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Western Australia’s water utility was shut out of Alcoa’s mining sites in state forest, newly released documents reveal, raising concerns the lack of oversight could be detrimental to Perth’s drinking water supply.
The documents show Water Corporation had also expressed concerns that several state government departments had stopped providing them with information relevant to Alcoa’s mining plans that could have assisted them in mitigating risk.
The concerns were revealed after a freedom of information request was submitted to Water Corporation by the WA Forest Alliance.
“Alcoa have initiated fencing of their minesites within the state forest and have imposed controls of access for Water Corporation rangers, including needing to be escorted into the areas to access our assets and not allowing drone use near their mining activities,” one document from May 2025 revealed.
“Water Corporation is working through these constraints, seeking solutions with Alcoa to allow us to undertake our critical operations.
“However, until these constraints are resolved, Water Corporation’s ability to monitor water quality within the mining areas is significantly diminished.
“Water Corporation also continue to request relevant data and information from Alcoa in a timely way, including performance reports which indicate a significant number of chemical spills, drainage failures and other events, which are pertinent to how we operate our dams and the (integrated water supply scheme).”
That scheme delivered 337 billion litres of drinking water in 2024-25 to over 2 million people in WA.
Water Corporation said that not holding a seat on the state government-formed Bauxite Strategic Executive Committee had also limited visibility and access to key planning documents, “constraining our visibility of Alcoa’s mining plans, and in turn constrained our ability to plan risk mitigation activities into our operations around those mining activities.”
One such document was the 2025-2029 Mining and Management Plan, which outlined Alcoa’s future mining intentions and the potential risks to Water Corporation operations and assets.
That document was held by the Department of Jobs, Tourism, Science and Innovation (now the Department of Energy and Economic Diversification) “for some months”.
The plan was eventually given to Water Corporation by the Department of Health in May 2025 but was “not considered sufficient to reasonably assess the potential impacts of future operations on the integrated water supply scheme”.
Water Corporation recommended that a whole-of-government risk management plan be developed.
Both Water Corporation and Alcoa did not answer questions on whether that plan had ever come to fruition, instead pointing to efforts made in the government’s independent technical advisory group.
The DEED, which chairs the Bauxite Strategic Executive Committee, said the department worked closely with other agencies to monitor Alcoa’s operations and potential risks to the surrounding environment and water resources.
A spokesperson said Alcoa’s mining and management program conditions assisted the company in “transitioning contemporary environmental frameworks”.
The documents also showed that the Department of Water and Environmental Regulation are “also now declining offers for technical advice from Water Corporation into their assessments”.
“We also continue to request information from DWER’s environmental assurance team and seek to build a relationship where they will share information with the Water Corporation,” it was stated.
“To date this exchange of information has been limited.”
In response, a DWER spokesperson said Water Corporation worked with their compliance teams, with both jointly attending Alcoa’s mine sites for a routine site inspection as recently as December 2025.
Lack of oversight labelled as ‘alarming’
Conservation Council of WA executive director Matt Roberts described the lack of oversight Water Corporation raised as “alarming”.
“At a time when we see increasing questions around Alcoa’s practices in our northern jarrah forest, we are seeing mining exemptions handed to them from the state and federal governments,” he said.
“The loss of our forests is bad enough, but we also have our drinking water being put at risk, with limited oversight and little to no accountability.
“When is enough, enough?”
WA Forest Alliance senior campaigner Jason Fowler said the risk Alcoa’s forest mining posed to Perth’s drinking water was unacceptable.
“And Alcoa knows it,” he said.
“Alcoa and the Cook government must urgently heed the utility’s advice on managing the threat to drinking water, and ensure full access to monitor Alcoa’s activities.”
A Water Corporation spokesperson said it provided advice on Alcoa to government through the independent technical advisory group.
“This enables us to provide independent, evidence-based advice to inform government decision-making on risks to drinking water catchments and is the established mechanism through which agencies share information and consider risks,” they said.
“We have been forthright in engaging with Alcoa to remedy previous concerns over site access and to ensure data is shared in a timely and comprehensive way.
“We continue to thoroughly monitor all mining activity in proximity to public drinking water catchments.
“Water Corporation’s position remains that protecting drinking water at its source provides the strongest protection for public water supplies.”
An Alcoa spokesperson said “in more than 60 years of operation we’ve never negatively impacted Perth’s drinking water supply and are focused on maintaining that record”.
“We continue to strengthen our relationship with Water Corporation and established processes are in place to enable visibility of our current and planned mining activities and Water Corporation’s ability to monitor water quality,” they said.
Alcoa has promised $100 million towards any cleanup efforts
A Deed Poll was negotiated between the State of Western Australia and Alcoa – signed at the beginning of 2025 – and comprises a $100 million financial guarantee from Alcoa.
Water Corporation can draw upon that guarantee to fund contingency and remediation actions “in the event that a dam cannot be used due to impacts from Alcoa’s mining operations”.
The documents show Water Corporation believes that while the financial guarantee “will not be sufficient to remediate for a major pollution incident” it will serve as a “reasonable disincentive for Alcoa to negatively impacting the Corporation’s dams.”
Previous Water Corporation reports suggest there are significant risks associated with Alcoa’s current operations, noting that the “probability of contamination of reservoirs is considered certain”.
In 2023, the government was told by Water Corporation that contamination could necessitate a $2.6 billion spend to clean up the water and force a shutdown of the 78-billion litre Serpentine dam.
The estimated cost of treatment of all dams where mining or exploration is intended is in the order of $3.25 billion.
Alcoa did not answer questions on whether they believed the $100 million Deed Poll to be sufficient, based on those figures.
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