Former ChlorAlkali Plant Mercury Contamination Investigations & Remediation

Orica has been producing chlorine from salt, water and electricity at Botany Industrial Park (BIP) for over 60 years. The original ChlorAlkali Plant used mercury cell technology to manufacture chlorine, caustic soda and other products from 1945 until 2002. In 2002, Orica constructed a ChlorAlkali plant that uses membrane technology. Membrane technology improves the plant's safety, environmental performance and energy efficiency.  Mercury is no longer used in the manufacturing process at the new plant. The former ChlorAlkali Plant was demolished in two stages between 2004 and 2007.

Since 2006, Orica has been investigating soil and groundwater in the vicinity and downgradient of the former ChlorAlkali plant, as well as off-site, for potential mercury contamination. Orica has gathered soil and groundwater data to assess the likely extent of remediation of the former ChlorAlkali Plant area. All of the off-site locations investigated are industrial/commercial areas southwest of the BIP on Beauchamp Road, Banksmeadow.

Part of the former ChlorAlkali Plant site - April 2008

Mercury Contamination Investigation 

Mercury has been detected in subsurface soil at the former ChlorAlkali Plant area, and in groundwater from monitoring wells on and off site. This suggests that mercury in groundwater has migrated downgradient, under off-site industrial/commercial areas (groundwater in the Botany area moves in a south-westerly direction). No dissolved mercury was detected in surface water at nearby storm drains (Springvale and Floodvale Drains) or at Penrhyn Estuary. All of the off-site wells included in these investigations are situated in industrial/commercial areas southwest of the BIP on Beauchamp Road and are within the Groundwater Extraction Exclusion Area, also known as Zone 1 of the NSW Office of Water's (formerly the Department of Water and Energy) Management Zones. Orica has confirmed with the industrial/commercial property occupiers that groundwater is not used at any of the off-site investigation areas. For further details, view Investigations Overview page. 

How did the Mercury Get into Soil and Groundwater?

Mercury was used in the manufacturing process at the former ChlorAlkali Plant. During the 40 years of manufacturing with mercury cell technology, mercury was released into the environment as a result of leakages from pipes and tanks. Some of the mercury also dissolved in the salt solution (brine) used in the manufacturing process. Brine leaks also released mercury to the environment. These leaks resulted in the soil at the plant site being contaminated with mostly elemental and some dissolved mercury. Groundwater flowing through the contaminated soil also becomes contaminated with mercuric salts and mercury micro droplets.

What is Orica Proposing to Do?

Following the successful soil washing trials in August 2008, Orica plans to use this technology to remediate the mercury-contaminated soil at the BIP, commencing in 2010. The extent of the proposed remediation will be determined by the Human Health and Environmental Risk Assessment (HHERA) and specified within a Remediation Action Plan (RAP). The HHERA and the RAP have been submitted to the NSW Department of Environment, Climate Change and Water (DECCW) for its review. Orica is also preparing a Voluntary Management Proposal, which will outline the implementation of the RAP and the establishment of a groundwater monitoring program on and off-site.