"This is fantastic news for the coast and it's great to be able to restore a link that's so important to the communities much earlier than we had planned,'' said West Coast area manager Mark Pinner.
"Our contractors have worked bloody well to reconstruct the washed out section of the highway.''
Contractors, many from Greymouth, have been working 15 hour days to reopen the vital tourist and truck route.
Mr Pinner said the cost of the work was more than $1 million.
The repairs are temporary, and drivers would need to use the section of highway with care, although there are no size or weight restrictions on vehicles.
Contractors had to divert the river's floodwaters away from the washout on the northern approach to the bridge before they could start rebuilding the highway.
The process of restoring the road involved building up layers of stone and gravel to get to the level of the bridge. About 100,000 cubic metres of gravel and stone had been used, in addition to 6000 tonnes of rock, and Mr Pinner estimated more would be needed.
Work on the abutment was completed yesterday, although Mr Pinner said it had been a slow process as they needed to be careful while doing it.
He said the NZTA would look at rebuilding the bridge, while more rocks would be placed upstream to try to keep the river within its channel in future.
Mr Pinner said the closure had been frustrating for locals, and the early opening was the best way to say thanks for their support and patience.
