A section of the Alaska Highway south of Beaver Creek will be closed Sunday night for a scheduled four hours to make repairs to the Koidern River Bridge.

Robin Walsh is the director of transportation engineering for the Yukon government. He said this morning melting permafrost has moved the abutment at the north end of the bridge and shifted the structure sideways about five centimetres.

The steel bridge girders sit on bearings which are 15 centimetres wide, he explained.

He said if the girders were to ever slide off the bearings, the bridge deck would fall about 15 centimetres to the bridge abutment.

'That would not be good,' he quipped. 'So we are moving it back in place.'

The Koidern River Bridge, situated some 50 kilometres south of Beaver Creek, was replaced in 1970, with upgrading work completed in 1990.

Walsh said it is not scheduled to be replaced as part of the U.S.-funded Shakwak project, because it is relatively new.

But the $200,000 being spent this year is necessary to stabilize the structure, he explained.

Walsh said there are also plans to insert cooling devices in the north-end abutment to withdraw as much heat from the ground as possible with hopes of keeping the permafrost stable through the summer months.

Klondike Welding of Whitehorse has been on site for about a week preparing to winch the bridge back in place, under the guidance of a Vancouver firm which specializes in this type of work.

The closure, he said, is scheduled between 9 p.m. Sunday and 1 a.m. Monday.

'Traffic will be minimal at that point in time and we are hoping to let people know, so they plan their trips not to be there then.'

This year's budget for the Shakwak project is $29.5 million, including the $200,000 for the Koidern River Bridge and $6.25 million to complete the $35-million replacement of the Donjek River Bridge.

The new Donjek bridge opened to traffic Wednesday. Work to replace it began last year.

Walsh said a tender call to remove the old bridge will go out later this year, with an aim to begin the work this winter. Removal is expected to cost somewhere between $2 million and $3 million, he said.

Once the second-longest bridge in the Yukon at 490 metres, second only to the Teslin's Nisutlin River Bridge at 583 metres, the redesigned Donjek has now shrunk to 270 metres, and has moved to third-longest, behind the Nisutlin and the Teslin River Bridge at Johnson's Crossing.

The Slim's River Bridge is scheduled to be replaced in 2008 as part of the Shakwak work, and the Duke River Bridge is scheduled for replacement in 2009.