A multi-million pound programme to improve Bolton's sewer network has been announced to help it withstand heavy rainfall to reduce 'storm spills' leading to river pollution.

United Utilities has announced a £230M investment across the North West.

A total of £57M will be spent in Bolton to build additional storage capacity at the borough's wastewater treatment works and also at seven different locations within the sewer network across the borough.

The works will reduce the need for storm spills and will also improve 21km of the River Croal.

There will be £14m spent at the Horwich wastewater treatment works and nearby sewer network.


Bolton Wastwater Treatment Works. Picture Google Maps

Bolton Wastwater Treatment Works. Picture Google Maps


Storm overflows are designed to act as relief valves when the sewerage system is at risk of being overwhelmed, for example during heavy downpours when a lot of rainwater runs into drains and the sewerage system in a short space of time, according to watchdog Ofwat.

If the system does get overwhelmed it can cause flooding.

To prevent that happening water companies sometimes use storm overflows to release extra rainwater and wastewater into rivers or seas.

According to the government's environment agency, there is too much pollution, including from sewage pollution, from storm overflow discharges.

Water companies have come under intense pressure, including from the public, for allowing far too many sewage spills into rivers and coastal waters.

Cash - £4M- will also be invested in Worsley wastewater treatment works to upgrade it with more with more storage capacity so that additional sewage flows can be treated during heavy rainfall. This will improve 7km of Astley Brook.

The investment was announced today as United Utilities  retains the top 4-star rating for its environmental performance in 2021.

Jo Harrison, Director of Environmental Planning and Innovation at United Utilities, said: “At United Utilities, our purpose is very clear – we don’t just supply water, we also want to make the North West greener, healthier and stronger. We work very hard to maintain a high level of environmental performance and we’re pleased that for the second year running we have been awarded the top 4-star rating by the Environment Agency.

“We know there is always more to do, and playing our part to improve the health of the region’s rivers is very important to our customers. This is already well underway and, by 2025, we will have invested £230m improving 184km of waterways and we will have developed our plans to progressively reduce the impact of storm overflows in the coming years.”