In April 2012, Orica successfully completed treatment of contaminated soil at the site of the former Car Park Waste Encapsulation (CPWE) using a method known as Directly-heated Thermal Desorption (DTD).
In 2015 the remediated site and some adjacent land was sold for commercial or industrial development. In 2016 Orica conducted civil works required to complete the beneficial re-use of the treated soil.
The CPWE was created when approximately 45,000 m3 of contaminated sand and coal ash was relocated in 1980 to a purpose-built storage facility covered by a car park at the north-eastern end of Botany Industrial Park (BIP) on Corish Circle, Banksmeadow. The waste was encapsulated in a synthetic Hypalon® liner and covered by thick soil walls and asphalt to establish the car park.
The soil in the CPWE was contaminated with hexachlorobutadiene (HCBD) and low levels of hexachlorobenzene (HCB) and hexachloroethane (HCE). HCBD is a waste byproduct with no commercial use that was produced during the manufacturing of chlorinated solvents, such as tetrachloroethene (PCE, commonly used as dry cleaning fluid) and carbon tetrachloride (CTC, an industrial solvent formerly used in the manufacturing of refrigerants). PCE and CTC were manufactured in the former Solvents Plant on BIP from the 1960s to 1991.
The waste was originally drummed and stored on site on a bed of boiler ash. Over time, these drums corroded, leading to contamination of the ash bed and underlying sandy soil.
In the late 1970s, Orica (then ICI Australia) investigated treatment and storage options for HCBD contaminated soil. At the time, there was no suitable technology to treat this soil. The best approach to manage it safely was to encapsulate it, effectively containing the soil in a synthetic liner and storing it underground until an appropriate remediation method became available.
The location of the former CPWE before treatment and a cross-section of its construction are shown in the above images.