Last reviewed 20 August 2019

On 10 July 2019, Aylesbury Crown Court fined Thames Water £607,000 and ordered it to pay £100,000 in costs for polluting the Maidenhead Ditch in Berkshire.

The Facts

The Court heard that Thames Water operates a sewage treatment works near the Maidenhead Ditch, Berkshire, which flows into the River Cut, a tributary of the Thames. This is home to Bray Marina, a public supply waterworks and an well-used amenity for water sports enthusiasts.

In June 2014, a member of the public reported that they had witnessed a grey and odorous cloud of polluted water entering the Maidenhead Ditch and River Cut from the sewage treatment works. An estimated 30 million litres of untreated human waste and other pollutants were released into the watercourse which killed hundreds of fish. Environment Agency officers tested the water quality and took samples from the watercourse at various locations. The samples contained very low dissolved oxygen levels and indicated that oxygen had been stripped from the water as a consequence of pollution. A second, smaller, incident also occurred in August 2014. The court was told that sewage had ended up in the watercourse due to poorly performing equipment and a build-up of items such as wet wipes stuck in the system.

Following investigations, officers discovered that discharges of untreated or inadequately treated raw sewage had repeatedly flowed into the river. Log book entries suggested that the discharges were ongoing and that there were other serious problems, indicating the site was struggling to cope. Thames Water’s management failed to react to the alarms which had alerted them to these concerns.

The sewage works has a permit to discharge storm sewage into the watercourse in storm conditions. Its aim is to manage the high flows which can occur during periods of extreme rainfall. There had been no serious weather conditions in June 2014. The sewage works also have a permit to discharge final effluent into the watercourse as it includes human waste, various pollutants, organic materials and chemicals. The Environment Agency told the court that Thames Water did not meet the conditions of these permits around the time of the incident.

The Decision

Thames Water entered guilty pleas at the first hearing before Maidenhead Magistrates’ Court on 14 November 2018. It accepted that it had breached Regulation 38(2) of the Environmental Permitting (England & Wales) Regulations 2010 in allowing discharge from the storm sewage effluent to leach into the storm tank and that the discharge contained more than 50 milligrammes per litre of biochemical oxygen demand.

The Court ordered Thames Water to pay fines of £607,000, costs of £100,000 and a victim surcharge of £120.

Speaking after the case Colin Chiverton, Environment Manager for the Environment Agency in Berkshire, said:

“Our officers believe up to around 30 million litres of sewage polluted the ditch. Hundreds of fish died and the environment suffered as a result of Thames Water’s failures. Pollution could and should have been avoided had the many warnings and alerts leading up to the incident been acknowledged and dealt with properly.

We take these types of incidents very seriously and will do everything within our powers to safeguard the environment and people affected, and that includes holding those who put the environment at risk to account for their actions.”

In a statement, Thames Water said:

"Our current pollution levels are 46% lower than five years ago, when this regrettable incident happened.

We're really sorry for what happened at our works, which has a very good track record, following one of the wettest winters on record.

This led to higher than expected amounts of wet wipes and other unflushable items getting into the system and causing a blockage."


This case is another large fine for Thames Water for pollution offences, following a £20 million fine over incidents in Buckinghamshire and Oxfordshire in 2013 and 2014, and a £2 million fine regarding another discharge in Oxfordshire in 2015. Perhaps the most interesting feature of this case, however, is the source of the problem: wet wipes.

The issues over wet wipes and other unflushable items has recently caught the public’s attention. Giant “fatbergs”, made of wet wipes, congealed grease and cooking fat, have appeared across the country. Earlier this year, South West Water removed a 210ft (64m) long fatberg in Sidmouth, Devon, which took eight weeks and £130,000 to remove.

Despite a growing public backlash, the UK uses 11 billion wet wipes a year, according to reports. As a result, the UK Government has promised to ban household wet wipes as part of its wider strategy to reduce plastic. Until then, however, sewage treatment facilities ought to be mindful of their potential impact if stuck in the system. As a contributory factor to the blockage which caused the pollution in this case, it would have been far cheaper to address the problem than receiving a court fine.