By rosebell
Microtunnelling will soon get underway on United Utilities’ £110M Bolton wastewater treatment works upgrade to improve water quality in the River Irwell.
Towards the end of September, micro-tunnel boring machine (TBM) Harriet arrived at the Bolton wastewater treatment works site off Red Rock Lane in Radcliffe.
United Utilities’ £110M project to improve the facility includes the excavation of a new 150m long tunnel. This will form part of a pipework system, replacing the old outfall.
Construction on the overall upgrade began in February of this year. The aim is to increase the capacity of the works to allow it to treat 20% more wastewater and to reduce the amount of times that the storm overflow operates in periods of heavy rain.
The tunnelling design and construction works are being carried out by Active Tunnelling, subcontracted by principal contractor Mott MacDonald Bentley, a Tier 1 framework partner of United Utilities.
The micro-TBM will be navigating geologically complex ground conditions.
A United Utilities spokesperson told GE that these “complexities include a deeply incised glacial valley, the Irwell Valley Fault and the legacy of former coal mining”.
“The alignment has been chosen to mitigate risks for tunnelling works associated with these conditions. The tunnel is being driven through river terrace gravel deposits,” they added.
The decision to use a microtunnelling, or pipejacking, technique was influenced by these local constraints.
Once the tunnelling phase is completed, the old outfall pipe will be removed, and a bifurcation system will be built to divert flows into the new pipe.
Full improvements are expected to be operational by April 2025, with landscaping work finishing by the end of that year.
This upgrade forms part of a wider set of improvements across the region, with similar works at Bury and Rossendale wastewater treatment works set to enhance water quality along a 47km stretch of the River Irwell.
