At around 7 p.m., technicians in a glass factory observed smoke near a 2,500-litre, 33% hydrochloric acid storage tank. Part of the tank’s content (1,200 litres) had spilt into its concrete retention basin, resulting in the release of acid vapours. In addition, the retention basin was unable to completely confine the release due to a sealing problem. In order to prevent the release of any product outside the site, bladders were inflated to block the sanitation networks. The acid that had spilt into the retention basin was then pumped into containers. During the event, the operator continued to treat its effluent in its waste water treatment plant (WWTP). As the sewerage networks were blocked off, the effluents overflowed into the company’s courtyard.

Causes of the accident

Initial investigations revealed that the leak was caused by a rupture of a drain flange at the bottom of the tank. Limited access to the facilities also made it difficult to reabsorb the release.

Actions taken following the event

The operator took the following actions:

• placement of a stock of soda ash to neutralise acidic discharges, and sandbags for basic releases;
• signage indicating the direction of fluid flow with an updated plan of its installations;
• a new storage tank in a polyethene retention basin which is itself located in a concrete retention basin;
• application of an acid-compatible resin treatment on the concrete retention basin.

The access conditions to the storage facilities are also being reconsidered.