Summer Jones, Senior Environmental Scientist at Tetra Tech Coffey, presented at the 2025 ALGA Conference on one of the most intriguing projects of her career—remediating a “mystery oil pit” at a remote, legacy mine site in Western Australia. With a background in contaminated land and environmental remediation across Australia and Canada, Summer brings a global perspective and sharp technical insight to some of the industry’s most complex challenges.
Here Summer shares insights to delve deeper into her work and uncover the unique story behind this legacy mine rehabilitation project.
Can you describe the specific conditions or history of the site featured in your presentation?
The site is incredibly remote—about three hours from Port Hedland via dirt road—and currently in care and maintenance. No one on site initially claimed responsibility for the oil pit’s origin, and there was no formal documentation or historical reporting. Locally, it had a nickname we couldn’t use officially, but everyone knew about it. The pit was small but notorious for its odour and unknown content. Anecdotal evidence suggested it had received a mix of waste materials over the years, from workshop fluids to potentially other chemical disposals.
What makes remediation of oil pits in remote locations particularly challenging from both a logistical and environmental perspective?
Accessibility is the biggest hurdle. The area experiences cyclones, and during our time there, multiple weather events delayed works. The original access road had to be abandoned due to damage, requiring a new route. Transporting material for off-site disposal meant navigating challenging terrain with semi-trailers—not easy. On the environmental side, you’re working with unknowns in an ecologically sensitive area, so the margin for error is slim.
What were the key unknowns or risks at the outset of the project, and how did your team approach them?
We had no idea what was in the pit. There were no previous reports, just stories. We approached it with extensive testing and stakeholder engagement. The client came on-site with us—everyone was curious. We excavated test pits and sampled down to three metres, analysing for a broad suite of contaminants to fully characterise the material. The top layer—what we call “the goo”—was particularly impacted, but material below that was far less contaminated.
What assessment or investigative techniques did you use to characterise the nature and extent of contamination?
We coordinated closely with the local landfill operator in Onslow to ensure our sampling matched their acceptance criteria. That included leachate testing with both deionised water and acetic acid, PFAS analysis, and detailed hydrocarbon profiling (aliphatic and aromatic splits). By tailoring our testing program to landfill requirements, we were able to classify most of the material as Class 3 rather than Class 4 or 5, which made a huge difference in cost and disposal logistics.
Can you walk us through the remediation strategy and how it was selected over other potential approaches?
The strategy focused on ‘selective excavation and segregation’. The highly contaminated top layer will be sent to a more secure cell, while the cleaner underlying soils will go to a general waste cell. We had considered blending all the material to reduce contaminant concentrations, but that would have resulted in a higher classification and more expensive disposal. Our data-driven approach allowed us to isolate the problem material and significantly reduce costs.
Mining companies are increasingly building closure into their planning from day one, and environmental budgets are finally reflecting the true cost of doing things properly. There’s still a way to go, but this project shows that even unexpected legacy issues can be resolved with the right planning, expertise, and intent.
Were there any innovations or adaptive solutions that had to be implemented due to the site’s remoteness or the nature of the waste?
Absolutely. The biggest innovation was around ‘material classification and logistics planning’. Our testing strategy enabled precise classification, which reduced waste volume and transport complexity. We also had to be flexible around scheduling—cyclones shut us down more than once, so having contingency plans for mobilisation and subcontractors was essential.
How did you ensure compliance with environmental regulations and stakeholder expectations, especially in an area with limited access or data?
We engaged early and often with stakeholders—including landfill operators, subcontractors, and the client’s environmental leads. We also developed a ‘conceptual site model’ that included all potential environmental receptors, including nearby gorges, waterways, and sacred Indigenous sites. This transparency helped ensure our approach met environmental and cultural expectations.
What environmental or ecological sensitivities existed at the site, and how were these factored into your remediation plan?
Our approach was conservative and considered considering impacts to groundwater and surface water, even if they seemed remote.
The site is located in a*breathtaking part of the Pilbara, West Australia, surrounded by gorges, native vegetation, and cultural heritage sites. This land will eventually be handed back to Traditional Owners, so we have a responsibility to restore it to a safe, culturally respectful standard. We kept this in mind throughout, especially knowing how significant the surrounding landscape is to the local community.
What were the outcomes or indicators of success for the project—and have you been able to quantify long-term benefits post-remediation?
While we’re still in the final stages of executing the strategy, one of the key indicators of success has already been achieved: we proved the contamination was largely confined to the surface layer. That allowed us to reduce both waste volume and disposal cost. The site will also be formally monitored post-remediation to confirm natural recovery over time.
How does this project contribute to the broader conversation around legacy mine site management in Australia?
It’s a clear reminder that legacy issues don’t just go away, and that proper documentation and planning are crucial. The client is taking a proactive stance in resolving these historical impacts, which is a big positive. It also highlights the need for mine closure planning to incorporate remediation contingencies—even for unknowns like this.
The lessons I will take from this project are two main ones. Firstly, to always be flexible, and secondly to never underestimate logistics. Cyclones, limited access, lack of historical data—these are realities on remote projects.
Are there opportunities to apply the remediation approach used here to other sites with similar legacy contamination issues?
Absolutely. The key is to understand the contaminant profile early and match it to disposal pathways. Our selective removal strategy could be replicated elsewhere—especially at remote or legacy sites where full-scale remediation isn’t practical.
How do you see the industry evolving when it comes to legacy waste management at mine sites—are we making enough progress?
I think we’re moving in the right direction. Mining companies are increasingly building closure into their planning from day one, and environmental budgets are finally reflecting the true cost of doing things properly. There’s still a way to go, but this project shows that even unexpected legacy issues can be resolved with the right planning, expertise, and intent.
Connect with Summer Jones at [email protected]