Bridge Will Slide West Time Zone Bridge Will Be Replaced With Wider Span

An unusual construction project under way here will relieve a bottleneck in Idaho’s north-south highway.

The Goff Bridge - commonly known as the Time Zone Bridge - will be replaced with a wider, higher and safer span across the Salmon River on U.S. Highway 95.

The target date for completion is December 1998. But there’s another red-letter month on the construction schedule: April 1997.

That’s when the existing 1935 bridge will be slid on rails into a new position 65 feet to the west so it can serve as a detour route.

“I feel pretty confident it will not fall in the river,” project manager David Kuisti said of the tricky maneuver.

With no other detour route and little room to work in the canyon, Kuisti said, engineers were left with no choice but moving the old bridge.

“We can’t leave it where it is and build around it.”

The contractor, Harcon Inc. of Spokane, will have 48 hours to move the bridge (72 hours, if it’s done on a weekend).

Time will be critical because U.S. 95 - the main transportation artery down the state’s spine - will be closed to traffic through Riggins during the move. That means a big detour through Oregon and Washington.

“We’ll have signs from Boise to Lewiston, alerting people to the closure,” said Kuisti.

The new bridge, like the existing one, will cross the river in a single span. But two steel posts, 4.5 feet in diameter, are needed to hold up the detour bridge. The posts will hit the riverbed 68 feet below the bridge deck and extend 41 feet into the earth.

Such in-river work can be done only between Nov. 15 and March 15 to avoid harming migrating steelhead.

Besides protecting fish and water quality, the bridge-builders must consider their impact on recreation.

Riggins is home to 12 river outfitters. The bridge itself, which is next to the Time Zone Rapids, constantly is used by people driving to and from a popular rafting takeout point at Lucile.

Travelers passing south over the bridge go from Pacific to Mountain time - hence, the name.

Right now, two large trucks can’t pass on the shoulderless bridge. The height restriction is 14 feet, 5 inches; it will be 22 feet, 5 inches on the new bridge.

The new bridge will be longer and will have a straighter approach.

The new bridge will cost $12.4 million. One reason it became a high-priority project is that a slow landslide is pushing at the south end of the bridge. Going underneath the bridge, Kuisti pointed to bolts that have been moved as far as possible to compensate for the changing landscape.

The new bridge abutments will be wide enough that the moving earth won’t be a problem, Kuisti said.

, DataTimes