Remediation of Soil Contamination – Lessons Learned

A site in Kingaroy used as a livestock dip from 1917 and council workshops and truck sheds from 1950 was found to be contaminated with arsenic, chromium and petroleum hydrocarbons.

The 2.6 hectare site in the South Burnett Regional Council area had a number of contaminants of concern and the site was listed on the Environmental Management Register (EMR):
– Arsenic contaminated soil from the former cattle dip
– Chromium from a large stockpile of imported fill
– Petroleum hydrocarbons from the workshop / oil sump, washdown bay, flush pit, underground fuel storage (USTs), bitumen storage / heating areas, truck sheds.

The site presented an opportunity for redevelopment and being surrounded by public parkland, houses and commercial premises, the contamination on site needed to be removed.

The arsenic contaminated soil required treatment and disposal offsite under a Soil Disposal Permit to Underground Storage Tanks (USTs).

The hydrocarbon contaminated soils required onsite bioremediation.

IMEMS, a local environmental services business was engaged to investigate and remedy the soil contamination.

They utilised the in-field arsenic detection equipment, Field Portable X-Ray Fluorescence (FPXRF) to target arsenic contamination.

Director Paul Anderson said “using in-field contaminant detection equipment such as FPXRF (for arsenic) takes a little longer during excavation works, but it reduces the total amount of contaminated soil required for disposal which in turn cuts emissions and time.

“In-field rapid detection equipment such as FPXRF allows field staff to quickly determine the elemental composition and indicative concentration of heavy metals and arsenic in soil”.

“The advantage is that use of FPXRF in the field can significantly also reduce project costs through lowered sampling and analysis requirements and the associated time delays, contractor equipment stand-down etc”.

For hydrocarbon contaminated soils, there is an opportunity for on site bioremediation when there are minimal inorganic contaminants and high concentrations of biodegradable hydrocarbons. Laboratory trials show that some hydrocarbons can be bio-remediated following addition of nutrients and compost.

There were a number of “lessons learned” in the clean-up of this soil contamination project:
– Ensure initial desktop investigation is thorough.
– Speak to the right people who had historic involvement with the site.
– If possible, require statutory declarations from information suppliers.
– What is thought to be the limits of contamination based on early investigations is not necessarily what you will find when you commence remediation earthworks.
– The weather may disrupt, hamper or derail remediation efforts.
– Manage your neighbours well.
– The timeline and budget for such a contaminated land project has the potential to blow out.
– Stockpile management can be a challenge
– Utilise appropriate machinery and skilled professionals.
– The client, consultant, auditor and contractors can work well together given opportunity.
IMEMS is currently undertaking similar projects at large former heavy industrial sites in North Qld.

For more information about Remediation of Soil Contamination,
see CISC member IMEMS Environmental.

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