The New Zealand Transport Agency announced yesterday the first of five 12m sections, which would form the portal on State Highway 94, were set to be moved into position today, weather permitting.
Each section of the temporary extension will be assembled in a car park area 100m downhill from the western tunnel entrance. The extension should be completed by mid-February.
The agency's Southland area manager, Peter Robinson, said yesterday some 5pm closures of the Milford road, from the Hollyford turn-off, would be necessary to do the job with the minimum of disruption to road users.
''We will give road users and tour operators as much advance notice of these as possible,'' Mr Robinson said.
''Since mid-December, the road has been closed daily from 7pm to 7.30am because of rock-fall risk in the area.''
The extension is intended to deflect scatter rock above the western tunnel entrance away from the highway. Mr Robinson said work on fabricating the $1 million to $1.5 million portal began just after Christmas.
''There isn't a quick permanent fix to the current rock-fall risk at the western entrance to the tunnel and it is likely to take time to find one,'' he said.
''Until then, we have to look at ways to safely extend the opening hours of this important tourist route while the rock-fall risk remains.
''This portal extension provides that as well as giving us an opportunity to work on the rocks above the entrance without putting road users at risk.''
The flexible modular design of the portal meant it could be removed and erected again at the location, or used elsewhere on the Milford road, Mr Robinson said.
