New details revealed about fatal Avonmouth explosion at Wessex Water plant

It has been more than eight months since the Wessex Water explosion killed four workers. Families, friends, and colleagues await the inquiry’s findings, with no end date in sight.

Reports 11th August, 2021

Alon Aviram

Wessex Water staff have described their frustration at the slow paced investigation into the explosion at the Avonmouth plant, which killed four workers, including a 16-year-old apprentice, the Cable has heard.

The investigation into the explosion, at the Wessex Water recycling plant in Avonmouth in December 2020, is being led by the police, with the support of the Health and Safety Executive (HSE). Findings are yet to be released from the inquiry into the incident, in which a silo catastrophically exploded. Wessex Water is also conducting an internal investigation into the incident, which is not expected to be released publicly.

Sixteen-year-old apprentice Luke Wheaton, 64-year-old Michael James, 63-year-old Brian Vickery, and 57-year-old Raymond White all died in the blast.

Specialist multi-agency inquiries of this kind typically take many months, if not longer, to complete. Some staff are, however, frustrated at the pace and rigour of the investigation into the deaths of their colleagues.

While the HSE has conducted in-depth interviews with some Wessex Water employees, the agency is yet to take samples for inspection from the silo that exploded, an insider has alleged. An HSE spokesperson told the Cable it would be inappropriate to comment on the investigation at this time. 

Following the Avonmouth blast, there was speculation into what the workmen and apprentice were doing on the roof of the silo, which contained biosolids – recycled organic matter, such as animal or food waste, to be used by farmers as agricultural fertiliser.

The Cable has now learned that the workers who were killed were using disk grinders on the silo, according to two sources with knowledge of the investigation. 

Sparks from the work may have ignited an accumulation of methane gas in the top of the tank, according to independent fire safety specialist Tony Ennis. 

Meanwhile, staff have also alleged that an ignition risk assessment was not carried out before grinding work began on that fateful day. This, however, remains unconfirmed, as Wessex Water declined to comment while inquiries continue.

An industry specialist with working knowledge of the Wessex Water plant told the Cable that the Wessex Water silo did not have a flame arrester – a device that stops sparks from entering a tank – leaving it more susceptible to an explosion, should a spark interact with air and gas inside the container. And while the silo was not meant to produce any biogas, because it was a holding tank for processed biosolids, residual gas emissions in storage could accumulate, according to the specialist.

It is not uncommon across the waste treatment industry for silos and Anaerobic Digesters (ADs) – systems that can break down a range of organic matter in the absence of oxygen to produce biosolids and biomethane – to be built without flame arresters, including the ADs at Wessex Water. This is in part because arresters require regular maintenance to keep them clean and functioning. But without them, staff and site safety can be undermined, the industry insider told the Cable, on the condition of anonymity.

“Every waste treatment plant in the country needs to look at Wessex Water”, the industry specialist stressed, adding: “They are all running off the same technology. The same people have designed them.”

A Wessex Water spokesperson declined to comment while investigations were ongoing and said: “We are continuing to work with the authorities as they carry out their investigations and are committed to understanding why the incident happened.”

An HSE spokesperson said: “HSE continue to support Avon and Somerset Police, who are leading this investigation. It wouldn’t be appropriate for us to comment at this time.”