5,000 fish died when ‘lime in a liquid form’ entered a river
Hundreds of fish were found dead in the White River at Pentewan in June 2025 following a pollution incident(Image: James Mustoe)
Residents living next to a river where more than 5,000 fish died during a “shocking and catastrophic” pollution incident are still waiting for answers one year on.
Thousands of Eels, trout, and brook lamprey were among the fish found dead in the White River in Pentewan Valley on June 19 last year when “lime in a liquid form” entered the water.
At the time, South West Water blamed the incident on a third-party delivery of liquid lime to one of its plants.
The pollution incident was reported to the Environment Agency, and a no-bathing health warning was issued to swimmers.
At the time, the EA said: “Bathing is not advised, due to pollution from sewage. Incident started June 19th 2025, 17.45. Incident is currently expected to end on June 20, 2025.”
The White River flows into Pentewan, a privately-owned sandy beach resort in St Austell Bay, close to a campsite. It had received a bathing water quality classification of ‘Excellent’ for the last four years running, from 2021 through to 2024.
Nick Taylor from local group Three Bays Wildlife remembers the incident.
Hundreds of fish were found dead in the White River at Pentewan in June 2025 following a pollution incident(Image: James Mustoe)
He said: “By chance, we undertook routine monitoring of the two sites above, the day after the lime incident occurred last year. It had an instant, catastrophic impact on the river life, essentially killing virtually all creatures in the stretch of river from the sewage works to the sea. On that day, we noted 103 dead fish in our monitoring site (over 30m), and we found very few live invertebrates in our sample.
“Lime is highly alkaline and would most probably have killed the fish and invertebrates by ‘burning’ sensitive parts of their bodies, particularly the gill structures, which enable them to breathe. They were essentially suffocated.
“I estimate that at least 5,000 fish were killed and countless invertebrates.”
Lime is commonly used in water treatment processes; it can also be a water pollutant under certain circumstances. Specifically, improper use or disposal of lime can lead to increased turbidity, elevated pH levels, and the potential for toxic substances to leach into waterways.
One year on, and Pentewan’s Cornwall Councillor James Mustoe said the local community is still waiting for real answers.
He said: “One year on from the shocking and catastrophic wave of pollution that swept through Pentewan Valley, I wanted to place on record that the local community, which was upset and devastated by the scenes we witnessed, have not forgotten, and are still waiting for the outcome of the investigation the Environment Agency has been conducting since that day.
“Water pollution cases often take years to conclude, but this one, while absolutely devastating, and described by the Environment Agency at the time as ‘high category’, was confined to one spill, in one geographic location, over a relatively short period of time, so could in theory take less time to investigate.
The Environment Agency has been investigating after pollution killed “many hundreds” of fish in the White River near St Austell(Image: Environment Agency)
“Last year I was clear in stating that if there is a fine as a result of the legal action, I want to see it invested straight back into the local area, to support things such as the valuable community work carried out by the White River Project group, to improve wildlife habitats and accessibility to the White River.
“Locally, we will continue to do all we can to ensure this terrible incident is not forgotten about, and that those who were responsible, both in enabling the pollution and actually causing it, are held accountable at the highest level.”
Three Bays Wildlife have recorded hundreds of sewage pollution incidents by South West Water at Pentewan over the last fives years.
In 2021, there were 146 spills totalling 2,797 hours, which equates to 3 months and 25.2 days. In 2023, there were 148 spills lasting 2,167.21 hours (two months and 29.5 days) and last year, sewage pollution incidents totalled 106 or 1,890.7 hours (that’s equivalent to two months and 18 days).
Nick Taylor added: “The raw sewage spills, from Menagwins Waste Water Treatment Works have already changed the type of aquatic invertebrates we see downstream of it.
“Pollution sensitive creatures, such as the larvae of flat-bodied mayfly and stoneflies, disappear completely and we find a proliferation of pollution tolerant species, such as freshwater shrimps, olives (a type of mayfly larva), leeches and hoglice.
“The river runs into St Austell Bay at Pentewan beach. Large beds of seagrass and maerl have been found within the bay. It is not known what effect the sewage pollution is having on these beds, but circumstantial evidence from limited snorkelling studies indicates it may well be encouraging the growth of smothering algae, limiting their ability to respire and photosynthesise.”
About the sewage pollution incidents, he added: “These figures lie well outside that expected for the works, in accordance with its Permit to Discharge. It has been accepted by SWW and the EA, that the high number of raw sewage spills are a result of too much rainwater and groundwater entering the sewage system, particularly over the winter period, after heavy rainfall. This increases the total flow entering the works to a level that exceeds its design capacity. To prevent the works from being flooded, the excess flow is passed directly to the river.”
“The sewage entering the river is diluted by the rainfall and groundwater, but the excessive length of time of the spills, leads to a significant build-up of sewage fungus on the bed and sides of the river. This appears as a grey filamentous coating, which even covers the gills of some of the invertebrates, limiting their ability to breathe.”
Cllr Mustoe added: “These figures speak for themselves, with sewage being discharged for the equivalent of two months into the river in the past year. The reality on the ground is stark.
“Just last week in a beach clean with the Marine Conservation Society, where we studied in detail a 100m transect of the beach at random, six per cent of the items we recovered were sewage related.
“This cannot go on, and it is critical that South West Water demonstrate clearly how their investment into both their treatment plant and wider sewage infrastructure locally is happening. I have recently written to South West Water and asked them to meet with us to address these issues specifically. I await their response.”
A spokesperson for the SWW said: “This incident remains subject to an ongoing Environment Agency investigation and legal process, so we are unable to comment further at this stage. We continue to cooperate fully with the regulator.”
A spokesperson for the EA added: “We have been conducting a full and thorough investigation into this serious pollution incident, and this work is nearing completion.
“So as not to prejudice any legal proceedings, we cannot comment further at this time, but we will provide a statement once our investigation has concluded.”
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