Scottish Water is shortly expected to announce a joint venture of Costain and Vinci as preferred bidder to design and build a 3-mile long sewer tunnel in Glasgow.

The contract award will be a momentous deal for the new pairing, which is also bidding alongside Bachy for the three major tunnelling packages on the vast £2.3bn Thames Tideway project in London.

Costain and Vinci first bid together for tunnelling work on London Underground’s £500m Bank Station upgrade but lost out at the last to Dragados.

The 4.5m diameter Shieldhall tunnel in Glasgow will be driven at depths of between 10m to 30m and will run through an area of old mine workings raising potential technical problems.

The old workings will be grout filled before tunnelling can start.

The Costain/Vinci team will excavate six shafts for the tunnel drive which is expected to advance at 10m a day.

They will then need to connect the tunnel at both ends to the existing sewer network.

The waste water tunnel in the south of Glasgow forms part of the biggest upgrade of the city’s waste water network in more than a century and will run between Queen’s Park and Craigton Industrial Estate via Pollok Park and Bellahouston Park.

Geoff Aitkenhead, Scottish Water’s Asset Management Director, said: ”The Shieldhall tunnel will resolve large-scale water quality problems in the River Clyde and its tributaries, provide aesthetic screening to overflows into watercourses such as tributaries of the Clyde and White Cart Water and reduce the risk of flooding.”