Case Study: Managing UPSS Contamination Risk During Redevelopment
Introduction
We regularly deal with sites that have legacy underground petroleum storage systems (UPSS). They’re one of the most common contamination risks we see, and one of the easiest to underestimate.
On a recent redevelopment project in Western Sydney, we worked through a fairly typical UPSS scenario that highlights how these risks actually play out on site.
The Scenario
The site was a former commercial facility being redeveloped into a data centre.
There were multiple UPSS across the site, including a refuelling area and tanks associated with generator infrastructure. As part of the works, these systems needed to be removed and the surrounding soils validated.
What We Expected
At the outset, the key risk was straightforward:
petroleum hydrocarbon contamination in soil and potentially groundwater.
That’s standard for UPSS works, and the investigation and validation approach was designed around that.
What Actually Happened
During excavation and stockpiling of soils from one of the UPSS areas, things didn’t play out exactly as expected.
Some areas appeared clean based on visual and olfactory inspection
Material was initially managed as general solid waste
During offsite disposal, unexpected contamination was identified within the stockpile
This required us to stop, reassess and reclassify portions of the material.
How We Managed It
Segregation Over Assumptions
Rather than treating the excavation as a single unit, we broke it down into smaller zones and stockpiles.
That allowed us to separate clean from impacted material and avoid over-classifying everything.
Treating Classification as Iterative
Waste classification wasn’t a one-off exercise. As new information came in, we updated our approach.
That meant:
additional targeted sampling
rapid lab turnaround where needed
revising classifications based on actual data
Staying Aligned with the Contractor
This is where these jobs are won or lost.
We worked closely with the civil contractor to adjust excavation sequencing, manage stockpiles and respond quickly when issues came up. That kept the job moving.
Having a UFP in Place
The Unexpected Finds Protocol did exactly what it’s supposed to do, it gave the team a clear process to follow when something didn’t look right.
No confusion or delays while people worked out what to do.
Key Takeaways
UPSS impacts are rarely uniform – you can have clean and impacted soils within the same excavation
Hydrocarbons aren’t always the only issue – other contaminants can show up unexpectedly
Waste classification drives cost – getting this wrong has real commercial impact
Flexibility is critical – you need to adapt as the site conditions become clearer
Closing Thought
Most UPSS projects don’t fail because contamination exists, they run into trouble when the approach doesn’t allow for uncertainty. If you plan for variability, stay flexible and integrate environmental management into the construction process, these risks are very manageable.
If you’re dealing with a site that has existing or former UPSS, it’s worth getting clear on the risks early. Reach out to Marty or myself, we’d be happy to talk through your project.
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