The stark assessment was given by Pete Lambert, river projects manager at Shropshire Wildlife Trust, who said old infrastructure in Shrewsbury was having a “significant negative impact on the river”.
The trust is now calling for major investment from Severn Trent Water to move the town’s drainage system away from its heavy reliance on combined sewer overflows (CSOs).
CSOs carry both rainwater and domestic waste, but become overwhelmed in periods of heavy downpour which causes them to discharge their contents – including untreated human waste, non-biodegradable wipes and sanitary products, and cleaning chemicals – into the river.
Speaking at a Shrewsbury Town Council meeting on Monday evening, Mr Lambert said: “At normal rainfall those CSOs don’t activate and don’t discharge. The issue for Shrewsbury is that we have a colossal number of these CSOs – not all of them monitored, which is disconcerting – that discharge directly into the river as it passes through town.
“The tributaries that run into the Severn in the vicinity of the town, including the Rea Brook, Bow Brook and Rad Brook, are all affected by discharges of this nature.
“It isn’t just a main river issue, it’s an all river issue.”
According to data published by the Rivers Trust, the CSOs in Shrewsbury which are monitored discharged more than 1,000 times in 2019 for a total of more than 20,000 hours.
One in Castlefields discharged 177 times for 2,301 hours and one in Victoria Avenue 162 times for a total of 3,140 hours.
Mr Lambert said the result of such frequent and prolonged CSO discharges was that the town now had a “significant water quality problem”, causing harm to wildlife and putting the long-term health of the town at risk.
The trust has also backed a private members’ bill by Ludlow MP Philip Dunne, chair of the Environmental Audit Committee, aimed at cleaning up the country’s rivers. The bill is due to be discussed in the Commons on January 22.
Mr Lambert said: “We have written to all five MPs in Shropshire asking them to turn up on the 22nd and put their support behind the bill.
“The bill primarily raises the discharge standards of CSOs, so it’s an interim measure, but it’s an important step towards recognising the damage that is currently being done on a regular basis.
“Secondly it raises those standards to move towards greater investment from Severn Trent.”
Mr Lambert said Shrewsbury MP Daniel Kawczynski had already offered his support to the bill and pledged to vote for it.
The town council’s finance and general purposes committee resolved to support the trust’s efforts and write to Mr Kawczynski to seek assurance that he will support Mr Dunne’s bill.
The town council will also invite Severn Trent to a public meeting to discuss the issue and any proposed solutions.
A spokesman for Severn Trent said: "Our system’s designed to stop customers’ homes being flooded during times of heavy rain. It does this by redirecting the waste water, which is mainly rainwater, to a nearby water course to stop our sewers and treatment works becoming overwhelmed by the sheer quantity of rainwater.
"This is fully agreed with the Environment Agency, and by doing this we hope to make sure no one has to suffer sewer flowing in their home, which is a terrible experience for anyone."