Motorists driving south this weekend will have to take detours around the Skagit River Bridge as workers install a permanent fix for the structure.

The new span will have no overhead supports and will look nothing like the old bridge, which tumbled into the river in May after the top of a large crate being hauled by an Albertan trucker struck a beam, collapsing one span of the bridge into the river.  

Travis Phelps, spokesman for the Washington State Department of Transportation, says the switch is expected to take 12 hours, but may take longer.

The bridge, located along Interstate 5 about 130 kilometres south of Vancouver, will be shut down at 7 p.m. PT Saturday and is expected to reopen at 7 a.m. Sunday.

Officials say the bridge will be partially closed 36 times until mid-November.