by Daniel Green
No matter where you dig in the developed areas of this great nation you will invariably find hazardous contraband of some kind. Asbestos, lead pipe, remnants of petroleum services, pesticides, naturally occurring chemicals and much more. No more can we just bury the sins of the past. Our children’s future depends on it and besides – buried secrets always find their way back to the surface.
Take Erskineville’s Sugarcube and Honeycomb terraces. One hundred and twenty-seven stunning apartments and townhouses built on the contaminated remains of the old Ashmore Industrial Estate, their owners paying upwards of a cool million for the chance. Soon after handover in 2018, Ashmore relinquished her secrets in the form of asbestos, hydrocarbons and contaminated groundwater. For one reason or another, the soil that the entire 11 000 square metre construction lies on, was not remediated. Post construction testing has proved the area uninhabitable. Now those 127 apartments lay abandoned like some inner west Chernobyl.
Don’t despair, not all soil is contaminated due to human activity. Mother Nature has her part to play as well. Soil that is high in naturally occurring chemicals like acid sulphate and arsenic can have the same damaging health impacts as manmade materials. Heavy metals such as mercury and nickel have long been known to have harmful effects on our wellbeing. One extreme example is the hydrogen sulphide emitted by venting volcanoes. It’s completely and utterly toxic yet completely and utterly natural.
What is Soil Remediation?
Remedial works correct harmful impurities in soil. Known as spoil in the old speak, GSW [General Solid Waste] or VENM [Virgin Excavated Natural Material] are two types of material that will likely form the earthen foundations on which we build. Thousands of years of human interaction and millions of years of natural activity have produced soils that are unfit for foundations, both from an engineering standpoint and a health one. Soil remediation is corrective action towards having healthy, stable ground to construct residential, commercial and industrial structures – so that they remain vertical and harm free for their typical lifespan of 60+ years.
So Why Remediate?
There’s many reasons from fiscal motivation through to benevolence. Yes, it’s good for the environment, for our children’s future, for our communities. What it also does is open up more development options. Say you’re begun groundworks on 111 apartments in Neutral Bay that you can collectively sell for $180m. Post-demo soil testing shows signs of arsenic and remnants of an old service station. If you simply cap it you’re still at 111 units and $180m. But if you excavate and remediate, now you can add a sub-level carpark, sixteen retail stores & a daycare centre. That $180m is easily in excess of $200m.
How To Remediate?
The short answer is a] an inspection to gauge the type of contaminants and to quantify the damage, then b] removal in whichever process is best/cost effective, c] disposal and finally, d] the final inspection to determine the land has been reclaimed. The differing methods are where its gets technical:
- Thermal desorption. This is where the soil is heated, directly or indirectly, to a significant enough temperature to that the contaminants seperate themselves from the solid medium. The contaminants can then be collected and disposed of while the clean soil can be reused.
- Direct Thermal Destruction. This process uses heat to annihilate any impurities in the soil. Due to the nature of this method it can’t be used for all contaminants. Also called incineration.
- Pyrolysis is thermal decomposition at elevated temperatures in an inert atmosphere. It’s different to Direct Thermal Destruction in that it uses no oxygen.
- The Chemical Stabilisation process involves adding emulsifiers, repellants and binders to modify the behaviour of the soil. This renders the impurities obsolete as well as trapping them in situ.
- Chemical Oxidisation refers to a process whereby oxidants are utilised to help change harmful contaminants into less toxic ones. Like pumping hydrogen peroxide into ground wells.
- Bioremediation. This is where living organisms, such as microbes and bacteria, remove contaminants from the soil. One good example is the use of worms as they excrete clean soil as waste.
- Transportation and disposal. The contaminated material is excavated, trucked away and disposed of in line with government regulations. Bingo’s Eastern Creek facility is one of Sydney’s primary locations for contaminated waste disposal.
- Chemical fixation. This adds reagents or materials into the contaminated soil to form insoluble or hardly movable, low toxic matters so they can’t migrate to water or other organic material.
As soon as the conditions allow. The type of remediation most suitable will dictate how long it will take to regain stasis. Excavation by machine can, with a 20t excavator, a skilled operator and truck good access, move 1000t in an eight hour work day. Bioremediation can take years. Some of these approaches may need multiple attempts, so sooner rather than later is probably your best bet.
Perfect Contracting and Perfect Remedial are great choices. With the joint capabilities of decades of tier one construction, civil & demolition works, Perfect has the know-how, the systems, the leadership and the machinery to tackle any soil remediation project sent our way. We’ve worked with multiple construction, government and industrial clients across an array of sectors in this exact space. For example:
- Musswellbrook Regional Council – Asbestos Soil Remediation
- Method – Transportation and disposal
- FDC Construction – Asbestos Soil Remediation
- Method – Transportation and disposal
Regardless if the contaminants are manmade or natural, either way you slice it its a legacy issue, that unfortunately – like inheriting that dilapidated Rose Bay mansion from your recently deceased long-lost great aunt – is our responsibility to amend. Especially considering there’s more than 160 000 known contaminated sites across Australia polluted with as many as 75 000 different contaminants.
Perfect Contracting and Perfect Remedial.
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For more information on our services, take a look at our webpage or request a free quote.contact us today