Minimising risks on contaminated sites

There are more regulations now, and more awareness around management of construction and development sites. Whereas in the past a builder might have pushed ahead to get the job completed, everything now needs to be managed with more care. We’re testing for a larger array of contaminants, making assessments, and developing management strategies, which ultimately means sites are safer. 

It depends on the project. Sometimes we will be engaged upfront and complete a due diligence assessment to determine potential development costs from a contamination perspective prior to the purchase of a site.  

We might be brought in mid-way through a project when unexpected items are encountered, and then need to keep returning as structures are being demolished and removed. It’s hard to test soil for contamination if an old structure is sitting on the top. 

We’ve worked on the Subiaco Oval redevelopment and in that case, we completed initial testing with a drill rig while the structure was still erect. We drilled through the concrete slab of the actual stadium itself and tested for contamination to get a feel for what may lie beneath.  

That could only give us a broad understanding of the soil condition – we couldn’t assess for contaminants such as asbestos. It wasn't until they started pulling things down that we could have a better feel for any areas that needed further attention. 

For the stadium redevelopment, the identification of asbestos fragments in soils beneath the structure presented a significant risk to the project with the potential to push out project schedule and costs if not managed carefully. It’s quite common to find asbestos on sites - back in the day, when they demolished structures containing asbestos, they tended to leave the asbestos buried on site and just build over the top.  

We also look for pesticides and heavy metals. These come from things like old termite treatments and can present a risk to health when a site is redeveloped, particularly if being repurposed for a more sensitive land use.  

The first stage of our investigation typically involves a desktop assessment to gather information relating to the site’s history. We'll look at historic documents and aerial photography to get an idea of how things have progressed at that site – what’s been there, has it changed, etc.

By dating a building or structure it can give an indication as to what potential contaminants may lie beneath and within site structures. Then we’ll go on site to take samples and confirm what needs to be done to manage and prepare the site for redevelopment, and this might happen at multiple stages of a development.

A lot of land and residential developments that involve what we call acid sulfate soils. These are typically waterlogged soils, largely oxygen free with tiny crystals of iron sulfide minerals. If not managed correctly, when disturbed and exposed to oxygen the soils can oxidise and release acid, which in turn mobilises heavy metals in the groundwater and cause contamination. This can damage the environment as well as buildings, roads and other structures.  

We do a lot of acid sulfate soil work and groundwater management in Perth because it’s shallow, with a shallow water table and many developments happening on low-lying land. 

We also do a lot of assessments of per- and poly-fluoroalkyl substances (PFAS). It is a contaminant that has recently been linked to potential health and environmental issues. The projects stem from historic land use where PFAS-containing Aqueous Film-Forming Foam (AFFF) was used at Defence sites, waste treatment facilities and fire stations. 

Our project work is about minimising risk. PFAS, like asbestos and other products, had a beneficial use then negative aspects were realised, sometimes, decades later. So, we now manage those risks and minimise their impact on human health and the environment. 

I have a background in chemistry and forensic science, so I've always had an inquisitive nature and analytical way of thinking. For work involving contaminated land, it's helpful to have a chemistry background knowing about the fate and transport of contaminants through soil and groundwater, and seeing how they interact. And then, applying a forensic lens to try to work out the next steps and determine health and ecological risks.  

Basically, we need to figure out what issues are present that may hinder development, how they got there, how to manage them to resolve any issues for the clients and avoid delays in a cost-effective and environmentally friendly manner. 

Working among a herd of cattle, with a couple of angry bulls and only a small excavator and field vehicles as protection. That added a bit of excitement to the day! Many undeveloped sites are home to snakes, ticks, spiders and rats, which always keep field staff on their toes. 

Digging in semi-rural areas often leads to some interesting discoveries such as buried car bodies, entire structures and on occasion old glass bottles, some dating back to the early 1900s.