Water Corp suggested new $1 billion desalination plant over mining fears, documents reveal

Western Australia’s water utility is so concerned about the risk posed to Perth’s water supplies by Alcoa’s bauxite mining in catchment areas that it has proposed replacing the 64-year-old, 25-gigalitre Serpentine Dam with a $1 billion desalination plant.

That revelation was contained in a trove of internal Water Corporation and government documents obtained by news website Boiling Cold under Freedom of Information laws.

Alcoa’s bauxite mining operations near Serpentine Dam have raised concerns within WA’s water utility.Credit: 9News Perth

Those documents also show Water Corporation ejected itself from any decision-making capacity on committees charged with assessing Alcoa’s bauxite strip-mining activities.

They also reveal a Water Corporation claim that other agencies tasked with approving Alcoa’s mining activities – the departments of Jobs, Tourism, Science and Industry, and Water and Environmental Regulations – have been instructed to prioritise social and economic factors above water source protection.

According to the documents, Alcoa’s 2023-27 mining management plan comprises 400 hectares of clearing in drinking water catchments in the hills, including near the Serpentine dams. Water Corp said 73 per cent of this proposed clearing was in previously protected areas.

It is this plan that has sent the authority’s alarm bells ringing over the risks to the Serpentine and Serpentine Pipehead dams.

Previously reported FOI documents show Water Corporation thinks the risk of contamination of water reservoirs from Alcoa’s 2023-27 mining plan is “considered certain”.

This was due to the annual average of 38 drainage failures, 130 hydrocarbon spills and 28 turbidity (water clarity) events the company reported between 2017 and 2022.

These new documents detail the level of concern at the top echelons of the organisation.

Water Corp chief executive Pat Donovan issued a warning to its board in May 2024 of what could happen in the event of a contamination of the pipehead dam.

He said the number of impacted customers would grow from 1000 in the first two hours, to 10,000 within six hours, and “well over 100,000 customers beyond six hours”.

Donovan said, depending on the contamination, it could result in health authorities issuing advice for Perth homes to boil their water, or Water Corporation needing to supply bottled water to impacted homes.

Water Corp executives continued to press the issue with its board as late as October in a report that suggested the loss of the Serpentine Main Dam would reduce Perth’s water supply by some 28 billion litres, or 7 per cent of total drinking water supplied through Perth’s water network.

These concerns resulted in Water Corp advice to its board and government to build in contingencies to mitigate any impact to the water supply which included removing Serpentine Dam as a water supply entirely.

In December 2023 a report from Water Corporation’s General Manager of Operations suggested it would cost the state $1 billion to replace the 25 gigalitre dam with a new desalination train at either the Perth Seawater or Alkimos Desalination plant.

An Alcoa spokesman denied its activities posed a threat to Perth’s water supply – pointing to the fact it had operated for more than six decades without a water quality incident.

“Alcoa continues to comply with the strict conditions put in place by the state government as part of the Alcoa Transitional Approvals Framework, including additional management measures for environmental factors such as water,” he said.

“We have also elected to defer mining activity in the Reservoir Protection Zone as part of the Revised Proposal for future mining activities to further evidence our commitment to continuing to operate responsibly.”

Alcoa has made a $100 million guarantee to the state government which it said demonstrated its confidence it would not impact drinking water supplies.

The company also immediately stopped mining within one kilometre of dams and stopped clearing of land with steep slopes within two kilometres.

‘Reputational risk’

Donovan’s May report to his board shows Water Corp’s concerns about Alcoa’s mining to Perth’s water supply and that it removed itself from any decision-making authority in assessing mining proposals to protect its reputation.

“Alcoa’s recent approval ... increases drinking water quality risks,” Donovan told the board.

He said Water Corp recommended to the Department of Jobs, Tourism, Science and Industry its role needed to change to being in an advisory capacity only, where it tabled advice proactively “and without prejudice.”

“This preferred option recognises that Water Corporation does not have a regulatory function but does carry the reputational risk of being party to approving mining activity which ultimately impacts its operations,” he said.

Bureaucrats ‘told to prioritise mining’

Alcoa employs more than 4000 people in WA, and any decision that could impact its viability would send shockwaves through the economy.

Assessment of Alcoa’s mining proposals is transitioning to a standardised Environmental Protection Authority process, which could take until 2028.

In December 2023, Alcoa was granted an exemption from stopping its activities while the EPA conducted its assessment.

That same month, Alcoa wrote to Premier Roger Cook warning it would be economically unviable for the company to completely retreat from catchment areas.

While that was occurring, Water Corp was also voicing its concerns about the exemption order.

In a response to Alcoa’s 2023-27 mine management plan presented to the Water Corp board, it lashed the government for not including its advice in the exemption.

It also claimed the departments responsible for oversight had been given instructions to not impact social or economic factors.

“Water Corporation would like to highlight that its advice has not been included in the conditions of the Exemption Order, recognising that JTSI and DWER had formal instructions to have no impact on social or economic factors,” the Water Corp response said.

A Cook government spokesman backed Alcoa and the current state of its regulatory approval.

“The conditions of the exemption order itself limit the physical areas in which Alcoa can explore, clear and mine, and require regular compliance reporting to the state government,” he said.

“Any breach of conditions would see the exemption order immediately cancelled, and the state government retains the right to withdraw or amend the exemption at any point.”

The spokesman said monitoring of water quality was ongoing, and Water Corporation was a part of that process.

“Proposed mining activities in drinking water catchment areas have a comprehensive risk management framework in place with the primary goal being the protection of public health,” he said.

Water Corporation handballed questions to Water Minister Simone McGurk.

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