Storm overflows, pollution incidents and bursts
There is much confusion around the types of pollution that result from water company activities. In simple terms these fall into two categories permitted and pollution incidents. This article setsout some of the key differences but the important thing to remember is that both result in sewage entering the river or sea.
Permitted
Permitted spills are usually from combined sewage sytems where foul water - wastewater from your home, business or industry - gets mixed with surface water - rainfall running off roads and roofs into the drains.
Foul water
Generally the amount of foul water can be fairly accurately predicted. We tend to produce a similar amount of wastewater each day although the rate will vary throughout the day more people washing and using the toilet before work on a morning for example. An additonal amount can be predicted and added to cover tourists and visitors as Exmouth is an attractive place to visit. This is based on the current population and the expected number of visitors. Put together this is used to calculate the dry weather flow.
Population estimate for for the Exmouth sewage treatment works catchment area 2024 - including Budleigh Salterton, Lympstone and outlying settlements (Source SWW EIR)
Resident Population 47,730
Including tourists at peak season 59,405
Surface water
Surface run off is much harder to estimate as it depends on the severity of the rain or snow, the surfaces it falls on which affects how quickly it enters the sewers and how wet the ground is already. There is evidence over time that climate change is affecting the amount and severity of rainfall particularly in the winter and spring. In summer the total amount is largely the same but there is evidence that rain storms are heavier.
In the second half of the last century more and more housing was built with separate sewer systems but the legacy in towns like Exmouth, as with much of western Europe, is a combined sewerage system where foula dn surface water is mixed together. At times of heavy rain the sewers fill up storm tanks as there is a limit around how much can be passed to the wastewater treatment works (wwtw) for treatment. If the storm tanks fill up then, providing the maximum flow is being pumped to the wwtw, the water company is 'permitted' to spill the sewage into the river or sea via a combined sewage overflow (CSO). If this did not happen the sewer would fill up and flood homes and businesses so it is a safety valve.
Over the last few years water companies have been required to fit Event Duration Monitors (EDMs) which send a message to the water company when a spill occurs. They are required to publish an annual report for each CSO saying how many times it spilled and for how long. From January 2025 water companies are also required to notify the public when any CSO starts to spill and stops spilling. This has to be done within an hour. This is also known as Near Real Time Reporting. This information is available on the National Storm Overflow Hub (NSOH) which is managed by Water UK who are the industry trade body.
ESCAPE'S View
We have a number of issues but recognise that the installation of EDMs has brought sewage pollution to the public's attention as we see in almost real-time how often storm overflows are used even after a very small amount of rainfall. Many permits were approved more than 20 years ago and have not kept up with population increase. East Devon has the second highest growth in the south west of England.
There is evidence that water companies have not invested in upgrading or maintaining their wastewater assets resulting in storm tanks silted up, broken pumps and pipework past its lifespan.
There is also growing evidence that many EDMs are failing and therfore under-reporting spills. Ofwat has been tasked with monitoring the reporting of spills within an hour but it is unclear how the 'Financial Regulator' will be able to monitor this effectively. We have recently seen a delay of two and a half hours between and CSO start spilling and it appearing on WaterFit Live.
The final concern is that Water UK may not fall under the Freedom of Information regulations and so will not be accountable to the public who have a right to request environmental information from water companies.
Pollution Incidents
The other main reason that untreated sewage enters the water is because something has gone wrong. This could be down to a large number of reasons such as a power failure, blockage in the sewer or a burst pipe as we experienced in Exmouth a number of times in 2024. There are also other less obvious reasons such as misconnections where a foul water drain is connected to a surface water sewer. The net result is the same as with permitted spills, untreated sewage enters the watercourse and presents a risk to the environment and people wanting to use the water.
Managing a pollution incident quickly is critical and water companies are monitored by the regulator the Environment Agency (EA). Water companies are expected to self report any incidents immediately to the EA but often it is the public who spot problems and spills and report them to the EA hotline on 0800 80 70 60.
ESCAPE'S View
The public play's a part in creating problems by disposing of fats and oils into the sewers and allowing misconnections through improvement works but the lack of investment in infrastructure and regular planned maintenance by water companies is undoubtably a major factor. Unfortunately South West Water (SWW) is by far the worst offender in England and Wales for the number of pollution incidents. As water companies are all different sizes the EA normalises the figures by calculating the number of incidents per 10,000 km of sewer. The national average in 2023 was 36 incidents per 10,000 km the figure for SWW was 110 incidents per 10,000 km (194 actual incidents). Pollution incidents are classified by their severity from 1 - 4 with 1 being the most severe eg an oil tanker going around. Category 4 incidents are small and not reported. Despite claims that SWW is reducing the number of pollution incidents a recent Environmental Information Request (EIR) shows there is no reduction in our area.
Pollution incidents in the Exe Catchment area
Cat 1 2 3
2018 0 0 21
2019 0 0 17
2020 0 0 26
2021 0 1 18
2022 0 0 14
2023 0 1 41
Article published Monday 9th December 2024