Thames Water storm overflows have collectively discharged sewage for more than 154 hours in the last two days, the company’s new interactive map shows.
As of Tuesday morning, 28 monitors had recorded a discharge as having stopped in the last 48 hours.
This figure does not include a further 21 monitors that were recorded as currently discharging, with some adding up to more than 850 hours of discharge since late December.
Two storm overflows in Berkshire, Burghfield and Mortimer have racked up 853 and 855 hours respectively since December 19, feeding into brooks that eventually flow into the Thames.
Another in Fairford, Gloucestershire, said it has been discharging for 770 hours since December 23.
Thames Water said the discharges are necessary to prevent sewage backing up into people’s homes and businesses when the system exceeds capacity.
Liberal Democrat councillor Geoff Mayes, who represents the Burghfield and Mortimer ward and who is a civil engineer by trade, said the overflow monitor at Mortimer is clocking so many hours because water is continually being recycled between the brook and the sewer system during floods and heavy rain.
He said: “Once the water gets into that system they can’t stop it. They haven’t got any reservoir in the system, not any large storage, but it does depend on the way the system is designed and operated.
“There are pipes and manholes in the road nearby which, in certain circumstances, if it’s overloaded with surface water from the rain, the manhole covers lift and the water from the brook gets into the valve system.”
He also said that flap valves, designed to stop water flowing back into the sewer system, are getting jammed open because of a build-up of mud and sediment.
A spokesperson from Thames Water said the company has a £17 million upgrade planned for Burghfield which it says will reduce untreated sewage discharges and that it is investigating the best way to reduce discharges from Mortimer.
They added: “Our shareholders have recently approved a business plan that sees us spending an additional £2 billion beyond what our customers are funding so we can improve outcomes for customers, leakage and river health and we’ve also committed to a 50% reduction in the total annual duration of spills across London and the Thames Valley by 2030, and within that an 80% reduction in sensitive catchments.”
Dr Harvey Wood, director of the Clean Rivers Trust, said there needs to be a nationwide overhaul of sewage infrastructure because it is not able to deal with the amount of water being flushed away by an increasing number of households.
He said: “It’s a huge problem that this country has got to adjust to. Sewers that are discharging are having to take far more sewage as the house building continues and the system can’t cope.
“There’s a huge need in rural and semi-rural areas for an increase in sewer size. The sewer system generally in this country is shot.
“And there needs to be a national debate between the Government, the water companies and the other players, from the angler to the idler.
“The person who wants to sit by a river and write poetry has equal rights and everyone has got to be aware that it’s a major upheaval this country is going to have to undertake.”
An Angling Trust spokesperson added: “The interactive sewage map published by Thames Water shines a welcome light on what is happening to our rivers. But it is only the first step.
“What is needed now is action to address the appalling lack of investment in our sewage and wastewater infrastructure since water companies were privatised in 1991.
“That lack of investment and water companies prioritising profits over protecting our environment is nothing short of scandalous. It is a failure of the business model, but also a political failure and a regulatory failure.
“Elevated levels of sewage in our rivers is devastating for our fish and wildlife, as well as a threat to our public health.
“Sudden massive pollution spills from either sewage or farming can wipe out whole stretches of river, killing hundreds, sometimes thousands of fish. That river can take years to properly recover.”