Wake up Joondalup

The curious amongst you may wonder what happens when you don’t extract the leachate from a tip.

By October 2024, it was estimated that more than 167 Olympic-sized swimming pools worth of bin juice had accumulated in the lined tip at Tamala Park, known as Stage 2.

That was nearly two years ago. Just before the first Environmental Protection Notice (EPN) was issued.

We know this from the publicly available Mandatory Auditor’s Report (MAR), published in April 2025. According to the MAR, Talis estimated the volume of leachate within Stage 2 at over 417 million litres.

And the report describes that as a conservative estimate.

MRC surely must have known there was a serious leachate problem. By November 2024, DWER had issued its first EPN. Talis Leachate Management Plan landed in February 2025, and the MAR followed in the April.

So what happens when you have that much leachate accumulating?

It escapes into the groundwater.

I read the MAR so you don’t have to. But if you’re a member of the MRC, you probably should.

Here are the Cliff Notes.

According to the report, groundwater quality has been shown to be impacted by leachate seeping through the landfill liner. The leachate acts as a constant source of contamination and, to put it simply, the more bin juice sitting above the liner, the more pressure there is pushing it through and into the groundwater.

So what is the contamination?

There is now a plume, which is great if you’re a peacock, not so much if you’re leachate in the groundwater beneath a landfill.

To be clear, this does NOT mean residents are drinking contaminated groundwater or that every contaminant presents an immediate health threat.

And rather than paraphrase the risk, I’ll quote directly from the report:

“Assessment indicates that groundwater beneath the site is impacted by a leachate plume containing elevated levels of chloride, ammonia, arsenic, iron, and PFAS compounds, with contamination primarily originating from the active western portion of the landfill. Heavy metals are present in wells along the landfill’s western, northern, and southern edges, though their spread appears contained within the site boundary. While the plume is expanding westward and downward in the water column, it is retracting in the northern buffer zone. Groundwater onsite is unsuitable for drinking or non-potable use, with moderate risks from ammonia, arsenic, E. coli, and PFAS, though occupational health risks remain low.”

The report continues:
“The PFOS levels in the leachate plume exceed ecological guidelines and remain undefined to the west of the site, extending toward the Indian Ocean (1.8 km). This is assumed to present a moderate risk to offsite marine and terrestrial ecology. “

Data gaps in the Groundwater Risk Assessment (GRA) involve the spatial extent and stability of the leachate plume, as well as its associated risks to offsite human health and marine ecology.”

Data gaps? Undefined?

In this case, that’s Auditor report-speak for: we don’t know because there weren’t monitoring wells there to test it.

At the time of the report there were no offsite groundwater monitoring wells to the west capable of telling them where the plume ended.

What we do know is that, in the Auditor’s opinion, the aquifer has been impacted by the leachate. The leachate will never be removed and now the best that can be achieved is mitigation measures.

Get the leachate down. Reduce how much more gets through. Manage and monitor what is already there.

And even then, the report warns that improvements to groundwater quality will be slow and that the plume may continue to expand because of the mass of contamination already in the aquifer.

Which leads me to my next big question since the one about why they stopped the evaporation ponds:

What on earth has MRC been doing about this leachate issue since the evaporation ponds were stopped? Since the first EPN? Since the February 2025 Talis report? Since the April 2025 MAR?

Because the Auditor wasn’t coy about what needed to happen: reducing the amount of leachate sitting above the liner was the only meaningful control left.

Sitting fees are not paid to sit on reports.

They are paid for councillors to read them, understand them, ask questions and act on what they say. They are paid to offer oversight.

But in this case, whatever has been done about the leachate, if anything, is clearly not enough.

Because on 3 August 2026, DWER issued another Environmental Protection Notice.

And for me, this isn’t simply a story about contaminated groundwater.

It is a story about what happens when a serious, long-term environmental liability is governed by a structure that seems much better at asking for and receiving reports about risk than responding to them.

Which brings me to Lesson 4 of this series:
Regional Councils and the laws of perverse incentives and unintended consequences.

Link to the full Mandatory Auditor’s Report in the comments.

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