What is Groundwater and the Aquifer?
Groundwater is the general term used for water found under the ground, as opposed to surface water, which is commonly in the form of a pond, lake, creek, stream or river. Groundwater runs at different depths under the ground and, just as any river, it has its own direction of flow (which is influenced by gravity, hydrostatic head [water pressure] and ground permeability). Below Botany Industrial Park (BIP) , the shallow groundwater runs at depth of 3-7 m in a south-westerly direction.
A body of underground water is known as an aquifer. The surface of aquifer is known as the water table, which varies in depth. Apart from ground surface physical features (topography) and underground soil or geological features, seasonal changes and rainfall affect the depth of water table. Close to the sea, tidal changes can also affect the water table.
What is a Contaminant Plume?
A contaminant plume is a mass of contaminated water that extends outward from the source of the contamination. It is similar to a plume of smoke from a smoke stack.
The principal source of groundwater contamination at BIP are chlorinated hydrocarbons (CHCs), referred to as Dense Non-Aqueous Phase Liquid (DNAPL). As the name suggests, DNAPL is denser than water and is not very soluble. It can be found in the aquifer in the form of small droplets residing in the pore spaces between soil particles, and as thin pools lying on top of layers of low permeability matter (e.g. peat, clay or rock).
Groundwater Contamination at Botany
Contamination of groundwater at BIP was first identified in a survey conducted for ICI Australia in 1990 (view History).
The environmental legacies at what is now known as BIP date back to the 1940s when manufacturing began at the site. The 1960s saw the introduction of larger manufacturing plants making a wide range of chemicals. This was an era when environmental awareness and standards were far lower than those of today, especially in understanding the potential impacts of chemical use and storage on local soil and groundwater.
During this time, CHCs were stored on-site in tanks and drums. Some of these stored materials leaked into the ground and groundwater. It is likely that contamination was also caused by accidental spills. The main widespread contaminant in the groundwater is ethylene dichloride (EDC). EDC is also known as 1,2-dichloroethane and is a manufactured chemical that is commonly used as a solvent or to make common plastic (polyvinyl chloride or PVC). This chemical along with other CHC contaminants are no longer manufactured at BIP.
CHCs listed in the VMP
|Volatile Chlorinated Hydrocarbons
||Semi-volatile Chlorinated Hydrocarbons
|Carbon Tetrachloride (CTC)
|Vinyl Chloride (VC)
Botany Groundwater Cleanup Project
In response to a Notice of Clean Up Action (NCUA) served upon Orica, the company submitted a Groundwater Cleanup Plan to the NSW EPA in October 2003. The GCP provided a detailed approach for the containment and treatment of the contaminated groundwater. In February 2004, the EPA issued a Variation Notice to the NCUA authorising and requiring implementation of Orica's Groundwater Cleanup Plan. Thus, the Botany Groundwater Cleanup Project commenced.
The Project is now regulated by a Voluntary Management Proposal (VMP).
The Botany Groundwater Cleanup Project is a multi-action approach to contain the contaminated groundwater, prevent it from entering Botany Bay, and treat the contaminated groundwater for non-potable reuse. It has involved the design, construction and operation of the Groundwater Treatment Plant (GTP), an extensive environmental monitoring and reporting program, and the ongoing evaluation and, if practicable, implementation of dense non-aqueous phase liquid (DNAPL) source area investigations and removal technologies.
Outline of the Project:
Treatment of the groundwater at the GTP achieves a water quality that is suitable for non-potable reuse, thus reducing demand on Sydney's water supply. For more information, visit the Water Recycling Program.
Orica provides quarterly progress reports*# on its implementation of the Groundwater Cleanup Plan to regulatory authorities and the community, along with results of surface and groundwater monitoring.
* Groundwater and surface water monitoring results are reported as an appendix to quarterly progress reports.
# Monitoring results for the GTP are reported on the Monitoring Results page.