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£5m underground tank to reduce spills from storm overflow in Birkenhead by 90%

18 Sep 2026

A £5 million project in Birkenhead that will reduce spills from a storm overflow into the River Mersey by around 90% has reached the halfway stage, United Utilities has announced.

The Mayfield pumping station combined sewer overflow (CSO) has historically activated around 100 times a year during periods of high rainfall. However, significant investment by the North West water company is expected to reduce this to fewer than 10 spills a year.

United Utilities is constructing a 500m³ underground stormwater storage tank on council-owned land off Mayfield Drive, near the junction with Ferry Road. The additional storage capacity will help the sewer network cope better during heavy rainfall, reducing the need for the overflow to operate when the system reaches capacity.

A new wastewater sewer screen is set to be delivered to site and installed in the next few weeks as work continues.

On completion, scheduled to be around March 2027, the land surrounding the tank will also benefit from a new community orchard for residents to enjoy.

 

Steve Kenyon, County Business Lead for Wastewater in Merseyside, said: “This investment will build resilience into the system, ensuring our network can better cope with heavy rainfall while improving water quality in the River Mersey.

“The storage tank and pumping station upgrades at Mayfield are part of a wider programme of work we're delivering across Wirral and Merseyside to modernise wastewater infrastructure and reduce the use of storm overflows.

“We are investing more than £375m over the next four years to reduce operations from 20 storm overflows across the Liverpool City region, with £60m being spent in Wirral alone.”

The company is making major progress on the largest upgrade of water and wastewater infrastructure in the North West in a century, investing more than £13.5 billion to protect and enhance over 500km of rivers, lakes and bathing waters, while safeguarding drinking water supplies for millions of customers.