Orica remediated the contaminated soil within the CPWE using a treatment method known as Directly-heated Thermal Desorption (DTD).
The CPWE remediation works were regulated by the NSW Environment Protection Authority (EPA) under an Environment Protection Licence (EPL) and Environmentally Hazardous Chemicals Act Licence. Reports on the management of the CPWE were regularly submitted to the EPA in accordance with the relevant conditions of these licences.
The CPWE site was excavated during the remediation project. A building (called the Excavation Soil Building) constructed over the CPWE site enclosed the contaminated soil excavation works. Excavated soil was transported in sealed trucks on internal BIP roads to a Feed Soil Building. Construction of buildings over the soil excavation and handling areas was the best way to manage dust and vapour emissions. Air was drawn out of the buildings through large carbon absorbers that removed the dust and vapours.
The contaminated soil was transferred from the Feed Soil Building to the treatment process via a feed conveyor. The DTD Plant treated the soil in a rotary dryer using heat to vaporise the contaminants into a gas stream. The gas stream contaminants were destroyed in a thermal oxidiser, and dust and acidic gases were removed from the gas stream in a baghouse and acid gas scrubber before it was discharged to the atmosphere through the plant's tall stack. The main components of the treatment process can be seen in the image at right.
The first contaminated soil was processed through the DTD plant in May 2011 and the plant operated until April 2012. The buildings and plant were then decommissioned and removed from site an
d the project was complete in November 2012. The treated soil – approximately 93,000 tonnes – was tested to confirm that the treatment had achieved the remediation goals.
All emissions to the environment were tested in accordance with the requirements of the Environment Protection Licence.
During the project, the Community Participation and Review Committee (CPRC) established a panel of independent experts to provide technical advice to the committee and other interested stakeholders for the duration of the work. Click here for IEP Requests and Reports. The panel and their fields of expertise were (from left to right):
- Dr John McCracken - process engineering: DTD technology, proof of performance trials, operation and plant performance
- Dr Peter Nadebaum - environmental impacts such as noise, odour and water management
- Dr Chris Clunies-Ross - air emissions impacts and assessment of monitoring results
- Professor Brian Priestly - human health risk assessment
Requirements for Future Land use
The CPWE soil was remediated in 2012 to the criteria in the Remedial Action Plan and contaminants have not been detected in ambient air above the soil. However, tests in 2013 showed the continued presence of residual chlorinated hydrocarbon vapour in the soil below the site. The vapour concentrations have been assessed against those concentrations that were considered in the CPWE Human Health and Environmental Risk Assessment, which was incorporated into the Consolidated Human Health Risk Assessment, and are within the range that present no unacceptable health risk.
Review of Risk Issues – Future Use of CPWE Site, January 2014 (PDF 2.2MB)
Orica consulted with the Site Auditor, Chris Jewell, and risk assessor Jackie Wright (Environmental Risk Sciences) and it was determined in early 2014 that a passive vapour mitigation system should be incorporated into the future development of the CPWE area as a precaution against potential soil vapour intrusion into a development on the site.
In May 2014 the Site Auditor issued a Part B Site Audit Statement confirming that the CPWE site will be suitable for commercial industrial use following implementation of a vapour barrier. This marks an important milestone for this long-term project which has seen the safe and successful remediation of approximately 93,000 tonnes of soil contaminated during historical operations at the BIP.
A Part A Site Audit Statement, which confirms the site is fit for occupation, can be issued upon confirmation that the passive vapour mitigation design has been implemented. The vapour barrier is to be installed by a purchaser of the land.
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