MORE THAN 8000 metres of Glasgow's Subway network are being cleaned up as part of a £300m upgrade.

Around 100 workers will be involved in the huge clean-up operation, which is expected to take up to two years.

They will be underground during the night time closures to minimise disruption to passengers.

Engineers from Freyssinet Ltd have begun work on the mammoth £17m project, which sees the Subway getting its first full-scale upgrade in more than 30 years.

The 119-year-old system is the third oldest in the world behind London and Budapest.

Work is being carried in tunnels running between Hillhead and Buchanan Street, with a stretch that covers Kelvinbridge, St George's Ceross and Cowcaddens.

Engineers will also work in a section of tunnels on the east side of Glasgow from Shields Road to Kinning Park.

Work will involve cleaning the tunnel lining, track bed and drainage channel over 8019 metres.

They will also repair grouting, do concrete and brickwork lining repairs and inject resin to seal against leaks.

Another 6672 metres of line will be cleaned and engineers will investigate its condition to prioritise any subsequent work that needs to take place.

Around 100 workers will be involved in the operation, which is taking place overnight and expected to take around two years.

A spokesman said: "The labour force will average at 80 people but, at the peak in operations, we expect to bring 130 people into the tunnels."

Strathclyde Partnership for Transport (SPT) awarded the £17m contract to the specialist civil engineering company earlier this year.

The work is part of an overall £300m modernisation programme, which will eventually result in driver-less trains.

Bosses at Strathclyde Partnership for Transport say the work is needed to keep the underground running.

It would have to go ahead even without the ongoing £288m modernisation of the system.

Insiders at the transport body say it is hoped the relining can be carried out without any disruption to passengers but have been unable to give any guarantees.