Remediation work valued at approximately $100M was undertaken by Thiess Services during the Lednez and Homebush Bay Remediation Project. Land-based remediation works concluded at the ten hectare former Lednez/Union Carbide site in Rhodes, NSW, in March 2011, while the remediation of parts of Homebush Bay concluded in August 2010.
During the project, Thiess Services closely consulted the City of Canada Bay Council and State Government departments including the Department of Environment, Climate Change and Water (DECCW), the Department of Commerce, NSW Health and the Department of Planning. Stringent health and environmental standards were set for the project.
The former Lednez/Union Carbide site became contaminated as a result of its long-time use for chemical manufacturing, including the manufacture of pesticides. Lime and ash wastes containing chemical residues were used to fill foreshore areas of the site and of the neighbouring site, owned at the time by the Allied Feeds company. As well as contaminating the land-based sites, this form of land reclamation resulted in contamination spreading into Homebush Bay.
The principal contaminants of concern which made the remediation necessary were dioxins, by-products of the chemical manufacturing processes. Thiess Services’ work included the staged excavation and classification of soil and sediment, treatment of contaminated material using "directly-heated thermal desorption" and the reinstatement of material on site that met the soil reuse criteria (with or without treatment). The soil reuse criteria were developed to protect both human health and the environment. A Site Auditor accredited by the DECCW approved the criteria.
The quantity of excavation material for the project was approximately ~900,000 tonnes of soil from the land site and ~50,000 tonnes of sediment from Homebush Bay.
Removal of organic contaminants from the soil and sediment was undertaken on site using a directly-heated thermal desorption (DTD) plant and 82,000 tonnes of material was treated.
The State Government acquired the site in 1999 from the Lednez company (formerly the Union Carbide company). Now remediated, the site will provide a safe location for the development of residential apartments and public open space with direct access to the bay foreshore.
Thiess Services established the remediation site in June 2005 and excavation work commenced in December of that year. The project was completed in March 2011.