Wessex Water have sent us this statement about their plans for storm overflows. Note especially the section on rainwater separation:

I’m writing to you to explain more about what we’re doing to improve river and coastal water quality in the area, and our plans to address storm overflows. We know many of our customers are concerned about overflows, and we’re absolutely clear that they aren’t fit for the 21st century. Our long-term aim is eliminate the need for storm overflows. 
There are probably certain questions you’re frequently being asked about ‘sewage dumping’, or indeed may have questions yourself. I thought it would be helpful to outline what we’re doing about storm overflows, now and in the future, as part of our commitment to great river and coastal water quality in our region.

The facts

Wessex Water does not ‘dump’ sewage anywhere. Storm overflows operate automatically during or after intense rainfall to prevent flooding of properties and are licensed by the Environment Agency.
We would love to stop all storm overflow discharges immediately. But they are a legacy resulting from how houses and drains have been built for over 150 years – being drained by one pipe to carry both rainwater and sewage.
To tackle the issue, we’re spending £3 million every month on improving them and reducing how often they operate. We’re also planning to go even further and, if approved by our regulators, will invest around £9 million per month from 2025.
We feel it’s important people know where and how often storm overflows operate. You can view a map of all our overflows, see the primary cause of their operation and our progress in installing real-time monitoring on our Drainage and Wastewater Management Plan portal. You can also download the number and hours of overflow discharges and what we’re planning to do about them from the performance section.

What we’re doing now

Here are some examples of the different ways we are investing to reduce overflow impact and discharges.

Increasing treatment capacity
At treatment centres means we can deal with more rainwater after a heavy rainfall event. One location where we’ll be doing this is our largest water recycling centre in Avonmouth, near Bristol.

Increasing storage capacity
By installing large storm tanks we are able to store more rainwater and sewage prior to it being treated. An example of where we have carried out this work is at Compton Bassett in Wiltshire. 

Separating rainwater from sewage
This approach is the most environmentally friendly solution, and one area where we have done this is at Portland, in Dorset, which has seen surface water from 8,000m2 area removed from the combined system that also carries foul water.

Overflow treatment
In more rural locations, nature-based solutions can be used like reed beds to naturally treat storm water before it’s discharged into local watercourses. We have successfully achieved this at Shrewton, Wiltshire where groundwater at times inundates the sewer network.

Our Storm Overflow Improvement Map outlines where and how we’re tackling the issue near you.

What we all can do
The best solution is separating rainwater at source so it doesn’t enter sewers. We all need to value rain as a resource, capturing it locally for reuse (such as garden watering) and then disposing of it back into the environment as close to where it landed in the first place, for example, via rainwater gardens and/or soakaways.
You can read more about how you can help.

What next?
This email is intended as the first of our regular updates to you about our work to provide great river and coastal water quality.  If you would prefer not to receive this information please unsubscribe.

In the meantime, we’re happy to answer any questions you may have via email: overflows@wessexwater.co.uk
I hope you find this update useful.
Yours sincerely,
Matt Wheeldon
Director of Infrastructure Development
Wessex Water

We've launched our campaign for the River Char as follows:

1. River Water Campaign – to clean up our river…
We call on Wessex Water to:

• Take urgent action to stop all sewage discharges at Newlands Bridge (recently 8-12 per year)
• Work with Newlands Holiday Park and houses on Stonebarrow Lane to • seal any defective drains and • stop rainwater from roofs, roads and hard standing entering the sewer network.
• Install 6mm screens at Newlands Bridge – as a temporary measure.

We call on the Environment Agency to:

• Start monitoring water quality again at the mouth of the River Char.

2. Coastal Waters – to clean up our beach and sea…
We call on Wessex Water to:

• Cut discharges of untreated sewage into the sea to less than 10 per year and 3 per bathing season. [These happen about 70 times a year into the sea, with no pollution alert required.]

We call on the Environment Agency to:

• Enforce the requirement for no storm discharges at Newlands Bridge
• Extend its definition of ‘Bathing season’ beyond May-Sept and reclassify discharges from the Long Sea Outfall as “high priority”.

We call on South West Water to:

• Clean up its plastic biobeads, which are littering Charmouth Beach.

To help make this happen, we will film the plume of untreated sewage pouring from the offshore pipe and work with South West Water to implement its agreed beach clean-up strategy.

3. Other Sea and River Issues – we will also campaign on 3 issues:

• Climate-led Sea Level Rise: we will press for full information on Wessex Water’s strategy.
• Sewage Spills: we will work with Wessex Water to get complete, accurate, real-time data.
• Community Projects: we will seek funding to help residents use water butts and other water-saving techniques to reduce the amount of rainwater entering the combined sewer.

More details here