A major clean-up of arsenic contamination at Orica’s Kooragang Island plant will begin early next year in an effort to prevent the poison from leaching into the Hunter River.
A 12 meter deep concrete containment cell will be constructed to hold the toxic pollution, which has been found at depths of eight metres below ground level.
The need to clean-up the arsenic contamination was identified about 15 years ago, however, recent testing has shown the contamination has moved to within 250 metres of Hunter River.
“The [contaminated] site extends off site from beneath the former [sludge] pit towards the south arm of the Hunter River,” an environmental impact statement says.
“It is noted that the off-site soil contamination has been caused by absorption from the groundwater plume, rather than being related to any direct discharges.”
The pollution is a legacy of the ammonia manufacturing process that was used prior to 1994.
“Until the 1994 the Vetrocoke process was used to remove (scrub) carbon dioxide from the process gas stream prior to the production of ammonia. The Vetrocoke process utilised a solution containing potassium carbonate and arsenic trioxide to remove carbon dioxide,” the environmental impact statement said.
The Department of Planning recently approved a development application for the $6.5 million state significant containment cell project
The cell will be constructed on site of a former sludge disposal pit, situated in the north-western portion of the plant, that was used for the disposal of solid and liquid arsenic waste for 25 years.
The pit covered an area of about 1500 square metres and remained unsealed until the mid 1980s .
The company has already spent millions of dollars attempting to contain the environmental effects of arsenic sludge dumping on its Kooragang Island site.
At least 15,000 tonnes of material has been removed from the pit.
The environmental impact statement for the containment cell project notes the contaminated soil contains about 40 milligrams of arsenic per kilo.
“It was estimated that leaching of arsenic from soils containing 40 mg/kg would be negligible and would be readily attenuated by the residual soils,” the study says.
An Orica Spokeswoman said the project was expected to take about five months to complete.
“Studies have confirmed that there is a very low level of environmental and human health risk associated with the contamination,” she said.
Stockton Community Action Group spokesman Keith Craig said the project was a welcome development.
“It’s a difficult problem that has taken a long time to come up with a reasonable solution for,” Mr Craig said.
At least this will stop the pollution from getting into the Hunter River.”
The Environment Protection Authority, NSW Health, the Office of Environment and Heritage and the Department of Primary Industries have reviewed to containment cell project. Newcastle City Council has called for the cell’s effectiveness to be audited.
Orica announced in August 2011 that it had accidentally breached its pollution licence by pumping about 1.2 million litres of effluent into the Hunter River with an above-limit concentration of arsenic.
Orica was fined more than $750,000 in July 2014 for seven air and water pollution incidents at Newcastle and Botany.
Orica pleaded guilty in the Land and Environment Court to nine charges for the incidents that occurred between October 2010 to December 2011, the most controversial of which was the leak of hexavalent chromium in the air over Stockton and onto some of its onsite workers on August 8, 2011.
The other incidents included discharges of nitric acid into soil and the Hunter River, and ammonium nitrate and ammonia gas, as well as an emission of mercury vapour from its Botany plant.
For the Stockton leak and the delay reporting it, Orica was ordered to pay $175,000 and $36,750 as a contribution for stage two of the restoration of Kooragang Dykes project to address the deterioration of dykes in the Hunter Wetlands National Park.
Orica global head of manufacturing Richard Hoggards said at the time that the company regretted the incidents and more than $200 million had since been invested in the Kooragang Island plant.