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A specialist rescue team is on standby as part of the £20m project to renovate sewers in Ramsgate.
Southern Water is running regular practice exercises for the team who will be trained to rescue injured colleagues from deep tunnel networks.
The unique sewers were built by the Victorians over a century ago when miners dug underground tunnels through the chalk, up to 10m deep in places.
Project manager Norman Howell said: "Our specialist underground teams are working in a cramped and hostile environment and their safety is our top priority.
"It's imperative that we have the necessary experienced personnel and equipment on site so these workers can be evacuated safely if there's an accident or emergency."
The rescue scenario involved a worker with a head injury 10m below ground and 7m along from the entrance.
Rescuers were lowered to administer first aid and prepare the casualty to be winched back to the surface.
Mr Howell added: "On hearing the alarm, our mines rescue team quickly recovered the 'injured' worker, demonstrating a controlled and efficient approach which is the hallmark of seasoned professionals.
"This is one of several practice rescues we have carried out to ensure our team is ready for any eventuality.”
As part of the project the team has lined more than 12km of the sewer, 6km of the chalk tunnels and built more than 2km of pipeline.
Southern Water started the project in July 2014 and is also improving 98 manhole shafts and building 15 new manholes.