Balu

On 20 March 2001, the chemical tanker the Balu, transporting 8,000 tonnes of sulphuric acid, sank in a storm in the Bay of Biscay. She now lies on the sea bed at a depth estimated between 4,600 and 4,800 metres, at the limit of the French and Spanish territorial waters, at about 120 nautical miles in the north of La Coruna. Cedre was asked to assess the possible consequences for the marine environment.

Sulphuric acid is denser than water (d = 1.84). We can therefore safely assume that if the acid did not sink inside the tanker, it immediately followed the vessel to the bottom of the sea, gradually dissolving as it went.

In the absence of a sudden exothermic reaction when the acid sank, the risk incurred by marine flora and fauna was a risk of mortality due to strong acidification of their habitat, situated near the shipwreck. The acid would have dissolved in the seawater, which has a strong neutralizing capacity and represents a huge volume. The pH would therefore return rapidly to its original level in the area affected.

 
At the depth in question, the sea bed populations have a low biomass per surface unit, are low in diversity and are not the subject to any exploitation. There is therefore no risk in terms of fishing, and the environmental impact is too temporary and localized to be quantified.

Accidents caused by chemical tankers transporting sulphuric acid, a highly corrosive product, are a well documented risk in the accidental sea pollution archives.