On 6 January 2020, there was an uncontrolled release of 300,000 litres of hydrochloric acid from three chemical storage tanks at a site in West Thurrock, Essex. The toxic hydrogen chloride gas cloud this created resulted in schools in the area closing and local residents being told to shut their doors and windows. Less than nine months later, a crack in a pipe on the same site resulted in the release of 87,000 litres of sulphuric acid into the local atmosphere.
HSE Principal Inspector Maria Strangward, working alongside inspectors from the Environment Agency, investigated these incidents.
The incidents
‘There were two incidents in this investigation. The first involved the loss of containment of approximately 300,000 litres of hydrochloric acid,’ said Maria. ‘Although nobody was injured in the incident, due to conditions, the hydrochloric acid reacted with water and formed a plume of hydrogen chloride gas cloud that then drifted off site, towards nearby towns, posing a risk to local residents in Thurrock, Purfleet and Chafford Hundred. Hydrogen chloride is a toxic gas and inhalation causes irritation of the eyes and nose with sore throat, cough, chest tightness, headache, fever, wheeze, tachycardia and confusion.
The incidents were both caused by a failure of both steel and glass reinforced plastic (GRP) pipework and fittings used to transport the hydrochloric acid and sulphuric acid
‘The second incident involved the loss of containment of approximately 87,000 litres of sulphuric acid. Sulphuric acid is highly corrosive. It causes burns on contact and breathing in air with high levels of sulphuric acid can cause lung damage, shortness of breath and chest pains. In this incident, the risk was to employees dealing with the leak and the clean-up afterwards.’
The investigation
‘The HSE attended the site and the pipe work involved in the incidents was analysed by colleagues from HSE’s Science Division to ascertain the cause of the pipe failures,’ explained Maria.
‘Inspectors, specialist inspectors and regulatory compliance officers were involved in the investigation. The investigation was completed jointly between the HSE and the Environment Agency.’
The incidents were both caused by a failure of both steel and glass reinforced plastic (GRP) pipework and fittings used to transport the hydrochloric acid and sulphuric acid. This equipment failure resulted from a failure to inspect and maintain the pipework and fittings, she said. ‘We found no written scheme of examination was in place, so there was no proactive inspection or examination. The pipework was exposed to conditions that would cause it to deteriorate and it was not inspected regularly or maintained so that defects could be identified and remedied before any failure and loss of containment.’
The company pleaded guilty to charges arising from the two incidents. At a sentencing hearing at Westminster Combined Court on Friday 28 March, the company was fined £2.4 million in relation to charges under the Health and Safety at Work Act and a further £100,000 in relation to charges under the Environmental Permitting (England and Wales) Regulations 2016.
Source – IOSH
