We know customers want us to clean up storm overflows, and we’re working our way through. By 2030, we aim to have tackled each one and reduced spills per overflow to a maximum of 10 per year.
The overflows near Beals Mill near Launceston, Cornwall will now spill much less thanks to improvements we’ve put in place. Our work isn’t finished yet, so spills should reduce even further.
What are storm overflows?
If there’s more waste in the system than sewage treatment works can cope with, the excess is released from a storm overflow. Most of the time, this is because heavy rain has added lots of extra water to the sewer.
If storm overflows weren’t on the network, the waste would back up and spill in other places. To make storm overflows operate less, we need to keep surplus water out of the system, increase stormwater storage or upgrade capacity at treatment works or pumping stations – very often, a combination of solutions is needed.
We share the sense of urgency customers have about storm overflows. Solutions take time to design and implement, but we’re making good progress.
What was happening at Beals Mill?
Beals Mill Wastewater Treatment Works had three local storm overflows. One of them was one of the region’s biggest spillers in 2023. Between them, the storm overflows spilled 450 times in that year. Our programme to address storm overflow use is focusing on major spill sites like this first, to have the biggest impact.
When we investigated the factors that were making the storm overflows spill, we found that groundwater (rainwater that’s seeped into the ground) was finding its way into the sewers. This means that after heavy rainfall, the treatment works were inundated with a lot of water that didn’t need full sewage treatment at all.
Actions that will reduce storm overflow use
After working out the reasons that led to storm overflow use, we made improvements to reduce spills. These have reduced spills by 40% (2024 compared to 2023).
Here’s what we’ve done so far:
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- Closing two of the three overflows, and diverting their flows to the treatment works.
- Adding a 40,000 litre storm tank so that excess wastewater can be stored at times of heavy flow, then treated when the flow slows down.
- Installing a new screening plant at the sewage treatment works, helping to reduce impact on water quality if the storm overflow does need to spill.
Further improvements that will be put in place soon
We’re planning to re-line sewers near the works to keep groundwater out. We can do this using a clever pipe-lining method that saves us from having to dig up the ground, reducing disruption for local people.
We’re also going to upgrade a local pumping station, which helps to move wastewater around the system. Boosting this station will help to ensure waste can get to the treatment works, even when the flow is heavy.
A path to improved water quality
We’re committed to helping to improve water quality in rivers and seas around the South West. For every storm overflow, detailed studies need to be carried out to make sure the measures we put in place will really work. Some sites also limit our options – for example, it’s not always easy to find somewhere to install a storm tank.
Our team members are working hard to deliver these improvements. Karl Stone, South West Water’s Area Operations Manager for East Cornwall, said:
“It’s rewarding to see real improvements taking shape. At Beals Mill, the upgrades we’ve delivered, including new infrastructure and a better understanding of how groundwater was affecting the site, have already led to a dramatic drop in spills.
Our teams live and work in these areas, so we’re personally invested in getting it right. There’s more to do, but we’re committed to keeping up the momentum and making a lasting difference.”
What’s happening in your area?
If you’d like to see whether there are storm overflows near you, what their spill history is and how we plan to make improvements, check out our WaterFit Live map. You can see near-live information about storm overflows. Follow the ‘more information’ links that pop up on the map to find localised information.