Management of CPWE
The Car Park Waste Encapsulation (CPWE) is managed in accordance with criteria from the Australian and New Zealand Environment and Conservation Council's (ANZECC) HCB Waste Management Plan (November 1996), which details requirements for other similar wastes (primarily HCB) stored at Botany Industrial Park (BIP). The CPWE is regulated by the Office of Environment and Heritage (OEH) under Orica's Environment Protection Licence (EPL) and Environmentally Hazardous Chemicals Act Licence. Reports on the management of the CPWE are submitted to the OEH on a six-monthly basis in accordance with the relevant conditions of these licences.
As part of the management process, Orica conducts routine visual inspections of the car park site and its surrounds, and monitors groundwater and soil vapour emissions in the vicinity of the CPWE on a six and fifteen-monthly basis, respectively (Environmental Monitoring Reports).
Infiltrated Water Collection and Treatment
Orica has been removing the relatively small volume of water (i.e. rainwater) that seeps in the CPWE and collects in the drainage lines by pumping it to portable bunded drums situated on the car park site. The collected and stored water is then transferred to the Groundwater Treatment Plant for treatment. The water contains very low concentrations of contamination.
Previous Management Works
During 2004, when Orica was investigating options for long-term remediation of the CPWE, the results of groundwater and soil vapour emission monitoring inferred that vapour was permeating the liner and consequently having an impact on the groundwater below. This triggered the need to reassess the impact of the vapours on workers, neighbours and the broader community in the vicinity of the CPWE. A Human Health Risk Assessment of the CPWE was conducted by Orica's environmental consultant URS Australia Pty Ltd. The conclusions stated that 'no unacceptable risks to human health have been identified' from the emissions of vapour from the car park surface and surrounding banks.
As a precautionary measure, Orica undertook works in mid 2005 to minimise the migration of vapours out of the embankment soil and to minimise infiltration of surface water, thus limiting the pathway for contamination of the groundwater. The eastern embankment of the CPWE was capped using a High Density Polyethylene liner, which was subsequently covered with top soil. Vapour monitoring wells were installed on site to monitor the effectiveness of the capping system.
Prior to excavations commencing in 2011 for the remediation of the CPWE, Orica regularly monitored and investigated the condition of the CPWE Polyethylene liner. Orica would also remove the relatively small volume of rainwater that seeped into the CPWE drainage lines by pumping it to portable bunded drums situated on the car park site. The collected and stored water would then be transferred to the Groundwater Treatment Plant for testing and treatment.