A giant robotic mole that has been crunching its way under Preston for a year has resurfaced in the city centre.
United Utilities (UU) lowered the machine 28 metres into a shaft close to Penwortham Golf Club and it has been steadily burrowing 3.5km underground to Marsh Lane.
The mole has ground out the water company’s centrepiece main tunnel, into which other tributaries that have already been created will feed.
Carl Sanders, UU senior project manager, said: “This tunnel is very much the lynch-pin of the whole Preston project.
“It’s the biggest tunnel that rainwater from all the other tunnels will flow into, before the water is pumped to Clifton Marsh wastewater treatment works.”
The new sewer system aims to help clean up the River Ribble and beaches along the Lancashire coastline, from Southport to Blackpool.
Mr Sanders said: “The sewer system in Preston is a combination of surface water and foul water.
“That means the water from household kitchens and bathrooms goes down the same sewer as that from the run off from the roofs and roadways.”
The firm said the city’s sewers were built in Victorian times and it was not practical to make them big enough to cope with the heaviest rainfall events.
The network of pipes were built with overflows into water courses and as a consequence the River Ribble isn’t as clean as it ought to be.
Mr Sanders said: “We have paid out nearly £1m in loss of profit payments during this project to businesses so we have been very sympathetic to the city’s business community and thankful to them for their on-going patience.”
The £114m project began two years ago.
Engineers constructed 13 large diameter underground structures, placing 10,000m3 concrete piles and laying around 7,000m of pipes.
A team of around 200 engineers have been working around the clock to deliver the scheme, often working 100ft below the streets of the city.
Shafts were dug at Watery Lane, Marsh Lane and Fishergate Hill to allow digging machines to travel 26m underground to create a network of tunnels between the sites.
The scheme has been designed to reduce the amount of waste water entering the Ribble and comply with European water quality legislation.