Hydro Aluminium Kurri Kurri Smelter

The Hydro Aluminium Kurri Kurri (HAKK) Smelter was one of six smelters producing aluminium in Australia until closure in 2012. Since this time, Hydro has embarked on a decade-long campaign to meet its environmental obligations for decommissioning, demolition and decontamination to the highest standards.

In our effort to help our client achieve sustainable change, Ramboll completed all the environmental investigations at the Smelter Site and the surrounding Buffer Zone, which includes valuable biodiversity. The driver for remediation was long-term stockpiling of aluminium smelter waste at the site, which had led to a leachate plume impacting shallow groundwater and vegetation growth in a portion of the Buffer Zone.

Ramboll finalised the Remedial Action Plan (RAP) in 2018 with on-site containment of aluminium smelter wastes and contaminated soil in a purpose-built Engineered Containment Cell (ECC) designed to the highest engineering standards selected as the remedial solution. As part of the remedial options assessment, Ramboll completed a Net Environmental Benefit Analysis (NEBA) which identified on-site containment as the most sustainable remediation option.

Implementing the RAP has involved multi-disciplinary teams completing several separate but interlinked projects:

• Interim storage of process wastes and contaminated soil
• Demolition works
• ECC construction and filling

Ramboll led all environmental and remediation works, including multiple rounds of investigations for a range of contaminants of concern associated with aluminium smelting and activities in the Buffer Zone, which included hobby farms and a municipal landfill. Ramboll has progressively completed validation reporting as remedial works at the Smelter Site and in the Buffer Zone have been completed.

In the past, decommissioning, demolition and decontamination of major industrial facilities have been completed as separate projects with divergent objectives. At industrial facilities where contamination has been capped, decontamination of subsurface infrastructure has not been required. This has led to long-term management and can impact on future redevelopment.

At the HAKK Smelter, the objective of the RAP was to render the smelter suitable for commercial and industrial land use with no long-term management requirements aside from the footprint of the ECC. This requirement led to innovative engineering solutions that have contributed to both technical knowledge and contracting processes within the contaminated land profession.

Demolition and decontamination works were completed by CMA Contracting in collaboration with Ramboll. The age of the HAKK Smelter and the layout provided challenges for both CMA and Ramboll. The timing of construction in 1969 meant that materials were used that are now recognised as hazardous.

During demolition works, CMA and Ramboll implemented the RAP requirements but went beyond these to develop a more formalised methodology that allowed provision of required information for validation reporting.

Demolition works were sequenced to manage contamination risks, with specific risks such as asbestos and PCBs managed by specialist subcontractors. Over 80 separate Work Method Statements were developed and implemented, taking 150,000 work hours over four years with zero lost time injuries.

The methodology and engineering solutions implemented by CMA allowed Ramboll to validate that demolition works did not cause cross-contamination.

The preparation of specific validation reports, including a Demolition Validation Report, Subsurface Asbestos Validation Report and Substations Validation Report, has resulted in the sale of a portion of the Smelter Site for early redevelopment as part of the Snowy Hydro Hunter Power Project. This milestone could not have been achieved without a technically capable multi-disciplinary team focused on delivering a high standard of remediation engineering.

At the completion of demolition works, Ramboll and CMA created a digital twin of subsurface infrastructure remaining below 1.5 m bgs, including retained concrete pits, footings and services. The digital twin was developed using Hydro engineering drawings covering the layout of the entire smelter, with a link to these drawings in the GIS database.

This digital twin will provide useful information to site developers, who will be able to plan construction works around remaining subsurface infrastructure. This will reduce risks with unknown ground conditions in the future.

The lessons learnt on this project can be carried forward to provide a framework for best practice decommissioning, demolition and decontamination of large-scale industrial facilities into the future.