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South West Water (SWW) is investigating the “high frequency” of leaks from two sewage treatment plants into a popular swimming river in south Devon.
Sewage discharges from storm overflows at the Diptford and Moreleigh plants have risen from 128 in 2021 to 207 in 2022, according to data from the Environment Agency.
The number of hours of dismissal rose from 450 in 2021 to 1,056 in 2022.
South West Water (SWW) said work at both sites should reduce levels of spills by the end of July.
A conservationist said he could not understand what was causing the increase in discharges.
The River Avon is a popular river for boaters and every year hundreds of swimmers take part in the Bantham Swoosh which swims from Aveton Gifford to the sea.
Storm surge discharges should operate during times of heavy rainfall to prevent flooding of homes and businesses.
Discharges into the River Avon at Diptford Sewage Treatment Plant have increased from 83 in 2021 to 119 in 2022, according to EA statistics.
Storm surge discharges at Moreleigh on Torr Brook, a major tributary of the Avon, rose from 45 in 2021 to 88 in 2022.
The Environment Agency’s records say SWW surveys in Moreleigh and Diptford were caused by “high spill frequency”.
The average number of leaks in the DHW network dropped from 38.9 to 28.5 from 2021 to 2022, “due to a combination of dry weather and our interventions and investments,” the water company said.
SWW said it has committed to achieving an average of 20 spills per storm overflow per year by 2025.
The company was fined more than £2.1 million in April after admitting to fouling five sewage treatment plants and pumping stations in Devon and Cornwall.
It said “improvements” at Diptford and Moreleigh should “reduce levels of spills from those sites” by the end of July.
A SWW spokesperson said: “We are reducing the use of storm surges and our plan is working, but there is more to do.
“We want everyone to have confidence in water quality and know that we are serious about reducing the use of storm overflows.
“We have installed 100% monitoring on our storm overflows ahead of the target.
“We are investing significantly to reduce our impact on rivers and we have plans to invest in a number of storm surges affecting the River Avon.”
The nearest designated bathing place, where the water is tested by the Environment Agency, is Bantham at the mouth of the river, where the quality was rated “excellent” in 2022.
‘Idyllic’
The River Avon, also known as the River Aune, has its source in the marshland on Dartmoor and flows through the South Devon Area Of Outstanding Natural Beauty (AONB) to the sea.
Dr. Stuart Watts, chairman of the river watchdog the Aune Conservation Association, told BBC News that on a fine day the lower reaches of the river are packed with people in boats and kayaks, stand-up paddleboards and swimming.
“It’s just idyllic, it’s wonderful,” he said.
“It’s the artery that feeds everything in the Avon Valley, which is central to the South Devon Area of Outstanding Natural Beauty and the diversity of that area depends in many ways on the river.”
He said the increase in layoffs was a mystery.
“From my own experience as a gardener, 2022 has been a terrible year for rainfall and yet here in Diptford and Moreleigh we have this huge increase in discharges.
“The excuse of heavy rainfall causing these discharges just isn’t there.
“We don’t understand why they occurred, but for a considerable period of time, sewage in some form was discharged into the river.
“We don’t know what those discharges were made of or how much they were diluted.
“They say they’re going to fix them, but we don’t know what went wrong and we don’t know what they’re doing, so we’d like to know more details.”
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