Work to remove debris from about 20 piers on the twin bridges on State Highway 82 between Kurow and Hakataramea will take place today, the New Zealand Transport Agency has confirmed.
Agency area manager Colin Hey said that, depending on progress made, the work could continue into tomorrow.
While the work was done, the 129-year-old wooden bridges would be closed for short periods, but open for five minutes on the hour and half hour.
They would also reopen if needed for emergency vehicles.
Works is due to start at 8.30am.
"The work is a continuation of efforts that started last Saturday to shift debris from the piers of the bridges," he said.
A logging machine with a specially extended grab arm will be used to reach over the sides of the bridges to shift branches and small trees stuck in the piers by flooding in January and last month.
A team of abseiling tree fellers would work over the sides of the bridges to help free trapped debris.
Mr Hey said every effort would be made to remove the remaining debris today and reduce the pressure on the bridge piers.
"Heavy rain is predicted over the next few days in the headwaters of the Waitaki River and is likely to increase river flows, so there may be only a limited window of opportunity to get this job finished," he said.
The agency was aware of the impact on the local community caused by last month's extended closure of the bridges and asked for patience, so remaining debris could be shifted.
