cost should it run over budget, as per the grant agreement.
The business case notes that the plant must be relocated in 2025 to avoid failing to meet further commitments to the EPA, and for development plans at Macquarie Point to progress.
TasWater concerned environmental approvals could delay project
The business case chose a "staged development" of Selfs Point as its preferred option to relocate the Macquarie Point plant.
This includes expanding the existing Selfs Point plant for an additional 12-million-litre-per-day capacity, then further works by 2040 to reach a total capacity at the site for 26 million litres per day.
A new local outfall pipe to release treated waste will be needed at Selfs Point, 200 metres from the existing outfall, which runs under petrochemical sites.
A 4.5-kilometre rising main will also be constructed from Macquarie Point to Selfs Point, with the majority to run alongside the pipes to the Blinking Billy outfall in Sandy Bay, which will also be upgraded.The majority of Selfs Point effluent is discharged at Blinking Billy.
A new sewage pump station and emergency storage would be built at Macquarie Point, but TasWater redacted the exact location of these, and said discussions with landholders was ongoing.
TasWater is finalising an environmental impact statement for the EPA for the entire project, which it expects will be submitted by the end of March.
"TasWater is now undertaking detailed design work to enable public consultation and the required planning and environmental approvals through 2023, following this work, a final proposal and budget will be provided to the TasWater board for approval."TasWater said in a statement.
Concerns about TasWater's refusal to detail costs
While the sewage treatment plant is still pictured in the latest indicative images of the proposed Macquarie Point stadium, a Derwent estuary expert says it was essential that it be relocated sooner rather than later.
Christine Coughanowr, who led the Derwent Estuary Program for 20 years, said the levels of chemicals — particularly chlorine — being discharged by the plant were surprising, and improving Hobart's sewage infrastructure was essential.
"Centralising and upgrading treatment to the tertiary level is certainly a big plus," she said.
"What's the most cost-effective way? I'm not sure, but it seems crazy to leave a sewage treatment plant in the city's best, prime real estate.
"It's going to have to be moved eventually. The only question is who pays, and when."
TasWater's ongoing refusal to detail the latest cost estimates for the relocation raised concerns with University of Tasmania right to information expert Rick Snell.
He said it appeared some public authorities were not weighing up the public interest test when withholding information on a commercial-in-confidence basis.
"TasWater doesn't have any competitors," Dr Snell said.
"All around Australia if this went out to tender you would know what the starting proposition is. At some stage, they're going to have to announce how much they'll put into it.
"The arguments for commercial confidentiality may be high, but for a project like this, the public interest argument may be higher."
The state government and TasWater reiterated their view that it would be "irresponsible" to release the latest costings as it could "compromise the market testing" during the tender process.
Mr Ferguson said the government would be willing to increase its funding for the relocation project should it encounter cost overruns.
"Our money is real. We're prepared to provide more if required, noting TasWater's final business case hasn't yet been approved by the board," he said.
"This is a very, very exciting project not only for the environmental benefits … but also to clear away odour and the visual improvement of that amenity will be really substantial, and will really pave the way for incredible investment at Macquarie Point for a range of uses."
