The manhole on a 33% hydrochloric acid (HCl) cistern tore open at a Seveso site packaging and distributing chemical products. Fire-fighters arrived along with a chemical emergency squad and a doctor. The driver was seriously injured and taken to hospital. A spread of HCl could be neutralised with soda ash. Due to the acidic fumes, a foam blanket was deployed and the 45 employees evacuated from the site until 12:30 pm. The HCl was collected in a retention basin. The classified facilities inspectorate and labour inspection, as well as the gendarmerie, made a site visit the very same day.

According to witness accounts, the lorry arrived onsite at 10 am and the reception protocol was strictly followed: company/cargo verification; issuance of required procedures written in the driver’s native language (Spanish), though the driver was already familiar with the site; ADR accreditation, layout, etc. The vehicle drove over the track scale and entered the acid transfer zone. The manhole was opened for sampling (inspections of type/quality of delivered product) then shut. The driver and a technician hooked up the hoses at 10:30 am; next, the cistern was pressurised at between 1.8 and 2 bar absolute. The manhole started leaking soon after compressor start-up. The technician proposed lowering the pressure, but the driver climbed atop the cistern to identify the cause of the leak and tighten the ribs closing the manhole with a hollow iron bar wielding a strong leverage effect. The ribs broke at 10:50 am, ejecting the manhole cover at the driver’s face, who also inhaled vapours, received a splattering of HCl and fell into the cistern despite the safety railing; 1 tonne of HCl was expelled from the pressurised cistern.

The inspectorate noted that it had not been informed and moreover that the internal emergency plan, had it been activated, would have improved coordination of actions without overlooking: caring for the injured while waiting for the fire services physician to arrive; responding to the HCl spread and open cistern, whose inaccessible manhole had not been anticipated; respecting the order of a pre-established call list. Other anomalies were also recorded, including a transfer zone that was without retention, unsealed and (like the retention on the fixed HCl reservoir) with a lining non-resistant to acids. The inspectorate in November 2008 had already requested the operator to ensure sealing the basins and providing an assessment. Lastly, several bulk containers had no retention, while others noncompliant with the compatibility rules for stored products had already been addressed in both November 2008 and May 2009.

The soiled excavated earth was treated at a certified facility; the operator had to submit paperwork on eliminating both the waste generated from neutralising the spread of HCl and the polluted ground. The prosecutor appointed an expert to determine the causes of this accident: inappropriate driver response, worn and cracked cistern joint,