The Court of Appeal has dismissed an appeal by Thames Water against a £250,000 fine for polluting Chase Brook near Newbury in Berkshire with raw sewage in 2012 resulting from a leak at its Broadlayings Sewage Pumping Station.

At  the Appeal Court hearing in London Mr Justice Mitting, sitting with Lord Chief Justice Lord Thomas and Mr Justice Lewis, described the fine as lenient, saying it could easily have been higher.

Thames Water had appealed for the fine to be reduced – the water company’s lawyers sought to introduce new evidence and argued the judge at the original hearing had got some of the facts wrong.

Original case took £346.7m profit by Thames into account

At the time Rooma Horeesorun, the prosecutor for the Environment Agency who brought the case said:

“The offence was sentenced following the New Environmental Offences Sentencing Guideline. In addition to the culpability and harm factors the Judge took into account the financial circumstances of the defendant."

“The defendant’s profit for the year ending 31 March 2014 was £346.7 million. The message is clear and the level of fines ordered reflects proportionately with the financial circumstances of the defendant”.

Thames Water received the fine in August last year after admitting breaches of environmental protection regulations.

The leak at the Broadlayings Sewage Pumping Station was caused by two clogged up pumps – despite over a dozen alarms warning of rising sewage levels  Thames Water staff did not respond. One or both of the pumps had failed on at least 16 occasions five months before sewage overflowed into the brook over a period of a week.

Mr Justice Mitting said that Thames Water had been convicted of 162 environmental offences since 1991 and that without mitigation, the starting point for calculating the fine would have been “significantly into seven figures”, concluding:

“We would have had no hesitation in upholding a very substantially higher fine. This appeal is dismissed”.

Earlier this year in a case brought by the Environment Agency, Thames Water was fined £220,000 and ordered to pay costs of £27,500 at Guildford Crown Court on 16 February for polluting the River Blackwater, a tributary of the River Loddon in Surrey. In that case the judge concluded that the company had been reckless in relation to the incident which had caused significant environmental harm and negligent in allowing a blockage to occur at its Camberley Sewage Treatment Works.

In 2010 the Court of Appeal reduced a fine imposed on Thames Water for spilling sodium hypochlorite into the River Wandle in September 2007 during cleaning at Beddington sewage plant which killed 7,000 fish. Three Court of Appeal judges ruled that the £125,000 fine imposed in January 2009 at Croydon Crown Court was "manifestly excessive" and reduced it to £50,000.