CHARLESTOWN — On Monday, the New Hampshire Department of Transportation will begin rehabilitation of the Route 12 bridge over the railroad tracks just south of downtown.

The project will require one-lane alternating traffic over the bridge both day and night. Temporary traffic signals will be implemented for motorists and new traffic patterns will be established.

The DOT is also closing access to South Main Street from Route 12 for the duration of the project, which has an anticipated completion date of Aug. 1, 2025. Motorists will have to detour onto Paris Avenue and then East Street and past the Charlestown Primary School to South Main Street.

The work will include removing the pavement and repairing the concrete deck. Miller Construction, of Windsor, is the contractor on the $920,000 project.