A major milestone has been hit on a project to improve water quality in the River Irwell. 

Water company United Utilities says work has been ‘continuing at pace’ on a £110m scheme at Bolton Wastewater Treatment works.

Now, a tunnelling machine has been brought to the site to complete a 150-metre (492ft) dig.

United Utilities says the tunnel will form part of a pipework system, replacing the old outfall – where a sewer empties directly into public waterways.

Local school children from the nearby St Saviour CE Primary School were on hand to see the tunnelling machine, named Harriet, as she arrived on site. 

Pupils from the school have their designs displayed on hoarding around the site after a competition to design a poster of what not to flush down the loo. 

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It’s part of several changes to the site, which is located off Red Rock Lane.

To meet growing demand from the Bolton area, water company United Utilities says it will be increasing the capacity of the works to allow it to treat 20 per cent more wastewater. 

Work began in February this year.

The increase in treatment capacity will also reduce the number of times the storm overflow operates in periods of heavy rain.

There will be major enhancements to the treatment processes at the works to use more innovative technology to treat the wastewater to a higher standard. 

The storm overflow outfall pipe will also be relocated as part of the project.

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Catherine Coupe, third party coordinator for United Utilities, said: “It was fantastic to welcome pupils from St Saviour CE Primary School to mark this major milestone for the project so they could get a better understanding of what we’re doing in the area. 

“They were really interested to see the tunnelling machine and asked lots of questions. 

“The works are continuing at pace across the treatment works at the moment and this project will deliver real benefits to the water quality in the River Irwell.”

The full improvements will be operational by April 2025, with landscaping completed by the end of that year.

When originally announced, the cost for the works were slated to be just £57 million.

However, the works will now include major enhancements to the treatment processes at the works to use more innovative technology to treat the wastewater to a higher standard.

This means the final effluent will be of higher quality, with reduced levels of chemicals including phosphorous and improved biochemical oxygen demand (BOD) – the amount of oxygen consumed by bacteria and microorganisms while they decompose.

Further projects are taking place at Bury and Rossendale wastewater treatment works.

Together with the works at Bolton, it’s expected the result will be improved water quality along a 47km (29 mile) stretch of the River Irwell.

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