The Use of Treated Timber for Oyster Farms

Timber is a preferred material for construction of the frames, racks and trays employed in oyster farming; the oysters attach to (and grow on) meshes made from non-corrosive materials that are fixed to the timber components.

Preservative treated timber provides an effective alternative to the use of untreated naturally durable native forest timbers.

The preservatives commonly used to treat timber for exposure in the marine environment are CCA and creosote / PEC, applied either separately or as "double treatment".

Studies of barnacles growing on treated timber piles ⁽¹⁾ indicate that some uptake of copper and chromium occurs in these shellfish - but when double treated timber is used (CCA plus creosote) the levels of Cu and Cr uptake is much reduced; arsenic does not appear to be picked up by the barnacles from the treated timber. These studies have also shown that CCA does not contaminate the seawater in the immediate vicinity of the piles.

It is important to note that CCA-treated and creosote / PEC-treated timber should not be used in direct contact with foodstuffs. And of course this applies equally to such preservatives when used to treat the timber components used in oyster farming. However, unlike the barnacles in the above study the oysters are not grown in direct contact with the treated timber. Thus, there is no risk of oyster contamination with the treatment chemicals.

⁽¹⁾ D.K. Scown and L.J. Cookson (1999). Copper-Chromium-Arsenic Levels in Barnacles Growing on Timber Marine Piles. 10th International Congress on Marine Corrosion and Fouling. University of Melbourne, February 1999: Additional Papers