The Western Australian Environmental Protection Authority says it will "comprehensively scrutinise" parts of the US-listed company's five-year bauxite mining program for its Huntly and Willowdale sites on the Darling Range, south of Perth.
"These proposals involve the clearing of large areas of native vegetation so there will be impacts to a range of environmental values including biodiversity and water resources," chair Matthew Tonts said on Monday.
"There is also the potential for significant cumulative impacts to the Northern Jarrah Forest."
The WA Forest Alliance referred two of Alcoa's mining and management programs for 2022 to 2027 to the independent authority earlier in the year.
The EPA considered more than 2500 public submissions following a seven-day comment period and other advice and determined a public environmental review was necessary.
Professor Tonts said the regulator would consider potential impacts of land clearing on flora, fauna and water catchments.
It will look at the impact of noise, dust and visual impacts on the community and climate change as a result of the mines' greenhouse gas emissions.
The assessment will include a longer-than-usual 10-week public consultation period for Alcoa's environmental review document because of the potential impact on the Northern Jarrah Forest and the high level of community interest.
"The EPA has also decided to conduct in-person briefings with community groups to ensure all information and concerns are captured in the assessment," Prof Tonts said.
The Cook government last week gave Alcoa an exemption to continue its mining operations with strict controls during the review, saying it would protect jobs.
The EPA is also considering a proposal by Alcoa to increase production at its Pinjarra refinery and transition mining at the existing Huntly Mine to the Myara North and Holyoake regions.Â
Alcoa has mined bauxite in WA's southwest for 60 years and operates two bauxite mines and three alumina refineries.
The company said it would cooperate with the EPA assessment and would work to improve its operations to meet the exemption conditions and community expectations.
Authorities earlier this year found a pipeline built by Alcoa without approval was at risk of leaking toxic chemicals into a dam that supplies drinking water in the state's southwest.
It said the pipeline was likely to contain wastewater contaminated with PFAS, which is associated with a range of serious health issues.
Alcoa was ordered to urgently flush out the pipeline which crosses the Samson Dam, about 100km south of Perth.
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