The first of five micro-tunnels 27 metres below Preston city centre is underway at Watery Lane. United Utilities is constructing eight kilometres of tunnels at a cost of £114m, to stop wastewater flowing into the River Ribble during heavy storms.
Eight deep shafts are being dug at Watery Lane, Marsh Lane and Fishergate Hill, to allow the micro-tunnels to be constructed.
Powerful hydraulic jacks are used to push specially designed pipes through the ground behind the Micro Tunnel Boring Machine (TBM). At the same time the rotating head cuts the rock and diverts the rock chippings to the back of the TBM where it is recovered via skips.
Eventually all five micro tunnels will connect to the huge 3.5 km long storm storage tunnel between the City and Penwortham. The scheme will bring significant environmental improvements to the Fylde coast bathing waters and designated shellfish beds located within the Ribble Estuary.
Brian Edwards, Principal Project Manager said:
"The project has been planned to help the river and the Fylde coast comply with European legislation.
"Once complete, improvements should be seen to river quality and shellfish waters along the estuary and to beaches at Southport, Ainsdale, St Annes and Blackpool."
The tunnel and shafts will provide an extra 40,500 cubic metres of storm water storage for the city. During a storm the new tunnel will transport flows to the new pumping station in Penwortham, this is designed to pass up to a maximum flow of 1500 litres per second (equivalent of 30 baths per second) to the existing Wastewater Treatment Works at Clifton Marsh.
Flows above this rate will be screened and allowed to flow to the river via the new outfall adjacent to the pumping station.
January saw delays to the multi-million tunnelling project in Preston, due to silt entering a small section of the tunnel under construction north of the river, near Clifton Marsh.
Mr Edwards added:
"We are disappointed that the tunnelling work close to Clifton Marsh has had to be temporarily halted. We are securing from our contractor a programme of works that will recommence tunnelling shortly."
When the groundbreaking project is finished the amount of storm water spilling into the River Ribble will be reduced.
With the UK government demanding a 50% reduction in storm overflow spills by 2029, the era of reactive management is over. Speaking in the House of Commons on 21 July 2025, then environment secretary Steve Reed said, “This Government will cut water companies’ sewage pollution in half by the end of the decade.”
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