The heavy rain over the past few weeks has meant that raw sewage has been discharged into the Thames. It’s been noticeable lying around on the surface of the water at Strand on the Green.
The discharges are ‘unacceptable’ say Thames Water, whose responsibility this is, but also inevitable until the Tideway Tunnel is complete, and work has been delayed, like everything else, by the pandemic.
Untreated sewage has been dumped in the Thames throughout London’s history. The sewer system is relatively new in the grand scheme of things, but desperately needs modernising. The majority of London’s sewer system is over two hundred years old and was designed for a much smaller population in a city which had many more green spaces which helped to absorb rainfall.
The combined network takes both the discharge from buildings – kitchens, bathrooms and toilets – and run-off from roadsides. When the sewer network and/or treatment sites get full up, the system has built-in overflow points, a bit like a sink or bathtub, to relieve the pressure and stop the excess wastewater backing up into homes and other properties.
When the system is full, it naturally spills into the river via these overflow points, like a regular sink would overflow if you left the tap running. It’s not a case of somebody pressing a button, it happens automatically to prevent flooding to property and the wider environment, where it wouldn’t be diluted in the same way it is in the river.
Most local discharges come from either Mogden Water Treatment Works, in Hounslow, and Hammersmith Pumping Station. Storm overflow tanks at Mogden are currently in use, as the site has reached capacity due to several spells of heavy rain in recent weeks.
Thames Water told The Chiswick Calendar the wastewater is heavily diluted as it is mixed with a large volume of rainwater that has led to the system filling up and the overflows being needed in the first place. They say discharges of untreated sewage into the Thames are “unacceptable”, even when they are legally permitted, and are working to stop them being a necessity.
But with the delay of the new Tideway Tunnel due to Covid, these sewage discharges into the river won’t be going away anytime soon.
Images above: a seal visits a paddle-boarder on the Thames; Theo Thomas collects a water sample from the river
Campaign for an online notification system
Theo Thomas is the Chief Executive of the London Waterkeeper charity, which is a member of the Waterkeeper Alliance, a global federation fighting for fishable, drinkable and swimmable water.
His charity is campaigning to get an online notification system for London’s sewage overflow points, so rowers, paddleboarders, canoeists and anyone else who uses the river can find out before they leave the house whether there’s been a recent discharge, rather than once they’re standing, or sitting in it.
Improvements in recent years
There has been major investment in the quality of the water in recent years. The appearance of seals in our part of the river is an indication that there is a plentiful fish stock and that in turn shows a marked improvement in water quality.
“There have been some big investments in upgrading the sewage works, particularly on the tidal sections and at Mogden upstream of Chiswick and then you’ve got to go all the way out to east London to Crossness and Beckton” Theo told The Chiswick Calendar.
“Each of those has had a sewage upgrade and that’s been great as we have seen the water quality improve in the last five or so years since those sites were given extra capacity and treatment was improved. That’s why we are seeing people take pictures of seals in sections of the river around Chiswick and Kew. They wouldn’t be there if there were no fish, and they weren’t there before those upgrades.
“Back in 2011 and before then in 2004 there were some significant fish kills in each of those summers. Because in the summer there’s less water in the river so it holds less oxygen. If you get a heavy downpour of rain and the sewers overflow in those circumstances then you’ll potentially see things like a fish kill.”
A reduced level of oxygen in the water is the most common cause of a localised die-off of fish. Water quality can actually be pretty good in the central Thames, but this isn’t the case around other parts of London and the UK where there haven’t been upgrades, says Theo.
As the water quality has improved more people have been going out on the Thames, rowing, kayaking, paddle-boarding and swimming. Experienced river users are well aware that when it rains heavily the water quality can change quite dramatically. The most hardened river users don’t seem too bothered, but Paul Hyman, who runs Active 360, the paddleboarding outfit at Kew Bridge, told us they cancelled beginners classes when it’s like that, to avoid the risk of people coming into contact with untreated sewage.
Experienced river user or not, it’s not pleasant.
Images above: sewage in the Thames at Strand on the Green
Keeping a watch on river pollution
Theo’s campaign for an online notification system isn’t just about getting the information about sewage releases in good time, it’s also about keeping a check on those responsible for water quality.
“We need to know that these upgrades are still doing their jobs. If we aren’t told when the sewers are overflowing we don’t know whether things are improving year-on-year. What we really don’t want to see is around £600,000,000 spent on these upgrades across five treatment plants steadily being undone over time.
When sewage is dumped into the Thames, Mogden Sewage Treatment Works and Hammersmith Pumping Station send out notifications a emails and Twitter. But many others, such as the overflow system at Kew, do not send out notifications when there are river dumps, giving an incomplete picture of what is actually going into the river.
“If they’re doing it for Mogden and Hammersmith, then they should be doing it for all of them” Theo continued. “We live in a world of the internet, big data improving our lives, in this case the environment, the more information we have then the more complete picture there will be.
“What we want is the system Seattle has which is a map online which shows lots of dots of the combined sewer overflows and they’re either green for not having overflowed in the last 48 hours, yellow for they have overflowed in the last 48 hours and red if they’re currently overflowing and that is updated every 20 minutes so that’s a real-time system.
“If you ask most people whether the Thames is clean or dirty, they’ll say its dirty and that’s been people’s response for decades and decades. Back in the 1950s and 1960s it was really sick as a river, but it has been gradually improving and these upgrades have seen it improve more.
“So the reality is it is getting cleaner but it will take time for people’s behaviour and mindsets to change because for decades it just hasn’t been the case. Having that information online so people can know when it is clean and when it’s not will really help improve that and so many more people could benefit from it especially in these times where people aren’t travelling as much and appreciating their local environment more.”
Image above: planned route of the Thames Tideway Tunnel
Thames Tideway Tunnel
One of the ways Thames Water is looking to ensure that current and future demands on London’s water and sewage networks can be met is by building the Thames Tideway Tunnel, also known as the ‘Super Sewer’.
The Tideway Tunnel is a 15-mile-long sewer, the width of three London buses, which is being dug under the River Thames. This new tunnel will pipe sewage from Acton to Thames Water’s Beckton works (just outside Dagenham) where the sewage will be treated and clean water returned to the environment.
“An online sewer notifications system is important for the Tideway Tunnel as well” said Theo.
“Obviously we want to see less sewage going into the Thames and that’s what we’re paying £4 billion for, but what we need to know is how well is it performing?”
Image above: one of the boring machines which is helping to dig the massive Tideway Tunnel, a worker walks through part of the finished tunnel
Tideway Tunnel delayed until 2025
Like many other things, the Covid-19 pandemic has had an impact on the Tideway Tunnel’s cost and schedule. In August 2020 it was announced that the cost of the project had risen by £233m (with a total cost of around £4.1 billion). A further nine months has been added to the schedule, as completion has been pushed back to the first half 2025.
Andy Mitchell, Tideway’s CEO, said: “Having to manage the progress of works during the pandemic has been a challenge beyond anyone’s expectations. Keeping our staff well both physically and mentally has been our first priority and secondly ensuring we continue with our task of cleaning up London’s river.
“We have achieved some major milestones so far this year, (2020) with the completion of the main tunnel drive in the western section and the central section drive due to complete before the end of this month. (November 2020) We have also continued to use the river to deliver the project, reducing our presence on London’s roads and helping with our overall ambition of minimising our disruption to the local communities in which we work.”
If you’d like more information on the work of London Waterkeeper you can follow the link below:
Read more stories on The Chiswick Calendar
See also: Severe weather warning
See also: The invasion of Chiswick Eyot
Support The Chiswick Calendar
The Chiswick Calendar CIC is a community resource. Please support us by buying us the equivalent of a monthly cup of coffee (or more, if you insist). Click here to support us.
We publish a weekly newsletter and update the website with local news and information daily. We are editorially independent.
To subscribe to the weekly newsletter, go here.