State Highway 94 into Milford Sound had been closed since last Thursday with avalanche risk too high for safe travel.
There had been several avalanches, triggered by warm rain, and crews could not safely clear the road.
Waka Kotahi Milford Road Alliance manager Kevin Thompson said there was a small window on Monday evening in which to carry out the control work.
This was pre-emptive work managed by the Milford Road Alliance to set off avalanches when there was no traffic on the highway and clear the road once it was safe to do so.
The forecast bad weather turned to the south, which also helped reduce avalanche risk.
The road reopened yesterday but drivers were advised to drive with care. Avalanche hazard was low and another update would be given this morning.
The Milford Rd may be open but the Hollyford Rd will not be for weeks.
Some side creeks have flooded extensively and blocked bridges. Some creeks have then scoured out the road.
NZTA expects it will take several weeks to repair and provide good access. Inspections were under way and machinery would be delivered, starting today.
