Four workers were killed and another was seriously injured following an explosion and subsequent fire at the site on 02 June 2011.
HSE said both Valero Energy UK and B&A Contracts will face charges under Sections 2(1) and 3(1) of the Health and Safety at Work etc Act 1974. At the time of the incident, the refinery was operated by Chevron Limited, but ownership changed in August 2011.
-- Advertisement --
HSE's deputy director field operations, Jane Lassey, said: "Following a painstaking and extremely thorough investigation, much of which was conducted jointly with Dyfed Powys Police, we have concluded that there is sufficient evidence to bring criminal charges."
The defendants are due to appear at Haverfordwest Magistrates' Court at 2pm on 24 September 2018.
(LM/MH)
