WALLACE - A failing joint on the viaduct is causing a speed limit reduction on Interstate 90.

Effective immediately, the speed limit for eastbound lanes between mileposts 60.9 and 61.5 is 55 miles per hour. The Idaho Transportation Department said it's for safety reasons.

"We're going to do a temporary repair until we can get in there and do a permanent repair," said Barbara Babic of the ITD communications office.

That will include the installation of a big metal plate that's bolted into place across the failing joint, which will create a 1-inch bump across the road.

Westbound lanes will not be affected.

The speed limit reduction could take as long as one year.

"This will probably be a long-term reduction until that permanent repair can be done," Babic said.

Babic said the problem isn't from megaloads, which have been traveling through the area for several months. Rather, it's the age of the viaduct, which was built about 20 years ago.

Costs of the temporary and permanent repairs were not available.