There are likely to be months of delays on Derby's roads during a £2.5m scheme to upgrade the city's sewers.
Severn Trent said the 6km (3.7 miles) of sewers in the city are showing severe signs of wear and tear.
The company said it will try to keep problems to a minimum during the anticipated six months of repairs.
Work on the 150-year-old system is already under way on Normanton Road, and will continue near the Derbyshire Royal Infirmary on London Road.
The work should be finished by March next year.