THE Environmental Protection Authority has ordered chemical giant Orica to clean-up arsenic contaminated groundwater at its Kooragang Island site.
Groundwater beneath the site is significantly contaminated with arsenic historically used in ammonia production.
Orica dealt with the principal source of the arsenic contamination shortly after it took control of the site in 2005, but now the EPA has ordered it to begin the clean-up stage of the remediation.
“Since  the residual contamination in groundwater has been the focus of significant investigations and remediation trials by Orica to determine its extent, impact and to identify appropriate remediation options,’’ the EPA’s director of hazardous incidents and environmental health, Craig Lamberton, said.
The management order was issued last week, and the remediation must be completed by the end of 2017.
The order requires Orica to implement work to prevent any more contaminated groundwater leaving the site, as well as requires community consultation, groundwater monitoring, an updated environmental management plan and an independent validation report on implementation of the remediation technology.
In a statement Orica said it was ‘‘assessing the available options for remediation as outlined by the EPA’’.
It said it would also develop a groundwater monitoring program for the arsenic contamination. ‘‘Independently reviewed studies have shown that with appropriate management, the contamination does not currently pose an unacceptable risk to either the environment or human health,’’ it said in the statement.
The groundwater contamination at Kooragang is the result of an old industrial process used in the ammonia plant between the early 1970s and 1994. Orica assumed management of the site in 2003 and undertook contaminant source removal work in 2005.
In the last eight years the company has spent about $10 million on investigations into further remediation options.
The EPA order comes after the Land and Environment Court last month handed down more than $750,000 in penalties to the company for a series of pollution incidents at Kooragang Island and Botany, including the 2011 leakage of toxic hexavalent chromium over Stockton.
The EPA said the total sum was the highest penalty ever levelled at a company for a matter it had prosecuted.