What is Orica Doing about the Groundwater Contamination?
- Created three different hydraulic containment areas and installed groundwater extraction wells at:
- Primary Containment Area (PCA) - McPherson Street and Southlands
- Secondary Containment Area (SCA) - Foreshore Road
- BIP Containment Line - north-west boundary of the BIP and west of the Groundwater Treatment Plant
Locations of the hydraulic containment areas (while lines)
On an ongoing basis, Orica is:
- Extracting and pumping contaminated groundwater from the Primary, Secondary, and BIP Containment Areas
- Operating the GTP to treat groundwater
- Conducting various monitoring programs:
- Groundwater monitoring*
- Surface water monitoring*
- Hydraulic monitoring*
- Monitoring GTP emissions#
- Investigating contaminant DNAPL source areas and remediation/depletion technologies and options
- Liaising closely with the community and government agencies
# Monitoring Data for the GTP
* Groundwater and surface water monitoring results are reported as an appendix to the quarterly progress reports.
Progress to Date
Hydraulic containment and operation of the GTP has resulted in:
- Effective contaminant containment at the SCA, intercepting the groundwater plume generally referred to as Central Plume (the groundwater in the area flows in a south-westerly direction), and significantly reducing the direct discharge of CHCs in groundwater into Penrhyn Estuary;
- Major improvements to surface water quality in stormwater drains (Springvale and Floodvale Drains), which run through the local industrial area (refer to figure below). This results from the general lowering of groundwater levels in the area that in turn minimises the discharge of contaminated shallow groundwater to the drains;
- Improvements to ambient air quality immediately adjacent to Springvale Drain in Orica Southlands and nearby areas. This results from the improved surface water quality in the drain;
- Significant and consistent improvement to the quality of surface water at Penrhyn Estuary (where the stormwater drain discharge) and Botany Bay with regard to CHC contamination. Surface water discharge from Springvale Drain and Floodvale Drain has historically formed the dominant contributor of CHC surface water concentrations in the estuary and bay; and,
- Management of overall human health and environmental risks assessed in the Consolidated Human Health Risk Assessment.
In the past, Orica has also:
- Relined stormwater pipes between BIP and Springvale Drain, preventing the ingress of contaminated shallow groundwater into the pipes and the subsequent discharge of that contaminated groundwater into the drain;
- Removed contaminated sediments from the bottom of Springvale Drain to prevent them from being carried downstream to Penrhyn Estuary; and
- Distributed treated water for reuse by BIP and neighbouring industries (see Treated Water Recycling Program).
Aerial image of local area depicting BIP, Orica Southlands, Floodvale and Springvale Drains and Penrhyn Estuary
Groundwater Cleanup Challenges
The lowering of CHC concentrations in groundwater and the rate of aquifer cleanup from 'pump & treat' is slow, especially because DNAPL source materials continue to dissolve into groundwater plumes. As at the end May 2012, Orica has removed and destroyed 987 tonnes of CHC contamination (the equivalent of roughly one-quarter of the volume of an Olympic swimming pool) from the Botany Sands Aquifer (for an update on the total destroyed CHC volume, refer to the latest progress report). Over the past five years the average concentration of CHC's has fallen from 73 mg/L in 2008 to 54 mg/L in 2012. The data provides an indication that groundwater extraction will need to continue for many years.
Orica conducted reviews of the cleanup strategy for the Botany Groundwater Cleanup Project during late 2007 and 2008 and again in 2011. As part of the 2007/2008 review, Orica completed a number of studies to improve the understanding of the scale of the groundwater contamination, including estimates of the contaminant mass in the aquifer and solute transport modelling to predict the potential cleanup duration under various cleanup scenarios. The review concluded that hydraulic containment using 'pump & treat' may need to continue for hundreds of years or until new technologies become available to improve the efficiency of contaminant removal. For further details on the Botany Groundwater Strategy Review, click here .