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The City of Perth will seek assistance from the state government for a “practical closure pathway” for Tamala Park Waste Facility after excess leachate in the landfill grew to almost 40 Optus Stadiums.
The City is one of seven member councils that takes its residential waste to the facility which accepts up to a third of Perth’s household waste.
At its meeting on Tuesday night, the council voted to request Lord Mayor Bruce Reynolds to advocate to the state government for a “balanced regulatory response” that enables a practical closure pathway for Tamala Park.
Councillors also unanimously supported their acting chief executive to monitor the Tamala Park landfill closure, leachate management, community amenity and financial implications and provide them with reports on the status.
As of October 2024, data shows there were 167 Olympic-sized swimming pools worth of leachate accumulated at the bottom of the landfill.
Without any removal methods in place, that number will rise.
Data in the City’s agenda report reveals that the Mindarie Regional Council – who runs the landfill – “revised its estimate of leachate stored within Stage 2 from approximately 417,000 m³ to approximately 2.07 million m³, or about 2.07 billion litres, after incorporating measurements from internal landfill-gas wells.”
That equates to 828 Olympic swimming pools’ worth of leachate or 39.4 Optus Stadiums.
“DWER reports potential leachate heads of approximately 30 to 40 metres above the liner at some locations, while acknowledging uncertainty as to the distribution and hydraulic connectivity of the leachate within the waste mass,” the report said.
As a result, the Department of Water and Environment Regulation issued an Environmental Protection Notice on August 3 to the Mindarie Regional Council.
The notice requires the MRC to provide a detailed and accurate determination of the leachate levels as well as a leachate removal plan, with 30 days to do it.
The EPN also requires the council to improve its landfill gas management, provide updated landfill closure planning, and undertake additional technical investigations.
The agenda report says a 2025 assessment by the MRC identified off-site leachate treatment scenarios could cost between “tens of millions of dollars to more than $1 billion” for the amount of leachate that was in the landfill in 2024.
“Given the current leachate estimate is materially higher, those historical estimates should not be directly extrapolated. It is nevertheless reasonable to conclude that a large-scale off-site program could expose MRC and its member councils to costs in the hundreds of millions of dollars,” the report said.
“The ultimate allocation of those costs between member councils is currently unknown but is likely to be based on the current ownership structure, of which the City is a 1/12 owner.”
The landfill was due to reach the end of its operational life around 2028, but an excessive buildup of liquid waste is now threatening to derail the closure plans.
Tamala Park is only partially lined and the MRC’s recent request to install a piggyback liner and create a leachate management area in the northern portion of the tip – closest to the nearby residential homes – was rejected by DWER at the beginning of August.
A DWER spokesperson said the high leachate levels was one of the reasons behind the decision.
Five of the seven councils have received exemptions to take their waste to other facilities before Tamala Park’s expected closure date, but none have anything locked in yet, leaving the site in limbo if it will ever reach its final profile height to be able to close.
The MRC is considering a Waste-to-Energy agreement at a behind-closed-doors meeting on August 27.
A further report to the City of Perth council regarding the Waste-to-Energy agreements will be presented at the September ordinary council meeting.
DWER was approached for comment regarding the leachate levels in the landfill.
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