Alarming mining practices by Alcoa near Perth’s biggest dam could render the water undrinkable, causing water restrictions and potentially costing the state up to $2.6 billion to fix.

The US mining giant changed its bauxite mining methods around five years ago, increasing the risk of sediment flowing into the nearby dam.

WA Today reporter Peter Milne told 6PR Mornings one big rain event in the area could cause major issues.

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Shire of Serpentine-Jarrahdale President Michelle Rich says the different rules for members of the community and the miners are mind-boggling.

“Our communities are not allowed to walk, hike, horse ride, mountain bike – they can’t do any of these recreational activities but the area is allowed to be strip-mined,” Ms Rich told Gary Adshead.

Press PLAY to hear more on-ground details of the Alcoa mining threat