CONTRACTORS IN Derby were this week racing to complete emergency repairs to a culvert beneath one of the city's main shopping streets.
The road has been closed to traffic since June, when routine inspection revealed that a 210m culvert and an underground bridge connected to it were close to collapse.
The street is due to reopen next month, ahead of the Christmas shopping season.
'We carried out an inspection on 18 June at 2pm and by 4pm we had closed the road, ' said Derby Council head of engineering design Dennis O'Neill.
The inspection revealed that joints in the culvert and bridge had opened up and some sandstone bridge blocks were missing. Utility companies had also weakened the bridge by drilling holes through the arch for cable ducts.
The 19th century brick culvert is incorporated within an 18th century sandstone bridge.
The culvert is being relined and the bridge strengthened as part of the £530,000 project.
McNicholas is relining the culvert roof and walls with up to 600mm of C40 steel fibre reinforced concrete. Fibres make up 40kg/m 3of the mix and are added on site. Concrete is pumped under pressure from street level.
The contractor is using 2m long by 1m wide steel plate shutters, which are fitted together underground after being lifted through 900mm by 600mm manholes along Albert Street.
This enables work to be carried out without opening up the street and means the job can be completed in two months - less than half the time needed if the road were dug up. Engineers are now repairing the last 60m of culvert.