Residents in a number of the ACT's fastest-growing suburbs have taken to social media to express their frustration around the lengthy closure of the crossing, which has been blocked for 10 days after heavy rain washed trees and other debris onto the bridge.

Locals says water levels have fallen below the causeway after the weekend's rainfall, despite claims made by the transport directorate to the contrary.

Around 6000 vehicles a day normally use the low-level crossing, which connects Denman Prospect and the growing Molonglo Valley with William Hovell Drive, the new suburb of Whitlam, and Canberra's northern suburbs.

The crossing is also a vital link for police and emergency services. Police officers patrolling out of the Belconnen police station are responsible for responding to incidents in the Molonglo Valley and use the crossing as the most direct route, although resources can be directed from other districts.

The project to replace Coppins Crossing with the as-yet-unnamed Molonglo River Bridge, an extension of the Sir John Gorton Drive dual carriageway through the valley, is not due for completion until 2025.

Joint ACT and federal funding of $175 million has been earmarked for the project, with the tender closing two months ago. Work is expected to start next year.

The bridge project has to support vehicles and active travel (on-road cycle lanes and off-road shared paths) and a future light rail route. There are also plans for a future pedestrian underpass.

Jeremy Smith from Transport and City Services' infrastructure and transport delivery told ABC radio that controlled releases of water from Scrivener Dam had been responsible for washing debris down the river and snagging on the crossing.

The directorate said it was looking to engage a contractor to do the clean-up work but claimed it cannot do so while there was still water coming down the river and over the crossing.

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"We do have to wait for that water level to reduce a bit before we can get in there and make that clean-up happen," he said.

The contractor will need to remove the debris and then inspections will be required to ensure there has been no effect on the structural integrity of the bridge. Some of the barriers on either side of the bridge have been damaged by debris and will need to be repaired.

"We recognise the community's frustration," he said.

The planning process for the new bridge has been protracted, and outpaced by residential development on either side of it.

Coppin's Crossing is named after the Coppin family. John Coppin was a shepherd at the Goat Station, an outstation of the Ginninderra holding on the lower Molonglo River, between 1859 and 1891. Records show the Coppin family was flooded in on several occasions.

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