The work, which is necessary to meet Health and Safety Executive demands, has been planned jointly with the Cheshire County and Chester City councils, emergency services and public transport operators.
Starting on August 11, 2008, one-third of a mile of metallic main will be renewed from Mill Street, Handbridge, over the Old Dee Bridge along Lower Bridge Street to its junction with Pepper Street and Bridge Street.
The scheduled ancient monument will be closed until September 1, 2008, but will remain open to pedestrians and cyclists, according to National Grid.
Craig Horrocks, National Grid contract manager, said: The work has to be timed for the summer months when demand for gas is low. Engineers can then isolate sections of the main and insert the new plastic pipe, avoiding the need for open excavations and turning off supplies.
