Bacchus Marsh Gasworks
The Project
BlueSphere was engaged from 2011 to 2024 to undertake a comprehensive program of soil and groundwater investigations, remedial design, and on‑ground implementation at this former gasworks site. The Crown Land parcel, currently managed by the Department of Transport and Planning (DTP), was subject to a 53X Environmental Audit. The site is located in a sensitive setting adjacent to market gardens, residential receptors, and groundwater users.
Our work included detailed characterisation and delineation of coal tar non‑aqueous phase liquids (NAPL) and dissolved contaminants such as benzene and ammonia. A range of advanced investigative technologies were applied, including sonic drilling, Membrane Interface Probe (MIP) assessments, and NAPL FLUTe liners. Comprehensive human health and environmental risk assessments were completed, addressing risks to extractive groundwater users and a nearby river system.
By 2015, an innovative and pragmatic remediation strategy had been developed incorporating options such as in‑situ chemical oxidation (ISCO) and surfactant‑enhanced mobilisation. A robust Conceptual Site Model (CSM) was established to understand the fate and transport of key contaminants, and this was subsequently endorsed by the appointed environmental auditor.
A Remediation Action Plan guided a pilot ISCO trial in source zones, followed by full‑scale Surfactant Enhanced Aquifer Remediation (SEAR) in 2019. Post‑implementation monitoring confirmed the effectiveness of the approach. This method delivered a more sustainable remediation outcome—requiring fewer chemicals, reduced pumping volumes, and lower overall costs—while enabling treated groundwater to be safely reinjected into the aquifer.
Outcomes
Approximately 18% of coal tar NAPL mass in groundwater was removed through SEAR treatment.
Following achievement of the practical limits of remediation, the Environmental Audit was finalised during 2024 (CARMS Reference: 30327-2).
The former gasworks site has been remediated to the extent practicable and is now suitable for potential divestment and future development, pending decisions by the land manager.
A Check Your Groundwater Area (CYGA) has been recommended for the site and surrounding properties where residual groundwater impacts exceed adopted criteria.
Benefits to Client
Development of a robust hydrogeological and geochemical conceptual model, enabling well‑targeted and cost‑effective investigations.
Delivery of a pragmatic remedial strategy that supported successful completion of the Environmental Audit.
Tangible site improvements achieved through significant reduction of source‑zone contaminant mass.
Use of an engineered non‑ionic surfactant allowed efficient mobilisation of recalcitrant contaminants, enabling a relatively short six‑month SEAR operating period and supporting future divestment of contaminated surplus government land.