04 August 2020

Port Pirie River before the upgrade

A new study has found deposits of heavy metals, including silver, in underwater sediment near the South Australian regional town of Port Pirie, which could be worth up to $40 million.

The University of SA study found levels of lead, zinc, cadmium, copper, arsenic and silver in the top layer of sediment surrounding the town exceeded national environmental standards, in some cases by a factor of 50.

The study also suggested dredging the top 80 centimetres of sediment could be a commercially viable way to reduce metal pollution which has plagued the city since it began smelting lead over a century ago.

The investigation estimated there to be over 3,000 tonnes of lead and about 4,500t of zinc in the Port Pirie River as well as a separate smelter effluent dump called First Creek.

However, it was high levels of silver — a predicted $24 million worth — that the report said could make a dredging effort worthwhile.

Lead smelter owner Nyrstar told researchers silver pollution was likely a result of an "historic leak from the precious metals refinery", which had "occurred over many years".

The operator said it removed the refinery and recovered the lost silver from the smelter site, but did not know how much silver had leached into the greater environment.

A well-known problem

The study showed heavy metal contamination continued to be a huge problem for the regional city.

It noted lead and cadmium pollution was particularly worrying given the metals were: "amongst the most toxic of metal contaminants and are known to induce neurological disorders and multiple organ damage even at low levels of exposure".

Though the pollution means the commercial fishing of mussels and some fish is banned, the study notes: "little awareness exists in the local community and [mussels] remain a target species for local recreational fishers".

It also highlighted a negative impact on marine species' diversity and habitat.

"Metal contamination decreases species diversity, changes community structure, results in abundance and biomass decline and degrades habitats," the study said.

"Consequential effects can include reductions in both marine resource yields and ecosystem services."

Removal could 'broaden' city's interests

The report said that in the past the cost of disposing of dredge spoil made dredging prohibitively expensive, and the port had become too shallow for many larger commercial ships.

"Siltation has resulted in only shallow draft vessels being able to be used under tidal restrictions," it said.

The study also found that dredging the top of the silt would align with shipping requirements and save the estimated $4 million a year of shipping capacity the city was losing out on.

It said removing the waste would "encourage the clean-up of pollution legacies" and would broaden the city's "industrial, recreational and tourism interests", which were currently limited by the contamination.

Next research phase in jeopardy

Researchers say the next phase of the study, which would have involved the creation of a roadmap to practical a solution over a three year period, is now in doubt.

UniSA researcher Hazel Vandeleur said despite smelter operator Nyrstar having jointly funded the current study with Uni SA, Flinders Ports and SA's Environmental Protection Authority, the company had pulled out of funding the next phase.

She said unless funding came from elsewhere progress would not be made.

"Obviously, with the removal of one of the partners, there is a possibility that the project will not go ahead," Ms Vandeleur said.

"We would love the State Government on side — this is part and parcel of the economic development in the area.

"We all think this would be an opportunity lost if it did not go ahead due to funding."

ABC North and West SABy Gabriella Marchant 
Posted Tuesday 4 August 2020