Cost‑Efficient Remediation for Hydrocarbon Contamination — Newcastle & Wollongong, NSW

Project summary

Surface staining of unsealed ground was observed at three sites in the Newcastle and Wollongong areas. iEnvi conducted targeted soil sampling in the stained areas. Laboratory results identified subsurface hydrocarbon contamination at two of the sites, with detected impacts to depths of up to 0.5 m below ground surface.

Investigation and findings

An iEnvi Environmental Scientist attended each site to collect targeted soil samples where surface staining was present. Results confirmed shallow hydrocarbon contamination at two sites (maximum reported depth ~0.5 m). The third site showed no subsurface hydrocarbon impacts in the sampled locations.

Remediation approach recommended

iEnvi recommended a pragmatic, cost‑efficient response that could be completed by the site operator. The key elements were:

• Treatment of the delineated contaminated soil in situ with a biological additive (reported product: S200 OilGone) to stimulate indigenous hydrocarbon‑degrading bacteria;
• Excavation of the treated, delineated soil areas to remove residual free product and contaminated material;
• Immediate and permanent encapsulation or appropriate containment of excavated/treated material to protect workers and the environment and to reduce human health and ecological risks associated with the soil.

What the treatment is intended to do (plain English)

• Biological additives are intended to accelerate natural breakdown of hydrocarbons by providing nutrients or compounds that support indigenous microbes.
• Treatment prior to excavation can reduce free product and make excavation handling safer and potentially reduce disposal classification and cost.
• Encapsulation provides an engineered barrier to prevent exposure pathways to workers, the public and ecological receptors.

Practical implications for clients and developers

• Time: Combining targeted treatment with focussed excavation can shorten remediation schedules compared with large‑scale wholesale excavation.
• Cost: Targeted approaches reduce excavation volumes and transport/disposal costs, delivering a cost‑efficient outcome when contamination is shallow and well‑delineated.
• Compliance & risk: Documented investigation, treatment and validated excavation/encapsulation reduces legal and environmental risk and supports due diligence for property transactions or development approvals.

Key takeaways

1. Targeted sampling is essential — this project showed contamination at two of three visually stained locations, with impacts limited to shallow soil (≤ 0.5 m).
2. Biological treatment additives can be a cost‑effective component of a remediation strategy when combined with delineation and targeted excavation, but product claims should be validated by vendor data and laboratory results.
3. Maintain clear records (chain of custody, lab reports, volumes excavated, disposal documentation and final validation sampling) to support regulatory compliance and commercial transactions.

Next steps and how iEnvi can help

If you require a legally and financially defensible multiple‑site due diligence assessment for M&A, development or a remediation strategy, iEnvi can scope and deliver investigations, vendor evaluation, treatment validation and managed excavation programs.

Contact iEnvi — call 13000 43684 or submit a confidential enquiry via our contact page.