SOME streets in Wrexham were left covered in what is thought to be raw sewage after Sunday's heavy downpours. 

The Wrexham Litter Pickers group took to social media to report that East Avenue and Holyrood Crescent had been left covered in "wipes, sanitary products and human excrement" last night. 

It followed heavy downpours in the Wrexham area on Sunday night, which saw The Racecourse stadium evacuated due to a collapsed roof.

Welsh Water's website states: "Most of the UK has a combined sewerage system, meaning that both rainwater and wastewater (from toilets, bathrooms and kitchens) are carried in the same pipes to a sewage treatment works.

"When our sewer system is operating normally, combined sewers collect rain water that runs off gutters, drains and roads, as well as sewage. We call this wastewater, which then gets taken to our wastewater treatment works, where it is cleaned, treated and returned safely to the environment to rivers or the sea. 

"Most of the wastewater network was built over 100 years ago during the Victorian times, if we were designing a system now, we would do it very differently and have separate pipes for sewerage and rainwater. This is how new housing developments are designed.

"During heavy rain storms, more water enters the pipes of these older ‘combined’ systems than they are designed to cope with, so they have been designed to safely relieve the pressure through release points - known as Combined Storm Overflows or CSOs. CSO release the flows – which is around 95 per cent surface water - into river of the sea. Without these release points, the sewerage system would back up, and cause sewage flooding to streets, highways and cause toilets to overflow inside properties."

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It adds: "It is important to point out that CSOs are designed to operate during heavy rain, so that if they release wastewater then any sewage present is heavily diluted with rain and surface water into waterbodies which should also be in flood.

"The operation of our CSOs is highly regulated and is permitted and monitored by our environmental regulators Natural Resources Wales and Environment Agency. CSOs have always existed on the sewer network and are not a new creation. It is possible that they are releasing more due to increased storm frequency linked to climate change, as well as increased amounts of impermeable surfaces like paving or concrete. These surfaces means more water runs off into the drains than on to an absorbent surface such as grass."

Natural Resources Wales and Wrexham County Borough Council have been approached for comment on the matter.