For more than three hours an Anglian Water sewage treatment works discharged sewage into the River Wid in Essex killing hundreds of fish and hundreds of invertebrates, a court heard last Friday.

The incident in September 2009 affected more than 2 kilometres of the river and was categorised as the most serious by the Environment Agency. Harlow Magistrates’ Court has sent the case to Chelmsford Crown Court for sentence after hearing details of the offence at Wyatts Green Road, Doddinghurst.

Mrs Anne-Lise McDonald, prosecuting for the Environment Agency, told the court that Anglian Water records showed that there were power problems on site all weekend. There is a back-up generator on site for power failures.

Mrs McDonald said that on the night of the offence, there was a power failure at the site and the emergency generator failed to operate. The lack of power meant that the works discharged directly into the river.

An electrician sent to Doddinghurst STW called Anglian Water operations management centre at 9.25pm to ask why he had been sent there. He said he thought he had been sent to turn off the back-up generator but when he did, everything at the works stopped so he turned it back on again. He was told to leave the generator running, the court was told, but 10 minutes later it stopped working and he thought the fuel had run out.

Neither the electrician nor the operations staff knew where to get more fuel.  An employee dispatched to get more from Chelmsford works was diverted before he could get it back to Doddinghurst.

“The duty manager seemed unaware that Doddinghurst works had completely failed and was discharging sewage into the river,” said Mrs McDonald.

At 1.20am the electrician found and checked the main power supply for the works.  “The electrician turned the isolator off and on again and the power came back on", said Mrs McDonald.  It was not clear, she said, whether the power failure was due to the electrical supply to the works or to a fault on the main power supply within the works.

“But the main supply was not checked for two and a half hours because the electrician was unaware of its location and he said there was no schematic on site to enable him to find it”.

She told the court that after the incident Anglian Water could find no fault with the isolator. It was 3.20am the following day before there was confirmation that the tank was fuelled.

The site treatment manager told investigating officers that due to thefts of fuel at the site only a limited amount was kept there but he thought there was enough fuel to get more if needed. He said a ‘lessons learned’ document had been drawn up since.

In mitigation Miss Sarah Le Fevre said that there were procedures in place to deal with this type of incident but they were not followed. She said there was fuel in an external tank but that the pump supplying the internal tank had tripped and the electrician failed to check it. The electrician had also failed to check the isolator switch.

Sentencing will take place at Chelmsford Crown Court on 18 November. Anglian Water Services Ltd pleaded guilty to: