The company's main activity involved injecting natural gas into depleted underground oil reservoirs for storage. On 26 February 2014, during a maintenance operation, around 145 kg of natural gas was released into the atmosphere, along with some crude oil that spilled on to the concrete process area.
The two employees who were carrying out the maintenance work were unharmed, however they were exposed to a risk of fire and explosion as the release formed a flammable gas cloud.
The Health and Safety Executive's investigation found the workers to be inadequately trained and supervised and they did not follow the permit to work and isolation procedures.
Humbly Grove Energy pleaded guilty to breaching Section 2(1) of the Health and Safety at Work Act at Winchester Crown Court. It was fined £80,000 plus costs of £14,000.