Families have set up makeshift houses in the gaping pit, and men, women and children pass their days digging for whatever gold and copper they can reach.
It's risky and dangerous work, but many feel they have no other option.
They live among decaying infrastructure and the skeleton of the mine's concentrator, left over from the massive operation run by Bougainville Copper Limited (BCL) between 1972 and 1989.
BCL was majority owned by global mining group Rio Tinto, but operations ceased on the mine in 1989 after an armed insurgency known as the "Bougainville crisis".
Growing anger over the mine's environmental impact and the limited financial compensation paid to landowners spilled over into a civil war that lasted a decade and claimed up to 15,000 lives.
BCL has previously described the situation as one in which it had to leave "in a hurry", and the mine was not wound up as it should have been.
The damage from Panguna, and the emotional and physical pain that comes with it, is still unfolding.
Water tinged blue from copper contamination flows from the mine site into rivers and creeks, polluting drinking water.
Millions of tonnes of mine tailings, a liquid slurry of fine mineral particles left over after the extraction of ore, have also diverted floodwaters into villages and hamlets.
In 2020, the Human Rights Law Centre, acting on behalf of 156 Bougainville community residents, lodged a complaint with the Australian government, alleging serious adverse environmental and human rights impacts linked to the ongoing pollution from the mine.
Although the human rights complaint revolves around the environmental and social damage done in Bougainville, the complaint has been filed with the Australian National Contact Point for Responsible Business Conduct (AusNCP) because Rio Tinto is a multinational company registered in Australia.
Now, the full scale of the damage is expected to be laid bare in an independent assessment, which was mostly funded by Rio Tinto in response to the complaint.
For those on the ground, the process is seen as a vital way to find a set of solutions, to help remediate the disaster.
But many also want the mine to reopen, believing a resources company would come in and be required to clean up the mess.
There may also be a financial incentive, with the autonomous Bougainville government (ABG) estimating there is almost $90 billion of return still in the pit.
The desperate search for clean water
An independent group, the Panguna Mine Legacy Impact Assessment (PMLIA) Oversight Committee, was formed to oversee the assessment of the mine.
This year, a team of scientists began work on a major field study, carrying out environmental, social and human rights investigations in order to identify Panguna's impact.
The committee consists of landowners, clan and community leaders, members from the ABG, Rio Tinto, BCL and the Human Rights Law Centre.
One of the key areas that will be examined is the "lower tailings", downstream in the Jaba/Kawerong River valley, which is where mine waste was dumped.
Travelling from the mine to these communities takes hours, through a series of dirt roads through the forest and several river crossings.
At Kuneka, few homes are accessible by car because of floodwaters that have been diverted into the village.
Villagers say tailings waste builds up in the river and causes the flooding, which contaminates their drinking water.
Many families have relocated closer towards the mountains in search of higher ground and clean water.
Local man Vennie Neo said he had access to some groundwater, but often relied on collecting rainwater without a tank.
"When the mine was operating, the Jaba River was destroyed, including all the smaller streams," he said.
"When we see that it is about to rain, we put out things to collect rainwater, but if we are late there will be no water.
"We just have to cook on the fire and eat … we are the unfortunate ones."
Bernardine Kirra, who represents the communities of the lower tailings on the oversight committee, estimates 90 per cent of those people do not have access to safe, clean drinking water.
"All our sources where we used to get clean drinking water, it's been polluted by the mine, by the tailings," she said.
Mud and tailings replace wetlands and forests
In the Jaba/Kawerong River valley, communities say wetlands and forests have been destroyed and replaced with large swathes of mud and tailings sludge.
"We feel that the damage will never be fixed again," Ms Kirra said.
"The landscape has changed a lot, and our new generation, they don't know [what] the forest or the land was like in the past before the mining came."
She said rivers here had few fish, and washing and swimming in them caused a burning, itchy sensation.
"Most of our land has been destroyed [where] we could plant cocoa to get an income," Ms Kirra said.
"That's why we have some of our people panning for gold — because most of the land is underwater or it's swampy so we cannot grow any cash crop."
"Life has changed a lot and people are really struggling now to find money."
Leonard Paki has come down to the Jaba River with his family to pan for gold.
"It is to support us to buy food and school fees … we come and pan for gold here to get a little money to sustain us," he said.
"When we come, we bring water in containers and drink from them."
"Here you cannot wash or drink from the river … the entire forest is already damaged by the mine waste."
Human rights group says Panguna an 'urgent situation'
It is expected the assessment will have early findings for release in mid-next year.
But The Human Rights Law Centre's Keren Adams said, on the ground, there was a "sense of frustration that things aren't moving towards actual solutions".
"It's an urgent situation that they feel needs to be addressed as soon as possible," she said.
"We'd really like to see the company (Rio Tinto) moving swiftly to discussing what can be done to address these huge problems that people are living with."
Complainant, landowner and local MP Theonila Matbob said while Rio Tinto's funding for the assessment was a start, she wanted a commitment from the company to fund the clean-up and remediation.
"We should be talking about, or committing to, the second step or the solution, or what happens after the assessment," she said.
"Every single day is a challenge … mentally the future is always unsure, it's always bleak."
"We're trying to say, maybe let's adapt and be resilient here, but the reality is not on our side."
In a statement, a spokesperson for Rio Tinto said the independent legacy impact assessment (LIA) was "an important milestone in understanding the potential impacts of the Panguna mine".
"Our people were recently able to visit Buka for the first time in more than 30 years as part of the LIA process, which is helping us to better understand the situation," they said.
"This included meeting with government representatives, landowners and clan and community leaders, who are fellow members of the Legacy Impact Assessment oversight committee."
When asked if the company would contribute to a remediation fund, the spokesperson said the assessment was a "key first step to identifying impacts and discussing next steps with all parties".
"The understandings from it will help us meet our commitment to act in line with our external environmental and human rights commitments and internal policies and standards," they said.
In 2016, Rio Tinto divested from the mine. Its shares are being transferred to the ABG.
Could the mine reopen?
The ABG has signed a resolution with Central Bougainville landowners for the Panguna mine to reopen and be operated by a government-owned entity.
But the ABG's new mining minister, Robin Wilson, said after that, "nothing happened".
He said he was keen to re-activate the process and the decision was still in the landowners' hands.
"According to our law, they own the minerals," Mr Wilson said.
"Whilst the government has the overall agenda of economic activities to generate internal revenue, we are mindful that the process involves the consent of the landowners."
The cost of reopening the mine is estimated to be about $US6 billion ($9 billion).
But there's a massive economic incentive for the ABG to have the mine reopened.
"If the mine opens, the mine is expected to operate for 28 years and it's expected to make returns in excess of $US58 billion … so that's a lot of money there," Mr Wilson said.
He's hoping a reopened mine would stimulate the surrounding economy, generating increased tax revenues.
Bougainville is currently seeking its independence by 2027, but it's still mostly reliant on grants provided by the PNG government.
Yet downstream in the communities living with the tailings waste, some have voiced opposition to the mine's reopening.
Ms Matbob is calling on everyone to work together to create solutions.
"It takes all of us to work together in solving the problem that was instituted and imposed upon us," she said.
"[If] we make politics … we are only going to bring into the picture bitter generations to come because they'll say, 'What have you done about this?'"
Story first published on ABC News