Altona Properties Pty Ltd (APPL) operated a polyvinyl chloride (PVC) manufacturing facility at its 16 ha (40 acre) site until February 2002. Until 1978, the PVC monomer vinyl chloride was manufactured on-site from cracking 1,2-dichloroethane (EDC), which was manufactured on the adjacent Dow site and supplied to APPL by an above-ground pipeline. APPL’s manufacturing processes resulted in impacts of EDC and its related tars to soil and groundwater on the site. In fact, they resulted in a groundwater plume that extends some 500 m (1,650 feet) south of the site boundary.

This plume has posed a large problem for APPL for two primary reasons:

• It is prohibitively expensive to remediate all of the contamination, which is bound in weathered basalts (clays) and basalt fractures in soil and groundwater extending some 40 m (130 feet) below the site surface and 500 m (1,650 feet) off-site.
• Remediation technologies used in similar situations have had their own environmental impacts, such as the generation of greenhouse gases, other gases that could include toxicants, and wastewater.

As a result, APPL chose a general sustainable approach to the treatment that was community-based, included source treatment and monitored natural attenuation. PB’s role has been innovative in supporting community consultation, providing complete electronic documentation to meet EPA licence requirements, and managing a new technologies— a special metal catalyst to remediate (destroy) chlorinated solvent contaminants. Our effort involved careful planning and presentation of information to stakeholders who required education and needed to develop confidence in our ability to employ a new technology.

The Environmental Setting

The site generally comprises thin (0.5-m to 2-m, or 2-foot to 7-foot) -thick layers of silty clay and fill surface material overlying basalt to nominally 30 m to 50 m (100 feet to 165 feet) below ground level (mBGL). Two aquifer intervals that may be hydraulically connected (referred to in this article as the upper and lower basalt aquifers) were identified in the basalt by previous works ^{1, 2.}

Soil investigations indicated the extent of surface soil contamination was confined primarily to the top 2 m (7 feet) of weathered basalt and included free-phase product at the clay-basalt interface. Shallow surface contamination was evident in the:

• Former tar storage area (south-west corner) in the form of polyaromatic hydrocarbons, total petroleum hydrocarbons and monoaromatic hydrocarbons
• Former EDC plant area in the form of EDC and VCHs.

These two areas are “hotspots,” or source zones, for contamination of the subsurface and groundwater.

Selecting the Approach to Contaminant Treatment

APPL is involved in a number of community consultation groups concerned with issues specific to the site and the Altona Chemical Complex as a whole. As a result of the efforts of one such group, which includes as members local residents, representatives from the Environment Protection Authority (EPA), APPL management, neighbouring companies and Hobsons Bay Council, a treatment strategy was adopted that called for source zones to be identified on the site and for APPL to commit to treating those zones. Source zones were defined as those with highly raised concentrations of chlorinated solvents, probably indicative of dense non-aqueous phase liquids (DNAPLs) in the vicinity. Source zones were determined to include shallow basaltic clays, basalt above standing water levels and groundwater.

It was recognised that technologies required for the treatment were in development or unproven, and the heterogeneity of the site would make uniform and complete treatment impractical. For these reasons, the treatment strategy included the following steps:

• Treatment targets would be subject to further assessment of what was practical and consideration given to the environmental costs and benefits of continued operation.
• Groundwater outside the source zone would be treated by natural attenuation and a monitoring programme would be implemented to assess long-term plume trends and highlight any unexpected developments.
• Where possible, all wastes would be treated on-site and discharges would be compliant with regulatory requirements.

Contaminant Treatment

The following methodology is being used to meet the above strategy:

• Chlorinated solvents are removed from groundwater and vadose source zones by a combined air sparging/soil vapour extraction system.
• Off-gas treatment is by catalytic oxidation followed by caustic scrubbing of the hydrogen chloride generated by the oxidation process. Catalytic oxidation at 450°C to 490°C (842°F to 914°F) minimises the generation of polychlorinated dibenzo dioxins (PCDDs) and polychlorinated dibenzo furans (PCDFs) that may occur at higher temperatures (notably at 750°C to 900°C, or 1,382°F to 1,652°F).
• Off-gas is emitted to the atmosphere under a Waste Discharge License negotiated with the state EPA.
• Scrubber effluent containing sodium chloride is disposed to the sewer under a Trade Waste Agreement.

More traditional remediation approaches including groundwater extraction and carbon stripping of extracted vapours were assessed, but discounted due to the large volumes of hazardous wastes they produced. The use of catalytic oxidation (the technology itself sourced from the U.S.) was the first such application in the remediation of chlorinated solvents in Australia.

To date, a total in the order of 16 tonnes of chlorinated solvents has been removed and treated from beneath the former Altona chemical plant. This feat demonstrates the success of both the process and technology in achieving environmental remediation.