PHOTOS: Boyne Basin prawn farm rehabilitation continues
THE rehabilitation of an abandoned prawn farm at South Trees is entering its second stage.
The 2ha area is in a tidal zone in the Boyne River Basin and in the 1990s was leased by Vijay Ram as a prawn, mud crab and barramundi farm.
Its closure was shrouded in mystery but, according to State Government documents, the owner walked away from the aquaculture operation in 1999.
Those documents also suggest high levels of acid sulfates in the soil might have been the reason for this.
For 10 years the site was left abandoned.
In May 2011 Gladstone Regional Council lodged a statement of claim to recover rates worth $7873.07.
But Mr Ram's lease had expired, and therefore the rates were not recoverable.
In 2012 a State Government tender was issued to develop a plan to rehabilitate the land. The first stage of rehabilitation was carried out in April 2013. Tenders to carry out the second stage closed earlier this month.
That's raised new concerns for geologist, engineer and Gladstone Conservation Council president Jan Arrens who said disturbing the whole site further could cause severe environmental damage.
The soil is naturally rich in acid sulfates, a common material in coastal waterways. But when that soil is dug up and mixed with oxygen, as it was during the construction of the prawn farm, it creates sulphuric acid, a highly corrosive material.
If left untreated, those bund materials will continue to produce and release acid as they oxidise over time.
Field and laboratory measurements performed by the state government from the two ponds show the pH level of the water is pH2-3.
That's below Australian standards for a healthy waterway.
Each time it rains that acidic water with harmful metal concentrations is leached into the surrounding environment.
Mr Arrens said those metals could also make their way into the food chain.
"If (those chemicals) are absorbed by the algae, the algae is eaten by a shrimp, a fish eats the shrimp and then we eat the fish - those (chemicals) will get into our bodies creating long term carcinogenic exposure," Mr Arrens said.
He is also concerned about aspects of the state government rehabilitation strategy.
"One proposal is to draw the local water table down," Mr Arrens said.
"They are proposing to go around the perimeter and drain the water but when you remove the water you bring it out of an anaerobic zone (an oxygen poor environment) which makes the problem worse.
"(But) The most responsible way of dealing with it now would be to backfill the whole area in clean sediment sand."
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