Work to repair the south side of Fen Bridge near Crowland begins on Tuesday with daytime closures Monday-Friday through to mid-October.
Some improvements were made to the bridge on the B1166 Gravel Causeway earlier this year but the current scheme could not be tackled then because of an issue with the water mains.
County highways say the water mains will now be temporarily diverted by Anglian Water, meaning the team can return to finish the job.
Due to the narrow width of the bridge, the road will need to be closed during the daytime.
The bridge will be open in the evenings and at weekends, although temporary traffic lights will be in place during these times.
The improvements are expected to be completed by Friday, October 13, weather-permitting.
Andrew Antcliff, the council’s senior bridge engineer, said: “We’re now ready to divert the present mains over the bridge and complete the repairs, starting after the bank holiday.
“We apologise for any inconvenience caused, and would like to thank people for their ongoing patience.
“There may be times when we are able to reopen the road during the day, and we will do so whenever possible. However, we would still recommend motorists use alternative routes where they can.”
During the closures, traffic will be diverted via the B1166, B1040, A16, B1443, A15, B1524, B1166 and vice-versa.
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